JP7503938B2 - How to inspect the holding surface - Google Patents

Description

The present invention relates to a method for inspecting the holding surface of a chuck table in a grinding machine.

A grinding device is known that is used to grind plate-shaped workpieces such as semiconductor wafers and reduce their overall thickness by mounting a grinding wheel with grinding stones arranged in a ring shape on a spindle (see, for example, Patent Document 1).

Japanese Patent No. 5841846

In general, the grinding machine uses in-feed grinding, in which the axis of rotation of the chuck table is inclined relative to the axis of rotation of the spindle, and grinds only the radius of the workpiece held on the chuck table that rotates around the axis of rotation. The holding surface of the chuck table that holds the workpiece is ground by a grinding wheel attached to the spindle to form a very low conical shape. In the conical shape, the processing area where the grinding wheel contacts the held workpiece is adjusted to be almost parallel to the lower surface of the grinding wheel, and the non-processing area where the grinding wheel does not contact the held workpiece is adjusted to be lower than the processing area. If the conical shape (height) of the holding surface of the grinding machine changes, the thickness of the wafer after grinding will vary and not be uniform, that is, it will cause in-plane thickness variation.

Therefore, the grinding machine needs to inspect the shape of the holding surface, which traditionally requires the operator to remove the grinding wheel, attach a measuring device to the spindle, and measure the height of the holding surface while checking the measuring device's reading, a task that requires skill and time.

The present invention was made in consideration of these points, and its purpose is to provide a method for inspecting a holding surface that can easily measure the shape of the holding surface.

In order to solve the above-mentioned problems and achieve the object, the present invention provides a method for inspecting a holding surface of a grinding device that performs in-feed grinding on a workpiece, the method comprising: a rotatable chuck table that holds a workpiece on the holding surface; a rotatable grinding unit having a grinding wheel with grinding wheels arranged in an annular shape attached to its tip; a grinding feed unit that moves the grinding unit toward the chuck table; and an inclination adjustment unit that relatively adjusts the inclination of a rotation axis of the chuck table and a rotation axis of the grinding unit, the method comprising the steps of: inspecting the shape of the holding surface of the conical chuck table in the grinding device that performs in-feed grinding on the workpiece; the holding step of holding an evaluation workpiece on the holding surface of a chuck table; a grinding groove forming step of grinding the evaluation workpiece with the grinding wheel while the rotation of the chuck table is stopped, and forming an arc-shaped grinding groove in the evaluation workpiece along a moving trajectory of the grinding wheel that passes through the rotation center of the chuck table; a holding surface shape calculating step of measuring the thickness of a portion of the substrate of the evaluation workpiece remaining at the bottom of the grinding groove at a plurality of positions, and calculating the shape of the conical holding surface; and a determination step of determining whether the calculated shape of the holding surface is within an acceptable range.

In addition, in the method for inspecting the holding surface, the grinding groove forming step may form a grinding groove that continues from the peripheral portion of the evaluation workpiece where the grinding wheel cuts through, through the center of rotation of the chuck table, and to the peripheral portion of the evaluation workpiece where the grinding wheel cuts through.

The method for inspecting the holding surface may further include a holding surface correction step of grinding the holding surface with the grinding wheel while rotating the chuck table prior to the step of holding the workpiece for evaluation, and the grinding groove forming step may include inspecting the shape of the corrected holding surface using the grinding wheel that has ground the holding surface.

The method for inspecting the holding surface of the present invention has the effect of making it easy to measure the shape of the holding surface.

FIG. 1 is a side view, partially in section, that typically shows a main part of a grinding machine in which the shape of a holding surface is inspected by a method for inspecting a holding surface according to a first embodiment. FIG. 2 is a perspective view showing an example of a workpiece to be processed by the grinding apparatus shown in FIG. FIG. 3 is a plan view showing the positional relationship between the chuck table, the grinding unit, and the height fine adjustment unit of the inclination adjustment unit of the grinding apparatus shown in FIG. FIG. 4 is a flowchart showing the flow of the holding surface inspection method according to the first embodiment. FIG. 5 is a side view showing a step of holding an evaluation workpiece in the method of inspecting the holding surface shown in FIG. FIG. 6 is a plan view showing the positional relationship between the chuck table, the grinding unit, and the height fine adjustment unit of the inclination adjustment unit in the grinding groove forming step of the holding surface inspection method shown in FIG. FIG. 7 is a side view seen from the direction of arrow VII in FIG. FIG. 8 is a side view seen from the direction of arrow VIII in FIG. FIG. 9 is a side view seen from the direction of arrow IX in FIG. FIG. 10 is a plan view of an evaluation workpiece in which a grinding groove is formed, the thickness of which is to be measured in the holding surface shape calculation step of the holding surface inspection method shown in FIG. FIG. 11 is a flowchart showing the flow of a holding surface inspection method according to the second embodiment. FIG. 12 is a side view showing an example of the holding surface correction step of the holding surface inspection method shown in FIG. 11 at the start of the holding surface correction step. FIG. 13 is a side view showing an example of the holding surface correction step of the holding surface inspection method shown in FIG. 11 at the end of the step.

