Shape measuring device

Abstract

To provide a shape measuring device that can measure a shape of a plate-like object to be measured, especially a notch part of a wafer with a complex shape, with higher accuracy.SOLUTION: A shape measuring device for acquiring a plurality of surface images while scanning a surface of a plate-like object 1 to be measured, and measuring a shape of the object 1 to be measured, includes: an imaging system 10 that irradiates the object 1 to be measured with parallel light and acquires the surface images; a stage system 30 that holds the object 1 to be measured and adjusts an attitude of the object 1 to be measured with respect to the imaging system 10; and a controller 20. The controller 20 includes: an attitude adjustment unit 21 that controls the imaging system 10 and the stage system 30 to scan the surface while adjusting the attitude and acquire the plurality of surface images; and an image processing unit 22 that generates a restored model of the three-dimensional shape of the object 1 to be measured from the plurality of acquired surface images. The attitude adjustment unit 21 adjusts the attitude so that an angle of incidence of the parallel light on the surface falls within a predetermined range when acquiring the surface images.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus for measuring the shape of the surface and chamfered edge of a plate-shaped object to be measured, particularly a semiconductor wafer (hereinafter simply referred to as a "wafer"), and more particularly to a shape measuring apparatus for measuring the three-dimensional shape of a notch portion. [Background technology]

[0002] There is a demand for measuring the edge profile of semiconductor wafers manufactured through processes such as grinding, etching, and polishing after each process is completed, and / or of finished products. The optical projection measurement method is known as a method for measuring this edge profile. The light projection measurement method involves projecting light onto the chamfered edge of a wafer from a direction approximately parallel to the front and back surfaces of the wafer, and capturing a projected image of the wafer edge (cross-sectional shape cut in the thickness direction) using a camera from a direction opposite to the light projection direction.

[0003] Patent Document 1 describes that when measuring the end face shape of a semiconductor wafer or the like based on its projected image, in order to perform accurate shape measurement without being affected by any adhesions present on the end face, predetermined image processing is performed on each of the projected images at multiple set angles.

[0004] Furthermore, Patent Document 2 describes that when measuring the two-dimensional shape of the outer peripheral edge portion of a semiconductor wafer that has a long depth along the optical axis, a collimator lens is used to irradiate light that is as nearly parallel as possible in order to prevent blurring of the contours and the occurrence of diffraction fringes in the projected image. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-25079 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-145487 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-mentioned conventional technologies described in Patent Documents 1 and 2, only the top surface shape (two-dimensional) of the notch portion of the wafer could be measured, and the more complex three-dimensional shape of the notch portion could not be measured with high accuracy. Furthermore, the accuracy of shape measurement of the peripheral portion other than the notch portion was not sufficient due to factors such as the wafer alignment (posture), crystal orientation, and light diffraction (light deflection), which blurred the outline.

[0007] Therefore, an object of the present invention is to provide a shape measuring device that can measure the shape of a plate-shaped object to be measured, particularly a notch portion of a wafer that has a complex shape, with high accuracy. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0009] [1] A shape measuring device for measuring the shape of a plate-shaped object by scanning the surface of the object and acquiring multiple surface images of the object, the shape measuring device comprising: an imaging system that irradiates the object with parallel light and acquires the surface images; a stage system that holds the object and adjusts the attitude of the object relative to the imaging system; and a control device, wherein the control device comprises an attitude adjustment unit that controls the imaging system and the stage system to scan the surface while adjusting the attitude and acquire multiple surface images; and an image processing unit that generates a restored model of the three-dimensional shape of the object from the acquired multiple surface images, wherein the attitude adjustment unit adjusts the attitude when acquiring the surface images so that the angle of incidence of the parallel light on the surface is within a predetermined range. [2] The shape measuring device according to [1], wherein the posture adjustment unit determines the amount of adjustment based on design data of the three-dimensional shape of the object to be measured that is stored in advance. [3] The shape measuring device according to [1] or [2], wherein the stage system includes a chuck table with a five-axis structure, which includes the three axes of X, Y, and Z, as well as two additional axes of a yaw axis for rotation and a pitch axis for tilt. [4] A shape measurement device as described in [1] or [2], which has a plurality of the imaging systems and an imaging system switching mechanism for switching between the imaging systems, and the control device switches the imaging system to be used to a predetermined imaging system based on a correspondence with the object to be measured. [5] The shape measuring device according to [4], wherein the object to be measured is a wafer, the imaging system includes at least two or more types selected from the group consisting of a system for acquiring a white light interference microscope image, a system for acquiring a confocal microscope image, and a system for acquiring images by photometric stereo using a polarizing plate, and the control device switches to the imaging system for acquiring a white light interference microscope image when the wafer is a wafer after grinding processing, to the imaging system for acquiring a confocal microscope image when the wafer is a wafer after etching processing, and to the imaging system for acquiring images by photometric stereo when the wafer is a wafer after polishing processing. [6] The shape measuring device according to [3], wherein the object to be measured is a wafer, and the attitude adjustment unit, when acquiring the surface image of the edge portion of the wafer, rotates the pitch axis with respect to an inclined surface or an end face to adjust the angle of incidence, and acquires the surface image while scanning the imaging system in the direction of the X axis, and then rotates the yaw axis to acquire the surface image of the outer periphery. [7] The shape measuring device described in [6], wherein when acquiring the surface image of the R portion of the wafer, the attitude adjustment unit divides the pitch axis in rotational increments of a predetermined pitch angle to acquire the surface image. [8] The shape measuring device described in [3], wherein the object to be measured is a wafer, and the attitude adjustment unit, when acquiring the surface image of one R portion of the notch portion of the wafer, fixes the focal length of the imaging system, places the imaging system on an optical axis passing through the center of the one R portion, and rotates the yaw axis to acquire the surface image. [9] The shape measuring device described in [3], wherein the object to be measured is a wafer, and the attitude adjustment unit fixes the focal length of the imaging system and the yaw axis and adjusts the angle of incidence when acquiring the surface image of the straight portion of the notch.

