Interference monitoring device, optical adjustment procedure and optical adjustment program

Abstract

In an interference observation device, an input unit receives a first input representing the thicknesses, refractive indices, and arrangement order of a plurality of layers present in an object under observation. A display unit shows a first element representing the thickness and refractive index values ​​of the plurality of layers according to the first input, and a second element graphically representing the plurality of layers in a mode corresponding to the thicknesses and arrangement order of the plurality of layers according to the first input. In a state where the display unit shows the first and second elements, the input unit receives a second input to specify an observation surface from the interfaces between the plurality of layers.The processing unit performs a first optical adjustment process to set a relative position between the objective lens and the observation object, and a second optical adjustment process to set an optical path length by moving a reference mirror based on the thicknesses and refractive indices of the multitude of layers according to the first input, so that an interference image of the observation surface is captured according to the second input.

Description

TECHNICAL AREA

[0001] One aspect of the present disclosure relates to an interference monitoring device, an optical adjustment procedure for the interference monitoring device, and an optical adjustment program. STATE OF THE ART

[0002] For example, patent literature 1 describes an interference observation device comprising: a light source; an interference-optical system that splits the light emitted by the light source into a first branched light and a second branched light, which reflects the first branched light from an observation object and combines the first branched light and the second branched light (reference light) and emits the combined light; a light receiving unit that receives the combined light and outputs a detection signal; and an image acquisition unit that obtains an interference image based on the detection signal. CITATION LIST PATENT LITERATURE

[0003] Patent Literature 1: PCT International Publication No. WO2016-121250 PRESENTATION OF THE INVENTIONAL PROBLEM

[0004] The interference observation setup described above is used for surface observation to view a surface of the object under observation. However, internal observation can also be considered to view the interior of the object through interference. For example, if the object under observation is a device with a cap element, a surface of the device (the interface between the device and the cap element) can be viewed through the cap element using light with a wavelength that passes through the cap element. Such internal observation requires optical adjustments, such as adjusting the focus position of an objective lens or the optical path length of the reference light.

[0005] One objective of the present disclosure is therefore to provide an interference observation device, an optical adjustment procedure and an optical adjustment program that are capable of performing the optical adjustment appropriately for internal observation. SOLUTION TO THE TASK

[0006] An interference observation device according to one aspect of the present disclosure is [1] “an interference observation device for observing the interior of an object of observation having a plurality of layers, wherein the interference observation device comprises: a light source emitting light; an interference-optical system comprising a movable reference mirror and an objective lens that splits the light emitted by the light source into a first light and a second light and emits the interference light of the first light, which is reflected from an observation surface arranged inside the object of observation, and of the second light, which is reflected from the reference mirror; an image sensor that detects the interference light; an input unit that receives an information input; a display unit that displays information; and a processing unit,which acquires an interference pattern based on a captured interference light result and performs an optical adjustment process for optical alignment with respect to an observation of the observed object. The input unit receives an initial input representing the thicknesses, refractive indices, and arrangement order of the multiple layers. The display unit shows a first element representing the thickness and refractive indices of the multiple layers according to the initial input, and a second element graphically representing the multiple layers in a mode corresponding to the thicknesses and arrangement order of the multiple layers according to the initial input. In a state where the display unit shows both the first and second elements,The input unit receives a second input to specify the observation surface from the interfaces between the multitude of layers. The processing unit performs a first optical adjustment process to set a relative position between the objective lens and the observation object, and a second optical adjustment process to set an optical path length of the second light by moving the reference mirror based on the thicknesses and refractive indices of the multitude of layers according to the first input, so that the interference pattern of the observation surface is captured according to the second input.

[0007] In the interference observation device, the first optical adjustment process sets the relative position between the objective lens and the observation object. The second optical adjustment process sets the optical path length of the second light by moving the reference mirror, based on the thicknesses and refractive indices of the multiple layers corresponding to the first input. This results in the acquisition of the interference pattern of the observation surface corresponding to the second input. Accordingly, the relative position between the objective lens and the observation object, as well as the optical path length of the second light, can be adjusted based on the thicknesses and refractive indices of the multiple layers of the observation object, thus obtaining the interference pattern of the observation surface.Furthermore, in the interference observation device, the first element, representing the thickness and refractive index values ​​of the multiple layers according to the first input, and the second element, graphically representing the multiple layers in a mode corresponding to their thickness and stacking order according to the first input, are displayed on the display unit. When the display unit shows both the first and second elements simultaneously, the observation surface is defined by the interfaces between the multiple layers. This simplifies the process of defining the observation surface from the interfaces between the multiple layers. Therefore, the interference observation device allows for suitable optical adjustment for internal observation.

[0008] An interference monitoring device according to one aspect of the present disclosure may be [2] “the interference monitoring device according to [1], in which the display unit displays the interference pattern captured by the processing unit in addition to the first element and the second element.” In this case, observation may be facilitated.

[0009] An interference monitoring device according to one aspect of the present disclosure may be [3] “the interference monitoring device according to [1] or [2], wherein the display unit together with the second element displays an element indicating the interface designated as the observation surface among the interfaces of the plurality of layers graphically represented as the second element.” In this case, the interface designated as the observation surface can be easily detected.

[0010] An interference monitoring device according to one aspect of the present disclosure may be [4] “the interference monitoring device according to one of [1] to [3], wherein the display unit together with the second element displays an element for indicating a position of the objective lens at a position spaced apart from the plurality of layers graphically represented as the second element by a distance corresponding to the relative position between the objective lens and the object being observed.” In this case, the relative position between the objective lens and the object being observed can be easily ascertained.

[0011] An interference monitoring device according to one aspect of the present disclosure may be [5] “the interference monitoring device according to one of [1] to [4], wherein the second input is received from a user who specifies a region within the first element or the second element.” In this case, the specification of the observation surface among the interfaces between the plurality of layers can be further improved.

[0012] An interference monitoring device according to one aspect of the present disclosure may be [6] “the interference monitoring device according to any of points [1] to [5], wherein the processing unit performs an additional adjustment process after the first optical adjustment process and the second optical adjustment process, and in the additional adjustment process the processing unit acquires a plurality of interference images in which an optical path length difference between the first light and the second light is made different by changing the optical path length of the second light, and performs the first optical adjustment process and the second optical adjustment process based on the plurality of interference images.” In this case, the relative position between the objective lens and the observation object and the optical path length of the second light can be adjusted with higher accuracy.

[0013] An interference observation device according to one aspect of the present disclosure may be [7] “the interference observation device according to [6], which further comprises a table for arranging the object of observation, wherein the table is movable at least along a plane that intersects a direction in which the first light is incident on the object of observation. The processing unit performs the additional adjustment process in response to a movement of the table along the plane.” In this case, the observation position can be changed by moving the object of observation, while the relative position between the objective lens and the object of observation and the optical path length of the second light are adjusted with higher accuracy.

[0014] An interference monitoring device according to one aspect of the present disclosure can be [8] “the interference monitoring device according to [7], wherein the input unit receives a third input to specify whether the additional adjustment process should be performed in response to the movement of the table along the plane. The display unit shows an element representing an adjustment state, whether the additional adjustment process should be performed in response to the movement of the table along the plane, based on the third input.” In this case, it can be specified whether the additional adjustment process should be performed in response to the movement of the table, and the adjustment state, whether the additional adjustment process should be performed, can be detected, and consequently, the facilitation can be improved.

[0015] An interference monitoring device according to one aspect of the present disclosure may be [9] “the interference monitoring device according to one of [6] to [8] wherein the input unit receives a fourth input to specify a limit value relating to the additional tuning process, and the display unit displays an element representing the limit value according to the fourth input.” In this case, the limit value can be specified with respect to the additional tuning process, and the limit value can be detected, and consequently, the facilitation can be improved.

[0016] An interference monitoring device according to one aspect of the present disclosure may be

[10] “the interference monitoring device according to one of [6] to [9], wherein the display unit displays an element representing a relative distance between the objective lens and the object being observed and an amount of the optical path length of the second light that is set in the additional adjustment process.” In this case, the result of the additional adjustment process can be recorded, and the facilitation can be improved.

[0017] An optical adjustment method according to one aspect of the present disclosure is

[11] “an optical adjustment method for carrying out an optical adjustment with respect to an observation of an observation object, which has a plurality of layers in an interference observation device, comprising a light source emitting light, an interference optical system comprising a movable reference mirror and an objective lens that splits the light emitted by the light source into a first light and a second light, and emits the interference light of the first light, which is reflected from an observation surface located within the observation object, and of the second light, which is reflected from the reference mirror, an image sensor that detects the interference light, an input unit that receives an information input, and a display unit that displays the information,and which acquires an interference image based on a capture result of the interference light, the method comprising in sequence: a step in which the input unit is caused to receive a first input representing thicknesses, refractive indices, and the arrangement order of the plurality of layers; a step in which the display unit is caused to display a first element representing values ​​of the thicknesses and refractive indices of the plurality of layers according to the first input, and a second element graphically representing the plurality of layers in a mode corresponding to the thicknesses and arrangement order of the plurality of layers according to the first input; a step in which the input unit is caused to receive a second input to specify the observation surface from the interfaces between the plurality of layers in a state,in which the display unit displays the first element and the second element; and a step in which a first optical adjustment process is carried out to set a relative position between the objective lens and the observation object, and a second optical adjustment process is carried out to set an optical path length of the second light by moving the reference mirror based on the thicknesses and refractive indices of the multitude of layers corresponding to the first input, so that the interference pattern of the observation surface corresponding to the second input is captured.” According to the optical adjustment procedure, the optical adjustment for internal observation can be carried out appropriately for the reasons described above.

[0018] An optical adjustment program according to one aspect of the present disclosure is

[12] “an optical adjustment program for performing an optical adjustment with respect to an observation of an observation object, which has a plurality of layers in an interference observation device, comprising a light source emitting light, an interference optical system comprising a movable reference mirror and an objective lens that splits the light emitted by the light source into a first light and a second light, and emits the interference light of the first light, which is reflected from an observation surface located within the observation object, and of the second light, which is reflected from the reference mirror, an image sensor that detects the interference light, an input unit that receives an information input, and a display unit that displays the information,and which captures an interference pattern based on a capture result of the interference light, wherein the program causes a computer in the interference observation apparatus to perform the following in sequence: a process in which the input unit is caused to receive a first input representing thicknesses, refractive indices, and the arrangement order of the plurality of layers; a process in which the display unit is caused to display a first element representing values ​​of the thicknesses and refractive indices of the plurality of layers according to the first input, and a second element graphically representing the plurality of layers in a mode corresponding to the thicknesses and arrangement order of the plurality of layers according to the first input; a process in which the input unit is caused to receive a second input,to specify the observation surface from the interfaces between the multitude of layers in a state where the display unit shows the first element and the second element; and a process in which a first optical adjustment process is performed to set a relative position between the objective lens and the observation object, and a second optical adjustment process is performed to set an optical path length of the second light by moving the reference mirror based on the thicknesses and refractive indices of the multitude of layers corresponding to the first input, such that the interference pattern of the observation surface corresponding to the second input is captured.” According to the optical adjustment program, the optical adjustment for internal observation can be performed appropriately for the reasons described above. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0019] According to one aspect of the present disclosure, it is possible to provide the interference observation device, the optical adjustment procedure and the optical adjustment program which are suitable for carrying out an optical adjustment appropriately for internal observation. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] Fig. Figure 1 shows a view of the design of an interference monitoring device of one embodiment. [ Fig. 2] Fig. 2 is a view describing internal observation. [ Fig. 3] Fig. Figure 3 is a view describing a relationship between the amount of movement of an objective lens and the amount of change in the optical path length of a second light. [ Fig. 4] Fig. 4 is a view used to describe a setting when an observed object has a large number of layers. [ Fig. 5] Fig. Figure 5 is a flowchart describing a process that is carried out in the interference observation facility. [ Fig. 6] Fig. Figure 6 is a view describing the operation of the interference monitoring facility. [ Fig. 7] Fig. Figure 7 is a view showing examples of captured interference patterns. [ Fig. 8] Fig. Figure 8 is a view showing examples of a real part image, an imaginary part image, an amplitude image, and a phase image. [ Fig. 9] Fig. Figure 9 is a flowchart describing a process for calculating a rating based on a captured interference pattern. [ Fig. 10] Fig. Figure 10 is a flowchart describing the focus setting process. [ Fig. 11] Fig. 11 is a view describing the focus setting. [ Fig. 12] Fig. 12 is a view describing the focus setting. [ Fig. 13] Fig. 13 is a view describing the focus lock. [ Fig. 14] Fig. Figure 14 is a view describing the focus lock. [ Fig. 15] (a) and (b) in Fig. 15 are views describing another example of the operation of the interference monitoring facility. [ Fig. 16] Fig. Figure 16 is a flowchart to describe another example of a process carried out in the interference observation facility. [ Fig. 17] Fig. Figure 17 is a flowchart to describe another example of a process carried out in the interference observation facility. [ Fig. 18] Fig. Figure 18 is a flowchart to describe another example of a process carried out in the interference observation facility. [ Fig. 19] Fig. 19 is a table describing methods for capturing an interference pattern. [ Fig. 20] Fig. Figure 20 is a view describing another example of the operation of the interference monitoring facility. [ Fig. 21] Fig. 21 is a table describing another example of optical adjustment. [ Fig. 22] Fig. Figure 22 shows a view of the design of another example of an interference monitoring device. [ Fig. 23] (a) to (c) in Fig. 23 are views describing the relationship between the magnitude of focus movement and the magnitude of the change in optical path length in the Fig. 22 shown interference monitoring device. [ Fig. 24] Fig. Figure 24 is a view describing a method for calculating a valuation value based on a curvature amount in a phase image. [ Fig. 25] Fig. Figure 25 is a view describing an application example for an optical adjustment process. [ Fig. 26] Fig. Figure 26 is a view describing surface observation. [ Fig. 27] Fig. Figure 27 is a view describing another example of the operation of the interference monitoring facility. [ Fig. 28] Fig. Figure 28 is a view describing another example of the operation of the interference monitoring facility. [ Fig. 29] Fig. Figure 29 is a view describing the optical setting when the objective lens is replaced. [ Fig. 30] Fig. Figure 30 is a flowchart to describe an example of a process when the objective lens is replaced. [ Fig. 31] Fig. Figure 31 is a view showing an example where an adapter is attached to the lens. [ Fig. 32] Fig. Figure 32 is a view describing the setting of the mechanical difference of a lens. [ Fig. 33] Fig. 33 is a view that shows an example of a display in a display unit. [ Fig. 34] Fig. Figure 34 is a flowchart describing an operational example of the interference monitoring facility. [ Fig. 35] Fig. Figure 35 is a view of the design of an optical adjustment program. [ Fig. 36] (a) and (b) in Fig. 36 are views describing the focus lock. [ Fig. 37] Fig. 37 is a view that shows another example of a display in the display unit. [ Fig. 38] Fig. Figure 38 is a view showing an interference observation setup of a modification example. [ Fig. 39] Fig. Figure 39 is a view that shows a display example in the case of the modification example. DESCRIPTION OF EXECUTION FORMS

[0020] An embodiment of the present disclosure is described in detail below with reference to the drawings. In the following description, the same reference numerals are used for the same or corresponding elements, and duplicate descriptions are omitted. [Interference monitoring facility]

[0021] As in the Fig. 1 and Fig. As shown in Figure 2, an interference observation device 1 comprises a light source 2, an interference optical system 3, an image sensor 4, a processing unit 5, and a stage S. The interference observation device 1 is an interference microscope for observing an observation object 8 arranged on the stage S by means of light interference. The observation object 8 is, for example, a semiconductor device, but it can also be other industrial samples made of metal, glass, resin, liquid crystal, a polymer compound, or the like. The observation object 8 can be a biological sample such as a cell or cell mass. In the following description, an X-direction, a Y-direction perpendicular to the X-direction, and a Z-direction perpendicular to both the X-direction and the Y-direction are defined, as shown in Figure 2. Fig. 1 and Fig. 2 shown.

