INTERFERENCE OBSERVATION DEVICE AND INTERFERENCE OBSERVATION METHOD

Abstract

An interference observation device comprises a light source; an optical interference system comprising a reference mirror that splits the light emitted by the light source into a first light and a second light, and emits interference light between the first light reflected from an object under observation and the second light reflected from the reference mirror; an image sensor that detects the interference light; and a processing unit that acquires an interference image. The optical interference system includes a device configured to change the focus of the second light's beam path.The processing unit separates observation surface information and non-observation surface information based on a multitude of interference images obtained when the focusing of the beam path of the second light is changed in a state where the focal point of the first light is aligned with an observation surface of the observed object.

Description

Technical field

[0001] One aspect of the present invention relates to an interference observation device and an interference observation method. State of the art

[0002] For example, patent literature 1 describes an interference observation device comprising: a light source; an interference optics system that splits the light emitted by the light source into a first branched light and a second branched light, reflects the first branched light from an observation object, 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 captures an interference image based on the detection signal. Citation list for patent literature

[0003] Patent literature 1: International PCT Publication No. WO2016-121250 Summary of the invention; Problem statement

[0004] With the interference observation device described above, if an interface of the observed object is used as the observation surface, for example, if there are scratches or similar marks on another interface, these scratches or similar marks may influence the interference pattern being recorded. In this case, there is a risk that information regarding the observation surface cannot be acquired with high accuracy.

[0005] One objective of the present invention is to provide an interference observation device and an interference observation method with which information relating to an observation surface can be acquired with high accuracy. Solution to the problem

[0006] An interference observation device according to one aspect of the present invention is [1] “an interference observation device comprising: a light source that emits light; an interference optics system comprising a reference mirror that splits the light emitted by the light source into a first light and a second light and emits interference light between the first light reflected by an object being observed and the second light reflected by the reference mirror; an image sensor that detects the interference light; and a processing unit that acquires an interference image based on a detection result from the image sensor. The optical interference system comprises a device configured to change the focus of the beam path of the second light.”The processing unit separates observation surface information, which relates to an observation surface of the observed object, and non-observation surface information, which relates to a non-observation surface other than the observation surface, based on a multitude of interference images obtained when the focusing of the beam path of the second light is changed in a state where a focal point of the first light is aligned with the observation surface.

[0007] As a result of careful investigations, the inventors have found that when the focusing of the second light is changed in a state where the focal point of the first light is aligned with the observation surface of the object being observed, in the several interference patterns obtained, the amount of modulation received by components relating to the non-observation surface, which differs from the observation surface, is significantly larger than the amount of modulation received by components relating to the observation surface.Therefore, in the interference observation device according to one aspect of the present invention, information relating to the observation area (hereinafter also referred to as "observation area information") and information relating to the non-observation area (hereinafter also referred to as "non-observation area information") are separated based on the multiple interference images thus acquired. Accordingly, the observation area information can be selectively obtained by excluding the non-observation area information from the interference image, and the observation area information can be acquired with high accuracy.

[0008] An interference monitoring device according to one aspect of the present invention can be [2] “the interference monitoring device according to [1], wherein the processing unit separates the observation surface information and the non-observation surface information based on a first interference image obtained when the reference mirror is in a first position, and a second interference image obtained when the reference mirror is moved from the first position along the beam path of the second light by a distance equal to or greater than half a wavelength of the light emitted by the light source.” In this case, the observation surface information and the non-observation surface information of the interference image can be separated by moving the reference mirror along the beam path of the second light.

[0009] An interference observation device according to one aspect of the present invention can [3] be “the interference observation device according to [1], wherein the interference optics system comprises a reference objective lens which directs the second light to the reference mirror and is movable, and the processing unit separates the observation surface information and the non-observation surface information on the basis of a first interference image obtained when the reference objective lens is in a first position, and a second interference image obtained when the reference objective lens is moved from the first position along the beam path of the second light by a distance equal to or greater than half a wavelength of the light emitted by the light source”.In this case, the observation surface information and the non-observation surface information of the interference image can be separated by moving the reference objective lens along the path of the second light.

[0010] An interference observation device according to one aspect of the present invention can [4] be “the interference observation device according to [1], wherein the light source comprises a first light source emitting light of a first wavelength and a second light source emitting light of a second wavelength that differs from the first wavelength, the interference optics system comprises a dispersive medium arranged on the beam path of the second light, and the processing unit separates the observation surface information and the non-observation surface information on the basis of a first interference image obtained when the light is emitted from the first light source and a second interference image obtained when the light is emitted from the second light source”.In this case, the observation area information and the non-observation area information can be separated using light of two wavelength types.

[0011] An interference observation device according to one aspect of the present invention can [5] be the interference observation device according to any one of points [1] to [4], wherein the object under observation comprises a device section and a cap section provided over an air gap on a front face of the device section, the interference optics system causing the first light to fall on the object under observation from a side of the cap section, the observation area being the front face of the device section, and the non-observation area comprising a front and a back face of the cap section. In this case, observation area information with respect to the front face of the device section can be acquired with high accuracy, while the influence of the front and back faces of the cap section is suppressed.

[0012] An interference observation device according to one aspect of the present invention can [6] “be the interference observation device according to any one of points [1] to [4], wherein the object being observed comprises a device section and a film section provided on a front side of the device section, the interference optics system causes the first light to fall on the object being observed from a side of the film section, the observation area is the front side or a back side of the device section, and the non-observation area comprises a front side and a back side of the film section.” In this case, observation area information with respect to the front side or the back side of the device section can be acquired with high accuracy, while the influence of the front side and the back side of the film section is suppressed.

[0013] An interference observation device according to one aspect of the present invention can [7] be “the interference observation device according to any one of points [1] to [4], wherein the object under observation comprises a first device section and a second device section provided on a front side of the first device section, the interference optics system causes the first light to fall on the object under observation from a side of the second device section, the observation surface is the front side or a back side of the first device section, and the non-observation surface comprises a front side and a back side of the second device section.” In this case, observation surface information with respect to the front side or the back side of the first device section can be acquired with high accuracy, while the influence of the front side and the back side of the second device section is suppressed.

[0014] An interference observation device according to one aspect of the present invention can be [8] “the interference observation device according to any one of points [1] to [4], wherein the object under observation comprises a device section, the optical interference system causes the first light to fall on the object under observation from a front side of the device section, the observation area is a back side of the device section, and the non-observation area is a front side of the device section.” In this case, observation area information with respect to the back side of the device section can be acquired with high accuracy, while the influence of the front side of the device section is suppressed.

