Grinder

Abstract

To provide a grinder which enables automatic regulation of a positional relationship between a spindle and a chuck table, and to provide a wafer grinding method.SOLUTION: A grinder 1 includes a chuck table 10, grinding units 20 each having a grinding wheel 24 including grind stone parts 26, which are disposed in an annular shape having a diameter smaller than or equal to a radius of a wafer 100, at a tip; grinding movement mechanisms 30 each of which relatively moves the grinding unit 20 and the chuck table 10 in a rotation axis direction; diameter regulation mechanisms 40 each of which relatively moves the grinding unit 20 and the chuck unit 10 in a direction orthogonal to a rotation axis; non-contact thickness measurement units 60 each of which measures a thickness distribution of the wafer 100; a target diameter storage part 91 which stores a target diameter of a circular recessed part formed in the wafer 100; a diameter calculation part 92 which calculates a diameter of the circular recessed part based on the measured thickness distribution; and a command part 94 which commands the diameter regulation mechanism 40 to make correction based on a difference between the target diameter and the calculated diameter.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a grinding device. [Background technology]

[0002] For example, with the spread of SiP (System in Package) etc., there is a demand for grinding techniques that can thin wafers with good yield. The TAIKO (registered trademark) grinding method is known as one of the grinding techniques for thinning wafers.

[0003] The TAIKO grinding method is a technique for grinding the back surface of a wafer having a device area on its surface on which multiple devices are formed, in which the outer peripheral edge portion of the back surface of the wafer is left intact, and only the inner portion of the back surface of the wafer that corresponds to the device area inside the outer peripheral edge portion is ground to thin the wafer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-19461 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the TAIKO grinding method, only the devices formed on the surface side of the formed circular recess are used as effective chips. However, for example, if the circular recess becomes smaller than the target diameter, the number of effective chips will decrease, so it is desirable that the diameter of the circular recess be formed as intended.

[0006] In the grinding equipment that performs TAIKO grinding, the diameter of the circular recess is determined by the positional relationship between the spindle and the chuck table, and the diameter of the grinding wheel used for grinding. Therefore, it is necessary to adjust (set) the positional relationship between the spindle and the chuck table when starting up the equipment (installation), and to adjust (set) it when replacing the grinding wheel, which is a consumable item. Each adjustment causes an increase in man-hours, which leads to a decrease in productivity, which is an issue.

[0007] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a grinding apparatus that can automatically adjust the positional relationship between the spindle and the chuck table. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, the grinding apparatus of the present invention is a grinding apparatus that grinds a surface of a wafer to form a circular recess and a ring-shaped reinforcing portion surrounding the circular recess on the surface of the wafer, and includes a chuck table that holds the wafer, a grinding unit having a grinding wheel at the tip of a spindle, the grinding wheel including a grinding stone portion arranged in a ring shape with a diameter equal to or less than the radius of the wafer and a wheel base that supports the grinding stone portion, a grinding movement mechanism that moves the grinding unit and the chuck table relatively in the direction of the rotation axis of the spindle, and a grinding mechanism that moves the grinding unit and the chuck table in a direction perpendicular to the rotation axis of the spindle, a non-contact thickness measurement unit that measures a thickness distribution of the wafer, and a control unit, wherein the control unit includes a target diameter memory unit that stores a target diameter of a circular recess formed on the wafer, a diameter calculation unit that calculates the diameter of the circular recess formed on the wafer based on the thickness distribution measured by the non-contact thickness measurement unit, and a command unit that commands the diameter adjustment mechanism to make a correction based on the difference between the target diameter stored in the target diameter memory unit and the diameter calculated by the diameter calculation unit.

[0009] In the grinding apparatus of the present invention, the non-contact thickness measuring unit may measure the thickness distribution of the wafer held on the chuck table.