[0022] The interference observation device 1 is designed to allow internal observation of the interior of the observation object 8 in addition to surface observation of a surface (outer surface) of the observation object 8. As in Fig. 1 and Fig. As shown in Figure 2, the internal observation involves an observation surface R located inside the observation object 8. In this example, the observation object 8 is a semiconductor device with a cap section and has a first layer 81, a second layer 82, and a third layer 83.

[0023] The first layer 81 is a resin layer (cap section), the second layer 82 is an air layer, and the third layer 83 is a semiconductor layer (fuse layer). The first layer 81 through the third layer 83 are arranged (stacked) in the order of the third layer 83, the second layer 82, and the first layer 81, and the object under observation 8 is positioned on the stage S such that the third layer 83 is in contact with the stage S. The observation surface R is located at one of the interfaces between the first layer 81, the second layer 82, and the third layer 83. For example, the observation surface R in the example of Fig. 1 arranged at the interface between the second layer 82 and the third layer 83, and in the example of Fig. The observation surface R is located at the interface between the first layer 81 and the second layer 82. The observation surface R can be observed through the first layer 81 by using light with a wavelength that passes through the first layer 81, such as light emitted by the light source 2, which will be described later.

[0024] Light source 2 emits incoherent light. Light source 2 is, for example, a lamp-based light source such as a halogen lamp, a light-emitting diode (LED) light source, a superluminescent diode (SLD) light source, an enhanced spontaneous emission (ASE) light source, or similar.

[0025] In this example, the interference optical system 3 (interference observation device 1) is designed as a Linnik interference type. The interference optical system 3 comprises a lens 11, a beam splitter 12, an objective lens 13, a reference objective lens 14, and a reference mirror 15. The interference optical system 3, together with the light source 2, is arranged in a housing H and forms an optical module M. The optical module M is movable along the Z-direction by a predefined actuator 16. The Z-direction is a direction parallel to an optical axis of the objective lens 13 and is parallel to the direction in which a first light L1, which will be described later, is incident on the observation object 8.

[0026] Lens 11 collimates the light emitted by light source 2. Beam splitter 12, for example a prism with an optical surface 12a, splits the light collimated by lens 11 at its optical surface 12a into a first light L1 and a second light L2. Beam splitter 12 directs the first light L1 to objective lens 13 and the second light L2 to reference objective lens 14. Furthermore, the first light L1, reflected from the observation surface R of the observation object 8, passes through objective lens 13 onto optical surface 12a, and the second light L2, reflected from reference mirror 15, passes through reference objective lens 14 onto optical surface 12a. The first light L1 and the second light L2 are combined at optical surface 12a to form interference light L3. The interference optical system 3 emits the interference light L3 to the image sensor 4.

[0027] The objective lens 13 focuses the first light L1 emitted by the beam splitter 12 onto the observation object 8 arranged on the stage S. In addition, the first light L1 reflected from the observation surface R of the observation object 8 falls onto the objective lens 13. The objective lens 13 then directs the incident first light L1 to the beam splitter 12.

[0028] The reference lens 14 directs the second light L2, emitted by the beam splitter 12, to the reference mirror 15 and focuses the second light L2 onto the reference mirror 15. Furthermore, the reference lens 14 emits the second light L2 reflected by the reference mirror 15 to the beam splitter 12. The reference mirror 15 reflects the second light L2 emitted by the reference lens 14 back to the reference lens 14.

[0029] Furthermore, the housing H of the optical module M contains a stepper motor 17 for moving the reference objective lens 14, as well as a stepper motor 18 and a piezoelectric element 19 for moving the reference mirror 15. The stepper motor 17 moves the reference objective lens 14 along an optical axis (for example, the X-direction) of the second light L2 perpendicular to the Z-direction. The stepper motor 18 and the piezoelectric element 19 move the reference mirror 15 along the optical axis of the second light L2.

[0030] The response time of stepper motors 17 and 18 is greater than 10 ms, while the response time of piezoelectric element 19 is less than 1 ms. This is because the response time of piezoelectric element 19 is shorter than that of stepper motors 17 and 18. The stroke (minimum distance of movement) of stepper motors 17 and 18 is several mm, while the stroke of piezoelectric element 19 is approximately 2 µm. This is because the stroke of piezoelectric element 19 is smaller than that of stepper motors 17 and 18. The number of activations of stepper motors 17 and 18 during their lifetime is less than 1 million, while the number of activations of piezoelectric element 19 during its lifetime is more than 10 billion. The number of activations of the piezo element 19 during its lifetime is greater than the number of activations of the stepper motors 17 and 18 during their lifetime.

[0031] The image sensor 4 is, for example, an image sensor (camera) such as a CCD area image sensor or a CMOS area image sensor. The image sensor 4 detects the interference light L3 emitted by the interference optical system 3 (the beam splitter 12) (captures an image of it). A lens 41 and an objective 42 are arranged between the image sensor 4 and the interference optical system 3. The lens 41 forms an image of the interference light L3 emitted by the interference optical system 3 onto an image-capturing surface of the image sensor 4. The lens 41 is housed within an objective 42. The objective 42 is, for example, cylindrical and is attached to the image sensor 4 in such a way that it surrounds the surface of the image sensor.

[0032] The processing unit 5 is communicatively connected to each part of the interference observation device 1, including the light source 2, the interference optical system 3, the image sensor 4, and the object stage S, and acquires an interference image based on the acquisition result of the interference light L3 in the image sensor 4. Furthermore, the processing unit 5 performs an optical adjustment process for the optical adjustment with respect to the observation of the observation object 8 using the interference observation device 1. The interference image and the process performed by the processing unit 5 are described later. The processing unit 5 consists, for example, of a computer C, which has a processor (CPU) as well as RAM and ROM as storage media. The computer C has a memory area 51.

[0033] Computer C further comprises an input unit 52, which receives information input, and a display unit 53, which displays information. The input unit 52 is, for example, a device that receives user input, such as a mouse or a keyboard. The display unit 53 is, for example, a display that shows an image. The input unit 52 and the display unit 53 can, for example, be configured as a single touch panel. Furthermore, in this example, the processing unit 5, the memory area 51, the input unit 52, and the display unit 53 are configured as a single device; however, at least one of them can be configured as a separate device, such as a mobile port or the like.

[0034] The object stage S is a stage for positioning the observation object 8 and is movable along an XY plane perpendicular to the Z direction in which the first light L1 falls on the observation object 8. Accordingly, the observation object 8 can be observed in the interference observation device 1 (an interference pattern can be captured) while the object stage S is moved along the XY plane, namely while the observation position of the observation object 8 is changed. [Example of an interference monitoring facility]

[0035] As described above, the processing unit 5 in the interference observation device 1 performs the optical adjustment process for optical settings with respect to the observation of the observation object 8. These optical settings include the adjustment of the relative position between the objective lens 13 and the observation object 8, and the adjustment of the optical path length of the second light L2 (reference light). The first setting, in the interference observation device 1, involves adjusting the position of the objective lens 13 relative to the observation object 8 by moving the objective lens 13 along the Z-direction using the actuator 16, thereby setting the focus position of the objective lens 13.As the latter setting, the optical path length of the second light L2 (optical path length difference between the first light L1 and the second light L2) is set by moving the reference objective lens 14 and the reference mirror 15 using the stepper motors 17 and 18.

[0036] Such optical settings are necessary for the following reasons, for example. Firstly, for instance, when using the [unclear] in the Fig. 1 and Fig. In the internal observation shown in Figure 2, when the interior of the observed object 8 is observed through the first layer 81, the measured value of the thickness or refractive index of the first layer 81 may deviate from a target value. Therefore, even if the focus position of the objective lens 13 and the optical path length of the second light L2 are set based on the nominal values, it is to be feared that errors in the focus position of the objective lens 13 and the optical path length of the second light L2 will occur due to the deviation, and therefore a satisfactory interference pattern cannot be obtained.

[0037] For example, if the first layer 81 is made of glass, its nominal refractive index is 1.51 and its nominal thickness is 400 µm, the adjustment amounts calculated on the basis of the nominal values ​​were as follows: a movement amount of the objective lens 13 is 256 µm, and a movement amount of the reference mirror 15 is 340 µm; however, the adjustment amounts calculated on the basis of the measured values ​​were as follows: a movement amount of the objective lens 13 is 270 µm, and a movement amount of the reference mirror 15 is 365 µm.Another example: If the first layer 81 consists of resin, has a nominal refractive index of 1.59, and a nominal thickness of 1000 µm, the adjustment amounts calculated based on the nominal values ​​were as follows: a movement amount of the objective lens 13 is 629 µm and a movement amount of the reference mirror 15 is 961 µm; however, the adjustment amounts calculated based on the measured values ​​were as follows: a movement amount of the objective lens 13 is 590 µm and a movement amount of the reference mirror 15 is 927 µm. Thus, there are discrepancies between the adjustment amounts calculated based on the nominal values ​​and those calculated based on the measured values, and optical adjustments cannot be satisfactorily performed by adjustments based solely on the nominal values.

[0038] Furthermore, the thickness or refractive index of the first layer 81 can change depending on the observation position, which also leads to errors in the focus position of the objective 13 and the optical path length of the second light L2, and therefore it is to be feared that a satisfactory interference image cannot be acquired. Therefore, an optical adjustment process described below is carried out in the interference observation device 1.

[0039] With reference to Fig. Section 3 describes a relationship between the amount of movement of the objective lens 13 and the amount of change in the optical path length of the second light L2. The equation transitions from a state in which the focus position of the objective lens 13 is on a front surface of the observation object 8 with a refractive index n1 and a thickness d, as indicated by a dashed line, to a state in which the distance between the observation object 8 and the objective lens 13 is reduced by δd, as indicated by a solid line, and the focus position is on a rear surface of the observation object 8. In this case, δd = d / n1, and the amount of the increase in the optical path length of the first light L1 is expressed by equation (1). Theoretically, the optical path length of the second light L2 would have to be adjusted so that it increases by the amount of the magnification.The entry amounts based on the nominal values ​​described above can be calculated using this method. [Equation 1] −δd+n1d=n12−1n1d

[0040] Settings based on the nominal values ​​can also be made if the observation object 8 has a large number of layers. With reference to Fig. Section 4 describes a relationship between the magnitude of the movement of the objective lens 13 and the magnitude of the change in the optical path length of the second light L2. Fig. Figure 4 illustrates a case where the observation object 8 has three layers. In an object having N layers with different refractive indices, when the light is focused onto a lower surface of an Nth layer, the distance between the observation object 8 and the objective lens 13 must be adjusted so that it is reduced by Δd, expressed by equation (2), compared to a state where the light is focused onto an upper surface of a first layer. [Equation 2] ∑d=∑m=1Ndmnm

[0041] In this case, the magnitude of the increase ΔOPD in the optical path length of the first light L1 is expressed by equation (3). Theoretically, the optical path length of the second light L2 would have to be adjusted so that it increases by the amount of this increase. [Equation 3] ΔOPD=∑m=1Nnm2−1nmdm

[0042] The above-mentioned calculation allows the distance between the observation object 8 and the objective lens 13, as well as the optical path length, to be set based on the nominal values, even if a large number of layers with different refractive indices are present.

[0043] With reference to Fig. Section 5 describes an example of the process (optical adjustment procedure) performed in the interference observation device 1. In general, this process involves capturing a first interference image and a second interference image, in which the optical path length difference between the first light L1 and the second light L2 is adjusted by changing the optical path length of the second light L2, and the focus position of the objective lens 13 is adjusted based on the first and second interference images.The first interference image is acquired in a state where the reference mirror 15 is in a forward position (for example, in a first position close to the reference objective lens 14), and the second interference image is acquired in a state where the reference mirror 15 is in a rear position (for example, in a second position that is further away from the reference objective lens 14 than the forward position). The process is subsequently described using a diagram. Fig. The process is described in the flowchart shown in section 5. After the schematic description of the entire process, the details of the individual processes are described where necessary.

[0044] The initial state of the interference observation device 1 is not limited; however, the focus position of the objective lens 13 and the optical path length of the second light L2 can be adjusted by a coarse adjustment process, described later, based on the nominal thicknesses and refractive indices of the first layer 81 to the third layer 83 of the observation object 8. In the coarse adjustment process, the focus position of the objective lens 13 and the optical path length of the second light L2 are adjusted, based on the thicknesses, refractive indices, and arrangement order of the first layer 81 to the third layer 83, to capture a user-specified interference pattern of the observation surface R. A fine adjustment process, described below, is used to perform optical adjustment with higher accuracy than the coarse adjustment process.

[0045] Once the process has started, the processing unit 5 first controls the piezoelectric element 19 to move the reference mirror 15 to the front position (step S1). The image sensor 4 then performs an image acquisition to capture four interference images (step S2). The processing unit 5 then constructs (captures) a first interference image based on the four interference images acquired in step S2 (step S3). The processing unit 5 then calculates a first evaluation score based on the first interference image acquired in step S3 (step S4). “f(a = front)” specifies a first evaluation score calculated based on the first interference image acquired in a state where the reference mirror 15 is in the front position.“f” is a function for calculating a rating based on the interference pattern, and “a = front” indicates that the reference mirror 15 is in the front position. The processing unit 5 overwrites and stores the first rating calculated in step S4 in a section of memory area 51, which is used to store the first rating.

[0046] The processing unit 5 then determines whether the absolute value (Abs) of a difference calculated by subtracting f(a = rear), which is a second evaluation value calculated based on the second interference image captured in a state where the reference mirror 15 is in the rear position, from f(a = front), which is the first evaluation value calculated based on the first interference image captured in a state where the reference mirror 15 is in the front position, is greater than a predefined limit (step S5). The values ​​of f(a = front) and f(a = rear) used in step S5 are currently stored in a region of memory area 51, which is used to store the first and second evaluation values.f(a = rear) is calculated in step S12, which will be described later, and stored in a portion of memory area 51, which is used to store the second evaluation value. As will be described later, since a first process, consisting of steps S1 to S8, and a second process, consisting of steps S9 to S16, are executed alternately and repeatedly, f(a = rear) is calculated and stored in memory area 51 even before step S5 is executed.