The following describes in detail the form (embodiment) for carrying out the present invention with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Various omissions, substitutions, or modifications of the configuration can be made without departing from the spirit of the present invention.

[Embodiment 1]
A method for inspecting a holding surface according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a side view showing a schematic partial cross section of a main part of a grinding device in which the shape of a holding surface is inspected by the method for inspecting a holding surface according to the first embodiment. Fig. 2 is a perspective view showing an example of a workpiece to be machined by the grinding device shown in Fig. 1. Fig. 3 is a plan view showing the positional relationship of a chuck table, a grinding unit, and a height fine adjustment unit of a tilt adjustment unit of the grinding device shown in Fig. 1. Fig. 4 is a flow chart showing the flow of the method for inspecting a holding surface according to the first embodiment.

The method for inspecting a holding surface according to the first embodiment is a method for calculating the shape of the holding surface 11 of the grinding device 1 shown in FIG. 1. The grinding device 1 shown in FIG. 1 is a processing device that performs in-feed grinding on the workpiece 200 shown in FIG. 2. First, the workpiece 200 that is the object of processing by the grinding device 1 will be described.

(Workpiece)
In the first embodiment, a workpiece 200 to be processed by the grinding apparatus 1 shown in Fig. 1 is a disk-shaped semiconductor wafer or optical device wafer having a substrate 201 made of silicon, sapphire, gallium arsenide, or the like. As shown in Fig. 1, the workpiece 200 has devices 204 formed in each of a plurality of regions partitioned by a plurality of planned division lines 203 that intersect (orthogonal in the first embodiment) on a surface 202 of the substrate 201.

The device 204 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), or a MEMS (Micro Electro Mechanical System). The workpiece 200 has a protective member 210 attached to the surface 202 side of the substrate 201, and the surface 202 side is suction-held to the holding surface 11 via the protective member 210, and the back surface 205 behind the surface 202 is infeed-ground. Next, the grinding device 1 that grinds the workpiece 200 will be described.

(Grinding equipment)
1, the grinding device 1 is a processing device that grinds the back surface 205 side of a substrate 201 of a workpiece 200 to thin the workpiece 200 to a predetermined finishing thickness. As shown in FIG. 1, the grinding device 1 includes an apparatus base 2, a chuck table 10, a grinding unit 20, a grinding feed unit 30, a tilt adjustment unit 40, and a control unit 100.

The chuck table 10 holds the surface 202 side of the workpiece 200 with the holding surface 11, and is rotatable around a rotation axis 112 shown by a dashed line in FIG. 1 that passes through the center 111 (corresponding to the center of rotation) of the holding surface 11. In the first embodiment, the holding surface 11 of the chuck table 10 is made of porous ceramics or the like, and is connected to a vacuum suction source (not shown) through a vacuum suction path (not shown) formed under the holding surface 11. The surface 202 side of the workpiece 200 is placed on the holding surface 11 of the chuck table 10 via a protective member 210, and the holding surface 11 is sucked by the vacuum suction source, thereby sucking and holding the workpiece 200 placed on the holding surface 11.

In the first embodiment, the chuck table 10 is mounted on a moving table 3 that is moved in the X-axis direction parallel to the horizontal direction by an X-axis moving unit (not shown). The chuck table 10 is rotated around a rotation axis 112 by a rotary drive source 4. The moving table 3 is moved in the X-axis direction by the X-axis moving unit so that it is located at a processing position where the workpiece 200 held on the chuck table 10 is ground by the grinding unit 20, and at a loading/unloading position where the workpiece 200 is loaded onto the chuck table 10 or unloaded from the chuck table 10.

