Abrading – Precision device or process - or with condition responsive... – With indicating
Reexamination Certificate
1998-03-19
2001-10-09
Eley, Timothy V. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
With indicating
C451S041000, C451S060000, C451S271000, C451S290000
Reexamination Certificate
active
06299506
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 progressed, and, thus, there is a need to provide precise polishing apparatuses for accurately flattening a surface of a semi-conductor wafer made of Si, GaAs, InP or SOI or a glass or quartz substrate (so-called element substrate) having a transistor. 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. 7 and 8
.
(1)
FIG. 7
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. 7
, 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
502
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
502
.
In the apparatus of this kind, holding the wafer onto a wafer chuck
501
by using vacuum suction or adhesion by using wax, solution or pure water have been adopted. Additionally, in some cases a guide ring is provided on a periphery of the wafer
100
to prevent deviation of the wafer
100
. The diameter of the polishing pad
502
on a polishing table
506
is greater than that of the wafer
100
by 3-5 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. 8
, there has been proposed a technique in which a wafer
100
is held on a wafer chuck
601
having a guide ring and disposed on a wafer table
606
with a polished surface thereof facing upwardly and the wafer
100
is polished by using a polishing pad
602
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.
However, in such 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 a 12-inch wafer with high accuracy.
In order to solve the above problem, it is considered that the entire surface of the wafer is firstly polished by using a rough polishing pad, and, then, a desired portion of the wafer is polished selectively or preferentially to obtain a desired wafer surface.
However, in order to polish the large diameter wafer (having the diameter of 8 inch or more), there arises the following problem in the conventional techniques.
In the conventional polishing apparatuses and methods using a polishing tool greater than the wafer, a portion of the wafer which could not be made uniform is very hard to be made more uniform or be further flattened by using the same method. Further, in a system in which a polishing tool smaller than the wafer is used and scan is effected while oscillating the rotating polishing tool or in a system in which a polishing tool smaller than the wafer is used and scan is effected while revolving the rotating polishing tool within a radius range greater than a radius of the tool and oscillating the tool, although a desired portion of the wafer can be polished selectively or preferentially, pitch unevenness due to the scan is apt to be generated, and, it is difficult to correct such pitch unevenness with high accuracy and to make the wafer surface uniform and to flatten the wafer surface. Also in a system, as disclosed in U.S. Pat. No. 4,128,968, in which a rotating and revolving tool having a sectional configuration of the polishing becoming maximum around a revolution axis and gradually decreasing toward the periphery is used, although a desired portion of the wafer can be polished selectively or preferentially, pitch unevenness due to the scan is apt to be generated, and, it is difficult to correct such pitch unevenness with high accuracy and to make the wafer surface uniform and to flatten the wafer surface.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a polishing apparatus and a polishing method, in which a large area substrate can be corrected and polished with high accuracy.
A second object of the present invention is to provide a polishing apparatus and a polishing method, in which a desired portion of a wafer can be corrected selectively or preferentially with high accuracy by using a tool (polishing pad) smaller than the wafer to make the wafer more uniform and to further flatten the wafer.
To achieve the above objects, according to the present invention, there is provided a polishing apparatus comprising a holding means for holding a polished body with a polished surface thereof facing upwardly, and a polishing head for holding a polishing pad having a polishing surface having an area smaller than an area of the polished surface while contacting the polishing pad with the polished surface and for rotating the polishing pad around its rotation axis, and wherein the polishing head is provided with a drive means for revolving the polishing pad around a revolution axis, and the revolution axis and the rotation axis are positioned so that a distance between the revolution axis and the rotation axis is smaller than a radius of the polishing pad.
In the polishing apparatus, the holding means can be rotated.
In the polishing apparatus, the revolution axis of the polishing head can be shifted along the polished surface.
In the polishing apparatus, the revolution axis may be shifted to a predetermined position of the polished body in accordance with a surface configuration of the polished body.
In the polishing apparatus, the revolution axis of the polishing head may be shifted to a predetermined position of the polished body in accordance with a surface configuration of the polished body, by rotation of the holding means and by shifting movement of the revolution axis.
In the polishing apparatus, the polishing head may include a detection head for detecting the surface configuration of the polished body.
In the polishing apparatus, the polishing head may include a variable means for varying a distance between the revolution axis and the rotation axis.
In the polishing apparatus, the polishing head may have a supply passage for supplying abrasive agent through the polishing pad.
The present invention further provides a polishing method in which a polished body is rested on a holding means with a polished surface thereof facing upwardly and the polished surface is polished by rotating a polishing pad having a polishing surface having an area smaller than an area of the polished surface while contacting the polishing pad with the polished surface, comprising the steps of rotating the polishing pad around the rotation axis, and revolving the polishing pad around the revolution axis positioned so that a distance between the revolution axis and the rotation axis becomes smaller than a radius of the polishing pad.
The polishing method may further comprise a step of shifting the revolution axis to a predetermined position of the polished body in accordance with
Ikeda Osamu
Nishimura Matsuomi
Ohta Satoshi
Uchiyama Shinzo
Canon Kabushiki Kaisha
Eley Timothy V.
Fitzpatrick ,Cella, Harper & Scinto
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