Diagnostic method

Abstract

To provide a diagnostic method that can diagnose clogging more stably than diagnosing the degree of clogging on the basis of images of bubbles.SOLUTION: There is provided a diagnostic method for diagnosing clogging of multiple suction ports in a holding plate. The diagnostic method comprises: a provision step of providing a measurement substrate having one surface and the other surface located on opposite sides in the thickness direction, the one surface having an area smaller than an area of a suction surface; an acquisition step of placing the measurement substrate on the holding plate so that one or more of the multiple suction ports form a blocked area blocked by the one surface of the measurement substrate, and then sucking, with the suction surface, the measurement substrate while measuring pressure in a suction path to acquire a pressure value; and a diagnostic step of diagnosing whether or not clogging has occurred in the multiple suction ports on the basis of the pressure value and a range of the blocked area on the suction surface or a range of an exposed area excluding the blocked area, of the suction surface.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a diagnostic method for diagnosing clogging of a plurality of suction ports in a holding plate having a suction surface on which the suction ports are connected to a suction source via suction paths and capable of sucking a workpiece on the suction surface. [Background technology]

[0002] Processing devices such as grinding devices and cutting devices are equipped with a chuck table that holds a workpiece such as a semiconductor wafer by suction using negative pressure (see, for example, Patent Document 1). As this chuck table, a porous plate with exposed pores on its upper surface, a support plate with exposed openings on its upper surface, or the like (hereinafter collectively referred to as a holding plate) is used.

[0003] Negative pressure is transmitted from a suction source to the pores and openings (hereinafter collectively referred to as suction ports) exposed on the upper surface of the holding plate, causing each upper surface to function as a holding surface for suction-holding the workpiece. However, machining debris such as grinding chips and cutting chips can block the suction ports and can also clog the flow paths provided inside the holding plate.

[0004] As a result, if the suction force on the holding surface decreases, it may have a negative impact on processing quality, such as causing chips to fly off during processing. Therefore, when a porous plate is used as the chuck table, a method is known in which the pores exposed on the holding surface are checked for clogging before processing the workpiece.

[0005] Specifically, first, an image of the holding surface is taken while water containing air is continuously ejected from the holding surface, and then the degree of clogging is diagnosed based on the presence or absence of bubbles in the image obtained by the image capture (see, for example, Patent Document 2).

[0006] Since water containing air forms bubbles when it is sprayed out from the pores of the holding surface, it is possible to objectively diagnose based on the image whether clogging has not occurred or the degree of clogging is low in the area where bubbles are formed.

[0007] However, the size of the bubbles changes over time and is not stable. Also, because bubbles repeatedly appear and disappear over time, depending on the timing of the image capture, bubbles may not be captured in an image even in an area where no clogging has occurred.

[0008] In addition, because the presence or absence of bubbles is determined by binarizing the obtained image, there is also the problem that the diagnostic results change even if the amount of light illuminating the chuck table changes. Therefore, the method of diagnosing the degree of clogging based on an image of the holding surface on which bubbles have formed is not very stable in its diagnostic results. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-60922 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-114563 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above problems, and aims to provide a diagnostic method that can stably diagnose clogging compared to diagnosing the degree of clogging based on images of bubbles. [Means for solving the problem]

[0011] According to one aspect of the present invention, there is provided a diagnostic method for diagnosing clogging of a plurality of suction ports in a holding plate having a suction surface on which the plurality of suction ports are connected to a suction source via a suction path and capable of sucking a workpiece on the suction surface, the diagnostic method comprising: a preparation step of preparing a measuring substrate having one side and another side located on opposite sides in the thickness direction, the area of ​​the one side being smaller than the area of ​​the suction surface; after the preparation step, placing the measuring substrate on the holding plate so that one or more of the plurality of suction ports form a blocked area blocked on the one side of the measuring substrate, and then sucking the measuring substrate on the suction surface while measuring the pressure of the suction path to acquire a pressure value; and a diagnostic step of diagnosing whether or not clogging has occurred in the plurality of suction ports based on the pressure value and the range of the blocked area on the suction surface or the range of an exposed area of ​​the suction surface excluding the blocked area.

[0012] Preferably, the measurement substrate does not have a through hole that penetrates from one surface to the other surface, and when the measurement substrate is placed on the holding plate in the acquisition process, the outer peripheral edge of the one surface of the measurement substrate is positioned inside the outer peripheral edge of the suction surface, thereby exposing the outer periphery of the suction surface, or the measurement substrate is annular and has a through hole that penetrates from one surface to the other surface, and when the measurement substrate is placed on the holding plate in the acquisition process, the central portion of the suction surface is exposed.

[0013] Preferably, the preparation step includes preparing a plurality of measurement substrates each having one side and another side located on opposite sides in the thickness direction, the area of ​​the one side being smaller than the area of ​​the suction side and the areas of the one side being different from each other; the acquisition step includes placing one measurement substrate on the holding plate for each of the plurality of measurement substrates so that one or more of the plurality of suction ports form a blocked area where one side is blocked; then, the one measurement substrate is sucked by the suction side while the pressure in the suction path is measured sequentially to obtain a plurality of pressure values; and the diagnosis step includes diagnosing whether or not the plurality of suction ports are clogged based on the plurality of pressure values ​​obtained in the acquisition step and the range of the blocked area on the suction side or the exposed area on the suction side for each of the plurality of measurement substrates.

[0014] Also, preferably, in the preparation step, for each of a plurality of substrates each having the same shape and the same surface area, the outer periphery of each of the plurality of substrates is cut and removed with a cutting blade to create a plurality of measurement substrates having different diameters on the surface, or the center of each of the plurality of substrates is cut and removed with a cutting blade to create a plurality of measurement substrates including through holes having different diameters.