[10] The shape measuring device described in [3], wherein the object to be measured is a wafer, and the posture adjustment unit, when acquiring the surface image of the bottom R portion of the notch portion of the wafer, fixes the focal length of the imaging system, places the imaging system on an optical axis passing through the center of the bottom R portion, and acquires the surface image while scanning in the Z-axis direction and the Y-axis direction. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a shape measuring device that can measure the shape of a plate-shaped object to be measured, particularly even a notch portion of a wafer having a complex shape, with high precision. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a functional block diagram of a shape measuring device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing the basic configuration of an imaging system for acquiring a white light interference microscopic image. [Figure 3] FIG. 1 is a diagram showing the basic configuration of an imaging system for acquiring confocal microscopic images. [Figure 4] FIG. 1 is a diagram illustrating the basic configuration of an imaging system for acquiring images by photometric stereo. [Figure 5] FIG. 2 is a perspective view showing the configuration of a stage system. [Figure 6] FIG. 2 is a configuration diagram showing the relationship between the imaging system and the object to be measured, as viewed from the front along the Y axis. [Figure 7] FIG. 2 is a configuration diagram showing the relationship between the imaging system and the object to be measured, as viewed from the front along the X axis. [Figure 8] 4 is a flowchart showing a procedure for measuring the three-dimensional shape of an object to be measured by the shape measuring device. [Figure 9] 1A to 1C are explanatory diagrams of a procedure for measuring the three-dimensional shape of a notch portion of an object to be measured, which is a wafer. [Figure 10]FIG. 10 is an explanatory diagram showing a method for acquiring a surface image when data is missing. [Figure 11] FIG. 10 is a Y-axis front view showing the relationship between the imaging system and the object to be measured when measuring the outer peripheral edge portion. [Figure 12] 10 is an X-axis front view showing the relationship between the imaging system and the object to be measured when acquiring a surface image of the inclined surface of the outer peripheral edge portion. FIG. [Figure 13] FIG. 10 is a detailed view showing the cross-sectional shape of the outer peripheral edge portion and the imaging direction. [Figure 14] 10A and 10B are explanatory diagrams of posture adjustment when acquiring a surface image of the outer peripheral edge portion. [Figure 15] FIG. 10 is a diagram showing the imaging trajectory of one R portion of X3 (end face) in the notch portion. [Figure 16] FIG. 10 is a diagram showing an imaging trajectory of the straight portion of X3 (end face) in the notch portion. [Figure 17] FIG. 10 is a diagram showing the imaging trajectory of the bottom R portion of X3 (end face) in the notch portion. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0013] The embodiment shown below is an example that embodies the technical concept of the present invention, and the technical concept of the present invention does not limit the materials, shapes, structures, and arrangements of the components to the following embodiment. The drawings are schematic. Therefore, the relationship and ratio between thickness and planar dimensions may differ from the actual ones, and the relationship and ratio between dimensions may also differ between the drawings.

[0014] [Shape measuring device] A shape measuring apparatus according to an embodiment of the present invention (hereinafter also referred to as "this shape measuring apparatus") is a shape measuring apparatus for measuring the shape of a plate-shaped object by scanning the surface of the object and acquiring multiple surface images of the object. The shape measuring apparatus includes an imaging system that irradiates the object with parallel light and acquires the surface images, a stage system that holds the object and adjusts the attitude of the object relative to the imaging system, and a control device. The control device includes an attitude adjustment unit that controls the imaging system and the stage system to scan the surface while adjusting the attitude and acquire multiple surface images, and an image processing unit that generates a restored model of the three-dimensional shape of the object from the acquired multiple surface images. The attitude adjustment unit adjusts the attitude of the object so that the angle of incidence of the parallel light on the surface is within a predetermined range when acquiring the surface images.

