Chuck table and method for cleaning the same

Abstract

To provide a chuck table which enables easy washing-away of machining chips stuck to its holding surface.SOLUTION: A holding part and / or a frame body part of a chuck table are made of ceramics and contains photocatalyst particles exposed on a holding surface. Thus, if water is supplied immediately after or during application of light to the holding surface of the chuck table, the waster is decomposed by the activated photocatalyst particles to generate a hydroxy radical. The hydroxy radical thus generated causes plus-charging of machining chips stuck to the holding surface to be easily peeled from the holding part and / or the frame body part made of ceramics. Therefore, on the chuck table, the machining chips stuck to the holding surface can be easily washed away.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a chuck table having a porous holding portion and a dense frame portion surrounding the holding portion, for holding a workpiece on a holding surface to which both the holding portion and the frame portion are exposed, and to a method for cleaning this chuck table. [Background technology]

[0002] Chips for devices such as integrated circuits (ICs) are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, by grinding the backside of a workpiece such as a wafer having multiple devices formed on its front side to thin it, and then cutting the workpiece to divide it along the boundaries of the multiple devices.

[0003] A grinding device for grinding a workpiece generally includes a chuck table for holding the workpiece and a spindle with a grinding wheel attached to its tip (see, for example, Patent Document 1). The grinding wheel includes an annular base having an end face on one side of which an annular groove is formed, and a plurality of grinding stones arranged in an annular shape, each having a base end fixed in the annular groove and each having a processing surface (grinding surface) located at its tip.

[0004] When thinning a workpiece in a grinding device, the workpiece is first held by a chuck table so that its backside is exposed. Then, by rotating both the chuck table and the spindle and bringing them closer together, the grinding surfaces of the multiple grinding wheels are rotated and pressed against the backside of the workpiece. This allows the workpiece to be ground by the multiple grinding wheels and thinned.

[0005] A cutting device for cutting a workpiece generally includes a chuck table for holding the workpiece and a spindle with a cutting blade attached to the tip. The cutting blade has a grinding wheel having a circular ring shape whose outer surface becomes the processing surface (cutting surface).

[0006] When dividing a workpiece in a cutting device, the workpiece is first held by a chuck table, for example, via a dicing tape. Then, while rotating the spindle, the cutting blade penetrates the workpiece and cuts into the dicing tape. The chuck table and the spindle are then moved relative to each other, and the cutting surface of the grinding wheel is pressed against the boundary between multiple devices on the workpiece while rotating. This causes the grinding wheel to cut the workpiece and divide it.

[0007] When a workpiece is processed (for example, grinded or cut) in this way, processing debris is generated, and the grinding wheel and the workpiece are heated by frictional heat, which may result in a deterioration in the processing quality of the workpiece. Therefore, such processing is often performed while supplying water near the contact interface (processing point) between the grinding wheel and the workpiece to wash away processing debris and cool the grinding wheel and the workpiece. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-288881 Summary of the Invention [Problem to be solved by the invention]

[0009] The chuck table generally has a portion made of a ceramic such as alumina (Al2O3). For example, the chuck table has a holding portion made of porous ceramic and a frame portion surrounding the holding portion and made of dense ceramic. The workpiece is held on the holding surface of the chuck table, where both the holding portion and the frame portion are exposed.

[0010] The surface zeta potential of the ceramic portion of the chuck table is often positive. On the other hand, the zeta potential of the machining debris generated during machining of the workpiece is often negative. Therefore, the machining debris generated during machining of the workpiece tends to adhere to the holding surface of the chuck table without being washed away.

[0011] In view of this, an object of the present invention is to provide a chuck table and a cleaning method therefor that can easily wash away machining debris adhering to the holding surface. [Means for solving the problem]

[0012] According to one aspect of the present invention, there is provided a chuck table having a porous holding portion and a dense frame portion surrounding the holding portion, for holding a workpiece on a holding surface to which both the holding portion and the frame portion are exposed, wherein the holding portion and / or the frame portion are made of ceramic and contain photocatalytic particles exposed on the holding surface.

[0013] Preferably, the photocatalyst particles are particles made of titanium oxide.

