POLISHING APPARATUS
A polishing apparatus according to the present invention includes a polishing tape (41) having a polishing surface, a substrate holder configured to hold and rotate a substrate (W), a press pad (50) configured to press the polishing tape against a bevel portion of the substrate held by the substrate holder, and a polishing-tape feeding mechanism (45) configured to cause the polishing tape to travel in its longitudinal direction. The press pad (50) includes a pad body (53), a plate-shaped pressing section having a pressing surface (51a) for pressing the bevel portion of the substrate through the polishing tape and having a rear surface (51b) opposite to the pressing surface, and a plurality of coupling sections (52) coupling the pressing section to the pad body. A space (S) is formed between the rear surface of the pressing section and the pad body.
The present invention relates to a polishing apparatus using a polishing tape, and more particularly to a polishing apparatus for polishing a bevel portion of a substrate, such as a semiconductor wafer.
BACKGROUND ARTFrom a viewpoint of improving a yield in semiconductor fabrications, management of a surface condition in a bevel portion of a semiconductor wafer has recently been drawing attention. Since a number of materials are deposited on a semiconductor wafer repeatedly to form multilayer structures, unwanted materials and damage are left on a bevel portion which is not used for actual products. As a conventional way of transporting and holding a wafer, it has been typically practiced to bring a holding member (e.g., a robot hand) into contact with a rear surface of a wafer. However, there is an increasing demand for maintaining cleanliness of the rear surface, as microfabrication technique of a device advances and a wafer having a diameter of 300 mm becomes mainstream. Therefore, it has been more common in recent years to transfer and hold a wafer by bringing a holding member into contact with only an edge of the wafer. Under such a background, the unwanted materials and damage, left on the bevel portion, are likely to come off the wafer during various processes and can adhere to a surface of a device. Such materials, attached to the device, can affect a yield in products.
In this specification, a bevel portion is, as shown in
While a cross-sectional shape of the bevel portion varies widely depending on substrate manufacturers, the bevel portion generally includes, as shown in
A polishing apparatus using a polishing tape is known as a device for removing a film formed on the bevel portion of the substrate. This type of polishing apparatus has a press pad arranged at a rear side of the polishing tape and is configured to press a polishing surface of the polishing tape against the bevel portion of the substrate by the press pad to thereby polish the bevel portion.
The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a polishing apparatus capable of controlling a contact area in a lateral direction of a bevel portion of a substrate and a distribution of loads applied along a vertical direction of the bevel portion of the substrate.
In order to solve the above drawbacks, one aspect of the present invention is to provide a polishing apparatus including: a polishing tape having a polishing surface; a substrate holder configured to hold and rotate a substrate; a press pad configured to press the polishing tape against a bevel portion of the substrate held by the substrate holder; and a polishing-tape feeding mechanism configured to cause the polishing tape to travel in its longitudinal direction. The press pad includes a pad body, a plate-shaped pressing section having a pressing surface for pressing the bevel portion of the substrate through the polishing tape and having a rear surface opposite to the pressing surface, and a plurality of coupling sections coupling the pressing section to the pad body. A space is formed between the rear surface of the pressing section and the pad body.
In a preferred aspect of the present invention, the plurality of coupling sections are arranged along a circumferential direction of the substrate held by the substrate holder.
In a preferred aspect of the present invention, the plurality of coupling sections are connected to both sides of the pressing section.
In a preferred aspect of the present invention, the plurality of coupling sections are connected to the rear surface of the pressing section and located inwardly from both sides of the pressing section toward a center of the pressing section.
In a preferred aspect of the present invention, the rear surface of the pressing section has a plurality of grooves extending in a direction perpendicular to a surface of the substrate.
In a preferred aspect of the present invention, a plurality of reinforcing members, extending in a direction perpendicular to a surface of the substrate, are secured to the rear surface of the pressing section.
In a preferred aspect of the present invention, the rear surface of the pressing section has at least one recess extending in a circumferential direction of the substrate.
