Grinding device

Abstract

Grinding device (1), comprising: a holding table (30) that holds a workpiece (W); and a grinding unit (7) comprising a spindle (70) and a grinding wheel (74) attached to the spindle (70), which grinds the workpiece (W) held by the holding table (30), wherein the grinding wheel (74) has a grinding stone (74a) formed by bonding abrasive grains (P1) with a bonding agent, and the grinding device (1) further comprises: a grinding water supply unit (8) that supplies grinding water to at least the grinding stone (74a) when the workpiece (W) held by the holding table (30) is ground by the grinding unit (7); a light application unit (9) which is arranged adjacent to the holding table (30) and which applies light to a grinding surface of the grinding stone (74a) which grinds the workpiece (W) held by the holding table (30). and a light application unit movement section (2) which is configured to position the light application unit (9) in a first fixed position on a rotational trajectory (E) of the grinding wheel (74) attached to the spindle (70) in the case that the grinding wheel (74) has a first diameter, and in a second fixed position on a rotational trajectory (E) of the grinding wheel (74) in the case that the grinding wheel (74) has a second diameter.

Description

BACKGROUND OF THE INVENTIONTechnical field

[0001] The present invention relates to a grinding apparatus including a holding table holding a workpiece and a grinding unit (abrasive) having a grinding wheel for grinding the workpiece held by the holding table. Description of related technology

[0002] A plate-shaped workpiece such as a semiconductor wafer is ground by a grinder (see, for example, Japanese Patent Laid-Open No. 2001-284303) to be thinned to a predetermined thickness, and then divided by a cutter or the like into individual component chips used for various electronic apparatuses and the like.

[0003] Further prior art helpful for understanding the present invention can be found in the following documents: US 6 899 592 B1 relates to a polishing tool containing abrasive particles and a binder for binding the abrasive particles together, wherein the polishing tool is pressed against a substrate to polish the substrate.

[0004] DE 10 2016 200 971 A1 concerns a cutting blade for cutting a workpiece. PRESENTATION OF THE INVENTION

[0005] When the wafer is made of a material that is difficult to grind, such as gallium nitride (GaN), silicon carbide (SiC), or gallium arsenide (GaAs), there is a problem that the amount of wear on a grinding wheel's grindstone is large, thus increasing production costs. In addition, when grinding a wafer made of a metal or a wafer in which metallic electrodes are partially exposed on a surface of the wafer to be ground, there is a problem that the ductility of the metal makes grinding difficult.

[0006] It is therefore an object of the present invention to inhibit excessive wear of a grindstone and enable smooth grinding in the case of grinding a wafer made of a material difficult to grind or a wafer including a metal.

[0007] According to one aspect of the present invention, a grinding device is provided including a holding table that holds a workpiece and a grinding unit including a spindle and a grinding wheel mounted on the spindle and grinding the workpiece held by the holding table. The grinding wheel includes a grindstone formed by bonding abrasive grains with a binder.The grinding device further includes: a grinding water supply unit that supplies grinding water at least to the grindstone when the workpiece held by the holding table is ground by the grinding unit; a light application unit that is arranged adjacent to the holding table and that applies light to a grinding surface of the grindstone that grinds the workpiece held by the holding table; and a light application unit moving section that is configured to position the light application unit at a first fixed position on a rotation trajectory of the grinding wheel attached to the spindle in the case that the grinding wheel has a first diameter, and at a second fixed position on a rotation trajectory of the grinding wheel in the case that the grinding wheel has a second diameter.

[0008] Preferably, the grindstone comprises the abrasive grains and photocatalytic grains bound by the binder, and the light applying unit applies light that excites the photocatalytic grains.

[0009] In addition, the binding agent is preferably a ceramic bond.