[0015] 1 is a functional block diagram of the shape measuring apparatus. The shape measuring apparatus 100 includes a stage system 30 that holds a plate-shaped object 1 to be measured (typically a work-in-progress after various processes and / or a finished wafer) and controls its posture, an imaging system 10 that irradiates the object 1 with parallel light and acquires a surface image, and a control device 20. The control device 20 includes a posture adjustment unit 21 that controls the imaging system 10 and the stage system 30 to scan the surface of the object 1 to acquire multiple surface images while adjusting the posture of the object 1, and an image processing unit 22 that generates a restored model of the three-dimensional shape of the object 1 to be measured.

[0016] The material, shape, size, etc. of the plate-shaped DUT 1 are not particularly limited, but a semiconductor wafer is typically preferred. The semiconductor wafer may be one cut from an ingot; one that has undergone processes such as grinding, etching, and polishing; or a finished product that has undergone each of these processes. The material is also not particularly limited, and may be any of single crystal silicon, sapphire, silicon carbide, gallium phosphide (GaP), gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN), etc.

[0017] The imaging system 10 has the function of irradiating the object to be measured 1 with parallel light and acquiring a surface image of the object to be measured 1, and typically preferably includes a camera, a parallel light source, a beam splitter, and a focusing optical system. Although the shape measuring device 100 has one imaging system 10, the shape measuring device 100 may have multiple imaging systems 10, in which case the shape measuring device 100 may have an imaging system switching mechanism for switching between and using the multiple imaging systems 10.

[0018] When the shape measuring device 100 has a plurality of imaging systems 10, it is preferable that each imaging system 10 is used according to the type of the object to be measured 1. Specifically, it is preferable that the control device 20 switches to a predetermined imaging system 10 based on the correspondence with the object to be measured 1.

[0019] For example, if the object 1 is a wafer after grinding, the surface of the object 1 has many grinding marks from the grinding tool, and light irradiated onto the surface of the object 1 is often diffusely reflected. In other words, the surface of the wafer after grinding is in a state where diffuse reflection is dominant. In such a case, it is preferable to use an imaging system 10 for acquiring a white light interference microscopic image in order to acquire a surface image more accurately and efficiently.

[0020] 2 is a diagram showing the basic configuration of an imaging system 10 for acquiring a white light interference microscopic image. Light from a light source 10-1 (laser or LED) having a Gaussian beam profile passes through a collimating optical system 10-2 (e.g., a beam expander) that collimates the diverging light, a beam splitter 10-3, and an objective lens 10-4, before being irradiated onto the object under test 1. Note that the light source 10-1 may be a parallel light source, in which case the collimating optical system 10-2 may not be provided.

[0021] The camera 10-7 captures images of light reflected from the object 1 and passing through the objective lens 10-4, beam splitter 10-3, and focusing optical system 10-6 (e.g., a focusing lens), as well as light reflected by the reference mirror 10-5 and returning along the same optical path. When the light reflected from the object 1 and the light reflected by the reference mirror 10-5 overlap, a spatial interference pattern (interference fringes) is obtained. The interference fringes contain information about the difference in the optical paths of the two, and by analyzing the contrast and phase changes of the interference fringes that appear when the objective lens 10-4 is scanned in the vertical direction, data on the surface topography can be obtained.

[0022] Furthermore, for example, if the object 1 to be measured is a wafer after etching (e.g., alkaline etching), the distribution of crystal orientation on the surface and the presence of etch pits may cause the reflection characteristics of the surface (direct reflection / diffuse reflection of irradiated light) to vary locally (coexist). In such a case, it is preferable to use an imaging system 10 for acquiring confocal microscopic images in order to acquire surface images more accurately and efficiently.

[0023] Figure 3 is a diagram showing the basic configuration of an imaging system 10 for acquiring confocal microscopic images. The imaging system 10 for acquiring confocal microscopic images acquires a three-dimensional image using an optical microscope with a shallow focal depth and a pinhole confocal optical system. As in Figure 2, light from a light source 10-1 passes through a collimating optical system 10-2, which collimates diverging light, a beam splitter 10-3, and an objective lens 10-4, before irradiating the object under test 1. A pinhole 10-8 is positioned in front of the light source 10-1 and a camera 10-7. Therefore, the camera 10-7 captures the light reflected from the object under test 1 and passing through the objective lens 10-4, the beam splitter 10-3, the focusing optical system 10-6, and the pinhole 10-8.

[0024] As a result, the out-of-focus image is blocked by the pinhole 10-8, preventing the acquisition of a strong signal. As a result, only the in-focus image is acquired. When performing three-dimensional measurements, the beam is scanned horizontally and then vertically to capture the surface. The in-focus image is obtained by setting a vertical step interval and capturing images of the surface at each height. The peak position of the detected light intensity corresponds to the surface height of the target sample, and this can be saved as three-dimensional surface shape data by the image processing unit 22, which will be described later.

[0025] Furthermore, for example, when the object to be measured 1 is a wafer after polishing, the surface is polished to a mirror finish, so direct reflection is dominant. In such a case, in order to acquire surface images more accurately and efficiently, it is preferable to use an imaging system 10 for acquiring images by photometric stereo using polarizing plates.

