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 measure the three-dimensional shape of a measurement surface on an edge of a wafer with good accuracy.SOLUTION: A shape measuring device 100 comprises: an optical unit 104 including a light source part 120 for irradiating a measurement surface T with measurement light L1 along an optical axis R parallel to the principal surface of a wafer W, and a camera 128 for imaging reflected light from the measurement surface and provided coaxially with the optical axis R; an optical unit drive part 106 for moving the optical unit 104 relatively to the measurement surface T in a direction along the optical axis R; a side face illumination unit 108 for irradiating the measurement surface T with side face illumination light M from a direction orthogonal to the optical axis R; and a control device 110 (shape data generation part 162) for generating three-dimensional shape data indicating the three-dimensional shape of the measurement surface T on the basis of a plurality of captured images that the camera 128 repeatedly captured while the optical unit 104 was making relative movement.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a shape measuring apparatus and a shape measuring method for measuring the three-dimensional shape of a measurement surface at an end portion of a wafer.

Background Art

[0002] Semiconductor wafers such as silicon wafers (hereinafter referred to as "wafers") on which semiconductor devices and the like are formed may be damaged or chipped due to contact with other members. Furthermore, due to such scratches and chips, the wafer may crack. Therefore, in the manufacturing process of the wafer, chamfering is performed by grinding the end portion of the wafer.

[0003] As shown in FIG. 17, an edge portion 80 is formed along the circumferential direction of the outer peripheral edge at the end portion of the chamfered wafer W, and a notch portion 82, which is a cutout portion, is formed in a part of the circumferential direction of the outer peripheral edge. Further, the edge portion 80 and the notch portion 82 have a chamfered portion 84 that has been chamfered. The notch portion 82 has a substantially U-shaped or substantially V-shaped configuration as shown in the enlarged view shown in the upper left of FIG. 17, and is roughly divided into straight portions 82a, 82a on both sides and a bottom portion 82b. Here, the bottom portion 82b is a portion that is located on the back side within the notch portion 82 and is configured in a curved shape having a predetermined curvature. The straight portions 82a, 82a are linear portions each having one end connected to both ends of the bottom portion 82b. The other end of each of the straight portions 82a, 82a is connected to the edge portion 80 that constitutes the outer peripheral edge of the wafer W.

[0004] As shown in the enlarged view at the lower right of FIG. 17, the cross-sectional shape of the edge portion 80 is provided with an inclined surface S and a flat surface F. Specifically, on the upper surface Wu side and the lower surface Wd side of the wafer W, two inclined surfaces S, S that are inclined obliquely with respect to the thickness direction of the wafer W are formed, and between the two inclined surfaces S, S, a flat surface F substantially perpendicular to the thickness direction of the wafer W is formed. Although not shown, the cross-sectional shape of the notch portion 82 is also the same as the cross-sectional shape of the edge portion 80. Here, as an example of the cross-sectional shapes of the edge portion 80 and the notch portion 82, the cross-sectional shape shown in FIG. 17 is shown, but it is not limited to this, and there may be cases of a round shape with rounded corners or other shapes.

[0005] By the way, in the manufacturing process of the wafer, it is important to confirm that there are no scratches or chips on the edge of the chamfered wafer, and to correctly measure the shape of the edge and confirm that the shape is within the allowable error range with respect to the designed shape.

[0006] For example, Patent Document 1 discloses a shape measuring device that measures the shape of the edge of a wafer by a light projection measurement method. This shape measuring device projects light onto the edge of the chamfered wafer from directions substantially parallel to the front and back surfaces of the wafer, and images the projected image of the edge of the wafer with a camera from a direction opposite to the light projection direction, and measures the shape of the edge of the wafer based on the projected image. The contour of the projected image obtained by this method is the cross-sectional shape of the edge of the wafer (the shape of the cross-section cut in the thickness direction).

[0007] In addition, Patent Document 2 discloses a three-dimensional shape measurement device that optically measures three-dimensional shapes such as the surface shape and surface roughness shape of the surface to be measured of the object to be measured. This three-dimensional shape measurement device measures the three-dimensional shape of the surface to be measured by using both the WLI (White Light Interferometry) method (white light interference method) and the FV (Focus Variation) method (focus variation method, autofocus method) based on a plurality of captured images captured by a camera at regular pitches while scanning a white light interference microscope in the vertical direction (Z direction) with respect to the surface to be measured.

[0008] Here, the WLI method is a method of calculating three-dimensional shape data indicating the height information of the surface to be measured of the object to be measured based on the Z-direction position where the luminance value is maximum in the Z direction for each pixel at the same coordinates of each captured image. The FV method calculates the focus degree for each pixel of each captured image, and calculates three-dimensional shape data indicating the height information of the surface to be measured of the object to be measured based on the Z-direction position where the focus degree is maximum for each pixel at the same coordinates of each captured image.

[0009] The WLI method has the advantage that the resolution in the height direction of the surface to be measured is high (below nm), and it is good at measuring the roughness of a surface that is nearly perpendicular to the scanning direction (Z direction) parallel to the optical axis of the white light interference microscope (interference objective lens). However, it has the disadvantage that the measurement sensitivity for an inclined surface inclined with respect to the scanning direction is low. On the other hand, the FV method has the disadvantage that the resolution in the height direction of the surface to be measured is lower than that of the WLI method, but it has the advantage that the measurement sensitivity for an inclined surface is high and it is good at measuring the shape of an inclined surface.

[0010] In the three-dimensional shape measurement device disclosed in Patent Document 2, taking advantage of the advantages of the two methods, among the three-dimensional shape calculation results by the WLI method and the three-dimensional shape calculation results by the FV method, the one with higher accuracy is selected for each pixel to generate the three-dimensional shape data of the surface to be measured.

Prior Art Documents

Patent Documents

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-4341 [Patent Document 2] Japanese Patent Application Laid-Open No. 2023-139925 [Summary of the Invention] [Problems to be Solved by the Invention]

[0012] In the shape measurement device disclosed in Patent Document 1, since the light projection measurement method is used, in principle, shape data cannot be obtained for the portions that are in shadow when viewed from the camera. Therefore, even if there are scratches or chips at the edges of the wafer, they may not be detected. Also, surface roughness is one of the important judgment factors in checking the quality of the edges of the wafer, but the light projection measurement method cannot measure surface roughness.

[0013] On the other hand, in order to measure the three-dimensional shape of the chamfered end portion (edge portion or notch portion) of the wafer, it is conceivable to apply the three-dimensional shape measurement device disclosed in Patent Document 2. However, this three-dimensional shape measurement device has the following problems.

[0014] As shown in FIG. 18, the white interference microscope 900 used in the three-dimensional shape measurement device disclosed in Patent Document 2 images the measurement surface 902 by the coaxial epi-illumination method. The coaxial epi-illumination method is an illumination method in which the optical axis of the illumination light (measurement light) irradiated onto the measurement surface 902 coincides with the optical axis of the white interference microscope 900 (the optical axis of the camera) to obtain the reflected light from the measurement surface 902 of the measurement object.