[0010] In addition, in the grinding apparatus of the present invention, the non-contact thickness measuring unit may rotate the chuck table on which the wafer is held and measure three or more boundary positions between the circular recess and the ring-shaped reinforcement portion, and the diameter calculation unit may calculate the diameter of the circular recess based on the boundary positions measured by the non-contact thickness measuring unit. Effect of the Invention

[0011] The present invention can automatically adjust the positional relationship between the spindle and the chuck table. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a grinding device according to an embodiment. [Diagram 2] FIG. 2 is a plan view showing a schematic configuration of the grinding apparatus shown in FIG. [Diagram 3] FIG. 3 is a side view, partly in section, showing one state of grinding by the grinding device. [Figure 4] FIG. 4 is a perspective view showing one state of wafer thickness distribution measurement by the grinding device. [Diagram 5] FIG. 5 is a plan view of a wafer for explaining an example of a method for calculating the diameter of a circular recess. [Figure 6] FIG. 6 is a side view, partly in section, showing one state of grinding processing by the grinding device after correction. [Figure 7] FIG. 7 is a plan view of a wafer for explaining another example of a method for calculating the diameter of a circular recess. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, 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 appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0014] In the embodiment described below, an XYZ Cartesian coordinate system is set, and the positional relationship of each part is described with reference to this XYZ Cartesian coordinate system. One direction in a horizontal plane is the X-axis direction, a direction perpendicular to the X-axis direction in the horizontal plane is the Y-axis direction, and a direction perpendicular to both the X-axis direction and the Y-axis direction is the Z-axis direction. The XY plane including the X-axis and Y-axis is parallel to the horizontal plane. The Z-axis direction perpendicular to the XY plane is the vertical direction.

[0015] [Embodiment] A grinding apparatus 1 and a method for grinding a wafer 100 according to an embodiment of the present invention will be described with reference to the drawings. First, the configuration of the grinding apparatus 1 according to the embodiment will be described. FIG. 1 is a perspective view showing an example of the configuration of the grinding apparatus 1 according to the embodiment. FIG. 2 is a plan view showing a schematic configuration of the grinding apparatus 1 shown in FIG. 1. As shown in FIGS. 1 and 2, the grinding apparatus 1 according to the embodiment includes a chuck table 10, a contact-type thickness measuring unit 16, a non-contact thickness measuring unit 60, a grinding unit 20, a grinding movement mechanism 30, a diameter adjustment mechanism 40, a cleaning unit 50, a cassette mounting table 71, an alignment unit 72, a transport unit 80, and a control unit 90.

[0016] The grinding apparatus 1 is an apparatus that grinds a wafer 100 held on a chuck table 10. More specifically, the grinding apparatus 1 forms a circular recess 102 and a ring-shaped reinforcing portion 104 surrounding the circular recess 102 on a surface 101 of the wafer 100 (see FIG. 6). The wafer 100 is a wafer such as a disk-shaped semiconductor wafer or an optical device wafer, which has a substrate made of, for example, silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), lithium tantalate (LiTaO3), or the like, and has a plurality of circuit elements such as ICs (Integrated Circuits) and LSIs (Large Scale Integrations) formed on its surface.

[0017] The chuck table 10 is disk-shaped and made of, for example, porous ceramics, and holds the wafer 100 on a horizontal, flat holding surface 11. The holding surface 11 is connected to a vacuum suction source via, for example, a vacuum suction path, and holds by suction the placed wafer 100. During grinding, the chuck table 10 is rotated within a horizontal plane around a vertical axis by a rotation drive mechanism (not shown).

[0018] In this embodiment, three chuck tables 10 are provided on the turntable 12 at equal intervals at a phase angle of 120 degrees. The turntable 12 is a disk-shaped table, and is provided on the upper surface of the device base 2 so as to be rotatable about a vertical axis within a horizontal plane relative to the device base 2. The turntable 12 is rotated at a predetermined timing, so that the chuck table 10 moves sequentially to a carry-in / out area 13, a rough grinding area 14, and a finish grinding area 15.

[0019] The carry-in / out area 13 is an area where the wafer 100 is carried in and out by a carry-in unit 82 and an unloading unit 83 described later. The rough grinding area 14 is an area where the wafer 100 is processed by a rough grinding unit 20-1 described later. The finish grinding area 15 is an area where the wafer 100 is processed by a finish grinding unit 20-2 described later.

