Workpiece processing method

Abstract

To process a workpiece while obtaining the total thickness of the workpiece in which a plurality of regions (layers, structures) are laminated.SOLUTION: A processing method of thinning a workpiece in which a first region and a second region are laminated, the processing method comprising: a first acquisition step of acquiring a thickness of the first region; a first processing step of bringing a processing tool into contact with the workpiece held on a holding table to thin the second region; a second acquisition step of measuring and acquiring a thickness of the second region of the workpiece thinned in the first processing step; and an adjustment step of adjusting a positional relationship between the processing tool and the holding table with reference to a total thickness of the workpiece including the thickness of the first region acquired in the first acquisition step and the thickness of the second region acquired in the second acquisition step. And a second processing step of bringing the processing tool into contact with the workpiece held by the holding table to thin the workpiece.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for processing a workpiece, such as a semiconductor wafer, by holding the workpiece on a holding table and processing the workpiece held on the holding table to thin it. [Background technology]

[0002] Device chips equipped with devices such as ICs (Integrated circuits) and LSIs (Large Scale Integration) are manufactured from disk-shaped wafers. Multiple devices are provided on the front surface of the wafer, and the wafer is ground and polished from the back side to thin it, and then divided into individual device chips. Alternatively, device chips are manufactured from package substrates formed by sealing multiple devices with resin or the like. The package substrate is ground and polished from the sealing material side to thin it, and then divided into individual device chips.

[0003] Grinding of workpieces such as wafers is performed by a grinding apparatus, and polishing of the workpiece is performed by a polishing apparatus. Processing apparatuses such as grinding apparatuses and polishing apparatuses have a holding table (chuck table) that holds the workpiece, and a processing unit that processes the workpiece held by the holding table with processing tools such as a grinding wheel or a polishing pad.

[0004] The processing device further includes a thickness gauge that measures the thickness of each point of the workpiece, obtains the thickness distribution of the workpiece during or after processing, and adjusts the positional relationship between the processing tool and the holding table before carrying out the next processing (see Patent Documents 1 to 4).A known thickness gauge that is included in processing devices is a non-contact type that measures the thickness of the workpiece by irradiating the workpiece with light, ultrasonic waves, or the like. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-112493 [Patent Document 2] Japanese Patent Application Publication No. 2-274459 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-119123 [Patent Document 4] Japanese Patent Publication No. 2022-133006 Summary of the Invention [Problem to be solved by the invention]

[0006] Processing equipment may process a workpiece in which multiple regions (layers, structures) with different properties are stacked. For example, processing equipment may process a wafer in which multiple layers with different functions and shapes are stacked. Also, processing equipment may process a stack of multiple wafers, such as a WLCSP (Wafer Level Chip Size (Scale) Package).

[0007] When thinning these workpieces, it is necessary to thin them so that the overall thickness (total thickness) is a specified value, rather than the thickness of each region that makes up the workpiece. If the entire workpiece is not finished to a specified uniform thickness, air bubbles will form at the bonding surface when the workpieces are bonded together.

[0008] In addition, wafers (chips) molded with encapsulants such as SiO2 or resin may be thinned using processing equipment. Whether the encapsulant is thinned to expose the chip electrodes or the encapsulant is processed and thinned to leave it on the workpiece, it is desirable for the entire workpiece to be made uniform to a specified thickness.

[0009] Thickness gages used to measure the thickness of workpieces near the processing point during or after processing typically use non-contact thickness gages that measure thickness using light, ultrasound, or other methods to prevent damage to the workpiece. However, for workpieces formed by stacking multiple regions (layers, structures), if certain regions of the workpiece are poorly penetrated by the light or ultrasound emitted by a non-contact thickness gage, the total thickness of the workpiece cannot be measured using a single thickness gage. This means that a single thickness gage cannot be used to measure the total thickness of the workpiece, and it is also impossible to adjust the positional relationship between the processing tool and the holding table using the workpiece's thickness distribution. This is problematic because it makes it impossible to process the workpiece into the desired shape.

[0010] The present invention has been made in consideration of such problems, and its purpose is to provide a method for processing a workpiece that can process the workpiece while obtaining the total thickness of the workpiece in which multiple regions (layers, structures) are stacked. [Means for solving the problem]

[0011] According to one aspect of the present invention, there is provided a method for thinning a workpiece having a first region and a second region stacked thereon, the method comprising: a first acquisition step for acquiring the thickness of the first region; a first processing step for contacting a processing tool with the workpiece held on a holding table to thin the second region; a second acquisition step for measuring and acquiring the thickness of the second region of the workpiece thinned in the first processing step; an adjustment step for adjusting the positional relationship between the processing tool and the holding table by referring to the total thickness of the workpiece, which includes the thickness of the first region acquired in the first acquisition step and the thickness of the second region acquired in the second acquisition step; and a second processing step for contacting the processing tool with the workpiece held on the holding table to thin the workpiece after the positional relationship between the processing tool and the holding table has been adjusted.

[0012] Preferably, in the second obtaining step, the thickness of the second region of the workpiece is measured by a thickness measuring device that performs thickness measurement without contacting the workpiece.

[0013] Alternatively, preferably, in the second acquisition step, the thickness of the second region of the workpiece is measured using a thickness measuring device that performs thickness measurements using light or ultrasound without contacting the workpiece, and the second region of the workpiece is more transparent to the light or ultrasound used by the thickness measuring device than the first region of the workpiece.

[0014] Also, preferably, the first acquisition step acquires the thickness of the first region at a position that is a first distance away from the center of the workpiece and at a position that is a second distance away from the center of the workpiece that is different from the first distance, and the second acquisition step acquires the thickness of the second region at a position that is the first distance away from the center of the workpiece and at a position that is the second distance away from the center of the workpiece.

[0015] Also, preferably, the second obtaining step is performed after the first machining step and before the second machining step, in a state where the machining tool is not in contact with the workpiece.

[0016] Alternatively, preferably, the second obtaining step is performed during the first processing step or after the first processing step with the processing tool in contact with the workpiece.

[0017] Preferably, the thickness of the first region acquired in the first acquisition step is calculated by subtracting the thickness of the second region from the total thickness of the workpiece.

[0018] Preferably, the first obtaining step is performed in a state where the workpiece is not held on the holding table. [Effects of the Invention]

[0019] In a method for processing a workpiece according to one aspect of the present invention, a processing tool is brought into contact with the workpiece held on a holding table in a first processing step, and then the positional relationship between the processing tool and the holding table is adjusted based on the total thickness of the workpiece. Then, in a second processing step, the workpiece is further thinned in a state in which the positional relationship between the processing tool and the holding table has been adjusted.

[0020] Here, the total thickness of the workpiece referred to when adjusting the positional relationship between the machining tool and the holding table includes the thickness of the first region of the workpiece and the thickness of the second region. The thickness of the second region is acquired in the second acquisition step by measuring the workpiece thinned in the first processing step. Meanwhile, the thickness of the first region is acquired in the first acquisition step, which is separate from the second acquisition step. That is, the thickness of the first region and the thickness of the second region are acquired separately.

[0021] Therefore, even if the thickness of the first region cannot be obtained by measurement in the second obtaining step, the total thickness of the workpiece can be referenced when adjusting the positional relationship between the processing tool and the holding table, which means that position adjustment can be performed so that the workpiece can be subsequently thinned to a predetermined shape.

[0022] Therefore, the present invention provides a method for processing a workpiece that can process a workpiece while obtaining the total thickness of the workpiece in which a plurality of regions (layers, structures) are stacked. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a perspective view schematically illustrating a processing device and a workpiece according to an example. [Figure 2] FIG. 2(A) is a cross-sectional view schematically showing an example of a workpiece, and FIG. 2(B) is a cross-sectional view schematically showing a simplified workpiece. [Figure 3] FIG. 2 is a cross-sectional view schematically showing a processing unit and a holding table. [Figure 4] FIG. 2 is a plan view schematically showing the positional relationship between a holding table and a grinding wheel. [Figure 5] FIG. 5(A) is a graph that schematically shows one element of the thickness distribution of the workpiece, and FIG. 5(B) is a graph that schematically shows another element of the thickness distribution of the workpiece. [Figure 6] FIG. 2 is a cross-sectional view schematically showing a thickness measurement unit. [Figure 7] FIG. 10 is a cross-sectional view schematically showing a thickness measurement unit according to a modified example. [Figure 8] FIG. 2 is a plan view schematically showing the back side of the workpiece. [Figure 9] Figure 9(A) is a cross-sectional view schematically showing the workpiece before processing, Figure 9(B) is a cross-sectional view schematically showing the workpiece after the first processing step has been performed, and Figure 9(C) is a cross-sectional view schematically showing the workpiece 1 that has been thinned to a predetermined thickness. [Figure 10] FIG. 10(A) is a flowchart showing the flow of each step of a method for processing a workpiece, and FIG. 10(B) is a flowchart showing the flow of each step of a method for processing a workpiece according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0024] An embodiment of the present invention will be described with reference to the drawings. In a method for processing a workpiece according to this embodiment, the workpiece is thinned. First, the workpiece will be described. FIG. 1 includes a perspective view that schematically shows an example of a workpiece 1. FIG. 2(A) is a cross-sectional view that schematically shows an example of a workpiece 5. FIG. 2(B) is a cross-sectional view that schematically shows a representative example of the workpieces 1 and 5.