[0010] In the grinding device according to the present invention, the grinding wheel comprises the grindstone formed by bonding abrasive grains with the bonding agent, and the grinding device includes: the grinding water supply unit that supplies grinding water at least to the grindstone when the workpiece held by the holding table is ground by the grinding unit; the light application unit that is arranged adjacent to the holding table and that applies light to the grinding surface of the grindstone that grinds the workpiece held by the holding table; and the light application unit moving section by which the light application unit is moved at the first position on the rotation trajectory of the grinding wheel attached to the spindle in the case where the grinding wheel has the first diameter, and in the case where the grinding wheel has the second diameter,can be positioned at the second position of the rotation trajectory of the grinding wheel. Therefore, it is possible to arrange the light application unit at a suitable position according to the diameter of the grinding wheel that the grinding unit has, to efficiently make the grindstone that cuts into the workpiece hydrophilic or the like, thereby improving a cooling effect of the grinding water, inhibiting wear of the grindstone, and improving chip removal properties. Furthermore, with the hydrophilic or the like grindstone, grinding water is effectively supplied to the machining region in which the grindstone grinds the workpiece, and therefore, machining quality is not reduced due to machining heat, and smooth grinding can be achieved even in the case where the workpiece is a wafer formed of a difficult-to-grind material.

[0011] In addition, when the grindstone is formed by bonding the abrasive grains and the photocatalytic grains with the binder, and the light application unit applies light that excites the photocatalytic grains, it is ensured that the supplied grinding water has an oxidizing power due to hydroxyl radicals. Therefore, even if the workpiece is a wafer formed of, for example, a difficult-to-grind material, it is possible to oxidize the surface of the workpiece to be ground by the strong oxidizing power of the thus generated hydroxyl radicals to perform grinding while the surface is embrittled by the oxidation, and to grind the workpiece smoothly.Similarly, even when the workpiece is a wafer formed of a metal or a wafer in which metallic electrodes are partially exposed on the surface of the wafer to be ground, grinding can be performed while the metal is embrittled by oxidation by the strong oxidizing force of the hydroxyl radicals, and thereby the workpiece can be ground smoothly.

[0012] With the vitrified bond used as the binder in the grindstone, the property of making the grinding surface of the grindstone hydrophilic or the like by applying light thereto can be further improved.

[0013] The above and other objects, features and advantages of the present invention and the mode for carrying them out will become clearer and the invention itself will be best understood by studying the following description and the appended claims with reference to the attached drawings which show a preferred embodiment of the invention. SHORT DESCRIPTION OF THE FIGURES Fig. 1 is a perspective view showing an example of a grinding device; Fig. 2 is a perspective view showing an example of a grinding wheel; Fig. 3 is a front view showing a part of a grindstone in an enlarged form; Fig. 4 is a perspective view illustrating an example of a positional relationship of a grinding unit, a holding table, and a light applying unit; Fig. 5 is a vertical sectional view showing an example of the structure of a light applying unit moving section; Fig. 6 is an end view illustrating a state in which a workpiece held by a holding table is ground by the grindstone; Fig. 7A is a top view showing an arrangement relationship of a rotation trajectory of a grinding wheel, a machining area in which the workpiece is machined by the grindstone, and the light application unit during grinding; Fig. 7B is a diagram, viewed from a lateral side, showing a state in which the grindstone cuts into the workpiece immediately after light is applied to a grinding surface; and Fig. 8 is an end view partially showing a state in which cleaning water is supplied to a cover via a light emitting portion during grinding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] One in Fig. The grinding apparatus 1 shown in FIG. 1 is an apparatus that grinds a workpiece W held on a holding table 30 by a grinding unit (abrasive) 7 provided with a grinding wheel 74. A front side (Y-direction side) on a base 10 of the grinding apparatus 1 is an attachment / detachment area A where the workpiece W is attached to and detached from the holding table 30, and a back side of the base 10 is a grinding region B where grinding of the workpiece W is performed by the grinding unit 7. An input means 12 through which an operator inputs machining conditions and the like to the grinding apparatus 1 is arranged on the front side of the base 10.

