Processing methods

Abstract

To flatness a protective member by grinding, and prevent adhesion of a bond material of a dressing board to a grindstone and a wafer.SOLUTION: A processing method of a protective member and a grindstone bonded to a front side of a wafer, includes: a rear side holding step of exposing the other surface side of the protective member in which one surface side is bonded to the front side by holding the rear side of the wafer with a chuck table; a flatness step of reducing a level of unevenness of the other surface side of the protective member by grinding the other surface side of the protective member with the grindstone after the rear side holding step; and a dressing step of dressing the grindstone by grinding the grindstone while bringing it in contact with the rear side of the wafer or a single crystal substrate formed by the same material with the single crystal substrate constructing the wafer, after the flatness step.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for processing a protective member and a grinding wheel attached to the front surface side of a wafer, and a method for processing a wafer, a protective member, and a grinding wheel for grinding the protective member.

Background Art

[0002] Electronic devices such as mobile phones and personal computers have device chips mounted thereon. When manufacturing device chips, for example, first, a plurality of devices such as ICs (Integrated Circuits) are formed on the front surface side of a disk-shaped wafer made of a semiconductor material such as silicon.

[0003] Next, the back surface side of the wafer is ground to thin it to a predetermined thickness, and then the ground wafer is cut and divided into individual devices. As a result, the wafer is divided into a plurality of device chips.

[0004] By the way, when grinding the back surface side of the wafer, usually, in order to reduce damage to the device, a resin protective member (protective tape) is attached to the front surface side of the wafer. Then, while the front surface side of the wafer is sucked and held by a chuck table, the back surface side of the wafer is ground (see, for example, Patent Document 1).

[0005] However, there are variations in the in-plane thickness of the protective member, and these variations in the in-plane thickness may affect the processing accuracy of the wafer in grinding (that is, the flatness of the wafer after grinding). In particular, when the finish thickness is relatively thin or when grinding a wafer provided with bumps on the front surface side, the influence of the variations in the in-plane thickness of the protective member becomes relatively large.

[0006] In addition, in a state where a protective member is attached to the front surface side of the wafer, irregularities caused by devices or the like provided on the front surface side of the wafer are also reflected on the protective member. When the back surface side of the wafer is ground in a state where the irregularities are reflected on the protective member, irregularities are formed on the back surface side of the wafer after grinding, so the processing accuracy decreases.

[0007] Therefore, a method has been proposed in which the protective member is polished before grinding the back side of the wafer (see, for example, Patent Document 2). In this method, the protective member attached to the front side of the wafer is polished to flatten the base film constituting the protective member, and then the back side of the wafer is ground.

[0008] In contrast, one possible approach is to use a grinding device to grind and flatten the protective material attached to the surface side of the wafer, then invert the wafer and hold the surface side with suction using a chuck table, and then grind the back side of the wafer.

[0009] However, when a protective component is ground with a grinding wheel, the wheel usually becomes clogged, making further grinding difficult. Therefore, after grinding the protective component and before grinding the back side of the wafer, it is necessary to use a dressing board to clear the clogging of the grinding wheel. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 61-141142 [Patent Document 2] Japanese Patent Publication No. 2005-19666 [Overview of the project] [Problems that the invention aims to solve]

[0011] However, dressing boards may have a bonding agent made of a different material than that of the grinding wheel. If a grinding wheel is dressed with a dressing board that has a bonding agent made of a different material than that of the grinding wheel, the bonding agent of the dressing board will adhere to the grinding wheel and the wafer.

[0012] This invention has been made in view of the aforementioned problems, and aims to flatten the protective member by grinding, and to prevent the bonding material of the dressing board from adhering to the grinding wheel and wafer. [Means for solving the problem]

[0013] According to one aspect of the present invention, a method for processing a protective member and a grinding wheel attached to the surface side of a wafer, comprising: a back-side holding step in which the back side of the wafer is held with a chuck table to expose the other side of the protective member, one side of which is attached to the surface side; a flattening step in which the other side of the protective member is ground with the grinding wheel after the back-side holding step to reduce the degree of unevenness on the other side of the protective member; and after the flattening step, On a single crystal substrate formed from the same material as the single crystal substrate constituting the wafer A processing method is provided which includes a dressing step of dressing the grinding wheel by bringing it into contact with the grinding wheel and grinding it.

[0014] Preferably, the grinding wheel has abrasive grains with an average particle size of 1 μm or more and 20 μm or less, and a vitrified bond, and the concentration of abrasive grains in the grinding wheel is 50 or more and 150 or less.

[0015] According to another aspect of the present invention, a method for processing a wafer, a protective member, and a grinding wheel for grinding the protective member, comprising: a bonding step of bonding one side of the protective member to the surface side of the wafer; a rough grinding step of performing rough grinding on the back side of the wafer with a first grinding wheel having a first grinding wheel; a finish grinding step of performing finish grinding on the back side of the wafer with a second grinding wheel having a second grinding wheel after the rough grinding step, wherein before the rough grinding step or before the finish grinding step, the back side of the wafer is held with a chuck table to expose the other side of the protective member; a flattening step of reducing the degree of unevenness on the other side of the protective member by grinding the other side of the protective member with a grinding wheel for grinding the protective member after the back side holding step; and after the flattening step, On a single crystal substrate formed from the same material as the single crystal substrate constituting the waferA processing method is provided which further includes a dressing step of dressing a grinding wheel for grinding a protective member by bringing the grinding wheel for grinding the protective member into contact with and grinding it.

