JPH0992710A - Polishing method for thin planar substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for polishing the entire surface of a semiconductor wafer uniformly with extremely high accuracy using a substrate holding plate comprising a vacuum chuck employing a porous plate. SOLUTION: The polishing method employs a polishing unit 1 comprising a rotary polishing surface plate 2, and a substrate holding plate 5 comprising a porous plate 5A for holding a semiconductor wafer S to be polished in parallel with the polishing face of the polishing surface plate 2 through vacuum suction. A large number of vents are made relatively uniformly in the surface 5D of the porous plate 5A provided with micropores and the semiconductor wafer S is polished while being sucked through an elastic pad 7 having uniform thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a thin plate-like substrate such as a semiconductor wafer or a glass plate for LCD, and particularly to a thin plate-like substrate polished so as to prevent uneven polishing. It is characterized in that the method of holding the substrate is improved.

[0002]

2. Description of the Related Art First, a polishing apparatus for a thin plate substrate in use (hereinafter simply referred to as "polishing apparatus") will be described with reference to FIG. FIG. 3 is a cross-sectional view schematically showing a part of a current polishing apparatus.

One of the currently used polishing apparatuses used for polishing a thin plate substrate, for example, a semiconductor wafer (hereinafter, "semiconductor wafer" will be described as an example of the thin plate substrate to be polished) is used. There is a polishing apparatus 1 using a vacuum chuck device having a structure as shown in FIG. The polishing apparatus 1 is roughly composed of a polishing surface plate 2, a substrate holding plate 5, and a nozzle 8.

The polishing platen 2 has, for example, a flat surface having an area having a diameter twice or more the diameter of the semiconductor wafer S,
A polishing pad 3 made of, for example, a non-woven fabric made of polyester resin is attached to the plane with an adhesive or the like, and is configured to rotate about the rotation shaft 4 at, for example, 30 rpm.

The substrate holding plate 5 is located above the polishing platen 2 and is rotated from the rotation axis 4 of the polishing platen 2, for example, the center of rotation is at the center of the radius of the polishing platen 2. The number of revolutions of the polishing platen 2 about the axis 6 is equal to 30.
It is configured to rotate at rpm. The substrate holding board 5 uses a vacuum chuck device as a substrate holding means for holding the semiconductor wafer S. This vacuum chuck device hermetically seals the disk-shaped porous plate 5A having a suction surface (hereinafter, simply referred to as "suction surface") 5D for sucking the back surface of the semiconductor wafer S formed on the lower surface and the circumferential surface. Further, it comprises a cylindrical seal frame 5B for supporting, an intake port 5C opened at the center of the rotary shaft 6, a suction pump (not shown) connected to this intake port 5C, and the like. The nozzle 8 supplies the polishing liquid L between the polishing pad 3 and the semiconductor wafer S near the center of rotation of the polishing platen 2.
In FIG. 3, only the right half of the polishing platen 2 is shown for convenience.

When polishing the semiconductor wafer S using the polishing apparatus 1, a suction pump (not shown) is operated to make the surface to be polished of the semiconductor wafer S to be polished face the polishing pad 3 surface, and the rear surface thereof. Is vacuum-sucked and held by the flat suction surface 5D, and in this holding state, the substrate holding plate 5 is rotated and lowered, and the semiconductor wafer S is rotated at the number of rotations. The surface to be polished of the semiconductor wafer S is chemically mechanically polished by the polishing pad 3 and the polishing liquid L (hereinafter , Abbreviated as “polishing”).

[0007]

When the semiconductor wafer S is sucked and held by using the substrate holding plate 5 constituted by such a vacuum chuck device, the warp of the semiconductor wafer S is corrected by vacuum suction and the flat state is obtained. Can be held at. However, as the porous plate 5A, for example, a porous ceramic material is used.
Generally, the sizes of the diameters of a large number of through-holes that are opened in the suction surface 5D vary depending on manufacturing restrictions. The diameters of the through holes vary over a range of two digits or more, such as about 1 to 300 μm. Therefore, assuming that the semiconductor wafer S is sucked, held and polished by using the substrate holding plate 5 having the porous plate 5A having the suction surface 5D having such a surface texture, a large opening is formed on the suction surface 5D. In the vicinity of the through hole, dimples (recesses) and hillocks (projections) are locally generated on the surface of the held semiconductor wafer S,
For this reason, there is a problem in that the surface to be polished of the semiconductor wafer S is unevenly polished and sometimes damaged.

The present invention is intended to solve the above-mentioned problems, and even when a substrate holding plate composed of a vacuum chuck device using the porous plate is used, the surface to be polished of a semiconductor wafer is It is an object of the present invention to obtain a method for polishing a thin plate-like substrate capable of polishing the entire surface uniformly and in a uniform thickness with extremely high accuracy.

