Grinder and wafer grinding method

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; a diameter measurement unit (an imaging unit 60 and a diameter calculation part 93) which measures a diameter of a circular recessed part formed on a surface of the wafer 100; a target diameter storage part 91 which stores a target diameter of the circular recessed part to be formed in the wafer 100; and a command part 95 which commands the diameter regulation mechanism 40 to make correction based on a difference between the target diameter and the measured diameter.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a grinding apparatus and a method for grinding a wafer. [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 and a wafer grinding method 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 problems and achieve the object, the grinding device of the present invention is a grinding device that grinds the 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 wheel 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 wheel 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, a diameter adjustment mechanism that moves the grinding unit and the chuck table relatively in a direction perpendicular to the rotation axis of the spindle, a diameter measurement unit that measures the diameter of the circular recess, and a control unit, and the control unit includes a target diameter memory unit that stores a target diameter of the circular recess to be formed on the wafer, 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 measured by the diameter measurement unit.

[0009] In addition, in the grinding apparatus of the present invention, the diameter measurement unit may include an imaging unit that captures an image of the circular recess formed in the wafer by an imaging camera, and a diameter calculation unit that calculates the diameter of the circular recess based on the captured image.

[0010] In addition, the grinding apparatus of the present invention may further include a cleaning unit having a cleaning table that holds the wafer and cleans the wafer held on the cleaning table, wherein the imaging unit rotates the chuck table or the cleaning table on which the wafer is held to image 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 imaged by the imaging unit.

[0011] Moreover, a wafer grinding method of the present invention is a wafer grinding method using the grinding apparatus to form a circular recess and a ring-shaped reinforcing portion surrounding the circular recess on a surface of the wafer, the method comprising: a holding step of holding the wafer on the chuck table; a pre-grinding step of grinding the surface of the wafer while positioning the wafer at a position where the circular recess to be formed on the surface of the wafer is smaller than the target diameter by the diameter adjustment mechanism, thereby forming a circular recess having a diameter smaller than the target diameter on the surface of the wafer; and a diameter measuring step of measuring the diameter of the circular recess after the pre-grinding step; a difference calculating step of calculating the difference between the diameter measured in the diameter measuring step and the target diameter; and a main grinding step of correcting the difference by the diameter adjustment mechanism and forming a circular recess of the target diameter on the surface of the wafer. Effect of the Invention

[0012] The present invention can automatically adjust the positional relationship between the spindle and the chuck table. [Brief description of the drawings]

[0013] [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 flowchart showing the flow of the wafer grinding method according to the embodiment. [Figure 4] FIG. 4 is a side view, partially in section, showing one state of the holding step shown in FIG. [Diagram 5] FIG. 5 is a side view, partly in section, showing one state of the pre-grinding step shown in FIG. [Figure 6] FIG. 6 is a side view, partially in section, showing one state of the diameter measurement step shown in FIG. [Figure 7] FIG. 7 is a plan view of a wafer for explaining the diameter measuring step shown in FIG. [Figure 8] FIG. 8 is a side view, partly in section, showing one state of the main grinding step shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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.

[0015] 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.

[0016] [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 measurement unit 16, a grinding unit 20, a grinding movement mechanism 30, a diameter adjustment mechanism 40, a cleaning unit 50, an imaging unit 60, a cassette mounting table 71, an alignment unit 72, a transport unit 80, and a control unit 90.

[0017] 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. 8). 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.

[0018] 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).

[0019] 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.

[0020] 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.

[0021] The contact type thickness measuring units 16 are provided at two locations, near the rough grinding region 14 and near the finish grinding region 15. 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 units 16 include a first contactor 17, a second contactor 18, and a thickness calculating section (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 section may be configured as a part of the function of a control unit 90 described later.

[0022] 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).