Effects of the Invention

[0016] In the processing method according to one aspect of the present invention, after the flattening step of the protective member, the grinding wheel is dressed by bringing the grinding wheel into contact with and grinding the back side of the wafer or a single-crystal substrate formed of the same material as the single-crystal substrate constituting the wafer.

[0017] In this way, by dressing the grinding wheel without using a dressing board, it is possible to prevent the adhesion of the bonding material of the dressing board to the grinding wheel and the wafer, which becomes a problem when the bonding material of the dressing board is different from the bonding material of the grinding wheel.

Brief Description of the Drawings

[0018] [Figure 1] It is a flowchart of the processing method in the first embodiment. [Figure 2] It is a diagram showing the pasting step. [Figure 3] It is a diagram showing the back-side holding step. [Figure 4] It is a diagram showing the flattening step. [Figure 5] It is a diagram showing the inversion step. [Figure 6] It is a diagram showing the dressing step. [Figure 7] It is a flowchart of the processing method in the second embodiment. [Figure 8] It is a diagram showing the dressing step in the second embodiment. [Figure 9] It is a flowchart of the processing method in the third embodiment. [Figure 10] It is a top view showing an overview of the grinding apparatus used in the third embodiment. [Figure 11]Figure 11(A) is a side view showing a wafer unit placed on a temporary stand, Figure 11(B) is a side view showing a wafer unit whose back side is held in place by a suction mechanism, and Figure 11(C) is a side view showing a wafer unit being transported to a chuck table. [Figure 12] This diagram shows the rough grinding process. [Figure 13] This diagram shows the finishing grinding process. [Figure 14] This is a flowchart of the processing method in the fifth embodiment. [Modes for carrying out the invention]

[0019] An embodiment of one aspect of the present invention will be described with reference to the attached drawings. In the first embodiment, as shown in Figure 1, the bonding step S10, the back side holding step S20, the flattening step S30, the inversion step S40, and the dressing step S50 are performed in this order.

[0020] Figure 1 is a flowchart of the processing method in the first embodiment. The wafer 11 has, for example, a disc-shaped single-crystal substrate made of silicon (see Figure 2). Note that the material of the single-crystal substrate is not limited to silicon.

[0021] The single-crystal substrate constituting wafer 11 may be formed from other semiconductors or compound semiconductors such as SiC (silicon carbide) or GaN (gallium nitride). Wafer 11 may have, for example, a diameter of 200 mm (i.e., 8 inches) and a thickness of 725 μm, but the diameter and thickness are not limited to these numerical examples.

[0022] As shown in Figure 2, multiple division lines (stories) 13 are arranged in a grid pattern on the surface 11a side of the wafer 11. A device 15, such as an IC, is formed in each of the rectangular regions demarcated by the multiple division lines 13.

[0023] A metal bump (not shown) may also be provided on the device 15. When grinding the back surface 11b of the wafer 11, a resin protective member 17 is attached tightly to the surface 11a to protect the device 15 located on the front surface 11a.

[0024] The protective member 17 of this embodiment is a so-called protective tape and has a laminated structure of a base layer 17a and an adhesive layer (glue layer) 17b (see Figure 3). The base layer 17a is formed of, for example, polyolefin or polyethylene terephthalate, and the adhesive layer 17b is formed of, for example, epoxy, acrylic, or rubber-based adhesives.

[0025] The thickness of the base layer 17a is greater than the thickness of the adhesive layer 17b. For example, the base layer 17a has a thickness of 100 μm to 500 μm, and the adhesive layer 17b has a thickness of 5 μm to 200 μm.

[0026] The adhesive layer 17b of the protective member 17 may be a UV-curing resin that hardens and loses adhesive strength upon UV (ultraviolet) irradiation, or a thermosetting resin that hardens and loses adhesive strength upon heating. The protective member 17 may also have only a base layer 17a without the adhesive layer 17b.

[0027] The protective member 17 is attached to the surface 11a side by pressing with a roller, vacuum bonding, thermocompression bonding, or the like. In this embodiment, one side 17c of the protective member 17 that is exposed to the adhesive layer 17b side is attached to the surface 11a side of the wafer 11 (attachment step S10).

[0028] Figure 2 shows the bonding process S10. In the bonding process S10, for example, the back side 11b of the wafer 11 is held by suction using a disc-shaped chuck table (not shown), and one side 17c of a substantially square protective member 17, which has sides larger than the diameter of the wafer 11, is bonded to the front side 11a.

[0029] Subsequently, the protective member 17 is cut along the outer circumference of the wafer 11 with a cutting blade (not shown) to form a wafer unit 19 in which wafers 11 and protective members 17 of approximately the same diameter are stacked. Alternatively, the adhesive layer 17b side of the protective member 17, which has been formed in a circular shape beforehand, may be attached to the surface 11a side.

[0030] When one side 17c is attached to the surface 11a side, the other side 17d of the protective member 17, which is located opposite to the one side 17c, is exposed. After the attachment process S10, irregularities 17e are formed on the other side 17d of the protective member 17 (see Figure 3). These irregularities 17e are caused by irregularities on the surface 11a side of the wafer 11, or by variations in the in-plane thickness of the protective member 17 itself.

[0031] The degree of unevenness 17e on the other surface 17d, as shown in Figure 3, is evaluated using, for example, the arithmetic mean roughness (Ra), maximum height roughness (Rz), and root mean square roughness (Rq), as defined in JIS (Japanese Industrial Standards) B 0601:2013.

[0032] For example, the degree of unevenness 17e on the other surface 17d, as shown in Figure 3, is measured by the maximum height roughness (Rz), and is between 10 μm and 500 μm.

[0033] Furthermore, the thickness variation (i.e., TTV (total thickness variation)) on the back surface 11b side of the wafer 11, in accordance with SEMI standards (Semiconductor Equipment and Materials International standards), is 10 μm or less.