[0026] 4 is a diagram showing the basic configuration of an imaging system 10 for acquiring images using photometric stereo. Photometric stereo measures normal vectors, which are three-dimensional shape information of an object surface, from multiple images captured by changing the position of a light source 10-1. If the surface of the object 1 to be measured is a mirror, direct reflection will be dominant. In this case, it is difficult to obtain an accurate image using an optical system for obtaining a white light interference microscope image or an optical system for obtaining a confocal microscope image, so it is preferable to use photometric stereo and then remove highlights, which are areas with high brightness due to gloss.

[0027] Light from light source 10-1 passes through polarizing plate 10-9, collimating optical system 10-2, beam splitter 10-3, and objective lens 10-4 before being irradiated onto object under test 1. Camera 10-7 captures the light that is reflected from object under test 1 and passes through objective lens 10-4, beam splitter 10-3, polarizing plate 10-10, and focusing optical system 10-6. Polarizing plate 10-9 and polarizing plate 10-10 are arranged with their polarization axes orthogonal to each other at 90° (crossed Nicol arrangement).

[0028] This optical arrangement eliminates reflection of the light source 10-1 due to specularly reflected light (linearly polarized light) from the object 1 under test, and only diffusely reflected light (unpolarized light) reaches the camera 10-7. This eliminates or reduces harmful "glare" or "shine" caused by reflection of the light source 10-1.

[0029] Returning to FIG. 1, the stage system 30 has the function of holding the object to be measured 1 and adjusting the attitude of the object to be measured 1 relative to the imaging system 10, and preferably includes a chuck table with a five-axis structure, which typically includes the three axes of X, Y, and Z, as well as two additional axes of a yaw axis for rotation and a pitch axis for tilt.

[0030] 5 is a perspective view showing the configuration of the stage system 30. The chuck table 16 that holds the object 1 to be measured, which is a wafer, has an attitude changing mechanism that allows movement along five axes, including the X-axis, Y-axis, Z-axis, yaw axis, and two additional pitch axes, so that the entire surface of the object 1 to be measured can be irradiated with measurement light from the imaging system 10 to acquire a surface image.

[0031] FIG. 6 is a configuration diagram showing the relationship between the imaging system 10 and the object to be measured 1, as viewed from the front along the Y axis. 2, 3, and 4 is fixed to a base board 15. The chuck table 16, which holds the workpiece 1 and changes its posture, is preferably a vacuum chuck type, and has a five-axis structure that adds two axes, a yaw axis for rotation and a pitch axis for tilt, in addition to the three axes of X, Y, and Z. This allows the surface of the workpiece 1 to be scanned gradually at a scan pitch P in the X-axis direction, thereby acquiring a surface image.

[0032] Furthermore, the edge portion 5 of the outer periphery of the object to be measured 1 is imaged by rotating the pitch axis so that the plane illuminated by the imaging system 10 is perpendicular to the slope and end face (in other words, so that the incident angle is 0°). Furthermore, the outer periphery can be imaged in a full circle by rotating the yaw axis 360 degrees. Note that the imaging system 10 may be configured so that the base board 15 can move in the X-, Y-, and Z-axis directions.

[0033] FIG. 7 is a configuration diagram showing the relationship between the imaging system 10 and the object 1 to be measured, as seen from the front along the X axis. As in FIG. 7, the surface of the object 1 to be measured is gradually scanned with parallel measurement light at a scan pitch P in the Y axis direction to obtain a surface image. The edge portion 5 on the outer periphery is imaged by rotating the pitch axis so that the irradiated surface is vertical (in other words, so that the incident angle is 0°). Furthermore, the outer periphery can be imaged by rotating the yaw axis 360 degrees.

[0034] Returning to Figure 1, the control device 20 is typically a computer having a CPU (Central Processing Unit), memory, etc., and the functions of the posture adjustment unit 21 and the image processing unit 22 are realized by the CPU executing a program stored in the memory.

[0035] The attitude adjustment unit 21 has a function of controlling the stage system 30 to control the attitude of the object 1, and is realized by the CPU executing a program stored in the memory of the control device 20. When acquiring a surface image, the attitude adjustment unit 21 adjusts the attitude of the object 1 so that the angle of incidence of parallel light with respect to the surface of the object 1 falls within a predetermined range.

[0036] It is generally known that the imaging angle (incident angle of parallel light) at which an accurate image can be acquired varies depending on the optical system (imaging method) of the imaging system 10. For example, in the case of imaging systems for acquiring white light interference microscopic images, Mirau type, Michelson type, etc. are known, but it is known that each of them has a limited range of imaging angles at which an accurate image can be acquired. This shape measuring device 100 has an attitude adjustment unit 21, and adjusts the angle of incidence (imaging angle) of parallel light on the surface according to the imaging system 10 so that it is within a predetermined range, thereby enabling more accurate images to be obtained. There are no particular limitations on the specific incident angle, but in general, it is preferably 0 to 30°, more preferably 0 to 15°, and in one preferred embodiment, the incident angle is approximately 0°.