[0015] The three-dimensional shape measurement device disclosed in Patent Document 2 calculates three-dimensional shape data by using both the WLI method and the FV method. However, as shown in FIG. 18, when the measured surface 902 has a mixture of flat surfaces and inclined surfaces, it is necessary to irradiate the inclined surface with illumination light as uniformly as possible. If the intensity of the reflected light that is reflected from the inclined surface and travels toward the camera of the white light interference microscope 900 becomes non-uniform, the sensitivity will be insufficient in the region of low reflected light (the inclined surface). In that case, in the FV method, the calculation accuracy of the three-dimensional shape data of the inclined surface may decrease, or the calculation itself may become impossible. In this case, it is necessary to adjust the gain and integration time of the camera in order to keep the maximum intensity of the reflected light on the inclined surface within the dynamic range.

[0016] However, if such adjustment is made, in the illumination light by the coaxial epi-illumination method, in the captured image 904 captured by the camera of the white light interference microscope 900, in the portion corresponding to the flat surface (the region of regular reflection) that is the facing part of the white light interference microscope 900, the reflected light becomes too strong and becomes a bright part (high luminance part), and the sensitivity of the other part, that is, the part corresponding to the inclined surface, is insufficient and becomes a dark part. In this case, in the WLI method, the information of the interference fringes at the location where the intensity of the reflected light is high (that is, the facing part) in the captured image 904 cannot be obtained (that is, it exceeds the preset measurement range), and the calculation accuracy of the three-dimensional shape data decreases.

[0017] Thus, there is room for improvement in applying the three-dimensional shape measurement device disclosed in Patent Document 2 to the measurement of the three-dimensional shape of the measured surface at the end (edge part or notch part) of the chamfered wafer.

[0018] The present invention has been made in view of such circumstances, and an object thereof is to provide a shape measurement device and a shape measurement method capable of accurately measuring the three-dimensional shape of the measured surface at the end of a wafer.

Means for Solving the Problems

[0019] The present invention comprises the following aspects in order to achieve the above object.

[0020] The shape measurement device according to the first aspect is a shape measurement device that measures the three-dimensional shape of the measurement surface at the end of a wafer, and has an optical axis parallel to the main surface of the wafer, and a light source unit that irradiates coaxial incident illumination light along the optical axis onto the measurement surface, and an imaging unit that is provided coaxially with the optical axis and images the reflected light from the measurement surface. It includes an optical unit, a relative movement unit that relatively moves the optical unit in a direction along the optical axis with respect to the measurement surface, a side illumination unit that irradiates side illumination light onto the measurement surface from a direction orthogonal to the optical axis, and based on a plurality of captured images repeatedly captured by the imaging unit while the optical unit is relatively moving, a shape data generation unit that generates three-dimensional shape data indicating the three-dimensional shape of the measurement surface.

[0021] The shape measurement device according to the second aspect is, in the first aspect, the side illumination unit has a rod-shaped light emitter with the longitudinal direction being the direction parallel to the optical axis.

[0022] The shape measurement device according to the third aspect is, in the second aspect, the side illumination unit has a pair of rod-shaped light emitters provided on both sides in the direction orthogonal to the optical axis with the end of the wafer sandwiched therebetween.

[0023] The shape measurement device according to the fourth aspect is, in the first aspect, provided with a light amount control unit that controls the light amount of the side illumination light irradiated from the side illumination unit.

[0024] The shape measurement device according to the fifth aspect is, in the third aspect, provided with a light amount control unit that independently controls the light amounts of the side illumination light emitted by the pair of rod-shaped light emitters.

[0025] The shape measurement device according to the sixth aspect is, in the first aspect, the side illumination unit has a planar light emitter that emits light in a planar shape parallel to the main surface.

[0026] The shape measurement device according to the seventh aspect is, in the first aspect, has a measurement table that holds the wafer and is configured to be rotatable about a rotation axis orthogonal to the main surface of the wafer, and a measurement control unit that rotates the measurement table so that the measurement surface at the end of the wafer is positioned at a position facing the optical unit.

[0027] In the shape measurement apparatus according to the eighth aspect, in any one of the first aspect to the seventh aspect, the shape data generation unit includes: a first shape data generation unit that generates first shape data indicating the three-dimensional shape of the measurement surface by a white interference method based on a plurality of captured images; a second shape data generation unit that generates second shape data indicating the three-dimensional shape of the measurement surface by a focus variation method based on a plurality of captured images; and an integration calculation unit that generates integrated shape data in which the first shape data and the second shape data are selectively combined pixel by pixel or region by region based on an index value obtained from at least one of the first shape data and the second shape data.

[0028] The shape measurement method according to the ninth aspect is a shape measurement method for measuring the three-dimensional shape of a measurement surface at an end portion of a wafer, including: a scanning step of relatively moving an optical unit having an optical axis parallel to the main surface of the wafer in a direction along the optical axis with respect to the measurement surface; an imaging step of irradiating the measurement surface with coaxial incident illumination light along the optical axis from the optical unit while the scanning step is being performed, and imaging reflected light from the measurement surface by an imaging unit provided coaxially with the optical axis in the optical unit; a side illumination step of irradiating the measurement surface with side illumination light from a direction orthogonal to the optical axis while the imaging step is being performed; and a shape data generation step of generating three-dimensional shape data indicating the three-dimensional shape of the measurement surface based on a plurality of captured images captured by the imaging unit in the imaging step.

Advantages of the Invention

[0029] According to the present invention, the three-dimensional shape of the measurement surface at the end portion of the wafer can be accurately measured.

Brief Description of the Drawings

[0030]

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Figure 18

Embodiments for Carrying Out the Invention

[0031] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0032] 〔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 indicate horizontal directions, and the Y direction indicates the vertical direction (perpendicular direction).

[0033] 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 measurement unit 20, and a transfer unit 22.

[0034] 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 measurement 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.

[0035] 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.

[0036] The grinding unit 16 performs grinding of the edge of the wafer W, that is, from rough grinding to finish grinding.

[0037] 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.

[0038] The grinding table 32 has a holding surface 32a for sucking and holding the wafer W on its upper surface. 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).

[0039] 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 moves forward, the rotating grinding wheel 34 is relatively pressed against the outer peripheral portion (edge portion 80 (see FIG. 17)), 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.

[0040] The grinding device 30 is provided with, in addition to the above-mentioned 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. 17). 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.

[0041] 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.

[0042] 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 movement in the Z direction and lifting movement 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. Thus, 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.

[0043] The measuring unit 20 measures the thickness and performs pre-alignment of the wafer W to be chamfered. The measuring unit 20 includes a measurement table (denoted by reference numeral 102 in FIG. 3), a thickness sensor, and an orifier-notch detection sensor for measuring the thickness and performing pre-alignment of the wafer W.