[0047] If, in step S5, the absolute value of f(a = front) - f(a = back) is greater than the limit (YES in step S5), processing unit 5 performs a focus adjustment (step S6). Conversely, if, in step S5, the absolute value of f(a = front) - f(a = back) is less than or equal to the limit (NO in step S5), processing unit 5 causes the observation position of the observed object 8 to move to the next observation position by moving the stage S along the XY plane without performing a focus adjustment (step S7). Processing unit 5 also performs the process of step S7 after step S6. The processes of steps S6 and S7 (focus adjustment and stage movement) can be performed simultaneously and in parallel. This also applies to steps S14 and S15, which are described later.

[0048] After step S7, processing unit 5 determines whether the current observation position is a final observation position (step S8). If, in step S8, the current observation position is the final observation position (YES in step S8), the process terminates. Conversely, if, in step S8, the current observation position is not the final observation position (NO in step S8), processing unit 5 continues with the process from step S9.

[0049] In step S9, the processing unit 5 controls the piezoelectric element 19 to move the reference mirror 15 from the front position to the rear position. The image sensor 4 then performs an image acquisition to capture four interference images (step S10). The processing unit 5 then constructs (captures) a second interference image based on the four interference images acquired in step S10 (step S11). The processing unit 5 then calculates the second evaluation value based on the second interference image acquired in step S11 (step S12). The processing unit 5 overwrites and stores the second evaluation value calculated in step S12 in the area of ​​memory 51 designated for storing the second evaluation value.

[0050] The processing unit 5 then determines whether the absolute value of a difference obtained by subtracting f(a = back) from f(a = front) is greater than the aforementioned limit (step S13). The value of f(a = front) and f(a = back) used in step S13 is a value currently stored in memory area 51, which is used to store the first and second evaluation values.

[0051] If, in step S13, the absolute value of f(a = front) - f(a = back) is greater than the limit (YES in step S13), processing unit 5 performs a focus adjustment (step S14). Conversely, if in step S13 the absolute value of f(a = front) - f(a = back) is less than or equal to the limit (NO in step S13), processing unit 5 causes the observation position of the observed object 8 to move to the next observation position by moving the object stage S along the XY plane without performing a focus adjustment (step S15). Processing unit 5 also executes the process of step S15 after step S14.

[0052] After step S15, processing unit 5 determines whether the current observation position is the final observation position (step S16). If, in step S16, the current observation position is the final observation position (YES in step S16), the process terminates. If, however, the current observation position is not the final observation position (NO in step S16), processing unit 5 returns to the process from step S1 in step S16. In this way, in this example, the first process, consisting of steps S1 to S8, and the second process, consisting of steps S9 to S16, are executed alternately and repeatedly until the observation position reaches the final observation position.

[0053] As in Fig. As shown in Figure 6, the reference mirror 15 moves between the front and rear positions during this process (steps S1 and S9), and at each position, an image acquisition is performed by the image sensor 4 to capture four interference images (steps S2 and S10). Furthermore, during the movement of the reference mirror 15, a focus adjustment process (optical adjustment process) is performed (steps S3 to S6 and S11 to S14), and the stage S moves along the XY plane (steps S7 and S15). Preferably, the movement of the stage S is a distance slightly smaller than the width of a field of view. This process makes it possible to acquire a large number of images and spatially align them to produce a composite image. Fig. Figure 6 shows the time sequence of the image acquisition (exposure) of the image sensor 4 and the time sequence of the movement of the object stage S.

[0054] Furthermore, it shows Fig. 6 the amount of movement of the piezo element 19. As in Fig. As shown in Figure 6, the piezoelectric element 19 is finely moved according to the image acquisition time of four interference images. Accordingly, the optical path length difference between the first light L1 and the second light L2 differs between the four interference images. In this example, the difference between the first interference image, acquired when the reference mirror 15 is in the front position, and the second interference image, acquired when the reference mirror 15 is in the rear position, is greater than the wavelength λ of the light emitted by the light source 2. This is because the distance between the front and rear positions is greater than the wavelength λ.Meanwhile, the magnitude of the change in the optical path length of the second light L2 differs between the four interference images, each captured at the front and rear positions, by a value smaller than the wavelength λ. This is because the motion of the reference mirror 15 for capturing the four interference images is smaller than the wavelength λ and smaller than the distance between the front and rear positions. Specifically, in this example, the magnitude of the change in the optical path length of the second light L2 differs between the four interference images by λ / 4.

[0055] Fig. Figure 7 shows an example of the four interference patterns captured in step S2. Fig. Figure 8 shows an example of the first interference pattern, which was constructed (captured) from the four interference patterns in step S3. The first interference pattern can be a real-part pattern or an imaginary-part pattern, which is described below, or it can be an amplitude pattern (interference pattern-amplitude pattern) or a phase pattern. Here, the construction of the first interference pattern and the calculation of the first weighting score based on the first interference pattern (steps S3 and S4) are described; however, the same applies to the construction of the second interference pattern and the calculation of the second weighting score based on the second interference pattern (steps S11 and S12).

[0056] With reference to Fig. Section 9 describes a process (steps S3 and S4) for capturing the first interference pattern from the four interference patterns captured in step S2 and for calculating the first evaluation value from this first interference pattern. This process is performed by processing unit 5. First, four interference patterns are captured (step S21). Then, a real part Re and an imaginary part Im of the first interference pattern are calculated (step S22). In step S22, a complex number image is generated: Comp = Re + iIm. The real part Re corresponds to a real part image, and the imaginary part Im corresponds to an imaginary part image. Subsequently, an amplitude image and a phase image of interference patterns (interference fringes) are generated (step S23).

[0057] The amplitude image is calculated by Abs(Comp), which is an absolute value calculation of a complex number, and the phase image is calculated by Arg(Comp), which is an argument calculation of complex numbers. Specifically, if the image of a complex number is Comp(x, y) = Re(x, y) + iIm(x, y) (where x and y are coordinates in the image), then Abs(Comp(x, y)) = sqrt(Re(x, y)). 2 + Im(x, y) 2 , Arg(Comp(x, y)) = atan2(Re(x, y), Im(x, y)). sqrt is a function that calculates the square root of a numerical value, and atan2 is a function that calculates one argument of a two-dimensional vector with two given arguments as elements. Subsequently, the in-image mean of the amplitude image Abs(Comp) is calculated as the first evaluation value (step S24).

[0058] In this example, a first interference pattern is acquired from the four interference patterns. The optical path length difference (phase shift interval) of the second light L2 between the four interference patterns is λ / 4. In this case, in step S22, the real part Re of the complex number image is calculated using "I1 - I3", and the imaginary part Im is calculated using "I1 - I2". I1 to I4 correspond to the four successively acquired interference patterns. Such an algorithm is called the "λ / 4 interval four-point phase shift method" (Reference Literature 1: "Field Guide to Interferometric Optical Testing" SPIE Press, ISBN 978-0-8194-6410-0, 2006, page 36). λ / 4 can be rewritten as π / 2 or 90°.

[0059] With reference to Fig. Section 10 describes the process of adjusting the focus in steps S6 and S14. This process is executed by the processing unit 5. First, it is determined whether the first evaluation value f(a = front) is greater than the second evaluation value f(a = back) (step S31). If f(a = front) is greater than f(a = back) (YES in step S31), the distance between the objective lens 13 and the observation object 8 is increased in step S31 by an amount obtained by multiplying the value of f(a = front) - f(a = back) by a predetermined coefficient (step S32). Specifically, in step S32, the actuator 16 is controlled such that the objective lens 13 moves away from the observation object 8 by this amount.In step S31, if f(a = front) is less than or equal to f(a = back) (NO in step S31), the distance between the objective lens 13 and the observation object 8 is reduced by an amount obtained by multiplying the value of f(a = back) - f(a = front) by the coefficient mentioned above (step S33). Specifically, in step S33, the actuator 16 is controlled such that the objective lens 13 moves closer to the observation object 8 by this amount.

[0060] The focus position of the objective lens 13 is adjusted by the process described above. Furthermore, in the process described above, the focus position of the objective lens 13 is adjusted while the stage S is moved along the XY plane, specifically during observation of the observation object 8 by changing the observation position of the observation object 8 (during the acquisition of the first and second interference images). In other words, the focus adjustment process, based on the first and second interference images, is performed in response to the movement of the stage S along the XY plane.

[0061] In this example, the observation position of the observed object 8 along the XY plane differs between the first and second interference images. This is because the first and second interference images are captured from different observation positions. For simplicity, the focus adjustment is described as an optical setting in this description; however, the adjustment of the optical path length of the second light L2 can be performed concurrently with the focus adjustment. As described later, the adjustment of the optical path length of the second light L2 can be performed simultaneously with the focus adjustment, based on a weighting value common to the focus adjustment, or based on a weighting value different from that of the focus adjustment.

[0062] As in this example, when the position of the reference mirror 15 is changed between the front and rear positions to capture the first and second interference images, the distortion of the interference patterns in the captured interference images changes, but the focus position of the lens 13 does not change, and therefore the signal-to-noise ratio decreases, but the captured interference images can still be used as interference images. The bowl-shaped distortion that appears in the interference patterns can be corrected by simple processing.

[0063] With reference to the Fig. Sections 11 to 14 describe in more detail the focus setting in the interference observation device 1. As in Fig. As shown in Figure 11, the thickness of the first layer 81 of the observed object 8 can change depending on the observation positions A, B, and C. As shown in Fig. As shown in Figure 12, in the interference observation device 1, for example, no focus adjustment is required at position A, since the absolute value of f(a = front) - f(a = back) (the absolute value of a difference between the first evaluation value and the second evaluation value) is less than or equal to a predefined limit. This case corresponds to the processes described above in steps S5 and S13. This determination can also be seen as determining whether a gradient Δf(a) / Δa of the function f(a) at the corresponding position of the reference mirror 15 is greater than a predefined value. Fig. In section 12, the reference mirror 15 located in the front position (“a = front”) is represented by “+Δa”, and the reference mirror 15 located in the rear position (“a = rear”) is represented by “-Aa”. This point also applies to Fig. 14.

[0064] Similar to position A, at position B, for example, since the absolute value of f(a = front) - f(a = back) is less than or equal to the predetermined limit, it is determined that no focus adjustment is necessary. Meanwhile, at position C, for example, since the absolute value of f(a = front) - f(a = back) is greater than the predetermined limit, it is determined that a focus adjustment is necessary. In this case, a focus adjustment is performed (S6 and S14). In this way, in the interference observation device 1, the need for a focus adjustment (optical adjustment) is determined based on the slope (derivative) of the function f (optimization function) to calculate an evaluation value based on the interference images. Specifically, the focus adjustment is not performed if the gradient of the function f is small, while it is performed if the gradient of the function f is large.

[0065] By performing such a process, observation can be carried out while the focus position of the objective lens 13 remains aligned with the observation surface R (while the focus is fixed). For example, as in Fig. Figure 13 illustrates the case of observing an interface C1 between the second layer 82 and the third layer 83. In this case, it is necessary to focus on interface C1 and not on an interface C2 between the first layer 81 and the second layer 82. Meanwhile, for example, as in Fig. As shown in Figure 14, in the function f(a), a maximum value due to interface C2 may be greater than a maximum value due to interface C1. If, in such a case, the position of the reference mirror 15 is simply moved significantly to maximize the function f(a), it is possible that the position of the reference mirror 15 will be set to a position corresponding to the maximum value due to interface C2. In contrast, during the focus adjustment process in the interference observation device 1, since the reference mirror 15 is moved finely to obtain a gradient (the difference between the first evaluation value and the second evaluation value), and the focus adjustment is performed based on the gradient, the position of the reference mirror 15 can still be aligned to the position corresponding to the maximum value due to interface C1 (focus lock). [Further operational example]

[0066] In the example described above, the object stage S moves while the reference mirror 15 moves between the front position and the rear position ( Fig. 6); however, as in (a) of Fig. As shown in Figure 15, the object stage S can move along the XY plane after four interference images have been acquired in a state where the reference mirror 15 is in the front position, and four interference images have been acquired in a state where the reference mirror 15 is in the rear position. In this case, as in the example described above, the difference between the first and second evaluation values ​​is calculated based on the first four interference images and the last four interference images, and the focus adjustment process is performed. In this case, for example, the processes described above in steps S7 and S8 are omitted. For example, an interference image created based on eight interference images can be used as the observation result at each observation position.

[0067] Alternatively, seven interference images can be acquired while the phase is changed in λ / 4 intervals, with interference image numbers 1 to 4 for the first interference images, interference image numbers 4 to 7 for the last interference images, and the fourth interference image being shared. In this case, the difference can be calculated by obtaining the first evaluation value from the first interference images and the second evaluation value from the last interference images, and a phase image, used as an observation result at each observation position, can be obtained by a λ / 4 interval seven-point phase shift method. Fig. 19, which will be described later, will be generated.

[0068] As in (b) of Fig. As shown in Figure 15, the acquisition of the first four interference images and the acquisition of the last four interference images can also be performed sequentially. In this case, the efficiency of image acquisition can be improved.

[0069] In the example described above, the first process, consisting of steps S1 to S8, and the second process, consisting of steps S9 to S16, are executed alternately and repeatedly, resulting in sequential processing; however, parallel processing can also be performed, as in the Fig. Figures 16 to 19 illustrate this. In this example, processing unit 5 executes in parallel a first process S40 (image acquisition thread), which relates to image acquisition, a second process S50 (image processing thread), which relates to image processing, and a third process S60 (motion amount calculation thread), which relates to the parallel calculation of a motion amount.

[0070] As in Fig. As shown in Figure 16, in the first process S40, the processing unit 5 first controls the piezoelectric element 19 to move the reference mirror 15 to the front position (step S41). Subsequently, the image sensor 4 performs image acquisition to capture four interference images corresponding to the first interference image, and the processing unit 5 acquires initial data corresponding to the four interference images from the image sensor 4 and stores the initial data in a first memory area (process wait FIFO) of the memory area 51 (step S42). The processing unit 5 then moves the observation position of the observed object 8 to the next observation position by causing the object stage S to move along the XY plane (step S43).

[0071] The processing unit 5 then controls the piezoelectric element 19 to move the reference mirror 15 to the rear position (step S44). The image sensor 4 then performs an image acquisition to capture four interference images corresponding to the second interference image, and the processing unit 5 acquires second data corresponding to the four interference images from the image sensor 4 and stores the second data in the first memory area of ​​memory area 51 (step S45). The processing unit 5 then causes the observation position of the observed object 8 to move to the next observation position by causing the object stage S to move along the XY plane (step S46). After the execution of step S46, the processing unit 5 returns to the process of step S41.In this way, in the first process S40, the processes of steps S41 to S43 and the processes of steps S41 to S43 are executed alternately, and the first and second data are stored sequentially in the first memory area, which is a process-waiting first-in-first-out (FIFO) memory. The first and second data are flagged with information indicating whether an image was captured at the front or the back position.