[0037] The method by which the posture adjustment unit 21 performs the above adjustment is not particularly limited, but it is preferable that the amount of adjustment be determined based on design data of the three-dimensional shape of the object to be measured 1 that is pre-stored in the memory of the control device 20. For example, when the object 1 is a wafer, the design data of the three-dimensional shape of the object to be measured may be a design drawing (specifications) of the product wafer. This design data may typically include data on the outer shape of the wafer (periphery and notch) and the three-dimensional shape of the notch. Specifically, the design data may be a form that is a point cloud expressed in a three-dimensional orthogonal coordinate system.

[0038] The image processing unit 22 has the function of generating a reconstruction model of the three-dimensional shape of the object to be measured 1 from multiple surface images acquired while scanning the surface of the object to be measured 1, and is realized by the CPU executing a program stored in the memory of the control device 20.

[0039] Surface images for 3D reconstruction are obtained by, for example, using laser light as the observation light (measurement light) and extracting and combining in-focus areas from multiple images obtained from an all-focus microscopy system, i.e., an image sensor. High-resolution, ultra-deep images can also be obtained by generating all-focus images in which all positions are in focus. Alternatively, photometric stereo can also be used to simultaneously perform detailed shape measurements of areas with relatively small unevenness (small elevation differences due to slope, for example, an elevation difference of 10 nanometers).

[0040] Next, the operation of the shape measuring device 100 will be described. FIG. 8 is a flowchart showing the procedure for measuring the three-dimensional shape of an object to be measured by the shape measuring device 100. First, in step S1, design data of the three-dimensional shape of the object to be measured is acquired. The method of acquiring the data is not particularly limited, and the design data may be read by a CPU in advance from a memory corresponding to the type of object to be measured, or may be input from an external device according to the object to be measured 1.

[0041] Next, in step S2, the amount of adjustment of the attitude of the object under test 1 is determined by the attitude adjustment unit 21 controlled by the control device 20 based on the design data. In other words, the trajectory (imaging trajectory) of the movement of the object under test 1 relative to the imaging system 10 is calculated. The above will be described in detail later using a specific example.

[0042] Next, in step S3, based on the imaging trajectory calculated in step S2, the posture adjustment unit 21 controls the imaging system 10 and the stage system 30, and the surface is scanned while adjusting the posture of the object to be measured 1, thereby acquiring a surface image of the object to be measured 1. At this time, the imaging position is adjusted so as to scan the surface of the object to be measured 1, so that an image over a wide range of the surface of the object to be measured 1 is acquired. At this time, the imaging system 10 may also be moved in addition to the stage system 30. In this way, the posture adjustment is performed more efficiently.

[0043] Next, in step S4, the image processing unit 22 forms a restored model of the three-dimensional shape from the plurality of surface images obtained in step S3.

[0044] The above measurement procedure will be further explained by taking as an example a case where the object to be measured 1 is a wafer. Figure 9 is an explanatory diagram of the procedure for measuring the three-dimensional shape of the notch portion 4 of the wafer 1. In recent years, semiconductor wafer production sites have been required to improve the quality of the shape, etc., all the way to the periphery, and the shape of the notch portion 4 in particular is prone to deformation during processes such as grinding, etching, and polishing, which affects the yield in subsequent processes.

[0045] 9(a) is a plan view of notch portion 4, and Fig. 9(b) is a cross-sectional view of the dashed line portion of notch portion 4. Notch portion 4 has a complex three-dimensional shape, and from the left end of Fig. 9(a) there is (1) a one-side R portion, (2) a straight portion, (3) a bottom R portion, (2') a straight portion that is inclined in a different direction from the (2) straight portion, and (1') a one-side R portion that is symmetrical to the (1) one-side R portion.

[0046] The cross-sectional shape has R1 and R2 as R portions connected to the slopes X1 and X2 at both ends of the end face X3, which is perpendicular to the top face 2 or bottom face 3 of the wafer 1 under test. X1, X2 and R1, R2 are symmetrical with respect to the midpoint of X3. The top face 2 or bottom face 3, end face X3, and slopes X1 and X2 of the wafer under test 1 also have different crystal orientations. Note that the cross-sectional shape in Figure 9(b) is consistent not only at the notch 4 but also at the edge 5 on the outer periphery.

[0047] Therefore, the postures of the imaging system 10 and the object 1 to be measured are changed in accordance with the notch shape so that the imaging system 10 (incident angle of parallel light) is perpendicular to the surface shape of the notch 4. To make the imaging system 10 perpendicular, the posture adjustment unit 21 calculates the posture adjustment amount (imaging trajectory) of the object 1 to be measured by the stage system 30 based on the information acquired in step S1 (step S2).