In a preferred aspect of the present invention, the pressing section has a shape such that a thickness thereof increases gradually from both sides of the pressing section toward a center thereof.
In a preferred aspect of the present invention, the pressing section is made from rigid plastic.
According to the present invention, since the pressing surface is not compressed greatly when contacting the bevel portion, high polishing pressure can be applied to the central region of the bevel portion. Therefore, the polishing tool can polish the central region of the bevel portion effectively without excessively polishing the boundaries at both sides of the central region of the bevel portion.
A polishing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.
As shown in
The wafer stage unit 20, the stage moving mechanism 30, and the bevel polishing unit 40 are contained in a housing 11. The housing 11 is partitioned by a partition plate 14 into two spaces: an upper chamber (a polishing chamber) 15 and a lower chamber (a mechanical chamber) 16. The above-mentioned wafer stage 23 and the bevel polishing unit 40 are located in the upper chamber 15, and the stage moving mechanism 30 is located in the lower chamber 16. The upper chamber 15 has a side wall with an opening 12. This opening 12 is closed by a shutter 13 which is driven by an air cylinder (not shown).
The wafer W is transported into and from the housing 11 through the opening 12. Transporting of the wafer W is performed by a known wafer transporting mechanism (not shown), such as a transport robot hand.
An upper surface of the wafer stage 23 has a plurality of grooves 26. These grooves 26 communicate with a vacuum pump (not shown) via a vertically extending hollow shaft 27. When the vacuum pump is operated, vacuum is produced in the grooves 26, whereby the wafer W is held on the upper surface of the wafer stage 23. The hollow shaft 27 is rotatably supported by bearings 28, and further the hollow shaft 27 is coupled to a motor m1 via pulleys p1, p2 and a belt b1. With these configurations, the wafer W is rotated by the motor m1, with being held on the upper surface of the wafer stage 23.
The polishing apparatus further includes a wafer chucking mechanism 80 disposed in the housing 11. The wafer chucking mechanism 80 is configured to receive the wafer W, which has been transported into the housing 11 by the above-mentioned wafer transporting mechanism, and place the wafer W onto the wafer stage 23. Further, the wafer chucking mechanism 80 is configured to remove the wafer W from the wafer stage 23 and transport the wafer W to the above-mentioned wafer transporting mechanism. Only part of the wafer chucking mechanism 80 is shown in
A hand 73 of the wafer transporting mechanism transports the wafer W to a position between the first chuck hand 81 and the second chuck hand 82. When the first chuck hand 81 and the second chuck hand 82 are moved closer to each other, the pins 83 are brought into contact with the periphery of the wafer W, whereby the wafer W is held by the first chuck hand 81 and the second chuck hand 82. A center of the wafer W when held by the chuck hands 81 and 82 and a center of the wafer stage 23 (i.e., a rotational axis of the wafer stage 23) agree with each other. Therefore, the first chuck hand 81 and the second chuck hand 82 also function as a centering mechanism.
As shown in
In these configurations, when the ball screw b2 is rotated by the motor m2, the movable plate 33, the bearing base 29, and the hollow shaft 27 move in the longitudinal direction of the linear guides 35 to allow the wafer stage 23 to move in the direction parallel to the upper surface of the wafer stage 23. In
As shown in
When the rotating mechanism rotates the take-up roller 45b, the polishing tape 41 is fed to the polishing head 42 from the feed roller 45a. The polishing tape 41 travels in a direction perpendicular to the surface of the wafer W held by the wafer stage 23 and is wound on the take-up roller 45b.
The polishing tape 41 can be constituted by a base film and abrasive particles, such as diamond particles or SiC particles, bonded to one-side surface of the base film. This surface with the abrasive particles provides the polishing surface. The abrasive particles to be bonded to the polishing tape 41 are selected according to a type of wafer W and a required capability. Examples of the abrasive particles to be used include diamond particles and SiC particles having an average diameter ranging from 0.1 μm to 5.0 μm. A belt-shaped polishing cloth with no abrasive particles can also be used. The base film may be a film made from a flexible material, such as polyester, polyurethane, or polyethylene terephthalate.
