Abrading – Machine – Rotary tool
Reexamination Certificate
2000-02-15
2002-07-30
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Rotary tool
C451S041000
Reexamination Certificate
active
06425809
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polishing apparatus for polishing a plate-like article such as a semiconductor wafer.
With recent rapid progress in technology for fabricating high-integration semiconductor devices, circuit wiring patterns have been becoming increasingly fine, with spaces between wiring patterns also decreasing. As wiring spacing decreases to a level less than 0.5 microns, the depth of focus in circuit pattern formation in photolithography and the like becomes shallower. Accordingly, surfaces of semiconductor wafers on which circuit pattern images are to be formed by a stepper are required to be polished by a polishing apparatus to have an exceptionally high degree of surface flatness.
FIG. 1
shows a conventional polishing apparatus for making the surface of a semiconductor wafer flat. The apparatus includes a turntable
101
provided with a polishing cloth
102
on the upper surface thereof, a wafer carrier
105
for carrying a semiconductor wafer
103
to be polished and an abrasive liquid supply nozzle
108
for supplying an abrasive liquid Q onto the polishing surface. The wafer carrier
105
is drivingly connected to a rotatable drive shaft
109
and is provided on its lower surface with a resilient backing member
107
formed from polyurethane or the like so that the semiconductor wafer
103
is supported on the backing member
107
with the entire upper surface of the semiconductor wafer engaged with the backing member
107
.
Further, the wafer carrier
105
is provided therearound with a guide ring
106
to prevent the wafer
103
from becoming disengaged from the lower surface of the backing member
107
. The guide ring
106
is fixedly secured to the wafer carrier with the lower surface of the guide ring
106
positioned at a lower level relative to the lower surface of the baking member
107
, whereby the semiconductor wafer
103
is securely held under the lower surface of the backing member.
During a polishing operation, the wafer carrier
105
holds the wafer
103
on the lower surface of the backing member
107
and presses it against the polishing cloth
102
on the turntable
101
while the wafer carrier
105
and the turntable
101
are turned about their axes, respectively. Simultaneously, the abrasive liquid nozzle
108
supplies an abrasive liquid Q on the polishing cloth
102
. The abrasive liquid consists of, for example, an alkaline slurry containing abrasive particles which chemically and mechanically polishes the semiconductor wafer by means of both the alkali and the abrasive particles.
Since, in such a conventional polishing apparatus, the semiconductor wafer
103
is engaged across its area with the backing member
107
when subjected to the polishing operation, the semiconductor wafer is readily affected by inconsistencies in the hardness of the backing member
107
, thereby making it difficult for the semiconductor wafer
103
to be polished uniformly.
Further, since the polishing cloth provided on the turntable
101
is formed from a resilient member such as IC1000/SUBA400(IC1000 with 1,000 punched holes) produced by Rodel Nitta Corp., when the polishing cloth
102
is disengaged from the semiconductor wafer
103
the polishing cloth tends to rebound or spring back against the wafer, whereby an edge of the semiconductor wafer comes into engagement with a portion of the polishing cloth under a strong pressure, resulting, as shown in
FIG. 2
, in excessive polishing.
FIG. 3
is a graph showing the thickness A of an oxide layer of a 6 inch diameter semiconductor wafer polished by a conventional polishing apparatus, which thickness was measured at a number of points along a radius of the semiconductor wafer, and pressures B imposed on the semiconductor wafer at points on the radius during polishing of the semiconductor wafer. The values of the pressures were calculated through the so-called finite element method. It can be noted from the graph that the values denoting the pressures generally correspond to the values denoting the thickness of the oxide layer. It has been confirmed that a similar tendency exists with respect to a semiconductor wafer having an 8 inch diameter in terms of the above-stated oxide layer thickness and pressures.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide a polishing apparatus whereby a plate-like article such as a semiconductor wafer is polished to have a uniformly high degree of flatness.
According to the present invention, a polishing apparatus comprises a turntable having a flat surface, and a flat polishing pad provided on the flat surface of the turntable. The polishing pad has a polishing surface provided with grooves formed therein to divide the polishing surface into a number of sections. The apparatus further comprises an article carrier having an article holding surface for holding thereon a plate-like article having a surface to be polished. The carrier is adapted to press the surface of the plate-like article against the polishing surface of the polishing pad and to polish and flatten the surface of the plate-like article by relative movement between the article and the polishing surface. An annular member is positioned between the article holding surface and the plate-like article to form a chamber defined by the annular member, the article holding surface and the plate-like article, and a pressure control system is fluidly connected to the chamber for controlling pressure in the chamber. The annular member may be positioned along the peripheral edge of the plate-like article. The grooves may be arranged in a grid-like pattern.
The plate-like article is pressed against the polishing surface under a pressure exerted by the pressurized fluid while pressing the plate-like article against the polishing surface through the annular member.
The annular member may have a width in a range of from 10 mm to 20 mm. According to another aspect of the present invention, a polishing apparatus comprises a turntable having a surface, and a polishing pad provided on the surface of the turntable. The polishing pad has a polishing surface. The apparatus further comprises an article carrier having an article holding surface for holding thereon a plate-like article having a surface to be polished. The carrier is adapted to press the surface of the plate-like article against the polishing surface of the polishing pad and to polish and flatten the surface of the plate-like article by relative movement between the article and the polishing surface. An annular member is positioned between the article holding surface and the plate-like article to form a chamber defined by the annular member, the article holding surface and the plate-like article. The annular member has a width in the range of from 10 mm to 20 mm, and a pressure control system is fluidly connected to the chamber for controlling the pressure in the chamber. The annular member may be positioned along the peripheral edge of the plate-like article.
According to a further aspect of this invention, a polishing apparatus comprises a turntable having a surface, and a polishing pad provided on the flat surface of the turntable. The polishing pad has a polishing surface. The apparatus further comprises an article carrier having an article holding surface for holding thereon a plate-like article having a surface to be polished. The carrier is adapted to press the surface of the plate-like article against the polishing surface of the polishing pad and to polish and flatten the surface of the plate-like article by relative movement between the article and the polishing surface. An outer member in the shape of a ring is placed between the article holding surface and the plate-like article to form a chamber defined by the outer member, the article holding surface and the plate-like article, and an inner member is positioned inwardly of the outer member between the article holding surface and the plate-like article to divide the chamber into a plurality of chamber sections separated from each other.
Ebara Corporation
Hail III Joseph J.
Thomas David B.
Wenderoth , Lind & Ponack, L.L.P.
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