[0048] As one form, the attitude adjustment amount is set as a condition under which the focal length of the imaging system 10 is constant and the angle of incidence of the irradiated parallel light is within a predetermined range based on the design data (point cloud data in a Cartesian coordinate system, etc.) information acquired in step S1. In other words, the attitude adjustment amount is determined as "a suitable optical imaging (image acquisition) condition of the surface shape" according to the surface state of the object 1 to be measured, based on the three-dimensional coordinates of the notch-shaped surface for which design values ​​are given.

[0049] Next, the imaging trajectory of the workpiece 1 is controlled based on the determined attitude adjustment amount, and a surface image of the workpiece 1 is acquired (step S3). The chuck table 16, which holds the workpiece 1 and changes its posture, is preferably a vacuum chuck, and one form is preferably a five-axis structure that adds two axes, a yaw axis for rotation and a pitch axis for tilt, in addition to the three axes of X, Y, and Z.

[0050] This shape measuring device 100 can adjust the attitude of the workpiece 1 even for a surface with sharp irregularities by moving the chuck table 16 in five axes and using an attitude adjustment mechanism, so that the angle of the imaging system 10 (incident angle of the irradiated light) relative to the surface shape can be kept within a predetermined range. As a result, it is possible to accurately image the surface shape of the workpiece 1 (acquire a surface image).

[0051] Furthermore, the inclination shape of the surface of the object 1 can be measured by examining the amount of light reflected from the surface irradiated with parallel measurement light, thereby obtaining accurate white light interference microscopic images, confocal microscopic images, photometric stereo, etc.

[0052] After the processing of step S3, depth coordinates, which are three-dimensional coordinates, are obtained from the acquired surface images, and three-dimensional reconstruction is performed to create a reconstructed model (step S4). After the restored model is created, it may be used to determine whether the master wafer (work) is good or bad, and as a shape condition for subsequent processes.

[0053] Surface images for 3D reconstruction can be obtained, for example, by using laser light as the observation light (measurement light) and extracting and combining in-focus areas from multiple images obtained from an all-focus microscopy system, i.e., an imaging element. High-resolution, ultra-deep images can also be obtained by generating all-focus images in which all positions are in focus. Alternatively, photometric stereo can also be used to simultaneously perform detailed shape measurements of areas with relatively small unevenness (small elevation differences due to slope, for example, elevation differences of around 10 nanometers).

[0054] Figure 10 is an explanatory diagram showing a method for acquiring a surface image when data is missing. Data may be missing when the surface has a large inclination of unevenness or when there are defects such as irregular etch pits. For example, existing optical surface texture measuring instruments have a numerical aperture (NA), which represents the light collection limit when there is no aberration, of approximately 0.55. Furthermore, when the inclination is 7.9° or more, the lens is unable to capture part of the reflected light from the surface being measured due to angle tracking, which can result in data missing.

[0055] Therefore, in this case, the pitch angle of the measurement target surface is rotated in increments of 7° or less, and multiple surface images are obtained from the same location at different imaging angles. If there is waviness (unevenness) on the measurement target surface as shown in Figure 10(a), the surface image in Figure 10(a), the surface image obtained by rotating the measurement target surface counterclockwise as shown in Figure 10(b), and the surface image obtained by rotating the measurement target surface clockwise as shown in Figure 10(c) are combined to integrate the obtained images. This allows the surface image of the area of ​​interest to be obtained as a consistent shape with no missing data.

[0056] Fig. 11 is a Y-axis front view showing the relationship between the imaging system 10 and the object to be measured 1 when measuring the outer peripheral edge portion 5. The cross section of the edge portion 5 has a slope (angle θ) as shown in Fig. 11(a) when laid flat. Fig. 11(b) shows the measurement state of the slope. The posture adjustment unit 21 rotates the chuck table 16 around the pitch axis so that the surface illuminated by the imaging system 10 is vertical, in other words, so that the angle of incidence is approximately 0°, and causes the imaging system 10 to acquire a surface image while scanning the imaging system 10 in the X-axis direction.

[0057] FIG. 11(c) shows the illumination state of the end face, and a surface image is acquired by rotating the pitch axis so that the incident angle of the parallel light is approximately 0° (within a predetermined range) in the same manner as in FIG. 11(b). Furthermore, the chuck table 16 is rotated 360 degrees around the yaw axis to acquire an image of the outer periphery surface.

[0058] FIG. 12 is an X-axis front view showing the relationship between the imaging system 10 and the workpiece 1 when acquiring a surface image of the slope of the outer peripheral edge portion 5. The workpiece 1 is held on a chuck table 16 similar to that shown in FIG. 9. When acquiring the surface image of the edge portion 5, the attitude adjustment unit 21 controls the attitude of the workpiece 1 around the pitch axis and tilt axis so that the angle of incidence of the parallel light falls within a predetermined range (for example, approximately 0°), thereby acquiring the surface image. Note that the irradiation conditions may be determined according to the crystal orientation and shape.