[0025] The workpiece 1 is, for example, a substantially circular wafer made of a material such as Si, SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor. A plurality of devices are arranged in a matrix on the surface 1a of the workpiece 1, such as a circular wafer, and the workpiece 1 is divided into individual devices to obtain individual device chips. In this case, if the workpiece 1 is thinned in advance, thin device chips can be obtained in the end.

[0026] In the method for processing a workpiece 1 according to this embodiment, the workpiece 1 is thinned. A tape-like protective member 3 for protecting devices and the like formed on the surface 1a is attached to the surface 1a, which is not the processing surface, of the workpiece 1 to be thinned.

[0027] The workpiece 1 processed by the processing equipment is composed of a variety of layers (inorganic insulating films, organic insulating films, conductive films, semiconductor layers, etc.) that constitute devices such as ICs and LSIs and have different functions and shapes. The processing equipment may also process a stack of multiple wafers, such as a WLCSP. The processing equipment may also process a workpiece 5 (substrate) as shown in FIG. 2(A), which is formed by molding chips 11 cut from a wafer with SiO2 or resin. However, the workpiece 1 is not limited to these.

[0028] In this way, various workpieces 1, 5 are processed and thinned in the processing device, but this can generally be generalized and simplified as a laminate formed by stacking a first region (layer, structure) 7 and a second region (layer, structure) 9. Figure 2(B) is a cross-sectional view showing a typical example of the workpiece 1, 5.

[0029] In a typical example of the workpiece 1, 5, the first region 7 may be composed of multiple layers or structures, or may be composed of a single layer or structure. The second region 9 may also be composed of multiple layers or structures, or may be composed of a single layer or structure. The first region 7 may not necessarily have a uniform thickness or shape throughout the entire workpiece 1, 5, and the second region 9 may not necessarily have a uniform thickness or shape throughout the entire workpiece 1, 5. Each region may be patterned into a predetermined shape.

[0030] In the processing device, the workpiece 1, 5 is processed from one side to be thinned. The structure exposed on the processing surface (rear surface 1b) of the workpiece 1 at this time is referred to as the second region 9. In the processing device, a processing tool comes into contact with the second region 9 and removes all or part of the second region 9 (for example, down to a thickness where a device is exposed). As described below, the second region 9 is a region whose thickness can be measured using a thickness measuring device, and all regions of the workpiece 1 that do not belong to the second region 9 may be referred to as the first region 7. Also, for example, the first region 7 refers to a region of the workpiece 1 whose thickness is relatively difficult to measure using a thickness measuring device described below.

[0031] The processing device then thins the workpieces 1, 5 so that they have a predetermined shape. For example, the processing device thins the workpieces 1, 5 so that they have a uniform predetermined thickness throughout. Alternatively, the processing device thins the workpieces 1, 5 so that the thickness distribution at each location becomes a predetermined thickness distribution.

[0032] Here, the processing device that thins the workpieces 1, 5 is, for example, a grinding device that grinds the workpiece 1 with a grinding wheel equipped with grinding stones arranged in a ring, or a polishing device that polishes the workpiece 1 by bringing a polishing pad into contact with the workpiece 1. Furthermore, the processing device that thins the workpieces 1, 5 may be a byte cutting device (surface planer) that cuts the workpieces 1, 5 with a byte tool that moves on a ring-shaped track.

[0033] In any case, the processing device that thins the workpiece 1, 5 in the processing method for the workpiece 1 according to this embodiment includes a holding table (chuck table) that holds the workpiece 1, 5, and a processing tool that comes into contact with the workpiece 1, 5 to thin the workpiece 1, 5. Below, the processing device used in the processing method for the workpiece 1 according to this embodiment will be described using a grinding device that grinds the workpiece 1, 5 to thin it. However, the processing device is not limited to a grinding device.

[0034] As shown in Fig. 1, grinding apparatus (processing apparatus) 2 includes a base 4 that supports each of its components. Cassette mounts 26a and 26b are fixed to the front end of base 4. Cassettes 28a and 28b, each housing a plurality of workpieces 1, are placed on cassette mounts 26a and 26b. In grinding apparatus 2, workpieces 1 are successively drawn out of cassettes 28a and 28b, ground (thinned), and the ground workpieces 1 are returned to cassettes 28a and 28b.

[0035] A wafer transfer robot 30 is installed at a position adjacent to the cassette mounting tables 26a and 26b on the base 4. The wafer transfer robot 30 takes out the workpiece 1 from the cassettes 28a and 28b placed on the cassette mounting tables 26a and 26b, and transfers the workpiece 1 to a positioning table 32 provided at a position adjacent to the wafer transfer robot 30 on the base 4.

[0036] The positioning table 32 has a plurality of positioning pins arranged in a ring shape. When the workpiece 1 is placed in the central placement area, the positioning table 32 moves each of the positioning pins radially inward in unison to position the workpiece 1 at a predetermined position.

[0037] A loading arm 34 and an unloading arm 36 are provided at positions adjacent to the positioning table 32 on the upper surface of the base 4. The workpiece 1 positioned at a predetermined position by the positioning table 32 is transported by the loading arm 34.

[0038] A disk-shaped turntable 6 is provided rotatably in a horizontal plane on the central upper surface of the base 4. Three holding tables (chuck tables) 8 are provided on the upper surface of the turntable 6, spaced 120 degrees apart from one another in the circumferential direction. When the turntable 6 is rotated, each holding table 8 that holds the workpiece 1 can be moved.

[0039] 3 is a cross-sectional view showing the holding table 8. The holding table (chuck table) 8 includes a disk-shaped porous member 8c having the same diameter as the workpiece 1, and a stainless steel frame 8b having an exposed recess for accommodating the porous member 8c. The frame 8b of the holding table 8 is provided with a suction path having one end reaching the bottom of the recess, and the other end of the suction path is connected to a suction source (not shown).

[0040] When the workpiece 1 is placed on the porous member 8c of the holding table 8 and the suction source is activated, negative pressure acts on the workpiece 1 through the suction path and the porous member 8c, and the workpiece 1 is sucked and held on the holding table 8. In other words, the upper surface of the holding table 8 serves as a holding surface 8a that holds the workpiece 1. As will be described later, this holding surface 8a has a conical shape with an extremely gentle slope.

[0041] A rotary drive source 56 such as a motor is connected to the bottom of the holding table 8, and the holding table 8 can rotate around a table rotation axis 58 that is set to pass through the center of the holding surface 8a.

[0042] The bottom 54 of the holding table 8 is supported by multiple support shafts in a manner that does not hinder rotation, and one or more of the support shafts are extendable. For example, in the grinding device 2, the bottom 54 is supported by one fixed shaft 60 and two extendable adjustment shafts 62, 64. By adjusting the lengths of these adjustment shafts 62, 64, the inclination of the holding surface 8a (the inclination of the table rotation shaft 58) can be changed. In other words, the adjustment shafts 62, 64 function as an inclination adjustment unit that adjusts the inclination of the table rotation shaft 58.

[0043] 1, the explanation will be continued. The workpiece 1 is loaded onto and unloaded from the holding table 8 in the wafer loading / unloading area of ​​the turntable 6. In the wafer loading / unloading area, the workpiece 1 can be loaded onto the holding table 8 by a loading arm 34, and can be unloaded from the holding table 8 by an unloading arm 36.

[0044] After the workpiece 1 is loaded by the loading arm 34 onto the holding table 8 positioned in the wafer loading / unloading area, the turntable 6 is rotated to move the holding table 8 to the next rough grinding area.

[0045] A first grinding unit 10a that roughly grinds the back surface 1b of the workpiece 1 held by a holding table 8 positioned in the rough grinding area is arranged outside the turntable 6 on the upper rear surface of the base 4. After the first grinding unit 10a has performed rough grinding of the workpiece 1, the turntable 6 is rotated to move the holding table 8 to a finish grinding area adjacent to the rough grinding area.

[0046] A second grinding unit 10b is disposed outside the turntable 6 on the upper rear surface of the base 4, and performs finish grinding on the back surface 1b of the workpiece 1 held on the holding table 8 positioned in the finish grinding area. After the second grinding unit 10b has performed finish grinding on the workpiece 1, the turntable 6 is rotated to return the holding table 8 to the wafer load / unload area, and the workpiece 1 is unloaded from the holding table 8 by the unloading arm 36.

[0047] A spinner cleaning device 38 that cleans and spin-dries the ground workpiece 1 is disposed near the unloading arm 36 on the upper surface of the base 4 and the wafer transfer robot 30. The workpiece 1 that has been cleaned and dried by the spinner cleaning device 38 is then transported from the spinner cleaning device 38 by the wafer transfer robot 30 and stored in cassettes 28a and 28b placed on cassette mounting tables 26a and 26b.

[0048] Columns 22a and 22b are erected at the rear of the base 4. A first grinding unit (processing unit) 10a is arranged in front of the column 22a so as to be able to rise and fall, and a second grinding unit (processing unit) 10b is arranged in front of the column 22b so as to be able to rise and fall.

[0049] The first grinding unit 10a includes a first spindle 14a extending vertically and a spindle motor 12a connected to the upper end of the first spindle 14a, while the second grinding unit 10b includes a second spindle 14b extending vertically and a spindle motor 12b connected to the upper end of the second spindle 14b.