[0072] As in Fig. As shown in Figure 17, in the second process S50, processing unit 5 first determines whether the first data or the second data is stored in the first memory area of ​​memory space 51 (step S51). In step S51, if it is determined that the first data or the second data is stored in the first memory area (YES in step S51), processing unit 5 generates the first interference image or the second interference image based on the first data or the second data by performing image processing (step S52). If in step S51 it is determined that the first data or the second data is not stored in the first memory area (NO in step S51), processing unit 5 executes the process of step S51 again.

[0073] Following step S52, processing unit 5 stores the first or second interference image generated in step S52 in memory area 51 (step S53). Processing unit 5 then calculates the first or second evaluation value based on the first or second interference image generated in step S52 (step S54). Processing unit 5 then stores the first or second evaluation value calculated in step S54 in a second memory area (evaluation value data list) within memory area 51 (step S55). After step S55 is executed, processing unit 5 returns to the process from step S51.

[0074] As described above, the second process S50 alternately executes the process of generating the first interference image based on the first data acquired in the first process S40 and storing the first evaluation value corresponding to the first interference image in the second memory area of ​​memory area 51, and the process of generating the second interference image based on the second data acquired in the first process S40 and storing the second evaluation value corresponding to the second interference image in the second memory area. The second memory area is, for example, an evaluation value data list, and the first and second evaluation values ​​are stored sequentially in the second memory area.

[0075] As in Fig. As shown in Figure 18, in the third process S60, processing unit 5 first waits for the first or second evaluation value to be stored in the second memory area (evaluation value data list) of memory area 51 (step S61). In step S61, when the first or second evaluation value is stored in the second memory area, processing unit 5 determines, based on the first evaluation value and the immediately preceding second evaluation value, whether the absolute value of f(a = front) - f(a = back) is greater than the limit (step S62). In step S62, if the absolute value of f(a = front) - f(a = back) is greater than the predetermined limit (YES in step S62), processing unit 5 sets the next movement amount of the objective lens 13 along the Z direction to a predetermined value by initiating the focus adjustment process ( Fig. 10) performs the steps S6 and S14 described above (step S63). In step S62, if the absolute value of f(a = front) - f(a = back) is less than or equal to the limit mentioned above (NO in step S62), processing unit 5 sets the next movement amount of the objective lens 13 along the Z direction to zero (step S64). After executing step S63 or S64, processing unit 5 returns to the process of step S61. As described above, in the third process S60, each time the first evaluation value or the second evaluation value is stored in the second memory area in the second process S50, the focus adjustment process (optical adjustment process) is performed based on the first and second evaluation values ​​that were acquired immediately beforehand.

[0076] A method for capturing the first interference pattern or the second interference pattern is not limited to the method of the example described above, and, for example, the methods listed in the table in Fig. The methods described in section 19 are used. Fig. In the leftmost column, N indicates the number of interference patterns used to create the first interference pattern or the second interference pattern.

[0077] In the first-row method, the first or second interference pattern is acquired by spatial multiplexing using a micropolarizer array based on an interference pattern. In this case, the real part Re of the complex number image is calculated by "I1 - I3", and the imaginary part Im is calculated by "14 - I2". Such an algorithm is called a "Micropolarizer Array, Phase-Shifting Interferometer" (Reference Literature 1, page 44). In the second-row method, the first or second interference pattern is acquired by spatial fringe analysis based on an interference pattern. In this case, the real part Re of the complex number image is calculated by "LPF(I*cos(27ifx))", and the imaginary part Im is calculated by "LPF(I*sin(2nfx))". LPF is a spatial low-pass filter.Such an algorithm is called the “Spatial Synchronous and Fourier Method” (Reference Literature 1, page 43).

[0078] In the third-row method, the first or second interference pattern is acquired based on three interference patterns. In this case, the real part Re of the complex number image is calculated by "I1 - I2", and the imaginary part Im is calculated by "I3 - I2". Such an algorithm is called the "λ / 4-interval three-point phase shift method" (Reference Literature 1, page 36). In the fourth-row method, the first or second interference pattern is acquired based on three interference patterns. In this case, the real part Re of the complex number image is calculated by "I1 - 2I2 + I3", and the imaginary part Im is calculated by "Sqrt(3)*(I1 - I3)". Such an algorithm is called the “λ / 3-interval three-point phase shift method” (Reference Literature 2: “Interferogram Analysis for Optical Testing”, CRC Press, ISBN 978-0824799403, (2005), page 269).The procedure in the fifth line is the “λ / 4-interval four-point phase shift method” of the example described above.

[0079] In the procedure described in the sixth line, the first or second interference pattern is acquired based on five interference patterns. In this case, the real part Re of the complex number pattern is calculated by "-I1 + 2I3 - I5", and the imaginary part Im is calculated by "2(I2 - I4)". Such an algorithm is called the "Schwider-Hariharan five-point phase shift method" (Reference Literature 1, page 36). In the procedure described in the seventh line, the first or second interference pattern is acquired based on seven interference patterns. In this case, the real part Re of the complex number pattern is calculated by "-I2 + 4I1 - 2I6", and the imaginary part Im is calculated by "I1 - 3I3 + 3I5 - I7". Such an algorithm is called the “λ / 4-interval seven-point phase shift method” (Reference Literature 3: K. Hibino, BF Oreb, DI Farrant, and KG Larkin, “Phaseshifting for nonsinusoidal waveforms with phase-shift errors,” J. Opt.Soc. Am. A 12, 761-768 (1995)). In this way, the procedure for capturing the first interference pattern and the second interference pattern is not limited, and the first interference pattern or the second interference pattern can be captured, for example, based on one, three, four, five, or seven interference patterns.

[0080] For example, if the spatially synchronous and Fourier methods in Fig. When used in step 19, the first interference pattern or the second interference pattern is captured based on an interference pattern. In this case, as in Fig. As shown in Figure 20, image acquisition for capturing an interference image can be performed by the image sensor 4 in a state in which the reference mirror 15 is in the front position, and image acquisition for capturing an interference image in a state in which the reference mirror 15 is in the rear position can be performed by the image sensor 4.

[0081] In the example described above, the focus position of the objective lens 13 is adjusted while the stage S is moved along the XY plane; as shown in Fig. As shown in Figure 21, the focus adjustment (focus lock) process can be performed without moving the stage S (without changing the observation position along the XY plane). For example, if the observation object 8 has an internal nanostructure, it can be observed how the nanostructure changes over time in response to temperature changes. In this case, the observation position does not change from a fixed position during the observation; however, the focus conditions are assumed to change due to the thermal expansion of the observation object 8. Even in this case, the focus position can still be aligned on the observation surface R of the target by performing the focus lock after the initial adjustment. In this case, the observation position of the observation object 8 along the XY plane is identical between the first interference image and the second interference image.The first interference pattern and the second interference pattern are captured at the same observation position.

[0082] An interference monitoring device 1A according to another in Fig. The example shown in Figure 22 differs from the interference observation device 1 in that the interference observation device 1A further comprises a surface autofocus (AF) unit 6. The surface AF unit 6 includes an AF light source 61 that emits light L6 and a beam splitter 62, which is, for example, a dichroic mirror. Incidentally, a half-mirror, which does not exhibit wavelength selectivity, can also be used as the beam splitter 62, although the light utilization efficiency may decrease. The beam splitter 62 splits the light L6 into two lights and emits one of the two split lights L6 to the interference optical system 3. The light L6 emitted to the interference optical system 3 is reflected from the surface (outer surface) of the observation object 8 and returns to the surface AF unit 6 via the interference optical system 3 and the beam splitter 62.The surface AF unit 6 detects the light L6 reflected from the observation object 8 and, based on the detection result, adjusts the relative distance between the objective lens 13 and the surface of the observation object 8. For example, the objective lens 13 is moved along the Z-direction by the actuator 16 so that the surface AF unit 6 maintains the distance between the objective lens 13 and the observation object 8 at a predetermined distance. In this way, the surface AF unit 6 detects the light L6 emitted by the AF light source 61 and reflected from the surface of the observation object 8 through the interference optical system 3 and adjusts the relative position between the objective lens 13 and the surface of the observation object 8 based on the detection result.The interference observation device 1A has a filter 63 which is arranged between the beam splitter 12 and the reference objective lens 14 and which blocks the light L6 reflected from the beam splitter 12.

[0083] In the interference observation device 1A, the optical path length of the second light L2 can be adjusted simultaneously with the focus adjustment described above (steps S6 and S14) based on a common evaluation value for the focus adjustment. This point is described below.

[0084] As in (a), (b) and (c) of Fig. As shown in Figure 23, it is assumed that the thickness of the observed object 8 changes from d0 to d1, while the distance between the objective lens 13 and the observed object 8 is kept constant by the surface AF unit 6. (a) in Fig. Figure 23 shows the case of the change from a state in which the focus position of the objective lens 13 is on the front surface of the observation object 8 with refractive index n1 and thickness d0 (dashed line) to a state in which the distance between the objective lens 13 and the observation object 8 decreases by δd0, as indicated by a solid line, and the focus position is on the rear surface of the observation object 8 (solid line). (b) in Fig. Figure 23 shows the case of the change from a state in which the focus position of the objective lens 13 is on the front surface of the observation object 8 with refractive index n1 and thickness d1 (dashed line), to a state in which the distance between the objective lens 13 and the observation object 8 is reduced by δd1, as indicated by a solid line, and the focus position is on the rear surface of the observation object 8 (solid line). (c) in Fig. Figure 23 shows a state after the distance between the objective lens 13 and the observed object 8 has been changed by the surface AF unit 6 from that shown in (b) of Fig. The state shown in section 23 was set.

[0085] In (a) of Fig. 23 is the distance between the objective lens 13 and the observation object 8 WD - δd0 = WD - d 0 / n1, and in this case the correction amount of the optical path length of the second light L2 is expressed by (4) below. WD is the working distance of the objective lens 13 in air. [Equation 4] n12−1n1d0

[0086] In (c) of Fig. 23 is the distance between the objective lens 13 and the observation object 8 after focusing by the surface AF unit 6 WD - δd1 = WD - d 1 / n1, and in this case the adjustment amount of the optical path length of the second light L2 is expressed by (5) below. [Equation 5] n12−1n1d0

[0087] If the distance between the objective lens 13 and the observation object 8 is kept constant by the surface AF unit 6, and the absolute value of f(a = front) - f(a = back) is greater than the predetermined limit in the processes described above for steps S5 and S13, both the focus position of the objective lens 13 and the optical path length of the second light L2 can be considered as targets for the optical adjustment. In this case, an adjustment amount Δz of the focus position of the objective lens 13 is expressed by equation (6), where a direction in which the objective lens 13 approaches the observation object 8 is positive. [Equation 6] Δz=1n1(d1−d0)

[0088] The adjustment amount □OPD of the optical path length of the second light L2 is expressed by equation (7), where a direction in which the reference mirror 15 moves away from the beam splitter 12 is positive. [Equation 7] ΔOPD=n12−1n1(d1−d0)

[0089] Therefore, in this case, the ratio between the setting value for the optical path length of the second light L2 and the setting value for the focus position of the objective lens 13 should be set to n1. 2 - can be set to 1:1. For example, if the first layer 81 of the observed object 8 is a glass layer (n = 1.5), this ratio is 1.25:1, and if the first layer 81 is a silicon layer (n = 3.5), this ratio is 11.25:1.

[0090] For example, in a case where the interference observation device 1A is used, in steps S32 and S33 described above, when the distance between the objective lens 13 and the observation object 8 is adjusted by the amount obtained by multiplying the difference between the first evaluation value and the second evaluation value by the specified coefficient, the optical path length of the second light L2 should also be adjusted such that the ratio of the adjustment amount of the optical path length of the second light L2 to the adjustment amount of the focus position of the objective lens 13 (the difference between the objective lens 13 and the observation object 8) n1 2 - 1:1. Accordingly, the optical path length of the second light L2 can be set simultaneously with the focus setting based on a weighting value common to the focus setting.

[0091] Alternatively, the adjustment of the optical path length of the second light L2 can be performed based on a different evaluation value than that of the focus setting. In this case, the adjustment of the optical path length of the second light L2 is not limited to being performed by the interference monitoring unit 1A, which has the surface AF unit 6, and can also be performed by the interference monitoring unit 1, which does not have the surface AF unit 6. For example, if in step S31 f(a = front) is greater than f(a = back) (JA in step S31), the processing unit 5 increases the optical path length of the second light L2 by the amount obtained by multiplying the value of f(a = front) - f(a = back) by the specified coefficient (step S32).In step S32, stepper motors 17 and 18 are controlled such that the reference objective lens 14 and the reference mirror 15 move away from the beam splitter 12 by a certain amount. If, in step S31, f(a = front) is less than or equal to f(a = back) (NO in step S31), the optical path length of the second light L2 is shortened by the amount obtained by multiplying the value of f(a = front) - f(a = back) by the coefficient mentioned above (step S33). In step S33, stepper motors 17 and 18 are controlled such that the reference objective lens 14 and the reference mirror 15 move closer to the beam splitter 12 by a certain amount. The subsequent processes are the same as for focus adjustment. Accordingly, the optical path length of the second light L2 can be adjusted.

[0092] The focus adjustment is described in this case. Processing unit 5 calculates the magnitude of the curvature of the interference patterns in the phase image Arg (Comp) as the first or second evaluation value, instead of calculating the image-internal average value of the amplitude image Abs (Comp) as the first or second evaluation value, and performs the focus adjustment of the objective lens 13 based on the first and second evaluation values. In this case, processing unit 5 calculates the magnitude of the curvature of the interference patterns in the phase image as the first or second evaluation value in step S24. A procedure for calculating the magnitude of the curvature of the interference patterns based on the phase image is described later. The subsequent processes are the same as in the procedures described above.Accordingly, the adjustment of the optical path length of the second light L2 and the focus adjustment of the objective lens 13 can be performed. The adjustment of the optical path length of the second light L2 can be performed before or after the focus adjustment, or concurrently with the focus adjustment.

[0093] Additionally, instead of using only the amplitude or only the curvature of the interference patterns as indices for the first and second weighting values, a linear sum or a vector sum of a difference in the amplitude of the interference patterns and a difference in the magnitude of the curvature can be assumed as a new weighting function. The new weighting function g(a, b) of the interference patterns is a function with two variables, expressed by both an optical path length a and a focus deviation b between the first light L1 (object light) and the second light L2 (reference light).In this case, the derivative of the weighting value when only the optical path length of the reference light path (the optical path length of the second light L2) is changed is described as a partial derivative ∂g / ∂a of g(a, b) with respect to a, and the derivative of the weighting value when only the focus of the reference light path is changed is described as a partial derivative ∂g / ∂b of g(a, b) with respect to b (equation (8)). Furthermore, the gradient vector of the weighting value is described as a two-dimensional vector with ∂g / ∂a as the first element and ∂g / ∂b as the second element.If the gradient vector of the evaluation function is known, the steepest descent method or the conjugate gradient method can be used as a procedure for optimizing the parameters a and b in the direction of the maximum values ​​of the evaluation function, so that the setting of the optical path length of the second light L2 and the focus setting of the lens 13 can be carried out simultaneously or with a time interval based on the setting values ​​obtained by the optimization procedure. [Equation 8] Gradient vector equation = (∂g(a,b)∂a∂g(a,b)∂b)

[0094] Furthermore, if only the reference mirror 15 is moved along the optical reference path, the influence of the movement on the evaluation function g(a, b) contributes both in the form of a change in the optical path length and a change in focus. In this case, the adjustment of the optical path length of the second light L2 and the focus adjustment of the objective lens 13 can be based on the fact that the optical path length contributes mainly to the amplitude of the interference fringes and the amount of curvature contributes mainly to the curvature of the interference fringes (the interference pattern).