[0014] According to another aspect of the present invention, there is provided a method for cleaning a chuck table having a porous holding portion and a dense frame portion surrounding the holding portion, for holding a workpiece on a holding surface to which both the holding portion and the frame portion are exposed, the method comprising: cleaning the holding surface in a state in which water is decomposed by photocatalytic particles activated by irradiating light onto the holding surface, the photocatalytic particles being included in the holding portion and / or the frame portion and made of ceramic so as to be exposed at the holding surface, thereby generating hydroxyl radicals. [Effects of the Invention]

[0015] The holding portion and / or frame portion of the chuck table of the present invention are made of ceramic and contain photocatalytic particles exposed on the holding surface. Therefore, when water is supplied to the holding surface of the chuck table immediately after or during irradiation with light, the activated photocatalytic particles decompose the water, generating hydroxyl radicals.

[0016] When hydroxyl radicals are generated in this manner, the chips adhering to the holding surface become positively charged and are more likely to separate from the ceramic holding portion and / or frame portion. Therefore, in the chuck table of the present invention, the chips adhering to the holding surface can be easily washed away. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view schematically showing some of the components provided in the processing device. [Figure 2] FIG. 2 is a partial cross-sectional side view schematically showing components of the processing apparatus shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view schematically showing some of the components provided in a processing device such as a grinding device or a cutting device. Fig. 2 is a partially sectional side view schematically showing the components of the processing device shown in Fig. 1. In Fig. 1 and Fig. 2, the direction indicated by arrow X (X direction) and the direction indicated by arrow Y (Y direction) are directions perpendicular to each other on a horizontal plane, and the direction indicated by arrow Z (Z direction) is a direction (vertical direction) perpendicular to each of the X direction and the Y direction.

[0019] 1 and 2 includes a chuck table 4. The chuck table 4 has a porous holder 6 made of a ceramic such as alumina (Al2O3) and a dense frame 8 surrounding the holder 6. Specifically, the holder 6 has a large number of pores that penetrate the holder 6 in its thickness direction. On the other hand, the frame 8 does not have such pores.

[0020] The holding portion 6 and the frame portion 8 each have a disk shape. However, a recess 8a is formed on the upper surface of the frame portion 8, and the holding portion 6 is fitted into this recess 8a. Therefore, the chuck table 4 has a disk shape as a whole, and both the holding portion 6 and the frame portion 8 are exposed on the upper surface.

[0021] Each of the holding part 6 and the frame part 8 contains photocatalytic particles exposed on the upper surface of the chuck table 4. Examples of the photocatalytic particles include particles made of metal oxides such as titanium oxide (TiO2), tungsten oxide (WO3), strontium titanate (SrTiO3), or zinc oxide (ZnO), or metal sulfides such as zinc sulfide (ZnS) or cadmium sulfide (CdS). The particle diameter of each photocatalytic particle is, for example, 10 nm to 1000 nm.

[0022] Specifically, when it is assumed that the upper surface side of the chuck table 4 will be processed (for example, self-grinding), each of the holding part 6 and the frame part 8 contains, for example, photocatalyst particles dispersed throughout its entire area. On the other hand, when this is not assumed, each of the holding part 6 and the frame part 8 contains, for example, photocatalyst particles unevenly distributed on the upper surface side.

[0023] A flow path 8b is formed in the frame body 8 of the chuck table 4. The flow path 8b penetrates the central region of the frame body 8 in the thickness direction and opens at the bottom surface of the recess 8a. The flow path 8b communicates with the space near the upper surface of the chuck table 4 via a large number of pores present in the holding portion 6.

[0024] The chuck table 4 is supported by a cylindrical support shaft 10. This support shaft 10 extends along the Z direction, and its upper end is fixed to the lower surface side of the central region of the frame body part 8. In addition, a flow path that communicates with the flow path 8b formed in the frame body part 8 is formed in the support shaft 10.

[0025] The flow path formed in the support shaft 10 is connected to a suction source (not shown) such as an ejector via a valve (not shown) etc. When this valve is opened and the suction source is operated, a suction force acts on the space near the upper surface of the chuck table 4.