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The imaging unit 60 includes an imaging camera such as a CCD (Charge Coupled Device) camera or an infrared camera that images the circular recess 103 (see FIG. 6) of the wafer 100. The imaging unit 60 of the embodiment images the wafer 100 held on the holding surface 52 of the cleaning table 51. The imaging unit 60 rotates the cleaning table 51 on which the wafer 100 is held, and images three or more boundary positions 107 (see FIG. 7) between the circular recess 103 and the ring-shaped reinforcement portion 104 (see FIG. 6). The imaging unit 60 images an imaging region 61 (see FIG. 7) including the boundary position 107, and outputs the captured image to the control unit 90. The imaging unit 60 in the embodiment and a diameter calculation unit 93 of the control unit 90 described later correspond to the diameter measurement unit of the present invention. The diameter measurement unit measures the diameter of the circular recess 103 formed on the surface 101 of the wafer 100 described later.

[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 grinding unit 20, the grinding movement mechanism 30, the diameter adjustment mechanism 40, the cleaning unit 50, the imaging unit 60, 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, an image processing unit 92, a diameter calculation unit 93, a difference calculation unit 94, and a command unit 95.

[0037] The target diameter storage unit 91 stores a target diameter 105 (see FIG. 8) of a circular recess 102 (see FIG. 8) 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 image processing unit 92 acquires an image of the wafer 100 captured by the imaging unit 60. The image processing unit 92 processes the acquired image to extract at least three boundary positions 107 (see FIG. 7 ) between the circular recess 103 and the ring-shaped reinforcing portion 104. The image processing unit 92 outputs the XY coordinates of the extracted boundary positions 107 to the diameter calculation unit 93.

[0039] The diameter calculation unit 93 calculates the diameter 106 (see FIG. 7) of the circular recess 103 based on the captured image captured by the imaging unit 60. The diameter calculation unit 93 calculates the diameter 106 of the circular recess 103 based on the boundary positions 107. In the embodiment, the diameter calculation unit 93 first acquires the XY coordinates of the three boundary positions 107 identified by the image processing unit 92. The diameter calculation unit 93 calculates a circle passing through the coordinates of the boundary positions 107, i.e., the diameter 106 of the circular recess 103. The diameter calculation unit 93 calculates the diameter 106 of the circular recess 103 based on the XY coordinates of the four or more boundary positions 107 using, for example, the least squares method.

[0040] The difference calculation unit 94 calculates the difference between the target diameter 105 stored in the target diameter storage unit 91 and the diameter 106 measured by the diameter measurement unit (in the embodiment, the imaging unit 60 and the diameter calculation unit 93).

[0041] The command unit 95 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 measured by the diameter measurement unit (in the embodiment, the imaging unit 60 and the diameter calculation unit 93). That is, the command unit 95 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.

[0042] Next, a method for grinding the wafer 100 in the embodiment will be described. As a preliminary preparation for a series of grinding steps, the unprocessed wafer 100 is placed on the cassette mounting 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 the factory facility in which the grinding apparatus 1 is installed. In addition, an empty cassette 70-2 is prepared on the cassette mounting table 71 of the grinding apparatus 1.

[0043] 3 is a flowchart showing a flow of a method for grinding a wafer 100 according to an embodiment. The method for grinding a wafer 100 is a method for forming a circular recess 102 and a ring-shaped reinforcing portion 104 surrounding the circular recess 102 on the surface 101 of the wafer 100 by using the grinding apparatus 1 described above and grinding the surface 101 of the wafer 100. The method for grinding a wafer 100 according to the embodiment includes a holding step 201, a pre-grinding step 202, a diameter measuring step 203, a difference calculation step 204, and a main grinding step 205.

[0044] (Retention step 201) Fig. 4 is a side view, partially in cross section, showing one state of the holding step 201 shown in Fig. 3. The holding step 201 is a step in which the wafer 100 is held by the chuck table 10. The control unit 90 shown in Fig. 1 drives the carry-in / out unit 81 to take out the unground wafers 100 contained 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.

[0045] 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 the 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 the processing area by the rough grinding unit 20-1. This completes the holding step 201.