[0020] The contact type thickness measuring units 16 are provided at two locations, namely, in the vicinity of the rough grinding region 14 and in the vicinity of the finish grinding region 15. In FIG. 1, the contact type thickness measuring unit 16 in the finish grinding region 15 is omitted. The two contact type thickness measuring units 16 have the same configuration and the same function, except for the location where they are provided. The contact type thickness measuring unit 16 includes a first contactor 17, a second contactor 18, and a thickness calculating unit (not shown) that calculates the distance in the Z-axis direction between the tips of the pair of contactors (the first contactor 17 and the second contactor 18). In the embodiment, the first contactor 17 and the second contactor 18 are both contact type probes that measure the height of the contact position. The thickness calculating unit may be configured as a part of the function of a control unit 90 described later.

[0021] The first contactor 17 measures the position of the holding surface 11 in the Z-axis direction, i.e., the height of the holding surface 11, by bringing its tip into contact with the holding surface 11 of the chuck table 10. The second contactor 18 measures the position of the upper surface of the wafer 100 in the Z-axis direction (upper surface position), i.e., the height of the upper surface of the wafer 100 (upper surface height), by bringing its tip into contact with the upper surface of the wafer 100 held on the chuck table 10. The contact type thickness measuring unit 16 measures the thickness of the wafer 100 held on the holding surface 11 of the chuck table 10 by the thickness calculation section calculating the distance in the Z-axis direction between the tips of the pair of contactors (first contactor 17 and second contactor 18).

[0022] The non-contact thickness measurement units 60 are provided at two locations, one near the rough grinding region 14 and the other near the finish grinding region 15. Note that in FIG. 1, the non-contact thickness measurement unit 60 in the rough grinding region 14 is omitted. The two non-contact thickness measurement units 60 have the same configuration and the same function, except for the location where they are provided. The non-contact thickness measurement unit 60 measures the thickness of the wafer 100 without contacting the upper surface of the wafer 100 held on the holding surface 11 of the chuck table 10. The non-contact thickness measurement unit 60 includes a swing arm 61 and a measurement head 62.

[0023] The swing arm 61 is supported at its base end so as to be swingable by a motor (not shown). The measuring head 62 is provided at the tip of the swing arm 61. The non-contact thickness measuring unit 60 is swung about its base end between a measuring position where the measuring head 62 faces the upper surface of the wafer 100 held on the holding surface 11 of the chuck table 10 in the Z-axis direction and a retracted position where the measuring head 62 retracts from the upper surface of the wafer 100 held on the holding surface 11 of the chuck table 10. The non-contact thickness measuring unit 60 measures the thickness of the wafer 100 while the measuring head 62 traverses the area facing the upper surface of the wafer 100, thereby measuring the thickness distribution of the wafer 100 in the area through which the measuring head 62 has passed. The non-contact thickness measurement unit 60, for example, rotates the chuck table 10 on which the wafer 100 is held, measures the thickness distribution including three or more boundary positions 107 (see FIG. 3) between the circular recess 103 (see FIG. 3) and the ring-shaped reinforcement portion 104 (see FIG. 3) of the wafer 100, and outputs the measurement results to the control unit 90.

[0024] The grinding unit 20 is a unit that grinds the wafer 100 held on the chuck table 10. In the embodiment, the grinding unit 20 includes a rough grinding unit 20-1 that roughly grinds the wafer 100, and a finish grinding unit 20-2 that finish grinds the wafer 100.

[0025] The rough grinding unit 20-1 grinds the wafer 100 held on the holding surface 11 of the chuck table 10 located in the lower rough grinding region 14. The rough grinding unit 20-1 has a spindle housing 21, a spindle 22 supported by the spindle housing 21 and rotating about a vertical axis, a motor 23 that rotates the spindle 22, and a grinding wheel 24 attached to the lower end of the spindle 22. The grinding wheel 24 rotates together with the spindle 22 about the vertical axis.

[0026] The grinding wheel 24 includes a wheel base 25 and a grindstone portion 26 supported on the lower surface side of the wheel base 25. For example, a plurality of grindstone portions 26 are arranged in a ring shape in a ring-shaped groove formed on the lower surface of the wheel base 25 so that one end side is embedded and the other end side protrudes, and are fixed by adhesive. At this time, the grindstone portions 26 are arranged in a ring shape whose diameter is equal to or smaller than the radius of the wafer 100. The rough grinding unit 20-1 can be moved in the direction of the rotation axis of the spindle 22 by a grinding movement mechanism 30-1 described later. The rough grinding unit 20-1 can be moved in the radial direction of the chuck table 10 located in the rough grinding region 14 by a diameter adjustment mechanism 40-1 described later.