[0034] After the bonding process S10, the back surface 11b side of the wafer 11 is held by suction using the disc-shaped chuck table 4 provided in the grinding apparatus 2 (back surface holding process S20). Next, the configuration of the grinding apparatus 2 will be described.

[0035] The grinding apparatus 2 of this embodiment is a manual type in which the operator manually places the wafer 11 on the chuck table 4, removes the wafer 11 from the chuck table 4 (see Figure 3), and inverts the wafer 11.

[0036] Furthermore, the grinding device 2 of this embodiment is an infeed grinding method in which the grinding feed is performed by lowering the grinding unit 8 (see Figure 4) along the Z-axis direction. The Z-axis direction is, for example, parallel to the vertical direction.

[0037] The chuck table 4 has a disc-shaped frame made of non-porous ceramics. A disc-shaped recess (not shown) is formed on the upper surface of the frame. A disc-shaped porous plate (not shown) made of porous ceramics is fixed in the recess.

[0038] A suction source (not shown), such as a vacuum pump, is connected to the frame, and the negative pressure generated by the suction source can be transmitted to the porous plate. The upper surface of the porous plate and the upper surface of the frame are formed to be substantially flush, forming a holding surface 4a that holds the wafer unit 19 by suction.

[0039] The retaining surface 4a has a conical shape in which the central part protrudes slightly compared to the outer periphery, but the amount of protrusion is very small, for example, 20 μm, so in Figures 3 and later, the retaining surface 4a is shown as approximately flat.

[0040] A rotational drive source (not shown), such as a motor, is located below the chuck table 4. The torque from the rotational drive source is transmitted to the rotating shaft 6 of the chuck table 4 (see Figure 4) via pulleys, an endless belt (neither shown), etc. In Figure 4, the rotating shaft 6 is simplified and shown with a dashed line.

[0041] The rotating shaft 6 is tilted slightly in a predetermined direction by an angle adjustment mechanism (not shown) such that a portion of the holding surface 4a is approximately parallel to the grinding surface 14c of the grinding wheel 14. The chuck table 4 is configured to move along the Y-axis direction, which is perpendicular to the Z-axis direction, by a ball screw type Y-axis direction movement unit (not shown).

[0042] The Y-axis movement unit moves the chuck table 4 between the loading / unloading area A1 where wafers 11 are loaded and unloaded, and the grinding area A2 where the protective member 17 and wafers 11 are ground.

[0043] A grinding unit 8 is provided above the chuck table 4 located in the grinding area A2. The grinding unit 8 has a cylindrical spindle housing (not shown) whose longitudinal direction is aligned with the Z-axis direction.

[0044] A ball screw type grinding feed mechanism (not shown) is connected to the spindle housing, which moves the grinding unit 8 along the Z-axis. A portion of the cylindrical spindle 10 is rotatably held within the spindle housing.

[0045] The longitudinal direction of the spindle 10 is aligned with the Z-axis direction. A rotational drive source (not shown), such as a motor, is provided at the upper end of the spindle 10, and a disc-shaped mount 12 is fixed to the lower end of the spindle 10.

[0046] An annular grinding wheel 14 is mounted on the lower side of the mount 12. The grinding wheel 14 has an annular wheel base 14a made of a metal such as an aluminum alloy. The upper side of the wheel base 14a is fixed to the lower side of the mount 12.

[0047] On the underside of the wheel base 14a, multiple segmented grinding wheels (grinding wheels for grinding protective members) 14b are arranged in a ring shape along the circumferential direction of the wheel base 14a. When the spindle 10 is rotated, the trajectories of the undersides of the multiple grinding wheels 14b form an annular grinding surface 14c.

[0048] The grinding wheel 14b comprises abrasive grains formed from diamond, cBN (cubic boron nitride), etc., and a bonding material formed from vitrified bond or resin bond, etc., for fixing the abrasive grains. The grinding wheel 14b of this embodiment has abrasive grains with an average particle size of 1 μm or more and 20 μm or less, and a vitrified bond, and the concentration of abrasive grains is 50 or more and 150 or less.

[0049] If the average particle size of the abrasive grains on the grinding wheel 14b is smaller than 1 μm, grinding the protective member 17 with the grinding wheel 14b is prone to clogging, and the protective member 17 cannot be properly ground.

[0050] In contrast, if the average particle size of the abrasive grains of the grinding wheel 14b is greater than 20 μm, grinding the protective member 17 with the grinding wheel 14b will cause roughness on the ground surface of the protective member 17.

[0051] The roughness of the grinding surface of the protective member 17 is transferred to the back surface 11b as irregularities on the back surface 11b when the back surface 11b of the wafer 11 is ground after the dressing process S50 described later. Therefore, it is preferable that the average particle size of the abrasive grains of the grinding wheel 14b be 1 μm or more and 20 μm or less.

[0052] In this embodiment, the average particle size is defined by the particle diameter at which the cumulative height reaches 50% in the sedimentation test method (i.e., the median diameter or 50% diameter). Alternatively, the average particle size may be defined by the particle diameter with the highest frequency in the electrical resistance test method (i.e., the most frequent particle diameter or mode diameter).

[0053] The size of abrasive grains can also be expressed using the grit size specified in JIS R 6001-2:2017. For example, grinding wheel 14b uses abrasive grains with a grit size of #1000 as specified by the electrical resistance test method.

[0054] The concentration level refers to the volume of abrasive grains in the grinding wheel 14b. When the concentration level is 50, the volume of abrasive grains in the grinding wheel 14b is 12.5%, and when the concentration level is 100, the volume of abrasive grains in the grinding wheel 14b is 25%.