[0095] With reference to Fig. Reference 24 describes the procedure for calculating the magnitude of the curvature of the interference patterns based on the phase image. For example, a procedure based on a correlation with a test image with an estimated curvature magnitude can be considered. For example, in reference 2, a procedure for calculating the Zernike polynomial components of a wavefront from a phase image is described. The degree of curvature of the interference patterns can be related to a component of (9) known as the 'defocus' in the Zernike polynomial. [Equation 9] Z20=3(2ρ2−1)

[0096] For example, as in Fig. Figure 24 shows that by comparing the captured phase image with test images exhibiting curvature values ​​of +5.0, +10.0, +20.0, and the like, the curvature of the interference patterns is calculated based on the phase image. Incidentally, the method for calculating the curvature from the interference patterns is not limited to this procedure.

[0097] In the example described above, the reference mirror 15 is moved between the front and rear positions by the piezoelectric element 19 (steps S1 and S9). However, in steps S1 and S9, the reference mirror 15 can also be moved between the front and rear positions by the stepper motor 18. In this case, the stepper motor 18 can be configured to operate in a fine movement mode (first mode) and a coarse movement mode (second mode). In the fine movement mode, the step angle (distance between movements) of the stepper motor 18 is smaller than in the coarse movement mode, microstepping is possible, the pulse rate is high, and there is no limit check. In the coarse movement mode, the step angle (distance between movements) of the stepper motor 18 is larger than in the fine movement mode, microstepping is not possible, the pulse rate is low, and there is a limit check.In steps S1 and S9, the processing unit 5 causes the reference mirror 15 to move between the front and rear positions by driving the stepper motor 18 in the first mode, and acquires the first and second interference images (steps S3 and S11). Meanwhile, when the optical path length of the second light L2 is adjusted as a result of determining it based on the first and second interference images, the processing unit 5 causes the reference mirror 15 to move by driving the stepper motor 18 in the second mode. The optical adjustment can also be performed using this process in the same manner as described above. When performing this process, the piezoelectric element 19 can be omitted.Such a process is particularly effective when the spatially synchronous and Fourier method is used, which does not require any movement of the reference mirror 15 by the piezo element 19. [Application examples for the optical adjustment process]

[0098] With reference to Fig. Section 25 describes application examples for the optical adjustment process. A first application example is the initial adjustment of the interference observation device 1. The initial adjustment can be applied to both surface and internal observations, and the focus position of the objective lens 13 and the optical path length of the second light L2 are set. Since there is a possibility that a shift in the micrometer range may occur in the housing H of the optical module M due to temperature changes or aging, it can be assumed that the initial adjustment is performed at regular intervals (e.g., about once a week). In the table of Fig. 25 is represented by “O” if the adjustment is made by the optical adjustment procedure based on the first interference pattern and the second interference pattern described above, “separate” is represented if the adjustment is made by a procedure other than the optical adjustment procedure, and “-” is represented if the adjustment is not made.

[0099] During initial setup, the focus position of the objective lens 13 is first aligned with the observation surface R. Focus adjustment can be performed, for example, using a method such as contrast AF. Contrast AF is a technique for acquiring a multitude of interference images while scanning the focus position across the entire observation object 8 in the direction of the optical axis, and for identifying a point as the focus position where the interference image contrast evaluation function has its maximum. Subsequently, the processing unit 5 performs an optical adjustment process to set the optical path length (optical reference path length) of the second light L2, using the in-image mean of the amplitude image as either the first or second evaluation value.The processing unit 5 then sets the distance (reference side focus) between the reference objective lens 14 and the reference mirror 15 based on the curvature of the interference patterns in the phase image as either the first or second evaluation value. Specifically, the stepper motors 17 and 18 are controlled such that the distance between the reference objective lens 14 and the reference mirror 15 is a target distance. First, either the optical path length of the second light L2 or the reference side focus can be set. In the case of the initial setting, the stage S does not move along the XY plane.

[0100] A second application example is surface observation, as in Fig. Figure 26 is shown and should be considered. For surface observation, only the focus position of the objective lens 13 should be adjusted. The focus position of the objective lens 13 can be adjusted according to the process described above ( Fig. 5) are set. In the case of surface observation, the focus position is set while the stage S is moved along the XY plane.

[0101] As in Fig. As shown in Figure 27, in the case of surface observation, the calculation of the first and second evaluation values ​​and the setting of the focus position can be carried out in a simplified manner. For example, in the figure shown in Fig. In the example shown in Figure 27, the calculation of the first and second rating values ​​and the adjustment of the focus position are performed each time the observation position (the field of view) is changed three times (in this example, the calculation and adjustment are only performed in fields of view #3, #6, #9, etc.).

[0102] For surface observation, the stage S can be driven at a constant speed, instead of a method where the movement and stopping are repeated each time an image is acquired (stop and go), as in the example described above. In the example described above, the focus adjustment is performed each time the stage S moves once; as in the example described above. Fig. In the example shown in Figure 27, focus adjustment can be performed each time the object stage S moves a predetermined number of times, or, as in this example, focus adjustment can be performed while the object stage S is moving continuously. In either case, the processing unit 5 performs an optical adjustment process based on the first and second interference images in response to the movement of the object stage S along the XY plane. Incidentally, when focus adjustment is performed during the continuous movement of the object stage S, it is preferable to use a micropolarizer array phase-shifting interferometer or a spatially synchronous Fourier method, in which the first and second interference images are acquired based on an interference image.Furthermore, to suppress the superposition of motion artifacts on the interference pattern, it is preferable for the light source 2 to be pulse-controlled.

[0103] As in Fig. As shown in Figure 28, if there is a possibility that the lateral reference focus or the optical path length of the second light L2 may vary during observation, e.g., if the temperature environment is unstable, the process during initial setup and the process described above during surface observation can be combined in a hybrid manner. For example, if the observed object 8 is XY-scanned in a zigzag pattern, as in Figure 28, the process can be combined in a hybrid manner. Fig. In the example shown in Figure 28, the process can be performed during initial setup in the first field of view in each row (fields of view #1, #7, #15, etc.). Contrast AF takes time, but if it is performed intermittently, as in this example, its impact on the cycle time can be minimized. In the other fields of view, the focus position of the objective lens 13 can be adjusted according to the process used for surface observation, based on the first and second interference images. Incidentally, the fields of view in which the process is performed during initial setup can be those where contrast AF is easy to perform, such as the edge of the observed object 8.

[0104] If, in fact, a step to perform the optical adjustment process based on the first interference image and the second interference image is called a fine adjustment step, and a step to adjust the focus position of the objective lens 13 by contrast AF is called a focus position adjustment step, then in the example mentioned above, if the observation object 8 moves along the XY plane, the fine adjustment step or the focus position adjustment step is performed depending on the observation position of the observation object 8 along the XY plane.As described above, in the focus position setting step (contrast AF), where the direction in which the first light L1 falls on the observation object 8 is referred to as an incidence direction, a multitude of interference images are captured while the focus position of the lens 13 is scanned over the entirety of the observation object 8 in the incidence direction, and the focus position is set based on the capture result.

[0105] Once again on Fig. 25 Referring to this, internal observation can be considered a third application example. In internal observation, both the focus position of the objective lens 13 and the optical path length of the second light L2 are adjusted. In this case, as described above, the focus position of the objective lens 13 and the optical path length of the second light L2 can be adjusted based on a common evaluation value, using the interference observation device 1A with the surface AF unit 6.Alternatively, the optical process for adjusting the optical path length of the second light L2 can be performed using the in-image mean of the amplitude image as the first or second evaluation value, and the optical process for adjusting the focus position of the objective lens 13 can be performed using the amount of curvature of the interference pattern in the phase image as the first or second evaluation value. Both the optical process for adjusting the optical path length of the second light L2 and the optical process for adjusting the focus position of the objective lens 13 can be performed with each movement of the field of view (change of observation position). Alternatively, the optical adjustment processes can be performed in a staggered manner, so that only one is performed in the odd-numbered fields of view and only the other in the even-numbered fields of view.

[0106] Examples of an internal observation include, in addition to the case where the observed object 8 is a semiconductor device with a cap section as in the example described above, when a semiconductor device is observed through a transparent resin cap, when a semiconductor device is observed through a glass window, when a semiconductor device is observed through a semiconductor cap (in this case, the light source 2 emits infrared light), when a rear surface of a semiconductor device is observed (in this case, the light source 2 emits infrared light), when a bonding surface of a joined wafer is observed (in this case, the light source 2 emits infrared light), when voids are observed on a bonding surface of a joined wafer, when a connection section or bonding surface between glass and resin is observed.when a laser-processed surface is observed in a component made of glass, resin, or a semiconductor, when internal defects are observed in a liquid crystal panel, and the like.

[0107] A fourth application example is the setting when replacing the objective lens 13. For example, in the Fig. In the example shown in Figure 29, the objective lens 13 is interchangeably attached to the housing H, and an objective lens 13, selected from a plurality of objective lenses 13 (three in this example) with different magnifications, is attached to the housing H. When the objective lens 13 is exchanged to change the observation magnification in such a configuration, the optical adjustment can be carried out with high speed and high accuracy by performing the optical adjustment based on the first and second interference images described above.

[0108] As in Fig. As shown in Figure 30, when the lens 13 is replaced during the adjustment process, the lens 13 is first replaced (step S71). Then, the focus position of the lens 13 is aligned with the surface R. The focus adjustment can be made, for example, using a method such as contrast AF (step S72). Parallel to steps S71 and S72, the processing unit 5 controls the stepper motors 17 and 18 to adjust the optical path length of the second light L2 by a nominal offset of the lens 13 (step S73) (coarse adjustment). Following steps S72 and S73, the processing unit 5 performs the optical adjustment process to set the optical path length of the second light L2 using the image-internal mean of the amplitude image as either the first or second evaluation value (fine adjustment).

[0109] The nominal offset of the objective lens 13 is the value of the optical path length of the second light L2, which must be corrected according to any difference in optical path length for each objective lens 13, and is measured in advance. However, since errors in the micrometer range can occur due to aging or temperature effects of the objective lens, mechanical errors at the point where the objective lens is mounted, and similar factors, it is possible that optimal interference patterns cannot be obtained solely by adjusting the nominal offset. If an adapter is attached to the objective lens 13, the nominal offset is adjusted taking into account the contribution of the adapter.

[0110] As in Fig. As shown in Figure 31, an adapter 13a can be attached to at least one of a plurality of objective lenses 13. For example, when replacing the objective lens 13, in addition to changing the magnification, the case of switching from a dry objective lens to an immersion objective lens (water immersion or the like) can also be taken into account. The resolution of the interference observation is determined by the NA of the objective lens 13 or the reference objective lens 14, whichever has the lower NA. Therefore, it is advantageous if the magnification of the reference objective lens 14 is matched to the magnification of the objective lens 13 with the highest NA among the plurality of objective lenses 13. For example, if the plurality of objective lenses 13 have magnifications of 20X, 10X, and 5X, the magnification of the objective lens 13 with the highest NA is 20X, and therefore it is preferred that the magnification of the reference objective lens 14 be 20X.

[0111] Furthermore, generally speaking, even if a dry objective and an immersion objective have the same magnification, the immersion objective has a higher NA. Typical values ​​for a 10X objective are, for example, NA = 0.25 for a dry objective and NA = 0.30 for an immersion objective. In this case, if the reference objective 14 is a 10X dry objective, the high resolution of objective 13, which is a 10X water immersion objective, cannot be utilized, and therefore it is preferable for the reference objective 14 to be a 20X objective with an NA of 0.40.

[0112] To shorten the travel distance of the stepper motors 17 and 18 during adjustment when the objective lens 13 is replaced, adapters 13a corresponding to the magnifications can be attached to the multiple objective lenses 13. The adapter 13a can be a hollow element to extend the optical path length or an element in which a transparent dielectric plate is arranged. Generally, in the case of 5X, 10X, and 20X objective lenses, since the optical path length in the lens is in the order 5X < 10X < 20X, the travel distance of the stepper motors 17 and 18 during adjustment when the objective lens 13 is replaced can be shortened by adjusting the optical path length of the adapter 13a in the reverse order: 5X > 10X > 20X. It is preferred that the adapter 13a is mechanically connected or joined to the objective lens 13 and can be integrally removed and attached when the objective lens 13 is replaced.

[0113] Once again on Fig. 25. Referring to this, the fifth application example can be considered to be the adjustment of a mechanical difference in the lens. As in Fig. As shown in Figure 32, a conjugate plane 4b of an image acquisition surface 4a of the image sensor 4 can deviate from the focus position of the objective lens 13 due to minute manufacturing defects in the image sensor 4, the lens 42, or similar components. This deviation is typically on the order of a few micrometers, but is of a magnitude that cannot be neglected in interference observation. Even in this case, the conjugate plane 4b of the image acquisition surface 4a can be aligned to the focus position of the objective lens 13 using the optical process described above, based on the first and second interference images. The process for adjusting the mechanical difference of the lens is the same as for the initial alignment.However, when the mechanical difference of the lens is adjusted, the conjugate plane 4b of the image acquisition surface 4a deviates, and therefore it is more efficient to move only the reference mirror 15 with the stepper motor 18 while keeping the position of the reference lens 14 fixed. [Functions and Effects]

[0114] The interference observation device 1 comprises the light source 2, which emits light; the interference optical system 3, which includes the movable reference mirror 15, which splits the light emitted by the light source 2 into the first light L1 and the second light L2, and which emits the interference light L3 between the first light L1, which is reflected by the observation object 8, and the second light L2, which is reflected by the reference mirror 15; the image sensor 4, which detects the interference light L3; and the processing unit 5, which acquires an interference image based on the detection result of the interference light L3 and which performs the optical adjustment process for the optical adjustment with respect to the observation of the observation object 8.The processing unit 5 acquires the first interference image and the second interference image, in which the optical path length difference between the first light L1 and the second light L2 is made different by changing the optical path length of the second light L2, and performs the optical adjustment process based on the first interference image and the second interference image.

[0115] Since the optical adjustment process in the interference observation device 1 is performed based on the first interference image and the second interference image with different optical path length differences, which are detected by changing the optical path length of the second light L2, the optical adjustment can be carried out with high speed and high accuracy. In particular, the optical adjustment can be performed with high speed and high accuracy compared, for example, to scanning the focus position of the objective lens 13 across the entire observation object 8 in the direction of its thickness. If the observation object 8 is scanned in the Z direction, for example, for contrast AF, a high degree of noise remains in the acquisition result for several hundred milliseconds. Therefore, it is difficult to achieve a speed increase, and this method is not suitable, for example, for inline measurement.In contrast, the interference observation device 1 can perform optical adjustment with high speed and high accuracy and is also suitable for inline measurement.