The holding surface 11 has a circular planar shape and is formed into a cone shape with the outer edge 113 slightly lower than the center 111. That is, the holding surface 11 is formed into a cone surface with the center 111 as the apex, and is formed into an inclined surface having a downward slope from the center 111 to the outer edge 113. The chuck table 10 holds the workpiece 200 to be machined along the conical surface of the holding surface 11. Note that while FIG. 1 shows the inclination of the conical surface of the holding surface 11 exaggerated, the inclination of the conical surface of the holding surface 11 is actually so slight that it cannot be seen with the naked eye.

The rotation axis 112, which is the center of rotation of the chuck table 10, is arranged at a slight incline with respect to the vertical direction. In the first embodiment, the processing area 114 (shown by parallel diagonal lines in Figs. 3 and 6) that faces the grinding wheel 25 of the grinding unit 20 on the holding surface 11 of the chuck table 10 in the processing position along the vertical direction and includes the center 111 is arranged parallel to the horizontal direction as shown in Fig. 3 when the grinding device 1 makes the thickness of the workpiece 200 after grinding uniform (suppressing the thickness variation as much as possible). Also, in the first embodiment, the non-processing area 115 that does not face the grinding wheel 25 of the grinding unit 20 on the holding surface 11 of the chuck table 10 in the processing position in the vertical direction is lower than the processing area 114 when the grinding device 1 makes the thickness of the workpiece 200 after grinding uniform, and is arranged gradually lower toward the outer edge 113. Note that FIG. 1 exaggerates the inclination 120 of the rotation axis 112 relative to the vertical direction, but in reality, the inclination 120 of the rotation axis 112 relative to the vertical direction is so slight that it cannot be seen with the naked eye.

The grinding unit 20 has a spindle 22 that has a grinding wheel 21 attached to its lower end, which is the tip, and is rotatable around a rotation axis 221 that is perpendicular to the X-axis direction and parallel to the vertical direction, and grinds the back surface 205 side of the substrate 201 of the workpiece 200 held on the chuck table 10 with the grinding stone 25 of the grinding wheel 21. The grinding unit 20 is supported on the device base 2 via the grinding feed unit 30. The grinding unit 20 includes the grinding wheel 21, the spindle 22, and a spindle motor 23.

The grinding wheel 21 grinds the workpiece 200 held on the chuck table 10. The grinding wheel 21 includes a disk-shaped wheel base 24 and grinding stones 25 arranged in a ring shape on the outer edge of the lower surface of the wheel base 24. That is, the grinding wheel 21 has grinding stones 25 arranged in a ring shape.

The grinding wheels 25 are arranged at equal intervals in the circumferential direction on the underside of the wheel base 24 facing the chuck table 10. In the first embodiment, the grinding wheels 25 are configured as a single so-called segmented grinding wheel formed into a single lump by mixing abrasive grains such as diamond or CBN (Cubic Boron Nitride) with a bonding material (also called a bond material) made of metal, ceramic, resin, or the like.

The grinding wheel 21 is driven by the spindle motor 23 to rotate the spindle 22 around the rotation axis 221, causing the grinding stone 25 to grind the back surface 205 of the workpiece 200 held on the chuck table 10.

The spindle 22 supports the grinding wheel 21 by fixing it to its lower end. The spindle 22 is rotatably housed in a spindle housing 26 that is supported by the grinding feed unit 30 so as to be movable in the vertical direction. The rotation axis 221 of the spindle 22 of the grinding unit 20 is disposed along the Z-axis direction that is perpendicular to the X-axis direction and parallel to the vertical direction. The spindle motor 23 rotates the spindle 22 around the rotation axis 221.

In the first embodiment, the rotation axis 221 of the grinding unit 20 is horizontally separated from the rotation axis 112 of the chuck table 10, and the movement trajectory of the grinding wheel 25 of the grinding wheel 21 when the spindle 22 rotates is located on the center 111 of the chuck table 10. Also, in the first embodiment, when the grinding device 1 makes the thickness of the workpiece 200 after grinding uniform (suppressing the variation in thickness as much as possible), the lower surface of the grinding wheel 25 is parallel to the processing area 114 of the holding surface 11 of the chuck table 10.