[0009]

Therefore, according to the polishing method of the present invention, a thin plate-shaped substrate, which comprises a rotary polishing platen and a main body made of a porous plate, and is intended to polish the polishing surface of the rotary polishing platen. When polishing the thin plate-shaped substrate using a thin plate-shaped substrate polishing device configured to hold the substrate in parallel by vacuum suction, the thin plate-shaped substrate suction surface of the porous plate is relatively uniform. The above-described problems are solved by adopting a method of polishing the adsorbed thin plate-shaped substrate while vacuum-sucking the thin plate-shaped substrate through an elastic pad having a large number of different ventilation holes and having a uniform thickness. are doing.

Therefore, according to the polishing method of the present invention, by interposing the elastic pad, adverse effects such as dimples and hillocks on the semiconductor wafer due to the surface texture of the suction surface of the porous plate can be prevented, and the semiconductor The surface to be polished of the wafer can be highly accurately and uniformly polished within the surface, and the elastic function of the elastic pad plays the role of cushioning the shock even if the polishing platen slightly shakes, reducing damage to the semiconductor wafer. can do.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polishing method of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view for explaining a polishing method of the present invention for polishing a semiconductor wafer using an existing polishing apparatus, and FIG. 2 is a plan view showing a structure of an elastic pad used in the polishing method of the present invention. .

First, with reference to FIG. 2, an elastic pad 7 used when the semiconductor wafer is sucked and held by the substrate holding plate 5 in the polishing method of the present invention will be described. The elastic pad 7 is made of polyester resin, polyurethane resin or the like having a thickness of 10 to 1000 μm and has a caliber of 0.1 to 0.1 μm.
Through hole 7 with the same diameter as possible within the range of 100 μm
It is made of a sheet with many A's opened uniformly. Regarding the elasticity of the elastic pad 7, if the elasticity is too large, it becomes difficult to uniformly polish the semiconductor wafer S to be polished within its surface. It is better to be hard, but it is necessary to have elasticity capable of absorbing the unevenness of the suction surface 5D of the porous plate 5A.

The elastic pad 7 having such a structure is mounted on the suction surface 5D of the substrate holding plate 5. In this mounting, the end face forming the same surface as the suction face 5D of the seal frame 5B is bonded with an adhesive, and the elastic sheet is cut into a circular shape along the outer diameter of the seal frame 5B. In this way, the substrate suction surface of the substrate holding plate 5 with the elastic pad 7 attached is located on the side where the semiconductor wafer S shown in FIG. 1 is in contact with the suction surface 5D of the porous plate 5A shown in FIG. It becomes the plane 7B of the elastic pad 7.

According to the polishing method of the present invention, the elastic pad 7 is attached to the suction surface 5D of the porous plate 5A constituting the substrate holding plate 5 in this way, and a vacuum pump (not shown) is operated,
The semiconductor wafer S to be polished is vacuum-sucked and held. As described above, since the elastic pad 7 is provided with a large number of minute through holes 7A, it becomes a part of the porous plate 5A, and ventilation is possible, so that the semiconductor wafer S is sucked and held as described above. be able to.

The semiconductor wafer S sucked and held is flattened and held by vacuum suction even if there is a warp, and is held and rotated in the flat state on the polishing platen 2. The surface to be polished is polished while applying a predetermined pressing force to the rotating surface of the polishing pad 3.

[0016]

When the polishing method of the present invention as described above is adopted, since the elastic pad is interposed between the porous plate and the semiconductor wafer constituting the vacuum chuck device, it is porous. It is possible to prevent adverse effects such as dimples and hillocks on the semiconductor wafer due to the surface texture of the suction surface of the plate. Further, due to the elastic function of the elastic pad, even if the polishing platen 2 is shaken to some extent, it can play a role of cushioning the impact and reduce damage to the semiconductor wafer. Therefore, the surface to be polished of the semiconductor wafer can be highly accurately and uniformly polished in the surface only by using a very simple and inexpensive means.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a part of a polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing the structure of an elastic pad used in the polishing method of the present invention.

FIG. 3 is a schematic cross-sectional view of a part of a current polishing apparatus.

[Explanation of symbols]

 1 Current polishing device for thin plate substrate 2 Polishing surface plate 3 Polishing pad 5 Substrate holding plate 5A Porous plate 5B Seal frame 5C Inlet port 5D Suction surface 7 Elastic pad 7A Through hole 7B Suction surface 8 Nozzle S Thin plate substrate (semiconductor substrate Wafer)

Claims (1)

[Claims] 1. A rotary polishing platen, and a substrate holding plate which has a main body made of a porous plate and holds a thin plate-like substrate to be polished against a polishing surface of the rotary polishing platen in a parallel state by vacuum suction. When polishing the thin plate-shaped substrate using a thin plate-shaped substrate polishing apparatus composed of, a relatively uniform number of ventilation holes are formed in the thin plate-shaped substrate suction surface of the porous plate, and uniform. A method for polishing a thin plate-shaped substrate, which comprises polishing the adsorbed thin plate-shaped substrate while vacuum-sucking the thin plate-shaped substrate through an elastic pad having a different thickness.