[0044] 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 orifier-notch detection sensor is, for example, a laser sensor and detects the position of the orifier or notch of the wafer W. Examples of the thickness sensor include those of the interference method in addition to the capacitance method, and examples of the orifier-notch detection sensor include an image sensor.

[0045] Further, the measuring unit 20 includes a diameter measuring instrument (not shown) that measures the diameter of the chamfered wafer W, and a shape measuring device 100 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.

[0046] Next, an outline of the operation of the wafer processing system 10 of the present embodiment will be described.

[0047] First, the wafer W is taken out from the wafer 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.

[0048] 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.

[0049] 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.

[0050] Next, in the grinding unit 16, the edge of the wafer W is ground (chamfered) by the grinding device 30. Specifically, after the edge portion 80, which is the outer peripheral portion of the wafer W, is roughly processed 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 processing with a notch rough grinding wheel, chamfering as finish grinding is performed with a notch finish grinding wheel.

[0051] Next, the wafer W for which the grinding process (chamfering) has been completed in the grinding unit 16 is conveyed from the grinding unit 16 to the cleaning unit 18 by the transfer robot of the transfer unit 22. Then, in the cleaning unit 18, the wafer W is cleaned by a spin cleaning device.

[0052] Next, the wafer W for which the cleaning has been completed in the cleaning unit 18 is conveyed from the cleaning unit 18 to the grinding unit 16 by the transfer robot of the transfer unit 22. After that, the wafer W is conveyed from the grinding unit 16 to the measurement unit 20 by the supply / retrieval robot of the load unit 14. The wafer W conveyed to the measurement unit 20 is placed on the measurement table.

[0053] Next, in the measurement 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 measurement unit 20 (the diameter of the wafer W and the three-dimensional shape of the end portion of the wafer W) are output to an output unit (denoted by reference numeral 114 in FIG. 11). Note that the control device 110 described later may calculate a determination result indicating whether or not the measurement results of the measurement unit 20 are within a predetermined range, and output the determination result to the output unit.

[0054] Next, the wafer W for which the measurement in the measurement unit 20 has been completed is transported from the measurement unit 20 to the cassette unit 12 by the supply / retrieval robot of the load unit 14 and stored in a wafer cassette.

[0055] 〔Shape Measuring Device〕 Next, the configuration of the shape measuring device 100 will be described. This shape measuring device 100 is an example of the shape measuring device of the present invention. Based on a plurality of captured images captured at regular pitches while the optical unit 104 (white light interference microscope) described later is scanned in the scanning direction (Z direction), both the WLI method and the FV method are used in combination to calculate three-dimensional shape data indicating height information (such as surface shape and surface roughness) of the measurement surface of the end portion of the wafer W, which is the object to be measured.

[0056] FIG. 3 is a side view (viewed from the X direction) showing a schematic configuration of the shape measuring device 100. FIG. 4 is a plan view (viewed from the Y direction) showing a schematic configuration of the shape measuring device 100.

[0057] As shown in FIGS. 3 and 4, the shape measuring device 100 generally includes a measurement table 102, an optical unit 104, a side illumination unit 108, and a control device 110.

[0058] 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.

[0059] The 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. This optical unit 104 has an optical axis R (corresponding to the optical axis of an interference objective lens 124 (see FIG. 5) described later) parallel (including substantially parallel) to the main surface (upper surface Wu or lower surface Wd) of the wafer W, and coaxial epi-illumination light (measurement light L1 described later) is irradiated along the optical axis R to the measurement surface (denoted by reference numeral T in FIG. 5) of the measurement object (the edge of the wafer W). It includes a light source unit (denoted by reference numeral 120 in FIG. 5) and a camera (denoted by reference numeral 128 in FIG. 5) provided coaxially with the optical axis R for imaging the reflected light from the measurement surface. That is, the optical axis R of the optical unit 104 is arranged so as to be parallel (including substantially parallel) to the direction orthogonal to the rotation axis G of the measurement table 102 (preferably, so as 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 by the measurement table 102. The configuration of the optical unit 104 will be described later.

[0060] The side illumination unit 108 irradiates side illumination light M to the end portion of the wafer W imaged by the camera of the optical unit 104 from a direction (Y direction) orthogonal to the optical axis R of the optical unit 104. The configuration of the side illumination unit 108 will be described later.

[0061] 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.

[0062] 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. Along the left side in the Z direction from the measurement surface T at the end of the wafer W to be measured, the interference objective lens 124, the beam splitter 122, the imaging lens 126, and the camera 128 are arranged in this order. Also, the light source unit 120 is arranged at a position facing the beam splitter 122 in the Y direction.

[0063] Under the control of the control device 110, the light source unit 120 emits white light (low-coherence light with low interferability) 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 has a light source capable of emitting 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.

[0064] 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. Also, the beam splitter 122 transmits a part of the combined light L3, which will be 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.

[0065] The interference objective lens 124 is of the Michelson type and has 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 along the left side in the Z direction from the measurement surface T side. Also, 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 known interference optical systems such as the Mirau type and the Linnik type can be adopted.

[0066] The objective lens 124A has a condensing function and condenses the measurement light L1 incident from the beam splitter 122 onto the surface to be measured T through the beam splitter 124B.

[0067] For example, a half mirror is used as the beam splitter 124B. 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 T, 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 T and then reflected by the surface to be measured T and returns to the beam splitter 124B.

[0068] For example, a reflection mirror is used as the reference surface 124C, and the reference light L2 incident from the beam splitter 124B is reflected toward the beam splitter 124B. This reference surface 124C can be manually adjusted in the Y direction by a position adjustment mechanism (not shown) (for example, a ball screw mechanism, an actuator, etc.). Thereby, the optical path length (reference optical path length) of the reference light L2 can be adjusted.

[0069] The beam splitter 124B generates a combined light L3 of the measurement light L1 returning from the surface to be measured T 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.

[0070] 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.

[0071] The camera 128 has an imaging device of the CCD (Charge Coupled Device) type or the CMOS (Complementary Metal Oxide Semiconductor) type, although not shown in the figure. The camera 128 images the combined light L3 imaged on the imaging surface of the imaging device 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.

[0072] 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, the 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.

[0073] 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. Further, when there is a limitation in the measurement field of the surface T 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.

[0074] 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. The 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.

[0075] Next, the configuration of the side illumination unit 108 will be described in detail. FIG. 6 is a schematic diagram showing the configuration of the side illumination unit 108. In FIG. 6, 1006A is a top view of the side illumination unit 108 (viewed from the Y direction), 1006B is a side view of the side illumination unit 108 (viewed from the X direction), and 1006C is a front view of the side illumination unit 108 (viewed from the Z direction). FIG. 7 is a diagram showing a state when the surface to be measured T is switched between the notch portion 82 and the edge portion 80 (a diagram corresponding to 1006B in FIG. 6).