[0059] 13 is a detailed diagram showing the cross-sectional shape and imaging direction of the outer peripheral edge portion 5. The arrow indicates the direction of incidence of parallel light from the imaging system 10. The cross-sectional shape changes from the top surface 2 of the object to be measured 1 to the slope X1, the curved portion R1, and ends at the end surface X3 that is perpendicular to the top surface 2.

[0060] Figure 14 is an explanatory diagram of attitude adjustment when acquiring a surface image of the outer peripheral edge portion 5. When acquiring a surface image of the edge portion 5 of the object under test 1, the pitch axis is rotated at each portion of the edge portion 5 (each portion explained in Figure 9(b)) to adjust the angle of incidence and scan the surface. Figure 14(a) shows the attitude control method when acquiring a surface image of X1, Figure 14(c) shows X3, and Figure 14(e) shows X2, and the method is performed by gradually moving in scan pitch increments. R1 in FIG. 14(b) and R2 in FIG. 14(d) show the imaging of the R portion, and the pitch axis is divided into rotational increments of a predetermined pitch angle. For example, since R1 and R2 are 60 to 70°, it is preferable to divide them into three and image them.

[0061] 15 is a diagram showing the imaging trajectory of the (1') piece R portion (see FIG. 9(b)) of X3 (end face) in the notch portion 4. When acquiring a surface image of the (1') piece R portion of the notch portion 4, the attitude adjustment unit 21 fixes the focal length of the imaging system as shown in FIG. 15(a), places the imaging system on the optical axis passing through the center of the (1') piece R portion, and rotates the yaw axis of the chuck table 16 to acquire the surface image, as shown in FIG. (1') By ​​placing the imaging system on the optical axis passing through the center of the R-shaped portion, the arc of the R-shaped portion and the incident direction of the parallel light become approximately perpendicular. In other words, by adjusting the posture as described above, it is possible to acquire a surface image by scanning the entire R-shaped portion (scanning in the Z-axis and Y-axis directions) while adjusting the incident angle within a predetermined range. Once the surface image of the curved portion is acquired as described above, the straight portion (2') is reached as shown in Figure 15(b). The same is true for the curved portion (1), which is symmetrical.

[0062] Fig. 16 is a diagram showing the imaging trajectory of the (2') straight portion (see Fig. 9(b)) of X3 (end face) in the notch portion 4. The surface image of the straight portion of the notch portion 4 is acquired by scanning in the Y-axis direction as shown in Fig. 16, fixing the focal length and yaw axis, and adjusting the angle of incidence.

[0063] Figure 17 is a diagram showing the imaging trajectory of the (3) bottom R portion of X3 (end face) in the notch portion 4. As shown in Figure 17(a), the surface image of the bottom R portion of the notch portion is acquired by fixing the focal length of the imaging system, and by controlling the rotation of the yaw axis, placing the imaging system on the optical axis passing through the center of the bottom R portion, adjusting the angle of incidence to approximately 0°, and scanning in the Z-axis and Y-axis directions.

[0064] As described above, the surface image of the object to be measured 1 is adjusted to optimal conditions according to the shape of the object to be measured 1 by the posture adjustment unit 21, so that shape measurement can be performed with high accuracy even for complex three-dimensional shapes such as the notch portion 4. [Explanation of symbols]

[0065] 1 Object to be measured, 2 Upper surface, 3 Lower surface, 4 Notch portion, 5 Edge portion, 10 Imaging system, 10-1 Light source, 10-10 Polarizing plate, 10-2 Collimating optical system, 10-3 Beam splitter, 10-4 Objective lens, 10-5 Reference mirror, 10-6 Focusing optical system, 10-7 Camera, 10-8 Pinhole, 10-9 Polarizing plate, 15 Base board, 16 Chuck table, 20 Control device, 21 Attitude adjustment unit, 22 Image processing unit, 30 Stage system, 100 Shape measurement device

Claims

1. 1. A shape measuring apparatus for measuring a shape of a plate-shaped object by acquiring a plurality of surface images while scanning the surface of the object, comprising: an imaging system that irradiates the object to be measured with parallel light and acquires the surface image; a stage system that holds the object to be measured and adjusts the attitude of the object to the imaging system; and a control device, The control device an attitude adjustment unit that controls the imaging system and the stage system to scan the surface while adjusting the attitude and acquire a plurality of surface images; an image processing unit that generates a restored model of the three-dimensional shape of the object to be measured from the acquired plurality of surface images, the attitude adjustment unit adjusts the attitude when acquiring the surface image so that an incident angle of the parallel light on the surface falls within a predetermined range; the object to be measured is a wafer after grinding processing, A shape measuring apparatus, wherein the imaging system is an imaging system for acquiring a white light interference microscope image.