[0027] The finish grinding unit 20-2 grinds the wafer 100 held on the holding surface 11 of the chuck table 10 located in the finish grinding area 15 below. The finish grinding unit 20-2 has the same basic configuration as the rough grinding unit 20-1, so a description thereof will be omitted. The finish grinding unit 20-2 can be moved in the direction of the rotation axis of the spindle 22 by a grinding movement mechanism 30-2 described later. The finish grinding unit 20-2 can be moved in the radial direction of the chuck table 10 located in the finish grinding area 15 by a diameter adjustment mechanism 40-2 described later.

[0028] The grinding movement mechanism 30 is a mechanism for relatively moving the grinding unit 20 and the chuck table 10 in the direction of the rotation axis of the spindle 22. In the embodiment, the grinding movement mechanism 30 includes a grinding movement mechanism 30-1 corresponding to the rough grinding unit 20-1 and a grinding movement mechanism 30-2 corresponding to the finish grinding unit 20-2. The grinding movement mechanism 30-1 moves the rough grinding unit 20-1 away from and toward the chuck table 10 located in the rough grinding region 14 in the Z-axis direction. The grinding movement mechanism 30-2 moves the finish grinding unit 20-2 away from and toward the chuck table 10 located in the finish grinding region 15 in the Z-axis direction.

[0029] Each grinding movement mechanism 30 is provided on a columnar portion 3 erected from an apparatus base 2 of the grinding apparatus 1. Each grinding movement mechanism 30 is realized by a ball screw mechanism having, for example, a known guide rail that supports the spindle housing 21 of the grinding unit 20 so as to be freely movable in the vertical direction, a known ball screw that is provided so as to be freely rotatable about a vertical axis, and a known motor that rotates the ball screw about the axis.

[0030] The diameter adjustment mechanism 40 is a mechanism for relatively moving the grinding unit 20 and the chuck table 10 in a direction perpendicular to the rotation axis of the spindle 22. In the embodiment, the diameter adjustment mechanism 40 includes a diameter adjustment mechanism 40-1 corresponding to the rough grinding unit 20-1 and a diameter adjustment mechanism 40-2 corresponding to the finish grinding unit 20-2. The diameter adjustment mechanism 40-1 moves the rough grinding unit 20-1 forward and backward in the radial direction of the chuck table 10 located in the rough grinding region 14. The diameter adjustment mechanism 40-2 moves the finish grinding unit 20-2 forward and backward in the radial direction of the chuck table 10 located in the finish grinding region 15.

[0031] The cleaning unit 50 is a unit that cleans the wafer 100 processed by the grinding unit 20. The cleaning unit 50 has a cleaning table 51 that holds the wafer 100 on a holding surface 52, and a cleaning nozzle (not shown) that drips a cleaning liquid supplied from a cleaning liquid supply source (not shown) onto the wafer 100 held on the cleaning table 51. The cleaning table 51 rotates around a vertical axis. The cleaning nozzle is movable from a position facing the wafer 100 held on the cleaning table 51 to a retracted position.

[0032] The cassette 70 is a container having a plurality of slots for accommodating one wafer 100 in a horizontal position in each slot. The cassette 70 includes a cassette 70-1 for accommodating unprocessed wafers 100 and a cassette 70-2 for accommodating processed and cleaned wafers 100. The cassette mounting stage 71 supports the pair of cassettes 70-1, 70-2 on which they are placed and which allows each of the cassettes 70-1, 70-2 to be raised and lowered in the vertical direction.

[0033] The alignment unit 72 is a table on which the wafer 100 taken out of the cassette 70-1 and transported by the carry-in / out unit 81 of the transport unit 80 is temporarily placed and used for aligning the center of the wafer 100.

[0034] The transport unit 80 is a unit that transports the wafer 100 by an arm that is rotated in a horizontal plane. The transport unit 80 includes a carry-in / out unit 81, a carry-in unit 82, and a carry-out unit 83. The carry-in / out unit 81 takes out the wafers 100 stored in the cassette 70-1 one by one and transports them to the alignment unit 72. The carry-in unit 82 transports the wafer 100 before rough grinding, which has been aligned by the alignment unit 72, onto the holding surface 11 of the chuck table 10 in the carry-in / out area 13 of the turntable 12. The carry-out unit 83 transports the wafer 100 after finish grinding from the chuck table 10 in the carry-in / out area 13 of the turntable 12 onto the holding surface 52 of the cleaning table 51 of the cleaning unit 50. The carry-in / out unit 81 transports the cleaned wafer 100 from the cleaning unit 50 and into the cassette 70-2.