[0050] The first grinding unit 10a includes a first lifting mechanism 24a that supports components of the first grinding unit 10a, including the first spindle 14a, so that they can move vertically. The second grinding unit 10b includes a second lifting mechanism 24b that supports components of the second grinding unit 10b, including the second spindle 14b, so that they can move vertically. The orientations of the spindles 14a and 14b may be adjustable.

[0051] 1 and 3 show the second lifting mechanism 24b. The second lifting mechanism 24b includes a pair of guide rails 24c provided vertically in front of the column 22b, a lifting plate 50 slidably supported on the guide rails 24c, and a ball screw 44 parallel to the pair of guide rails 24c. The components of the second grinding unit 10b are supported on the front surface of the lifting plate 50.

[0052] A nut portion 46 is provided on the back side of the lifting plate 50, and this nut portion 46 is threadedly engaged with a ball screw 44. A pulse motor 48 is connected to the upper end of the ball screw 44. When this pulse motor 48 is operated, the ball screw 44 rotates, and the lifting plate 50 moves up and down. The first lifting mechanism 24a is configured similarly to the second lifting mechanism 24b.

[0053] A disk-shaped wheel mount 16a is disposed at the lower end of the first spindle 14a, and a first grinding wheel (machining tool) 18a is fixed to the lower surface of the wheel mount 16a. That is, the first grinding wheel 18a is fixed to the lower end of the first spindle 14a. A plurality of first grinding stones 20a arranged in an annular shape are attached to the surface (lower surface) of the first grinding wheel 18a that faces the holding surface 8a of the holding table 8 positioned in the rough grinding region.

[0054] A disk-shaped wheel mount 16b is disposed at the lower end of the second spindle 14b, and a second grinding wheel (machining tool) 18b is fixed to the lower surface of the wheel mount 16b. That is, the second grinding wheel 18b is fixed to the lower end of the second spindle 14b. A plurality of second grinding stones 20b arranged in an annular shape are attached to the surface (lower surface) of the second grinding wheel 18b that faces the holding surface 8a of the holding table 8 positioned in the finish grinding region.

[0055] When the spindle motor 12a is operated to rotate the first spindle 14a, the first grinding wheel 18a rotates and the first grinding stone 20a moves on the first circular track. Then, the lifting mechanism 24a is operated to lower the first spindle 14a, and the first grinding stone 20a is brought into contact with the upper surface of the workpiece 1 held on the holding table 8, whereby the workpiece 1 is ground.

[0056] When the spindle motor 12b is operated to rotate the spindle 14b, the second grinding wheel 18b rotates and the second grinding stone 20b moves on the second circular track. Then, the lifting mechanism 24b is operated to lower the second spindle 14b, and the second grinding stone 20b is brought into contact with the upper surface of the workpiece 1 held on the holding table 8, whereby the workpiece 1 is ground.

[0057] In the first grinding unit 10a, the lifting mechanism 24a performs grinding feed at a relatively high speed, and the workpiece 1 is roughly ground. In the rough grinding by the first grinding unit 10a, most of the total grinding amount is ground until the workpiece 1 reaches the finishing thickness. In the second grinding unit 10b, the lifting mechanism 24b performs grinding feed at a relatively low speed, and the workpiece 1 is finish ground. In the finish grinding by the second grinding unit 10b, the workpiece 1 is ground until it reaches the finishing thickness, and roughness on the back surface 1b side is removed.

[0058] The first grinding wheel 20a and the second grinding wheel 20b contain abrasive grains made of diamond or the like and a binder that disperses and fixes the abrasive grains. The second grinding wheel 20b used for finish grinding preferably contains abrasive grains with a smaller particle size than the abrasive grains contained in the first grinding wheel 20a used for rough grinding. In this case, the first grinding wheel 20a can quickly rough-grind the workpiece 1, while the second grinding wheel 20b can finish-grind the workpiece 1 with high quality.

[0059] A first thickness gauge 40 for measuring the thickness of the workpiece 1 to be rough ground by the first grinding unit 10a is disposed on the upper surface of the base 4 near the first grinding unit 10a. A second thickness gauge 42 for measuring the thickness of the workpiece 1 to be finish ground by the second grinding unit 10b is disposed on the upper surface of the base 4 near the second grinding unit 10b.

[0060] The first thickness measuring device 40 is, for example, a contact-type thickness measuring device that comes into contact with the rear surface 1b of the workpiece 1. The contact-type thickness measuring device includes, for example, two probes (contactors) that extend above the holding table 8.

[0061] Each probe has a contact part extending downward from the tip of an arm extending horizontally. One probe measures the height of the back surface 1b of the workpiece 1 by bringing the lower end of the contact part into contact with the back surface 1b of the workpiece 1. The other probe measures the height of the holding surface 8a of the holding table 8 by bringing the lower end of the contact part into contact with the holding surface 8a.

[0062] The workpiece 1 is placed and held on the holding surface 8a of the holding table 8 via the protective member 3. Therefore, the contact-type thickness measuring instrument can calculate the total thickness of the workpiece 1 and the protective member 3 from the difference between the measured height of the back surface 1b of the workpiece 1 and the height of the holding surface 8a of the holding table 8.

[0063] The second thickness measuring device 42 is, for example, a non-contact type thickness measuring device that does not physically come into contact with the back surface 1b of the workpiece 1. The non-contact type thickness measuring device measures the thickness of the workpiece 1 by, for example, sending ultrasonic waves or light to the workpiece 1 from a measuring unit 42a disposed directly above the back surface 1b of the workpiece 1, receiving the reflected ultrasonic waves or the like at the measuring unit 42a, and analyzing the ultrasonic waves or the like.

[0064] The non-contact second thickness gauge 42 has, for example, a rotatable shaft 42b erected from the upper surface of the base 4 of the grinding device 2, and an arm 42c extending horizontally from the upper end of the shaft 42b, with the measuring unit 42a fixed to the tip of the arm 42c. A rotation mechanism (not shown) composed of a piston, a motor, or the like is connected to the lower end of the shaft 42b, and this rotation mechanism rotates the shaft 42b.

[0065] When the shaft 42b is rotated, the measuring unit 42a moves on an arc-shaped measurement orbit centered on the shaft 42b. That is, the grinding device 2 is provided with a measuring unit moving mechanism that moves the measuring unit 42a back and forth on the measurement orbit above the workpiece 1 held by the holding table 8. The measuring unit 42a is movable above the back surface 1b while the back surface 1b of the workpiece 1 is being ground by the second grinding unit 10b, and can measure the thickness of various points of the workpiece 1.

[0066] The grinding apparatus 2 further includes a controller (control unit) 90 that controls each of the components. The controller 90 controls, for example, the turntable 6, the holding table 8, the grinding units 10a and 10b, the wafer transfer robot 30, the positioning table 32, the loading arm 34, the unloading arm 36, the spinner cleaning device 38, and the like.

[0067] The controller 90 is configured by a computer including, for example, a processing device such as a CPU (Central Processing Unit) or a microprocessor, and a storage device such as a flash memory or a hard disk drive. The controller 90 operates the processing device in accordance with software such as a program stored in the storage device, thereby functioning as a concrete means in which the software and the processing device (hardware resource) work together.

[0068] The controller 90 stores in a storage device the processing conditions for grinding various types of workpieces 1 with the grinding units 10a, 10b, various information, etc. The processing conditions stored in the storage device include information such as the type and size of the workpiece 1 to be processed, the finishing thickness in rough grinding and finish grinding, and the rotation speed of the spindles 14a, 14b. Further details of the configuration of the controller 90 will be described later.

[0069] As shown in Figure 3 and other figures, the holding surface 8a of the holding table 8 is configured as an extremely gently sloping cone with its apex at the center. If the holding surface 8a is a cone, when the workpiece 1 is held by suction on the holding table 8, the workpiece 1 will deform slightly in accordance with the holding surface 8a. Note that the shapes of the workpiece 1, holding table 8, and the like shown in each figure are exaggerated for ease of explanation. The following explanation will be given using as an example the finish grinding performed by the second grinding unit 10b shown in Figure 3.

[0070] When grinding the workpiece 1, in this state, the holding table 8 is rotated around the table rotation axis 58, and the second spindle 14b is lowered while rotating, so that the second grinding wheel 20b comes into contact with the back surface 1b of the workpiece 1. Then, the workpiece 1 placed on the holding table 8 rotates while grinding progresses in an arc-shaped region from the center to the outer periphery of the workpiece 1, and the entire area of ​​the workpiece 1 is ground.

[0071] The inclination of the table rotation axis 58 is adjusted so that the generatrix constituting the holding surface 8a, which is formed by a conical surface, closest to the plane of rotation including the annular orbit of the second grinding wheel 20b is parallel to the plane of rotation, so that the front surface 1a and the back surface 1b of the ground workpiece 1 are parallel to each other. The thickness of the workpiece 1 is monitored by the second thickness gauge 42, and when the workpiece 1 reaches a predetermined thickness, the lowering of the second spindle 14b by the lifting mechanism 24b is stopped, and grinding of the workpiece 1 is completed.