The grinding feed unit 30 is installed on the device base 2 and moves the spindle 22 of the grinding unit 20 in the Z-axis direction, which is the grinding feed direction. The grinding feed unit 30 lowers the spindle 22 of the grinding unit 20 and moves the grinding unit 20 toward the chuck table 10 at the processing position. The grinding feed unit 30 raises the spindle 22 of the grinding unit 20 and moves the grinding unit 20 away from the chuck table 10 at the processing position.

The grinding feed unit 30 includes a well-known ball screw 31 that is arranged parallel to the Z-axis direction and is rotatable about its axis, a motor 32 that rotates the ball screw 31 about its axis to move the spindle 22 in the Z-axis direction via the spindle housing 26, and a well-known guide rail (not shown) that supports the grinding unit 20 so that it can move in the Z-axis direction.

The tilt adjustment unit 40 adjusts the tilt 120 between the rotation axis 112 of the chuck table 10 and the rotation axis 221 of the grinding unit 20 relative to each other. In the first embodiment, the tilt adjustment unit 40 is attached to the chuck table 10 and adjusts (changes) the orientation of the rotation axis 112 of the chuck table 10. As shown in FIG. 1, the tilt adjustment unit 40 includes a support base 41 and a height fine adjustment unit 42. The support base 41 includes a cylindrical support tube portion 411 that rotatably supports the chuck table 10 around the rotation axis 112 via a bearing (not shown), and a flange portion 412 that expands in diameter from the lower end of the support tube portion 411. The tilt adjustment unit 40 adjusts the tilt 120 of the rotation axis 112 by adjusting the tilt of the flange portion 412.

Two or more height fine adjustment units 42 are provided at intervals in the radial direction of the flange portion 412. In the first embodiment, the tilt adjustment unit 40 has three height fine adjustment units 42 provided at intervals in the radial direction on the underside of the flange portion 412, as shown in FIG. 3.

1, the height fine adjustment unit 42 includes a cylindrical portion 421 fixed to the moving table 3, a shaft 422 penetrating the cylindrical portion 421, a driving portion 423 connected to the lower end of the shaft 422, and a fixed portion 424 fixed to the flange portion 412 at the upper end of the shaft 422. The driving portion 423 includes a motor 425 that rotates the shaft 422, and a reducer 426 that reduces the rotational speed of the shaft 422 and is fixed to the moving table 3.

The fixed part 424 is screwed into a male screw (not shown) formed on the upper end of the shaft 422. The height fine adjustment unit 42 changes the height of the fixed part 424 fixed to the flange part 412 by rotating the shaft 422 about its axis via the reducer 426, thereby adjusting the inclination 120 of the rotation axis 112.

The control unit 100 processes multiple types of signals from each of the above-mentioned mechanisms constituting the grinding device 1 and controls each of the mechanisms. In other words, the control unit 100 causes the grinding device 1 to execute a machining operation on the workpiece 200. The control unit 100 is a computer that has an arithmetic processing device having a microprocessor such as a CPU (Central Processing Unit), a storage device having a memory such as a ROM (Read Only Memory) or RAM (Random Access Memory), and an input/output interface device, and is capable of executing computer programs.

The arithmetic processing unit of the control unit 100 executes a computer program stored in the ROM on the RAM to generate control signals for controlling the grinding device 1. The arithmetic processing unit of the control unit 100 outputs the generated control signals to each component of the grinding device 1 via the input/output interface device.

The control unit 100 is also connected to a display means (not shown) configured with a liquid crystal display device or the like that displays the status of the processing operation and images, and to an input means used by the operator to register processing content information, etc. The input means is configured with at least one of a touch panel provided on the display means and a keyboard, etc.

The grinding device 1 described above holds the surface 202 side of the workpiece 200 on the holding surface 11 of the chuck table 10 by suction via the protective member 210, positions the chuck table 10 at the processing position, and rotates the grinding wheel 21 around the rotation axis 221 and the chuck table 10 around the rotation axis 112 while supplying grinding fluid to the workpiece 200. The grinding device 1 abuts the grinding wheel 25 of the grinding wheel 21 against the back surface 205 of the substrate 201 of the workpiece 200, and moves the grinding unit 20 closer to the chuck table 10 at a predetermined feed rate with the grinding feed unit 30, grinds the back surface 205 of the workpiece 200 with the grinding wheel 25, and thins the workpiece 200. In this way, the grinding device 1 according to the first embodiment performs so-called in-feed grinding, in which the chuck table 10, which holds the workpiece 200 while maintaining its horizontal position at the processing position, rotates about the rotation axis 112 while the grinding stone 25 of the grinding wheel 21, which is rotated about the rotation axis 221 by the spindle 22, moves from top to bottom relative to the workpiece 200 held on the chuck table 10 to thin the workpiece 200. The grinding device 1 thins the workpiece 200 so that the thickness of the workpiece 200 is uniform at the finishing thickness. Next, a method for inspecting the holding surface will be described.