[0015] Also, preferably, in the preparation process, for each of a plurality of substrates each having the same shape and the same area of ​​one side, the outer periphery of each of the plurality of substrates is cut with a cutting blade to form an annular step on the outer periphery of each of the plurality of substrates, the step having a depth that does not reach from the one side to the other side, thereby making the area of ​​the one side smaller than the area of ​​the other side. [Effects of the Invention]

[0016] In a diagnostic method according to one aspect of the present invention, a measurement substrate having an area on one side smaller than the area of ​​the suction surface is placed on a holding plate so that one or more of the multiple suction ports on the suction surface are blocked by one side of the measurement substrate to form a blocked area, and then the measurement substrate is sucked by the suction surface while the pressure in the suction path is measured to obtain a pressure value.

[0017] Then, based on the pressure value and the extent of the blocked or exposed area, it is diagnosed whether or not clogging has occurred in the multiple suction ports. The pressure value remains approximately constant over time, and the extent of the blocked or exposed area is predetermined by the shape of one surface of the measurement substrate. Therefore, clogging diagnosis can be performed more reliably than when the degree of clogging is diagnosed based on an image of bubbles. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a flow diagram of a diagnostic method. [Figure 2] FIG. [Figure 3] FIG. 2 is a partial cross-sectional side view of the chuck table. [Figure 4] FIG. 4(A) is a cross-sectional view of a silicon single crystal substrate processed in a preparation step, and FIG. 4(B) is a diagram showing an example of the preparation step. [Figure 5] FIG. 5(A) is a diagram showing an acquisition process using one measurement substrate, and FIG. 5(B) is a diagram showing an acquisition process using another measurement substrate. [Figure 6] 10 is a top view of the chuck table showing the position of the outer periphery of one surface of a plurality of measurement substrates relative to the suction surface. FIG. [Figure 7] FIG. 7(A) is a partial cross-sectional side view showing a measuring substrate according to a first modified example, and FIG. 7(B) is a partial cross-sectional side view showing a measuring substrate according to a second modified example. [Figure 8] FIG. 8(A) is a top view of a measurement substrate according to the third modified example, and FIG. 8(B) is a diagram showing an acquisition process using the measurement substrate according to the third modified example. [Figure 9] Figure 9(A) is a partially cross-sectional side view showing an example of a preparation process in the fourth modified example, Figure 9(B) is a plan view of one measurement substrate in the fourth modified example, Figure 9(C) is a plan view of another measurement substrate in the fourth modified example, Figure 9(D) is a diagram showing an acquisition process using one measurement substrate, and Figure 9(E) is a diagram showing an acquisition process using another measurement substrate. [Figure 10] FIG. 10 is a plan view of a holding plate according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] (First embodiment) An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a flow diagram of a diagnostic method for diagnosing clogging of a plurality of pores (suction ports) 4b (see Fig. 3) on a suction surface 4a of a porous plate (holding plate) 4 of a chuck table 2.

[0020] In this embodiment, the steps are performed in the following order: a preparation step S10 for multiple measurement substrates 11; an acquisition step S20 for sucking each measurement substrate 11 onto the suction surface 4a and sequentially acquiring pressure values ​​in the suction path 8a1 (see Figure 3) connected to multiple pores 4b; and a diagnosis step S30 for diagnosing whether clogging has occurred in the multiple pores 4b.

[0021] First, a grinding apparatus 10 equipped with a chuck table 2 will be described with reference to Fig. 2. Note that, in this embodiment, an example will be described in which the chuck table 2 is equipped in the grinding apparatus 10, but a similar diagnostic method can also be applied to chuck tables 2 in various processing apparatuses such as cutting apparatuses, polishing apparatuses, and laser processing apparatuses.

[0022] Fig. 2 is a perspective view of the grinding apparatus 10. The X-axis direction (width direction), Y-axis direction (depth direction), and Z-axis direction (height direction) shown in Fig. 2 are perpendicular to one another. The grinding apparatus 10 has a base 12. On the front side of the base 12, cassette mounting tables 14a and 14b are arranged along the X-axis direction.

[0023] The cassette 16a on the cassette mounting table 14a and the cassette 16b on the cassette mounting table 14b each accommodate a plurality of workpieces 13. Each workpiece 13 has a front surface 13a and a back surface 13b located on opposite sides in the thickness direction.

[0024] A plurality of devices (not shown) are formed on the front surface 13a, and in order to protect the plurality of devices, a protective tape 15 having approximately the same diameter as the workpiece 13 is attached to the front surface 13a. The back surface 13b, which is the surface to be ground, is exposed.

[0025] A robot arm 18 is provided behind the cassette mounting tables 14a and 14b to transport the workpiece 13. The robot arm 18 takes out the workpiece 13 with the protective tape 15 attached from the cassettes 16a and 16b and transports it to the alignment unit 20.

[0026] The alignment unit 20 has a disk-shaped support table 20a. A plurality of alignment pins 20b are arranged on the outer periphery of the support table 20a, spaced apart from the support table 20a in the radial direction of the support table 20a and at approximately equal intervals along the circumferential direction of the support table 20a.

[0027] When the robot arm 18 transports the workpiece 13 onto the support table 20a so that the back surface 13b of the workpiece 13 is exposed upward, each alignment pin 20b approaches the center of the support table 20a by an equal distance, thereby positioning the workpiece 13 at a predetermined position on the base 12.

[0028] After alignment, the workpiece 13 is loaded by a loading arm unit (loading arm) 22 onto the chuck table 2 arranged in a loading / unloading area A1 on the turntable 24. The turntable 24 can rotate both clockwise and counterclockwise around a rotation axis (not shown) arranged in the radial center of the turntable 24.

[0029] The upper surface of the turntable 24 is divided by partition plates (not shown) or the like into a carry-in / carry-out area A1, a rough grinding area A2, and a finish grinding area A3, each of which is provided with one chuck table 2.

[0030] Here, the chuck table 2 will be described with reference to Fig. 3. Fig. 3 is a partially cross-sectional side view of the chuck table 2. In Fig. 3, the workpiece 13 and the protective tape 15 are indicated by dashed lines, and a portion of the cross section of the suction surface 4a is shown enlarged.