[0076] As shown in FIGS. 6 and 7, the side illumination unit 108 includes a pair of side light emitters 150A and 150B that are arranged at positions facing each other on both sides in the direction (Y direction) perpendicular to the optical axis R with the end portion of the wafer W to be measured sandwiched therebetween. Of the pair of side light emitters 150A and 150B, one side light emitter 150A is arranged on the upper surface Wu side of the wafer W, and the other side light emitter 150B is arranged on the lower surface Wd side of the wafer W. Further, each of the side light emitters 150A and 150B has a rod-like shape (for example, a cylindrical shape or a prismatic shape) with the direction (Z direction) along the optical axis R of the optical unit 104 as the longitudinal direction. Each of the side light emitters 150A and 150B is an example of a rod-shaped light emitter.

[0077] FIG. 8 is a schematic diagram showing a configuration example of the side light emitter 150. In FIG. 8, the side light emitters 150A and 150B are collectively denoted by the reference numeral 150.

[0078] As shown in 1008A of FIG. 8, in the side light emitter 150 of the first configuration example, a plurality of small LEDs (Light Emitting Diodes) 152 are arranged side by side along the Z direction. Further, as shown in 1008B of FIG. 8, the side light emitter 150 of the second configuration example, in addition to the configuration in which a plurality of small LEDs 152 are arranged side by side along the Z direction, further includes a light diffuser 154 on the emitting surface side of each LED 152. In this case, the light emitted from each LED 152 is irradiated as diffused light to the end portion of the wafer W via the light diffuser 154. Further, as shown in 1008C of FIG. 8, the side light emitter 150 of the third configuration example includes an elongated light guide 156 having the Z direction as its longitudinal direction, and an LED 152 provided at one end of the light guide 156, and irradiates the end portion of the wafer W with the light emitted from the LED 152 through the light guide 156. Note that the side light emitter 150 (150A, 150B) is not limited to the configurations of the first to third configuration examples described above, and may have other configurations.

[0079] As shown in FIGS. 6 and 7, the length of each of the side light emitters 150A and 150B in the longitudinal direction (Z direction) is longer than the length of the end portion of the wafer W. Specifically, as shown in 1006A of FIG. 6, each of the side light emitters 150A and 150B is configured to be longer than at least the depth (radial length of the wafer W) D of the notch portion 82. Then, regardless of whether the surface to be measured T is the notch portion 82 or the edge portion 80, when the end portion of the wafer W is viewed from one side in the Y direction, each of the side light emitters 150A and 150B is arranged at a position overlapping the surface to be measured T (notch portion 82 or edge portion 80). Thereby, regardless of whether the surface to be measured T is the notch portion 82 (illustrated by a solid line in FIG. 7) or the edge portion 80 (illustrated by a broken line in FIG. 7), when the optical unit 104 images the surface to be measured T, it is possible to uniformly irradiate the inclined surfaces S of each part with the side illumination light M.

[0080] Also, as shown in 1006C of FIG. 6, when the notch portion 82 is viewed from the front side (i.e., the side where the optical unit 104 is disposed, the Z direction), inclined surfaces S that expand in a funnel shape are formed on the upper surface Wu side and the lower surface Wd side of the wafer W in the notch portion 82, respectively. According to the side illumination unit 108 of the present embodiment, each side light emitter 150A, 150B has a rod shape with the Z direction as the longitudinal direction, and the outer width H in the X direction is formed to be smaller than the opening width Q of the notch portion 82, and a configuration is adopted in which the side illumination light M can be easily irradiated onto the inclined surface S of the notch portion 82. Generally, since the inner wall surface (such as the inclined surface S) in a concave portion such as the notch portion 82 is likely to be in the shadow and thus difficult to measure, by adopting the configuration as in the present embodiment, it becomes easier to uniformly irradiate the inclined surface S with the side illumination light M, enabling highly sensitive measurement.

[0081] FIG. 9 is a schematic diagram showing the configuration of a side illumination unit 910 according to a comparative example. As shown in FIG. 9, the side illumination unit 910 according to the comparative example includes a pair of dot light emitters 912A, 912B provided at positions facing each other with the end portion of the wafer W interposed therebetween. In the side illumination unit 910 according to the comparative example having such a configuration, when the surface T to be measured is the notch portion 82 (illustrated by a solid line in FIG. 9) and when it is the edge portion 80 (illustrated by a broken line in FIG. 9), the relative position of the surface T to be measured with respect to each dot light emitter 912A, 912B changes in the Z direction. Therefore, there are cases where the side illumination light M irradiated from each dot light emitter 912A, 912B does not sufficiently hit the inclined surface S. In this case, depending on the position of the surface T to be measured, the ratio between the amount of reflected light from the flat surface F, which is the facing portion of the measurement light L1 that is coaxial incident illumination light, and the amount of reflected light from the inclined surface S of the side illumination light M changes, making it difficult to perform the arithmetic processing of the three-dimensional shape data using both the WLI method and the FV method with high accuracy.

[0082] On the other hand, as shown in FIGS. 6 and 7, the side illumination unit 108 of the present embodiment includes a pair of side light emitters 150A, 150B having the optical axis R of the optical unit 104 as the longitudinal direction, and thus the following effects can be obtained.

[0083] FIG. 10 is a diagram for explaining the effect of the side illumination unit 108 of the present embodiment. 1010A in FIG. 10 shows the case where the surface T to be measured is the edge portion 80. Further, 1010B in FIG. 10 shows the case where the surface T to be measured is the notch portion 82.

[0084] As shown in 1010A and 1010B of FIG. 10, the light density of the side illumination light M irradiated from each of the side light emitters 150A and 150B is substantially uniform over the Z direction which is the longitudinal direction of each of the side light emitters 150A and 150B. Therefore, even when the surface T to be measured switches between the edge portion 80 and the notch portion 82 and the position of the surface T to be measured changes in the Z direction, the side illumination light M with a uniform light density is irradiated onto each inclined surface S of the edge portion 80 and the notch portion 82. That is, the amount of the side illumination light M contributing to the reflected light from each inclined surface S is substantially equal regardless of whether the surface T to be measured is the edge portion 80 or the notch portion 82. Therefore, the ratio between the amount of the reflected light from the flat surface F which is the facing portion of the measurement light L1 which is the coaxial epi-illumination light and the amount of the reflected light from the inclined surface S of the side illumination light L becomes substantially constant.

[0085] When calculating the three-dimensional shape data of the surface T to be measured by the WLI method, the side illumination light M becomes a noise source. On the other hand, when calculating the three-dimensional shape data of the surface T to be measured by the FV method, since the measurement sensitivity of the inclined surface S is low with the coaxial epi-illumination light, in order to improve the measurement accuracy for the inclined surface S, it is necessary to irradiate the inclined surface S with the side illumination light M. In order to make both of these two methods compatible and calculate the three-dimensional shape data of the surface T to be measured with stable quality, it is important that the ratio of the side illumination light M does not change with respect to the amount of the coaxial epi-illumination light (measurement light L1). In the side illumination unit 108 of the present embodiment, since each of the side light emitters 150A and 150 has a rod-like shape with the optical axis R of the optical unit 104 as the longitudinal direction, the light density of the side illumination light M does not depend on the position of the surface T to be measured, and thus it is possible to maintain the best illumination state regardless of the position of the surface T to be measured. Therefore, it is possible to stably calculate the three-dimensional shape data by the calculation processes using the two methods.

