Abrading – Machine – Rotary tool
Reexamination Certificate
2001-10-04
2003-10-07
Nguyen, Dung Van (Department: 3723)
Abrading
Machine
Rotary tool
C451S060000
Reexamination Certificate
active
06629882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a precise polishing apparatus and a precise polishing method for polishing a substrate such as a wafer with high accuracy.
2. Related Background Art
Recently, fine arrangement and multi-layer wiring of semi-conductor devices have been progressed and, thus, there has been requested to provide precise polishing apparatuses for flattening a surface of a substrate such as a semi-conductor wafer made of Si, GaAs, InP or SOI with high accuracy. Among them, as a precise polishing apparatus for accurately flattening the surface of the substrate such as a wafer on which semi-conductor elements are formed, a chemical mechanical polishing (CMP) apparatus is known.
Conventional CMP apparatuses can be divided into two types shown in
FIGS. 10 and 11
.
(1)
FIG. 10
is a schematic view of a polishing work portion of the CMP apparatus in which the polishing (abrasion) is effected with a polished surface of a wafer
100
facing downwardly.
As shown in
FIG. 10
, the wafer
100
is held with the polished surface (surface to be polished) thereof facing downwardly, and the wafer
100
is polished by urging the wafer against a polishing pad
802
having a diameter larger than that of the wafer while rotating the wafer. During the polishing, abrasive agent (slurry) is supplied onto the polishing pad
802
.
In the apparatus of this kind, as methods for holding the wafer onto a wafer chuck
801
, vacuum suction or adhesion by using wax, solution or pure water has been adopted, and, in some cases, a guide ring (not shown) is provided on a periphery of the wafer
100
to prevent deviation of the wafer
100
. The diameter of the polishing pad
802
on a polishing table
806
is greater than that of the wafer
100
by 3 to 5 times, and suspension obtained by mixing fine powder of silicon oxide with solution of potassium hydroxide is used as the slurry.
(2) On the other hand, as shown in
FIG. 11
, there has been proposed a technique in which a wafer
100
is held on a wafer chuck
901
having a guide ring (not shown) and disposed on a wafer table
906
with a polished surface thereof facing upwardly and the wafer
100
is polished by using a polishing pad
802
having a diameter smaller than that of the wafer
100
.
In such polishing apparatus and method, the substrate such as the present semi-conductor wafer having a diameter of eight inches can be polished exclusively. However, recently, since fine arrangement of semi-conductor integrated circuits and large diameter wafers have been proposed, it is guessed that the wafer having 8-inch diameter will be replaced by a wafer having 12-inch diameter in the near future.
In order to polish the large diameter wafer, there arise the following problems in the conventional techniques.
In the conventional polishing apparatuses, although the polishing ability is adjusted by making a thickness and elasticity of the polishing pad optimum to polish the 8-inch wafer, in this case, it is difficult to ensure fine adjustment and uniformity of material of the polishing pad and, thus, it is very difficult to polish the large diameter wafer such as 12-inch wafer with high accuracy.
For example, in the conventional polishing methods, it is difficult to obtain a uniform polished amount through the entire surface of the wafer by using the polishing pad having the diameter smaller than that of the wafer. Further, if the entire polished surface of the wafer is polished by the polishing pad having the diameter smaller than that of the wafer, the polishing time will be increased considerably. Further, if the wafer is polished at once by using the polishing pad having the diameter greater than that of the wafer by twice or more, the polished amount near outer periphery of the polishing pad will become greater than the polished amount near a rotational center of the polishing pad due to difference in peripheral speed between the rotational center of the polishing pad and the outer periphery of the polishing pad.
In addition, the polishing pad may be abraded or deformed into a donut shape since a part of the polishing pad is only in contact with the wafer. The polishing pad is applied with a pressure when it polishes the wafer and the polishing pad may be deformed due to the pressure. Such matters may affect the uniformness and the flatness of the polished surface.
Further, as is in the conventional cases, when the wafer with the polished surface thereof facing downwardly is polished by opposing the polishing pad having the diameter greater than that of the wafer by twice or more to the wafer, the abrasive agent is continued to be supplied to not only an area of the polishing pad with which the wafer is contacted but also the entire area of the polishing pad. As a result, a large amount of abrasive agent is consumed, thereby making the polishing expensive.
SUMMARY OF THE INVENTION
An object of the present invention is to eliminate the above-mentioned conventional drawbacks.
To achieve the above object, according to the present invention, there is provided a precise polishing apparatus comprising polished body holding means for holding a polished body with a polished surface thereof facing upwardly and for rotating the polished body around a center of the polished surface, a polishing head for holding a polishing pad having a diameter greater than a diameter of the polished body with a polishing surface thereof facing downwardly and for rotating the polishing pad around a center of the polishing surface, and a supply opening provided in the polishing head and adapted to supply abrasive agent to the polished surface via the polishing pad, and wherein the polishing is effected in conditions that a rotation axis of the polished body is deviated from a rotation axis of the polishing pad and that the polishing pad is contacted with an entire area of the polished surface of the polished body.
The present invention further provides a precise polishing apparatus comprising polished body holding means for holding a polished body with a polished surface thereof facing upwardly and for rotating the polished body around a center of the polished surface, a polishing head for holding a polishing pad having a diameter greater than a diameter of the polished body with a polishing surface thereof facing downwardly and for rotating the polishing pad around a center of the polishing surface, and a supply opening provided in the polishing head and adapted to supply abrasive agent to the polished surface via the polishing pad, and wherein the polished body holding means includes a drive means for oscillating the polished body in directions along the polished surface, and a sum of a maximum value of a distance between the center of the polished surface and the center of the polishing surface of the polishing pad generated due to the oscillation and a radius of the polished body is selected to become smaller than a radius of the polishing pad.
The present invention further provides a precise polishing apparatus comprising polished body holding means for holding a polished body with a polished surface thereof facing upwardly and for rotating the polished body around a center of the polished surface, a polishing head for holding a polishing pad having a diameter greater than a diameter of the polished body with a polishing surface thereof facing downwardly and for rotating the polishing pad around a center of the polishing surface, and a supply opening provided in the polishing head and adapted to supply abrasive agent to the polished surface via the polishing pad, and wherein the polishing head includes a drive means for oscillating the polished body in directions along the polished surface, and a sum of a maximum value of a distance between the center of the polished surface and the center of the polishing surface of the polishing pad generated due to the oscillation and a radius of the polished body is selected to become smaller than a radius of the polishing pad.
The present invention further provides a precise polishi
Ban Mikichi
Kamono Takashi
Nishimura Matsuomi
Takahashi Kazuo
Uchiyama Shinzo
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