[0026] Therefore, the chuck table 4 can hold the workpiece using the upper surface, where both the holding portion 6 and the frame portion 8 are exposed, as the holding surface. Specifically, when the suction source communicating with the flow path 8b or the like is operated with the workpiece placed on the chuck table 4 so as to cover the holding portion 6, the workpiece is sucked toward the chuck table 4 and held there.

[0027] Furthermore, the support shaft 10 is connected to a rotation mechanism (not shown). This rotation mechanism includes, for example, a motor and a pulley. When the rotation mechanism is operated, the chuck table 4 rotates together with the support shaft 10 around a rotation axis that passes through the center of the holding surface of the chuck table 4 and is aligned in the Z direction.

[0028] The support shaft 10 is also connected to a horizontal movement mechanism (not shown). This horizontal movement mechanism includes, for example, a ball screw and a motor connected to the ball screw. Alternatively, the horizontal movement mechanism may include a turntable that supports the chuck table and a motor for rotating the turntable. When the horizontal movement mechanism is operated, the chuck table 4 moves horizontally together with the support shaft 10.

[0029] For example, when the horizontal movement mechanism is operated, the chuck table 4 moves to one of the following positions: a position for loading and unloading a workpiece onto and from the holding surface (loading / unloading position), a position for processing a workpiece held on the holding surface (processing position), and a position for cleaning the holding surface or a workpiece held on the holding surface (chuck table cleaning position). Note that each of Figures 1 and 2 shows the chuck table 4 positioned at the chuck table cleaning position.

[0030] A cleaning unit 12 and an illumination unit 14 are provided near the chuck table cleaning position. The cleaning unit 12 includes a nozzle 12a facing downward. The nozzle 12a is connected to the tip of a pipe-shaped arm 12b extending in a direction perpendicular to the Z direction. The base end of the arm 12b is connected to the tip (upper end) of a pipe-shaped support shaft 12c extending in the Z direction.

[0031] The support shaft 12c is inserted into a through-hole formed in the top plate of the housing 12d, and its base end is connected to a motor (not shown) built into the housing 12d. When the motor is operated, the arm 12b rotates together with the support shaft 12c around a straight line along the Z direction as a rotation axis, i.e., the nozzle 12a pivots.

[0032] For example, when this motor is operated, the nozzle 12a moves between a position (for example, a position directly above the center of the holding surface) (nozzle cleaning position) for cleaning the holding surface of the chuck table 4 positioned at the chuck table cleaning position or a workpiece held on the holding surface, and a position (nozzle retracted position) where it does not overlap with the chuck table 4 in a plan view. Note that Fig. 1 shows the nozzle 12a positioned at the nozzle retracted position, and Fig. 2 shows the nozzle 12a positioned at the nozzle cleaning position.

[0033] Furthermore, the support shaft 12c is connected to a water supply source (not shown) via a pipe (not shown) and a valve (not shown) built into the housing 12d. When this valve is opened and the water supply source is operated, water is supplied directly below from the nozzle 12a via the support shaft 12c and the arm 12b.

[0034] The lighting unit 14 includes a lighting plate 14a facing downward. The lighting plate 14a has, for example, a disk shape with a size approximately equal to that of the chuck table 4 in a plan view, and is a surface light that irradiates light with a wavelength of 100 nm to 380 nm.

[0035] The upper surface side of the central region of illumination plate 14a is connected to the tip end of arm 14b extending in a direction perpendicular to the Z direction. The base end of arm 14b is connected to the tip end (upper end) of support shaft 14c extending in the Z direction. Support shaft 14c is inserted into a through-hole formed in the top plate of housing 14d, and its base end is connected to a motor (not shown) built into housing 14d.

[0036] The arm 14b of the lighting unit 14 is longer than the arm 12b of the cleaning unit 12. The motor built into the housing 14d of the lighting unit 14 is located at approximately the same height as the motor built into the housing 12d of the cleaning unit 12. Therefore, when the motor built into the housing 14d of the lighting unit 14 is operated, the lighting plate 14a rotates in the space above the nozzle 12a.

