Shape measuring device and shape measurement method

Abstract

To provide a shape measuring device and a shape measurement method with which it is possible to analyze the shape of a notch formed at an edge of a wafer with good accuracy.SOLUTION: Provided is a shape measurement method for measuring the shape of a measurement surface on an edge of a wafer. The method includes: generating measurement data indicating the shape of a notch formed on the measurement surface on the basis of the coordinates of a point cloud that the imaging unit obtained by repeatedly imaging the notch when an optical unit (104), which includes a light source part having an optical axis parallel to the principal surface of the wafer and irradiating a measurement surface with measurement light along the optical axis, and an imaging part for imaging reflected light from the measurement surface, is moved relatively to the measurement surface; and analyzing the shape of the notch on the basis of the measurement data.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a shape measurement apparatus and a shape measurement method, and more particularly to a shape measurement apparatus and a shape measurement method for measuring the shape of the end portion of a wafer.

Background Art

[0002] When a disk-shaped wafer is surface-processed by a polishing apparatus, the end portion of the wafer is processed into a sharp shape, which may cause the wafer to crack or chip. Therefore, a grinding process (also referred to as chamfering) is performed on the wafer to remove the sharp portion at the end of the wafer and make the end portion into a round shape or a chamfered shape (see Patent Document 1).

[0003] The shape and dimensions of the end portion of the wafer formed by the grinding process are defined by the standards determined by industry associations or the requirements of clients. Therefore, it is necessary to grind the end portion within the defined range. For this reason, in the wafer manufacturing process, after the grinding process, the shape of the end portion of the wafer is measured, and shape measurement is performed to inspect whether the shape of the end portion is within the defined range.

[0004] Patent Document 2 discloses a shape measurement apparatus that measures the shape of the end portion of a wafer by a light projection measurement method. This shape measurement apparatus projects light onto the end portion of the ground wafer from directions substantially parallel to each of the front and back surfaces of the wafer, and images the projected image of the end portion of the wafer with a camera from a direction opposite to the light projection direction, and measures the shape of the end portion of the wafer based on the projected image.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, a notch called a notch may be formed at the end of the wafer to indicate the crystal orientation of the wafer. If there is a defect such as a scratch in the notch of the wafer (especially the saddle part that is recessed like a horse's saddle), it may trigger wafer breakage. Therefore, it is required to measure the shape of the notch of the wafer and detect defects such as scratches.

[0007] In the light projection measurement method described in Patent Document 2, since light is projected from a direction substantially parallel to each of the front and back surfaces of the wafer, a shadowed portion is generated in the saddle portion of the notch. Therefore, the shape measurement of the saddle portion of the notch could not be performed.

[0008] The present invention has been made in view of such circumstances, and an object thereof is to provide a shape measurement apparatus and a shape measurement method capable of accurately analyzing the shape of a notch formed at the end of a wafer.

Means for Solving the Problems

[0009] The present invention comprises the following aspects in order to achieve the above object.

[0010] The shape measurement apparatus according to the first aspect of the present invention is a shape measurement apparatus for measuring the shape of a measurement surface at the end of a wafer, and has an optical axis parallel to the main surface of the wafer, and irradiates the measurement surface with measurement light along the optical axis. And an imaging unit that images the reflected light from the measurement surface, a relative movement unit that relatively moves the optical unit with respect to the measurement surface, and the imaging unit repeatedly images the notch formed on the measurement surface by relatively moving the optical unit. An arithmetic unit that generates measurement data indicating the shape of the notch portion based on the coordinates of the obtained point group, and an analysis unit that performs shape analysis of the notch portion based on the measurement data.

[0011] The shape measurement apparatus according to the second aspect of the present invention is, in the first aspect, the analysis unit obtains an approximate curve from the coordinates of the point group.

[0012] In the shape measurement apparatus according to the third aspect of the present invention, in the second aspect, the imaging unit images the notch portion of the wafer to obtain the coordinates of the point cloud, and the analysis unit calculates at least two curves obtained by shifting the approximate curve along the direction orthogonal to the front or back surface of the wafer, thereby obtaining an approximate curve of the notch portion along the direction orthogonal to the front or back surface of the wafer passing through the saddle point of the notch portion.

[0013] The shape measurement apparatus according to the fourth aspect of the present invention includes, in any one of the first to third aspects, an output unit that outputs a determination result as to whether there is an abnormality in the wafer based on the measurement data.

[0014] In the shape measurement apparatus according to the fifth aspect of the present invention, in any one of the first to fourth aspects, the analysis unit determines whether there is an abnormality in the three-dimensional shape corresponding to the region data based on the region data extracted from the three-dimensional shape of the end portion of the wafer.

[0015] In the shape measurement apparatus according to the sixth aspect of the present invention, in any one of the first to fifth aspects, the analysis unit relatively moves the optical unit with respect to a master workpiece whose angle between each surface is known, and based on the coordinates of the point cloud obtained by repeatedly imaging the surface to be measured of the master workpiece by the imaging unit, determines an analysis coordinate system for analyzing the notch portion.

[0016] A shape measurement method for measuring the shape of the surface to be measured at the end of a wafer, having a light source unit having an optical axis parallel to the main surface of the wafer and irradiating the surface to be measured with measurement light along the optical axis, and an imaging unit for imaging the reflected light from the surface to be measured. When the optical unit is relatively moved with respect to the surface to be measured, measurement data indicating the shape of the notch portion is generated based on the coordinates of the point cloud obtained by repeatedly imaging the notch portion formed on the surface to be measured by the imaging unit, and shape analysis of the notch portion is performed based on the measurement data.