[0015] The holding table 30 is, for example, circular in external shape and includes a suction holding section 300 that holds the workpiece W by suction, and a frame body 301 that supports the suction holding section 300. The suction holding section 300 is connected to a suction source (not shown), and the workpiece W is held by suction on a holding surface 300a, which is an exposed surface of the suction holding section 300. The holding surface 300a of the holding table 30 is formed in the shape of a conical surface having an extremely gentle slope with a rotation center of the holding table 30 as a highest point.The holding table 30 is surrounded by a cover 31, is rotatable about an axis in the vertical direction, and can be reciprocated in the Y-axis direction between the attachment / detachment area A and the grinding area B by a Y-axis direction feed means (not shown) attached to the underside of the cover 31 and a bellows cover 31a connected to the cover 31. The holding table 30 is, for example, an 8-inch holding table for use in the case of grinding a workpiece W having an 8-inch diameter. In the case of grinding a workpiece W having a 6-inch diameter (see . Fig. 7A), the grinding device 1 has a 6-inch holding table 30a (see Fig. 7A), which replaces the 8-inch holding table 30, allowing workpieces of different wafer sizes to be suitably ground.

[0016] A column 11 is provided upright in the grinding section B, and the grinding feed device 5 for displacing the grinding unit 7 in a grinding feed in a Z-axis direction is arranged on a lateral side of the column 11. The grinding feed device 5 includes a ball screw 50 having an axis in the Z-axis direction, a pair of guide rails 51 arranged parallel to the ball screw 50, a motor 52 connected to an upper end of the ball screw 50 and rotating the ball screw 50, a lifting plate 53 inside which a nut is screw-engaged with the ball screw 50 and side portions of which make sliding contact with the guide rails 51, and a holder 54 connected to the lifting plate 53 and holding the grinding unit 7.When the motor 52 rotates the ball screw 50, the lifting plate 53 is reciprocated in the Z-axis direction while being guided attached to the guide rails 51, and the grinding unit 7 held by the holder 54 is put into grinding feed in the Z-axis direction.

[0017] The grinding unit 7 includes a spindle 70 having an axial direction in the Z-axis direction, a housing 71 that supports the spindle 70 in a rotatable manner, a motor 72 that rotatably drives the spindle 70, a holder 73 connected to a tip of the spindle 70, and a grinding wheel 74 detachably attached to a lower surface of the holder 73.

[0018] The Fig. The grinding wheel 74 shown in Figure 2 includes an annular wheel base 74b and a plurality of substantially rectangular parallelepiped-shaped grinding stones 74a arranged in an annular pattern on a bottom surface (free end portion) of the wheel base 74b. An upper surface of the wheel base 74b is provided with threaded holes 74c and jet openings 74d through which grinding water is jetted to the grinding stones 74a. As shown in Fig. As shown in Figure 3, the grindstone 74a in the present embodiment is formed by mixing diamond abrasive grains P1 with photocatalytic grains P2 such as titanium oxide (TiO2) grains and binding the mixture with a ceramic binder B1, which is a ceramic or sintered binder. The grinding wheel 74 is fixed to a lower surface of the holder 73 by attaching Fig. 1, are screwed into threaded engagement with the threaded holes 74c in the disc base 74b through holes provided in the bracket 73.

[0019] The shape of the grinding stone 74a may be an integral annular shape, and the photocatalytic grains P2 may be tin oxide grains, zinc oxide grains, cerium oxide grains, or the like. Note that the grinding stone 74a may not contain the photocatalytic grains P2, and a binder other than the ceramic binder may be used as the binder therein.

[0020] For example, the grinding wheel 74 is a grinding wheel with a diameter of 8 inches, which is used in the case of grinding a workpiece W with a diameter of 8 inches. In the case where a workpiece W1 with a diameter of 6 inches is ground by the grinding device 1, the grinding wheel 74 with a diameter of 8 inches is replaced with the grinding wheel with a diameter of 6 inches, whereby suitable grinding of workpieces of various sizes can be performed.

[0021] A method for manufacturing the grinding wheel 74 is as follows. First, the ceramic binder B1 is mixed with diamond abrasive grains P1 having a grain size of #1000, and the resulting mixture is further mixed with the photocatalytic grains P2, followed by stirring. As the ceramic binder B1, for example, silicon dioxide (SiO2) is used as a main component, to which a minute amount of additive may be mixed to control the melting point. Next, this mixture is heated to a predetermined temperature, followed by pressing to form the mixture into a substantially rectangular parallelepiped shape. After that, sintering is further performed at a high temperature for several hours to produce a grindstone 74a. The content of the photocatalytic grains P2 in the grindstone 74a is, for example, 15% by weight.A plurality of the thus-prepared grinding stones 74a are arranged in an annular shape and fixed to a bottom surface of the wheel base 74b to manufacture the grinding wheel 74. Note that the grain size of the diamond abrasive grains P1 is not limited to the example of the present embodiment and can be appropriately modified according to the type and content of the photocatalytic grains P2 and similar factors.