Next, operation of the polishing apparatus thus constructed will be described. The wafer W is transported into the housing 11 through the opening 12 by the wafer transporting mechanism (not shown). The wafer chucking mechanism 80 receives the wafer W from the hands 73 (see
Thereafter, the wafer stage 23, together with the wafer W, is moved closer to the polishing head 42 by the stage moving mechanism 30. Subsequently, the wafer stage 23 is rotated by the motor m1 and then, supply of the polishing liquid onto the wafer W from the polishing liquid supply nozzles 58 is started. When a rotational speed of the wafer W and a flow rate of the polishing liquid reach predetermined values, the stage moving mechanism 30 moves the wafer W to bring the wafer W into contact with the polishing tape 41. At this time, the press pad 50 projects toward the wafer W by the pressing mechanism 56. The wafer W is moved by the stage moving mechanism 30 to a position where the bevel portion of the wafer W pushes back the press pad 50 and a pressing force of the pressing mechanism 56 acts on the bevel portion of the wafer W, whereby the polishing surface of the polishing tape 41 is pressed against the bevel portion of the wafer W. In this manner, the bevel portion of the wafer W is polished.
Next, the press pad 50 incorporated in the aforementioned polishing head 42 will be described in detail.
As shown in
The pressing surface 51a is arranged so as to face the bevel portion of the wafer W held by the wafer stage 23 (see
Since the pressing section 51 and the coupling sections 52 are deformed (bent) in this manner, the pressing surface 51a contacts the bevel portion of the wafer W over an entire length of the pressing surface 51a. Therefore, a contact length between the wafer W and the polishing tape 41 becomes longer, compared with a conventional press pad shown in
These grooves 60 serve to enable controlling of a curvature of the pressing section 51 when bent along the circumferential direction of the wafer W, and also serve to enhance the flexural rigidity of the pressing section 51 in the direction perpendicular to the surface of the wafer W. Therefore, the pressing section 51 is not compressed greatly along the vertical cross-sectional shape of the bevel portion of the wafer W, and the pressing section 51 can press the bevel portion with the flatter pressing surface 51a. The flexural strength in the circumferential direction and the vertical direction of the wafer W can be adjusted by modifying depth, shape, and the number of grooves 60 to be formed. Therefore, the press pad 50 is able to have optimum elasticity for polishing the bevel portion.
These reinforcing plates 61 serve to enable controlling of a curvature of the pressing section 51 when bent along the circumferential direction of the wafer W, and also serve to enhance the flexural rigidity of the pressing section 51 in the direction perpendicular to the surface of the wafer W. Therefore, the pressing section 51 is not compressed greatly along the shape of the bevel portion of the wafer W, and the pressing section 51 can press the bevel portion with the flatter pressing surface 51a. The flexural strength in the circumferential direction and the vertical direction of the wafer W can be adjusted by modifying thickness, material, number, and arrangement of the reinforcing plates 61 to be provided. Therefore, the press pad 50 is able to have optimum elasticity for polishing the bevel portion.
These recesses 62 serve to enable controlling of a curvature of the pressing section 51 when bent along the circumferential direction of the wafer W, and also serve to enhance the flexural rigidity of the pressing section 51 in the direction perpendicular to the surface of the wafer W. Therefore, the pressing section 51 is not compressed greatly along the shape of the bevel portion of the wafer W, and the pressing section 51 can press the bevel portion with the flatter pressing surface 51a. The press pad 50 is able to have optimum elasticity for polishing the bevel portion by modifying shape, number, and arrangement of the recesses 62 to be formed.