[0035] The control unit 90 controls each of the above-mentioned components of the grinding apparatus 1, causing the grinding apparatus 1 to perform processing operations on the wafer 100. The control unit 90 controls the chuck table 10, the turntable 12, the contact-type thickness measurement unit 16, the non-contact thickness measurement unit 60, the grinding unit 20, the grinding movement mechanism 30, the diameter adjustment mechanism 40, the cleaning unit 50, the cassette mounting table 71, the transport unit 80, and the like.

[0036] The control unit 90 is a computer including a processor as a calculation means, a storage device as a storage means, and an input / output interface device as a communication means. The processor includes, for example, a microprocessor such as a CPU (Central Processing Unit). The storage device has a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The processor performs various calculations based on a predetermined program stored in the storage device. The processor outputs various control signals to the above-mentioned components via the input / output interface device according to the calculation results, and controls the grinding device 1. The control unit 90 includes a target diameter storage unit 91, a diameter calculation unit 92, a difference calculation unit 93, and a command unit 94.

[0037] The target diameter storage unit 91 stores a target diameter 105 (see FIG. 6) of a circular recess 102 (see FIG. 6) to be formed on the front surface 101 of the wafer 100. The target diameter 105 indicates a target value of the diameter of the circular recess 102.

[0038] The diameter calculation unit 92 calculates the diameter 106 (see FIG. 5) of the circular recess 103 based on the thickness distribution of the wafer 100 measured by the non-contact thickness measurement unit 60. The diameter calculation unit 92 calculates the diameter 106 of the circular recess 103 based on the boundary positions 107. In the embodiment, the diameter calculation unit 92 first identifies positions where the thickness changes as boundary positions 107 based on the thickness distribution of the wafer 100. The diameter calculation unit 92 acquires the XY coordinates of the identified three boundary positions 107. The diameter calculation unit 92 calculates a circle passing through the coordinates of the boundary positions 107, that is, the diameter 106 of the circular recess 103. The diameter calculation unit 92 calculates the diameter 106 of the circular recess 103 based on the XY coordinates of the four or more boundary positions 107, for example, by using the least squares method.

[0039] The difference calculation unit 93 calculates the difference between the target diameter 105 stored in the target diameter storage unit 91 and the diameter 106 calculated by the diameter calculation unit 92 .

[0040] The command unit 94 commands the diameter adjustment mechanism 40 to make a correction based on the difference between the target diameter 105 stored in the target diameter storage unit 91 and the diameter 106 calculated by the diameter calculation unit 92. In other words, the command unit 94 commands the diameter adjustment mechanism 40 to relatively move the grinding unit 20 and the chuck table 10 forward and backward in the radial direction by an amount corresponding to the shortage of the diameter 106 of the already formed circular recess 103 relative to the target diameter 105, so that the grinding unit 20 forms a circular recess 102 having the target diameter 105.

[0041] Next, a series of grinding steps performed by the grinding apparatus 1 in the embodiment will be described. Unprocessed wafers 100 are placed on the cassette placement table 71 of the grinding apparatus 1 while being accommodated in a cassette 70-1. The cassette 70-1 is automatically transported, for example, by a transport device in a factory facility in which the grinding apparatus 1 is installed. An empty cassette 70-2 is prepared on the cassette placement table 71 of the grinding apparatus 1. The control unit 90 drives the carry-in / out unit 81 to take out the wafers 100 before grinding accommodated in the cassette 70-1 one by one and transport them to the alignment unit 72. The centers of the wafers 100 transported to and temporarily placed in the alignment unit 72 are aligned.

[0042] The control unit 90 drives the carry-in unit 82 to transport the wafer 100 aligned by the alignment unit 72 onto the holding surface 11 of the chuck table 10 in the carry-in / out area 13 of the turntable 12. The control unit 90 drives a vacuum suction source connected to the holding surface 11 of the chuck table 10 to suction-hold the wafer 100 on the holding surface 11. The control unit 90 rotates the turntable 12 by 120 degrees, and moves the chuck table 10, on which the wafer 100 is held, to the rough grinding area 14, which is a processing area by the rough grinding unit 20-1.