[0116] Processing unit 5 calculates the evaluation values ​​(the first evaluation value and the second evaluation value) for the first interference image and the second interference image (steps S4 and S12) and performs the optical adjustment process based on the evaluation values ​​of the first and second interference images. Accordingly, the optical adjustment process can be carried out appropriately.

[0117] Processing unit 5 performs the optical adjustment process based on the difference between the first evaluation value, which is the evaluation value calculated based on the first interference image, and the second evaluation value, which is the evaluation value calculated based on the second interference image (steps S5 and S12). Accordingly, the optical adjustment process can be carried out appropriately.

[0118] After the second interference pattern is acquired, processing unit 5 performs the optical adjustment if the absolute value of the difference is greater than a predefined value, and does not perform the optical adjustment if the absolute value of the difference is less than or equal to the predefined value (steps S5 and S12). Accordingly, the optical adjustment process can be carried out appropriately.

[0119] When processing unit 5 performs the optical adjustment after acquiring the second interference image, it does so according to a relationship between the first and second evaluation values ​​(steps S31 to S33). Accordingly, the optical adjustment process can be carried out appropriately.

[0120] When processing unit 5 performs the optical adjustment after acquiring the second interference image, it adjusts the optical value by an amount corresponding to the magnitude relationship between the first and second evaluation values ​​(steps S32 and S33). Accordingly, the optical adjustment process can be carried out appropriately.

[0121] Processing unit 5 calculates the first or second evaluation value based on the amplitude image corresponding to the first or second interference image (step S24). Accordingly, the evaluation value can be calculated appropriately.

[0122] The processing unit 5 can calculate the evaluation value based on the amount of curvature of the interference patterns in the phase image corresponding to the first interference image or the second interference image ( Fig. 24). In this case too, the valuation value can be calculated in a suitable manner.

[0123] The processing unit 5 acquires the first and second interference images with different optical path length differences by moving the reference mirror 15 so that the optical path length of the second light L2 changes. Accordingly, the first and second interference images can be acquired appropriately.

[0124] The change in the optical path length of the second light L2 differs between the first and second interference patterns by a value greater than the wavelength of the light emitted by light source 2. Accordingly, the optical adjustment process can be carried out appropriately.

[0125] The optical adjustment performed in the interference observation device 1 involves adjusting the relative position between the objective lens 13 and the observation object 8. Accordingly, the relative position between the objective lens 13 and the observation object 8 can be adjusted.

[0126] The optical adjustment involves setting the optical path length of the second light L2 by moving the reference mirror 15. Accordingly, the optical path length of the second light L2 can be adjusted.

[0127] The optical setting includes an adjustment of the position of the reference lens 14. Accordingly, the position of the reference lens 14 can be adjusted.

[0128] The observation position of the observation object 8 along the XY plane (a plane that intersects the direction in which the first light L1 falls on the observation object 8) can be the same between the first interference pattern and the second interference pattern ( Fig. 21). In this case, the optical adjustment process can be carried out based on the first interference image and the second interference image, which were acquired at the same observation position.

[0129] The observation position of the observed object 8 along the XY plane can differ between the first interference pattern and the second interference pattern ( Fig. 5) In this case, the optical adjustment process can be carried out based on the first interference image and the second interference image, which were captured at different observation positions.

[0130] The processing unit 5 performs the optical adjustment process based on the first and second interference images in response to the movement of the object stage S along the XY plane. Accordingly, the observation position can be changed by moving the observation object 8 during the optical adjustment process.

[0131] The processing unit 5 performs the optical adjustment process to set the relative position between the objective lens 13 and the observation object 8 based on the first and second interference images in response to the movement of the stage S along the XY plane. Accordingly, the observation position can be changed by moving the observation object 8 while the relative position between the objective lens 13 and the observation object 8 is being adjusted.

[0132] Processing unit 5 executes the first process (steps S1 to S8) and the second process (steps S9 to S16) alternately. In the first process, processing unit 5 acquires the first interference image (step S2), performs the optical adjustment process based on the first interference image and the second interference image acquired in the immediately preceding second process (steps S5 and S6), and moves the object stage S along the plane (step S7). In the second process, processing unit 5 acquires the second interference image (step S10), performs the optical adjustment process based on the second interference image and the first interference image acquired in the immediately preceding first process (steps S13 and S14), and moves the object stage S along the plane (step S15). Accordingly, the optical adjustment process can be performed through sequential processing.

[0133] The processing unit 5 executes the first process S40, the second process S50, and the third process S60 in parallel. In the first process S40, the processing unit 5 alternately performs a process of acquiring the first data to generate the first interference image from the image sensor 4, storing the first data in the first memory area of ​​memory space 51 (step S42), and then moving the object stage S along the XY plane (step S43), and a process of acquiring the second data to generate the second interference image from the image sensor 4, storing the second data in the first memory area (step S45), and then moving the object stage S along the XY plane (step S44).In the second process S50, the processing unit 5 alternately executes a process to generate the first interference image based on the first data acquired in the first process S40 (step S52) and to store the first evaluation value corresponding to the first interference image in the second memory area of ​​memory area 51 (steps S54 and S55) and a process to generate the second interference image based on the second data acquired in the first process S40 (step S52) and to store the second evaluation value corresponding to the second interference image in the second memory area (steps S54 and S55).In the third process S60, processing unit 5 performs the optical adjustment process based on the first and second assessment values ​​acquired immediately beforehand, each time the first or second assessment value is stored in the second memory area in the second process S50 (step S61). In this case, the optical adjustment process can be performed by parallel processing.

[0134] The processing unit 5 acquires the first and second interference images with different optical path length differences by moving the reference mirror 15 using the piezoelectric element 19 to adjust the optical path length of the second light L2, and performs the optical adjustment using the stepper motors 17 and 18. Accordingly, the optical adjustment process can be carried out using the piezoelectric element 19 and the stepper motors 17 and 18. Since the piezoelectric element 19 has a greater number of actuations over its lifetime than the stepper motor 18, the lifetime of the device can be extended by acquiring both the first and second interference images using the piezoelectric element 19.

[0135] The stepper motor 18 can be controlled in fine movement mode (first mode) and coarse movement mode (second mode) with a larger step angle than in fine movement mode. In this case, the processing unit 5 acquires the first interference image and the second interference image with different optical path length differences by driving the stepper motor 18 in fine movement mode to move the reference mirror 15 so that the optical path length of the second light L2 changes, and performs the optical adjustment by driving the stepper motor 18 in coarse movement mode. In this case, the design of the device can be simplified by performing the optical adjustment process using the stepper motor 18.

[0136] The stepper motors 17 and 18 used for the optical adjustment process can be other types of motors with a resolution from 1 micrometer to several micrometers. Examples of other motor types include a geared motor with a large reduction ratio and a servo motor.

[0137] The interference observation device 1A includes the surface AF unit 6. The surface AF unit 6 includes the AF light source 61, which emits the light L6. The interference optical system 3 detects the light L6 emitted by the AF light source 61 and reflected from the surface of the observation object 8 and adjusts the relative position between the objective lens 13 of the interference optical system 3 and the surface of the observation object 8 based on the detection result. In this case, the surface AF unit 6 can adjust the relative position between the objective lens 13 and the surface of the observation object 8.

[0138] In the interference observation device 1A, which includes the surface AF unit 6, the processing unit 5 can perform the optical adjustment process to set the relative position between the objective lens 13 and the observation object 8 based on the first and second interference images in response to the movement of the stage S along the XY plane, and the optical adjustment process to set the optical path length of the second light L2 by moving the reference mirror 15. In this case, the optical adjustment process to set the relative position between the objective lens 13 and the observation object 8 and the optical adjustment process to set the optical path length of the second light L2 can be performed while the observation object 8 is moving.

[0139] In the optical adjustment procedure performed with the interference observation device 1, the first and second interference images can be acquired based on the detection of the interference light from the first light L1, reflected from the surface of the observation object 8, and the second light L2, reflected from the reference mirror 15 (surface observation). Accordingly, in the case of surface observation, the optical adjustment can be performed to observe the surface of the observation object 8.

[0140] In the optical adjustment procedure, the first and second interference images can be acquired based on the detection of the interference light from the first light L1, which is reflected within the observation object 8, and the second light L2, which is reflected from the reference mirror 15 (internal observation). Accordingly, in the case of internal observation, the optical adjustment can be carried out to observe the interior of the observation object 8.

[0141] In the optical adjustment method, the optical adjustment process can be carried out based on the first interference pattern and the second interference pattern in response to the movement of the observed object 8 along the XY plane. In this case, the optical adjustment process can be carried out while the observed object 8 is moving.

[0142] In the optical adjustment procedure, the optical process for adjusting the optical path length of the second light L2 can be carried out by moving the reference mirror 15 based on the first interference image and the second interference image when the objective lens 13 is exchanged (adjustment when the objective lens 13 is exchanged). Accordingly, the optical adjustment can be performed when the objective lens 13 is exchanged. [Variation examples]

[0143] The present disclosure is not limited to the examples described above. For instance, the material and shape of each embodiment are not limited to the material and shape described above, and various materials and shapes may be used.

[0144] In the example described above, the first and second interference images are acquired by moving the reference mirror 15 to change the optical path length of the second light L2; however, the first and second interference images can also be acquired by moving the objective lens 13 to change the optical path length of the second light L2. In the example described above, the optical adjustment process is performed based on two interference images, namely the first and second interference images; however, the optical adjustment process can also be performed based on three or more interference images.

[0145] In steps S32 and S33 of the example described above, the distance between the objective lens 13 and the observation object 8 is changed by the amount obtained by multiplying the value of f(a = front) - f(a = back) by the given coefficient; however, the distance should be changed by an amount that is positively correlated with the value of f(a = front) - f(a = back), and the relationship between the value of f(a = front) - f(a = back) and the amount of change is not restricted to a proportional relationship.

[0146] The weighting value based on the amplitude image (the first weighting value or the second weighting value) is not limited to the image-internal average value of the amplitude image, but can also be a different value calculated based on the amplitude image. The weighting value based on the phase image is not limited to the amount of curvature of the interference patterns in the phase image and can also be a different value calculated based on the phase image. The weighting value can be calculated based on either the amplitude image or the phase image. The optical path length of the second light L2 can differ between the first and second interference images by a value smaller than the wavelength of the light emitted by light source 2. In this case, too, the optical adjustment process can be carried out in the same way as in the example described above.

[0147] In the example described above, the relative position between the objective lens 13 and the observation object 8 is adjusted by moving the objective lens 13 along the Z-direction using the actuator 16; however, instead or additionally, the relative position can also be adjusted by moving the stage S along the Z-direction. In this case, the stage S is designed to be movable in the Z-direction in addition to the X- and Y-directions. In this case, the actuator 16 can be omitted. The stage S should be movable along a direction that intersects the direction in which the first light L1 strikes the observation object 8, and can, for example, be movable in a direction inclined to the XY-plane.The actuators that drive the reference objective lens 14 and the reference mirror 15 are not limited to the stepper motors 17 and 18, but can also be other actuators such as servo motors.

[0148] In the process of calculating the first evaluation value based on the first interference image (step S4) and the process of calculating the second evaluation value based on the second interference image (step S12), the interference image can be subjected to spatial thinning (reduction of resolution) and then image processing in a subroutine specialized for obtaining the evaluation value. Image processing can be accelerated by generating an interference image, used as the test image, from a separate high-resolution image and calculating the evaluation value from the thinned image.

[0149] In the example described above, the interference-optical system 3 is designed as a Linnik interference type; however, the interference-optical system 3 (interference observation device 1) can also be designed as a Michelson interference type or as a Mirau interference type. The reference objective lens 14 can be omitted. [Example display]

[0150] With reference to Fig. 33 describes a display example, etc., in the display unit 53. During internal observation, the user specifies the observation surface R of the observed object 8 using the input unit 52 and the display unit 53. In the example of Fig. 33 The display unit 53 shows a first element 101, a second element 102, a hint element 103, a lens element 104, an interference image element 105, an image capture button 106, a coarse adjustment button 107, a fine adjustment button 108, an adjustment amount display element 109, a focus lock element 110, a limit value element 111 and a stage element 112 on a rectangular screen 53a.

[0151] The first element 101 is an element that relates to the input and display of layer information for the observation object 8. When the input unit 52 receives an initial input from the user representing the layer information, the display unit 53 displays the first element 101 according to the initial input. The layer information for the observation object 8 includes, for example, the thicknesses, refractive indices, and arrangement order of a multitude of the layers contained within the observation object 8. In this example, the observation object 8 has five layers: a first layer 84, a second layer 85, a third layer 86, a fourth layer 87, and a fifth layer 88. The five layers 84 to 88 are arranged in order of their distance from the object stage S (closer to the objective lens 13) and have thicknesses of 500 µm, 20 µm, 300 µm, 15 µm, and 600 µm, respectively, and refractive indices of 1.51, 1.00, 3.56, 1.00, and 3.56.The first layer 84 is a glass layer, the second layer 85 and the fourth layer 87 are air layers, and the third layer 86 and the fifth layer 88 are semiconductor layers (silicon layers).

[0152] In this example, the first element, 101, is a table that displays the thicknesses, refractive indices, and arrangement order (layer numbers) of the five layers 84 to 88. The table shows the layer numbers corresponding to the five layers 84 to 88 side by side in an order that reflects the arrangement order of the five layers. For example, the first element, 101, is located in the upper right corner of screen 53a.

[0153] The second element 102 is an element that graphically represents the five layers 84 to 88 of the observed object 8 in a mode that corresponds to the thicknesses and arrangement order according to the first input. In this example, the second element 102 consists of objects 102a, 102b, 102c, 102d, and 102e with a rectangular shape (layer shape), each corresponding to the five layers 84 to 88. The thicknesses of objects 102a to 102e correspond (proportionally) to the thicknesses of the five layers 84 to 88. The arrangement order of objects 102a to 102e corresponds to the arrangement order of the five layers 84 to 88. Objects 102a to 102e are represented, for example, in colors or patterns that correspond to the refractive index and the material. Since in this example the second layer 85 and the fourth layer 87 are air layers, the corresponding objects 102b and 102d are displayed transparently.Object 102a, corresponding to the first layer 84, which is a glass layer, is shown in light blue, and objects 102c and 102e, corresponding to the third layer 86 and the fifth layer 88, which are semiconductor layers, are shown in gray. For example, the second element 102 on screen 53a is positioned so that it borders the first element 101 in a left-right direction.

[0154] The indicator element 103 is an element that displays the observation surface R of the observation object 8. Indicator element 103 is displayed together with the second element 102 and indicates an interface specified as the observation surface R beneath the interfaces of the five layers 84 to 88, which are graphically represented as the second element 102. In this example, indicator element 103 is rendered as a dashed line and is displayed so that it overlaps the objects 102a to 102e corresponding to the five layers 84 to 88. In this example, the interface between the second layer 85 and the third layer 86 is specified as the observation surface R, and indicator element 103 is displayed between objects 102b and 102c.

