Wafer processing method

Abstract

To provide a wafer processing method of grinding a front surface of a wafer in which a post region and an outer peripheral residual region surrounding the post region are formed, to grind the height of a post to a desired height.SOLUTION: A processing method by a grinding deice 1 includes the steps of: holding another surface of a wafer on a chick table 32; detecting a height position of the front surface of an outer peripheral residual region of the held wafer with a laser displacement gauge 5; rotating the chuck table, and making grinding means 4 comprising a grinding wheel 425 in which a grinding grinder 426 is annularly distributed approach the wafer held on the chuck table to grind a post region of the wafer so that the grinding grinder passes through a rotational center of the wafer; and detecting the height position of the post to be ground in the post region when executing the grinding step, and terminating the grinding step in the case where a difference between the height position of the post and the height position of the outer peripheral residual region becomes a predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for processing a wafer having a post region in which a plurality of fine posts are formed and a peripheral excess region surrounding the post region formed on one surface. [Background technology]

[0002] A wafer has a plurality of devices such as ICs and LSIs formed on its surface, which is partitioned by planned dividing lines. The back surface is ground by a grinding machine to form the wafer to the desired thickness, and then the wafer is divided into individual device chips by a dicing machine, which are then used in electrical devices such as mobile phones and personal computers.

[0003] The grinding device is equipped with at least a chuck table for holding the wafer, a grinding means having a rotatable grinding wheel with a ring-shaped arrangement of grinding stones for grinding the wafer held on the chuck table, a grinding feed means for feeding the grinding means, and a measuring means for measuring the thickness of the wafer, and can process the wafer to the desired thickness (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-246098 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there are cases where it is required to grind the surface of a wafer on one side of which a post region in which multiple fine posts are formed and a peripheral excess region surrounding the post region, and to accurately grind the height of the posts to a desired height.However, a specific method for achieving such processing has not yet been established, and there is a problem in that it is difficult to implement.

[0006] The present invention has been made in consideration of the above facts, and its main technical object is to provide a wafer processing method that can grind the surface of a wafer on one side of which a post region in which a plurality of fine posts are formed and a peripheral excess region surrounding the post region are formed, and that can accurately grind the height of the posts to a desired height. [Means for solving the problem]

[0007] In order to solve the above-mentioned main technical problem, according to the present invention, a method for processing a wafer having a post region in which a plurality of fine posts are formed and a peripheral excess region surrounding the post region formed on one side thereof, the method comprising: a holding step of holding the other side of the wafer on a chuck table; and a peripheral height detection step of detecting the height position of the surface of the peripheral excess region of the wafer held on the chuck table by a laser displacement meter. After the outer periphery height detection step is performed, a grinding step in which the chuck table is rotated and a grinding means having a rotatable grinding wheel with grinding stones arranged in an annular shape is brought close to the wafer held on the chuck table, and the post region of the wafer is ground so that the grinding stone passes through the center of rotation of the wafer; and a laser displacement meter is used to detect the height position of the post to be ground in the post region during the grinding step, and the height position of the post is calculated. The outer periphery height detected by the outer periphery height detection process and a grinding termination step of terminating the grinding step when the difference in height between the surface of the outer peripheral excess area and the surface of the outer peripheral excess area reaches a predetermined value.

[0008] In the grinding completion step, it is preferable to detect at least any breakage or chipping of the post. [Effects of the Invention]