[0015] An interference monitoring device according to one aspect of the present invention can [9] be “the interference monitoring device according to any one of points [1] to [4], wherein the observation surface is an interface of the observation object and the non-observation surface is a front face of an optical element between a detection surface of the image sensor and the observation object.” In this case, observation surface information with respect to the interface of the observation object can be acquired with high accuracy, while the influence of the front face of the optical element between the image sensor and the observation object is suppressed.

[0016] An interference monitoring device according to one aspect of the present invention can be

[10] “the interference monitoring device according to [9], wherein the observation surface is the interface of the object being observed and the non-observation surface is a front surface of a protective plate of the image sensor, the protective plate being located at a distance from the detection surface of the image sensor.” In this case, observation surface information with respect to the interface of the object being observed can be acquired with high accuracy, while the influence of the front surface of the protective plate of the image sensor is suppressed.

[0017] An interference monitoring device according to one aspect of [ ] of the present invention can

[11] be “the interference monitoring device according to any one of points [1] to

[10] , which further comprises: a display unit that displays at least one table showing the positions of a plurality of foreign bodies in the interference image and / or the degree of defocus of each of the plurality of foreign bodies and / or an image showing the distribution of the degrees of defocus in the interference image”. In this case, foreign bodies on the observation surface and foreign bodies on the non-observation surface can be easily distinguished and identified by at least one of the tables and images displayed on the display unit.

[0018] An interference monitoring device according to one aspect of the present invention can

[12] be “the interference monitoring device according to any one of points [1] to

[11] , which further comprises: a storage unit that stores at least one table showing the positions of a plurality of foreign bodies in the interference image and a degree of defocus of each of the plurality of foreign bodies, and an image showing a distribution of the degrees of defocus in the interference image.” In this case, foreign bodies on the observation surface and foreign bodies on the non-observation surface can be easily distinguished and identified by using at least one of the tables and images stored in the storage unit.

[0019] An interference observation method according to one aspect of the present invention is

[13] “an interference observation method comprising: a light output step for outputting light from a light source; an interference light output step for splitting the light output from the light source into a first light and a second light and for outputting interference light between the first light reflected from an object of observation and the second light reflected from a reference mirror; an interference light detection step for detecting the interference light using an image sensor; and a processing step for detecting an interference image based on a detection result from the image sensor.In the processing step, observation surface information relating to an observation surface of the observed object and non-observation surface information relating to a non-observation surface other than the observation surface are separated based on a multitude of interference images obtained when a focusing condition of a beam path of the second light is changed in a state in which a focal point of the first light is aligned with the observation surface.

[0020] In the interference observation method, observation area information can also be selectively obtained by excluding non-observation area information from the interference image, and the observation area information can be recorded with high accuracy. Advantageous effects of the invention

[0021] According to one aspect of the present invention, it is possible to provide the interference observation device and the interference observation method with which information regarding the observation area can be acquired with high accuracy. Brief description of the drawings Fig. 1] Fig. Figure 1 is a configuration view showing an interference monitoring device according to a first embodiment. [ Fig. 2] Fig. Figure 2 is a flowchart that provides an example of the operation of the interference observation device in Fig. 1 shows. [ Fig. 3] Fig. 3(a) is a photograph showing an example of a first phase image. Fig. 3(b) is a photograph showing an example of a second phase image with a reference. [ Fig. 4] Fig. 4(a) is a time diagram showing an example of the operation of a reference mirror. Fig. 4(b) is a time diagram showing another example of the operation of the reference mirror. [ Fig. 5] Fig. 5(a) is a photograph showing an example of a phase image with extracted bright spots. Fig. 5(b) is a photograph showing an example of an image with bright dot positions. [ Fig. 6] Fig. 6(a) is a photograph showing an example of a difference phase image. Fig. 6(b) is a photograph showing an example of a defocus index image. [ Fig. 7] Fig. 7(a) is a photograph showing an example of a focused phase image. Fig. 7(b) is a photograph showing an example of a defocused phase image. [ Fig. 8] Fig. 8 is a view that shows a defocus index table. [ Fig. 9] Fig. Figure 9 is a configuration view showing an interference monitoring device according to a second embodiment. [ Fig. 10] Fig. Figure 10 is a diagram showing the spectral properties of the luminous power emitted by a first light source and a second light source. [ Fig. 11] Fig. Figure 11 is a configuration view showing an interference monitoring device according to a third embodiment. [ Fig. 12] Fig. Figure 12 is a flowchart that provides an example of the operation of the interference observation device in Fig. 11 shows. [ Fig. 13] Fig. 13(a) is a photograph showing an example of a first phase image. Fig. 13(b) is a photograph showing an example of a second phase image. [ Fig. 14] Fig. 14(a) is a photograph showing an example of a differential phase image “ ”. Fig. 14(b) is a view obtained by binarizing the photo into Fig. 13(a) was obtained. [ Fig. 15] Fig. Figure 15 is a view describing the field of view of an imaging device of the interference observation device in Fig. 11. [ Fig. 16] Fig. Figure 16(a) is a cross-sectional view to describe an observed object according to a modification example. Fig. Figure 16(b) is a cross-sectional view to describe an observed object according to a modification example. [ Fig. 17] Fig. Figure 17 is a cross-sectional view to describe an observed object according to a modification example. Description of embodiments

[0022] The following sections describe embodiments in detail with reference to the drawings. In the following description, identical or corresponding elements use the same reference numerals, and duplicate descriptions are omitted. <Erste Ausführungsform> [Setup of an interference monitoring device]

[0023] As in Fig. As shown in Figure 1, an interference observation device 1 according to a first embodiment comprises a light source 2, an interference optics 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 using light interference. The observation object 8 is, for example, a semiconductor device, but can also be other industrial samples made of metal, glass, resin, liquid crystal, 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 1. Fig. 1 shown, fixed.

[0024] The interference observation device 1 is configured to perform both surface observation (observing the front (outer) surface of the observation object 8) and internal observation (observing the interior of the observation object 8). Internal observation involves observing an observation area R located within the observation object 8. In this example, the observation object 8 is a capped semiconductor device comprising a first layer 81, a second layer 82, and a third layer 83.