(Method of inspecting holding surface)
The method for inspecting the holding surface according to the first embodiment is a method for inspecting the shape of the conical holding surface 11 by calculating the difference in height in the Z-axis direction between the center 111 of the conical holding surface 11 shown in FIG. 1 and two points 113-1, 113-2 of the outer edge (shown in FIG. 3 and the like, hereinafter referred to as the first outer edge and the second outer edge). In the present invention, inspecting the shape of the conical holding surface 11 is a method for calculating the difference in height in the Z-axis direction between the center 111 of the conical holding surface 11 and the outer edge portions 113-1, 113-2, and calculating the shape of the holding surface 11. In addition, in the first embodiment, the first outer edge portion 113-1 is located on one height fine adjustment unit 42, and the second outer edge portion 113-2 is located on the other height fine adjustment unit 42. As shown in FIG. 4, the method of inspecting the holding surface includes an evaluation workpiece holding step 1001, a grinding groove forming step 1002, a holding surface shape calculation step 1003, and a judgment step 1004.

(Evaluation workpiece holding step)
5 is a side view showing the evaluation workpiece holding step of the holding surface inspection method shown in FIG. 4. The evaluation workpiece holding step 1001 is a step of holding the evaluation workpiece 220 on the holding surface 11 of the chuck table 10. In the first embodiment, the evaluation workpiece 220 is a dummy wafer, for example, in which the device 204 is not formed on the surface 202. In the first embodiment, the evaluation workpiece 220 is a dummy wafer in which the material constituting the substrate 201, the outer diameter, and the thickness are the same as those of the workpiece 200 before grinding. In the present invention, the evaluation workpiece 220 may be a product wafer (workpiece 200) in which the device 204 is formed, and in that case, the amount of grinding during inspection is not to reach the finishing thickness.

In evaluation workpiece holding step 1001, the evaluation workpiece 220 is placed on the holding surface 11 of the chuck table 10, and the grinding device 1 suction-holds the evaluation workpiece 220 on the holding surface 11 of the chuck table 10. Note that the same parts of the evaluation workpiece 220 as those of the workpiece 200 are given the same reference numerals and will not be described.

(Grinding groove forming step)
Fig. 6 is a plan view showing the positional relationship between the chuck table, the grinding unit, and the height fine adjustment unit of the tilt adjustment unit in the grinding groove forming step of the holding surface inspection method shown in Fig. 4. Fig. 7 is a side view seen from the direction of arrow VII in Fig. 6. Fig. 8 is a side view seen from the direction of arrow VIII in Fig. 6. Fig. 9 is a side view seen from the direction of arrow IX in Fig. 6.

The grinding groove forming step 1002 is a step in which the evaluation workpiece 220 is ground with the grinding wheel 21 while the rotation of the chuck table 10 around the rotation axis 112 is stopped, and an arc-shaped grinding groove 230 is formed in the evaluation workpiece 220 along the movement trajectory of the grinding wheel 25 that passes through the center 111 of the chuck table 10.

In the grinding groove formation step 1002, the grinding device 1 positions the chuck table 10 at the processing position, and rotates the grinding wheel 21 around the rotation axis 221 using the spindle 22 while supplying grinding fluid to the evaluation workpiece 220 without rotating the chuck table 10 around the rotation axis 112. In the grinding groove forming step 1002, the grinding device 1 brings the grinding stone 25 of the grinding wheel 21 into contact with the back surface 205 of the substrate 201 of the evaluation workpiece 220, and the grinding feed unit 30 moves the grinding unit 20 closer to the chuck table 10 at a predetermined feed speed, grinding the back surface 205 of the evaluation workpiece 220 with the grinding stone 25, forming a grinding groove 230 having an arc-shaped planar shape along the movement trajectory of the grinding stone 25 passing through the center 111 of the chuck table 10 on the back surface 205 of the workpiece 200, as shown in Figures 6, 7, 8, and 9.