[0086] Therefore, according to the side illumination unit 108 of the present embodiment, even when the position of the measurement surface T of the object to be measured (the end portion of the wafer W) changes in the direction (Z direction) along the optical axis R of the optical unit 104, it is possible to uniformly irradiate the inclined surface S constituting a part of the measurement surface T with the side illumination light M. As a result, regardless of the position of the measurement surface T, the ratio between the amount of reflected light from the flat surface F, which is the facing portion of the measurement light L1, which is coaxial incident illumination light, and the amount of reflected light from the inclined surface S of the side illumination light M does not change, and it is possible to perform the arithmetic processing of the three-dimensional shape data using both the WLI method and the FV method with high accuracy.

[0087] Next, the configuration of the control device 110 will be described. FIG. 11 is a functional block diagram of the control device 110. As shown in FIG. 11, a light source unit 120, a camera 128, a scale 130, a table drive unit 116, an optical unit drive unit 106, a side illumination unit 108, an operation unit 112, and an output unit 114 of the optical unit 104 are connected to the control device 110.

[0088] The operation unit 112 includes operation members (for example, a keyboard and a mouse, etc.) for receiving an operator's operation input to the control device 110.

[0089] The output unit 114 is a device for outputting the execution result of a program, data of an arithmetic result, etc. by the control device 110. The output unit 114 includes, for example, an operation UI (User Interface) and a monitor (for example, a liquid crystal display, etc.) for displaying the detection result. In addition to or instead of the monitor, the output unit 114 may include a printer or a speaker, etc.

[0090] The control device 110 controls the measurement operation of the three-dimensional shape of the surface T to be measured 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 T to be measured. The control device 110 includes a processor that executes various operations (for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc.), a memory that serves as a working area for the processor (for example, a ROM (Read Only Memory) and a RAM (Random Access Memory), etc.), and a storage device for storing various programs and data (for example, an SSD (Solid State Drive) or an HDD (Hard Disk Drive), etc.).

[0091] The control device 110 functions as a measurement control unit 160 and a shape data generation unit 162 by executing the program stored in the storage device by the processor. Further, the shape data generation unit 162 functions as a first shape data generation unit 164, a second shape data generation unit 166, and an integration calculation unit 168, which will be described later.

[0092] The measurement control unit 160 controls the table drive unit 116, the optical unit drive unit 106, the light source unit 120, the camera 128, and the side illumination unit 108, and while scanning the optical unit 104 in the scanning direction (Z direction), repeatedly images the measurement surface T (edge portion 80 or notch portion 82) of the object to be measured by the camera 128 at regular pitches. Specifically, the measurement control unit 160 controls the table drive unit 116 to rotate the measurement table 102 so that the measurement surface T (edge portion 80 or notch portion 82) of the object to be measured faces the optical unit 104. Further, after the measurement control unit 160 starts the emission of the measurement light L1 from the light source unit 120 and starts the emission of the side illumination light M from the side illumination unit 108, it 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, based on the detection result of the Z-direction position of the optical unit 104 by the scale 130, each time the optical unit 104 moves by a fixed pitch in the Z direction, the measurement control unit 160 repeatedly executes imaging of the combined light L3 (including the reflected light of the side illumination light M) by the camera 128 and output of the captured image to the control device 110.

[0093] Further, the measurement control unit 160 functions as a light amount control unit that controls the light amount of the side illumination light M irradiated from the side illumination unit 108 (side light emitters 150A, 150B). Thereby, since the ratio of the light amount of the side illumination light M to the light amount of the measurement light L1 can be changed, it is possible to optimize the irradiation conditions according to the shape of the measurement surface T of the object to be measured and the like.

[0094] Each time the camera 128 captures an image of the combined light L3, the shape data generation unit 162 acquires the captured image output from the camera 128 and generates three-dimensional shape data of the measurement surface T of the object to be measured. The shape data generation unit 162 includes a first shape data generation unit 164 that generates three-dimensional shape data (first shape data) of the measurement surface T by the WLI method, a second shape data generation unit 166 that generates three-dimensional shape data (second shape data) of the measurement surface T by the FV method, and an integration calculation unit 168 that calculates three-dimensional shape data (integrated shape data) of the measurement surface T obtained by integrating the first shape data and the second shape data generated by the two methods. Note that the captured image output from the camera 128 may be acquired via a storage device (such as a memory or a storage device) provided in the control device 110.

[0095] The first shape data generation unit 164 performs three-dimensional shape calculation of the measurement surface T in the WLI method based on a plurality of captured images captured by the camera 128 at regular intervals while scanning the optical unit 104 in the Z direction. Specifically, the first shape data generation unit 164 compares the luminance values of the pixels at the same coordinates in each captured image. Next, the first shape data generation unit 164 determines the Z-direction position where the luminance value is maximized for each pixel at the same coordinates in each captured image, thereby calculating height information indicating the height position (Z-direction position) of each part of the measurement surface T corresponding to each pixel. Thereby, three-dimensional shape data (first shape data) indicating the three-dimensional shape (height distribution) of the measurement surface T is generated.

[0096] The second shape data generation unit 166 performs three-dimensional shape calculation of the measurement surface T in the FV method based on a plurality of captured images captured by the camera 128 at regular pitches while scanning the optical unit 104 in the Z direction. Specifically, the second shape data generation unit 166 calculates the in-focus degree (contrast, sharpness) for each pixel of each captured image. For example, the second shape data generation unit 166 uses the pixel for which the in-focus degree is calculated as the target pixel, and based on the luminance value of this target pixel and the luminance values of each pixel within the in-focus degree calculation range with the target pixel as the reference, calculates the in-focus degree by a known method. The second shape data generation unit 166 calculates the in-focus degree for each pixel of each captured image by repeatedly executing the in-focus degree calculation process for all pixels of each captured image.

[0097] After calculating the in-focus degree, the second shape data generation unit 166 compares the in-focus degrees of the pixels at the same coordinates of each captured image, and determines the Z-direction position where the in-focus degree is maximized for each pixel at the same coordinates. Then, the second shape data generation unit 166 determines the focal position of the camera 128 with respect to the measurement surface T for each pixel at the same coordinates, and calculates height information indicating the height position (Z-direction position) of each part of the measurement surface T corresponding to each pixel. Thereby, three-dimensional shape data (second shape data) indicating the three-dimensional shape (height distribution) of the measurement surface T is generated.

[0098] Note that since the three-dimensional shape calculation process by the WLI method and the three-dimensional shape calculation process by the FV method are known techniques, detailed description thereof is omitted (see, for example, Patent Document 2).