In this example, the pressing section 51 and the two coupling sections 52 are integrally formed, but the pad body 53 is provided as a separate member. The pressing section 51 and the two coupling sections 52 are made from rigid plastic (rigid resin), such as PVC (polyvinyl chloride). The pad body 53 is made from the same material. Edges of the respective coupling sections 52 have folded portions 52a extending inwardly, and these folded portions 52a and a rear surface of the pad body 53 are secured to each other with glue or the like.
The pad body 53 has substantially an H-shape as viewed from its front and there are clearances 54 between side surfaces of the pad body 53 and the coupling sections 52. By providing these clearances 54, the coupling sections 52 are not brought into contact with the pad body 53 when the coupling sections 52 are bent inwardly, as shown in
The pressing section 51 and the two coupling sections 52 may be made from a different material from the pad body 53. For example, the pressing section 51 and the two coupling sections 52 may be integrally formed by using a special material, such as engineering plastic, and the pad body 53 may be made from another low-cost material. These configurations make it possible to reduce a production cost. Further, the coupling sections 52 and the pad body 53 may be joined to each other with an adhesive tape, so that the pressing section 51 and the coupling sections 52 can be replaceable.
The press pad 50 thus constructed has the following advantages. As discussed above, the polishing liquid is supplied to the wafer W during polishing. This polishing liquid scatters from the wafer W due to the rotation of the wafer W, as shown in
When the polishing head 42 is oscillated in the vertical direction around the polishing position of the bevel portion of the wafer W, a contact condition between the wafer W and the polishing tape 41 changes according to a position of the oscillating polishing head 42. Specifically, a shape, a contact area, and a pressure distribution of the press pad 50 when contacting the wafer W through the polishing tape 41 vary.
In
In the polishing apparatus shown in
The present invention is applicable to a polishing apparatus for polishing a bevel portion of a substrate, such as a semiconductor wafer.
Claims
1. A polishing apparatus comprising:
- a polishing tape having a polishing surface;
- a substrate holder configured to hold and rotate a substrate;
- a press pad configured to press the polishing tape against a bevel portion of the substrate held by said substrate holder; and
- a polishing-tape feeding mechanism configured to cause the polishing tape to travel in its longitudinal direction,
- wherein said press pad includes a pad body, a plate-shaped pressing section having a pressing surface for pressing the bevel portion of the substrate through the polishing tape and having a rear surface opposite to said pressing surface, and a plurality of coupling sections coupling said pressing section to said pad body, and
- wherein a space is formed between said rear surface of said pressing section and said pad body.
2. The polishing apparatus according to claim 1, wherein said plurality of coupling sections are arranged along a circumferential direction of the substrate held by said substrate holder.
3. The polishing apparatus according to claim 1, wherein said plurality of coupling sections are connected to both sides of said pressing section.
4. The polishing apparatus according to claim 1, wherein said plurality of coupling sections are connected to said rear surface of said pressing section and located inwardly from both sides of said pressing section toward a center of said pressing section.
5. The polishing apparatus according to claim 1, wherein said rear surface of said pressing section has a plurality of grooves extending in a direction perpendicular to a surface of the substrate.
6. The polishing apparatus according to claim 1, wherein a plurality of reinforcing members, extending in a direction perpendicular to a surface of the substrate, are secured to said rear surface of said pressing section.
7. The polishing apparatus according to claim 1, wherein said rear surface of said pressing section has at least one recess extending in a circumferential direction of the substrate.
8. The polishing apparatus according to claim 1, wherein said pressing section has a shape such that a thickness thereof increases gradually from both sides of said pressing section toward a center thereof.
9. The polishing apparatus according to claim 1, wherein said pressing section is made from rigid plastic.
Type: Application
Filed: Jul 8, 2008
Publication Date: Jan 6, 2011
Inventors: Tamami Takahashi (Tokyo), Kenya Ito (Tokyo), Hiroaki Kusa (Tokyo), Masaya Seki (Tokyo)
Application Number: 12/667,901
International Classification: B24B 21/16 (20060101); B24B 21/22 (20060101);