In the first embodiment, in the grinding groove forming step 1002, the grinding device 1 moves the grinding unit 20 toward the chuck table 10 in the Z-axis direction by a distance less than the thickness of the evaluation workpiece 220 after the grinding wheel 25 abuts against the back surface 205 of the evaluation workpiece 220, using the grinding feed unit 30 to form a grinding groove 230 in which a part of the substrate 201 remains at the bottom (hereinafter, the part of the substrate 201 remaining at the bottom of the grinding groove 230 is referred to as the grinding remaining portion 231). The Z-axis thickness 232 of the grinding remaining portion 231 at the bottom of each position of the grinding groove 230 is a value corresponding to the distance between the holding surface 11 and the grinding wheel 25 at each position, that is, a value corresponding to the height of the holding surface 11 in the Z-axis direction at each position, and a value corresponding to the shape of the holding surface 11. Thus, in the grinding groove forming step 1002, a grinding groove 230 is formed that continues from the peripheral portion 224 on the first outer edge portion 113-1 of the evaluation workpiece 220 where the grinding wheel 25 cuts through, through the center 111 of the chuck table 10, to the peripheral portion 225 on the second outer edge portion 113-2 of the evaluation workpiece 220 where the grinding wheel 25 cuts through.

(Holding surface shape calculation step)
Fig. 10 is a plan view of an evaluation workpiece having a grinding groove formed therein, the thickness of which is measured in the holding surface shape calculation step of the holding surface inspection method shown in Fig. 4. The holding surface shape calculation step 1003 is a step of measuring the thickness 232 of the remaining grinding portion 231 at the bottom of the grinding groove 230 corresponding to the grinding groove 230 at a plurality of positions, and calculating the shape of the conical holding surface 11.

In the first embodiment, in the holding surface shape calculation step 1003, the center 223 of the evaluation workpiece 220 superimposed on the center 111 of the chuck table 10 of the grinding groove 230 shown in FIG. 10 and the thickness 232 of the remaining grinding portion 231 of the peripheral portions 224 and 225 are measured. Note that in the present invention, the positions for measuring the thickness 232 of the remaining grinding portion 231 are not limited to the center 223 and the peripheral portions 224 and 225.

In addition, in the holding surface shape calculation step 1003, the thickness 232 of the grinding remaining portion 231 at any one of the positions where the thickness 232 of the grinding remaining portion 231 is measured is set as a reference (zero), and the difference between the thickness 232 of the grinding remaining portion 231 at the reference position and the thickness 232 of the grinding remaining portion 231 at the other positions is calculated. For example, the difference between the thickness 232 of the grinding remaining portion 231 at the reference position and ... is shown as a negative value, and the difference between the thickness 232 of the grinding remaining portion 231 at the reference position and the thickness 232 of the grinding remaining portion 231 at the reference position and the thickness 232 of the grinding remaining portion 231 at the reference position and the thickness 232 of the grinding remaining portion 231 at the reference position is shown as a positive value. In the first embodiment, the thickness 232 of the remaining grinding portion 231 at the center 223 is set as the reference (zero), the thickness 232 of the peripheral portion 224 is zero, and the thickness 232 of the peripheral portion 225 is +30 μm. Thus, in the first embodiment, in the holding surface shape calculation step 1003, the difference in height in the Z-axis direction between the center 111 of the holding surface 11 and the outer edges 113-1 and 113-2 is calculated.

(Determination step)
The judgment step 1004 is a step for judging whether the calculated shape of the holding surface 11 is within an allowable range. In the first embodiment, in the judgment step 1004, if the largest difference among the differences from the thickness 232 of the remaining portion 231 at one position set as a reference is within a predetermined allowable range (above a lower limit and below an upper limit), the holding surface 11 is judged to be suitable for grinding the workpiece 200. In addition, in the judgment step 1004, if the largest difference among the differences from the thickness 232 of the remaining portion 231 at one position set as a reference is outside a predetermined allowable range (below a lower limit or above an upper limit), the holding surface 11 is judged to be unsuitable for grinding the workpiece 200. If it is judged that the holding surface 11 is unsuitable for grinding the workpiece 200, the tilt 120 of the rotation axis 112 is adjusted by the height fine adjustment unit 42 of the tilt adjustment unit 40. Specifically, the specified tolerance range can be set such that the difference in height between the holding surface 11 at the peripheral portion 224 and the holding surface 11 at the center 223 is 3 μm or less, the holding surface 11 at the peripheral portion 225 is lower than the holding surface 11 at the center 223, and the difference in height between 20 μm or more and 40 μm or less.