Advantages of the Invention

[0017] According to the present invention, the shape of the notch portion formed at the end of the wafer can be accurately analyzed.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0020] [Wafer Processing System] FIG. 1 is a plan view showing a schematic configuration of a wafer processing system 10. In the following description, among the three mutually orthogonal XYZ directions shown in the figure, the X direction and the Z direction refer to the horizontal direction, and the Y direction refers to the vertical direction (perpendicular direction).

[0021] As shown in FIG. 1, the wafer processing system 10 includes a cassette unit 12, a load unit 14, a grinding unit 16, a cleaning unit 18, a measuring unit 20, and a transfer unit 22.

[0022] The load unit 14 transfers the wafer W (shown in FIGS. 2 and 3, etc.) between the cassette unit 12, the grinding unit 16, and the measuring unit 20. This operation is performed by a supply / retrieval robot. The cassette unit 12 is provided with a wafer cassette in which a large number of wafers W to be chamfered are stored. The supply / retrieval robot takes out the wafers W one by one from the wafer cassette or stores the chamfered wafers W in the wafer cassette.

[0023] The supply / retrieval robot includes a three-axis rotating transfer arm, and this transfer arm is provided with a suction pad (not shown) on its upper surface. The transfer arm holds the wafer W by vacuum-sucking the lower surface of the wafer W with this suction pad. That is, the transfer arm of this supply / retrieval robot can move back and forth, up and down, and rotate while holding the wafer W, and transfers the wafer W by combining these operations.

[0024] The grinding unit 16 performs grinding processing on the edge of the wafer W, that is, from rough processing to finish processing.

[0025] FIG. 2 is a schematic configuration diagram showing a schematic configuration of a grinding device (chamfering device) 30 installed in the grinding unit 16. As shown in FIG. 2, the grinding device 30 includes a grinding table 32 for holding the wafer W, a grinding wheel 34, and a spindle motor 36 for rotating the grinding wheel 34.

[0026] The grinding table 32 has a holding surface 32a on its upper surface for sucking and holding the wafer W. The grinding table 32 is configured to be rotatable about a rotation axis P parallel to the Y direction by various actuators such as a motor drive mechanism (not shown).

[0027] The grinding wheel 34 is configured to be rotatable about a rotation axis parallel to the Y direction by a spindle motor 36. Further, the grinding wheel 34 is moved forward and backward in the Z direction relative to the end of the wafer W held by the grinding table 32. When the grinding wheel 34 is moved forward, the rotating grinding wheel 34 is relatively pressed against the outer peripheral portion (edge portion 80), which is the end of the rotating wafer W, and the outer peripheral portion of the wafer W is ground. The grinding wheel 34 in this example is a total grinding wheel having grinding grooves 34a on its outer peripheral portion, and the shape of the grinding grooves 34a is transferred to the outer peripheral portion of the wafer W during grinding.

[0028] The grinding device 30 is provided with, in addition to the above-described grinding wheel (coarse grinding wheel) 34, a fine grinding wheel (not shown). Thereby, after the outer peripheral portion of the wafer W is roughly processed with the grinding wheel 34, chamfering for finish grinding of the outer peripheral portion of the wafer W is performed with the fine grinding wheel. Further, the grinding device 30 is provided with a notch rough grinding wheel and a notch fine grinding wheel for grinding the notch portion 82 (see FIG. 4). Thereby, for the notch portion 82, after rough processing with the notch rough grinding wheel, chamfering as finish grinding is performed with the notch fine grinding wheel. Note that a plurality of grinding devices 30 may be installed in the grinding unit 16.

[0029] Returning to FIG. 1, the cleaning unit 18 cleans the wafer W after chamfering. This cleaning unit 18 includes a spin cleaning device (not shown). The spin cleaning device sprays a cleaning liquid onto the upper surface (front surface) of the wafer W while rotating the wafer W held by the cleaning table, and peels off and removes the dirt adhering to the upper surface of the wafer W.

[0030] The transfer unit 22 transfers the wafer W between the grinding unit 16 and the cleaning unit 18. The transfer unit 22 includes a transfer robot configured to be capable of linear motion in the Z direction and lifting motion in the Y direction (vertical direction). The transfer robot includes an arm portion, and a suction pad is provided at the tip thereof. The transfer robot transfers the wafer W while sucking the upper surface of the wafer W with the suction pad of the arm portion. Thereby, in the transfer unit 22, the transfer robot transfers the wafer W chamfered in the grinding unit 16 to the cleaning unit 18, or transfers the wafer W cleaned in the cleaning unit 18 to the grinding unit 16.

[0031] The measurement unit 20 measures the thickness and performs pre-alignment of the wafer W to be chamfered. The measurement unit 20 includes a measurement table (denoted by reference numeral 102 in FIG. 3), a thickness sensor, and an orifla-notch detection sensor in order to measure the thickness and perform pre-alignment of the wafer W.

[0032] The measurement table rotates the wafer W around its central axis. The thickness sensor is, for example, a capacitance sensor and measures the distance from the upper surface to the lower surface of the wafer W. The measurement result of the capacitance sensor is output to an arithmetic unit (not shown), and the thickness of the wafer W is obtained. The orifla-notch detection sensor is, for example, a laser sensor and detects the position of the orifla or notch of the wafer W. Here, the orifla is substantially an orientation flat, which is a flat portion formed at the end of the wafer W to indicate the crystal orientation of the wafer W, and the notch portion 82 is a notch portion formed to indicate the crystal orientation of the wafer. Examples of the thickness sensor include an interference type in addition to the capacitance type, and examples of the orifla-notch detection sensor include an image sensor.

[0033] In addition, the measurement unit 20 includes a diameter measuring device (not shown) that measures the diameter of the chamfered wafer W, and a shape measuring device 100 (an example of the "shape measuring device" of the present invention) that measures the three-dimensional shape of the edge of the chamfered wafer W. The configuration of the shape measuring device 100 will be described in detail later.

[0034] Next, an overview of the operation of the wafer processing system 10 of the embodiment will be described.