[0022] Inside the Fig. 1, a channel 70a connected to a grinding water supply unit (grinding water supply means) 8 for supplying grinding water to the grindstones 74a and serving as a passage of the grinding water is provided, passing in the axial direction (Z-axis direction) of the spindle 70, so that the grinding water that has passed through the channel 70a can pass through the holder 73 and be ejected from the wheel base 74b to the grindstones 74a.

[0023] The grinding water supply unit 8 includes a grinding water source 80 that stores water (for example, pure water), a piping 81 connected to the grinding water source 80 and communicating with the passage 70a, and a control valve 82 arranged at an arbitrary position on the piping 81 to regulate the amount of supplied grinding water and to supply grinding water at least to the grindstones 74a.

[0024] As in Fig. 1 and Fig. 4, the grinding device 1 includes a light application unit (light application means) 9 which is arranged adjacent to the holding table 30 and which applies light to grinding surfaces (lower surfaces) of the grinding stones 74a which grind the workpiece W held by the holding table 30. As shown in Fig. 4, the light application unit 9 includes, for example, a base portion 90 having a substantially arcuate outer shape, a plurality of (four in the illustrated example) light emitting portions 91 arranged in alignment with an upper surface of the base portion 90, a cleaning water supply portion 92 that supplies cleaning water (for example, pure water) toward the light emitting portions 91, and a cover 93 that prevents dirt from adhering to the light emitting portions 91.

[0025] For example, the light-emitting portions 91 formed in recesses formed in the upper surface of the base portion 90 are light-emitting diodes (LEDs) that can emit light of a predetermined wavelength and can be switched between an ON state and an OFF state by a power source (not shown). Note that in the case where the photocatalytic grains P2 contained in the grindstones 74a are titanium oxide grains as in the present embodiment, the wavelength of the light (ultraviolet (UV) light) emitted from the light-emitting portions 91 is, for example, preferably 201 to 400 nm, and more preferably 201 to 365 nm.

[0026] Note that in the case where the grinding stone 74a does not contain the photocatalytic grains P2, the light-emitting portion 91 is preferably a low-pressure mercury lamp or a dual-wavelength LED capable of emitting light at two wavelengths, and preferably capable of emitting light having a wavelength of 80 to 200 nm (for example, a wavelength of 185 nm) and light having a wavelength of 240 to 280 nm (for example, a wavelength of 254 nm). It should be understood that in the case where the grinding stone 74a does not contain the photocatalytic grains P2, light having a wavelength of 201 to 365 nm can be applied thereto.

[0027] The plate-shaped cover 93 is made of, for example, a transparent member such as glass and is fixed to the upper surface of the base portion 90 in such a manner as to cover the light-emitting portions 91. For example, the base portion 90 is movable in the vertical direction, so that when grinding is performed, the height position of an upper surface of the cover 93 can be set to a desired height position, taking into account a grinding feed position of the grinding stones 74a.

[0028] The cleaning water supply section 92 includes, for example, a cleaning water source (not shown) in which water is stored, and a cleaning water nozzle 920 connected to the cleaning water source. The cleaning water nozzle 920 is attached, for example, to a side surface of the base section 90 in such a way as to lie along the base section 90, and a plurality of shallow slit-shaped jet openings 920a for jetting cleaning water toward the cover 93 covering the light-emitting sections 91 are aligned in the longitudinal direction of the cleaning water nozzle 920. The jet openings 920a have a shape, a size, an angle relative to the light-emitting section 91, etc., selected in such a way that the flow of the jetted cleaning water can be directed toward the upper surface of the cover 93.

[0029] The grinding device 1 is provided with a light application unit moving section (light application means moving section) 2, by which the light application unit 9, in the case where the grinding wheel 74 has a first diameter (for example, 8 inches), is moved to a first position on a rotation trajectory E (see Fig. 7A) of the grinding wheel 74 and, in the case where the grinding wheel has a second diameter (for example, 6 inches), at a second position on a rotation trajectory e (see Fig. 7A) of the grinding wheel can be arranged.