As described above, the method for inspecting the holding surface according to the first embodiment grinds the chuck table 10 holding the evaluation workpiece 220 without rotating it around the rotation axis 112, and forms the grinding groove 230 for evaluation in the evaluation workpiece 220, so that the height of each position of the holding surface 11 of the chuck table 10 can be transferred to the evaluation workpiece 220 as the thickness 232 of the grinding remaining portion 231 at the bottom of the grinding groove 230. For this reason, the method for inspecting the holding surface according to the first embodiment has the effect of being able to evaluate the height of the holding surface 11, i.e., the shape, without actually measuring the height of the holding surface 11, by simply measuring the thickness 232 of the grinding remaining portion 231 at the bottom of the grinding groove 230. As a result, the method for inspecting the holding surface according to the first embodiment has the effect of being able to easily measure the shape of the holding surface 11.

The method for inspecting the holding surface according to the first embodiment forms a grinding groove 230 that continues from the peripheral portion 224 of the evaluation workpiece 220 through the center 223 to the peripheral portion 225, so that the height of each position of the entire holding surface 11 is transferred to the evaluation workpiece 220 as the thickness 232 of the remaining grinding portion 231. As a result, the method for inspecting the holding surface according to the first embodiment can measure the shape of the entire holding surface 11 from the center 111 to the outer edge 13 of the holding surface 11 by measuring the thickness 232 of the remaining grinding portion 231 at the bottom of the grinding groove 230.

[Embodiment 2]
A method for inspecting a holding surface according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 11 is a flow chart showing the flow of the method for inspecting a holding surface according to the second embodiment. Fig. 12 is a side view showing an example of a start of a holding surface correction step of the method for inspecting a holding surface shown in Fig. 11. Fig. 13 is a side view showing an example of an end of a holding surface correction step of the method for inspecting a holding surface shown in Fig. 11. In the description of the second embodiment, the same reference numerals are assigned to the same parts as those in the first embodiment in Figs. 11, 12, 13, etc., and description thereof will be omitted.

The method for inspecting the holding surface according to the second embodiment is the same as that according to the first embodiment, except that it includes a holding surface correction step 1010 that is performed before the evaluation workpiece holding step 1001, as shown in FIG. 11. The holding surface correction step 1010 is a step of grinding the holding surface 11 with a grinding wheel 21 while rotating the chuck table 10 around the rotation axis 112, before the evaluation workpiece holding step 1001.

In the second embodiment, in the holding surface correction step 1010, the grinding device 1 positions the chuck table 10 at the processing position, and while supplying grinding fluid to the holding surface 11 of the chuck table 10, rotates the grinding wheel 21 around the rotation axis 221 by the spindle 22 and rotates the chuck table 10 around the rotation axis 112. In the holding surface correction step 1010, the grinding device 1 lowers the grinding wheel 25 of the grinding wheel 21 as shown by the arrow in FIG. 12, abuts it against the holding surface 11 of the chuck table 10, and moves the grinding unit 20 closer to the chuck table 10 at a predetermined feed rate by the grinding feed unit 30, and grinds the holding surface 11 of the chuck table 10 with the grinding wheel 25 as shown in FIG. 13.

In the second embodiment, in the holding surface correction step 1010, the grinding device 1 grinds the holding surface 11 until the entire processing area 114 of the holding surface 11 abuts the grinding wheel 25. In the holding surface inspection method according to the second embodiment, after the holding surface correction step 1010 is performed, the evaluation workpiece holding step 1001, the grinding groove forming step 1002, the holding surface shape calculation step 1003, and the judgment step 1004 are performed in the same order as in the first embodiment. In the holding surface inspection method according to the second embodiment, the grinding groove forming step 1002 uses the grinding wheel 21 that has ground the holding surface 11 to inspect the shape of the holding surface 11 corrected in the holding surface correction step 1010.

The method for inspecting the holding surface according to the second embodiment grinds the chuck table 10 holding the evaluation workpiece 220 without rotating it around the rotation axis 112, and similarly to the first embodiment, a grinding groove 230 for evaluation is formed in the evaluation workpiece 220. Therefore, by simply measuring the thickness 232 of the remaining grinding portion 231 at the bottom of the grinding groove 230, the shape of the holding surface 11 can be evaluated without actually measuring the holding surface 11, and the shape of the holding surface 11 can be easily measured.