[0025] The first layer 81 is a layer consisting of at least one semiconductor, glass, and resin, forming a cap section. The second layer 82 is an air layer, also referred to as an air cap. The third layer 83 is a semiconductor layer and forms a component part in which a pattern of functional elements is formed on a wafer. Here, the third layer 83 is a structured chip. The first layer 81 through the third layer 83 are arranged (laminated) in the order of the third layer 83, the second layer 82, and the first layer 81, and the observation object 8 is positioned on the stage S such that the third layer 83 is in contact with the stage S. The first layer 81 is located above the second layer 82 on a front face of the third layer 83. The observation area R is defined at any interface between the first layer 81, the second layer 82, and the third layer 83.Here, the observation surface R is defined at the interface between the second layer 82 and the third layer 83. The observation surface R is located on the front face of the third layer 83. A front face (a surface on the side of the interference optics system 3) and a back face (a surface on the side of the stage S) of the first layer 81 can be mirror-polished surfaces and a ground surface, respectively. The observation surface R can be observed through the first layer 81 using light with a wavelength that passes through the first layer 81, such as the light emitted by the light source 2.

[0026] 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 the like.

[0027] In this example, the interference optics system 3 is configured as a Linnik interference system. The interference optics 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 optical interference 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 predetermined actuator 16. The Z-direction is a direction parallel to the optical axis of the objective lens 13 and a direction parallel to the direction in which a first light L1, to be described later, strikes the observation object 8.

[0028] Lens 11 collimates the light emitted by light source 2. Beam splitter 12, for example, is a prism with an optical surface 12a and 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 outputs 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 the optical surface 12a, and the second light L2, reflected from reference mirror 15, passes through reference objective lens 14 onto the optical surface 12a. The first light L1 and the second light L2 are combined at the optical surface 12a to form an interference light L3. The interference optics system 3 outputs the interference light L3 to the image sensor 4.

[0029] The objective lens 13 focuses the first light L1 emitted by the beam splitter 12 onto the observation object 8 arranged on the table 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 outputs the incident first light L1 to the beam splitter 12.

[0030] 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.

[0031] A stepper motor 17 for moving the reference objective lens 14 and a stepper motor 18 and a piezoelectric element 19 for moving the reference mirror 15 are further arranged within the housing H of the optical module M. 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.

[0032] The response time of stepper motors 17 and 18 is more than 10 ms, while the response time of the piezoelectric element 19 is less than 1 ms. This means that the response time of the piezoelectric element 19 is shorter than the response time of stepper motors 17 and 18. The stroke (minimum travel distance) of stepper motors 17 and 18 is several mm, and the stroke of the piezoelectric element 19 is approximately 10 µm. This means that the stroke of the piezoelectric element 19 is smaller than the stroke of stepper motors 17 and 18. The lifetime of stepper motors 17 and 18 is less than 1 million cycles, while the lifetime of the piezoelectric element 19 is more than 10 billion cycles. This means that the lifetime of the piezoelectric element 19 is longer than the lifetime of stepper motors 17 and 18.

[0033] 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 (captures an image) the interference light L3 emitted by the interference optics system 3 (the beam splitter 12). A lens 41 and an objective tube 42 are arranged between the image sensor 4 and the interference optics system 3. The lens 41 forms an image of the interference light L3 emitted by the interference optics system 3 onto an image-receiving area of ​​the image sensor 4. The lens 41 is housed in the objective tube 42. The objective tube 42 is, for example, cylindrical in shape and attached to the image sensor 4 to surround the image-receiving area.

[0034] The processing unit 5 is connected to each part of the interference observation device 1, including the light source 2, the interference optics system 3, the image sensor 4, and the stage S, and acquires an interference image based on the acquisition result of the interference light L3 in the image sensor 4. The interference image includes, for example, a phase image, an amplitude image, a complex image, various images to be described later, and an image corresponding to one of these images.

[0035] The processing unit 5 is configured, for example, by a computer C, which includes a processor (CPU) and RAM and ROM memory. The computer C includes a memory area (memory unit) 51 that stores various information, an input unit 52 that accepts input of various information, and a display unit 53 that displays various information. The input unit 52 is, for example, a device that accepts 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 together as a touch panel and, in this case, configured as a graphical user interface (GUI).Furthermore, in this example, the processing unit 5, the memory area 51, the input unit 52 and the display unit 53 are configured as one device; however, at least one of them can be configured as a separate device, for example as a mobile device or the like.

[0036] Stage S is a platform for positioning the observation object 8 and is movable along an XY plane perpendicular to the Z direction, in which the first light L1 strikes the observation object 8. Accordingly, in the interference observation device 1, the observation surface R of the observation object 8 can be observed (an interference image can be captured) while stage S is moved along the XY plane, i.e., while the observation position of the observation object 8 is changed.

[0037] In the interference observation device 1, incoherent light is first emitted from the light source 2 (light output step). The light is collimated by the lens 11 and split into the first light L1 and the second light L2 by the beam splitter 12. The first light L1 is focused by the objective lens 13 onto the observation object 8, reflected at the interface of the observation object 8, and introduced into the beam splitter 12 via the objective lens 13. The second light L2 is focused by the reference objective lens 14 onto the reference mirror 15, reflected by the reference mirror 15, and introduced into the beam splitter 12 via the reference objective lens 14. The beam splitter 12 combines the introduced first light L1 and the introduced second light L2 and emits interference light (interference light output step). The emitted interference light is detected by the image sensor 4 (interference light detection step).The processing unit 5 captures an interference image based on the acquisition result of the image sensor 4 (processing step).

[0038] Furthermore, the image sensor 4 in the interference observation device 1 performs imaging to capture four interference images, and the processing unit 5 constructs (captures) an interference image based on the four captured interference images. The piezoelectric element 19 moves the reference mirror 15 precisely according to the imaging time of the 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. The amount of movement of the reference mirror 15 to capture the four interference images is less than one wavelength λl of the light emitted by the light source 2. In this example, the optical path length difference (phase shift interval) of the second light L2 among the four interference images is λ / 4.If the reference mirror 15 is moved so finely that the change in optical path length is λ / 4, taking into account that the second light L2 (hereinafter also referred to as the "reference light") moves back and forth along an optical path of the second light L2 (hereinafter also referred to as the "reference optical path"), the actual movement step of the reference mirror 15 becomes λ / 8, and, for example, in the case of λ = 532 nm, the value of the actual movement step is 66.5 nm. The method for acquiring interference images is not limited to the method described in the example above, but can be any of the various known methods.