[0046] (Pre-grinding step 202) Fig. 5 is a side view, partially in cross section, showing one state of the pre-grinding step 202 shown in Fig. 3. The pre-grinding step 202 is performed after the holding step 201. The pre-grinding step 202 is a step of grinding the front surface 101 of the wafer 100 to form a circular recess 103 having a diameter smaller than a target diameter 105 in the front surface 101 of the wafer 100.

[0047] In the pre-grinding step 202, first, the control unit 90 controls the diameter adjustment mechanism 40-1 to position the rough grinding unit 20-1 at a position where the circular recess 103 to be 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 it for processing while supplying grinding fluid to the surface machined by the rough grinding unit 20-1.

[0048] 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.

[0049] The control unit 90 rotates the turntable 12 by 120 degrees, 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 finish-ground wafer 100 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.

[0050] 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 horizontally 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.

[0051] (Diameter measurement step 203) Fig. 6 is a side view partially in cross section showing one state of the diameter measuring step 203 shown in Fig. 3. Fig. 7 is a plan view of the wafer 100 for explaining the diameter measuring step 203 shown in Fig. 3. The diameter measuring step 203 is performed after the pre-grinding step 202. The diameter measuring step 203 is a step for measuring the diameter 106 of the circular recess 103.

[0052] In the diameter measurement step 203, first, the imaging unit 60 uses an imaging camera to image the circular recess 103 of the wafer 100 held on the holding surface 52 of the cleaning table 51. More specifically, the imaging unit 60 images the boundary position 107 between the circular recess 103 and the ring-shaped reinforcement portion 104 at any position in the circumferential direction. Next, the cleaning table 51 is rotated by a predetermined angle (for example, 120 degrees each time) to image the boundary position 107 between the circular recess 103 and the ring-shaped reinforcement portion 104, thereby imaging three or more boundary positions 107. The imaging unit 60 outputs the captured image to the control unit 90.

[0053] In the diameter measurement step 203, the image processing unit 92 of the control unit 90 next processes the image captured by the imaging unit 60 to extract the boundary position 107 between the circular recess 103 and the ring-shaped reinforcing portion 104, and obtains the XY coordinates of the boundary position 107. Next, the diameter calculation unit 93 of the control unit 90 calculates the diameter 106 of the circular recess 103 based on the boundary position 107.

[0054] (Difference calculation step 204) The difference calculation step 204 is a step for calculating the difference between the diameter 106 measured in the diameter measurement step 203 and the target diameter 105. The difference calculation section 94 of the control unit 90 acquires information on the target diameter 105 stored in the target diameter storage section 91. The difference calculation section 94 also acquires the diameter 106 of the circular recess 103 calculated by the diameter calculation section 93 in the diameter measurement step 203. The difference calculation section 94 calculates the difference between the acquired diameter 106 and the target diameter 105.

[0055] (Main grinding step 205) Fig. 8 is a side view, partially in cross section, showing one state of the main grinding step 205 shown in Fig. 3. The main grinding step 205 is a step in which the difference between the diameter 106 of the circular recess 103 and the target diameter 105 of the circular recess 102 is corrected by the diameter adjustment mechanism 40, and the circular recess 102 having the target diameter 105 is formed on the front surface 101 of the wafer 100.

[0056] The wafer 100 in which the circular recess 102 of the target diameter 105 is formed in the main grinding step 205 may be the same wafer 100 as the wafer 100 in which the circular recess 103 of the diameter 106 smaller than the target diameter 105 was formed in the pre-grinding step 202, or it may be a different wafer 100 that has been newly removed from the cassette 70-1 and transported.

[0057] When processing another wafer 100, the wafer 100 whose diameter 106 has been measured while held on the holding surface 52 of the cleaning table 51 of the cleaning unit 50 is removed from the cleaning unit 50 and placed in a specified slot of the cassette 70-2, and the holding step 201 is performed on the new wafer 100 before grinding that is placed in the cassette 70-1.