[0072] For example, the controller 90 includes a grinding control unit 92 that controls each component to grind the workpiece 1. When the workpiece 1 is ground, the grinding control unit 92 rotates the holding table 8 that holds the workpiece 1 around the table rotation axis 58 and rotates the grinding wheels 18a, 18b of the grinding units 10a, 10b around the spindles 14a, 14b. Then, the spindles 14a, 14b are lowered by the lifting mechanisms 24a, 24b, and the grinding wheels 20a, 20b are brought into contact with the upper surface (rear surface 1b) of the workpiece 1 to grind the workpiece 1.

[0073] The grinding control unit 92 controls each component in accordance with the grinding conditions stored in the controller 90. While the grinding of the workpiece 1 progresses, the grinding control unit 92 monitors the thickness of the workpiece 1 using the thickness measuring devices 40, 42, and when the workpiece 1 reaches a predetermined thickness, stops the descent of the spindles 14a, 14b and stops grinding of the workpiece 1.

[0074] If the inclination of the table rotation axis 58 of the holding table 8 is not appropriate, the thickness distribution of the workpiece 1 will not be uniform, resulting in thickness deviations and preventing the front surface 1a and back surface 1b of the workpiece 1 from being parallel after grinding. Therefore, while the workpiece 1 is being ground, the measuring unit 42a of the second thickness gauge 42 is moved to measure the thickness of each point of the workpiece 1. Then, it is conceivable to monitor the thickness distribution of the workpiece 1 and adjust the inclination of the table rotation axis 58 using the inclination adjustment unit if a problem occurs with the thickness distribution.

[0075] The controller 90 monitors the thickness distribution of the workpiece 1 using the thickness measuring devices 40, 42, and controls the tilt adjustment unit to adjust the tilt of the table rotation axis 58 if a large thickness deviation is detected in the workpiece 1.

[0076] When adjusting the inclination of the table rotation axis 58, etc., the cross-sectional shape (thickness distribution) of the workpiece 1 is referenced. The controller 90 includes a thickness distribution specifying unit 94 that measures the thickness of each point of the workpiece 1 with the measuring unit 42a while moving the measuring unit 42a on the measurement track using the measuring unit moving mechanism, and specifies the thickness distribution of the workpiece 1.

[0077] Furthermore, the controller 90 calculates the amount of adjustment, such as the inclination of the table rotation axis 58, by the inclination adjustment unit, based on the calculated thickness distribution of the workpiece 1 so that the workpiece 1 ground by the grinding wheels 20a, 20b approaches a predetermined shape. More specifically, the controller 90 includes a positional relationship adjustment unit 96 that adjusts the positional relationship between the second grinding wheel (machining tool) 18b and the holding table 8.

[0078] The thickness distribution specifying unit 94 and the positional relationship adjusting unit 96 will be further described later in the description of the adjustment step S40 in the workpiece processing method according to this embodiment. The grinding control unit 92 controls the inclination adjusting unit and the like by referring to the calculated adjustment amount of the positional relationship, and adjusts the inclination of the table rotation axis 58, etc., to continue grinding (thinning processing) the workpiece 1.

[0079] Here, the relationship between the deviation in thickness distribution of the workpiece 1 during the grinding process and the inclination of the table rotation axis 58, etc. will be described in detail. The following explanation will be given taking as an example a scene where the workpiece 1 is finish-ground by the second grinding unit 10b, but this relationship also applies when the workpiece is rough-ground by the first grinding unit 10a.

[0080] Fig. 4 is a plan view schematically showing the planar positional relationship between the holding surface 8a of the holding table 8 and the annular track 20c on which the second grinding wheel 20b moves. In Fig. 4, the outline of the conical holding surface 8a of the holding table 8 and the annular track 20c are shown as a circle. The annular track 20c is a circle with the same diameter as the holding surface 8a of the holding table 8. The table rotation axis 58 of the holding table 8 passes through the center 68 of the holding surface 8a.

[0081] 4 also shows the positions of the fixed shaft 60 that supports the holding table 8 from below, and the two adjustment shafts 62 and 64. The fixed shaft 60 is located below approximately the center of the second grinding wheel 18b, and the fixed shaft 60 and the two adjustment shafts 62 and 64 are arranged to form the vertices of an equilateral triangle. The holding table 8 is supported by the fixed shaft 60 and the adjustment shafts 62 and 64, and the adjustment shafts 62 and 64 function as an inclination adjustment unit.

[0082] For example, when the adjustment shaft 64 is extended or retracted without extending or retracting the adjustment shaft 62, the inclination of the holding table 8 changes so that it rotates around a first axis 74 connecting the fixed shaft 60 and the adjustment shaft 62. When the adjustment shaft 62 is extended or retracted without extending or retracting the adjustment shaft 64, the inclination of the holding table 8 changes so that it rotates around a second axis 76 connecting the fixed shaft 60 and the adjustment shaft 64. In other words, when the adjustment shaft 62 and the adjustment shaft 64 are extended or retracted, the inclination of the table rotation shaft 58 can be changed.

[0083] When grinding the workpiece 1, the tilt of the table rotation axis 58 is adjusted by the tilt adjustment unit so that the generatrix connecting the center 68 and outer periphery 66 of the holding surface 8a, which overlaps with the annular orbit 20c, is parallel to the annular orbit 20c.

[0084] Then, the second grinding wheel 20b moving along the annular track 20c comes into contact with the back surface 1b of the workpiece 1 in a grinding region 72 between above the center 68 of the holding surface 8a and above the outer periphery 66, thereby grinding the workpiece 1. Note that the second grinding wheel 20b does not come into contact with the workpiece 1 in the region between above the center 68 of the holding surface 8a and above another outer periphery 70.

[0085] 5(A) and 5(B) are graphs illustrating the thickness distribution that appears on the workpiece 1 when grinding is performed on the workpiece 1 when the tilt of the table rotation axis 58 is inappropriate. In each graph, the horizontal axis represents the distance from the center of the workpiece 1, and the vertical axis represents the amount of thickness deviation of the workpiece 1.

[0086] When grinding the workpiece 1, the holding table 8 is rotated around the table rotation axis 58, and the second grinding wheel 18b is rotated around the second spindle 14b. At this time, a circular region at a given distance from the center of the workpiece 1 is ground in the same manner, so the thickness distribution of the workpiece 1 in this circular region is approximately constant. Therefore, as shown in the graphs of Figures 5(A) and 5(B), the thickness distribution of the workpiece 1 can be evaluated based on the relationship between the distance from the center of the workpiece 1 and the amount of thickness deviation of the workpiece 1.

[0087] The thickness distribution shown in the graph of Fig. 5(B) is an example of a thickness distribution that appears in the workpiece 1 when there is a slope across the entire grinding region 72 between the center and outer periphery of the workpiece 1. This thickness distribution appears in the workpiece 1 when the annular orbit 20c of the second grinding wheel 20b is not parallel to the generatrix connecting the center 68 and outer periphery 66 of the holding surface 8a.

[0088] More specifically, the thickness distribution shown in the graph of Fig. 5(B) is the thickness distribution when the distance between the holding surface 8a and the annular orbit 20c is greater at the center 68 of the holding surface 8a than at the outer periphery 66. The difference between the thickness at the center of the workpiece 1 and the thickness at the outer periphery of the workpiece 1 is shown in Fig. 5(B) as thickness deviation a. Note that when the distance between the holding surface 8a and the annular orbit 20c is greater at the outer periphery 66 of the holding surface 8a than at the center 68 of the holding surface 8a, deviation a takes a negative value.

[0089] This deviation a can also be called the "amount of convexity" due to the cross-sectional shape that appears on the workpiece 1 due to the deviation a. In order to eliminate the deviation in thickness distribution shown in the graph of Figure 5(B), it is sufficient to adjust mainly the length of the adjustment shaft 64 so that the holding surface 8a and the annular orbit 20c become parallel.

[0090] As shown in Figure 5(B), this thickness deviation can be expressed by a linear function of the distance from the center of the workpiece 1 (horizontal axis) and the amount of deviation in the thickness of the workpiece 1 (vertical axis). When the horizontal axis is zero, the vertical axis of this linear function becomes a, and when the horizontal axis becomes R, which is the radius of the workpiece 1, the vertical axis becomes zero.

[0091] The thickness distribution shown in the graph of Fig. 5(A) is an example of the thickness distribution that appears on the workpiece 1 when the grinding depth of the second grinding wheel 20b becomes shallow or deep in the central part of the grinding region 72 between the center and the outer periphery of the workpiece 1. In order to eliminate the bias in the thickness distribution shown in Fig. 5(A), it is advisable to adjust the adjustment shaft 64 mainly while adjusting the adjustment shaft 62 so as to correspond to the change in the inclination across the entire grinding region 72 that changes due to the adjustment of the adjustment shaft 62.

[0092] More specifically, the thickness distribution shown in the graph of Fig. 5(A) is the thickness distribution when the grinding depth of the second grinding wheel 20b is shallow in the center of the grinding region 72 between the center and the periphery of the workpiece 1. The difference between the thickness in the center of the grinding region 72 of the workpiece 1 and the thickness at the center and the periphery is shown in Fig. 5(A) as the thickness deviation m. When the center of the grinding region 72 of the workpiece 1 is ground deeper than the periphery, m becomes a negative value.

[0093] This deviation m can also be called the "seagull amount" due to the cross-sectional shape that appears on the workpiece 1 due to the deviation m. The adjustment amounts of the adjustment axes 62, 64 are preferably determined so that the deviation m becomes zero.