[0031] The chuck table 2 of this embodiment has a disk-shaped frame 2a. A disk-shaped recess 2c having a diameter smaller than the outer diameter of the frame 2a is formed on an upper surface 2b of the frame 2a. The above-mentioned porous plate 4, which is disk-shaped and has approximately the same diameter as the recess 2c, is fixed to the recess 2c with an adhesive or the like.

[0032] The porous plate 4 is made of various types of glass, such as soda glass or borosilicate glass, and is formed of glass particles 4b1 that are substantially transparent to visible light. Each glass particle 4b1 has substantially the same shape and size.

[0033] The porous plate 4 is a continuous porous body in which minute pores 4b are formed in a three-dimensional network, and the pores 4b are continuous from the lower surface 4c disposed within the frame 2a to the suction surface 4a. Note that the material constituting the porous plate 4 is not limited to the glass particles 4b1.

[0034] The porous plate 4 may contain hard ceramic particles used as abrasive grains such as alumina (Al2O3), silica (SiO2), zirconia (ZrO2), silicon carbide (SiC), etc., and three-dimensional mesh-like pores 4b.

[0035] When the porous plate 4 is fixed to the frame 2a, the suction surface 4a of the porous plate 4 is exposed from the frame 2a and is substantially flush with the upper surface 2b of the frame 2a. As shown in an enlarged view in Figure 3, a plurality of pores 4b are exposed on the suction surface 4a.

[0036] Grooves 2d are formed radially on the bottom surface of recess 2c of frame 2a. Grooves 2d intersect with each other at the radial center of frame 2a and connect to through-hole 2e that penetrates frame 2a at the center. Through-hole 2e is connected to suction source 8b, such as a vacuum pump, via suction path 8a1, such as a pipe.

[0037] A solenoid valve (not shown) is provided in the suction path 8a1. When the solenoid valve is closed, the suction path 8a1 is cut off from the suction source 8, but when the solenoid valve is opened, the negative pressure generated by the suction source 8b is transmitted to the porous plate 4.

[0038] The workpiece 13 placed on the suction surface 4a of the porous plate 4 is sucked and held (i.e., can be sucked) on the suction surface 4a via the protective tape 15 due to the negative pressure transmitted to the suction surface 4a. One end of the branch flow path 8a2 is connected to the suction path 8a1.

[0039] The other end of the branch flow path 8a2 is provided with a pressure gauge 8c such as a negative pressure gauge or a differential pressure gauge. The pressure gauge 8c uses the ambient pressure where the chuck table 2 is located (e.g., atmospheric pressure or the indoor pressure of a clean room) as a reference pressure and measures a gauge pressure that is lower than the reference pressure.

[0040] The gauge pressure (i.e., negative pressure) measured by the pressure gauge 8c can be considered to be approximately equal to the negative pressure transmitted to the lower surface 4c of the porous plate 4 (i.e., the negative pressure in the suction path 8a1 when the solenoid valve is in the open state).

[0041] A rotary shaft (not shown) is provided at the center of the bottom surface of the frame 2a in the radial direction of the frame 2a. A hollow portion that forms the suction path 8a1 is provided inside the rotary shaft, and this hollow portion is connected to the suction source 8b via a rotary joint (not shown).

[0042] 2, other components of the grinding device 10 will now be described. A first support pillar 26a is provided near the rough grinding area A2. A Z-axis direction moving unit 28a having a ball screw is provided on the first support pillar 26a.

[0043] The Z-axis direction moving unit 28a moves the rough grinding unit 30a along the Z-axis direction. The rough grinding unit 30a has a spindle 32a and a rough grinding wheel 34a attached to the lower end of the spindle 32a.

[0044] Similarly, a second support pillar 26b is provided near the finish grinding area A3. A Z-axis direction moving unit 28b having a ball screw is provided on the second support pillar 26b. The Z-axis direction moving unit 28b moves the finish grinding unit 30b along the Z-axis direction.

[0045] The finish grinding unit 30b has a spindle 32b and a finish grinding wheel 34b attached to the lower end of the spindle 32b. The workpiece 13, whose back surface 13b has been subjected to rough grinding and finish grinding in sequence, is placed in the carry-in / carry-out area A1.

[0046] The workpiece 13 placed in the loading / unloading area A1 is transported to the spinner cleaning unit 38 by the unloading arm unit (unloading arm) 36. The workpiece 13 cleaned in the spinner cleaning unit 38 is then loaded by the robot arm 18 into one of the cassettes 16a, 16b from which it was taken.

[0047] A cover (not shown) that covers the components of the grinding apparatus 10 is provided on the base 12. A touch panel 40 is provided on the front side of the cover. The touch panel 40 functions as an input device with which an operator inputs instructions to the grinding apparatus 10, and also functions as a display device for displaying a GUI (Graphical User Interface) or the like for inputting instructions.

[0048] The grinding apparatus 10 is provided with a controller 42 that controls the operation of the chuck table 2, robot arm 18, alignment unit 20, carry-in arm unit 22, turntable 24, carry-out arm unit 36, spinner cleaning unit 38, touch panel 40, etc.

[0049] The controller 42 is configured by a computer having a processor, such as a central processing unit (CPU), and a memory. The memory includes a main storage device such as a dynamic random access memory (DRAM), and an auxiliary storage device such as a flash memory.

[0050] The auxiliary storage device stores software including a predetermined program. The functions of the controller 42 are realized by operating the processor in accordance with this software.

[0051] Next, a diagnostic method for diagnosing clogging of the plurality of pores 4b on the suction surface 4a will be described with reference to Figures 4(A) to 6. Figure 4(A) is a cross-sectional view of a silicon single crystal substrate (substrate) 1 processed in the preparation step S10.

[0052] The silicon single crystal substrate 1 is, for example, a disk-shaped substrate having a substantially uniform thickness, and is also called a dummy wafer, a mirror wafer, etc. The silicon single crystal substrate 1 has one circular surface 11a and another circular surface 11b.

[0053] The first surface 11a and the second surface 11b are located on opposite sides in the thickness direction 11c of the silicon single crystal substrate 1. The silicon single crystal substrate 1 has, for example, a diameter of 300 mm and a thickness of 775 μm. A chamfered portion (also referred to as a bevel portion) is formed on the outer periphery of each of the first surface 11a and the second surface 11b.