[0043] FIG. 3 is a side view showing one state of grinding by the grinding device 1, partially in cross section. First, the surface 101 of the wafer 100 is ground to form a circular recess 103 having a diameter smaller than a target diameter 105 on the surface 101 of the wafer 100. The control unit 90 shown in FIG. 1 controls the diameter adjustment mechanism 40-1 to position the rough grinding unit 20-1 at a position where the circular recess 103 formed on the surface 101 of the wafer 100 is smaller than the target diameter 105. Next, the control unit 90 rotates the chuck table 10 about a vertical axis and rotates the spindle 22 of the rough grinding unit 20-1 about its axis. The control unit 90 causes the grinding movement mechanism 30-1 to lower the rough grinding unit 20-1 and feed the rough grinding unit 20-1 for processing while supplying a grinding fluid to the surface processed by the rough grinding unit 20-1.

[0044] As a result, the center of the surface 101 of the wafer 100 is roughly ground, and a circular recess 103 having a diameter 106 smaller than a target diameter 105 is formed on the surface 101 of the wafer 100. After grinding to a predetermined thickness, the control unit 90 causes the grinding movement mechanism 30-1 to raise the rough grinding unit 20-1, stops the rotation of the chuck table 10 and the rough grinding unit 20-1, and stops the supply of grinding fluid. The control unit 90 rotates the turntable 12 by 90 degrees, and moves the chuck table 10 holding the wafer 100 to the finish grinding area 15, which is a processing area for the finish grinding unit 20-2, and performs the finish grinding in the same manner as the rough grinding.

[0045] Fig. 4 is a perspective view showing one state of thickness distribution measurement of the wafer 100 by the grinding apparatus 1. Fig. 5 is a plan view of the wafer 100 for explaining one example of a method for calculating the diameter 106 of the circular recess 103. After the circular recess 103 having the diameter 106 smaller than the target diameter 105 is formed on the surface 101 of the wafer 100, the diameter 106 is measured. The control unit 90 first causes the swing arm 61 of the non-contact thickness measuring unit 60 to swing while measuring the thickness of the wafer 100 held on the holding surface 11 of the chuck table 10.

[0046] More specifically, the thickness of the wafer 100 is measured while swinging the swing arm 61 so that the measurement head 62 passes above a region including the circular recess 103, the ring-shaped reinforcement 104, and the boundary position 107 therebetween at any position in the circumferential direction. Next, the chuck table 10 is rotated by a predetermined angle (for example, 120 degrees at a time) to measure the thickness of the wafer 100 in the region including the circular recess 103, the ring-shaped reinforcement 104, and the boundary position 107 therebetween, and the thickness distribution of the wafer 100 including three or more boundary positions 107 is measured. The non-contact thickness measurement unit 60 outputs the measured thickness distribution to the control unit 90.

[0047] Next, the diameter calculation unit 92 of the control unit 90 extracts the boundary position 107 from the thickness distribution of the wafer 100, and acquires the XY coordinates of the boundary position 107. Next, the diameter calculation unit 92 calculates the diameter 106 of the circular recess 103 based on the boundary position 107. Next, the difference calculation unit 93 of the control unit 90 acquires information on the target diameter 105 stored in the target diameter storage unit 91. In addition, the difference calculation unit 93 acquires the diameter 106 of the circular recess 103 calculated by the diameter calculation unit 92. The difference calculation unit 93 calculates the difference between the acquired diameter 106 and the target diameter 105.

[0048] Fig. 6 is a side view, partially in cross section, showing one state of the grinding process after correction by the grinding apparatus 1. After calculating the difference between the diameter 106 of the circular recess 103 and the target diameter 105 of the circular recess 102, the circular recess 102 having the target diameter 105 is formed on the surface 101 of the wafer 100. The control unit 90 shown in Fig. 1 rotates the turntable 12 by 240 degrees, and moves the chuck table 10 holding the wafer 100 to the rough grinding area 14, which is the processing area by the rough grinding unit 20-1.