In addition, the method for inspecting the holding surface according to the second embodiment includes a holding surface correction step 1010, so that the shape of the holding surface 11 that has been corrected so as to suppress the variation in thickness of the workpiece 200 after grinding is measured, and the effort required to adjust the inclination 120 of the rotation axis 112 of the holding surface 11 can be reduced.

In addition, in the method for inspecting the holding surface according to embodiment 2, the grinding groove forming step 1002 uses the grinding wheel 21 that has been used to grind the holding surface 11 in the holding surface correction step 1010. Therefore, by measuring the thickness 232 of the remaining portion 231 at the bottom of the grinding groove 230, the shape of the holding surface 11 can be reliably evaluated without actually measuring the holding surface 11.

The present invention is not limited to the above embodiment. In other words, various modifications can be made without departing from the gist of the present invention. In the present invention, the processing area 114 of the holding surface 11 does not have to be parallel to the lower surface of the grinding wheel 25. For example, the distance between the holding surface 11 and the lower surface of the grinding wheel 25 may gradually increase from the outer edge 113 to the center 111. In addition, in the present invention, when the thickness of the evaluation workpiece 220 is uniform, the depth of the grinding groove 230 may be measured in the holding surface shape calculation step 1003 instead of measuring the thickness 232 of the remaining grinding portion 231. In addition, in the present invention, the rotation direction of the spindle 22 and the chuck table 10 may be opposite to the relationship of the inclination 120 of the rotation axes 112, 221 of the chuck table 10 and the spindle 22 shown in Figures 7, 8, and 9. This is true not only when grinding the evaluation workpiece 220, but also when grinding the workpiece 200 with the device 204.

REFERENCE SIGNS LIST 1 Grinding device 10 Chuck table 11 Holding surface 20 Grinding unit 21 Grinding wheel 22 Spindle 25 Grinding stone 30 Grinding feed unit 40 Tilt adjustment unit 111 Center (center of rotation)
112 Rotation axis 120 Inclination 200 Workpiece 220 Workpiece for evaluation 221 Rotation axis 224, 225 Periphery 230 Grinding groove 231 Remaining portion after grinding 232 Thickness 1001 Evaluation workpiece holding step 1002 Grinding groove forming step 1003 Holding surface shape calculation step 1004 Judging step 1010 Holding surface correction step

Claims (3)

A grinding device for in-feed grinding a workpiece, the grinding device comprising: a rotatable chuck table for holding a workpiece on its holding surface; a rotatable grinding unit having a grinding wheel, the grinding wheels being arranged in an annular shape, attached to its tip; a grinding feed unit for moving the grinding unit toward the chuck table; and an inclination adjustment unit for relatively adjusting the inclination of a rotation axis of the chuck table and a rotation axis of the grinding unit, the grinding device performing in-feed grinding of a workpiece, the method comprising the steps of: inspecting the shape of the conical holding surface of the chuck table;
an evaluation workpiece holding step of holding an evaluation workpiece on the holding surface of the chuck table;
a grinding groove forming step of grinding the evaluation workpiece with the grinding wheel while the rotation of the chuck table is stopped, and forming an arc-shaped grinding groove in the evaluation workpiece along a moving path of the grinding wheel passing through a rotation center of the chuck table;
a holding surface shape calculation step of measuring a thickness of a portion of the substrate of the evaluation workpiece remaining at the bottom of the grinding groove at a plurality of positions and calculating a shape of the conical holding surface;
a determining step of determining whether or not the calculated shape of the holding surface is within an allowable range;
A method for inspecting a holding surface comprising: The method for inspecting a holding surface according to claim 1, wherein in the grinding groove forming step, a grinding groove is formed that continues from the peripheral portion of the workpiece to be evaluated that is cut by the grinding wheel, through the center of rotation of the chuck table, and to the peripheral portion of the workpiece to be evaluated that is cut through by the grinding wheel. A holding surface correction step of grinding the holding surface with the grinding wheel while rotating the chuck table, before the evaluation workpiece holding step, is provided;
3. The method for inspecting a holding surface according to claim 1, wherein the grinding groove forming step includes inspecting the shape of the corrected holding surface using the grinding wheel that has been used to grind the holding surface.

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