[0054] 4(A), the chamfered portion is exaggerated, but the ratio of diameter to thickness is sufficiently large in the silicon single crystal substrate 1, and the region where the chamfered portion is formed is an extremely narrow region on the outer periphery. For example, the chamfered portion is formed in a range of less than 1.0 mm from the outer periphery in the radial direction of the silicon single crystal substrate 1 having a diameter of 300 mm.

[0055] In the preparation step S10 of this embodiment, the above-mentioned measurement substrate 11 is manufactured by performing edge trimming using a cutting device 50 (see Figure 4(B)) on each of a plurality of silicon single crystal substrates 1 each having the same shape (i.e., a shape in which the thickness, diameter, chamfered portion, etc. are the same within a range complying with a predetermined standard such as the SEMI standard) and the same area of ​​one surface 11a.

[0056] As shown in Fig. 4(B), the cutting device 50 has a disk-shaped chuck table 52. The chuck table 52 has a disk-shaped frame. A disk-shaped recess (not shown) is provided in the center of the upper surface of the frame. A disk-shaped porous plate having approximately the same diameter as the outer diameter of the recess is placed in this recess.

[0057] The porous plate is fixed to the frame with an adhesive or the like. The upper surface of the porous plate and the upper surface of the frame are substantially flush with each other, forming a holding surface that suction-holds the measurement substrate 11. This holding surface is disposed substantially parallel to a plane defined by the X-axis direction (processing feed direction) and indexing feed direction (Y-axis direction) of the cutting device 50.

[0058] The chuck table 52 is configured to be rotatable around a rotation axis 52a arranged along a Z-axis direction (height direction) perpendicular to the X-axis direction and Y-axis direction of the cutting device 50 by a motor (not shown).

[0059] A cutting unit 54 is disposed above the chuck table 52. The cutting unit 54 has a spindle 56. The longitudinal direction of the spindle 56 is disposed approximately parallel to the Y-axis direction. A cutting blade 58 is attached to the tip of the spindle 56.

[0060] 4(B) is a diagram showing an example of the preparation step S10. In the preparation step S10, first, the measurement substrate 11 is placed on the chuck table 52. At this time, the other surface 11b of the measurement substrate 11 contacts the holding surface of the chuck table 52. After being placed, the measurement substrate 11 is held by suction on the chuck table 52.

[0061] Next, the spindle 56 is rotated relatively quickly (for example, at 30,000 rpm). Then, the lower end of the cutting blade 58 is positioned at a predetermined depth (for example, 300 μm) from the one surface 11a, and the cutting blade 58 is placed on the extension line of one of the tangent lines at the outer periphery of the measurement substrate 11 that is disposed approximately parallel to the X-axis direction.

[0062] Next, the chuck table 52 is fed for processing along the X-axis direction. When the position on the XY plane where the extension of the spindle 56 intersects with the center of rotation of the chuck table 52 is reached, the feeding of the chuck table 52 for processing is stopped.

[0063] Next, the chuck table 52 is rotated relatively slowly (for example, at 5° / s) while the position of the rotation center of the chuck table 52 is fixed. The rotation of the chuck table 52 is continued until the cutting blade 58 completes at least one revolution around the outer periphery of the one surface 11a.

[0064] In this manner, an annular region near one surface 11a of the outer periphery of silicon single crystal substrate 1 is cut and removed (i.e., edge trimming is performed) by cutting blade 58. As a result, an annular step 11d is formed on the outer periphery of silicon single crystal substrate 1.

[0065] The annular step 11d has a predetermined depth 11d1 that does not reach from one surface 11a to the other surface 11b, and a predetermined width 11d2. In this embodiment, a plurality of measurement substrates 11 each having a different predetermined width 11d2 are produced by edge trimming.

[0066] For example, by performing edge trimming on one silicon single crystal substrate 1, an annular step 11d having a predetermined width 11d2 of 1.6 mm (i.e., the radius 11a1 of one surface 11a is 148.4 mm) and a predetermined depth 11d1 of 300 μm is created on the measurement substrate 11 (see #2 in Table 1 below).

[0067] Similarly, by performing edge trimming on another silicon single crystal substrate 1, an annular step 11d having a predetermined width 11d2 of 1.9 mm (i.e., a radius 11a1 of one surface 11a of 148.1 mm) and a predetermined depth 11d1 of 300 μm is created on the measurement substrate 11 (see #3 in Table 1 below).

[0068] Similarly, edge trimming is performed on yet another silicon single crystal substrate 1 to create an annular step 11d on the measurement substrate 11 having a predetermined width 11d2 of 2.2 mm (i.e., a radius 11a1 of one surface 11a of 147.8 mm) and a predetermined depth 11d1 of 300 μm (see #4 in Table 1 below).

[0069] In this way, multiple measurement substrates 11 are created, each having a different diameter of the surface 11a. Of course, the annular step 11d makes the area of ​​the surface 11a smaller than the area of ​​the other surface 11b. As will be described in detail later, by forming the annular step 11d, the area of ​​the surface 11a becomes smaller than the area of ​​the suction surface 4a.

[0070] In the preparation step S10 of this embodiment, the predetermined depth 11d1 of the annular step 11d is set to a constant value smaller than the thickness of the silicon single crystal substrate 1 in each measurement substrate 11, so that each of the multiple measurement substrates 11 has the annular step 11d but does not have a through hole that penetrates from one surface 11a to the other surface 11b.

[0071] In the preparation step S10, a plurality of measurement substrates 11 each having a different width 11d2 of the annular step 11d are prepared (see #2 to #8 in Table 1 below), and a silicon single crystal substrate 1 that does not have an annular step 11d on the outer periphery (i.e., is not edge-trimmed) is also prepared as the measurement substrate 11 (see #1 in Table 1 below).