[0030] The Fig. 4 and Fig. 5 Light application unit moving section 2 includes, for example, a pair of guide rails 20 to which the base section 90 of the light application unit 9 is fitted in such a manner as to be slidable toward the side of the direction of arrow R1 or the side of the direction of arrow R2, and a position fixing mechanism 21 (in Fig. 4 not shown), which is moved together with the base section 90 and can fix the base section 90 at a predetermined position in the extension direction of the guide rails 20.

[0031] The Fig. The position fixing mechanism 21 shown in Fig. 5 includes, for example, a housing 210 fixed to a side surface of the base portion 90 of the light application unit 9; a movable member 211 provided with a projection 211a and moved in the vertical direction within the housing 210; a compression coil spring 212 disposed within the housing 210 and storing, by compression, a biasing force for pushing back the movable member 211 upward; and a piston 213 inserted on the inner peripheral side of the compression coil spring 212, having an upper end fixed to the movable member 211, and being integrally formed with a knob 213a at a lower end thereof.

[0032] For example, a lower surface of each of the pair of guide rails 20 is formed with a recessed positioning groove 200 and a recessed positioning groove 201 at a predetermined interval (e.g., 2 inches) in the extending direction of the guide rails 20. An upper surface of the housing 210 is formed, in a penetrating manner, with a projection hole through which the projection 211a projects to the outside. When the base portion 90 is slid along the guide rails 20 and the projection 211a is located under one of the recessed positioning grooves 200 or the recessed positioning grooves 201, the movable member 211 is pushed upward by the restoring force of the compression coil spring 212, and the projection 211a projecting from the housing 210 is fitted into either the recessed positioning groove 200 or the recessed positioning groove 201.Then, the light application unit 9 is fixed at a predetermined position in the extending direction of the guide rails 20.

[0033] One in Fig. 1 in the case of grinding the workpiece W by using the grinding device 1 will now be described below.

[0034] The circular disc-shaped workpiece W with a diameter of 8 inches, which is in Fig. 1, for example, is a semiconductor wafer made of SiC, which is difficult to grind. A plurality of components are formed in areas defined by streets (parting lines) on a front surface Wa of the workpiece W, which faces the lower side in Fig. 1, are divided into a grid pattern, and a protective tape T for protecting the front surface Wa is attached thereto. A back surface Wb of the workpiece W is a surface to be ground by the grinding wheel 74. Note that the shape and type of the workpiece W are not particularly limited, but can be appropriately modified relative to the grinding wheel 74; examples of the applicable workpieces W include a wafer formed of GaAs, GaN, or the like, a wafer formed of metal, and a wafer in which metallic electrodes are partially exposed on the back surface side of the wafer.

[0035] First, the workpiece W is placed on the holding surface 300a of the holding table 30 with its back surface Wb facing up in the attachment / detachment area A. Then, a suction force generated by a suction source (not shown) is transmitted to the holding surface 300a, whereby the holding table 30 holds the workpiece W by suction on the holding surface 300a. The workpiece W is in the state of being held by suction on the holding surface 300a, which is a gently inclined conical surface.

[0036] The holding table 30 is moved by the Y-axis direction feed means (not shown) in a +Y direction to a position below the grinding unit 7, thereby performing alignment of the grinding wheel 74 and the workpiece W held by the holding table 30. The alignment is performed, for example, in such a manner that the rotation center of the grinding wheel 74 is offset by a predetermined distance in the +Y direction from the rotation center of the workpiece W, and the rotation trajectory of the grindstones 74a passes the rotation center of the workpiece W. In addition, the inclination of the holding table 30 is adjusted so that the holding surface 300a, which is a gently inclined conical surface, is parallel to the grinding surfaces, which are lower surfaces of the grindstones 74a, thereby causing the back surface Wb of the workpiece W to be parallel to the grinding surfaces of the grindstones 74a.