[0009] The wafer processing method of the present invention is a method for processing a wafer having a post region in which a plurality of fine posts are formed and a peripheral excess region surrounding the post region formed on one side, the method comprising: a holding step of holding the other side of the wafer on a chuck table; and a peripheral height detection step of detecting the height position of the surface of the peripheral excess region of the wafer held on the chuck table with a laser displacement meter. After the outer periphery height detection step is performed, a grinding step in which the chuck table is rotated and a grinding means having a rotatable grinding wheel with grinding stones arranged in an annular shape is brought close to the wafer held on the chuck table, and the post region of the wafer is ground so that the grinding stone passes through the center of rotation of the wafer; and a laser displacement meter is used to detect the height position of the post to be ground in the post region during the grinding step, and the height position of the post is calculated. The outer periphery height detected by the outer periphery height detection process The method further includes a grinding termination process that terminates the grinding process when the difference in height between the surface of the peripheral surplus area and the post area reaches a predetermined value, thereby eliminating the problem of difficulty in grinding the post height to the desired height when grinding a wafer that has a post area on one side on which multiple fine posts are formed and a peripheral surplus area surrounding the post area. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an overall perspective view of a grinding apparatus suitable for the wafer processing method of the present embodiment. [Figure 2] FIG. 2(a) is a block diagram showing an outline of a laser displacement meter disposed in the grinding device shown in FIG. 1, and FIG. 2(b) is a conceptual diagram of laser light decomposed so that the focal positions differ for each wavelength in the vertical direction. [Figure 3] FIG. 1(a) is a perspective view showing an embodiment of the holding step, and FIG. 1(b) is a cross-sectional view taken along the line AA in FIG. [Figure 4] FIG. 10 is a perspective view showing an embodiment of a peripheral height detection step. [Figure 5] 10A and 10B are perspective views showing embodiments of a grinding step and a grinding finishing step. [Figure 6] 10 is a graph based on data showing changes in post height caused by a grinding process. [Figure 7] FIG. 10 is a perspective view of the wafer after the grinding step is completed. [Figure 8] 10 is a graph based on data on post breakage and chipping detected in the grinding completion process. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a wafer processing method according to the present invention will be described in detail with reference to the accompanying drawings.

[0012] Fig. 1 shows an overall perspective view of a grinding apparatus 1 suitable for carrying out this embodiment. The grinding apparatus 1 shown in Fig. 1 includes a holding means 3 having a chuck table 32 that holds a plate-shaped workpiece by suction, a grinding means 4 as a processing means for grinding the workpiece held by suction on the chuck table 32, a laser displacement meter 5 that detects the height position of the surface of the workpiece, and a control means 100 that controls each operating part. The workpiece in this embodiment is a wafer 10 shown in Fig. 3(a), and details will be described later.

[0013] The grinding apparatus 1 shown in FIG. 1 includes an apparatus housing 2. The apparatus housing 2 has a roughly rectangular parallelepiped main body 21 and an upright wall 22 attached to the rear end of the main body 21 and extending in the vertical direction. The holding means 3 is disposed in the main body 21, and bellows means 6a and 6b are disposed on both sides of the holding means 3 in the X-axis direction indicated by the arrow X. The main body 21 contains a moving means (not shown) for moving the chuck table 32 of the holding means 3 in the X-axis direction. By operating the moving means, the bellows means 6a and 6b can be extended and retracted, and the unprocessed wafer 10 can be moved between a loading / unloading area at the front of the drawing, where the wafer is placed on the chuck table 32, and a processing area at the back of the drawing, where the wafer is processed directly below the grinding means 4. Note that, for convenience of explanation, the control means 100 is shown outside the grinding apparatus 1 in FIG. 1, but in reality, it is housed inside the apparatus housing 2.

[0014] The grinding means 4 is disposed on the front surface of the upright wall 22. The grinding means 4 includes a movable base 41 and a spindle unit 42 attached to the movable base 41. The rear side of the movable base 41 engages with a pair of guide rails 221, 221 attached to the upright wall 22 of the device housing 2, and is attached so as to be slidable in the Z-axis direction (up and down direction) relative to the guide rails 221, 221.

[0015] The spindle unit 42 includes a spindle housing 421 supported by a support portion 413 formed integrally with the movable base 41, a rotary spindle 422 rotatably held by the spindle housing 421, and a servo motor 423 disposed as a rotary drive means for driving the rotary spindle 422 to rotate. The lower end of the rotary spindle 422 protrudes downward from the spindle housing 421, and a wheel mount 424 is disposed at the lower end. A grinding wheel 425 is attached to the lower surface of the wheel mount 424, and a plurality of grinding stones 426 are disposed annularly on the lower surface of the grinding wheel 425 (see also FIG. 5). The grinding stone 426 in this embodiment is selected to have a roughness and material suitable for grinding posts 12 (see FIG. 3) formed on the front surface 10a of the wafer 10, which will be described later. For example, a vitrified grinding stone with a roughness of #4000 is selected.