[0072] [Table 1]

[0073] In the preparation step S10, instead of creating multiple measurement substrates 11 by edge trimming the silicon single crystal substrate 1, multiple measurement substrates 11 (see #2 to #8 in Table 1) that have been pre-processed so that the width 11d2 of the annular step 11d is different from each other, and a measurement substrate 11 that does not have an annular step 11d on the outer periphery (see #1 in Table 1) may be prepared.

[0074] The material of the measurement substrate 11 is not limited to the above-mentioned silicon single crystal. There are no particular limitations on the material of the measurement substrate 11 as long as it is a non-porous material. The material of the measurement substrate 11 may be a semiconductor other than silicon, a resin, a metal, a ceramic, or the like.

[0075] After the preparation step S10, the acquisition step S20 is performed by sequentially using each of the measurement substrates 11 #1 to #8 contained in the cassette 16a (or cassette 16b). In the acquisition step S20, first, the robot arm 18 carries out one measurement substrate 11 from the cassette 16a (or cassette 16b) to the alignment unit 20.

[0076] After the alignment unit 20 aligns the measurement substrate 11, the carry-in arm unit 22 places the measurement substrate 11 on the porous plate 4 of the chuck table 2 arranged in the carry-in / carry-out area A1.

[0077] At this time, as a result of the alignment of the measurement substrate 11 by the alignment unit 20, the radial center of one surface 11a of the measurement substrate 11 and the center 4d of the suction surface 4a of the porous plate 4 can be aligned with extremely high precision.

[0078] The diameter of the measurement substrate 11 is selected according to the diameter of the suction surface 4a. The measurement substrate 11 placed on the chuck table 2 covers a part or the whole of the suction surface 4a of the porous plate 4.

[0079] For example, one surface 11a of the measurement substrate 11 (#1 in Table 1) that does not have the annular step 11d covers the entire suction surface 4a, thereby forming a blocked region 4a2 in which all of the multiple pores 4b in the suction surface 4a are blocked by the one surface 11a of the measurement substrate 11 (see FIG. 5(A)), and no exposed region 4a3 is formed.

[0080] On the other hand, since the outer peripheral edge 11a2 of one surface 11a of each measurement substrate 11 (#2 to #8 in Table 1) having an annular step 11d is located inside the outer peripheral edge 4a1 of the suction surface 4a, an annular exposed area 4a3 is formed in which the outer periphery of the suction surface 4a is exposed (see Figure 5(B)).

[0081] In other words, a blocked area 4a2 in which one or more of the multiple pores 4b in the suction surface 4a are blocked by one surface 11a of the measurement substrate 11 is formed in the center of the suction surface 4a, and a ring-shaped exposed area 4a3, which is the area of ​​the suction surface 4a excluding the blocked area 4a2, is formed in the outer periphery of the suction surface 4a.

[0082] The measurement substrate 11 is placed on the chuck table 2, and then the measurement substrate 11 is sucked by the suction surface 4a, and the pressure in the suction path 8a1 is measured by measuring the pressure in the branch flow path 8a2 with the pressure gauge 8c. This obtains the pressure value of the suction path 8a1. This operation is performed for each measurement substrate 11 on one chuck table 2.

[0083] Fig. 5(A) is a diagram showing the acquisition step S20 using one (i.e., #1) measurement substrate 11, and Fig. 5(B) is a diagram showing the acquisition step S20 using another (i.e., any one of #2 to #8) measurement substrate 11. Fig. 6 is a top view of the chuck table 2 showing the position of the outer circumferential edge 11a2 of one surface 11a of the plurality of measurement substrates 11 relative to the suction surface 4a.

[0084] When using the measurement substrate 11 #1 in Table 1, the suction surface 4a is entirely blocked, so the absolute value of the negative pressure transmitted to the porous plate 4 becomes relatively large (see #1 in Table 2 below). In contrast, when using any of the measurement substrates 11 #2 to #8 in Table 1, the absolute value of the negative pressure becomes relatively small due to leakage (see #2 to #8 in Table 2 below).

[0085] In particular, since the smaller the diameter of one surface 11a, the wider the width of exposed region 4a3, it is generally considered that the smaller the diameter of one surface 11a, the smaller the absolute value of the negative pressure. However, if pores 4b are clogged, the absolute value of the negative pressure does not necessarily decrease as the diameter of one surface 11a decreases.

[0086] Table 2 below shows multiple pressure values ​​obtained by sequentially placing, suctioning, and measuring the pressure in the above-described manner for each of the measurement substrates 11 #1 to #8 in Table 1. For reference, #9 shows the pressure value of the suction path 8a1 when the measurement substrate 11 is not placed on the porous plate 4.

[0087] Table 2 also shows the negative pressure values ​​for the first chuck table 2 and a different second chuck table 2 among the three chuck tables 2 in the grinding apparatus 10. Note that for the second chuck table 2, the negative pressure values ​​when measurement substrates 11 #5 to #8 were used were not obtained due to experimental reasons.

[0088] Of course, the degree of clogging of the porous plate 4 varies depending on the usage time of the chuck table 2, the usage mode (for example, whether it was used for rough grinding or finish grinding), etc. Generally, clogging tends to occur easily on the outer periphery of the porous plate 4, but clogging does not necessarily occur only on the outer periphery of the porous plate 4.

[0089] [Table 2]

[0090] After the acquisition process S20, whether or not clogging has occurred in the multiple pores 4b is diagnosed based on the negative pressure value (pressure value) obtained using each measurement substrate 11 and the range of the blocked area 4a2 or the range of the exposed area 4a3 on the suction surface 4a (diagnosis process S30).

[0091] In this embodiment, clogging is diagnosed based on the negative pressure value and the range of the exposed area 4a3, but since the range of the entire suction surface 4a is equal to the sum of the range of the blocked area 4a2 and the range of the exposed area 4a3, there is no essential difference whether the range of the blocked area 4a2 or the range of the exposed area 4a3 is used.

[0092] The diagnosis step S30 of this embodiment is performed by the controller 42 of the grinding machine 10. In a first example of the diagnosis step S30, the controller 42 compares each negative pressure value with a threshold value (for example, −70 kPa) stored in advance in the auxiliary storage device.