[0037] After the alignment of the grinding wheel 74 and the workpiece W has been carried out, the spindle 70 is rotatably driven by the motor 72 and at the same time the grinding wheel 74 is rotated counterclockwise as viewed from the +Z direction side, as shown in Fig. 6. In addition, the grinding unit 7 is fed in the -Z direction by the grinding feed means 5, and the grinding wheel 74 is gradually lowered in the -Z direction, and the grinding stones 74a come into contact with the back surface Wb of the workpiece W, thereby performing grinding. Furthermore, during grinding, the workpiece W is also rotated counterclockwise in the direction viewed from the +Z direction side along with the rotation of the holding table 30, so that the grinding stones 74a grind the entire area of ​​the back surface Wb of the workpiece W.

[0038] During grinding, the grinding water supply unit supplies grinding water into the channel 70a in the spindle 70. As shown in Fig. 6, the grinding water supplied into the passage 70a passes through the passages 73b formed within the attachment 73 at regular intervals in the circumferential direction of the attachment 73, and is further jetted through the jet openings 74d of the disk base 74b toward the grindstones 74a.

[0039] Since the workpiece W is suction-held on the holding surface 300a of the holding table 30 along the holding surface 300a, which is a gently inclined conical surface, the grinding stones 74a take up a position in an area E1 (hereinafter referred to as machining area E1) in the rotation trajectory E of the grinding wheel 74, which is indicated by a dot-dash line in Fig. 7A, contact with the workpiece W and grind it.

[0040] For example, in a state where the alignment of the grinding wheel 74 and the holding table 30 has been performed, the light application unit 9 disposed adjacent to the holding table 30 is arranged at the immediately upstream position of a place where the grinding stones 74 enter the machining area E1, as shown in Fig. 7A. In addition, in the present embodiment, the light application unit 9 is positioned at the first position of the rotation trajectory E of the grinding wheel 74 because the grinding wheel 74 attached to the spindle 70 has the first diameter (8 inches). The first position is, for example, a position such that the light emitting portions 91 of the light application unit 9 are positioned below the grinding surfaces of the grinding stones 74a. The knob 213a of the position fixing mechanism 21, which is shown in Fig. 5, is pulled downward against the compression coil spring 212, and the protrusion 211a is released from the recessed positioning grooves 201 of the guide rails 20, resulting in a state in which the position fixing mechanism 21 and the light application unit 9 to which the position fixing mechanism 21 is fixed are movable along the guide rails 20. Note that the recessed positioning grooves 201 are recessed grooves used at the time of positioning the light application unit 9 at the second position on the rotation trajectory e of the grinding wheel in the case where the grinding wheel has the second diameter (6 inches). The second position is, for example, a position in which the light emitting portions 91 of the light application unit 9 are positioned below the grinding surfaces of the grindstones of the 6-inch grinding wheel.

[0041] When the position fixing mechanism 21 is moved in the direction of arrow R1 toward the recessed positioning grooves 200 used at the time of positioning the light applying unit 9 at the first position on the rotation trajectory E of the grinding wheel 74, the projection 211a is fitted into the recessed positioning grooves 200 of the guide rails 20 by the biasing force of the compression coil spring 21, and the light applying unit 9 can be fixed to the guide rails 20 in a state where the light applying unit 9 is positioned at the first position on the rotation trajectory E of the grinding wheel 74.Note that, since the projection 211a of the movable member 211 is in contact with the lower surfaces of the guide rails 20 during movement of the position fixing mechanism 21, a released state of the position fixing mechanism 21 is maintained even if the pusher 213a is not kept pulled down during the movement, and when the projection 211a reaches a position below the recessed positioning grooves 200, it is automatically fitted into the recessed positioning grooves 200 by the biasing force of the compression coil spring 212, and the position fixing mechanism 21 is also put into a fixing state.

[0042] When grinding starts, the light emitting portions 91 of the light applying unit 9 positioned at the first position are put into an ON state, and the light emitting portions 91 emit light (UV light) of a wavelength of, for example, about 365 nm. Then, this light is applied from directly below to the grinding surfaces of the grinding stones 74a of the grinding wheel 74 being rotated.