[0039] In the present embodiment, the processing unit 5 separates observation surface information relating to the observation surface R and non-observation surface information relating to a non-observation surface other than the observation surface R, based on a plurality of interference images obtained when the focusing of the beam path of the second light L2 is changed in a state where the focal point of the first light L1 is aligned with the observation surface R of the observed object 8. In other words, in the processing step, the observation surface information and the non-observation surface information are separated based on the multiple interference images obtained when the focusing of the beam path of the second light L2 is changed in a state where the focal point of the first light L1 is aligned with the observation surface R.Here, the processing unit 5 includes a control unit that controls the piezoelectric element 19 so that it moves the reference mirror 15 along the beam path of the second light L2, thereby changing the focus of the beam path of the second light L2. The piezoelectric element 19 and the mechanism that allows the reference mirror 15 to move along the beam path of the second light L2 by means of the piezoelectric element 19 form a device configured to change the focal point of the beam path of the second light L2.

[0040] The processing unit 5 separates the observation surface information and the non-observation surface information based on a first phase image (first interference image) obtained when the reference mirror 15 is in a first position, and a first phase image (second interference image) obtained when the reference mirror 15 is moved from the first position along the beam path of the second light L2 by a distance equal to or greater than half the wavelength (λ / 2) of the light emitted by the light source 2 (details are described later). [Example of the operation of an interference monitoring device]

[0041] Next, with reference to Fig. 2. An interference observation method using the interference observation device 1 is described. In one of the following examples, the observation area R is observed inside the observation object 8 (observed through the cap). The interference optics system 3 causes the first light L1 to fall onto the observation object 8 from the side of the first layer 81. The observation area R is the front side of the third layer 83. The non-observation area comprises the front and back sides of the first layer 81.

[0042] First, the processing unit 5 controls the actuator 16 to move the objective lens 13 along the Z-direction and adjust its position relative to the observation object 8 so that the focal point (focus position) of the objective lens 13 is aligned with the observation surface R. Specifically, the position of the objective lens 13 is adjusted so that the observation surface R and a light-receiving surface of the image sensor 4 are optically conjugate through optical imaging by the objective lens 13 and the lens 41. The processing unit 5 controls the piezoelectric element 19 to move the reference mirror 15 to a forward position. The forward position is, for example, the first position near the reference objective lens 14. The image sensor 4 detects and records four interference images. The processing unit 5 constructs (detects) a first phase image K1, which is then Fig. 3(a) is shown as a phase image, based on the four captured interference images (step S1).

[0043] If the four captured interference patterns are designated in succession as Img1, Img2, Img3 and Img4, a phase pattern Φ can be calculated by the following equation (F1). Φ=Atan2((Img1−Img3) / (Img4−Img2)).

[0044] In addition to the equation shown here for calculating a phase image, many types of algorithms for calculating a phase image from one or more interference images are widely known and can be applied to the method of the present embodiment. Incidentally, a background distortion may remain in the phase image Φ obtained here; however, this background distortion can be corrected by polynomial approximation or the like.

[0045] Furthermore, a complex amplitude image E, in which the pixel values ​​are complex numbers, can be computed as an image that retains the information about both the phase and amplitude components contained in the four interference images, and then used in subsequent processing. The complex amplitude image E can be computed by the following equation (F2). E=(Img4−Img2)+i(Img1−Img3)

[0046] This is a complex unit.

[0047] The processing unit 5 then controls the piezoelectric element 19 to move the reference mirror 15 from its front position to a rear position, for example by 4 µm. Accordingly, the focal condition of the beam path of the second light L2 is changed. The rear position is, for example, a second position that is further away from the reference objective lens 14 than the front position. The image sensor 4 detects and records four interference images. The processing unit 5 constructs (detects) a second phase image K2, which is then processed. Fig. 3(b) is shown as a phase image based on the four captured interference images (step S2).

[0048] Fig. 4(a) and Fig. 4(b) are time diagrams showing an operating mode of the reference mirror 15. Fig. Figure 4(a) shows a time diagram for a case in which the reference mirror 15 is in the front position and four interference images are acquired, and then the reference mirror 15 is in the rear position and four interference images are acquired. When the four interference images are acquired at each position, the reference mirror 15 moves finely with a step size of λ / 8, as described above; however, the amount of fine movement is significantly smaller than the amount of movement between the front and rear positions, for example, 4 µm, and the change in focus on the reference optics side during the acquisition of the four successive interference images is negligible.

[0049] Furthermore, with regard to the temporal sequence between the acquisition of an interference image in a state in which the reference mirror 15 is in the front position and the acquisition of an interference image in a state in which the reference mirror 15 is in the rear position, either the former or the latter can be performed first. Fig. Figure 4(b) shows a time diagram for a case in which the reference mirror 15 is in the rear position and interference images are taken, and then the reference mirror 15 is in the front position and interference images are taken.

[0050] As a movement mechanism for the reference mirror 15 to switch the reference mirror 15 between the front position and the rear position, the stepper motor 18 can be used instead of the piezoelectric element 19. In this case, too, the position of the reference mirror 15 can be, for example, set according to the Fig. The timing diagram shown in Figure 4(a) is controlled. However, between the piezoelectric element 19 and the stepper motor 18, the piezoelectric element 19 has a longer lifetime in terms of the number of reversing movements, and therefore, from the point of view of the lifetime of the device, it is preferable that the piezoelectric element 19 be used to switch the reference mirror 15 between the front position and the rear position.

[0051] Subsequently, processing unit 5 extracts a bright point-extracted phase image K3 from the first phase image K1 and the second phase image K2, which is then Fig. 5(a) is shown (step S3). The bright-point extracted phase image K3 is a phase image obtained by performing threshold processing, which is a known procedure, on an average image of the first phase image K1 and the second phase image K2 to extract only bright points equal to or greater than a threshold. Fig. 5(a) darkness corresponds to luminance, and the horizontal axis and the vertical axis each correspond to an X-coordinate position and a Y-coordinate position (the same applies to Fig. 6(a) to 7(b)). Incidentally, instead of extracting bright areas using the average image of the first phase image K1 and the second phase image K2, either the first phase image K1 or the second phase image K2 can be used.