[0016] The grinding apparatus 1 shown in Fig. 1 is equipped with a grinding feed means 7 that moves the grinding means 4 in the vertical direction along the pair of guide rails 221, 221. The grinding feed means 7 is equipped with an externally threaded rod 71 that is disposed on the front side of the upright wall 22 and extends in the vertical direction. The upper and lower ends of the externally threaded rod 71 are rotatably supported by the upright wall 22. A pulse motor 72 is disposed at the upper end of the externally threaded rod 71 as a drive source for rotating the externally threaded rod 71, and the output shaft of the pulse motor 72 is connected to the externally threaded rod 71. A threaded connecting portion (not shown) is formed on the rear surface of the movable base 41, and a female-threaded hole extending in the vertical direction is formed in the connecting portion, into which the externally threaded rod 71 is screwed. Such grinding feed means 7 can lower the grinding means 4 together with the moving base 41 by rotating the pulse motor 72 forward, and can raise the grinding means 4 together with the moving base 41 by rotating the pulse motor 74 backward.

[0017] 1, the laser displacement meter 5 is disposed on the main body 21 of the device housing 2 at a position close in the Y-axis direction to the area where the chuck table 32 moves in the X-axis direction, and is disposed on the side wall 23 formed along the X-axis direction. The laser displacement meter 5 is driven by a moving means (not shown) disposed inside the side wall 23 and is configured to be movable along a sliding groove 231 of the side wall 23 formed along the direction indicated by X1 in the drawing.

[0018] 1 and the block diagram showing an outline of the laser displacement meter 5 shown in Fig. 2(a), the function of the laser displacement meter 5 will be described in more detail. The laser displacement meter 5 includes a detection unit 51, a light source 52 disposed in the detection unit 51, a beam splitter 53 that transmits a part of the laser light L0 emitted from the light source 52, a projection lens 54 (e.g., a chromatic aberration lens) that splits the laser light L0 that has transmitted through the beam splitter 53 into laser lights (L1 to L2) of different wavelengths and generates focusing points in the vertical direction, a convex lens 55A that focuses the laser light that is reflected by the surface 10a of the workpiece (wafer 10 in the figure) and then reflected back by the beam splitter 53 and split, and a part of the reflected light focused by the convex lens 55A that focuses the laser light that is reflected by the surface 10a of the workpiece (wafer 10 in the figure) and then reflected back by the beam splitter 53 and split. The apparatus comprises a pinhole mask 56 having a pinhole 56a that passes only the laser light of the wavelength that is most focused on the surface of the workpiece (a part of L1 to L2 in the figure), a convex lens 55B that converts the laser light that has passed through the pinhole 56a into a substantially parallel beam, a diffraction grating 57 that reflects the laser light irradiated from the convex lens 55B in different directions for each wavelength, and a wavelength detector 58 that receives the laser light reflected by the diffraction grating 57 and includes a high-resolution photodetector that identifies the wavelength of the received laser light depending on the position at which it is received, and the wavelength detector 58 is connected to a control means 100.

[0019] The detection unit 51 has an air flow path 51a that communicates in the vertical direction, and high-pressure (e.g., 0.5 MPa) air 50 is introduced into the air flow path 51a from an air supply source (not shown), and the high-pressure air 50 introduced into the air flow path 51a is sprayed from a laser irradiation port 51b at the lower end of the detection unit 51 toward the measurement unit directly below at a flow rate of, for example, 160 L / min. When the height position of the surface of the workpiece is detected using the laser displacement meter 5, the spray of high-pressure air 50 blows away dust, machining fluid, etc. that have adhered to the surface of the workpiece positioned directly below the detection unit 51, making it possible to detect the height position of the surface of the workpiece with high accuracy.