[0093] Specifically, the controller 42 compares the absolute value of each negative pressure value when the width of the exposed area 4a3 is non-zero with the absolute value of a pre-stored threshold value (i.e., 70 kPa), and diagnoses that clogging has occurred in the exposed area 4a3 if the absolute value of the negative pressure value is greater than the absolute value of the threshold value.

[0094] Also, as a second example of the diagnostic process S30, the controller 42 diagnoses that a clog has occurred in the exposed area 4a3 when the absolute value of each negative pressure value when the width of the exposed area 4a3 is non-zero is greater than the absolute value of a threshold value that is individually predetermined for each exposed area 4a3.

[0095] The threshold value according to the exposed region 4a3 can be obtained by, for example, sequentially using the measurement substrates 11 #2 to #8 on an unused porous plate 4 to obtain negative pressure values.

[0096] In either the first or second example, in the example shown in Table 2, the controller 42 determines that #2 to #4 on the first chuck table 2 are abnormal values, and diagnoses that clogging has occurred in an annular region within 0.7 mm from the outer peripheral edge 4a1 in the radial direction 4e of the suction surface 4a (see Figure 6).

[0097] The controller 42 also determines that #2 on the second chuck table 2 is an abnormal value, and diagnoses that clogging has occurred in an annular region 0.1 mm or less from the outer peripheral edge 4a1 in the radial direction 4e of the suction surface 4a. In Table 2, an "x" is placed in parentheses to the right of a negative pressure value that is an abnormal value, and a check mark is placed in parentheses to the right of a negative pressure value that is not an abnormal value.

[0098] When the controller 42 uses pre-stored thresholds, the pressure values ​​#1 and #9 in Table 2 are acquired for reference only. Therefore, in the acquisition step S20, it is sufficient to acquire at least the pressure values ​​#2 to #8.

[0099] Incidentally, as the width of exposed region 4a3 increases, the absolute value of the negative pressure value obtained by pressure gauge 8c usually decreases. Therefore, as a third example of the diagnosis step S30, controller 42 may diagnose that exposed region 4a3 is clogged when the decrease in the absolute value of the negative pressure value associated with an increase in the width of exposed region 4a3 is too small.

[0100] Furthermore, when the range of the exposed region 4a3 becomes larger than a certain extent (for example, when it becomes larger than 1.0 mm from the outer peripheral edge 4a1), the negative pressure value gradually approaches a constant value (for example, a predetermined value from -40 kPa to -30 kPa), and the decrease in the absolute value of the negative pressure value tends to become smaller.

[0101] Therefore, the diagnosis of clogging based on the decrease in the absolute value of the negative pressure value as the width of the exposed region 4a3 increases is effective only when the range of the exposed region 4a3 is less than 1.0 mm from the outer circumferential edge 4a1, for example.

[0102] Even when the judgment method of the third example is adopted, in the example shown in Table 2, the controller 42 judges that the negative pressure values ​​of #2 to #4 on the first chuck table 2 are abnormal values, and judges that the negative pressure value of #2 on the second chuck table 2 is abnormal values.

[0103] As in the first to third examples, the controller 42 performs the diagnosis step S30, and thus the acquisition step S20 and the diagnosis step S30 are completed within the grinding device 10, which is convenient for the user.

[0104] However, the clogging diagnosis does not necessarily have to be performed by the controller 42. The pressure value and the range of the blocked area 4a2 or the exposed area 4a3 may be transferred to a PC (Personal Computer) or the like, and the clogging diagnosis may be performed by the PC.

[0105] In this embodiment, whether or not clogging has occurred in the multiple pores 4b is diagnosed based on the pressure value obtained by the pressure gauge 8c and the extent of the closed region 4a2 or the exposed region 4a3. The pressure value remains approximately constant over time, fluctuating only by about ±1 kPa.

[0106] Furthermore, the extent of the closed region 4a2 or the exposed region 4a3 is predetermined by the shape of one surface 11a of the measurement substrate 11. Therefore, clogging can be diagnosed more stably than when the degree of clogging is diagnosed based on an image of bubbles.

[0107] In addition, since it is possible to identify which annular region is clogged, it is possible to take measures to thoroughly clean the clogged region compared to the non-clogged region, which is much more efficient than cleaning the entire suction surface 4a for a sufficient amount of time, and also has the advantage of reducing the consumption of cleaning water, etc.

[0108] Furthermore, when a processing abnormality such as a grinding abnormality occurs, by examining the correspondence between the area of ​​the workpiece 13 where the processing abnormality occurred and the area of ​​the porous plate 4 that was sucking the workpiece 13 and was diagnosed as having clogging, it is possible to estimate whether or not the processing abnormality was caused by insufficient suction force due to clogging.

[0109] In the above-described embodiment, the chuck table 2 in a so-called fully automatic grinding machine 10 in which transportation, grinding, cleaning, etc. are performed automatically has been described. However, a similar diagnostic method can also be applied to a chuck table 2 in a so-called manual grinding machine (not shown) in which transportation, etc. other than grinding, is performed by an operator.

[0110] The manual grinding machine has a chuck table similar to chuck table 2, but does not have alignment unit 20 or carry-in arm unit 22. By using a plurality of measuring substrates 11 each having the same size (i.e., diameter) of the other surface 11b due to the annular step 11d, there is an advantage that when each measuring substrate 11 is sequentially placed on the chuck table of the manual grinding machine, it is easy to accurately place the radial center of one surface 11a of each measuring substrate 11 at the center of the suction surface of the chuck table.

[0111] (First Modification) Next, a first modification will be described with reference to Fig. 7(A). Fig. 7(A) is a partial cross-sectional side view showing a measuring substrate 11 according to the first modification. The measuring substrate 11 of the first modification has a truncated cone side surface 11e instead of the annular step 11d.

[0112] The diameter of the truncated cone side surface 11e is smallest at the one surface 11a and gradually increases toward the other surface 11b. Since the measurement substrate 11 has the truncated cone side surface 11e, the area of ​​the one surface 11a is smaller than the area of ​​the other surface 11b.