[0052] The processing unit then extracts 5 bright spot areas from the bright spot-extracted phase image K3 and acquires a bright spot position image I1, which is displayed in Fig. 5(b) is shown (step S4). The bright spot position image I1 is an image showing the bright spot areas of the bright spot-extracted phase image K3. The bright spot position image I1 is an image obtained by performing threshold processing on the bright spot-extracted phase image K3 to binarize the bright spot-extracted phase image K3, and subsequently by performing a labeling process, which is a known method, to extract the bright spot areas of the bright spot-extracted phase image K3. In Fig. 5(b) the horizontal axis and the vertical axis correspond to an X-coordinate position and a Y-coordinate position, respectively.

[0053] The processing unit 5 then calculates a difference between the first phase image K1 and the second phase image K2 and obtains a value in Fig. 6(a) difference phase image K4 shown (step S5). In step S5, if the difference phase image K4 is denoted as ΔΦ(x, y), the first phase image K1 is denoted as Φ1(x, y) and the second phase image K2 is denoted as Φ2(x, y), the difference phase image K4 is expressed as ΔΦ(x, y) = Abs(Φ2(x, y) - Φ1(x, y)).

[0054] Subsequently, processing unit 5 calculates a distribution of the defocus levels of the differential phase image K4 and acquires a defocus index image I2, which is displayed in Fig. Figure 6(b) is shown as an image representing the degree of defocus (step S6). In step S6, the following processing is performed for each bright spot region shown in the bright spot position image I1. First, an average luminance Qa in the bright spot region of the first phase image K1 is obtained. An average luminance Qb in the bright spot region of the second phase image K2 is obtained. The following equation (1) is calculated to obtain the degree of defocus as an index of the difference. That is, a coefficient of variation is obtained by dividing the magnitude of the luminance variation by the average value. This processing is performed for all bright spot regions in the field of view of the differential phase image K4, and the results are used as the degree of defocus for each bright spot region in the differential phase image K4.The degree of defocus is an index for the degree of defocusing and corresponds to the degree to which an image is blurry. Degree of defocus=Abs(Qa−Qb) / (0.5×(Qa+Qb))

[0055] If the phase image recorded by the image sensor 4 with the reference mirror 15 moved to the front position is called Φ1(x, y) and the phase image recorded by the image sensor 4 with the reference mirror 15 moved to the rear position is called Φ2(x, y), the above equation (1) can be rewritten as equation (2) as follows. Defocus level = Abs(Average value in the bright area of ​​Φ(x,y) / Average value in the bright area of ​​Φave(x,y))

[0056] This applies here ΔΦ(x,y)=Φ2(x,y)−Φ1(x,y), Φave=0.5×(Φ2(x,y)+Φ1(x,y)

[0057] Subsequently, processing unit 5 refers to the defocusing index image I2 based on the bright-point extracted phase image K3 and separately acquires a focused phase image K10 (see Fig. 7(a)), which corresponds to the components in the bright-point extracted phase image K3 whose degree of defocusing is less than a predetermined value, and an out-of-focus phase image K20 (see Fig. 7(b)), which corresponds to the components in the phase image K3 with extracted bright points and whose degree of defocusing is equal to or greater than the predetermined value (step S7).

[0058] The focused phase image K10 is observation surface information. It represents information within the focal depth of the first light L1. The focused phase image K10 corresponds to an image showing only components related to the observation surface R in the bright spot-extracted phase image K3. For example, the focused phase image K10 is an image obtained by extracting the areas in the bright spot-extracted phase image K3 whose degree of defocus is less than a predetermined value, with reference to the defocus index image I2. The defocused phase image K20 is non-observation surface information. It contains information outside the focal depth of the first light L1. The defocused phase image K20 corresponds to an image showing only components related to the non-observation surface in the bright spot-extracted phase image K3.For example, the blurred phase image K20 is an image obtained by extracting the areas in the bright phase image K3 extracted from the point whose degree of defocus is equal to or greater than the predefined value, with reference to the defocus index image I2. The predefined value is a predetermined value, is not particularly restricted, and can be a value that can be changed by user input. The predefined value is, for example, 0.05. [Measures and impacts]

[0059] As a result of careful investigations, the inventors have determined that when the focusing of the beam path of the second light L2 is changed to a state in which the focal point of the first light L1 is aligned with the observation surface R of the object 8, the amount of modulation received by the components relating to the non-observation surface (i.e., not the observation surface R) in the multiple captured interference images is significantly greater than the amount of modulation received by the components relating to the observation surface R. Therefore, in the interference observation device 1 and the interference observation method, the focused phase image K10 and the defocused phase image K20 are separated based on the multiple interference images captured in this manner.Since, for example, the focused phase image K10 can be selectively obtained by excluding the defocused phase image K20, which reflects cut marks, dirt, dust, or the like on the non-observation surface, from the bright-spot-extracted phase image K3, the focused phase image K10 can be acquired with high accuracy. It is possible to remove the information about the non-observed surface and obtain only the information about the observed surface without making any changes to the optical system from the observation object 8 to the image sensor 4 (without moving the optical module M of the observation sensor or the observation object 8 up and down).

[0060] The interference observation device 1 and the interference observation method separate the focused phase image K10 and the defocused phase image K20 based on the first phase image K1, which is obtained when the reference mirror 15 is in the front position, and the second phase image K2, which is obtained when the reference mirror 15 is moved by a distance equal to or greater than half the wavelength (λ / 2) to be in the back position, and in this case the focused phase image K10 and the defocused phase image K20 can be separated by moving the reference mirror 15 along the beam path of the second light L2.

[0061] In the interference observation device 1 and the interference observation method, the observation area R is the front of the third layer 83, and the non-observation area comprises the front and back of the first layer 81. In this case, the focused phase image K10, which relates to the front of the third layer 83, which is a device section, can be captured with high accuracy, while the influence of the front and back of the first layer 81, which is a cover part, is suppressed. [Other configurations of the interference monitoring device]

[0062] Memory area 51 stores at least one of the acquired images, namely the first phase image K1, the second phase image K2, image K3 with extracted bright spots, the difference phase image K4, the focused phase image K10, the defocused phase image K20, image I1 with the positions of the bright spots, and image I2 with the defocus index. In this case, foreign bodies on the observation area R and foreign bodies on the non-observation area can be easily distinguished and identified by image processing using each image stored in memory area 51.