[0099] The integration calculation unit 168 compares the first shape data and the second shape data after the processing of the first shape data generation unit 164 and the second shape data generation unit 166, and generates three-dimensional shape data (integrated shape data) of the measurement surface T in which the shape data with higher accuracy is selectively combined.

[0100] As a method for generating integrated shape data, for example, the method disclosed in Japanese Patent Application Laid-Open No. 2014-1964 can be adopted. In this method, the inclination angle (an example of an index value) of each pixel is calculated based on the second shape data generated by the FV method, and the inclination angle of each pixel is compared with a preset inclination angle threshold. For pixels whose inclination angle is less than or equal to the inclination angle threshold, the first shape data is selected, and for pixels whose inclination angle exceeds the inclination angle threshold, the second shape data is selected. As a result, integrated shape data is generated in which the first shape data is selected for surfaces with a small inclination angle and the second shape data is selected for surfaces with a large inclination angle. As a result, for the flat surface F of the surface to be measured T, the surface shape, surface roughness, etc. can be measured with high accuracy, and for the inclined surface S, highly sensitive measurement becomes possible.

[0101] In addition, the inclination angle of each pixel may be calculated based on the first shape data generated by the WLI method, and the inclination angle of each pixel may be compared with a preset inclination angle threshold. For pixels whose inclination angle is less than or equal to the inclination angle threshold, the first shape data may be selected, and for pixels whose inclination angle exceeds the inclination angle threshold, the second shape data may be selected. Further, not limited to each pixel, the above-described processes may be performed for each region composed of a plurality of pixels.

[0102] Further, as another method for generating integrated shape data, the method disclosed in Patent Document 2 may be adopted. In this method, the S / N ratio (signal-to-noise ratio) of the first shape data and the second shape data is calculated for each pixel, and integrated shape data is generated in which the shape data with the higher S / N ratio is selected for each pixel based on the S / N ratio calculated for each pixel.

[0103] In the method disclosed in Patent Document 2, the S / N ratio is calculated and compared for each pixel of each shape data. However, the present invention is not limited to this, and the S / N ratio may be calculated and compared for each region composed of a plurality of pixels. Also, in this method, each of the above-described processes may be performed not only for each pixel but also for each region composed of a plurality of pixels. Further, in each of the above-described methods, the inclination angle or the S / N ratio is used as an index value for comparing the accuracy of each shape data. However, other index values may be used as long as they can evaluate the accuracy of each shape data.

[0104] As described above, in the shape data generation unit 162, the first shape data generation unit 164 generates the first shape data (three-dimensional shape data by the WLI method), and the second shape data generation unit 166 generates the second shape data (three-dimensional shape data by the FV method). Then, the integration calculation unit 168 generates integrated shape data by selecting the more accurate one of the first shape data and the second shape data for each pixel or each region. Then, the shape data generation unit 162 outputs the integrated shape data generated by the integration calculation unit 168 to the output unit 114 as the measurement result of the three-dimensional shape of the measurement surface T. As a result, according to the operation of the operation unit 112, the measurement result of the three-dimensional shape of the measurement surface T is displayed on the monitor of the output unit 114 or the like.

[0105] 〔Shape measurement method〕 Next, a shape measurement method using the shape measurement apparatus 100 of the present embodiment will be described.

[0106] FIG. 12 is a flowchart showing the flow of the shape measurement method using the shape measurement apparatus 100 of the present embodiment. At the start of this measurement process, it is assumed that the wafer W is placed on the holding surface 102a of the measurement table 102. Here, a case where the three-dimensional shape of the notch portion 82 among the ends of the wafer W is measured will be described as an example.

[0107] As shown in FIG. 12, when the measurement process by the shape measurement apparatus 100 is started, first, relative alignment (alignment) between the notch portion 82 of the wafer W and the optical unit 104 is performed (step S10). Specifically, the measurement control unit 160 drives the table drive unit 116 to rotate the measurement table 102, thereby arranging the notch portion 82 of the wafer W at a position facing the optical unit 104. Further, the measurement control unit 160 drives the optical unit drive unit 106 to move the optical unit 104 in the X direction or the Y direction, thereby aligning the optical unit 104 with respect to the notch portion 82 so that the notch portion 82 is located in the direction along the optical axis R of the optical unit 104. Note that this alignment may be performed using the camera 128 of the optical unit 104 or a known alignment technique.

[0108] After the relative alignment between the notch portion 82 of the wafer W and the optical unit 104 is performed, the measurement control unit 160 starts the emission of the measurement light L1 from the light source unit 120 and also starts the emission of the side illumination light M from the side illumination unit 108 (side light emitters 150A, 150B) (step S12, side illumination step). As a result, the combined light L3 that is the combined light of the measurement light L1 reflected by the measurement surface T and the reference light L2 reflected by the reference surface 124C and includes interference fringes (including the reflected light of the side illumination light M reflected by the inclined surface S of the measurement surface T) enters the camera 128. Then, the measurement control unit 160 controls the optical unit drive unit 106 to start the Z-direction scanning of the optical unit 104 (step S14, scanning step).

[0109] Further, based on the detection result of the Z-direction position of the optical unit 104 by the scale 130, the measurement control unit 160 repeatedly executes imaging of the combined light L3 by the camera 128 every time the optical unit 104 moves by a certain pitch in the Z direction (NO in steps S16 and S18, steps S20, imaging step). As a result, while the optical unit 104 is being scanned, imaging images are repeatedly input from the camera 128 to the shape data generation unit 162, and the shape data generation unit 162 repeatedly acquires the imaging images.

[0110] When the scanning of the optical unit 104 is completed (YES in step S18), the first shape data generation unit 164 detects the luminance value for each pixel of the plurality of imaging images captured by the camera 128, determines the Z-direction position where the luminance value is maximized for each pixel of the same coordinates in each imaging image, and calculates the height information of the measurement surface T for each pixel of the same coordinates, thereby generating three-dimensional shape data (first shape data) indicating the three-dimensional shape of the measurement surface T (step S22).

[0111] Further, the second shape data generation unit 166 calculates the focus degree for each pixel of the plurality of imaging images captured by the camera 128, and based on the result of comparing the focus degrees for each pixel of the same coordinates in each imaging image, generates three-dimensional shape data (second shape data) indicating the three-dimensional shape (height distribution) of the measurement surface T (step S24).

[0112] Then, after the processing by the first shape data generation unit 164 and the second shape data generation unit 166, the integration calculation unit 168 selectively combines the shape data with higher accuracy among the first shape data and the second shape data for each pixel or each region of each shape data to generate three-dimensional shape data (integrated shape data) of the measurement surface T (step S26, shape data generation step). The integrated shape data generated in this way is output to the output unit 114. Thus, the flowchart shown in FIG. 12 ends.