[0113] The height of the truncated cone having the truncated cone side surface 11e corresponds to the above-mentioned predetermined depth 11d1, and the difference between the radius of one surface 11a of the truncated cone side surface 11e and the radius of the outer circumferential circle that defines the maximum diameter of the measurement substrate 11 corresponds to the above-mentioned predetermined width 11d2.

[0114] Furthermore, when the measurement substrate 11 is placed on the suction surface 4a, the area of ​​the surface 11a is smaller than the area of ​​the suction surface 4a, so that the outer periphery 11a2 of the surface 11a is located inside the outer periphery 4a1 of the suction surface 4a.

[0115] The truncated cone side surface 11e can be formed, for example, by cutting the outer periphery of one surface 11a of the measuring substrate 11 while rotating the chuck table 52 with the cutting blade 58 tilted relative to the rotation axis 52a.

[0116] Alternatively, the truncated cone side surface 11e may be formed by irradiating the outer periphery of one surface 11a of the measurement substrate 11 with a laser beam (not shown) having a wavelength that is absorbed by the measurement substrate 11, and then ablation processing the outer periphery of one surface 11a of the measurement substrate 11 while rotating the chuck table 52.

[0117] (Second Modification) Next, a second modification will be described with reference to Fig. 7(B). Fig. 7(B) is a partial cross-sectional side view showing the measuring substrate 11 according to the second modification. The measuring substrate 11 of the second modification does not have the annular step 11d or the truncated cone side surface 11e, but has a cylindrical side surface on the outer periphery.

[0118] Therefore, the area of ​​one surface 11a and the area of ​​the other surface 11b are the same. Such a measuring substrate 11 can be formed by aligning the lower end of the cutting blade 58 at the same height as the other surface 11b when edge trimming is performed on the measuring substrate 11 (see FIG. 4(B)).

[0119] In this way, by reducing the diameter of the measurement substrate 11, the area of ​​the one surface 11a is made smaller than the area of ​​the suction surface 4a. Therefore, when the measurement substrate 11 is placed on the suction surface 4a, the outer peripheral edge 11a2 of the one surface 11a is located inside the outer peripheral edge 4a1 of the suction surface 4a.

[0120] (Third Modification) Next, a third modification will be described with reference to Fig. 8(A) and Fig. 8(B). Fig. 8(A) is a top view of the measuring substrate 11 according to the third modification. The measuring substrate 11 and the chuck table 2 according to the third modification are not disk-shaped but rectangular plate-shaped. This is what makes them different from the above-described embodiment and modifications.

[0121] The measurement substrate 11 of the third modified example has a rectangular annular step 11d having a predetermined depth 11d1 and a predetermined width 11d2. The annular step 11d can also be formed by edge trimming. Due to the annular step 11d, the area of ​​the surface 11a of the measurement substrate 11 of the third modified example is smaller than the area of ​​the suction surface 4a.

[0122] For example, one surface 11a has a horizontal width 11a3 and a vertical width 11a4, whereas the suction surface 4a has a horizontal width greater than the horizontal width 11a3 and a vertical width greater than the vertical width 11a4. Fig. 8(B) is a diagram showing an acquisition step S20 using a measurement substrate 11 according to a third modified example.

[0123] In the first to third modified examples, a plurality of measurement substrates 11 having different surface areas 11a are sequentially used to measure the pressure in the suction path 8a1 to obtain a plurality of pressure values ​​(acquisition step S20). Then, based on the plurality of pressure values ​​and the extent of the blocked region 4a2 or the exposed region 4a3, it is diagnosed whether or not clogging has occurred in the porous plate 4 (diagnosis step S30).

[0124] Therefore, in the first to third modified examples, similar to the above-described embodiment, clogging diagnosis can be performed more stably than when the degree of clogging is diagnosed based on images of bubbles.

[0125] (Fourth Modification) Next, a fourth modification will be described with reference to Fig. 9(A) to Fig. 9(D). Fig. 9(A) is a partially cross-sectional side view showing an example of the preparation step S10 in the fourth modification.

[0126] In the preparation step S10 of the fourth modified example, the central portions of a plurality of silicon single crystal substrates 1 each having the same shape and the same area of ​​one side 11a are cut and removed with a cutting blade 60 to form through holes 11f (see Figures 9(B) and 9(C)) having different diameters 11f1, 11f2 (wherein diameter 11f2 is smaller than diameter 11f1).

[0127] This creates a plurality of measurement substrates 11 having different diameters 11f1, 11f2. Fig. 9(B) is a plan view of one measurement substrate 11 in the fourth modified example, and Fig. 9(C) is a plan view of another measurement substrate 11 in the fourth modified example.

[0128] In order to cut the center of the silicon single crystal substrate 1, a disk-shaped chuck table 52 capable of sucking up almost the entire surface 11a or 11b of the silicon single crystal substrate 1 except for the chamfered portion is used.

[0129] As shown in Figures 9(D) and 9(E), each through-hole 11f penetrates from one surface 11a to the other surface 11b, so that each measurement substrate 11 has a ring shape. Figure 9(D) is a diagram showing the acquisition step S20 using one measurement substrate 11, and Figure 9(E) is a diagram showing the acquisition step S20 using another measurement substrate 11.

[0130] 9(D) and 9(E), when the measurement substrate 11 is placed on the porous plate 4 in the acquisition step S20, the center of the suction surface 4a is exposed. In the fourth modified example, whether clogging has occurred mainly in the center of the suction surface 4a is diagnosed depending on the extent of the blocked area 4a2 or the exposed area 4a3.

[0131] Of course, the shape of the measurement substrate 11 is not limited to a disk shape, and it may be a rectangular plate shape as in the third modified example. That is, a rectangular plate-shaped measurement substrate 11 may be used to diagnose whether clogging has occurred in the center of the rectangular suction surface 4a.