[0094] 5(A), this thickness deviation m can be expressed by a quadratic function of the distance from the center of the workpiece 1 (horizontal axis) and the amount of thickness deviation (vertical axis) of the workpiece 1. In this quadratic function, the vertical axis is zero when the horizontal axis is zero, the vertical axis is m when the horizontal axis is 0.5R, and the vertical axis is zero when the horizontal axis is R.

[0095] When the lengths of the adjustment shafts 62 and 64 are both appropriate, the thickness of the workpiece 1 is uniform throughout. When the lengths of the adjustment shafts 62 and 64 are both inappropriate, the thickness distribution appearing on the workpiece 1 is the sum of the thickness distribution shown in the graph in Fig. 5(A) and the thickness distribution shown in the graph in Fig. 5(B). Conversely, when the inclination of the table rotation shaft 58, etc. is inappropriate, the thickness distribution appearing on the workpiece 1 can be separated into the thickness distribution shown in the graph in Fig. 5(A) and the thickness distribution shown in the graph in Fig. 5(B).

[0096] The controller 90 calculates the adjustment amounts of the adjustment axes 62, 64 so that the deviation m in the graph shown in Fig. 5(A) becomes zero and the deviation a in the graph shown in Fig. 5(B) becomes zero. The grinding control unit 92 controls the inclination adjustment unit by referring to the calculation result, and adjusts the lengths of the adjustment axes 62, 64, thereby adjusting the inclination of the table rotation axis 58.

[0097] In addition to or instead of adjusting the inclination of the table rotation axis 58, the controller 90 may adjust the inclination of the spindles 14a, 14b so that the workpiece 1 has a desired shape as a result of machining. Also, the controller 90 may adjust the relative positional relationship between the holding table 8 and the grinding units 10a, 10b in a direction substantially parallel to the holding surface 8a of the holding table 8. As the grinding (machining) of the workpiece 1 progresses while these adjustments are being made, the workpiece 1 will eventually have a desired shape.

[0098] However, the contact-type thickness gauge 40 requires a probe or the like to come into contact with the object whose thickness is to be measured, which may result in the object being damaged by the probe. Furthermore, if the surface of the object is uneven, the probe may be damaged when it encounters a step on the object, or the probe may vibrate more violently. Furthermore, the non-contact type thickness gauge 42 may have higher measurement accuracy than the contact-type thickness gauge 40. Therefore, it is preferable to use the non-contact type thickness gauge 42, particularly for measuring the thickness of a workpiece 1 undergoing finish grinding.

[0099] On the other hand, depending on the configuration of the object to be measured, the non-contact thickness gauge 42 may not be able to measure the total thickness of the object to be measured. As described above, the workpiece 1 has a first region 7 and a second region 9 that overlaps with the first region 7. The first region 7 of the workpiece 1 may be less transparent than the second region to the light or ultrasonic waves that the non-contact thickness gauge 42 irradiates the workpiece 1 with. In other words, the second region 9 of the workpiece 1 may be more transparent than the first region 7 of the workpiece 1 to the light or ultrasonic waves used by the second thickness gauge 42.

[0100] In this case, even if the measuring unit 42a detects light or the like irradiated onto the workpiece 1 and emitted from the workpiece 1, it is possible to obtain information about the thickness of the second region 9, but it is difficult to obtain information about the thickness of the structures of the workpiece 1 that are below the first region 7. In other words, when the workpiece 1 formed by stacking multiple regions (layers, structures) in this way is used as the measurement object, it is difficult to measure the total thickness of the workpiece 1 with a single thickness measuring device placed near the processing point.

[0101] In this case, the total thickness of the workpiece 1 cannot be measured simply by using a single thickness measuring device, and the positional relationship between the processing tool and the holding table cannot be adjusted using the thickness distribution of the workpiece 1. This is problematic because the workpiece 1 cannot be processed into a predetermined shape. Therefore, in the method for processing a workpiece according to this embodiment, the workpiece 1 is processed while obtaining the total thickness of the workpiece 1, which is made up of multiple laminated regions (layers, structures), as described below.

[0102] Next, a method for processing a workpiece according to this embodiment will be described, taking as an example a case where the method is carried out mainly using a grinding device (processing device) 2. In particular, a case where a workpiece 1 having a first region 7 and a second region 9 stacked thereon is ground by a second grinding unit 10b to be thinned will be described as an example. Fig. 10(A) is a flowchart illustrating the flow of each step of a method for processing a workpiece according to one example.

[0103] First, a first acquisition step S10 is performed to acquire the thickness of the first region 7 of the workpiece 1, and then a first processing step S20 is performed to thin the second region 9 by bringing a grinding wheel (processing tool) 18b into contact with the workpiece 1 held on the holding table 8. Next, a second acquisition step S30 is performed to measure and acquire the thickness of the second region 9 of the workpiece 1 thinned in the first processing step.

[0104] Thereafter, an adjustment step S40 is performed in which the positional relationship between the grinding wheel (machining tool) 18b and the holding table 8 is adjusted with reference to the total thickness of the workpiece 1, including the thickness of the first region 7 and the thickness of the second region 9. Then, with the positional relationship between the grinding wheel (machining tool) 18b and the holding table 8 adjusted, a second processing step S50 is performed in which the grinding wheel (machining tool) 18b is brought into contact with the workpiece 1 held on the holding table 8 to perform thinning processing. Each step will be described in detail below.

[0105] The first acquisition step S10 will be described in detail. The first acquisition step S10 is preferably performed before the second region 9 of the workpiece 1 is machined by the grinding wheel (machining tool) 18b. More preferably, the first acquisition step S10 is performed during a waiting time before the workpiece 1 is transported to and held on the holding table 8, or before the workpiece 1 is held on the holding table 8 and machined by the grinding wheel 18b.

[0106] In the first acquisition step S10, the thickness of the first region 7 of the workpiece 1 is acquired. For example, the thickness of the first region 7 of the workpiece 1 is acquired by measurement. The thickness of the first region 7 acquired by measurement is stored in a memory unit of the controller 90. Alternatively, in the first acquisition step S10, the thickness of the first region 7 stored in advance in the memory unit of the controller 90 is acquired by reading it out from the memory unit for calculation.

[0107] When the thickness of the first region 7 of the workpiece 1 is obtained by measurement, or when the thickness of the first region 7 is measured in advance and stored in the controller 90, the measurement may be performed in the grinding apparatus 2 or outside the grinding apparatus 2. When the measurement is performed outside the grinding apparatus 2, the measurement is performed before the workpiece 1 is placed in the cassettes 28a, 28b.

[0108] Furthermore, when the thickness of the first region 7 of the workpiece 1 is measured by the grinding device 2, the measurement is preferably performed between the time when the workpiece 1 is removed from the cassettes 28a, 28b and the time when the workpiece 1 is transported to the holding table 8. In other words, the first acquisition step S10 is preferably performed when the workpiece 1 is not held on the holding table 8. When the workpiece 1 is not held on the holding table 8, the thickness of the first region 7 of the workpiece 1 can be measured and acquired by a method that cannot be performed when the workpiece 1 is held on the holding table 8 (for example, when at least a part of the surface held on the holding table 8 is exposed).

[0109] The grinding apparatus 2 may be equipped with, for example, a measurement unit that performs measurements on the workpiece 1 being transported by the wafer transport robot 30 or the loading arm 34, or may be equipped with a measurement unit that performs measurements on the workpiece 1 placed on the positioning table 32.

[0110] 6 is a cross-sectional view schematically showing the thickness measurement unit 100 used in the first acquisition step S10. The thickness measurement unit 100 is provided, for example, on the upper surface of the base 4 of the grinding apparatus 2. In particular, the thickness measurement unit 100 is preferably incorporated into the positioning table 32. However, the thickness measurement unit 100 may also be provided outside the grinding apparatus 2. The thickness measurement unit 100 includes a support part 102 that supports the workpiece 1 from below, and a measurement part 104 that measures the thickness of the workpiece 1 supported by the support part 102.

[0111] The support part 102 is formed in a substantially cylindrical shape and has a substantially annular upper surface 106. The workpiece 1, which is the object to be measured for thickness, is placed on the support part 102 so that its outer periphery overlaps the upper surface 106 of the support part 102. When the workpiece 1 is placed on the support part 102, the lower surface (surface 1a) of the workpiece 1 is exposed over almost the entire area except for a portion of the outer periphery of the workpiece 1.

[0112] The measuring section 104 includes, for example, a probe unit 116 that contacts the upper surface (rear surface 1b) of the workpiece 1, a probe unit 112 that contacts the lower surface (front surface 1a) of the workpiece 1, and a support 108 that supports the probe units 112 and 116 so that they can be raised and lowered. The support 108 is provided on the side of the support section 102.

[0113] The measuring unit 104 includes an arm 114 extending from the support 108 above the workpiece 1 supported by the support unit 102, and an arm 110 extending from the support 108 below the workpiece 1 supported by the support unit 102. A probe unit 116 is fixed to the tip of the arm 114, and a probe unit 112 is fixed to the tip of the arm 110. The probe unit 116 includes a probe (contactor) 120 that comes into contact with the top surface of the workpiece 1, and the probe unit 112 includes a probe (contactor) 118 that comes into contact with the bottom surface of the workpiece 1.