[0049] A command section 94 of the control unit 90 controls the diameter adjustment mechanism 40-1 based on the difference between the diameter 106 of the circular recess 103 calculated by the difference calculation section 93 and the target diameter 105 of the circular recess 102, to position the rough grinding unit 20-1 at a position where the circular recess 102 to be formed on the front surface 101 of the wafer 100 will be the circular recess 102 with the target diameter 105. In other words, the positional relationship between the spindle 22 of the rough grinding unit 20-1 and the chuck table 10 in the rough grinding region 14 is adjusted.

[0050] The subsequent steps are the same as the procedure for forming the circular recess 103 having a diameter 106 smaller than the target diameter 105, and therefore a description thereof will be omitted. By performing finish grinding in the same manner as the rough grinding, the center of the front surface 101 of the wafer 100 is ground, and a circular recess 102 having a target diameter 105 and a ring-shaped reinforcing portion 104 surrounding the circular recess 102 are formed on the front surface 101 of the wafer 100.

[0051] The control unit 90 rotates the turntable 12 by 120 degrees from a state in which the chuck table 10 holding the wafer 100 on which the circular recess 102 is formed is in the finish grinding area 15, and moves the chuck table 10 holding the wafer 100 to the carry-in / out area 13 of the turntable 12. The control unit 90 stops the vacuum suction source connected to the holding surface 11 of the chuck table 10. The control unit 90 drives the carry-out unit 83 to transport the wafer 100 after the finish grinding from the chuck table 10 in the carry-in / out area 13 of the turntable 12 onto the holding surface 52 of the cleaning table 51 of the cleaning unit 50.

[0052] The control unit 90 drives a vacuum suction source connected to the holding surface 52 of the cleaning table 51, and causes the holding surface 52 to hold the wafer 100 by suction. The control unit 90 rotates the cleaning table 51 around a vertical axis and causes a cleaning nozzle (not shown) to supply a cleaning liquid to the wafer 100 on the cleaning table 51, thereby cleaning the ground surface of the wafer 100. At this time, the control unit 90 moves the discharge port of the cleaning nozzle in the horizontal direction so that the position where the cleaning liquid is supplied by the cleaning nozzle moves on a horizontal plane. After cleaning, the control unit 90 stops the supply of the cleaning liquid and the rotation of the cleaning table 51. The control unit 90 drives the carry-in / out unit 81 to carry out the cleaned wafer 100 from the cleaning unit 50 and store it in a predetermined slot of the cassette 70-2.

[0053] In the above procedure, the diameter 106 is measured in the finish grinding area 15 after the circular recess 103 having the diameter 106 smaller than the target diameter 105 is formed, but the diameter 106 may be measured in the rough grinding area 14 after the wafer 100 is cleaned in the cleaning unit 50. In the above procedure, the wafer 100 in which the circular recess 102 having the target diameter 105 is formed is the same wafer 100 as the wafer 100 in which the circular recess 103 having the diameter 106 smaller than the target diameter 105 is formed, but it may be another wafer 100 newly taken out of the cassette 70-1 and transported. The grinding apparatus 1 may also process a plurality of wafers 100 in parallel. That is, for example, while the wafer 100 is being processed by the grinding unit 20, another wafer 100 may be cleaned by the cleaning unit 50.

[0054] As described above, the grinding apparatus 1 according to the embodiment measures the diameter 106 of the circular recess 103 formed on the front surface 101 of the wafer 100 using the non-contact thickness measuring unit 60, and automatically adjusts the positional relationship between the spindle 22 of the grinding unit 20 and the chuck table 10 based on the difference between the measured diameter 106 and the target diameter 105. This makes it possible to make the diameter of the circular recess 102 formed after the automatic adjustment match the target diameter 105.

[0055] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

[0056] For example, the mounting position of the non-contact thickness measuring unit 60 may be a position where the thickness distribution of the wafer 100 held on the holding surface 51 of the cleaning unit 50 can be measured. In this case, the non-contact thickness measuring unit 60 rotates the cleaning table 51 on which the wafer 100 is held, and measures the thickness distribution including three or more boundary positions 107 between the circular recess 103 and the ring-shaped reinforcing portion 104 of the wafer 100.