[0020] The laser light L0 emitted from the light source 52 in this embodiment is, for example, white light, and is light that includes not only visible light wavelengths but also a wide range of wavelengths from 350 nm to 1400 nm, and a light source that emits light with stable intensity over the entire wavelength band is selected as the light source 52. As shown in the conceptual diagram of Figure 2(b), the laser light emitted from the laser irradiation port 51b of the detection unit 51 described above is decomposed so that the focal positions differ for each wavelength in the vertical direction. In this embodiment, the laser light is decomposed into laser light L1 with a wavelength of 350 nm to laser light L2 with a wavelength of 1400 nm, and focal positions are formed over a range of 7 mm (7000 µm) in the vertical direction. With this configuration, if the surface 10a of the wafer 10 is at position Z1 indicated by the solid line in Fig. 2(b), the focal position of the laser light L1 (wavelength 350 nm) will coincide with the focal position of the laser light L1, and light with a wavelength of 350 nm will be primarily reflected from the surface 10a of the wafer 10. If the surface 10a' of the wafer 10' is at position Z2 below indicated by the dashed-dotted line in Fig. 2(b), the focal position of the laser light L2 (wavelength 1400 nm) will coincide with the focal position of the laser light L2, and light with a wavelength of 1400 nm will be primarily reflected from the surface 10a' of the wafer 10'. Furthermore, if the surface 10a of the wafer 10 is located somewhere between positions Z1 and Z2, laser light of any wavelength between 350 nm and 1400 nm corresponding to that position will be primarily reflected. Furthermore, by providing the pinhole mask 56 having the pinholes 56a described above, only the wavelength that is mainly reflected is efficiently guided to the diffraction grating 57, and the laser light is irradiated at a position corresponding to the wavelength of the light receiving element in the wavelength detector 58, and the wavelength of the laser light that is mainly reflected by the workpiece can be accurately identified.

[0021] The wavelength signal of the wavelength identified and output by the wavelength detector 58 is transmitted to the control means 100, where it is compared with Table T, pre-stored in the control means 100, in a comparison unit 110 configured in the control means 100 based on the wavelength. As shown on the right side of FIG. 2(a), Table T identifies the wavelength of the light detected by the wavelength detector 58 within the range of 350 nm to 1400 nm, thereby enabling the height position to be determined relative to the focal position of the laser light with a wavelength of 350 nm as a reference (0 mm). Since the wavelength detector 58 in this embodiment is configured with a high-resolution light-receiving element, comparison with Table T enables the height position of the workpiece surface to be accurately determined in 0.5 μm increments. In addition to the comparison unit 110, the control means 100 also includes a grinding completion determination unit 120 for executing the grinding completion step. The function and operation of the grinding completion determination unit 120 will be described later.

[0022] The grinding apparatus 1 suitable for this embodiment has roughly the configuration as described above, and a wafer processing method carried out using the grinding apparatus 1 will be described below.

[0023] As shown in Figure 3(a), the workpiece in this embodiment is a circular silicon substrate wafer 10, for example, with a diameter of 150 mm. One surface of the wafer 10, i.e., the central portion of the surface 10a shown in the figure, is formed with a post region 14 in which a plurality of fine posts 12 made of nickel are formed, and an annular peripheral excess region 16 surrounding the post region 14. The diameter of the post region 14 is, for example, 138 mm, and the width of the peripheral excess region 16 is 6 mm. As shown in Figure 3(a), which shows an enlarged portion of the post region 14, the posts 12 are generally cylindrical, with a diameter of 0.5 mm, the spacing between adjacent posts 12 being 0.5 mm, and the height before grinding being 80 µm. As can be seen from Figure 3(b), which shows the AA cross section of Figure 3(a), the height of the posts 12 before processing (80 µm) is based on the height of the peripheral surplus region 16, and in this embodiment, the height of the posts 12 is ground to the desired height (25 µm). The other surface (back surface 10b) of the wafer 10 does not have the above-mentioned posts 12 and is a flat surface. In addition, the dashed line 11 that separates the post region 14 and the peripheral surplus region 16 on the front surface 10a of the wafer 10 shown in Figure 3(a) is added for convenience of explanation and is not actually shown.

[0024] When carrying out the wafer processing method of this embodiment, as shown in FIG. 3(a), the back surface 10b side of the wafer 10 is placed on the chuck table 32, and a suction means (not shown) is activated to suction-hold the wafer 10 on the chuck table 32 (holding process).