[0132] Second Embodiment Next, a second embodiment will be described with reference to Fig. 10. The chuck table of the second embodiment has a support plate (holding plate) 44 made of a metal such as stainless steel. The suction surface 44a of the support plate 44 is substantially flat, but the suction surface 44a has a plurality of openings (suction ports) 44b regularly arranged thereon.

[0133] 10 is a plan view of a support plate 44 according to a second embodiment, in which a plurality of openings 44b are provided on a suction surface 44a. Each opening 44b is sufficiently larger than the pores 4b, and has a diameter of, for example, about 1 mm to 3 mm in plan view. The openings 44b are arranged at approximately equal intervals along the circumferential direction of the suction surface 44a and at approximately equal intervals along the radial direction of the suction surface 44a.

[0134] The support plate 44 can also be used as a chuck table that suction-holds the workpiece 13 by negative pressure. Of course, the shape of the chuck table is not limited to a disk shape, but may also be a rectangular plate shape. Furthermore, the arrangement, number, shape, and size of the openings 44b are not particularly limited.

[0135] The clogging of the plurality of openings 44b in the suction surface 44a can also be diagnosed by the preparation step S10, the acquisition step S20, and the diagnosis step S30. In addition, the structures, methods, etc. according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention. [Explanation of symbols]

[0136] 1: Silicon single crystal substrate (substrate) 2: Chuck table 2a: Frame, 2b: Top surface, 2c: Recess, 2d: Groove, 2e: Through hole 4: Porous plate (retention plate) 4a: suction surface, 4a1: outer periphery, 4a2: closed area, 4a3: exposed area 4b: Pore (suction port), 4c: Bottom surface, 4d: Center, 4e: Radial direction 8a1: suction path, 8a2: branch flow path, 8b: suction source, 8c: pressure gauge 10: Grinding device, 12: Base 11: Measurement board 11a: one side, 11a1: radius, 11a2: outer edge, 11a3: width, 11a4: length 11b: other surface, 11c: thickness direction 11d: Annular step, 11d1: Depth, 11d2: Width 11e: Side of a truncated cone 11f: Through hole, 11f1, 11f2: Diameter 13: Workpiece, 13a: Front surface, 13b: Back surface, 15: Protective tape 14a, 14b: cassette mounting table 16a, 16b: Cassette 18:Robot arm 20: Alignment unit, 20a: Support table, 20b: Alignment pin 22: Loading arm unit 24: Turntable 26a: 1st support pillar, 26b: 2nd support pillar 28a, 28b: Z-axis direction moving unit 30a: Rough grinding unit, 30b: Finish grinding unit 32a, 32b: Spindle 34a: Rough grinding wheel, 34b: Finish grinding wheel 36: Unloading arm unit 38: Spinner cleaning unit 40: Touch panel 42: Controller 44: Support plate (retention plate), 44a: Suction surface, 44b: Opening (suction port) 50: Cutting equipment 52: chuck table, 52a: rotation axis 54: Cutting unit, 56: Spindle, 58, 60: Cutting blade A1: Loading / unloading area, A2: Rough grinding area, A3: Finish grinding area S10: Preparation step, S20: Acquisition step, S30: Diagnosis step

Claims

1. A diagnostic method for diagnosing clogging of a holding plate having a plurality of suction ports on a suction surface connected to a suction source via suction paths and capable of sucking a workpiece on the suction surface, comprising: a preparation step of preparing a measurement substrate having one surface and another surface positioned on opposite sides in a thickness direction, the one surface having an area smaller than an area of ​​the suction surface; an acquisition step of, after the preparation step, placing the measurement substrate on the holding plate so that one or more of the plurality of suction ports form a blocked region blocked by the one surface of the measurement substrate, and then sucking the measurement substrate with the suction surface while measuring the pressure of the suction path to acquire a pressure value; and a diagnostic process for diagnosing whether or not clogging has occurred in the plurality of suction ports based on the pressure value and the range of the blocked area on the suction surface or the range of the exposed area on the suction surface excluding the blocked area.

2. The measurement substrate does not have a through-hole penetrating from the one surface to the other surface, and when the measurement substrate is placed on the holding plate in the obtaining step, the outer periphery of the one surface of the measurement substrate is positioned inside the outer periphery of the suction surface, thereby exposing the outer periphery of the suction surface, or The diagnostic method described in claim 1, characterized in that the measurement substrate is annular with a through hole extending from one surface to the other surface, and when the measurement substrate is placed on the holding plate in the acquisition process, the center of the suction surface is exposed.

3. In the preparation step, a plurality of measurement substrates are prepared, each having the one surface and the other surface located on opposite sides in the thickness direction, the area of ​​the one surface being smaller than the area of ​​the suction surface, and the areas of the one surfaces being different from each other; In the acquisition step, for each of the plurality of measurement substrates, one measurement substrate is placed on the holding plate so that one or more of the plurality of suction ports are closed on one surface to form a closed region, and then the one measurement substrate is sucked on the suction surface while the pressure in the suction path is measured, thereby acquiring a plurality of pressure values; The diagnostic method described in claim 1 or 2, characterized in that in the diagnostic process, whether or not clogging has occurred in the multiple suction ports is diagnosed based on the multiple pressure values ​​obtained in the acquisition process and the range of the blocked area on the suction surface or the exposed area on the suction surface for each of the multiple measurement substrates.

4. In the preparation step, for each of a plurality of substrates each having the same shape and the same surface area, The diagnostic method described in claim 3, characterized in that the plurality of measurement substrates each having a different diameter on one side are created by cutting and removing the outer periphery of each of the plurality of substrates with a cutting blade, or the plurality of measurement substrates each including through holes having different diameters are created by cutting and removing the central portion of each of the plurality of substrates with a cutting blade.

5. In the preparation step, for each of a plurality of substrates each having the same shape and the same surface area, The diagnostic method described in claim 3, characterized in that the outer periphery of each of the plurality of substrates is cut with a cutting blade to form an annular step on the outer periphery of each of the plurality of substrates, the step having a depth that does not reach from the one surface to the other surface, thereby making the area of ​​the one surface smaller than the area of ​​the other surface.

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