[0063] The display unit 53 shows at least one of the acquired images, namely the first phase image K1, the second phase image K2, the bright-point extracted phase image K3, the differential phase image K4, the focused phase image K10, the defocused phase image K20, the bright-point position image I1, and the defocus index image I2. In this case, foreign bodies on the observation surface R and foreign bodies on the non-observation surface can be easily distinguished and identified based on the individual images displayed on the display unit 53.

[0064] Processing unit 5 generates a Fig. Figure 8 shows the defocus index table Tb, based on the bright-point extracted phase image K3 and the bright-point position image I1. The defocus index table Tb is a table that shows the positions of a multitude of foreign objects in the bright-point extracted phase image K3 and the degree of defocus for each of these foreign objects. The "Area" in the defocus index table Tb is the area of ​​a bright spot region corresponding to each foreign object in the bright spot-extracted phase image K3. The "Volume" in the defocus index table Tb is a value obtained by integrating the phase values ​​of the pixels contained within each bright spot region corresponding to each foreign object in the bright spot-extracted phase image K3 over the entire area. For example, the "volume" of a bright spot area spanning 2 x 2 pixels and having a phase value of 3 [radians] is 2 × 2 × 3 = 12 [radians · pixels (2) ] The unit can be expressed in [radian · µm (2 )] can be converted or using the proportional relationship between the thickness of the foreign body and the phase value in [µm (3 ) ] be converted.

[0065] Memory area 51 stores the defocus index table Tb. In this case, foreign objects on the observation area R and foreign objects on the non-observation area can be easily distinguished and identified by using the defocus index table Tb stored in memory area 51. Display unit 53 displays the defocus index table Tb. In this case, foreign objects on the observation area R and foreign objects on the non-observation area can be easily distinguished and identified using the defocus index table Tb displayed on display unit 53. <Zweite Ausführungsform>

[0066] Next, a second embodiment is described. The description of the second embodiment details the differences from the first embodiment, omitting any duplicate descriptions.

[0067] As in Fig. As shown in Figure 9, an interference observation device 101 according to the second embodiment differs from that of the first embodiment in that, instead of moving the reference mirror 15 to change the focus of the beam path of the second light L2, light of two different wavelengths is used. The interference observation device 101 differs from that of the first embodiment in that the light source 2 comprises a first light source 2X and a second light source 2Y, and the interference observation device 101 further comprises a dispersive medium 116 on the beam path of the second light L2.

[0068] The first light source 2X emits light of a first wavelength λ1. The second light source 2Y emits light of a second wavelength λ2, which is greater than the first wavelength λ1. As in Fig. As shown in Figure 10, the light from the first light source 2X has a spectral characteristic Sx, where the spectral intensity reaches its maximum at the first wavelength λ1, and the light from the second light source 2Y has a spectral characteristic Sy, where the spectral intensity reaches its maximum at the second wavelength λ2. The first light source 2X and the second light source 2Y emit essentially monochromatic light. The light is selectively emitted from one of the first light source 2X and the second light source 2Y and introduced into the interference optics system 3 via a dichroic mirror 112.

[0069] The dispersive medium 116 is arranged in the beam path of the second light L2 between the beam splitter 12 and the reference mirror 15, more precisely in the beam path of the second light L2 between the reference objective lens 14 and the reference mirror 15. The dispersive medium 116 changes the focus position of the second light L2 depending on the wavelength of the light from one of the first light sources 2X and the second light source 2Y.

[0070] In the interference observation device 101, in step S1, the first phase image K1 is acquired by emitting light from the first light source 2X and not emitting any light from the second light source 2Y. In step S2, the second phase image K2 is acquired by emitting light from the second light source 2Y and not emitting any light from the first light source 2X, without changing the position of the reference mirror 15 (without moving the reference mirror 15). In this way, in the interference observation device 101, the focused phase image K10 and the defocused phase image K20 can be acquired separately by simply switching the light-emitting light source 2 between the first light source 2X and the second light source 2Y, without moving the reference objective lens 14 or the reference mirror 15.

[0071] As described above, the focused phase image K10 can also be acquired with high measurement accuracy in the interference monitoring device 101. Furthermore, the interference monitoring device 101 can separate the focused phase image K10 and the defocused phase image K20 using light of two wavelengths. Since the relationship between the optical thickness OT of the foreign body and a phase Φ OT = λΦ / 2π is given by the formula, the apparent phase difference due to the wavelength difference can be normalized by a factor that is the inverse of the wavelength. In the present embodiment, the first and second light sources 2X and 2Y and the dispersive medium 116 form a device configured to change the focal point of the beam path of the second light L2. <Dritte Ausführungsform>

[0072] Next, a third embodiment is described. The description of the third embodiment details the differences from the first embodiment, omitting any duplicate descriptions.

[0073] As in Fig. As shown in Figure 11, an interference monitoring device 201 according to the third embodiment differs from that of the first embodiment in that, when a single-plate wafer or the like is used as the observation object 208, a front face (incident surface) of the observation object 208 is defined as the observation surface R, and a front face 4R (a surface on the side of the observation object 208) of a protective plate 43, which is mounted at a distance from a detection surface 4D of the image sensor 4, is defined as a non-observation surface, the following processing is carried out by the processing unit 5. The protective plate 43 is mounted in front of the detection surface 4D, which detects light, in the image sensor 4, which is normally used in industrial metrology. The protective plate 43 is made of a transparent material.The protective plate 43 is designed to prevent foreign matter (dust, dirt, or the like) from adhering to the detection surface 4D. The distance between the detection surface 4D and the protective plate 43 is designed such that the detection surface 4D and the protective plate 43 are typically spaced approximately 1 mm to 5 mm apart. In a recorded interference image, foreign matter adhering to the front surface 4R of the protective plate 43 appears slightly blurred; nevertheless, the foreign matter interferes with the quantitative image analysis.

[0074] First, processing unit 5 controls, as in Fig. Figure 12 shows the piezoelectric element 19, used to move the reference mirror 15 into the forward position. The image sensor 4 detects and records four interference images. The processing unit 5 creates (detects) a first phase image K11, which is displayed in Fig. 13(a) is shown, based on the four interference patterns captured (step S11).

[0075] The processing unit 5 then controls the piezoelectric element 19 to move the reference mirror 15, for example, by 3 µm from the front position to the rear position. Accordingly, the focal condition of the beam path of the second light L2 is changed. The image sensor 4 detects and records four interference images. The processing unit 5 creates (detects) a second phase image K12, which is displayed in Fig. 13(b) is shown, based on the four captured interference patterns (step S12).