[0114] The support 108 has an internal lifting mechanism (not shown), such as a ball screw or cylinder type, which raises and lowers the arms 110, 114. The thickness measurement unit 100 raises and lowers the arms 110, 114 and detects contact between the probes 118, 120 and the workpiece 1, thereby detecting the height of the upper surface (rear surface 1b) and the lower surface (front surface 1a) of the workpiece 1. The difference between these two heights is then determined as the thickness (total thickness) of the workpiece 1.

[0115] In the thickness measurement unit 100, it is preferable that the shape and size of each component be determined so that the probes 118 and 120 overlap each other, thereby making it possible to simultaneously measure the heights of the upper and lower surfaces of the workpiece 1 at one location.

[0116] Furthermore, the thickness measurement unit 100 can change the positions of the probes 118, 120 relative to the workpiece 1. For example, the thickness measurement unit 100 can move the support 108 along a direction parallel to the upper surface 106 of the support part 102. Alternatively, the thickness measurement unit 100 can extend and retract the arms 110, 114. Furthermore, the thickness measurement unit 100 can rotate one or both of the support 108 and the workpiece 1 supported by the support part 102 around an axis along a direction perpendicular to the upper surface 106 of the support part 102.

[0117] The shape and position of the support portion 102 are determined so that it does not collide with the probe unit 112 and arm portion 110 that come into contact with the underside of the workpiece 1 when the positions of the probes 118, 120 relative to the workpiece 1 are changed.

[0118] The measuring section 104 of the thickness measuring unit 100 further includes a non-contact measuring head 122 that measures the thickness of the second region 9 of the workpiece 1. The measuring head 122 constitutes a non-contact thickness measuring device similar to the second thickness measuring device 42 described above. For example, ultrasonic waves or light are transmitted to the workpiece 1 from the measuring head 122 disposed directly above the rear surface 1b of the workpiece 1, and the reflected ultrasonic waves or the like are received by the measuring head 122. The thickness measuring unit 100 measures the thickness of the second region 9 by analyzing the ultrasonic waves or the like.

[0119] The thickness measurement unit 100 can then calculate the thickness of the first region 7 by subtracting the thickness of the second region 9 from the total thickness of the workpiece 1 measured by the measurement section 104. The measurement head 122 is capable of changing its position relative to the workpiece 1, similar to the probe units 112 and 116. By measuring the total thickness of the workpiece 1 and the thickness of the second region 9 at each point on the workpiece 1, the thickness of the first region 7 at each point on the workpiece 1 can be obtained. In other words, the thickness of the first region 7 obtained in the first obtaining step S10 may be calculated by subtracting the thickness of the second region 9 from the total thickness of the workpiece 1.

[0120] It should be noted that the thickness measurement unit used in the first obtaining step S10 does not need to measure the total thickness of the workpiece 1. A modified example of the thickness measurement unit used in the first obtaining step S10 will be described. Fig. 7 is a cross-sectional view schematically showing a thickness measurement unit 100a according to the modified example.

[0121] The thickness measurement unit 100a includes a support part 102a that supports the workpiece 1, similar to the thickness measurement unit 100 described in Fig. 6. The support part 102a is similar to the support part 102 of the thickness measurement unit 100. The workpiece 1 is placed on the support part 102a with the back surface 1b facing downward and the front surface 1a facing upward, for example.

[0122] The thickness measurement unit 100a includes a measurement head 122a that directly measures the thickness of the first region 7 of the workpiece 1. The measurement head 122a constitutes a non-contact thickness measuring device, similar to the above-described measurement head 122. However, the measurement head 122a irradiates the workpiece 1 with ultrasound, light, or the like, which is more easily transmitted through the first region 7 than the second region 9. The thickness measurement unit 100a then measures the thickness of the first region 7 by receiving the reflected ultrasound, light, or the like with the measurement head 122a and analyzing the ultrasound, light, or the like.

[0123] Alternatively, the thickness measurement unit 100a may measure the thickness of the second region 9. In this case, the measurement head 122a irradiates the workpiece 1 with ultrasound, light, or the like, which is more easily transmitted through the second region 9 than the first region 7. Then, the thickness measurement unit 100a may measure the thickness of the second region 9, and the thickness of the first region 7 may be calculated by subtracting the thickness of the second region 9 obtained by the measurement from the total thickness of the workpiece 1.

[0124] 7, the measuring head 122a may be disposed above the workpiece 1, or may be disposed below the workpiece 1. When the measuring head 122a is disposed below the workpiece 1 placed on the support part 102a, the workpiece 1 is placed on the support part 102a with the front surface 1a facing downward and the back surface 1b facing upward.

[0125] The thickness of the first region 7 of the workpiece 1 acquired in the first acquisition step S10 is measured by the thickness measurement units 100, 100a. In the first acquisition step S10, the thickness of the first region 7 of the workpiece 1 is measured and acquired by the thickness measurement units 100, 100a, and stored in the memory unit of the controller 90 of the grinding device 2. Alternatively, in the first acquisition step S10, the thickness of the first region 7 is acquired by subtracting the thickness of the second region 9 obtained by measurement from the total thickness of the workpiece 1 stored in the memory unit of the controller 90, and stored in the memory unit of the controller 90 of the grinding device 2. Alternatively, in the first acquisition step S10, the thickness of the first region 7 of the workpiece 1 stored in the memory unit of the controller 90 is read out from the memory unit.

[0126] According to the method for processing a workpiece according to this embodiment, a first processing step S20 is performed after the first acquisition step S10 or before the first acquisition step S10. In the first processing step S20, the workpiece 1 is transported to the holding table 8, and the holding table 8 holds the workpiece 1 by suction. Then, a second grinding wheel (processing tool) 18b is brought into contact with the workpiece 1 held on the holding table 8 to thin the second region 9. Note that the workpiece 1 may be ground with the first grinding wheel 18a before being ground with the second grinding wheel 18b.

[0127] 3 is a cross-sectional view schematically showing how the workpiece 1 held by the holding table 8 is ground. The thinning process is performed by rotating the second grinding wheel 18b and the holding table 8 around their respective rotation axes, lowering the second grinding unit 10b, and bringing the grinding stone 20b of the second grinding wheel 18b into contact with the back surface 1b of the workpiece 1. At this time, the lowering of the second grinding unit 10b is completed before the workpiece 1 is thinned to the final target finish thickness.

[0128] In the method for processing a workpiece according to this embodiment, a second obtaining step S30 is carried out in which the thickness of the second region 9 of the workpiece 1 thinned in the first processing step S20 is measured and obtained.

[0129] The second acquisition step S30 may be performed by a second thickness measuring device 42 of the grinding device (processing device) 2. That is, in the second acquisition step S30, the thickness of the second region 9 of the workpiece 1 may be measured by the second thickness measuring device 42, which performs thickness measurement using light or ultrasonic waves without contacting the workpiece 1. In this case, it is preferable that the second region 9 of the workpiece 1 is more transparent to the light or ultrasonic waves used by the second thickness measuring device 42 than the first region 7 of the workpiece 1.

[0130] The measurement of the thickness of the second region 9 of the workpiece 1 is performed, for example, after the first processing step S20 is completed and before the second processing step S50, which will be described later. In this case, it is preferable to retract the second grinding wheel (machining tool) 18b from the region above the workpiece 1 after the first processing step S20 is completed. In this case, the second acquisition step S30 is performed in a state where the second grinding wheel (machining tool) 18b is not in contact with the workpiece 1.

[0131] When the second grinding wheel 18b is retracted from the area above the workpiece 1, the measuring section 42a of the second thickness measuring device 42 can be moved to any position in the area above the workpiece 1 without being interfered with by the second grinding wheel (machining tool) 18b.

[0132] Here, the position where the thickness of the second region 9 is acquired in the second acquisition step S30 will be described. As will be described below, the position where the thickness of the second region 9 is acquired has a predetermined relationship with the position where the thickness of the first region 7 is acquired in the first acquisition step S10. Therefore, the position where the thickness of the first region 7 is acquired will also be described at the same time.

[0133] In the first acquisition step S10, it is not necessary to acquire the thickness of the first region 7 over the entire area of ​​the workpiece 1, and in the second acquisition step S30, it is not necessary to acquire the thickness of the second region 9 over the entire area of ​​the workpiece 1. As long as adjustment can be performed with sufficient accuracy in the adjustment step S40 described below, the number of positions on the workpiece 1 at which the thickness is acquired may be small. For example, if the thickness of the first region 7 and the thickness of the second region 9 are acquired at at least two positions on the workpiece 1, it may be possible to perform adjustment with sufficient accuracy in the adjustment step S40.

[0134] However, in order to calculate the total thickness at each location of the workpiece 1 in the adjustment step S40 described below, it is preferable that the positions at which the thickness is acquired on the workpiece 1 are the same in the first acquisition step S10 and the second acquisition step S30. In other words, at a specific position on the workpiece 1, it is preferable that the thickness of the first region 7 is acquired in the first acquisition step S10, and the thickness of the second region 9 is acquired in the second acquisition step S30.

[0135] However, the position at which the thickness of the workpiece 1 is acquired does not need to be completely the same in the first acquisition step S10 and the second acquisition step S30. Depending on the properties of the workpiece 1 and the details of the thinning process, the thickness of the first region 7 may be similar in a specific region of the workpiece 1 in a plane parallel to the front surface 1a and back surface 1b, and the thickness of the second region 9 may be similar in this specific region before and during the thinning process.