2. 1. A shape measuring apparatus for measuring a shape of a plate-shaped object by acquiring a plurality of surface images while scanning the surface of the object, comprising: an imaging system that irradiates the object to be measured with parallel light and acquires the surface image; a stage system that holds the object to be measured and adjusts the attitude of the object to the imaging system; and a control device, The control device an attitude adjustment unit that controls the imaging system and the stage system to scan the surface while adjusting the attitude and acquire a plurality of surface images; an image processing unit that generates a restored model of the three-dimensional shape of the object to be measured from the acquired plurality of surface images, the attitude adjustment unit adjusts the attitude when acquiring the surface image so that an incident angle of the parallel light on the surface falls within a predetermined range; the object to be measured is a wafer after etching processing, A shape measuring apparatus, wherein the imaging system is an imaging system for acquiring a confocal microscopic image.

3. 1. A shape measuring apparatus for measuring a shape of a plate-shaped object by acquiring a plurality of surface images while scanning the surface of the object, comprising: an imaging system that irradiates the object to be measured with parallel light and acquires the surface image; a stage system that holds the object to be measured and adjusts the attitude of the object to the imaging system; and a control device, The control device an attitude adjustment unit that controls the imaging system and the stage system to scan the surface while adjusting the attitude and acquire a plurality of surface images; an image processing unit that generates a restored model of the three-dimensional shape of the object to be measured from the acquired plurality of surface images, the attitude adjustment unit adjusts the attitude when acquiring the surface image so that an incident angle of the parallel light on the surface falls within a predetermined range; the object to be measured is a polished wafer, A shape measuring apparatus, wherein the imaging system is an imaging system for acquiring images by photometric stereo.

4. 4. The shape measuring instrument according to claim 1, wherein the attitude adjusting unit determines the amount of the adjustment based on pre-stored design data of the three-dimensional shape of the object to be measured.

5. 5. The shape measuring apparatus according to claim 1, wherein the stage system includes a chuck table having a five-axis structure including three axes, namely, an X-axis, a Y-axis, and a Z-axis, as well as two axes, namely, a yaw axis for rotation and a pitch axis for tilt.

6. the object to be measured is a wafer, When acquiring the surface image of the edge portion of the wafer, the attitude adjustment unit rotating the pitch axis with respect to the inclined surface or the end surface to adjust the incident angle, and acquiring the surface image while scanning the imaging system in the X-axis direction; The shape measuring apparatus according to claim 5 , wherein the yaw axis is then rotated to acquire the surface image of the outer periphery.

7. When acquiring the surface image of the R portion of the wafer, The shape measuring instrument according to claim 6 , wherein the attitude adjusting unit divides the pitch axis into rotational increments of a predetermined pitch angle to acquire the surface image.

8. the object to be measured is a wafer, When acquiring the surface image of the one-side R portion of the notch portion of the wafer, the attitude adjustment unit 6. The shape measuring device according to claim 5, wherein the focal length of the imaging system is fixed, the imaging system is placed on an optical axis passing through the center of the one-side R portion, and the yaw axis is rotated to acquire the surface image.

9. the object to be measured is a wafer, When acquiring the surface image of the straight portion of the notch portion, the attitude adjustment unit The shape measuring apparatus according to claim 5 , wherein the focal length of the imaging system and the yaw axis are fixed, and the angle of incidence is adjusted.

10. the object to be measured is a wafer, 6. The shape measuring device according to claim 5, wherein, when acquiring the surface image of the bottom R portion of the notch portion of the wafer, the attitude adjustment unit fixes a focal length of the imaging system, places the imaging system on an optical axis passing through a center of the bottom R portion, and acquires the surface image while scanning in the Z-axis direction and the Y-axis direction.

11. 1. A shape measuring apparatus for measuring a shape of a plate-shaped object by acquiring a plurality of surface images while scanning the surface of the object, comprising: an imaging system that irradiates the object to be measured with parallel light and acquires the surface image; a stage system that holds the object to be measured and adjusts the attitude of the object to the imaging system; and a control device, The control device an attitude adjustment unit that controls the imaging system and the stage system to scan the surface while adjusting the attitude and acquire a plurality of surface images; an image processing unit that generates a restored model of the three-dimensional shape of the object to be measured from the acquired plurality of surface images, the attitude adjustment unit adjusts the attitude when acquiring the surface image so that an incident angle of the parallel light on the surface falls within a predetermined range; A plurality of the imaging systems; an imaging system switching mechanism that switches the imaging system; The control device switches the imaging system to be used to the imaging system that is predetermined based on a correspondence relationship with the object to be measured.

12. the object to be measured is a wafer, the imaging system includes at least two or more types selected from the group consisting of an imaging system for acquiring a white light interference microscope image, an imaging system for acquiring a confocal microscope image, and an imaging system for acquiring an image by photometric stereo using a polarizing plate; The control device When the wafer is a wafer after grinding processing, the imaging system for acquiring a white light interference microscope image includes: When the wafer is a wafer after etching, the imaging system for acquiring a confocal microscope image includes:

12. The shape measuring instrument according to claim 11, wherein when the wafer is a wafer that has been polished, the imaging system is switched to the imaging system for acquiring an image by photometric stereo.

Images