[0035] First, a wafer W is taken out from a cassette attached to the cassette unit 12 by the supply / retrieval robot of the load unit 14 and conveyed to the measurement unit 20. The wafer W conveyed to the measurement unit 20 is placed on the measurement table of the measurement unit 20.

[0036] Next, in the measurement unit 20, the thickness of the wafer W is measured and pre-alignment is performed using a thickness sensor and an orifice-notch detection sensor. Also, the diameter of the wafer W is measured using a diameter measuring device.

[0037] Next, the wafer W on which various measurements have been performed in the measurement unit 20 is conveyed to the grinding unit 16 by the supply / retrieval robot of the load unit 14. The wafer W conveyed to the grinding unit 16 is placed on the grinding table 32 of the grinding device 30.

[0038] Next, in the grinding unit 16, grinding processing (chamfering) of the edge of the wafer W is performed by the grinding device 30. Specifically, after rough machining the edge portion 80 which is the outer peripheral portion of the wafer W with a grinding wheel 34, chamfering for finish grinding of the outer peripheral portion of the wafer W is performed with a finish grinding wheel. Also, for the notch portion 82 of the wafer W, after rough machining with a notch rough grinding wheel, chamfering as finish grinding is performed with a notch finish grinding wheel.

[0039] Next, the wafer W on which grinding processing (chamfering) has been completed in the grinding unit 16 is conveyed from the grinding unit 16 to the cleaning unit 18 using the transfer robot of the transfer unit 22. Then, in the cleaning unit 18, the wafer W is cleaned by a spin cleaning device.

[0040] Next, the wafer W that has been cleaned in the cleaning unit 18 is transported from the cleaning unit 18 to the grinding unit 16 by the transfer robot of the transfer unit 22. Thereafter, the wafer W is transported from the grinding unit 16 to the measuring unit 20 by the supply / retrieval robot of the load unit 14. The wafer W transported to the measuring unit 20 is placed on the measuring table.

[0041] Next, in the measuring unit 20, the diameter of the wafer W is measured using a diameter measuring instrument, and the three-dimensional shape of the end portion of the wafer W is measured by the shape measuring device 100. The measurement results of the measuring unit 20 (the diameter of the wafer W and the three-dimensional shape of the end portion of the wafer W) are output to the output unit. Note that the control device 110 described later may calculate a determination result indicating whether or not the measurement results of the measuring unit 20 are within a predetermined specified range, and output the determination result to the output unit (reference numeral 114 in FIG. 6).

[0042] Next, the wafer W that has been measured in the measuring unit 20 is transported from the measuring unit 20 to the cassette unit 12 by the supply / retrieval robot of the load unit 14 and stored in the cassette.

[0043] [Shape Measuring Device] Next, the configuration of the shape measuring device 100 will be described. This shape measuring device 100 calculates three-dimensional shape data indicating the height information (such as surface shape and surface roughness) of the measured surface of the end portion of the wafer W, which is the measurement object, based on a plurality of captured images captured at regular pitches while scanning the optical unit 104 (white interference microscope) described later in the scanning direction (Z direction).

[0044] FIG. 3 is a side view (viewed from the X direction) showing the schematic configuration of the shape measuring device 100. FIG. 4 is a plan view (viewed from the Y direction) showing the schematic configuration of the shape measuring device 100.

[0045] As shown in FIGS. 3 and 4, the shape measuring device 100 includes a measuring table 102, an optical unit 104, and a control device 110.

[0046] The measurement table 102 has a holding surface 102a on its upper surface for sucking and holding the wafer W. Further, the measurement table 102 is configured to be rotatable about a rotation axis G parallel to the Y direction. The table drive unit 116 is composed of various actuators such as a motor drive mechanism, and rotates the measurement table 102 about the rotation axis G under the control of a control device 110 described later. As a result, the wafer W sucked and held on the holding surface 102a of the measurement table 102 rotates and moves about the rotation axis G.

[0047] The optical unit 104 is composed of a white light interference microscope. This optical unit 104 is provided at a position adjacent to one side in the Z direction (the left side in FIG. 3) with respect to the measurement table 102. Specifically, the optical unit 104 is arranged such that its optical axis R (corresponding to the optical axis of the interference objective lens 124) is parallel (including substantially parallel) to the main surface (upper surface or lower surface) of the wafer W. In other words, the optical axis R of the optical unit 104 is arranged to be parallel (including substantially parallel) to the direction orthogonal to the rotation axis G of the measurement table 102 (preferably, to intersect the rotation axis G of the measurement table 102). Then, the optical unit 104 images the end portion (edge portion 80 or notch portion 82) of the wafer W from a position facing the end portion of the wafer W held on the measurement table 102.

[0048] Next, the configuration of the optical unit 104 will be described in detail. FIG. 5 is a schematic diagram showing the details of the configuration of the optical unit 104.

[0049] The optical unit 104 is a Michelson type white light interference microscope. As shown in FIG. 5, this optical unit 104 includes a light source unit 120, a beam splitter 122, an interference objective lens 124, an imaging lens 126, and a camera 128. They are arranged in the order of the interference objective lens 124, the beam splitter 122, the imaging lens 126, and the camera 128 along the left side in the Z direction from the measured surface of the end portion of the wafer W to be measured. The light source unit 120 is arranged at a position facing the beam splitter 122 in the Y direction.

[0050] Under the control of the control device 110, the light source unit 120 emits white light (low-coherence light with low coherence) in a parallel light beam as measurement light L1 toward the beam splitter 122. Although not shown in the figure, the light source unit 120 includes a light source capable of emitting the measurement light L1 such as a light-emitting diode, a semiconductor laser, a halogen lamp, and a high-intensity discharge lamp, and a collector lens that converts the measurement light L1 emitted from this light source into a parallel light beam.