[0136] For example, in a plane parallel to the front surface 1a and the back surface 1b, the thickness of the first region 7 may be uniform in an annular region that is a collection of points a certain distance away from the center of the workpiece 1. In addition, in this annular region, the thickness of the second region 9 before thinning may be uniform, and the thickness of the second region 9 may also be uniform during the thinning process.

[0137] In this case, the thickness of the first region 7 may be acquired at a point belonging to the annular region in a first acquisition step S10, and the thickness of the second region 9 may be acquired at the same or another point belonging to the annular region in a second acquisition step S30. In this case, each acquired thickness can be treated as a representative value of the thickness in the annular region.

[0138] 8 is a plan view schematically showing the rear surface 1b side, which is the surface to be processed, of the workpiece 1. Fig. 8 shows positions on the workpiece 1 from which the thickness is acquired. For example, positions 13 from which the thickness is acquired are preferably located near the center of the workpiece 1, in an annular region 15 that is a distance half the radius of the rear surface 1b of the workpiece 1 from the center of the workpiece 1, and near the outer periphery of the workpiece 1.

[0139] The position in the workpiece 1 where the thickness of the first region 7 is acquired and the position where the thickness of the second region 9 is acquired will be described from another perspective. In the first acquisition step S10, it is preferable to acquire the thickness of the first region 7 at a position that is a first distance away from the center of the workpiece 1 and at a position that is a second distance away from the center of the workpiece 1 that is different from the first distance. Furthermore, in the second acquisition step S30, it is preferable to acquire the thickness of the second region 9 at the position that is the first distance away from the center of the workpiece 1 and at the position that is the second distance away from the center of the workpiece 1.

[0140] When the position 13 on the workpiece 1 where the thickness is acquired is determined in this manner, it is possible to adequately grasp the thickness trends of the first region 7 and the second region 9 over the entire area of ​​the workpiece 1. Then, adjustment can be performed with sufficient accuracy in the adjustment step S40.

[0141] As described above, in the second acquisition step S30, the thickness of the second region 9 of the thinned workpiece 1 is measured and acquired. The thickness of the second region 9 acquired in the second acquisition step S30 may be stored in a memory unit of the controller 90 of the grinding device (processing device) 2. This makes it possible to derive the total thickness of the thinned workpiece 1, and in the adjustment step S40 described next, adjustment can be performed based on the total thickness of the workpiece 1.

[0142] In the method for processing a workpiece according to this embodiment, an adjustment step S40 is performed. The adjustment step S40 is performed, for example, mainly by the thickness distribution specifying unit 94 and the positional relationship adjusting unit 96 of the controller 90. Therefore, the following description will be referred to as an explanation of the functions of the thickness distribution specifying unit 94 and the positional relationship adjusting unit 96 of the controller 90, as appropriate.

[0143] In the adjustment step S40, the positional relationship is adjusted between the second grinding wheel (machining tool) 18b and the holding table 8. This adjustment of the positional relationship is performed with reference to the total thickness of the workpiece 1, which includes the thickness of the first region 7 acquired in the first acquisition step S10 and the thickness of the second region 9 acquired in the second acquisition step S30.

[0144] When the adjusting step S40 is performed, the thickness of the first region 7 stored in the memory unit of the controller 90 of the grinding device (processing device) 2 is acquired. If the first acquiring step S10 is performed by acquiring the thickness of the first region 7 stored in the memory unit, the first acquiring step S10 is performed when the adjusting step S40 is performed. If the first acquiring step S10 is performed by measuring and acquiring the thickness of the first region 7, the adjusting step S40 is performed after the first acquiring step S10.

[0145] Then, in an adjusting step S40, the thickness of the second region 9 acquired in the second acquiring step S30 and stored in the memory unit of the controller 90 is read from the memory unit. The controller 90 calculates the total thickness of the workpiece 1 from the read thickness of the first region 7 and the thickness of the second region 9. More specifically, a thickness distribution specifying unit 94 of the controller 90 adds up the thickness of the first region 7 and the thickness of the second region 9 at each location of the workpiece 1 to calculate the total thickness at each location of the workpiece 1. This allows the thickness distribution of the workpiece 1 to be obtained.

[0146] In the adjustment step S40, the positional relationship adjustment unit 96 of the controller 90 then calculates the adjustment amount for adjusting the positional relationship between the second grinding wheel (machining tool) 18b and the holding table 8 based on the total thickness (thickness distribution) of each part of the workpiece 1.

[0147] For example, the positional relationship adjustment unit 96 calculates the bias a (amount of convexity) and bias m (amount of gulls) described in Figures 5(A) and 5(B) from the total thickness (thickness distribution) of each location of the workpiece 1. Then, the positional relationship adjustment unit 96 derives an adjustment amount so that the bias a (amount of convexity) and bias m (amount of gulls) approach zero after the thinning process (second processing step S50) that is subsequently performed.

[0148] For example, the controller 90 derives the amount of adjustment required for the tilt of the table rotation axis 58 and calculates the amount of adjustment for the lengths of the adjustment axes 62, 64. Then, the positional relationship adjustment unit 96 of the controller 90 adjusts the lengths of the adjustment axes 62, 64 based on the calculated amount of adjustment, thereby adjusting the tilt of the table rotation axis 58.

[0149] Alternatively, in the adjusting step S40, an adjustment amount for the tilt of the spindle 14b of the second grinding unit 10b (tilt of the rotation axis of the machining tool) may be calculated instead of or in addition to the tilt of the table rotation axis 58 (the length of the adjustment axes 62, 64). Furthermore, in the adjusting step S40, an adjustment amount for the relative position between the second grinding wheel (machining tool) 18b and the holding table 8 in a direction parallel to the holding surface 8a of the holding table 8 may be calculated.

[0150] The positional relationship between the second grinding wheel (machining tool) 18b and the holding table 8, for which the adjustment amount is calculated in the adjusting step S40, refers to some or all of these elements. Then, in the adjusting step S40, the positional relationship between the second grinding wheel (machining tool) 18b and the holding table 8 is adjusted according to the calculated adjustment amount of the positional relationship.

[0151] As described above, in the method for processing a workpiece according to this embodiment, the total thickness of the workpiece 1 can be calculated by using the thickness of the first region 7 measured before thinning the workpiece 1 and the thickness of the second region 9 measured after thinning the workpiece 1. Therefore, even in a processing device (grinding device 2) equipped with a thickness gauge (second thickness gauge 42) that is not suitable for measuring the thickness of the first region 7, the total thickness of the workpiece 1 can be derived using this thickness gauge, and the positional relationship of processing tools, etc. can be adjusted based on this total thickness.

[0152] In other words, even if the workpiece 1 has layers and regions whose thickness is difficult to measure using a thickness gauge provided in the processing device that performs the thinning process, this thickness gauge can be used to derive the total thickness of the workpiece 1. Therefore, the workpiece 1 can be thinned to a predetermined shape while making adjustments based on this total thickness.

[0153] In the method for processing a workpiece according to this embodiment, a second processing step S50 is performed after the adjustment step S40. In the second processing step S50, with the positional relationship between the second grinding wheel (processing tool) 18b and the holding table 8 adjusted, the second grinding wheel (processing tool) 18b is brought into contact with the workpiece 1 held on the holding table 8 to perform thinning processing.

[0154] The second processing step S50 is performed in the same manner as the first processing step S20, except that the positional relationship between the second grinding wheel (processing tool) 18b and the holding table 8 is adjusted. Then, when the workpiece 1 reaches a predetermined thickness, the thinning processing of the workpiece 1 by the second grinding wheel 18b is completed.

[0155] The above-described method for processing a workpiece will now be summarized. Fig. 9(A) is a cross-sectional view schematically showing the workpiece 1 before processing. In the method for processing a workpiece according to this embodiment, a second grinding wheel (processing tool) 18b is brought into contact with the workpiece 1 held on the holding table 8 to thin the workpiece 1 (first processing step S20).

[0156] 9(B) is a cross-sectional view schematically showing the workpiece 1 thinned in the first processing step S20. In the method for processing a workpiece according to this embodiment, the positional relationship between the second grinding wheel 18b and the holding table 8 is then adjusted with reference to the total thickness of the workpiece 1 (adjustment step S40). Then, in the second processing step S50, the workpiece 1 is further thinned in a state in which the positional relationship between the second grinding wheel 18b and the holding table 8 has been adjusted.

[0157] Here, the total thickness of the workpiece 1, which is referred to when adjusting the positional relationship between the second grinding wheel 18b and the holding table 8, includes the thickness of the first region 7 and the thickness of the second region 9 of the workpiece 1. The thickness of the second region 9 is obtained in a second acquisition step S30 by measuring the workpiece 1 that has been thinned in the first processing step S20. On the other hand, the thickness of the first region 7 is obtained in a first acquisition step S10 that is separate from the second acquisition step S30. That is, the thickness of the first region 7 and the thickness of the second region 9 are obtained separately.

[0158] Therefore, even if the thickness of the first region 7 cannot be obtained by measurement after the first processing step S20, the total thickness of the workpiece 1 can be referenced when adjusting the positional relationship between the second grinding wheel (processing tool) 18b and the holding table 8. In other words, position adjustment can be performed so that the workpiece 1 can be subsequently thinned to a predetermined shape.