[0076] The processing unit 5 then calculates a difference between the first phase image K11 and the second phase image K12 and acquires a differential phase image (step S13). Processing unit 5 extracts pixels with a luminance equal to or greater than a threshold value from the differential phase image (step S14). Accordingly, the original differential phase image from which the pixels are extracted is defined as a sharp phase image, and a differential phase image corresponding to the extracted pixels is defined as a blurred phase image. The sharp phase image and the blurred phase image are thus acquired separately (step S15).

[0077] Incidentally, processing unit 5 can be entered after step S13. Fig. The differential phase image K13 shown in 14(a) is captured by enhancing the contrast of the captured differential phase image. The processing unit 5 can be in Fig. The differential phase image K14 shown in Figure 14(b) is acquired by performing a binarization process on the differential phase image K13. Accordingly, the differential phase image K14 can be separated as a fuzzy phase image that clearly shows foreign matter such as dust on the front face 4R of the protective plate 43.

[0078] As described above, the focused phase image can also be acquired with high accuracy in the interference observation device 201. Furthermore, the interference observation device 201 can acquire the focused phase image of the observation object 208 with high accuracy while simultaneously suppressing the influence of the front face 4R of the protective plate 43 of the image sensor 4.

[0079] Incidentally, in the present embodiment, the blurred phase image relating to foreign bodies on the front surface 4R of the protective plate 43 of the image sensor 4 can be used as follows. That is, several phase images are acquired by taking pictures of the observation object 208 while the table S is moved along the XY plane. Calibration is performed by subtracting a blurred phase image from each of the several acquired phase images. In particular, during calibration, a foreign body that overlaps with a foreign body in the differential phase image K14 (a foreign body on the front surface 4R of the protective plate 43) is not counted as a foreign body. As, for example, in Fig. As shown in Figure 15, for a point in a phase image of a particular viewing field V2 that overlaps with a foreign body Q on the front 4R of the protective plate 43, a phase image of another viewing field V1 or viewing field V3 is used in which the point does not overlap with the foreign body Q on the front 4R of the protective plate 43.

[0080] Furthermore, similar to the detection of foreign bodies on the front surface 4R of the protective plate 43 of the image sensor 4, foreign bodies can be detected on the front surface (any surface) of an optical element located between the detection area 4D of the image sensor 4 and the objective lens 13. The front surface of the optical element can be the front surface of the beam splitter 12 or the front surface of the lens 41 in the objective tube 42. In these cases as well, the focused phase image and the defocused phase image can be distinguished by the difference between the phase image detected at the front position of the reference mirror 15 and the phase image detected at the rear position of the reference mirror 15. <modifikationsbeispiele>

[0081] In the embodiments described above, the focus state of the beam path of the second light L2 is changed by moving the reference mirror 15; however, instead of or in addition to this configuration, the focus state of the beam path of the second light L2 can be changed by moving the reference objective lens 14. In this case, the processing unit 5 can create the first phase image based on a plurality of interference images acquired by the image sensor 4 in a state where the processing unit 5 controls the stepper motor 17 to move the reference objective lens 14 to the forward position. The processing unit 5 can create the second phase image based on a plurality of interference images acquired by the image sensor 4 in a state where the processing unit 5 controls the stepper motor 17 to move the reference objective lens 14 to the rear position.Furthermore, the processing unit 5 can separate the observation area information and the non-observation area information based on the first and second phase images. In this case, the stepper motor 17 and the mechanism that allows the reference objective lens 14 to move along the beam path of the second light L2 by means of the stepper motor 17 form a device configured to change the focal point of the beam path of the second light L2.

[0082] In the embodiments described above, various objects can be used as observation objects instead of the observation objects 8 and 208. For example, a Fig. The observation object 308 shown in Figure 16(a) is used as the observation object. The observation object 308 is a so-called film-coated wafer. The observation object 308 comprises a device section 310, which forms a structured chip, and a film section 311, which is provided on a front side of the device section 310. The interference optics system 3 causes the first light L1 to fall onto the observation object 308 from the side of the film section 311. The observation area R is a front side 310a of the device section 310, and the non-observation area comprises a front side 311a and a back side 311b of the film section 311.

[0083] In this case, a focused phase image with respect to the front 310a of the device section 310 can be acquired with high accuracy, while the influence of the front 311a and the back 311b of the film section 311 is suppressed. Incidentally, the observation area R can be a back 310b of the device section 310.

[0084] Furthermore, for example, an in Fig. The observation object 408 shown in Figure 16(b) is used as the observation object. The observation object 408 is a so-called bonded wafer. The observation object 408 comprises a first device section 410 and a second device section 411, which is provided on a front face of the first device section 410. The interference optics system 3 causes the first light L1 to fall onto the observation object 408 from the side of the second device section 411. The observation area R is a front face 410a of the first device section 410. The non-observation area comprises a front face 411a and a back face 411b of the second device section 411.

[0085] In this case, a focused phase image with respect to the front 410a of the first instrument section 410 can be acquired with high accuracy, while the influence of the front 411a and the back 411b of the second instrument section 411 is suppressed. Incidentally, the observation area R can be a back 410b of the first instrument section 410.

[0086] Furthermore, for example, an in Fig. The observation object 508 shown in Figure 17 can be used as the observation object. The observation object 508 is a so-called single-plate wafer. The observation object 508 comprises a device section 510 with a plate shape. The interference optics system 3 causes the first light L1 from a front surface 510 of the device section 510 to strike the observation object 508. The observation surface R is a back surface 510b of the device section 510, and the non-observation surface is a front surface 510a of the device section 510. In this case, a focused phase image relating to the back surface 510b of the device section 510 can be acquired with high accuracy, while the influence of the front surface 510a of the device section 510 is suppressed.

[0087] In the embodiments 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 of or in addition to this configuration, the relative position can be adjusted by moving the stage S along the Z-direction. In this case, the stage S is configured 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 only needs to 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 with respect 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 a servo motor.

[0088] In the embodiments described above, the optical interference system 3 is configured as a Linnik interference type; however, the optical interference system 3 can also be configured as a Michelson interference type or a Mirau interference type. The reference objective lens 14 can be omitted. In the embodiments described above, the method for acquiring the first phase images K1 and K11 and the second phase images K2 and K12 is not limited to the method described above, and various known methods can be used. In the embodiments described above, the number of interference images used to create the first phase images K1 and K11 and the second phase images K2 and K12 is not particularly limited and can be one or more.In the embodiments described above, the distance between the observation surface R and the non-observation surface is limited; however, it is desirable that the distance be, for example, equal to or greater than the focal length of the lens 13.