[0051] For example, a half mirror is used as the beam splitter 122. The beam splitter 122 reflects a part of the measurement light L1 incident from the light source unit 120 toward the interference objective lens 124 on the right side in the Z direction. Further, the beam splitter 122 transmits a part of the combined light L3 (described later) incident from the interference objective lens 124 to the left side in the Z direction and emits this combined light L3 toward the imaging lens 126.

[0052] The interference objective lens 124 is of the Michelson type and includes an objective lens 124A, a beam splitter 124B, and a reference surface 124C. The beam splitter 124B and the objective lens 124A are arranged in order from the side of the surface to be measured along the left side in the Z direction. Further, the reference surface 124C is arranged at a position facing the beam splitter 124B in the Y direction. Hereinafter, the explanation will be made using a Michelson-type interference optical system, but the interference optical system is not limited to the Michelson type, and a known interference optical system such as the Mirau type or the Linnik type can be adopted.

[0053] The objective lens 124A has a condensing action and condenses the measurement light L1 incident from the beam splitter 122 onto the surface to be measured through the beam splitter 124B.

[0054] The beam splitter 124B is, for example, a half mirror. The beam splitter 124B splits a part of the measurement light L1 incident from the objective lens 124A as the reference light L2, transmits the remaining measurement light L1, emits it to the surface to be measured, and reflects the reference light L2 toward the reference surface 124C. The measurement light L1 transmitted through the beam splitter 124B is irradiated onto the surface to be measured and then reflected by the surface to be measured and returns to the beam splitter 124B.

[0055] The reference surface 124C uses, for example, a reflection mirror and reflects the reference light L2 incident from the beam splitter 124B toward the beam splitter 124B. This reference surface 124C can be manually adjusted in the Y direction by a position adjustment mechanism (for example, a ball screw mechanism, an actuator, etc.) not shown. Thereby, the optical path length (reference optical path length) of the reference light L2 can be adjusted.

[0056] The beam splitter 124B generates a combined light L3 of the measurement light L1 returning from the surface to be measured and the reference light L2 returning from the reference surface 124C, and emits this combined light L3 toward the objective lens 124A on the left side in the Z direction. This combined light L3 passes through the objective lens 124A and the beam splitter 122 and is incident on the imaging lens 126.

[0057] The imaging lens 126 forms an image of the combined light L3 incident from the beam splitter 122 on the imaging surface (not shown) of the camera 128. Specifically, the imaging lens 126 forms an image of a point on the focal plane of the objective lens 124A as an image point on the imaging surface of the camera 128.

[0058] The camera 128 has a CCD (Charge Coupled Device) type or CMOS (Complementary Metal Oxide Semiconductor) type imaging element, although not shown. The camera 128 images the combined light L3 formed on the imaging surface of the imaging element by the imaging lens 126, and processes the imaging signal of the combined light L3 obtained by this imaging to output an imaging signal. The camera 128 is an example of an imaging unit.

[0059] The optical unit drive unit 106 is composed of various actuators such as a linear motor or a motor drive mechanism, and holds the optical unit 104 movably in the Z direction, which is the scanning direction. Under the control of the control device 110, this optical unit drive unit 106 scans the optical unit 104 in the Z direction, that is, along the direction parallel to the optical axis R of the optical unit 104. The optical unit drive unit 106 is an example of a relative movement unit.

[0060] In addition, the optical unit drive unit 106 holds the optical unit 104 movably not only in the Z direction but also in the Y direction and the X direction. Thereby, it becomes possible to adjust the relative position (relative positions in the X direction and the Y direction) of the optical unit 104 with respect to the end portion of the wafer to be measured. Also, when there is a limitation in the measurement field of the surface to be measured that can be measured at one time due to limitations such as the measurement field of the interference objective lens 124, it becomes possible to perform a plurality of measurements while moving the optical unit 104 in the X direction or the Y direction. Note that instead of moving the optical unit 104 in the X, Y, or Z direction, the measurement table 102 may be moved in the X, Y, or Z direction.

[0061] The scale 130 is a position detection sensor that detects the Z-direction position of the optical unit 104, and for example, a linear scale is used. This scale 130 repeatedly detects the Z-direction position of the optical unit 104 and repeatedly outputs the position detection result to the control device 110.

[0062] FIG. 6 is a functional block diagram of the control device 110 in the shape measurement device 100. The control device 110 is connected to the light source unit 120 and the camera 128 of the optical unit 104, the scale 130, the table drive unit 116, the optical unit drive unit 106, the operation unit 112, and the output unit 114.

[0063] The operation unit 112 includes an input device (for example, a keyboard and a mouse, etc.) for receiving an operator's operation input to the control device 110.

[0064] The output unit 114 is a device for outputting the execution results of programs, data of calculation results, etc. by the control device 110. The output unit 114 includes, for example, an operation UI (User Interface) and a monitor (e.g., a liquid crystal display, etc.) for displaying detection results. Further, the output unit 114 may include a printer, a speaker, etc. in addition to or instead of the monitor.

[0065] The control device 110 controls the measurement operation of the three-dimensional shape of the surface to be measured (edge portion 80 or notch portion 82) by the shape measurement device 100 in response to an operation input from the operation unit 112, and performs operations such as calculation of the three-dimensional shape of the surface to be measured. The control device 110 includes a processor (e.g., a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc.) that executes various calculations, a memory (e.g., a ROM (Read Only Memory) and a RAM (Random Access Memory), etc.) that serves as a working area for the processor, and a storage device (e.g., an SSD (Solid State Drive) or an HDD (Hard Disk Drive), etc.) for storing various programs and data.

[0066] The control device 110 functions as a measurement control unit 160, a calculation unit 162, and an analysis unit 164 by executing the program stored in the storage device by the processor.