[0113] 〔Effects of this Embodiment〕 According to the shape measurement device 100 of the present embodiment, when the optical unit 104 is scanned in the scanning direction (Z direction) and the imaging of the measurement surface T by the camera 128 is repeatedly performed at a constant pitch, the side illumination unit 108 irradiates the side illumination light M to the end of the wafer W. In particular, in the present embodiment, since each side light emitter 150A, 150B constituting the side illumination unit 108 is formed in a rod shape having a longitudinal direction along the optical axis R of the optical unit 104, regardless of whether the edge portion 80 or the notch portion 82 of the wafer W is measured, the reflected light from the flat surface F and the inclined surface S on the measurement surface T can be optimized. Therefore, even if the position of the measurement surface T changes, both the flat surface F and the inclined surface S can be measured under the best optical conditions. Therefore, it is possible to measure the three-dimensional shapes of both the edge portion 80 and the notch portion 82 of the wafer W with the same quality.

[0114] Further, according to the shape measurement device 100 of the present embodiment, by providing the side illumination unit 108 configured as described above, it is possible to maintain the best illumination state regardless of the position of the measurement surface T. Therefore, three-dimensional shape data can be stably calculated by arithmetic processing using two methods (WLI method and FV method). Therefore, for a surface (flat surface F) that is nearly perpendicular to the optical axis R of the optical unit 104, the surface shape, surface roughness, etc. can be measured with high precision, and for a surface (inclined surface S) that is inclined with respect to the optical axis R of the optical unit 104, high-sensitivity measurement is possible. As a result, it becomes possible to measure the roughness of the bottom 82b (see FIG. 17) of the notch portion 82, which is particularly important in the measurement of the three-dimensional shape of the measurement surface T. Note that since the bottom 82b of the notch portion 82 is composed of a surface that is nearly perpendicular to the optical axis R of the optical unit 104, the surface shape, surface roughness, etc. of the bottom 82b of the notch portion 82 can be measured with high precision by arithmetic processing using the WLI method.

[0115] 〔Modification Example〕 Next, a modification example of the present embodiment will be described.

[0116] <First Modification Example> In this embodiment, the measurement control unit 160 (an example of a light quantity control unit) may be capable of independently controlling the light quantity of the side illumination light M emitted by each of the side light emitters 150A and 150B that constitute the side illumination unit 108. For example, as shown in FIG. 13, when the inclination angles of the inclined surface S on the upper surface Wu side and the inclined surface S on the lower surface Wd side are different on the measurement surface T at the end of the wafer W, among the side illumination lights M irradiated from the side light emitters 150A and 150B, the light quantity of the reflected light that is reflected by each inclined surface S and travels toward the optical unit 104 may be different. In such a case, the emission quantity of the side light emitter 150A on the upper surface Wu side where the light quantity of the reflected light becomes relatively large is made relatively smaller than the light quantity of the side light emitter 150B on the lower surface Wd side where the light quantity of the reflected light becomes relatively small (preferably, so that the reflected light from both inclined surfaces S becomes substantially uniform), and the irradiation light quantities of the respective side light emitters 150A and 150B are individually controlled. Thereby, without being affected by the difference in the inclination angles of the respective inclined surfaces S, the reflected light of the side illumination light M reflected by each inclined surface S becomes uniform, so that it becomes possible to stably perform the arithmetic processing by the FV method.

[0117] (Second Modified Example) The side illumination unit 108 of this embodiment has been shown in a configuration including a pair of side light emitters 150A and 150B on both sides sandwiching the end of the wafer W, but is not limited thereto, and it may be configured to include only one of the pair of side light emitters 150A and 150B. For example, as shown in FIG. 14, when the inclined surface S is formed only on the upper surface Wu side of the wafer W, the side light emitter 150A may be arranged only on the side where the inclined surface S is formed among both sides sandwiching the end of the wafer W. According to the second modified example, it becomes possible to realize the side illumination unit 108 at low cost.

[0118] (Third Modified Example) In a preferred aspect, the side illumination unit 108 of the present embodiment is configured such that each of the side light emitters 150A and 150B is formed in a rod shape with the longitudinal direction along the optical axis R of the optical unit 104 (Z direction). However, the present invention is not limited to this. For example, as shown in 1015A to 1015C of FIG. 15, each of the side light emitters 158A and 158B may be configured in a planar shape parallel to the main surface (upper surface Wu or lower surface Wd) of the wafer W. A plurality of light sources are two-dimensionally arranged along the Y direction and the Z direction, which are directions parallel to the main surface of the wafer W, on each of the side light emitters 158A and 158B, and side illumination light M is emitted in a planar shape parallel to the main surface of the wafer W. Each of the side light emitters 158A and 158B is an example of a surface light emitter. Each of the side light emitters 158A and 158B shown in FIG. 15 is, as an example, configured in a rectangular shape in plan view with the longitudinal direction along the optical axis R of the optical unit 104 (Z direction) and the short side direction perpendicular to the optical axis R (X direction). Further, the length of each of the side light emitters 158A and 158B in the short side direction is configured to be equal to or longer than the opening width Q of the notch portion 82. According to such a configuration, even when the opening width Q of the notch portion 82 is large, it is possible to irradiate the entire notch portion 82 with the side illumination light M.

[0119] (Fourth Modification Example) Each side light emitter 150A, 150B (or side light emitters 158A, 158B) constituting the side illumination unit 108 may be configured to be movable in the Y direction. Thereby, for example, as shown in FIG. 16, when the inclination angles of the inclined surface S on the upper surface Wu side and the inclined surface S on the lower surface Wd side are different on the measurement surface T at the end of the wafer W, the distance between the side light emitter 150A on the upper surface Wu side with a larger inclination angle and the end of the wafer W is relatively larger than the distance between the side light emitter 150B on the lower surface Wb side with a smaller inclination angle and the end of the wafer W. The side light emitter 150A is moved to one side in the Y direction (the upper side in FIG. 16). Instead of moving the side light emitter 150A to one side in the Y direction, the side light emitter 150B may be moved to the other side in the Y direction (the lower side in FIG. 16). Thereby, it becomes possible to equalize the amount of reflected light of the side illumination light M reflected by each inclined surface S. As a result, similar to the first modification example, it is possible to equalize the reflected light of the side illumination light M reflected by each inclined surface without being affected by the difference in the inclination angle of each inclined surface S, so that it is possible to stably perform the arithmetic processing by the FV method. Note that a combination of the first modification example and the fourth modification example may also be used.

[0120] (Fifth Modification Example) The optical unit 104 used in the shape measurement apparatus 100 of the present embodiment includes the interference objective lens 124. However, instead of the interference objective lens 124, it may include a non-interference objective lens (objective lens for bright field observation) used in general FV method measurement. In this case, in the flowchart shown in FIG. 12, the generation of the first shape data by the WLI method is not performed (step S22), and only the generation of the second shape data by the FV method is performed (step S24). Then, the integration calculation unit 168 outputs the second shape data generated in step S24 to the output unit 114 as the three-dimensional shape data (integrated shape data) of the measurement surface T.