[0025] Next, the moving means is operated to move the chuck table 32 in the X-axis direction, and as shown in FIG. 4, the peripheral excess region 16 of the wafer 10 is positioned directly below the detection unit 51 of the laser displacement meter 5. As described above, the laser displacement meter 5 can also be moved in the X-axis direction in the main body 21 of the apparatus housing 2, so it is also possible to move the chuck table 32 to the processing region directly below the grinding means 4, and then fine-adjust the position of the laser displacement meter 5 so that the peripheral excess region 16 of the wafer 10 is positioned directly below the detection unit 51 of the laser displacement meter 5. Next, the laser displacement meter 5 is operated to spray high-pressure air 50 from the laser irradiation port 51b of the detection unit 51, and to irradiate laser light L0 from the light source 52, and to detect the wavelength λ1 of the laser light reflected by the surface 10a of the peripheral excess region 16 of the wafer 10 held on the chuck table 32. In this embodiment, the position of the detection unit 51 of the laser displacement meter 5 is adjusted in advance so that the surface 10a of the wafer 10 is located between the focal position of the laser light L1 with a wavelength of 350 nm and the focal position of the laser light L2 with a wavelength of 1400 nm, and the wavelength λ1 is detected at a substantially midpoint between 350 nm and 1400 nm. When detecting the height position of the surface 10a of the outer circumferential surplus region 16, the chuck table 32 may be rotated in the direction indicated by arrow R1 in FIG. 4, and the average value of the wavelengths of the laser light reflected at a plurality of positions may be calculated as the wavelength λ1.

[0026] Here, the wavelength λ1 (e.g., 735.1 nm) detected by the wavelength detector 58 as described above is transmitted to the comparison unit 110 of the control means 100, and by comparing the wavelength λ1 with table T, it is detected that the height position of the surface of the outer periphery surplus region 16 is Z3 (e.g., 3675.5 μm) (outer periphery height detection step). The value of Z3 is stored in the grinding completion determination unit 120 disposed in the control means 100. Note that, as described above, the height position Z3 obtained by comparing the detected wavelength λ1 with table T is the distance from a position based on the focal position of the laser light L1 having a wavelength of 350 nm, and the reference position is set to be sufficiently above the surface 10 a of the wafer 10.

[0027] Next, the moving means is operated to move chuck table 32 to the processing area directly below grinding means 4, and the center of rotation of chuck table 32 is positioned where grinding wheel 426 of grinding means 4 passes, as shown in Fig. 5. Next, rotating spindle 422 of grinding means 4 is rotated in the direction indicated by arrow R2 at a predetermined rotational speed (e.g., 2000 rpm), and rotation drive means (not shown) is operated to rotate chuck table 32 in the direction indicated by arrow R3 at a predetermined rotational speed (e.g., 100 rpm). Next, the grinding feed means 7 is operated to lower the grinding means 4 in the direction indicated by the arrow R4, bringing it close to the surface 10a of the wafer 10 held on the chuck table 32, and while supplying a processing fluid (grinding water) not shown, the grinding stone 426 arranged on the underside of the grinding wheel 425 is brought into contact with the post region 14 on the surface 10a of the wafer 10, and the post region 14 on the surface 10a of the wafer 10 is ground at a predetermined lowering speed (e.g., 0.5 μm / sec) (grinding process).

[0028] When the above-described grinding process is performed, the grinding completion process described below is performed in parallel. More specifically, as shown in FIG. 5, the detection unit 51 of the laser displacement meter 5 is positioned above the post region 14 of the wafer 10 held on the chuck table 32. If the chuck table 32 has been moved to the vicinity of the processing region when the above-described outer periphery height detection process is performed, it is only necessary to finely adjust the position of the detection unit 51 of the laser displacement meter 5. Next, high-pressure air 50 is sprayed from the laser irradiation port 51b of the detection unit 51 toward the post region 14, and laser light L0 is irradiated from the light source 52. When the grinding process is performed, a processing fluid (grinding water) is supplied onto the front surface 10a of the wafer 10, and the processing fluid containing grinding debris overflows outward from the grinding wheel 425, covering the front surface 10a of the wafer 10. However, as described above, high-pressure air 50 is sprayed from laser irradiation port 51b of detection unit 51, so the machining fluid is removed from the predetermined position (on the circumference indicated by dashed line 18) that serves as the measurement portion of post region 14 where the laser light is irradiated. Then, while chuck table 32 makes one rotation, wavelength λ2 of the laser light reflected at predetermined position 18 of post region 14 is detected by wavelength detector 58.

[0029] As described with reference to FIG. 3, the post region 14 is formed with a plurality of minute posts 12. Therefore, the wavelength detected by the wavelength detector 58 repeatedly varies between the wavelength λ1 of the laser light reflected at the height of the surface 10a where the posts 12 are located (the same height as the peripheral excess region 16) and the wavelength λ2 (λ2<λ1) of the laser light reflected at the top of the posts 12. If the wavelength λ2 is, for example, 719.1 nm before the grinding process or immediately after the grinding process is started, the height position Z4 of the posts 12 before or at the beginning of grinding is detected as, for example, 3595.5 μm by comparing the wavelength λ2 (719.1 nm) with the table T. The value of Z4 is constantly stored in the grinding completion determination unit 120, and the specific height of the posts 12 is detected by repeatedly calculating the difference between Z3 and Z4. The data on the height of the post 12 detected based on the detected wavelength is shown in a graph, for example, as shown on the left side of FIG.