[0067] The measurement control unit 160 controls the table drive unit 116, the optical unit drive unit 106, the light source unit 120, and the camera 128 to repeatedly image the measured surface (edge portion 80 or notch portion 82) of the object to be measured by the camera 128 at a constant pitch while scanning the optical unit 104 in the scanning direction (Z direction). Specifically, the measurement control unit 160 controls the table drive unit 116 to rotate the measurement table 102 so that the measured surface (edge portion 80 or notch portion 82) of the object to be measured faces the optical unit 104. Further, after starting the emission of the measurement light L1 from the light source unit 120, the measurement control unit 160 controls the optical unit drive unit 106 to scan the optical unit 104 in the Z direction. Also, while the optical unit drive unit 106 scans the optical unit 104 in the Z direction, the measurement control unit 160 repeatedly executes imaging of the combined light L3 by the camera 128 and output of the captured image to the control device 110 each time the optical unit 104 moves by a constant pitch in the Z direction based on the detection result of the Z-direction position of the optical unit 104 by the scale 130.

[0068] Each time the camera 128 images the combined light L3, the calculation unit 162 acquires the captured image output from the camera 128 and generates three-dimensional shape data of the measured surface of the object to be measured. Specifically, the calculation unit 162 compares the luminance values of the pixels at the same coordinates of each captured image. Next, the calculation unit 162 determines the Z-direction position where the luminance value is maximized for each pixel at the same coordinates of each captured image, thereby calculating height information indicating the height position (Z-direction position) of each part of the measured surface corresponding to each pixel. Thereby, three-dimensional shape data indicating the three-dimensional shape (height distribution) of the measured surface is generated.

[0069] Based on the three-dimensional shape data of the surface to be measured generated by the arithmetic unit 162, the analysis unit 164 performs shape analysis on the edge portion 80 (for example, the notch portion 82) of the wafer W. The analysis unit 164 determines, for example, the quality of the shape of the notch portion 82 based on the three-dimensional shape of the notch portion 82. Specifically, the analysis unit 164 determines that there is a defect such as a scratch when there is a portion that deviates from the design value of the notch portion 82 by a threshold value or more, a stepped shape, or a portion where a roughness parameter (for example, surface roughness (ISO 25178-2), etc.) is equal to or greater than the threshold value.

[0070] [Notch Shape Measurement] FIG. 7 is a diagram for explaining the procedure of measuring the shape of the notch portion 82. FIG. 7(a) is a plan view of the wafer W, and FIG. 7(b) is an enlarged plan view showing the VIIb portion of FIG. 7(a). Further, FIG. 7(c) is a cross-sectional view showing the YZ cross-section (plane X = x i ) of the notch portion 82.

[0071] In the present embodiment, the analysis unit 164 obtains the shape of the notch portion 82 shown in FIG. 7(c) (for example, the apex in the Z direction (coordinates of the point where the Z coordinate is the maximum), etc.). Then, based on the obtained shape of the notch portion 82, shape analysis of the notch portion 82 (for example, determination of the quality of the shape of the notch portion 82, detection of defects such as scratches, etc.) is performed.

[0072] By the way, random noise-like components may be added to the measurement data Di of the coordinates of the surface of the notch portion 82 measured by the shape measurement device 100. The example shown in FIG. 7(d) shows an example of the locus obtained from the measurement data Di (X = x i ) as viewed from the Z direction. In the example shown in FIG. 7(d), the locus obtained from the measurement data Di does not form a smooth curve (including a straight line, a line segment, and a half-line), and the influence of random noise-like components appears.

[0073] Therefore, in the present embodiment, as shown in FIG. 7(e), an approximate curve Li (including a straight line, a line segment, and a half-line) is calculated from the measurement data Di, and shape analysis of the notch portion 82 is performed.

[0074] When measuring the shape of the notch portion 82, it is assumed that the wafer W alignment process and the process of determining the position (angular position) of the notch portion 82 by the orifice-notch detection sensor have been completed in advance.

[0075] Here, in the alignment process, the center C0 of the wafer W is made to coincide with the center (rotation axis G) of the measurement table 102. The alignment process is performed, for example, using a diameter measuring device including a camera (for example, an imaging element such as a CCD or CMOS). Specifically, the wafer W is placed on the measurement table 102 and imaged while being rotated. The analysis unit 164 detects the change in the position of the edge portion 80 of the wafer W from the captured images for each rotation angle. The analysis unit 164 obtains the distance between the center (G) of the measurement table 102 and each endpoint of the plurality of edge portions 80 detected for each rotation angle, and based on these distances, calculates the diameter of the wafer W and the amount of misalignment of the center C0 of the wafer W with respect to the center (rotation axis G) of the measurement table 102. Thereby, the alignment of the center C0 of the wafer W and the center (rotation axis G) of the measurement table 102 can be performed.

[0076] First, a coordinate system (hereinafter referred to as the analysis coordinate system) for analyzing the notch portion 82 is created. For example, the analysis unit 164 acquires the front or back surface of the wafer W (approximate plane. For example, the surface obtained by least squares approximation from the coordinates of the front or back surface of the wafer W), and creates an analysis coordinate system based on the front or back surface of the wafer W. Specifically, the direction orthogonal to the front or back surface of the wafer W can be defined as the Y direction. Also, regarding the rotation around the Y axis, for example, the Z direction of the shape measurement device 100 can be defined as the Z direction of the analysis coordinate system. Thereby, the XYZ directions of the analysis coordinate system can be defined.

[0077] Next, focusing on a certain YZ cross-section (plane X = x i ), the maximum value of the Z coordinate and the Y coordinate at that time are acquired from the measurement data Di by the shape measurement device 100. Note that the calculation of the maximum value may be performed after applying a filter.