[0055] Furthermore, at a concentration of 150, the volume of abrasive grains in the grinding wheel 14b is 37.5%. Thus, the concentration in the grinding wheel 14b increases linearly in accordance with the increase in the volume of abrasive grains in the grinding wheel 14b.

[0056] Next, referring to Figures 3 to 6, the processing methods for the protective member 17 and the grinding wheel 14b from the bonding process S10 onward will be explained. Figure 3 shows the back side holding process S20. For the sake of explanation, Figure 3 shows the wafer unit 19 in cross-section.

[0057] In the back-side holding step S20, the back side 11b of the wafer 11 is held by suction using the holding surface 4a of the chuck table 4 located in the loading / unloading area A1, thereby exposing the other side 17d of the protective member 17. After the back-side holding step S20, the chuck table 4 is moved to the grinding area A2.

[0058] Then, while supplying grinding water (not shown), such as pure water, to the area to be ground and the grinding wheel 14b at a predetermined flow rate, the other side 17d of the protective member 17 is ground with the grinding wheel 14b to reduce the degree of unevenness 17e on the other side 17d (flattening step S30, see Figure 4).

[0059] In the planarization process S30, for example, grinding water is supplied to the machining point at a rate of 4 L / min from a nozzle (not shown) (so-called internal nozzle) positioned between the grinding wheel 14 and the holding surface 4a, and further, grinding water (so-called wheel grinding water) is supplied at a rate of 4 L / min from a plurality of nozzles (not shown) formed on the inner circumference side of the grinding wheel 14b along the circumferential direction of the wheel base 14a.

[0060] In addition to grinding water, the lower surface of the grinding wheels 14b may be cleaned by spraying grinding water onto one or more grinding wheels 14b located outside the chuck table 4 from below the grinding wheel 14 towards the grinding wheels 14b at a predetermined high pressure (e.g., 10 MPa) and predetermined flow rate (e.g., 4 L / min).

[0061] Figure 4 shows the planarization process S30. In Figure 4, the wafer unit 19 is shown in cross-section. In the planarization process S30, only the base material layer 17a of the protective member 17 is ground with the grinding wheel 14.

[0062] For example, the other side 17d of the protective member 17 is ground to a thickness of 5 μm or more and less than 500 μm, so that the degree of unevenness 17e on the other side 17d, as measured by the arithmetic mean roughness (Rz), is 10 μm or less. The processing conditions in the planarization process S30 are set as follows, for example.

[0063] Grinding feed rate: 0.3 μm / s Spindle rotation speed: 2500 rpm Chuck table rotation speed: 300 rpm Load current of the motor driving the spindle: 10A

[0064] After the planarization process S30, as shown in Figure 5, the chuck table 4 is returned to the loading / unloading area A1, and the operator manually inverts the wafer unit 19 upside down. Then, the other side 17d of the ground protective member 17 is held in place by suction at the holding surface 4a (inversion process S40).

[0065] Figure 5 shows the inversion process S40. In Figure 5, the wafer unit 19 held by suction on the holding surface 4a is shown in cross-section. After the inversion process S40, the wafer unit 19 is returned to the grinding area A2 as shown in Figure 6.

[0066] Then, the grinding wheel 14b is brought into contact with the back surface 11b of the wafer 11 and ground, thereby dressing the grinding wheel 14b (dressing step S50, see Figure 6). Grinding water is also supplied to the processing point during the dressing step S50.

[0067] For example, grinding water is supplied to the machining point at a rate of 4 L / min from an internal nozzle (not shown), and wheel grinding water is supplied to the machining point at a rate of 4 L / min from the wheel base 14a. Figure 6 shows the dressing process S50. The dressing conditions are set as follows, for example.

[0068] Grinding feed rate: 1.0 μm / s Spindle rotation speed: 1000 rpm Chuck table rotation speed: 300 rpm Load current of the motor driving the spindle: 13A

[0069] Incidentally, the dressing boards typically used to dress the grinding wheel 14b have abrasive grains such as white alundum (WA) and green carbon (GC) fixed to a bonding material such as vitrified bond or resin bond.

[0070] If the bonding material of the dressing board and the bonding material of the grinding wheel 14b are different materials, then when the grinding wheel 14b is dressed using the dressing board, the bonding material of the dressing board will adhere to the grinding wheel 14b.

[0071] However, in this embodiment, by applying a dressing to the grinding wheel 14b without using a dressing board, it is possible to prevent the adhesive material of the dressing board from adhering to the grinding wheel 14b, which becomes a problem when the adhesive material of the dressing board and the adhesive material of the grinding wheel 14b are different.

[0072] Furthermore, when grinding the wafer 11 with the dressing wheel 14b, it is possible to prevent the bonding material of the dressing board, which is different from the bonding material of the grinding wheel 14b, from adhering to the wafer 11.

[0073] In this way, contamination of the grinding wheel 14b and wafer 11 by different types of bonding materials can be prevented. Furthermore, contamination of the grinding wheel 14b and wafer 11 by different types of abrasive grains can also be prevented.

[0074] In addition, since dressing can be performed simply by inverting the wafer unit 19 in the inversion process S40, a dressing board is unnecessary. Furthermore, there is the added advantage of eliminating the need for transporting and managing the dressing board.

[0075] Furthermore, in the dressing process S50, in addition to dressing the grinding wheel 14b, the back surface 11b of the wafer 11 can be ground to thin the wafer 11. In other words, dressing and grinding of the wafer 11 can be performed together.