[0089] In the embodiments described above, the observation area information is not limited to the focused phase image, but can also include other information relating to the observation area. Similarly, in the embodiments described above, the non-observation area information is not limited to the defocused phase image, but can also include other information relating to the non-observation area.

[0090] Each configuration in the embodiments and modification examples described above is not limited to the materials and shapes described above, and various materials and shapes can be used. Furthermore, each configuration in the embodiments and modification examples described above can be applied to any configuration in other embodiments or modification examples. List of reference symbols 1, 101, 201 Interference observation device, 2 light sources, 2X first light source (mechanism for changing focus), 2Y second light source (mechanism for changing focus), 3 Interference optics system, 4 image sensors, 4R Front of the protective plate, 5 processing units, 8, 208, 308, 408, 508 Object of observation, 14 Reference lens, 15 reference mirrors, 17 Stepper motor (mechanism for changing focus), 18 stepper motor (mechanism for changing focus), 19 piezoelectric element (mechanism for changing focus), 43 Protective plate, 51 Storage area (storage unit), 53 Display unit, 81 first layer (covering section), 82 second layer (air layer), 83 third layer (equipment section), 116 dispersive medium (mechanism for changing focus), 310 Equipment section, 311 film segment, 410 first section of the device, 411 second device section, 510 Device section, I2 defocus index image, L1 first light, L2 second light, L3 interference light, K1, K11 first phase image (first interference image), K2, K12 second phase image (second interference image), K10 focused phase image, K20 defocused phase image, R observation area, Tb Defocusing Index Table. 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] < / modifikationsbeispiele>

Claims

[1] An interference monitoring device comprising: a light source that emits light; an optical interference system comprising a reference mirror, which splits the light emitted by the light source into a first light and a second light and emits interference light between the first light reflected by an object being observed and the second light reflected by the reference mirror; an image sensor that captures the interference light; and a processing unit that captures an interference image based on a recording result from the image sensor, wherein the optical interference system comprises a device configured to change a focusing condition of a beam path of the second light, and The processing unit separates observation surface information relating to an observation surface of the observed object and non-observation surface information relating to a non-observation surface that is a surface other than the observation surface, based on a multitude of interference images obtained when the focusing condition of the beam path of the second light is changed in a state in which a focal point of the first light is aligned with the observation surface. [2] Interference observation device according to claim 1, wherein the processing unit separates the observation surface information and the non-observation surface information on the basis of a first interference image obtained when the reference mirror is in a first position and a second interference image obtained when the reference mirror is moved along the beam path of the second light by a distance equal to or greater than half a wavelength of the light emitted by the light source. [3] Interference monitoring device according to claim 1, wherein the interference optics system comprises a reference objective lens which directs the second light to the reference mirror and is movable, and The processing unit separates the observation surface information and the non-observation surface information based on a first interference image obtained when the reference objective lens is in a first position, and a second interference image obtained when the reference objective lens is moved from the first position along the beam path of the second light by a distance equal to or greater than half a wavelength of the light emitted by the light source. [4] Interference monitoring device according to claim 1, wherein the light source comprises a first light source that emits light of a first wavelength and a second light source that emits light of a second wavelength that differs from the first wavelength, the interference optics system comprises a dispersive medium that is arranged on the beam path of the second light, and The processing unit separates the information about the observation area and the information about the non-observation area based on a first interference image obtained when light is emitted from the first light source and a second interference image obtained when light is emitted from the second light source. [5] Interference monitoring device according to claim 1, wherein the object under observation comprises a device section and a cap section which is provided over an air layer on a front side of the device section, the interference optics system causes the first light to fall onto the observation object from one side of the cap, the observation area is the front of the device section and The non-observation area comprises a front and a back side of the cap section. [6] Interference monitoring device according to claim 1, wherein the object of observation comprises a device section and a film section provided on a front side of the device section, The interference optics system causes the first light from one side of the film section to fall onto the object being observed. the observation area is the front surface or a rear surface of the device section and The non-observation area comprises a front and a back of the film section. [7] Interference monitoring device according to claim 1, wherein the object of observation comprises a first device section and a second device section, which are provided on a front side of the first device section, The interference optics system causes the first light to fall onto the object being observed from a second side of the device section. the observation area is the front or back of the first device section, and The non-observation area comprises a front and a back of the second device section. [8] Interference monitoring device according to claim 1, where the object of observation comprises a section of the device, The interference optics system causes the first light to fall onto the observation object from a front side of the device section. the observation area is a back side of the device section and The non-observation area is the front side of the device section. [9] Interference monitoring device according to claim 1, where the observation surface is a boundary surface of the observed object and The non-observation area is the front face of an optical element between a detection surface of the image sensor and the object being observed. [10] Interference monitoring device according to claim 9, where the observation surface is the boundary surface of the observed object and The non-observation surface is a front surface of a protective plate of the image sensor, wherein the protective plate is located at a distance from the detection surface of the image sensor. [11] Interference monitoring device according to claim 1, further comprising: a display unit that displays at least one table showing the positions of a plurality of foreign bodies in the interference image and / or a degree of defocus of each of the plurality of foreign bodies and / or an image showing a distribution of the degrees of defocus in the interference image. [12] Interference monitoring device according to claim 1, further comprising: a storage unit that stores at least one table containing the positions of a plurality of foreign bodies in the interference image and / or a degree of defocus of each of the plurality of foreign bodies and / or an image with a distribution of the degrees of defocus in the interference image. [13] An interference observation method, comprising: a light emission step in which light is emitted from a light source; an interference light output step for splitting the light emitted by the light source into a first light and a second light and for outputting interference light between the first light, which is reflected by an observation object, and the second light, which is reflected by a reference mirror; an interference light detection step for capturing the interference light using an image sensor; and a processing step to capture an interference pattern based on a detection result from the image sensor, wherein in the processing step observation surface information relating to an observation surface of the observed object and non-observation surface information relating to a non-observation surface other than the observation surface are separated on the basis of a plurality of interference images obtained when a focusing condition of a beam path of the second light is changed in a state in which a focal point of the first light is aligned with the observation surface.

Images