[0043] By applying the light, the photocatalytic grains P2 mixed in the grinding stones 74a are excited. That is, electrons in a valence band of the photocatalytic grains P2 are excited, generating two types of carriers: electrons and holes. The holes generated in the photocatalytic grains P2 mixed in the grinding stones 74a oxidize the grinding water that comes into contact with the surfaces of the photocatalytic grains P2, thereby producing hydroxyl radicals with high oxidizing power. Therefore, the grinding water that has contacted the grinding surfaces of the grinding stones 74a is given oxidizing power due to the hydroxyl radicals at least on the back surface Wb of the workpiece W.

[0044] Since the workpiece W formed of SiC is embrittled by oxidation by the thus-produced hydroxyl radicals, it becomes easy to grind the workpiece W with the grinding wheel 74. In addition, the presence time of the thus-produced hydroxyl radicals is very short, and therefore, no oxidation other than that of the back surface Wb of the workpiece W is caused by the grinding water. In addition, the discharged grinding water also acts to cool the part of contact between the grindstones 74a and the back surface Wb of the workpiece W and to remove grinding debris generated on the back surface Wb of the workpiece W.

[0045] Note that even where, for example, the workpiece W is a wafer formed of a metal or a wafer in which metallic electrodes are partially exposed on the back surface side of the wafer, grinding can be performed while the metal is embrittled by oxidation by the strong oxidizing force of the hydroxyl radicals, so that uniform grinding of the workpiece can be achieved.

[0046] In addition, the hydrophilicity of the grinding surfaces of the grindstones 74a formed by using the vitrified bond B1 as a binder is improved, for example, by forming highly polar hydrophilic groups by applying light, so that the grinding water is less likely to form droplets on the grinding surfaces of the grindstones 74a, and the grinding water tends to spread in a water film form over the entire grinding surfaces of the grindstones 74a. Therefore, the thus hydrophilic grindstones 74a enter the machining area E1 while accompanied by a large amount of grinding water, and grind the back surfaces Wb of the workpiece W. As more grinding water enters the contact area between the back surfaces Wb of the workpieces W and the grinding surfaces of the grindstones 74a, generation of frictional heat in the contact area is inhibited.As a result, excessive wear of the grinding stones 74a can be inhibited, and chip removal performance can be improved. Furthermore, with the hydrophilic grinding stones 74a, grinding water is effectively supplied to the machining area E1 where the grinding stones 74a grind the workpiece W, and thus, the machining quality can be prevented from being reduced by machining heat.

[0047] Note that in the case where the grindstone 74a does not contain the photocatalytic grains P2, the light-emitting portions 91 can apply, for example, UV light with a wavelength of 185 nm and UV light with a wavelength of 254 nm toward the grindstones 74a. When the UV light with the wavelength of 185 nm is applied to the grinding surfaces of the grindstones 74a, oxygen molecules in the air located between the bottom surfaces of the grindstones 74a and the light-emitting portions 91 absorb the UV light, thereby generating oxygen atoms in a ground state. The thus generated oxygen atoms combine with oxygen molecules in the surroundings to generate ozone. Further, the generated ozone absorbs UV light with the wavelength of 254 nm, thereby generating active oxygen in an excited state.Since active oxygen and ozone have a high oxidizing power, they combine with carbon, hydrogen, or the like generated on the grinding surfaces of the grinding stones 74a to gradually form highly polar hydrophilic groups on the grinding surfaces of the grinding stones 74a, resulting in the grinding stones 74 being made hydrophilic.

[0048] In addition, as in Fig. 8, the cleaning water supply section 92 supplies cleaning water to the cover 93 via the light-emitting sections 91 during grinding. Specifically, the cleaning water jetted from the cleaning water nozzle 920 onto the cover 93, the flow of which is appropriately straightened, gradually removes dirt such as grinding debris deposited on the cover 93, whereby the light generated by the light-emitting sections 91 during grinding can always be appropriately applied to the processing surfaces of the grindstones 74a.

[0049] According to an example of experimental results obtained with respect to grinding, grinding a 50 μm SiC workpiece W using a conventional grinder required 110 seconds, whereas grinding using the grinding apparatus 1 according to the present invention required only 90 seconds, thus realizing a reduction in grinding time. In addition, when grinding a Si surface of a workpiece W, 83% of the total part of the grindstone C of a conventional grinder was worn, with a grinding amount of 100, whereas the wear of the grindstones 74a of the grinding apparatus 1 according to the present invention was only 57% of the total part, with a grinding amount of 100.Further, in grinding a C surface of a workpiece W, 60% of the total part of the grindstone of an ordinary grinder was worn, the grinding amount being 100, whereas the wear of the grindstones 74a of the grinder 1 according to the present invention was only 39% of the total part, the grinding amount being 100.