[0078] In addition, when there is design information or the like regarding the shape of the tip of the notch portion 82, fitting of the measurement data Di may be performed using the shape based on the design information or the like, and the apex of the approximate curve Li obtained by the fitting may be determined. For example, as shown in FIG. 7(c), when there is design information regarding the Z-direction region (e.g., design dimension z c ) of the notch portion 82, the measurement range of the actual shape by the shape measuring device 100 (or the extraction range of the measurement data Di from the measurement results by the shape measuring device 100) may be limited to the range defined by the design dimension z c .

[0079] Hereinafter, an example of approximating the measurement data Di with a quadratic curve will be described. For example, the approximate curve near the apex in the Z direction of the notch portion 82 is set as Z = -k(Y - a) 2 +b, and the parameters k, a, and b are determined by performing approximation (e.g., the least squares method) of the measurement data Di. Here, the parameter a is the coordinate of the apex in the Z direction.

[0080] The point sequence obtained by measuring the shape of the notch portion 82 along the plane X = x i (i = 1 to nx) is set as (x1, y1, z1),…,(x i , y i , z i ),…,(x nx , y ny , z nz ). The least squares curve Li (i = 1 to nx) is obtained from this point sequence. For simplicity, it is assumed that there are points on the plane X = x i . However, when there are no points on the plane X = x i , points on the plane X = x i may be calculated by interpolation or extrapolation from nearby points.

[0081] The obtained least squares curve Li (i = 1 to nx) is represented as (x i , y 2,1 , z 2,1 ),…,(x i , y 2,i , z 2,i ),…,(x i , y 2,ny , z 2,nz) shall be used.

[0082] In addition, the point sequence (x i , y 2,1 , z 2,1 ),…,(x i , y 2,i , z 2,i ),…,(x i , y 2,ny , z 2,nz ) obtained in the above example shows an example of regressing Y on Z (linear regression), but the method for obtaining the approximate curve is not limited to this.

[0083] In addition, the object of shape measurement and shape analysis is not limited to the notch portion 82. For example, the shape measurement according to the present embodiment can also be applied to the edge portion 80 of the wafer W where the notch portion 82 is not formed, or an orifice or the like.

[0084] [Example 1 of Shape Analysis] In the present embodiment, the shape analysis of the notch portion 82 is performed using the least-squares curve Li obtained as described above. For example, the least-squares curve Li is compared with the design value of the notch portion 82 of the wafer W. Note that, as the object to be compared with the least-squares curve Li, instead of or in addition to the design value, the result of measuring a wafer master workpiece with known shape and dimensions, or the measurement result by the optical projection measurement method described in Patent Document 2 may be used. Further, a process of superimposing (best-fit process) the least-squares curve Li and the object to be compared may be performed to compare the shapes of both.

[0085] When the above comparison result does not satisfy a predetermined standard (for example, when it exceeds a threshold value), the analysis unit 164 determines that there is an abnormality (NG) in the notch portion 82. Then, the analysis unit 164 outputs the determination result to the output unit 114 (for example, performs monitor display or voice guidance).

[0086] For example, the analysis unit 164 determines a plane X = x obtained from the least-squares curve Li iWhen the difference or absolute value of the difference between the position (Y coordinate) of the vertex in the Z direction and the design value in is greater than or equal to the threshold value, it may be determined that there is an abnormality (NG) in the notch portion 82, and when it is less than the threshold value, it may be determined that there is no abnormality (OK).

[0087] Also, when obtaining the least-squares curve Li, the calling shape may be removed by the least-squares method, or after applying a short-wavelength pass filter with an appropriate length, roughness parameter analysis (ISO21920-2, ISO12085 (ISO: International Organization for Standardization), etc.) may be performed.

[0088] [Example 2 of Shape Analysis] FIG. 8 is a perspective view for explaining the shape analysis according to Example 2.

[0089] In Example 1, attention was paid to the plane X = x i Similarly, if attention is paid to the plane Y = y k (k = 1 to ny), the point sequence (x 3,i , y k , z 3,1 ),…, (x 3,i , y k , z 3,i ),…, (x nx , y k , z 2,nz ) corresponding to the curve Ls can be obtained, and the following processes (1) to (3) are performed on this curve. The plane Y = y k corresponding to the curve Ls may use the parameter a of Example 1, but design information can also be used, and it is not limited thereto.

[0090] (1) For the curve Ls corresponding to the above point sequence, cross-sections shifted by α and β in the Y direction respectively and the cross-section of the original shape are obtained. In FIG. 8, two curves Lα and Lβ shifted with respect to the curve Ls are obtained, but the number of shifted curves is not limited to two and may be three or more.

[0091] (2) Determine the lowest points (points with the minimum Z - coordinate) P0, Pα, and Pβ in the Z - direction on the three curves Ls, Lα, and Lβ.

[0092] Here, the deviation amounts α and β may be manually inputtable, for example, by causing the user interface illustrated in FIG. 9 to be displayed on the output unit 114. Also, the deviation amounts α and β may be automatically set by the analysis unit 164. For example, when the reference curve Ls is biased near the front or back surface of the wafer W, the deviation amounts α and β may be set so that the three curves are not biased with respect to the center in the thickness direction of the wafer W, or the number of curves may be increased. For example, when the curve Ls is close to the front surface of the wafer W, the curves Lα and Lβ may be set near the back surface and near the saddle point SP (see FIG. 10).

[0093] (3) Obtain a curve LY that connects the three points P0, Pα, and Pβ. Here, the curve L1 is obtained, for example, by polynomial approximation, piecewise polynomial approximation, or B - spline curve, etc.

[0094] Through the above analysis, a curve LY of the outer peripheral surface along the direction (Y - direction) substantially perpendicular to the front or back surface of the wafer W passing through the saddle point SP of the notch portion 82 can be obtained.