[0159] After the positional relationship between the second grinding wheel (machining tool) 18b and the holding table 8 is adjusted, the workpiece 1 is further thinned to a predetermined shape (second machining step S50). FIG. 9(C) is a cross-sectional view that schematically shows the workpiece 1 that has been thinned to a predetermined thickness. For example, even if it is not easy to measure the thickness of the first region 7, the workpiece 1 can be thinned to a uniform thickness over the entire area of ​​the workpiece 1, as shown in FIG. 9(C).

[0160] Here, in the method for processing a workpiece according to this embodiment, depending on the calculated total thickness (thickness distribution) of the workpiece 1, there may be cases where it is not necessary to adjust the positional relationship between the second grinding wheel (processing tool) 18b and the holding table 8 in the adjustment step S40. That is, there may be cases where the adjustment amount is calculated to be zero. Even in this case, there is an advantage in that it is confirmed that the workpiece 1 can be processed with high precision without adjusting the positional relationship. Therefore, the adjustment step S40 includes cases where the positional relationship is adjusted with the adjustment amount set to zero.

[0161] The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above-described embodiment, the second acquisition step S30 is performed after the first processing step S20, with the second grinding wheel (processing tool) 18b retracted from above the workpiece 1. However, one aspect of the present invention is not limited to this.

[0162] In the method for processing a workpiece according to one aspect of the present invention, the second obtaining step S30 may be performed during the first processing step S20. Alternatively, when the second obtaining step S30 is performed after the first processing step S20, the second obtaining step S30 may be performed with the second grinding wheel (processing tool) 18b in contact with the workpiece 1.

[0163] In these cases, the second grinding wheel 20b is in contact with the center of the back surface 1b (work surface) of the workpiece 1, and this center is not exposed, so the measuring unit 42a cannot access this center. In other words, the thickness of the second region 9 at the center of the workpiece 1 cannot be measured by the second thickness measuring device 42. Therefore, if multiple representative examples of the cross-sectional shape of the workpiece 1 are stored in advance in the controller 90, etc., the thickness at the center of the workpiece 1 can be predicted based on the cross-sectional shapes of the parts other than the center of the workpiece 1 obtained by measurement.

[0164] For example, referring to the plan view of Fig. 8, the thickness of the second region 9 is not measured at position 13 near the center of the workpiece 1, but is measured at positions other than position 13. More specifically, the thickness of the second region 9 is measured at position 13 that is half the diameter of the workpiece 1 from the center of the workpiece 1, and at position 13 near the outer periphery of the workpiece 1.

[0165] Thereafter, the cross-sectional shape of the workpiece 1 other than the central part obtained by the measurement is compared with each representative example stored in the controller 90, and the representative example that is closest to this cross-sectional shape is selected. Then, based on the selected representative example, the thickness distribution over the entire area of ​​the workpiece 1 is predicted, and the inclination of the table rotation axis 58, etc. are adjusted in adjustment step S40.

[0166] In this way, when the thickness of the second region 9 is not measured at the center of the workpiece 1, the second acquisition step S30 can be performed during the first processing step S20. Alternatively, the second acquisition step S30 can be performed after the first processing step S20 with the second grinding wheel (processing tool) 18b in contact with the workpiece 1.

[0167] Furthermore, in the above embodiment, the case where the first acquisition step S10 is performed before the first processing step S20 has been mainly described, but the method for processing a workpiece according to one aspect of the present invention is not limited to this. That is, if the thickness of the first region 7 is acquired in the first acquisition step S10 by reading out the thickness of the first region 7 stored in advance in the memory unit of the controller 90, the first acquisition step S10 may be performed after the first processing step S20 and before the adjustment step S40.

[0168] 10(B) is a flowchart showing the flow of a method for processing a workpiece according to one aspect of the present invention, in which the first acquisition step S10 is performed after the first processing step S20. The thickness of the first region 7 acquired in the first acquisition step S10 is used in the adjustment step S40. Therefore, the first acquisition step S10 only needs to be completed before the adjustment step S40 is performed.

[0169] Furthermore, in the above embodiment, the thickness of the first region 7 of the workpiece 1 acquired in the first acquisition step S10 is obtained by measuring the workpiece 1 to be thinned in the first processing step S20, etc. However, the workpiece processing method according to one aspect of the present invention is not limited to this. For example, when the workpiece processing method according to one aspect of the present invention is repeatedly performed to thin multiple workpieces 1, it is not necessary to measure the thickness of the first region 7 for all of the workpieces 1.

[0170] That is, if the quality of a plurality of workpieces 1 is stable and the thickness of the first region 7 is similar for all workpieces 1, the thickness of the first region 7 may be acquired by measurement in the first acquisition step S10 only for the workpiece 1 that is processed first. Then, the thickness of the first region 7 acquired by measurement may be stored in the memory unit of the controller 90.

[0171] When the workpiece processing method according to one aspect of the present invention is performed on the second or subsequent workpiece 1, the first acquisition step S10 may acquire the thickness of the first region 7 of the workpiece 1 to be processed first, which is stored in the memory unit of the controller 90. In this case, the number of measurements required to acquire the thickness of the first region 7 of the workpiece 1 is minimized, allowing multiple workpieces 1 to be processed efficiently.

[0172] In this way, the thickness of the first region 7 of the workpiece 1 acquired in the first acquisition step S10 does not have to be derived from measurements performed on the workpiece 1 that is the target of thinning processing in the first processing step S20, etc.

[0173] The structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0174] 1 Workpiece 1a surface 1b back side 3 Protective materials 5 Workpiece 7 First area 9 Second area 11 chips 13 positions 15 Annular Region 2 Grinding equipment 4 Foundation 6. Turntable 8 Holding table 8a Holding surface 8b Frame 8c Porous material 10a, 10b Grinding unit 12a, 12b Spindle motor 14a, 14b Spindle 16a, 16b Wheel mount 18a, 18b Grinding wheels 20a, 20b Grinding wheel 20c circular orbit 22a, 22b Column 24a, 24b Lifting mechanism 24c guide rail 26a, 26b Cassette placing table 28a, 28b cassette 30 Wafer transport robot 32 Positioning table 34 Loading Arm 36 Unloading Arm 38 Spinner cleaning device 40,42 Thickness measuring instrument 42a Measuring part 42b Shaft 42c arm 44 Ball screw 46 Nut part 48 Pulse motor 50 Lifting Plate 54 Bottom 56 Rotational drive source 58 Table rotation axis 60 Fixed axis 62,64 Adjustment axis 66 Outer circumference 68 center 70 perimeter 72 Grinding Area 74 1st axis 76 2nd axis 90 Controller 92 Grinding control section 94 Thickness distribution specification section 96 Positional adjustment section 100,100a Thickness measurement unit 102,102a Support part 104 Measuring section 106 Top surface 108 Support 110 Arm 112 Probe Unit 114 Arm 116 Probe Unit 118,120 probes 122,122a Measuring head

Claims

1. A processing method for thinning a workpiece having a first region and a second region stacked thereon, comprising: a first acquisition step of acquiring a thickness of the first region; a first processing step of bringing a processing tool into contact with the workpiece held on a holding table to thin the second region; a second obtaining step of measuring and obtaining a thickness of the second region of the workpiece thinned in the first processing step; an adjusting step of adjusting a positional relationship between the machining tool and the holding table by referring to a total thickness of the workpiece including the thickness of the first region acquired in the first acquiring step and the thickness of the second region acquired in the second acquiring step; a second processing step in which, with the positional relationship between the processing tool and the holding table adjusted, the processing tool is brought into contact with the workpiece held on the holding table to perform thinning processing.

2. The method for processing a workpiece according to claim 1, characterized in that in the second acquisition step, the thickness of the second region of the workpiece is measured using a thickness measuring device that performs thickness measurements without contacting the workpiece.

3. In the second obtaining step, a thickness of the second region of the workpiece is measured by a thickness measuring device that performs thickness measurement using light or ultrasonic waves without contacting the workpiece; 2. The method for processing a workpiece according to claim 1, wherein the second region of the workpiece is more transparent to the light or ultrasonic waves used by the thickness gauge than the first region of the workpiece.

4. In the first obtaining step, thicknesses of the first region are obtained at a position that is a first distance away from a center of the workpiece and at a position that is a second distance away from the center of the workpiece, the second distance being different from the first distance; 3. The method for processing a workpiece according to claim 1, wherein the second acquisition step acquires the thickness of the second region at a position that is the first distance away from the center of the workpiece and at a position that is the second distance away from the center of the workpiece.

5. 3. The method for processing a workpiece according to claim 1, wherein the second acquisition step is performed after the first processing step and before the second processing step, in a state where the processing tool is not in contact with the workpiece.

6. 3. The method for processing a workpiece according to claim 1, wherein the second acquisition step is performed while the first processing step is being performed or after the first processing step, with the processing tool in contact with the workpiece.

7. A method for processing a workpiece as described in claim 1 or claim 2, characterized in that the thickness of the first region acquired in the first acquisition step is calculated by subtracting the thickness of the second region from the total thickness of the workpiece.

8. 3. The method for machining a workpiece according to claim 1, wherein the first obtaining step is performed in a state where the workpiece is not held on the holding table.

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