[0058] In the main grinding step 205, based on the difference between the diameter 106 of the circular recess 103 calculated by the difference calculation unit 94 and the target diameter 105 of the circular recess 102, the command unit 95 controls the diameter adjustment mechanism 40-1 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 area 14 is adjusted.

[0059] The subsequent steps are the same as those in the pre-grinding step 202, and therefore will not be described. 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. After the grinding is completed, the wafer 100 is cleaned in the cleaning unit 50 and then stored in the cassette 70-2 by the carry-in / out unit 81.

[0060] The above process may be performed in parallel on a plurality of wafers 100. That is, for example, while a wafer 100 is being processed by the grinding unit 20, another wafer 100 may be being cleaned by the cleaning unit 50.

[0061] As described above, the grinding apparatus 1 and the grinding method for the wafer 100 according to the embodiment measure the diameter 106 of the circular recess 103 formed on the surface 101 of the wafer 100, and automatically adjust 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.

[0062] 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.

[0063] For example, the mounting position of the imaging camera of the imaging unit 60 may be a position where the imaging camera can image the wafer 100 held on the holding surface 11 of the chuck table 10. In this case, the imaging unit 60 rotates the chuck table 10 on which the wafer 100 is held, and images three or more points of the boundary position 107 between the circular recess 103 and the ring-shaped reinforcing portion 104.

[0064] 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, the imaging unit 60 images three or more outer periphery positions of the wafer 100 when imaging the boundary position 107 between the circular recess 103 and the ring-shaped reinforcement portion 104. The image processing section 92 processes the acquired captured images to extract at least three outer periphery positions of the wafer 100, similar to the boundary position 107. The center shift amount calculation section calculates the center coordinates of the circular recess 103 from the three or more boundary positions 107, and calculates the center coordinates of the wafer 100 from the three or more outer periphery positions, and calculates the center shift amount from each center coordinate. [Explanation of symbols]

[0065] 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 Imaging unit (diameter measurement unit) 61 Imaging area 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 Image Processing Section 93 Diameter calculation unit (diameter measurement unit) 94 Difference calculation part 95 Command Department 100 wafers 101 Surface 102 Circular recess 103 Circular recess 104 Ring-shaped reinforcement 105 Aim diameter 106 diameter 107 Boundary position 201 Retention Step 202 Pre-grinding step 203 Diameter Measurement Step 204 Difference calculation step 205 Grinding Steps

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 diameter measuring unit for measuring the diameter of the circular recess; 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 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 measured by the diameter measurement unit. A grinding apparatus comprising:

2. The diameter measuring unit comprises: an imaging unit that captures an image of the circular recess formed on the wafer by an imaging camera; A diameter calculation unit that calculates a diameter of the circular recess based on the captured image.

2. The grinding apparatus according to claim 1 .

3. a cleaning unit having a cleaning table for holding the wafer and cleaning the wafer held on the cleaning table; The imaging unit includes: The chuck table or the cleaning table on which the wafer is held is rotated, and images of three or more boundary positions between the circular recess and the ring-shaped reinforcing portion are taken; The diameter calculation unit is calculating a diameter of the circular recess based on the boundary position imaged by the imaging unit; 3. The grinding apparatus according to claim 2.

4. A method for grinding a wafer, comprising the steps of: forming a circular recess on a surface of the wafer and a ring-shaped reinforcing portion surrounding the circular recess; and a holding step of holding the wafer on the chuck table; a pre-grinding step of grinding the surface of the wafer while positioning the wafer at a position where the circular recess to be formed in the surface of the wafer by the diameter adjustment mechanism is smaller than the target diameter, thereby forming a circular recess having a diameter smaller than the target diameter in the surface of the wafer; a diameter measuring step of measuring a diameter of the circular recess after the pre-grinding step; a difference calculation step of calculating a difference between the diameter measured in the diameter measurement step and the target diameter; and a main grinding step of correcting the difference by the diameter adjustment mechanism to form a circular recess having a target diameter on the surface of the wafer.

1. A method for grinding a wafer, comprising the steps of:

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