[0095] In the second embodiment, shape analysis of the notch portion 82 is performed using the curve LY obtained as described above. For example, comparison between the curve LY and the design value of the notch portion 82 of the wafer W is performed. Note that as the object to be compared with the curve LY, instead of or in addition to the design value, the result of measuring a wafer master workpiece with known shape and dimensions, or the measurement result by the optical projection measurement method described in Patent Document 2 may be used. Also, a process of superposing (best - fit process) the curve LY and the object to be compared may be performed to compare the shapes of both.

[0096] When the above matching result does not meet a predetermined standard (for example, when it exceeds a threshold value), the analysis unit 164 determines that there is an abnormality (NG) in the notch portion 82. Then, the analysis unit 164 outputs the determination result to the output unit 114 (for example, performs monitor display or voice guidance).

[0097] For example, when the difference or absolute value of the difference between the position (Y coordinate) of the saddle point obtained from the curve LY and the design value is greater than or equal to the threshold value, the analysis unit 164 may determine that there is an abnormality (NG) in the notch portion 82, and when it is less than the threshold value, determine that there is no abnormality (OK).

[0098] Also, when obtaining the least squares curve Li and the curve LY, the call shape may be removed by the least squares method, or after applying a short-wavelength pass filter with an appropriate length, roughness parameter analysis (ISO21920-2, ISO12085, etc.) may be performed.

[0099] [Modification Example of Example 2 of Shape Analysis] In Example 2, as shown in FIG. 10, curves LX and LY in the XY2 direction passing through the saddle point SP can be obtained. Then, by performing interpolation or extrapolation using the curves LX and LY, the surface shape of the region specified with the region including the saddle point SP etc. as the reference (center) can be generated, and the generated region can be extracted.

[0100] This region may be manually inputtable, for example, by causing the output unit 114 to display a user interface exemplified in FIG. 11 with the XY direction range centered on the saddle point SP. Note that the region designation may be set as a strip-shaped region based on the curve LX or LY by leaving ±X or ±Y blank. Also, instead of numerical input, it may be possible to specify by displaying the shape of the saddle portion in FIG. 10 with a pointing device such as a mouse.

[0101] In the area designation based on the saddle point SP of the second embodiment, the area is designated to be rectangular when considered on the projection plane onto the XY plane, but it is not limited to this. For example, an area of any shape other than rectangular (e.g., a polygon, a circle, or an oval shape (e.g., an ellipse, an oblong, etc.)) may be designated when considered on the projection plane onto the XY plane. Specifically, the radius of the circle or the major and minor axes of the oval shape based on the saddle point SP may be numerically input. Also, a UI (e.g., a button or an icon) for selecting the shape of the area (e.g., a rectangle, a polygon, an oval shape, or an arbitrary shape) may be provided, and the area of the selected shape may be designated using a pointing device.

[0102] Also, the area designation is not limited to the example of being based on the projection plane onto the XY plane. For example, the area may be designated three-dimensionally. For example, the area may be designated using three-dimensional coordinates. Also, the area may be designated by specifying the voxels of the three-dimensional image displayed on the output unit 114 using a pointing device.

[0103] Shape analysis of the notch portion 82 is performed using the surface shape of the notch portion 82 of the area extracted as described above. For example, the extracted area is compared with the design value of the notch portion 82 of the wafer W. Note that, as the object to be compared with the extracted area, instead of or in addition to the design value, the result of measuring a wafer master workpiece with known shape and dimensions or the measurement result by the optical projection measurement method described in Patent Document 2 may be used. Also, a process of overlapping (best fit process) the curve LY and the object to be compared may be performed to compare the shapes of both. Also, not limited to the notch portion 82, shape analysis of area data obtained by extracting a desired area from the three-dimensional shape of the end portion of the wafer W may be performed.

[0104] When the above comparison result does not meet a predetermined standard (e.g., exceeds a threshold value), the analysis unit 164 determines that there is an abnormality (NG) in the notch portion 82. Then, the analysis unit 164 outputs the determination result to the output unit 114 (e.g., performs monitor display or voice guidance).

[0105] Alternatively, after removing the call shape from the extracted area using the design values, or after applying a short-wavelength pass filter of an appropriate length, the surface shape may be digitized and collated using three-dimensional surface texture parameters (ISO 25178-2) or the like.

[0106] According to the present embodiment, by using the shape measuring device 100, it becomes possible to analyze the shape of the notch portion 82 (saddle portion), and it becomes possible to digitize the shape or roughness of the saddle portion. Further, by digitizing the shape or roughness of the saddle portion, it becomes possible to determine the presence or absence of an abnormality (pass / fail determination) of the notch portion 82 based on a threshold value. Also, analysis and pass / fail determination similar to the light projection measurement method are also possible.

[0107] Furthermore, in the present embodiment, numerical values are recorded for a plurality of wafers W. If wafers W showing the same tendency of numerical value abnormalities continue, it can be determined that there is a problem with the grinding wheel. The detection of abnormalities in the grinding wheel is particularly effective for portions that are shaded in the light projection measurement method. And it is also possible to feedback the results of the detection of abnormalities in the grinding wheel and the like to the processing conditions.

[0108] [Others] In the above shape analysis, in addition to the measurement data Di of the notch portion 82 (saddle portion), data on the front or back surface of the wafer W is used. When the tilt sensitivity of the shape measuring device 100 is low, it is difficult to simultaneously acquire the measurement data of the saddle portion and the data of the front or back surface.

[0109] FIG. 12 is a perspective view showing an example of determining an analysis coordinate system using a master workpiece. As shown in FIG. 12, the master workpiece M is placed on the measurement table 102 instead of the wafer W. The master workpiece M is a workpiece in which the angles between the respective surfaces constituting the master workpiece M are known, and for example, a right angle gauge or the like can be used. The master workpiece M is fixed on the measurement table 102 by, for example, suction or its own weight.