[0155] The objective lens element 104 is an element that indicates the current position of the objective lens 13. The objective lens element 104 is displayed together with the second element 102. The objective lens element 104 is displayed at a position separated from the five layers 84 to 88 (objects 102a to 102e), which are graphically represented as the second element 102, by a distance corresponding to the relative position between the objective lens 13 and the observation object 8. Since, in this example, the objective lens 13 faces the first layer 84 during the actual observation, the objective lens element 104 is positioned above object 102a such that it faces object 102a, which corresponds to the first layer 84. The distance between the objective lens element 104 and object 102a corresponds to the distance between the objective lens 13 and the first layer.The display position of the objective lens element 104 changes when the objective lens 13 moves along the Z direction.

[0156] The interference image element 105 is an element that displays an interference image captured by the processing unit 5. This interference image can be the first interference image or the second interference image described above, but also an amplitude image, a phase image, or something similar. For example, interference image element 105 is located in the upper left corner of screen 53a, adjacent to the second element 102.

[0157] The image capture button 106, the coarse adjustment button 107, and the fine adjustment button 108 are located below the interference image element 105. For example, when the user clicks the image capture button 106, the image sensor 4 takes an image, and the captured interference image is displayed as the interference image element 105. Fig. Figure 33 shows a pointer 120, which gives the user an indication of the click position.

[0158] The following methods can be considered as methods for setting the image acquisition time. First, it can be assumed that image acquisition and the display of an interference image continue at all times. Alternatively, it can be considered that image acquisition and display are performed in response to clicking the image acquisition button 106. It can be provided that when the image acquisition button 106 is clicked, image acquisition and display are started, and when the image acquisition button 106 is clicked again, image acquisition and display are stopped. In this case, it is advantageous for the color or pattern of the image acquisition button 106 to be set differently during image acquisition than during non-image acquisition.Alternatively, image acquisition and display can be performed when the observation surface R is changed or when the stage S is moved along the XY plane to change the observation position. With methods other than the first, the processing load for image acquisition and display can be reduced.

[0159] The coarse adjustment button 107 indicates the execution of the coarse adjustment process, and the fine adjustment button 108 indicates the execution of the fine adjustment process. When the user clicks the coarse adjustment button 107, processing unit 5 executes the coarse adjustment process, and when the user clicks the fine adjustment button 108, processing unit 5 executes the fine adjustment process. The coarse adjustment process and the fine adjustment process are described later.

[0160] The adjustment amount indicator 109 is located below the first element 101 and the second element 102. The adjustment amount indicator 109 is a table displaying the "Z-stage movement amount," the "optical path length adjustment amount," and the "reference lens adjustment amount." The "Z-stage movement amount" corresponds to the amount by which the objective lens 13 is moved by the actuator 16 during the optical adjustment process (fine-tuning process, first optical adjustment process, described later). The "optical path length adjustment amount" corresponds to the amount by which the reference mirror 15 is moved by the stepper motor 18 during the optical adjustment process (fine-tuning process, second optical adjustment process, described later).The “reference lens adjustment amount” corresponds to the amount by which the reference lens 14 is moved by the stepper motor 17 in the optical adjustment process (fine adjustment process, third optical adjustment process, which will be described later).

[0161] The focus lock element 110 is located below the setting amount indicator element 109. The focus lock element 110 is an element representing a setting state that indicates whether the focus adjustment process (fine-tuning process) should be performed in response to the movement of the object stage S along the XY plane (whether focus locking should be performed). In this example, the focus lock element 110 has a rectangular checkbox with the text "FOCUS LOCK" displayed around the checkbox. When focus locking is ON, a check mark is displayed in the box, and when focus locking is OFF, no check mark is displayed in the box (the box remains empty). A third input that determines whether focus locking should be performed is received, for example, from the input unit 52.For example, the user sets the focus lock to ON or OFF by clicking an area within the box.

[0162] The limit element 111 is located below the focus lock element 110. Limit element 111 represents a limit value related to the fine-tuning process. This limit value is used in determining steps S5 and S13 described above. A fourth input for setting the limit value is received, for example, from input unit 52. The user sets the limit value by entering a numerical value. If the limit value is small, the fine-tuning process is performed frequently. While this improves observation accuracy, it reduces the service life of stepper motors 17 and 18 and increases the cycle time. If the limit value is large, the frequency of fine-tuning processes is reduced.In this case, the service life of stepper motors 17 and 18 can be extended and the cycle time reduced, but the observation accuracy is reduced.

[0163] The object stage element 112 is located below the setting amount indicator element 109 and to the right of the focus lock element 110 and the limit value element 111. The object stage element 112 has an operating indicator element 112a and a current position indicator element 112b. The operating indicator element 112a consists, for example, of four arrow-shaped elements indicating the directions up, down, left, and right. If the user clicks on one of the arrows of the operating indicator element 112a, for example, the object stage S moves in the direction (the X direction or the Y direction) corresponding to the arrow.

[0164] The current position indicator 112b is an element that numerically displays the current position of the object stage S on the XY plane and is arranged within a rectangular frame together with the operating indicator 112a. The current position of the object stage S displayed by the operating indicator 112a may, for example, be a reading from an encoder attached to a motor that drives the object stage S, or, if the object stage S has a distance measuring mechanism, the current position of the object stage S may be based on a reading from the distance measuring mechanism. The numerical value displayed by the current position indicator 112b may be an absolute value with respect to the origin of the object stage S, or a relative value if the coordinates are defined as the origin at the start of the observation.

[0165] With reference to Fig. Section 34 describes the optical adjustment procedure performed using the interference observation device 1. First, the input unit 52 receives the initial input, which represents the thicknesses, refractive indices, and arrangement order of the five layers 84 to 88 present in the observation object 8 (step S81, first input reception step). For example, if the user enters a numerical value, the initial input is received by the input unit 52.

[0166] Subsequently, the display unit 53 displays the first element 101, which represents the values ​​of the thicknesses and refractive indices of the five layers 84 to 88 according to the first input received in step S81, and the second element 102 (objects 102a to 102e), which graphically represents the five layers 84 to 88 in a mode that corresponds to the thicknesses and the arrangement order of the five layers 84 to 88 according to the first input (step S82, display step).

[0167] Subsequently, in a state where the display unit 53 shows the first element 101 and the second element 102, the input unit 52 receives a second input to specify the observation surface R from the interfaces between the five layers 84 to 88 (step S83, second input reception step). The second input is received, for example, when the user clicks and defines an area in the first element 101 or the second element 102 with the pointer 120. For example, the user specifies the interface between the first layer 84 and the second layer 85 in the table, which is displayed as the first element 101, as the observation surface R by clicking a position corresponding to the interface (surface section between layer number 1 and layer number 2).Alternatively, the user specifies the interface between the second layer 85 and the third layer 86 as the observation surface R by clicking a position that corresponds to the interface between object 102b, corresponding to the second layer 85, and object 102c, corresponding to the third layer 86, in objects 102a to 102e displayed as the second element 102. When the observation surface R is specified by the second input, the indicator element 103 is displayed at a position corresponding to the specified observation surface R.

[0168] Following step S83, the coarse adjustment button 107 is clicked by the user (step S84). When the coarse adjustment button 107 is clicked, the processing unit 5 performs the first optical adjustment process and the second optical adjustment process (step S85, optical adjustment step). In the optical adjustment step, the processing unit 5 performs the first optical adjustment process to adjust the relative position (the focus position of the objective lens 13) between the objective lens 13 and the observation object 8, and the second optical adjustment process to adjust the optical path length of the second light L2 by moving the reference mirror 15 based on the thicknesses and refractive indices of the five layers 84 to 88 according to the first input received in step S81, so that an interference pattern of the observation surface R is acquired according to the second input received in step S83.In this example, processing unit 5 performs the third optical adjustment process in the optical adjustment step to set the distance (reference side focus) between the reference objective lens 14 and the reference mirror 15, in addition to the first and second optical adjustment processes. The reference side focus is set, for example, according to the amount of movement of the reference mirror 15 in the second optical process.

[0169] The first to third optical adjustment processes constitute the coarse adjustment process described above. In the coarse adjustment process, the focus position of the objective lens 13, the optical path length of the second light L2, and the reference side focus are set based on the input values ​​of the thicknesses and refractive indices of the five layers 84 to 88 of the observation object 8. The coarse adjustment process can, for example, be carried out according to the same procedure as that described with reference to Fig. The three described adjustment procedures are based on the target values. The focus position of the objective lens 13 is set by the coarse adjustment process to the position of the observation surface R, which corresponds to the second input received in step S83. In addition, the optical path length of the second light L2 and the reference side focus are adjusted so that the optical path length and the focus length correspond to the focus position.

[0170] The optical adjustment procedure described above is implemented, for example, by executing an optical adjustment program P, which is located in Fig. 35 is shown. As in Fig. As shown in Figure 35, the optical adjustment program P is stored in memory area 51 of computer C. Memory area 51 can be a non-transient, computer-readable storage medium that stores the optical adjustment program P. Computer C implements the optical adjustment procedure by instructing the processor to read and execute the optical adjustment program P. The optical adjustment program P comprises a first input receiver module P1, a display module P2, a second input receiver module P3, and an optical adjustment module P4. The processes implemented by the execution of the first input receiver module P1, the display module P2, the second input receiver module P3, and the optical adjustment module P4 are the same as the processes of the first input receiver step, the display step, the second input receiver step, and the optical adjustment step described above.The optical setting program P can, for example, be stored in a state where it is permanently recorded on a physical recording medium such as a CD-ROM, a DVD-ROM, or a semiconductor memory. Alternatively, the optical setting program P can also be provided as a data signal via a communication network.

[0171] The coarse adjustment process is performed through the series of processes described above. When the fine adjustment button 108 is clicked after the coarse adjustment process, the processing unit 5 performs the fine adjustment process (additional adjustment process) (one fine adjustment step, one additional adjustment step). In the fine adjustment step, the processing unit 5 acquires the first interference image and the second interference image, in which the optical path length difference between the first light L1 and the second light L2 is made different by causing the reference mirror 15 to move to change the optical path length of the second light L2, and performs the first optical adjustment process, the second optical adjustment process, and the third optical adjustment process, as described above, based on the first and second interference images.The fine-tuning process is carried out, for example, by the procedure based on the first interference pattern and the second interference pattern, which is shown in . Fig. As described in section 4, an error in the optical adjustment may occur during the coarse adjustment process based on the target values ​​or the input values; however, such an error can be corrected by performing the fine adjustment process.

[0172] In the fine-tuning process, the limit value received by input unit 52 as the fourth input and represented by limit value element 111 is used as the limit value referenced in the determinations of steps S5 and S13 described above. The result of the fine-tuning process is displayed by the adjustment amount indicator element 109. The interference patterns (e.g., the first interference pattern and the second interference pattern) acquired for the optical adjustment process during the fine-tuning process may or may not be displayed as interference pattern element 105. When the focus of each layer (e.g.,The first layer (84) and the reference-side optical path length are optimized by the fine-tuning process. Furthermore, the thickness or refractive index of the corresponding layer is calculated backwards based on the optimal value after fine-tuning, and the thickness and refractive index values ​​displayed in the first element (101) can be corrected. The user can specify separately whether to perform this correction.

[0173] In a state where the focus lock is ON when observation is started after the coarse adjustment process and the stage S moves along the XY plane, the processing unit 5 performs the fine adjustment process in response to the movement of the stage S along the XY plane (for example, each time the stage S moves to the next observation position). Accordingly, observation can be carried out while the focus position of the objective lens 13 continues to be aligned with the observation surface R (while the focus is locked). As described above, the ON / OFF state of the focus lock is received by the input unit 52 as the third input and represented by the focus lock element 110.Incidentally, if the observation is carried out with the focus lock set to AN, it is advantageous to define the observation position as a section that is unlikely to change due to manufacturing conditions (e.g., a mark or similar provided on the observation object 8) and to perform the coarse adjustment process when the observation is started. In this case, the coarse adjustment process can be carried out under the same conditions every time.

[0174] With reference to Fig. Section 36 describes the advantages of being able to set the focus lock to ON or OFF. For example, if the focus lock is set to ON when two adjacent layers of the observation object 8 are partially peeled away from each other, the observation surface R followed by the focus lock may differ from the surface the user wishes to observe. For example, in (a) of Fig. 36 the focus position of the lower surface due to the focus lock, although the surface the user wants to observe is the peeled-off upper surface. In contrast, by setting the focus lock to OFF at the time indicated by an arrow in (b) of Fig. 36 is indicated, even in such a case a new setting is made by re-entering the thicknesses, the refractive indices and the arrangement order of the multitude of layers contained in the observation object 8. [Functions and Effects]

[0175] The interference observation device 1 is an interference observation device for observing the interior of the observation object 8, which has the five layers 84 to 88 (multiple layers), wherein the interference observation device comprises: the light source 2, which emits light; the interference optical system 3, which comprises the movable reference mirror 15 and the objective lens 13, which splits the light emitted by the light source 2 into the first light L1 and the second light L2, and which emits the interference light L3 between the first light L1, which is reflected from the observation surface R, which is located inside the observation object 8, and the second light L2, which is reflected from the reference mirror 15; the image sensor 4, which detects the interference light L3; the input unit 52, which receives an information input; the display unit 53, which displays the information; and the processing unit 5.which acquires an interference pattern based on the acquisition result of the interference light L3, and which performs the optical adjustment process for the optical adjustment with respect to the observation of the observation object 8. The input unit 52 receives the first input, which represents the thicknesses, refractive indices, and arrangement order of the five layers 84 to 88 (step S81). The display unit 53 displays the first element 101, which represents the values ​​of the thicknesses and refractive indices of the five layers 84 to 88 according to the first input, and the second element 102 (objects 102a to 102e), which graphically represents the five layers 84 to 88 in a mode that corresponds to the thicknesses and arrangement order of the five layers 84 to 88 according to the first input (step S82). In a state where the display unit 53 displays the first element 101 and the second element 102,The input unit 52 receives the second input to specify the observation surface R from the interfaces between the five layers 84 to 88 (step S83). The processing unit 5 performs the first optical adjustment process to set the relative position (focus position) between the objective lens 13 and the observation object 8, and the second optical adjustment process to adjust the optical path length of the second light L2 by moving the reference mirror 15, based on the thicknesses and refractive indices of the five layers 84 to 88 according to the first input, so that the interference pattern of the observation surface R is acquired according to the second input (step S85) (coarse adjustment process).