[0076] (Second Embodiment) Next, a second embodiment will be described. Figure 7 is a flowchart of the processing method in the second embodiment. In the second embodiment, a dummy wafer 21 is used instead of wafer 11 in the dressing process S50 (see Figure 8).

[0077] The dummy wafer 21 is a single-crystal substrate formed from the same semiconductor material (i.e., the same material) as the single-crystal substrate constituting the wafer 11, and the device 15 is not formed on it. In this embodiment, being formed from the same semiconductor material (i.e., the same material) means that the main components are the same material.

[0078] Since the wafer 11 of this embodiment has a silicon single crystal substrate, a silicon single crystal substrate having the same main component (i.e., silicon) is used as the dummy wafer 21.

[0079] Incidentally, the dummy wafer 21 may be a mirror wafer in which at least one of its two sides, one side 21a and the other side 21b located opposite to side 21a, is mirror-finished.

[0080] In the second embodiment, since the dressing process S50 is performed using a dummy wafer 21, instead of the inversion process S40, a replacement process S42 is performed in which the wafer unit 19 placed in the loading / unloading area A1 is replaced with a dummy wafer 21 having approximately the same diameter as the wafer 11.

[0081] In the replacement process S42, one side 21a of the dummy wafer 21 is held in place by suction on the holding surface 4a. After the replacement process S42, the grinding wheel 14b is brought into contact with the other side 21b of the dummy wafer 21 and ground, thereby dressing the grinding wheel 14b.

[0082] Figure 8 shows the dressing process S50 in the second embodiment. In Figure 8, the dummy wafer 21 held by suction on the holding surface 4a is also shown in a cross-sectional view.

[0083] In the second embodiment as well, it is possible to prevent the bonding material of the dressing board from adhering to the grinding wheel 14b. Furthermore, during grinding of the wafer 11 after dressing, it is also possible to prevent the bonding material of the dressing board, which is different from the bonding material of the grinding wheel 14b, from adhering to the wafer 11.

[0084] (Third Embodiment) Next, a third embodiment will be described. Figure 9 is a flowchart of the processing method in the third embodiment. In the third embodiment, an automatic type grinding device 20 is used in which a transport robot 30 or the like automatically transports and inverts the wafer 11, and which uses an infeed grinding method (see Figure 10).

[0085] Figure 10 is a top view showing an overview of the grinding apparatus 20 used in the third embodiment. Note that the X-axis, Y-axis, and Z-axis directions shown in Figure 10 are orthogonal to each other. For example, the X-Y plane is approximately parallel to the horizontal plane, and the Z-axis direction is parallel to the vertical direction.

[0086] The grinding apparatus 20 has a rectangular base 24 when viewed from above. Cassette mounting tables 26a and 26b are provided on the front side (one side in the Y-axis direction) of the base 24, along the X-axis direction. Cassette mounting tables 26a each have cassettes 28a containing multiple wafer units 19 before grinding.

[0087] Furthermore, cassettes 28b for housing multiple wafer units 19 after grinding are placed on each cassette mounting table 26b. A transport robot 30 is provided behind the cassette mounting tables 26a and 26b (on the other side in the Y-axis direction).

[0088] The base of the transport robot 30 is configured to be movable along the X-axis and Z-axis directions. A multi-bar link structure is provided on the base. A wrist section 30b is provided at the tip of the uppermost link.

[0089] The wrist portion 30b is provided with a hand portion 30a capable of non-contact suction and holding of the wafer unit 19. Multiple Bernoulli chucks (also called Bernoulli pads) are provided on one surface of the hand portion 30a, and this surface functions as a suction surface 30a1 (see Figure 11(B)) for suction and holding of the wafer unit 19.

[0090] The hand portion 30a is rotated around a predetermined axis of rotation by a rotational drive source (not shown) located within the wrist portion 30b. In other words, the suction surface 30a1 of the hand portion 30a is inverted vertically.

[0091] A disc-shaped temporary support platform 30c is provided on one side of the base 24 in the X-axis direction (the left side in Figure 10). In a top view, the diameter of the temporary support platform 30c is smaller than the gap 30a2 provided in the hand portion 30a. The temporary support platform 30c is used, for example, when inverting the wafer unit 19 or when aligning the wafer unit 19.

[0092] The transport robot 30 accesses cassettes 28a and 28b, as well as a disc-shaped turntable 32 located on the rear side of the base 24. The turntable 32 can rotate both clockwise and counterclockwise when viewed from above.

[0093] The upper surface of the turntable 32 is divided into four fan-shaped regions (loading / unloading region B1, protective member grinding region B2, rough grinding region B3, and finish grinding region B4), each with a central angle of approximately 90 degrees, and a disc-shaped chuck table 34 is provided in each region.

[0094] The structure of each chuck table 34 is substantially the same as that of chuck table 4. In each chuck table 34, the upper surface of the porous plate and the upper surface of the frame function as holding surfaces 34a that suction and hold the wafer unit 19.

[0095] Each chuck table 34 is rotatable around a predetermined axis of rotation (not shown), similar to the rotation axis 6 of the chuck table 4. Above the protective member grinding area B2, a protective member grinding unit 36 ​​is provided for grinding the protective member 17.

[0096] The configuration of the protective member grinding unit 36 ​​is the same as that of the grinding unit 8 used in the flattening process S30 of the protective member 17. The grinding wheel 14 described above is attached to the lower end of the spindle (not shown) of the protective member grinding unit 36.

[0097] A rough grinding unit 38 is provided above the rough grinding area B3. The configuration of the rough grinding unit 38 is the same as that of the grinding unit 8. However, a rough grinding wheel (first grinding wheel) 44 is mounted on the lower end of the spindle 40 of the rough grinding unit 38 via a mount 42 (see Figure 12).