[0110] If the master workpiece M is, for example, substantially rectangular parallelepiped in shape, it is installed with one face's normal direction substantially directed towards the center (rotation axis G) of the measurement table 102. Also, the rotation axis G of the measurement table 102 and the Y direction of the optical unit 104 are made substantially coincident (substantially parallel). Further, the position of the optical unit 104 in the Y direction is adjusted so that the optical unit 104 faces the surface to be measured of the master workpiece M. Also, the angle of the rotation axis of the optical unit 104 at which the reflected light to the optical unit 104 becomes maximum is adjusted.

[0111] After the above adjustments, the master workpiece M is measured. Specifically, while scanning the optical unit 104 in the Z direction, based on the captured images captured by the camera 128 at predetermined pitches, the coordinates of a plurality of points on the surface to be measured of the master workpiece are detected. Then, a least-squares plane is calculated from the coordinates of the point group composed of this plurality of points, and the XY plane is defined from the least-squares plane of the master workpiece M. Regarding the degree of freedom of rotation in the Z-axis direction, for example, the Y direction of the shape measurement device 100 can be defined as the Y direction of the analysis coordinate system. Thereby, the analysis coordinate system can be defined.

[0112] Note that since the rotation axis G of the measurement table 102 and the Y direction of the shape measurement device 100 are substantially coincident (substantially adjusted in parallel), even if the Y direction of the shape measurement device 100 is defined as the Y direction of the analysis coordinate system, no practical problems in the above shape analysis occur. Also, when collating with design values etc., since a best fit is performed with the surface shape (measured shape) of the notch portion 82, no practical problems in the above shape analysis occur.

[0113] Here, if the edge portion ME of the master workpiece M (for example, data near the edge) is included in the measurement range MR by the shape measurement device 100, as shown in FIG. 13, the data near the edge may be removed to obtain the least-squares plane MS (XY plane).

[0114] As described above, by using the master workpiece M with known angles between each face, the XY plane can be defined even when it is difficult to obtain data on the front or back surface of the wafer W.

[0115] In the above-described embodiment, in the measurement unit 20, a configuration including a shape measurement device having a white light interference microscope has been described as an example. However, the present invention is not limited thereto. For example, a shape measurement device having a microscope such as a focus variation method microscope or a laser confocal method microscope may be provided.

[0116] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above examples, and various improvements and modifications may of course be made without departing from the gist of the present invention.

Explanation of Reference Numerals

[0117] 10... Wafer processing system, 12... Cassette unit, 14... Loading unit, 16... Grinding unit, 18... Cleaning unit, 20... Measurement unit, 22... Transfer unit, 30... Grinding device, 32... Grinding table, 32a... Holding surface, 34... Grinding wheel, 34a... Grinding groove, 36... Spindle motor, 80... Edge portion, 82... Notch portion, 100... Shape measurement device, 102... Measurement table, 102a... Holding surface, 104... Optical unit, 106... Optical unit drive unit, 110... Control device, 112... Operation unit, 114... Output unit, 116... Table drive unit, 120... Light source unit, 122... Beam splitter, 124... Interference objective lens, 124A... Objective lens, 124B... Beam splitter, 124C... Reference surface, 126... Imaging lens, 128... Camera, 130... Scale, 160... Measurement control unit, 162... Calculation unit, 164... Analysis unit

Claims

1. A shape measurement device for measuring the shape of a measurement surface at an end of a wafer, an optical unit having a light axis parallel to the main surface of the wafer and irradiating measurement light along the light axis onto the measurement surface, and an imaging unit for imaging reflected light from the measurement surface; a relative movement unit for relatively moving the optical unit with respect to the measurement surface; an arithmetic unit that generates measurement data indicating the shape of the notch portion based on the coordinates of a point group obtained by repeatedly imaging the notch portion formed on the measurement surface by relatively moving the optical unit; an analysis unit that performs shape analysis of the notch portion based on the measurement data; A shape measurement device comprising:

2. The shape measurement device according to claim 1, wherein the analysis unit obtains an approximate curve from the coordinates of the point group.

3. The imaging unit images the notch portion of the wafer to obtain the coordinates of the point group, The shape measurement device according to claim 2, wherein the analysis unit calculates at least two curves obtained by shifting the approximate curve along a direction orthogonal to the front surface or the back surface of the wafer, thereby obtaining an approximate curve of the notch portion along a direction orthogonal to the front surface or the back surface of the wafer passing through the saddle point of the notch portion.

4. The shape measurement device according to any one of claims 1 to 3, further comprising an output unit that outputs a determination result on the presence or absence of an abnormality of the wafer based on the measurement data.

5. The shape measurement device according to any one of claims 1 to 3, wherein the analysis unit determines the presence or absence of an abnormality in the three-dimensional shape corresponding to the region data based on the region data extracted from the three-dimensional shape of the end of the wafer.

6. The analysis unit relatively moves the optical unit with respect to a master workpiece whose angles between respective surfaces are known, and determines an analysis coordinate system for analysis of the notch portion based on the coordinates of a point group obtained by repeatedly imaging the surface to be measured of the master workpiece by the imaging unit. The shape measurement apparatus according to any one of claims 1 to 3.

7. A shape measurement method for measuring the shape of a surface to be measured at an end portion of a wafer, comprising: an optical unit having a light source unit that has an optical axis parallel to the main surface of the wafer and irradiates measurement light along the optical axis onto the surface to be measured, and an imaging unit that images reflected light from the surface to be measured; when the optical unit is relatively moved with respect to the surface to be measured, generating measurement data indicating the shape of the notch portion based on the coordinates of a point group obtained by repeatedly imaging the notch portion formed on the surface to be measured by the imaging unit, and performing shape analysis of the notch portion based on the measurement data. A shape measurement method.

Images