[0057] The control unit 90 may further include a center shift amount calculation section that calculates the amount of shift between the center of the wafer 100 and the center of the circular recess 103. In this case, when measuring the thickness distribution of the wafer 100 including the boundary position 107 between the circular recess 103 and the ring-shaped reinforcement portion 104, the non-contact thickness measurement unit 60 also measures the outer periphery position of the wafer 100. The center shift amount calculation section calculates the center coordinates of the circular recess 103 from three or more boundary positions 107, and calculates the center coordinates of the wafer 100 from three or more outer periphery positions, and calculates the amount of center shift from each of the center coordinates.

[0058] Furthermore, the region in which the thickness distribution of the wafer 100 is measured by the non-contact thickness measuring unit 60 is not limited to the embodiment. That is, in the embodiment, the swing arm 61 is swung while the chuck table 10 is stopped, and the thickness distribution of an arc-shaped region is measured, but in the present invention, a linear thickness distribution may be measured.

[0059] 7 is a plan view of the wafer 100 for explaining another example of a method for calculating the diameter 106 of the circular recess 103. By swinging the swing arm 61 while rotating the chuck table 10, the measurement head 62 is moved linearly relative to the wafer 100, and the thickness distribution of a linear region can be measured. In this case, two boundary positions 107 can be extracted. Furthermore, the thickness distribution is measured multiple times by shifting in a direction perpendicular to the linear movement direction, and the position where the distance between the two boundary positions 107 is the largest is the diameter 106. [Explanation of symbols]

[0060] 1 Grinding equipment 2 Equipment base 3 Columnar part 10 Chuck table 11 Holding surface 12. Turntable 13 Loading / unloading area 14 Rough grinding area 15 Finish grinding area 16 Contact thickness measurement unit 17 First contact 18 Second Contact 20 Grinding unit 20-1 Rough grinding unit 20-2 Finish grinding unit 21 Spindle housing 22 Spindle 23 Motor 24 Grinding Wheel 25 Wheel base 26 Grindstone Department 30, 30-1, 30-2 Grinding movement mechanism 40, 40-1, 40-2 diameter adjustment mechanism 50 Cleaning Unit 51 Cleaning Table 52 Holding surface 60 Non-contact thickness measurement unit 61 Swing Arm 62 Measuring Head 70, 70-1, 70-2 Cassette 71 Cassette placement table 72 Alignment unit 80 Transport unit 81 Loading / unloading unit 82 Loading unit 83 Unloading unit 90 Control Unit 91 Target diameter memory section 92 Diameter calculation section 93 Difference calculation part 94 Command Department 100 wafers 101 Surface 102 Circular recess 103 Circular recess 104 Ring-shaped reinforcement 105 Aim diameter 106 diameter 107 Boundary position

Claims

1. A grinding apparatus for forming a circular recess and a ring-shaped reinforcing portion surrounding the circular recess on a surface of a wafer by grinding the surface of the wafer, comprising: a chuck table for holding the wafer; a grinding unit having a grinding wheel at a tip of a spindle, the grinding wheel including a grinding stone portion arranged in a ring shape having a diameter equal to or smaller than the radius of the wafer and a wheel base supporting the grinding stone portion; a grinding movement mechanism that relatively moves the grinding unit and the chuck table in the direction of the rotation axis of the spindle; a diameter adjustment mechanism that relatively moves the grinding unit and the chuck table in a direction perpendicular to the rotation axis of the spindle; a non-contact thickness measurement unit for measuring the thickness distribution of the wafer; A control unit, The control unit a target diameter storage unit that stores a target diameter of a circular recess to be formed on the wafer; a diameter calculation unit that calculates a diameter of the circular recess formed on the wafer based on the thickness distribution measured by the non-contact thickness measurement unit; and a command unit that commands the diameter adjustment mechanism to make a correction based on a difference between the target diameter stored in the target diameter storage unit and the diameter calculated by the diameter calculation unit. A grinding apparatus comprising:

2. The non-contact thickness measurement unit measures a thickness distribution of the wafer held on the chuck table.

2. The grinding apparatus according to claim 1 .

3. The non-contact thickness measurement unit includes: The chuck table holding the wafer is rotated to measure three or more boundary positions between the circular recess and the ring-shaped reinforcing portion; The diameter calculation unit is Calculating a diameter of the circular recess based on the boundary position measured by the non-contact thickness measurement unit.

3. The grinding apparatus according to claim 1 or 2.

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