[0050] Note that the grinding device 1 according to the present invention is not limited to that in the present embodiment, and the structure of the grinding device 1 illustrated in the attached drawings and the like is not limited, and modifications can be made appropriately within such ranges that the effect of the present invention can be produced.

[0051] For example, in the case of grinding a workpiece W1 with a diameter of 6 inches in the grinding device 1, the 8-inch holding table 30 is replaced by a 6-inch holding table 30a, and the grinding wheel 74 with a diameter of 8 inches is replaced by a grinding wheel with a diameter of 6 inches. Further, in a state where alignment of the 6-inch grinding wheel and the 6-inch holding table 30a has been performed during grinding, the light application unit 9 is positioned at the second position on the rotation trajectory e of the 6-inch grinding wheel, which is indicated by a dotted line in Fig. 7A is shown.

[0052] Specifically, the protrusion 211a is released from the recessed positioning grooves 200 of the guide rails 20, resulting in a state where the light application unit 9 is movable along the guide rails 20. Then, the position fixing mechanism 21 is moved in the direction of arrow R2 toward the recessed positioning grooves 201, and the protrusion 211a is fitted into the recessed positioning grooves 201 of the guide rails 20, thereby fixing the light application unit 9 to the guide rails 20 in a state where the light application unit 9 is positioned at the second position on the rotation trajectory e of the grinding stones of the 6-inch grinding wheel. In this state, grinding of the 6-inch workpiece W1 is performed while light of a predetermined wavelength is applied from the light application unit 9 to the grinding surfaces of the grinding stones 74a.

[0053] The structure of the position fixing mechanism 21 of the light application unit moving section 2 is not limited to the example in the present embodiment, and the part where the position fixing mechanism 21 is to be arranged is not limited to the side surface of the base section 90 of the light application unit 9. In addition, for example, a recessed positioning groove other than the recessed positioning groove 200 and the recessed positioning groove 201 may be formed at a predetermined position offset from the recessed positioning groove 201 in the lower surfaces of the guide rails 20 by 2 inches further toward the arrow R2 side, so that in the case of grinding a workpiece with a diameter of 4 inches, the light application unit 9 can be positioned at a third position on a rotation trajectory of a 4-inch grinding wheel.

[0054] The present invention is not limited to the details of the embodiment described above. The scope of the invention is defined by the appended claims.

Claims

[1] Grinding device (1), comprising: a holding table (30) holding a workpiece (W); and a grinding unit (7) including a spindle (70) and a grinding wheel (74) mounted on the spindle (70) and grinding the workpiece (W) held by the holding table (30), wherein the grinding wheel (74) comprises a grindstone (74a) formed by bonding abrasive grains (P1) with a binder, and the grinding device (1) further comprises: a grinding water supply unit (8) which supplies grinding water to at least the grindstone (74a) when the workpiece (W) held by the holding table (30) is ground by the grinding unit (7); a light application unit (9) arranged adjacent to the holding table (30) and applying light to a grinding surface of the grindstone (74a) that grinds the workpiece (W) held by the holding table (30) and a light application unit moving section (2) configured to position the light application unit (9) in a first fixed position on a rotation trajectory (E) of the grinding wheel (74) fixed to the spindle (70) in the case that the grinding wheel (74) has a first diameter, and in a second fixed position on a rotation trajectory (E) of the grinding wheel (74) in the case that the grinding wheel (74) has a second diameter. [2] Grinding device (1) according to claim 1, wherein the grindstone (74a) comprises the abrasive grains (P1) and photocatalytic grains (P2) bound by the binder and the light application unit (9) applies light which excites the photocatalytic grains. [3] Grinding device (1) according to claim 1, wherein the binder is a ceramic binder. [4] Grinding device (1) according to claim 2, wherein the binder is a ceramic binder.

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