[0098] The rough grinding wheel 44 has an annular wheel base 44a made of a metal such as an aluminum alloy. The upper side of the wheel base 44a is fixed to the lower side of the mount 42.

[0099] On the lower surface of the wheel base 44a, multiple segmented rough grinding wheels (first grinding wheels) 44b are arranged in an annular pattern along the circumferential direction of the wheel base 44a. When the spindle 40 is rotated, an annular grinding surface 44c is formed by the trajectories of the lower surfaces of the multiple rough grinding wheels 44b.

[0100] The coarse grinding wheel 44b comprises abrasive grains formed from diamond, cBN (cubic boron nitride), etc., and a bonding material formed from vitrified bond or resin bond, etc., for fixing the abrasive grains.

[0101] The coarse grinding wheel 44b in this embodiment has abrasive grains with an average particle size larger than that of the grinding wheel 14b used to grind the protective member 17. For example, the coarse grinding wheel 44b uses abrasive grains with a grit size of #400, #500, or #600 as specified in the electrical resistance test method of JIS R 6001-2:2017.

[0102] A finishing grinding unit 48 is provided above the finishing grinding area B4. The configuration of the finishing grinding unit 48 is the same as that of the grinding unit 8. However, a finishing grinding wheel (second grinding wheel) 54 is mounted on the lower end of the spindle 50 of the finishing grinding unit 48 via a mount 52 (see Figure 13).

[0103] The finishing grinding wheel 54 has an annular wheel base 54a made of a metal such as an aluminum alloy. The upper side of the wheel base 54a is fixed to the lower side of the mount 52.

[0104] On the underside of the wheel base 54a, multiple segmented finishing grinding wheels (second grinding wheels) 54b are arranged in an annular pattern along the circumferential direction of the wheel base 54a. When the spindle 50 is rotated, the trajectories of the undersides of the multiple finishing grinding wheels 54b form an annular grinding surface 54c.

[0105] The finishing grinding wheel 54b comprises abrasive grains formed from diamond, cBN (cubic boron nitride), etc., and a bonding material formed from vitrified bond or resin bond, etc., for fixing the abrasive grains. In this embodiment, the finishing grinding wheel 54b has abrasive grains with an average particle size less than or equal to the average particle size of the grinding wheel 14b that grinds the protective member 17.

[0106] For example, the finishing grinding wheel 54b uses abrasive grains with a grit size of #6000 or #8000 as specified in the electrical resistance test method of JIS R 6001-2:2017. In one preferred embodiment, the finishing grinding wheel 54b has an average particle size of 1 μm or less.

[0107] A spinner cleaning device 60 is provided on the front side of the temporary storage table 30c. After processing, the wafer unit 19 is transported from the chuck table 34 located in the loading / unloading area B1 to the spinner cleaning device 60 by a transport unit 62 provided on one side of the base 24 in the X-axis direction.

[0108] For the sake of clarity, the transport unit 62 is shown with a dashed line in Figure 10. The transport pad 62a, which holds the wafer unit 19 by suction, is configured to be movable along the X-axis, Y-axis, and Z-axis directions.

[0109] The wafer 11, cleaned in the spinner cleaning device 60, is transported from the spinner cleaning device 60 to the cassette 28b by the transport robot 30. Next, the processing method for the wafer 11, protective member 17, and grinding wheel 14b will be explained with reference to Figure 9.

[0110] The wafer unit 19 formed through the bonding process S10 is housed in the cassette 28a. The transport robot 30 accesses the cassette 28a, holds the wafer unit 19 by suction on the side with the protective member 17, and transports it to the chuck table 34 located in the loading / unloading area B1.

[0111] The wafer unit 19 is transported to the chuck table 34 located in the loading / unloading area B1 so that the back surface 11b of the wafer 11 is in contact with the holding surface 34a, after which the back surface 11b is held by suction (back surface holding step S20). At this time, the other surface 17d of the protective member 17 is exposed upward.

[0112] After the back side holding step S20, the turntable 32 is rotated 90 degrees clockwise when viewed from above. Then, the planarization step S30 described above is performed using the protective member grinding unit 36. After the planarization step S30, the inversion step S40 is performed to invert the wafer unit 19 upside down.

[0113] In the inversion process S40, first, the turntable 32 is rotated 90 degrees counterclockwise when viewed from above, thereby returning the chuck table 34, which is holding the wafer unit 19 after the planarization process S30, to the loading / unloading area B1.

[0114] Then, the transport unit 62 suction-holds the wafer unit 19 on the side with the protective member 17 and transports it from the chuck table 34 located in the loading / unloading area B1 to the temporary storage table 30c. Figure 11(A) is a side view showing the wafer unit 19 placed on the temporary storage table 30c.

[0115] As shown in Figure 11(A), the wafer unit 19 is placed on the temporary stand 30c so that the flattened other surface 17d is exposed upwards. Next, as shown in Figure 11(B), the hand unit 30a, which has been adjusted to face upwards, is placed below the wafer unit 19.

[0116] Then, the back surface 11b of the wafer 11 is held in place by suction using the suction surface 30a1. Figure 11(B) is a side view showing the wafer unit 19 with its back surface 11b held in place by the hand part 30a. The hand part 30a moves upward while holding the wafer unit 19 in place by suction, and also inverts the wafer unit 19 vertically.

[0117] Then, as shown in Figure 11(C), the transport robot 30 transports the wafer unit 19 to the chuck table 34 located in the loading / unloading area B1. Figure 11(C) is a side view showing the wafer unit 19 being transported to the chuck table 34 located in the loading / unloading area B1.