[0037] For example, when this motor is operated, the illumination plate 14a moves between a position (illumination position) for irradiating light onto the holding surface when cleaning the holding surface of the chuck table 4 positioned at the chuck table cleaning position (for example, a position directly above the holding surface), and a position (illumination plate retracted position) where it does not overlap with the chuck table 4 in a plan view. Note that Fig. 1 shows the illumination plate 14a positioned at the illumination plate retracted position, and Fig. 2 shows the illumination plate 14a positioned at the illumination position.

[0038] In the processing device, for example, after processing a workpiece held on the holding surface of the chuck table 4, the chuck table 4 is cleaned to remove processing debris that is generated during the processing and adheres to the holding surface. Cleaning of the chuck table 4 is performed, for example, in the following order.

[0039] First, the chuck table 4, the nozzle 12a of the cleaning unit 12, and the lighting plate 14a of the lighting unit 14 are positioned at the chuck table cleaning position, the nozzle cleaning position, and the lighting position, respectively. Then, the chuck table 4 is rotated, water is supplied from the nozzle 12a toward the holding surface of the chuck table 4, and light is irradiated from the lighting plate 14a.

[0040] The holding portion 6 and frame portion 8 of the chuck table 4 are made of ceramics and contain photocatalytic particles exposed on the holding surface. Therefore, when water is supplied while the holding surface of the chuck table 4 is being irradiated with light, the activated photocatalytic particles decompose the water, generating hydroxyl radicals.

[0041] When hydroxyl radicals are generated in this manner, the machining debris adhering to the holding surface becomes positively charged and becomes more likely to separate from the ceramic holding portion 6 and frame portion 8. Therefore, in this chuck table 4, the machining debris adhering to the holding surface can be easily washed away.

[0042] It should be noted that the above is one aspect of the present invention, and the present invention is not limited to the above. For example, in the chuck table 4, either the holding portion 6 or the frame portion 8 may not contain photocatalytic particles. That is, in the chuck table 4, the holding portion 6 or the frame portion 8 may contain photocatalytic particles. Furthermore, the holding portion 6 or the frame portion 8 that does not contain photocatalytic particles may be made of a material other than ceramics (for example, metal, etc.).

[0043] Furthermore, when cleaning the holding surface of the chuck table 4, the supply of water from the nozzle 12a of the cleaning unit 12 and the irradiation of light from the illumination plate 14a of the illumination unit 14 do not have to be performed in parallel. In other words, this cleaning only needs to be performed in a state where water is decomposed by the activated photocatalytic particles and hydroxyl radicals are generated, so the supply of water may be started after the irradiation of light onto the holding surface is completed.

[0044] Furthermore, when cleaning the holding surface of the chuck table 4, not only water but also gas such as air may be supplied to the holding surface. When the holding surface is cleaned in this manner, for example, the nozzle 12a of the cleaning unit 12 may be replaced with a two-fluid nozzle.

[0045] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0046] 2: Processing equipment 4: Chuck table 6: Holding part 8: Frame body portion (8a: recess, 8b: flow path) 10: Support shaft 12: Cleaning unit (12a: nozzle, 12b: arm, 12c: support shaft, 12d: housing) 14: Lighting unit (14a: lighting plate, 14b: arm, 14c: support shaft, 14d: housing)

Claims

1. A chuck table having a porous holding portion and a dense frame portion surrounding the holding portion, for holding a workpiece on a holding surface to which both the holding portion and the frame portion are exposed, The holding portion and / or the frame portion are made of ceramics and contain photocatalytic particles exposed on the holding surface of the chuck table.

2. 2. The chuck table according to claim 1, wherein the photocatalytic particles are particles made of titanium oxide.

3. A cleaning method for a chuck table having a porous holding portion and a dense frame portion surrounding the holding portion, the chuck table holding a workpiece on a holding surface to which both the holding portion and the frame portion are exposed, comprising: A method for cleaning a chuck table, comprising: cleaning the holding surface in a state where water is decomposed by photocatalytic particles activated by irradiating light onto the holding surface, the photocatalytic particles being included in the holding portion and / or the frame portion made of ceramic and exposed on the holding surface, and hydroxyl radicals are generated by irradiating light onto the holding surface.

Images