[0121] According to the fifth modification example, since the three-dimensional shape data of the surface T to be measured is obtained by calculation using the FV method, the measurement accuracy of the flat surface F is inferior to that of the present embodiment described above. However, with the side illumination unit 108, regardless of whether the edge portion 80 or the notch portion 82 of the wafer W is measured, the reflected light from the flat surface F and the inclined surface S on the surface T to be measured can be optimized. Therefore, it is possible to measure the three-dimensional shape of the inclined surface S with high sensitivity.

[0122] (Sixth Modification Example) In the shape measurement apparatus 100 of the present embodiment, the measurement operation of repeatedly imaging with the camera 128 at a constant pitch while scanning the optical unit 104 in the scanning direction (Z direction) is performed only once. However, the present invention is not limited to this. For example, a first measurement operation of performing measurement with the interference objective lens 124 attached to the optical unit 104 and a second measurement operation of performing measurement with a non-interference objective lens attached to the optical unit 104 may be performed. That is, the measurement may be performed in two measurement operations in which the objective lens attached to the optical unit 104 is switched for each measurement. In this case, in the flowchart shown in FIG. 12, the generation of the first shape data by the WLI method is performed based on a plurality of captured images obtained in the first measurement operation (step S22). Further, the generation of the second shape data by the FV method is performed based on a plurality of captured images obtained in the second measurement operation (step S24). Then, the integration calculation unit 168 generates three-dimensional shape data (integrated shape data) of the surface T to be measured in which the two shape data are selectively combined for each pixel or each region, and outputs the data to the output unit 114 (step S26).

[0123] According to the sixth modification example, since the measurement operation is performed twice, although the measurement time is longer than that of the present embodiment described above, it is possible to perform measurement under measurement conditions suitable for the first measurement operation and the second measurement operation, respectively. Therefore, it is possible to measure the three-dimensional shape of the surface T to be measured with higher accuracy.

[0124] The embodiments of the present invention have been described above. However, the present invention is not limited to the above examples, and of course, various improvements and modifications may be made without departing from the gist of the present invention.

Explanation of Reference Numerals

[0125] 10…Wafer processing system, 12…Cassette unit, 14…Load unit, 16…Grinding unit, 18…Washing unit, 20…Measuring unit, 22…Conveying 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, 82a…Straight portion, 82b…Bottom portion, 84…Chamfering portion, 100…Shape measuring device, 102…Measuring table, 102a…Holding surface, 104…Optical unit, 106…Optical unit driving portion, 108…Side illumination unit, 110…Control device, 112…Operation portion, 114…Output portion, 116…Table driving portion, 120…Light source portion, 122…Beam splitter, 124…Interference objective lens, 124A…Objective lens, 124B…Beam splitter, 124C…Reference surface, 126…Imaging lens, 128…Camera, 130…Scale, 150…Side light emitter, 150A…Side light emitter, 150B…Side light emitter, 152…LED, 154…Light diffuser, 156…Light guide, 158A…Side light emitter, 158B…Side light emitter, 160…Measurement control portion, 162…Shape data generation portion, 164…First shape data generation portion, 166…Second shape data generation portion, 168…Integration calculation portion, 900…White interference microscope, 902…Measured surface, 904…Captured image, 910…Side illumination unit, 912A…Point light emitter, 912B…Point light emitter, W…Wafer, Wu…Upper surface, Wb…Lower surface, T…Measured surface, F…Flat surface, S…Inclined surface, L1…Measurement light, L2…Reference light, M…Side illumination light, R…Optical axis, G…Rotation axis

Claims

1. A shape measurement apparatus for measuring the three-dimensional shape of a measurement surface at an end of a wafer, comprising a light source unit having an optical axis parallel to the main surface of the wafer and irradiating coaxial incident illumination light along the optical axis onto the measurement surface, and an imaging unit provided coaxially with the optical axis for imaging reflected light from the measurement surface; an optical unit, a relative movement unit that relatively moves the optical unit in a direction along the optical axis with respect to the measurement surface, a side illumination unit that irradiates side illumination light onto the measurement surface from a direction orthogonal to the optical axis, and a shape data generation unit that generates three-dimensional shape data indicating the three-dimensional shape of the measurement surface based on a plurality of captured images repeatedly captured by the imaging unit while the optical unit is relatively moving. A shape measurement apparatus comprising the above.

2. The side illumination unit has a bar-shaped light emitter having a longitudinal direction parallel to the optical axis. The shape measurement apparatus according to Claim 1.

3. The side illumination unit has a pair of the bar-shaped light emitters provided on both sides in a direction orthogonal to the optical axis with the end of the wafer interposed therebetween. The shape measurement apparatus according to Claim 2.

4. The shape measurement apparatus according to Claim 1, further comprising a light quantity control unit that controls the light quantity of the side illumination light irradiated from the side illumination unit. The shape measurement apparatus according to Claim 1.

5. The shape measurement apparatus according to Claim 3, further comprising a light quantity control unit that independently controls the light quantity of the side illumination light emitted by the pair of bar-shaped light emitters. The shape measurement apparatus according to Claim 3.

6. The side illumination unit has a planar light emitter that emits light in a planar shape parallel to the main surface. The shape measurement apparatus according to Claim 1.

7. It has a measurement table that holds the wafer and is configured to be rotatable about a rotation axis orthogonal to the main surface of the wafer. It includes a measurement control unit that rotates the measurement table so that the surface to be measured at the end of the wafer is positioned at a position facing the optical unit. The shape measurement device according to claim 1.

8. The shape data generation unit includes: A first shape data generation unit that generates first shape data indicating the three-dimensional shape of the surface to be measured by a white interference method based on the plurality of captured images; A second shape data generation unit that generates second shape data indicating the three-dimensional shape of the surface to be measured by a focus variation method based on the plurality of captured images; An integration operation unit that generates integrated shape data by selectively combining the first shape data and the second shape data pixel by pixel or region by region based on an index value obtained from at least one of the first shape data and the second shape data; The shape measurement device according to any one of claims 1 to 7, having the above components.

9. A shape measurement method for measuring the three-dimensional shape of the surface to be measured at the end of a wafer, comprising: A scanning step of relatively moving an optical unit having an optical axis parallel to the main surface of the wafer in a direction along the optical axis with respect to the surface to be measured; An imaging step of irradiating the surface to be measured with coaxial epi-illumination light along the optical axis from the optical unit while the scanning step is being performed, and imaging the reflected light from the surface to be measured by an imaging unit provided coaxially with the optical axis in the optical unit; A side illumination step of irradiating the surface to be measured with side illumination light from a direction orthogonal to the optical axis while the imaging step is being performed; A shape data generation step of generating three-dimensional shape data indicating the three-dimensional shape of the surface to be measured based on the plurality of captured images captured by the imaging unit in the imaging step; The shape measurement method including the above steps.

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