[0118] Note that the inversion step S40 described above is just one example. For example, in the inversion step S40, a dedicated inversion mechanism (not shown) may be used to hold the wafer unit 19 on the chuck table 34 located in the loading / unloading area B1 and invert it vertically.

[0119] In any case, after the inversion process S40 is completed, the wafer unit 19 is held by suction on the surface 11a side of the wafer 11 via the protective member 17 (surface side holding process S44).

[0120] After the surface-side holding step S44, the turntable 32 is rotated 90 degrees clockwise in a top view to position the chuck table 34 directly below the protective member grinding unit 36 ​​(protective member grinding area B2). Then, the dressing step S50 is performed in the same manner as in the first embodiment.

[0121] In the dressing process S50 of this embodiment, the dressing is applied to the grinding wheel 14b of the protective member grinding unit 36 ​​on the back surface 11b side of the wafer 11, thus preventing the bonding material of the dressing board from adhering to the grinding wheel 14b or the wafer 11. In addition, there is the advantage that a dressing board is not required.

[0122] After the dressing process S50, the turntable 32 is rotated 90 degrees clockwise in a top view, and the chuck table 34 is positioned directly below the rough grinding unit 38 (rough grinding area B3).

[0123] Then, while supplying grinding water such as pure water to the area to be ground and the rough grinding wheel 44b at a predetermined flow rate, rough grinding is performed on the back surface 11b side of the wafer 11 with the rough grinding wheel 44 (rough grinding step S60). Figure 12 is a diagram showing the rough grinding step S60. The processing conditions in the rough grinding step S60 are set, for example, as follows.

[0124] Grinding feed rate: 1 μm / s to 10 μm / s Spindle rotation speed: 1000 rpm to 3500 rpm Chuck table rotation speed: 10 rpm to 500 rpm Load current of the motor driving the spindle: 6A to 20A

[0125] After the rough grinding process S60, the turntable 32 is rotated 90 degrees clockwise in a top view, and the chuck table 34 is positioned directly below the finish grinding unit 48 (finish grinding area B4).

[0126] Then, while supplying grinding water such as pure water to the area to be ground and the finish grinding wheel 54b at a predetermined flow rate, the finish grinding wheel 54 performs finish grinding on the back surface 11b side of the wafer 11 (finish grinding step S70). Figure 13 is a diagram showing the finish grinding step S70. The processing conditions in the finish grinding step S70 are set, for example, as follows.

[0127] Grinding feed rate: 0.5 μm / s Spindle rotation speed: 3000 rpm Chuck table rotation speed: 300 rpm Load current of the motor driving the spindle: 10A

[0128] After the rough grinding process S60 and the finish grinding process S70, the wafer 11 is thinned to a predetermined thickness (for example, 100 μm). After the finish grinding process S70, the turntable 32 is rotated 270 degrees counterclockwise in a top view and returned to the loading / unloading area B1.

[0129] Then, the transport unit 62 transports the thinned wafer unit 19 to the spinner cleaning device 60. After cleaning in the spinner cleaning device 60, the transport robot 30 transports the wafer unit 19, whose back surface 11b side has been cleaned, to the cassette 28b.

[0130] In the third embodiment, the planarization step S30 of the protective member 17 can be performed before the rough grinding step S60, so that in the rough grinding step S60, the other side 17d of the substantially flattened protective member 17 can be held by suction with the chuck table 34.

[0131] This improves the flatness of the back surface 11b compared to when the planarization process S30 is performed after the rough grinding process S60 and before the finish grinding process S70. Furthermore, since the back surface 11b is ground with the grinding wheel 14b in the dressing process S50 after the planarization process S30, the volume of the wafer 11 to be ground in the rough grinding process S60 and the finish grinding process S70 can be reduced.

[0132] By the way, if the flattening process S30 is performed after the rough grinding process S60 and before the finish grinding process S70, two reversal processes are required. However, in the third embodiment, there is the advantage that only one reversal process is required.

[0133] (Fourth Embodiment) Next, a fourth embodiment will be described. In the fourth embodiment, a dummy wafer 21 is used in the dressing process S50, similar to the second embodiment. The dummy wafer 21 is placed on a chuck table 34 different from the wafer unit 19.

[0134] This allows the dressing process S50 to be performed using the dummy wafer 21 during the inversion process S40 of the wafer unit 19, during the rough grinding process S60 or finish grinding process S70 of the wafer 11, or during the spinner cleaning of the wafer 11. The dummy wafer 21 may be continuously held by suction on any chuck table 34 until it reaches its usable thickness limit.

[0135] (Fifth Embodiment) Next, a fifth embodiment will be described. Figure 14 is a flowchart of the processing method in the fifth embodiment. In the fifth embodiment, similar to the third embodiment, the dressing process S50 is performed using the back surface 11b side of the wafer 11.

[0136] However, the fifth embodiment differs from the third embodiment in that the backside holding process S28, the flattening process S30, the dressing process S50, etc. are performed after the rough grinding process S24 and before the finish grinding process S70.

[0137] As shown in Figure 14, after the bonding process S10, the wafer unit 19 is held by suction on the surface 11a side via the protective member 17 at the chuck table 34 located in the loading / unloading area B1 (surface side holding process S22).

[0138] After the surface side holding step S22, rough grinding is performed on the back side 11b (rough grinding step S24). After the rough grinding step S24, for example, the wafer unit 19 is inverted upside down using the transport robot 30, temporary stand 30c and transport unit 62 (inversion step S26).