[0030] During the grinding process, the grinding completion determination unit 120 repeatedly calculates the difference between Z3 and Z4 at a frequency of, for example, 10 kHz (10,000 times per second) to determine whether the height of the post 12 has reached a predetermined value (25 μm in this embodiment). If the height of the post 12 has not reached the predetermined value (25 μm), the grinding process continues. As the grinding process progresses and the post 12 is ground, the wavelength λ2 of the laser light reflected from the top of the post 12 becomes 730.1 nm, and the height position Z4 detected by comparing the wavelength λ2 with table T becomes 3650.5 μm. As a result, it is determined that the difference between the height positions Z3 (3675.5 μm) and Z4 (3650.5 μm) of the surface 10a of the outer circumferential excess region 16 has reached 25 μm, as can be seen from the graph shown on the right side of FIG. 6. Based on this determination, the end of the grinding process is instructed by the control means 100. As a result, the wafer 10 is brought into the desired state as shown in Fig. 7, and the grinding process and grinding completion process are completed.

[0031] Incidentally, when performing the grinding completion step as described above, the height state of the post regions 14 can be displayed in a graph as shown in FIG. 8 based on the wavelength detected by the wavelength detector 58. The graph shows in detail the surface 10a of the wafer 10 and the shape of the posts 12. By examining the shape of the graph (16C, 16D) shown in FIG. 8 during or after the grinding step is completed, at least one of a broken post 12 as shown in A in the figure or a chipped post 12 as shown in B in the figure can be detected. Such detection can be performed by an operator managing the grinding apparatus 1 visually checking the graph displayed on a monitor (not shown) connected to the control means 100, or it can be automatically detected (checking step) using an image processing program stored in the control means 100. Providing such a checking step not only helps with wafer quality control when performing the wafer processing method described above, but also allows for the prompt determination of appropriate processing conditions for the wafer processing method that will prevent breakage or chipping of the posts 12.

[0032] According to this embodiment, when grinding a wafer having a post region on one side where multiple fine posts are formed and a peripheral excess region surrounding the post region, the problem of difficulty in grinding the post height to the desired height can be resolved. [Explanation of symbols]

[0033] 1: Grinding device 2: Device housing 21: Main body 22: Upright wall 3: Holding means 32: Chuck table 4: Grinding means 41: Mobile base 42: Spindle unit 421: Spindle housing 422: Rotating spindle 423: Servo motor 424: Wheel mount 425: Grinding wheel 426: Grinding wheel 5: Laser displacement meter 51: Detection unit 51a: Air flow path 51b: Laser emission port 52: Light source 53: Beam splitter 54: Projection lens 55A, 55B: Convex lenses 56: Pinhole mask 56a: Pinhole 57: Diffraction grating 58: Wavelength detector 6a, 6b: bellows means 7: Grinding feed means 100: Control means 110: Matching unit 120: Grinding completion determination section

Claims

1. A method for processing a wafer having a post region in which a plurality of fine posts are formed and a peripheral excess region surrounding the post region formed on one surface, comprising: a holding step of holding the other surface of the wafer on a chuck table; a peripheral height detecting step of detecting the height position of the surface of the peripheral excess region of the wafer held on the chuck table by a laser displacement meter; a grinding step in which, after the outer periphery height detection step has been carried out, the chuck table is rotated, and a grinding means having a rotatable grinding wheel with grinding stones arranged annularly is brought close to the wafer held on the chuck table, and the post region of the wafer is ground so that the grinding stone passes through the center of rotation of the wafer; a grinding termination step in which, during the grinding step, a height position of the post to be ground in the post region is detected by a laser displacement meter, and the grinding step is terminated when a difference between the height position of the post and the height position of the surface of the outer periphery excess region detected by the outer periphery height detection step reaches a predetermined value; A wafer processing method comprising:

2. 2. The wafer processing method according to claim 1, wherein at least one of breakage and chipping of the post is detected in the grinding completion step.

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