[0176] In the interference observation device 1, the first optical adjustment process is used to set the relative position between the objective lens 13 and the observation object 8. The second optical adjustment process is used to adjust the optical path length of the second light L2 by moving the reference mirror 15 based on the thicknesses and refractive indices of the five layers 84 to 88 corresponding to the first input, so that the interference pattern of the observation surface R corresponding to the second input is captured (coarse adjustment process). Accordingly, the relative position between the objective lens 13 and the observation object 8, as well as the optical path length of the second light L2, can be adjusted based on the thicknesses and refractive indices of the five layers 84 to 88 of the observation object 8, and the interference pattern of the observation surface R can be captured.Furthermore, in the interference observation device 1, the first element 101, which represents the thickness and refractive index values ​​of the five layers 84 to 88 according to the first input, and the second element 102, which graphically represents the five layers 84 to 88 in a mode corresponding to the thickness and stacking order of the five layers 84 to 88 according to the first input, are displayed on the display unit 53. In a state where the display unit 53 shows the first element 101 and the second element 102, the observation surface R is determined from the interfaces between the five layers 84 to 88. Accordingly, the ease of specifying the observation surface R from the interfaces between the five layers 84 to 88 can be improved. Therefore, the optical adjustment for internal observation can be carried out appropriately using the interference observation device 1.

[0177] The display unit 53 shows the interference pattern (interference pattern element 105) captured by the processing unit 5, in addition to the first element 101 and the second element 102. This improves the ease of viewing.

[0178] The display unit 53, together with the second element 102, displays the indicator element 103, which graphically represents the interface specified as observation surface R beneath the interfaces of the five layers 84 to 88 as the second element 102. Accordingly, the interface specified as observation surface R can be easily located.

[0179] The display unit 53, together with the second element 102, displays the objective lens element 104 to indicate the position of the objective lens 13 at a position spaced apart from one of the five layers 84 to 88, which are graphically represented as the second element 102, by a distance corresponding to the relative position between the objective lens 13 and the observation object 8. Accordingly, the relative position between the objective lens 13 and the observation object 8 can be easily determined.

[0180] The second input is received when the user specifies a region within the first element 101 or the second element 102. This further improves the ease of defining the observation surface R from the interfaces between the five layers 84 to 88.

[0181] Processing unit 5 performs the fine-tuning process (additional adjustment process) following the coarse-tuning process. During the fine-tuning process, processing unit 5 acquires the first and second interference images, in which the optical path length difference between the first light L1 and the second light L2 is differentiated by changing the optical path length of the second light L2. Based on these interference images, processing unit 5 then performs the first and second optical adjustment processes. This allows for more precise adjustment of the relative position between the objective lens 13 and the observation object 8, as well as the optical path length of the second light L2.

[0182] The processing unit 5 performs the fine-tuning process depending on the movement of the stage S along the XY plane. Accordingly, the observation position can be changed by moving the observation object 8, while the relative position between the objective lens 13 and the observation object 8 and the optical path length of the second light L2 are adjusted with higher accuracy.

[0183] The input unit 52 receives the third input to specify whether the fine-tuning process should be performed in response to the movement of the stage S along the XY plane (whether focus lock should be applied), and the display unit 53 shows an element representing the setting state of whether the fine-tuning process should be performed in response to the movement of the stage S along the XY plane based on the third input. Accordingly, it can be specified whether the fine-tuning process should be performed in response to the movement of the stage S, and the setting state of whether the fine-tuning process should be performed can be detected, and consequently, the focusing aid can be improved.

[0184] The input unit 52 receives the fourth input to specify a limit value in relation to the fine-tuning process, and the display unit 53 shows an element representing the limit value according to the fourth input. Accordingly, the limit value in relation to the fine-tuning process can be specified, the limit value can be recorded, and consequently, the adjustment can be improved.

[0185] The display unit 53 shows the adjustment value indicator 109, which represents the relative distance between the objective lens 13 and the observation object 8 and the magnitude of the optical path length of the second light L2, which is adjusted during the fine-tuning process. Accordingly, the result of the fine-tuning process can be recorded, and the light-gathering effect can be improved. Furthermore, it is possible to verify whether the optical adjustment is being performed correctly and how much error the optical adjustment value has compared to a theoretical value. [Examples of variations]

[0186] The display unit 53 should display at least the first element 101 and the second element 102, and must not display at least one of the other elements 103 to 112. For example, in the Fig. In the example shown in Figure 37, only the first element 101, the second element 102, the indicator element 103, the objective lens element 104, and the interference image element 105 are shown. If the focus lock element 110 is omitted, the focus lock can be automatically turned ON after the fine-tuning process is complete. If the limit value element 111 is omitted, a predefined value (a value hard-coded in the software, a value written in a settings file, or similar) can be used as the limit value when determining steps S5 and S13.

[0187] In the example described above, the interference observation device 1 is designed as an upright microscope; as in Fig. As shown in Figure 38, the interference observation device 1 can also be configured as an inverted microscope. In this case, as shown in Figure 38, the interference observation device 1 can be configured as an inverted microscope. Fig.Figure 39 shows the first element 101 and the second element 102 displayed in a mode corresponding to an inverted microscope. The interference observation device 1 can have the function of changing the display mode of the first element 101 and the second element 102 based on the information whether the interference observation device 1 is an upright microscope or an inverted microscope.

[0188] The first input, representing the thicknesses, refractive indices, and arrangement order of the five layers 84 to 88 contained in the observation object 8, and received in step S81, can be received when computer C reads a numerical value file containing the information corresponding to the first input. In this way, the input device is not limited to a device such as a mouse or keyboard and should be designed to receive an input of information. Alternatively, the first input can be received when computer C reads a recipe file that does not directly contain numerical value information (for example, a file containing observation conditions).In the example described above, it was stated that the user enters information by clicking; however, if the input unit 52 and the display unit 53 are designed as a touch panel, the user can enter information by touching the screen.

[0189] The second input for specifying the observation surface R from the interfaces between the five layers 84 to 88, received in step S83, can be received when the user specifies the observation surface R using a keyboard that forms the input unit 52. For example, the second input can be received when the user enters a layer number corresponding to the observation surface R that the user wishes to specify via the keyboard, or when the user selects the interface corresponding to the observation surface R that the user wishes to specify by pressing the up and down keys of the keyboard.

[0190] In the first element 101, a location corresponding to the observation surface R can be highlighted. For example, the location corresponding to the observation surface R can be shown in bold or in a different background color than the other sections. The number of the layer corresponding to the observation surface R can be represented by a number. The interference observation device 1 can have the function of not performing the focus adjustment or displaying an error message if the amount of movement from the surface (outer surface) of the observation surface R during the coarse adjustment process is greater than or equal to the working distance of the objective lens 13. In this case, damage to the objective lens 13 or the observation object 8 can be prevented. The interference observation device 1 can have the function of manually performing the fine adjustment process according to user instructions.

[0191] In the example described above, clicking the coarse adjustment button 107 causes processing unit 5 to perform the coarse adjustment process (step S85); however, receiving the second input to define the observation surface R in step S83 can also cause processing unit 5 to perform the coarse adjustment process. In this case, processing unit 5 can perform the coarse adjustment process immediately after receiving the second input or after a certain period of time.The case in which the coarse adjustment process is not carried out immediately after receiving the second input (including the case in which clicking the coarse adjustment button 107 is used as a trigger, as in the example described above) is preferable insofar as an unnecessary optical adjustment process (movement of the stage S) is not carried out in a case in which an incorrect spot is clicked when the observation surface R is displayed.

[0192] In the example described above, clicking the fine-tuning button 108 after the coarse-tuning process causes processing unit 5 to perform the fine-tuning process; however, the fine-tuning process can be performed automatically after the coarse-tuning process of step S85 is complete. In this case, processing unit 5 can perform the fine-tuning process immediately after the coarse-tuning process is complete or perform the fine-tuning process after a certain period of time. The case where the fine-tuning process is not performed immediately after the coarse-tuning process is complete (including the case where clicking the fine-tuning button 108 is used as a trigger, as in the example described above) is preferable because it allows the user time to check the situation if there is an error in the instructions for the coarse-tuning process (e.g.,(a wrong input of interface information).

[0193] 1, 1A: Interference observation device, 2: Light source, 3: Interference optical system, 4: Image sensor, 5: Processing unit, 8: Object of observation, 13: Objective lens, 15: Reference mirror, 52: Input unit, 53: Display unit, 84 to 88: Multiple layers, 101: First element, 102: Second element, 103: Hint element, 104: Objective lens element, 105: Interference image element, 109: Setting amount display element, 110: Focus lock element, 111: Limit value element, C: Computer, L1: First light, L2: Second light, L3: Interference light, L6: Light, P: Optical setting program, R: Observation surface, S: Stage. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2016-121250

[0003] Cited non-patent literature

[0000] Field Guide to Interferometric Optical Testing” SPIE Press, ISBN 978-0-8194-6410-0, 2006, page 36

[0058] Micropolarizer Array, Phase-Shifting Interferometer” (Reference Literature 1, page 44

[0077] Spatial Synchronous and Fourier Method” (Reference Literature 1, page 43

[0077] Interferogram Analysis for Optical Testing", CRC Press, ISBN 978-0824799403, (2005), page 269

[0078] K. Hibino, B. F. Oreb, D. I. Farrant, and K.G. Larkin, „Phaseshifting for nonsinusoidal waveforms with phase-shift errors,“ J. Opt.Soc. Am. A 12, 761-768 (1995

[0079]

Claims

[1] Interference observation device for observing the interior of an object having a multitude of layers, wherein the device comprises: a light source that emits light; an interference-optical system comprising a movable reference mirror and an objective lens, which splits the light emitted by the light source into a first light and a second light and outputs the interference light of the first light, which is reflected from an observation surface located inside the object being observed, and of the second light, which is reflected from the reference mirror; an image sensor that detects the interference light; an input unit that receives information input; a display unit that shows information; and a processing unit that captures an interference image based on a detection result of the interference light, and that performs an optical adjustment process for an optical adjustment with respect to an observation of the observed object, wherein the input unit receives an initial input representing the thicknesses, refractive indices and the arrangement order of the multitude of layers, The display unit shows a first element that represents values ​​of the thicknesses and refractive indices of the multitude of layers according to the first input, and a second element that graphically represents the multitude of layers in a mode that corresponds to the thicknesses and the arrangement order of the multitude of layers according to the first input. in a state where the display unit shows the first element and the second element, the input unit receives a second input to specify the observation surface from the interfaces between the multitude of layers, and The processing unit performs a first optical adjustment process to set a relative position between the objective lens and the observation object, and a second optical adjustment process to set an optical path length of the second light by moving the reference mirror, based on the thicknesses and refractive indices of the multitude of layers according to the first input, so that the interference pattern of the observation surface is captured according to the second input. [2] Interference monitoring device according to claim 1, wherein the display unit displays the interference pattern captured by the processing unit in addition to the first element and the second element. [3] Interference monitoring device according to claim 1 or 2, wherein the display unit together with the second element displays an element that graphically represents as the second element the interface specified as the observation surface among the interfaces of the plurality of layers. [4] Interference observation device according to one of claims 1 to 3, wherein the display unit together with the second element displays an element for displaying a position of the objective lens at a position that is spaced apart from the plurality of layers, which are graphically represented as the second element, by a distance corresponding to the relative position between the objective lens and the object being observed. [5] Interference monitoring device according to any one of claims 1 to 4, wherein the second input is received from a user who specifies a range within the first element or the second element. [6] Interference monitoring device according to any one of claims 1 to 5, wherein the processing unit performs an additional adjustment process after the first optical adjustment process and the second optical adjustment process, and in the additional adjustment process the processing unit acquires a plurality of interference images in which an optical path length difference between the first light and the second light is made different by changing the optical path length of the second light, and performs the first optical adjustment process and the second optical adjustment process based on the plurality of interference images. [7] Interference monitoring device according to claim 6, further comprising: an object table for arranging the object of observation, wherein the object table is movable at least along a plane that intersects a direction in which the first light falls on the object of observation, the processing unit performs the additional adjustment process in response to a movement of the object table along the plane. [8] Interference monitoring device according to claim 7, wherein the input unit receives a third input to specify whether the additional adjustment process should be performed in response to the movement of the object table along the plane, and The display unit shows an element representing a setting state, indicating whether the additional setting process should be carried out in response to the movement of the object table along the plane based on the third input. [9] Interference monitoring device according to any one of claims 6 to 8, wherein the input unit receives a fourth input to specify a limit value relating to the additional setting process, and The display unit shows an element that represents the limit value according to the fourth input. [10] Interference observation device according to one of claims 6 to 9, wherein the display unit displays an element that represents a relative distance between the objective lens and the observation object and an amount of the optical path length of the second light, which is set in the additional adjustment process. [11] Optical adjustment method for performing an optical adjustment with respect to an observation of an object of observation, comprising a plurality of layers in an interference observation device, which includes a light source emitting light, an interference optical system comprising a movable reference mirror and an objective lens that splits the light emitted by the light source into a first light and a second light, and emits the interference light of the first light, which is reflected from an observation surface located within the object of observation, and of the second light, which is reflected from the reference mirror, an image sensor that detects the interference light, an input unit that receives an information input, and a display unit that displays the information and that captures an interference image based on a detection result of the interference light.the procedure has the following order: , a step of causing the input unit to receive an initial input representing thicknesses, refractive indices and the arrangement order of the multitude of layers; a step of causing the display unit to display a first element that represents values ​​of the thicknesses and refractive indices of the plurality of layers according to the first input, and a second element that graphically represents the plurality of layers in a mode that corresponds to the thicknesses and arrangement order of the plurality of layers according to the first input; a step of causing the input unit to receive a second input to specify the observation surface from the interfaces between the multitude of layers in a state where the display unit shows the first element and the second element; and a step of performing a first optical adjustment process to set a relative position between the objective lens and the observation object and a second optical adjustment process to set an optical path length of the second light by moving the reference mirror, based on the thicknesses and refractive indices of the multitude of layers according to the first input, so that the interference pattern of the observation surface is captured according to the second input. [12] Optical adjustment program for performing an optical adjustment with respect to an observation of an object of observation, which has a plurality of layers in an interference observation device, comprising a light source that emits light, an interference optical system comprising a movable reference mirror and an objective lens that splits the light emitted by the light source into a first light and a second light, and outputs the interference light of the first light, which is reflected from an observation surface located within the object of observation, and of the second light, which is reflected from the reference mirror, an image sensor that detects the interference light, an input unit that receives an information input, and a display unit that displays the information and that captures an interference image based on a detection result of the interference light,wherein the program causes a computer to execute the following in the interference monitoring device in the following order: a process of causing the input unit to receive an initial input representing thicknesses, refractive indices, and the arrangement order of the multitude of layers; a process of causing the display unit to display a first element representing values ​​of the thicknesses and refractive indices of the plurality of layers according to the first input, and a second element graphically representing the plurality of layers in a mode corresponding to the thicknesses and arrangement order of the plurality of layers according to the first input; a process of causing the input unit to receive a second input to specify the observation surface from the interfaces between the multitude of layers in a state where the display unit displays the first element and the second element; and a process of performing a first optical adjustment process to set a relative position between the objective lens and the observation object and a second optical adjustment process to set an optical path length of the second light by moving the reference mirror, based on the thicknesses and refractive indices of the multitude of layers according to the first input, so that the interference pattern of the observation surface is captured according to the second input.

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