[0139] Next, the back surface 11b is held by suction using a chuck table 34 located in the loading / unloading area B1 (back surface holding step S28). After that, the degree of unevenness 17e on the other surface 17d of the exposed protective member 17 is reduced (flattening step S30).

[0140] After the planarization process S30, the wafer goes through the inversion process S40 again, and the surface 11a side of the wafer 11 is held by suction via the protective member 17 on the chuck table 34 located in the loading / unloading area B1 (surface side holding process S44).

[0141] After the surface holding step S44, the dressing step S50 using the protective member grinding unit 36 ​​and the finish grinding step S70 using the finish grinding unit 48 are performed sequentially.

[0142] In the fifth embodiment as well, it is possible to prevent the bonding material of the dressing board from adhering to the grinding wheel 14b or the wafer 11. In the fifth embodiment as well, a dummy wafer 21 can be used.

[0143] By the way, in the third to fifth embodiments described above, an example was given in which a grinding device 20 having three grinding units (a so-called three-axis type) is used. However, a grinding device having two grinding units (a so-called two-axis type) may also be used.

[0144] In this case, the finish grinding unit 48 is omitted, and the flattening step S30 and the finish grinding step S70 are performed using the protective member grinding unit 36, which is used for flattening the protective member 17. Furthermore, the structure, method, etc. of the above embodiment can be modified as appropriate without departing from the scope of the object of the present invention.

[0145] For example, the embodiments described above are not limited to wafers 11 having devices 15, etc. One side 17c of the protective member 17 may be attached to the surface 11a of a wafer 11 that does not have devices 15, etc., and the other side 17d of the protective member 17 may be ground down to reduce the degree of unevenness 17e on the other side 17d.

[0146] This allows, for example, the degree of irregularities 17e on the other surface 17d, which are between 3 μm and 6 μm in size, to be reduced to 1 μm or less. By flattening the protective member 17 in this way, it leads to improved processing accuracy in subsequent processes such as grinding. [Explanation of symbols]

[0147] 2: Grinding device, 4: Chuck table, 4a: Holding surface 6: Rotating shaft, 8: Grinding unit, 10: Spindle, 12: Mount 11: Wafer, 11a: Front side, 11b: Back side, 13: Planned division line, 15: Device 14: Grinding wheel, 14a: Wheel base 14b: Grinding wheel (grinding wheel for grinding protective components), 14c: Grinding surface 17: Protective material, 17a: Base material layer, 17b: Adhesive layer 17c: one side, 17d: the other side, 17e: uneven surface, 19: wafer unit 20: Grinding device, 24: Base 21: Dummy wafer, 21a: One side, 21b: Other side 26a, 26b: Cassette mounting tray, 28a, 28b: Cassette 30: Transport robot, 30a: Hand unit 30a1: Suction surface, 30a2: Gap, 30b: Wrist area, 30c: Temporary stand 32: Turntable, 34: Chuck table, 34a: Holding surface 36: Protective component grinding unit 38: Rough grinding unit, 40: Spindle, 42: Mount 44: Rough grinding wheel (first grinding wheel), 44a: Wheel base 44b: Coarse grinding wheel (first grinding wheel), 44c: Grinding surface 48: Finishing grinding unit, 50: Spindle, 52: Mount 54: Finishing grinding wheel (second grinding wheel), 54a: Wheel base 54b: Finishing grinding wheel (second grinding wheel), 54c: Grinding surface 60: Spinner cleaning device, 62: Conveying unit A1: Loading / unloading area, A2: Grinding area B1: Loading / unloading area, B2: Protective material grinding area B3: Rough grinding area, B4: Finishing grinding area S10: Pasting process S20: Back side holding process, S22: Front side holding process, S24: Rough grinding process S26: Inversion process, S28: Backside holding process S30: Flattening process S40: Inversion process, S42: Replacement process, S44: Surface side holding process S50: Dressing process, S60: Rough grinding process, S70: Finish grinding process

Claims

1. A method for processing a protective member attached to the surface side of a wafer and a grinding wheel, A back-side holding step in which the back side of the wafer is held with a chuck table and the other side of the protective member, which has one side attached to the front side, is exposed, After the back-side holding step, a flattening step is performed in which the other side of the protective member is ground with the grinding wheel to reduce the degree of unevenness on the other side of the protective member. After the planarization step, a dressing step is performed in which the grinding wheel is brought into contact with a single crystal substrate made of the same material as the single crystal substrate constituting the wafer and ground, thereby dressing the grinding wheel. A processing method characterized by comprising the following:

2. The processing method according to claim 1, characterized in that the grinding wheel has abrasive grains with an average particle size of 1 μm or more and 20 μm or less, and a vitrified bond, and the concentration of abrasive grains in the grinding wheel is 50 or more and 150 or less.

3. A method for processing wafers, protective members, and grinding wheels for grinding protective members, A bonding step of attaching one side of the protective member to the surface side of the wafer, A rough grinding step in which rough grinding is performed on the back side of the wafer with a first grinding wheel having a first grinding wheel, After the rough grinding step, a finish grinding step is performed on the back side of the wafer using a second grinding wheel having a second grinding wheel, Equipped with, Before the rough grinding step or before the finish grinding step, A back-side holding step in which the back side of the wafer is held with a chuck table to expose the other side of the protective member, After the back-side holding step, a flattening step is performed to reduce the degree of unevenness on the other side of the protective member by grinding the other side of the protective member with a grinding wheel for grinding the protective member, A dressing step is performed after the planarization step, in which the grinding wheel for grinding the protective member is brought into contact with a single crystal substrate made of the same material as the single crystal substrate constituting the wafer and ground, thereby dressing the grinding wheel for grinding the protective member. A processing method characterized by further comprising the following.

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