Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Utility Patent
1998-12-04
2001-01-02
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C451S287000
Utility Patent
active
06168684
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a wafer polishing apparatus and a polishing method. More particularly, the invention relates to a wafer polishing apparatus and a polishing method applicable for a chemical and mechanical polishing for planarization of an uneven portion on a semiconductor wafer formed through a semiconductor device fabrication process.
2. Description of the Related Art
FIG. 10
shows a graph showing a shape after polishing of an outer peripheral portion of a wafer in the case where chemical and mechanical polishing for planarization of an uneven portion on a semiconductor wafer formed through a semiconductor device fabrication process. In
FIG. 10
, a horizontal axis represents a position in a radial direction from an outer peripheral portion of the wafer toward the center, and a vertical axis represents a residual layer thickness of the wafer.
Typically, a wafer polishing apparatus performs chemical and mechanical polishing supplies an abrasives to a rotating abrasive cloth and performs polishing by pressing the abrasive cloth onto the wafer. In this case, a ring called as retainer for preventing the wafer from jumping out during polishing process, is arranged for surrounding the wafer. In
FIG. 10
, a curve represented by (a) shows a shape of wafer in the case where the retainer does not contact with the polishing cloth. In general, the shape of the outer peripheral portion of the wafer after polishing is a shape in the case where the retainer is pressed onto the polishing cloth. A curve represented by (b) shows a shape of wafer in the case where the retainer is in contact with the abrasive-cloth. In general, the shape of the outer peripheral portion of the wafer after polishing is differentiated depending upon whether the retainer is pressed onto the abrasive cloth or not. It has been known that better or higher flatness can be obtained as shown by the curve of (a) in FIG.
10
.
In the semiconductor fabrication process, an amount of the semiconductor chips obtained from a single wafer (hereinafter referred to as yield) depends upon an area of a flat region of the wafer. In case of the curve shown by (a) of
FIG. 10
, namely in the case where the retainer is pressed onto the abrasive cloth, higher flatness can be obtained in the outer peripheral portion of the wafer to achieve higher yield from one wafer to lower fabrication cost. Accordingly, in view of this, it is advantageous to press the retainer on the abrasive cloth in view point of the fabrication process. However, in this case, since the retainer surrounds the wafer, when the lower surface of the retainer is flat, supply of the abrasives to a polishing surface of the wafer is interfered to lower a polishing speed or to case lack of polishing at the center portion of the wafer.
A polishing apparatus solving the problems set forth above has been disclosed in Japanese Unexamined Patent Publication No. Heisei 7-237120.
The wafer polishing apparatus disclosed in the above-identified Japanese Unexamined Patent Publication No. Heisei 7-237120 will be discussed with reference to FIG.
9
.
The wafer polishing apparatus shown in
FIG. 9
is constructed with a rotatable polishing bed
52
, an abrasive cloth
3
provided on the polishing bed, an abrasives supply portion
5
supplying an abrasives
4
on the surface of the abrasive cloth
3
by means of a pump or the like, a carrier head
6
holding a wafer
1
as an object of polishing, a retainer
9
surrounding the wafer
1
, fixed to the carrier head
6
in so as to be placed at a height to depress the abrasive cloth
3
around the wafer
1
during polishing and provided with a plurality of grooves
10
on the surface contacting with the abrasive cloth
3
, a pressurizing mechanism
14
depressing the wafer
1
and the retainer
9
toward the abrasive cloth
3
together with the carrier head
6
, and a spindle
13
driving the wafer
1
and the retainer
9
on the abrasive cloth
3
together with the carrier head
6
.
The conventional wafer polishing apparatus shown in FIG.
9
supplies the abrasives
4
to the rotating abrasive cloth
3
and performs polishing by rotating the spindle
13
with depressing the wafer
1
onto the abrasive cloth
3
by means of the pressurizing mechanism
14
, similarly to the typical apparatus for performing chemical and mechanical polishing. At this time, since the retainer
9
is also depressed onto the abrasive cloth
3
, good flatness can be obtained on the outer peripheral portion of the wafer
1
as shown in FIG.
10
(
a
) to increase yield. On the other hand, since a plurality of grooves are provided on the retainer
8
, the abrasives
4
is supplied to the polishing surface of the wafer through these grooves
10
to solve the problem of lowering of the polishing speed and lacking of polishing at the center portion of the wafer
1
.
However, such conventional wafer polishing apparatus still remains a problem in synchronous rotation of the wafer and the retainer via the carrier head.
Namely, the conventional wafer polishing apparatus can differentiate inflow amount of the abrasives at portions where the grooves are formed and portions where the grooves are not formed for synchronous rotation of the wafer and retainer to cause fluctuation of polishing amount in the circumferential direction of the wafer and correspondingly cause lowering of the yield.
On the other hand, the conventional wafer polishing apparatus cannot control supply and discharge of the abrasives to the wafer polishing surface. A polishing chip and reaction product generated according to progress of polishing can be accumulated below the wafer polishing surface. By this, scratching of the wafer surface and lowering of the polishing speed can be caused.
SUMMARY OF THE INVENTION
The present invention has been worked out in view of the problems in the prior art. Therefore, it is an object of the present invention to provide a wafer polishing apparatus and a polishing method which can increase yield with eliminating fluctuation of polishing amount and can prevent occurrence of scratching and lowering of polishing speed by accumulation of reaction products.
According to the first aspect of the present invention, a wafer polishing apparatus comprises:
a rotary polishing bed;
an abrasive cloth provided on the polishing bed;
abrasives supplying means for supplying an abrasives to a surface of the abrasive cloth;
wafer depressing means for depressing the wafer onto the abrasive cloth at a predetermined pressure;
a ring shaped retainer arranged surrounding the wafer and provided with a plurality of grooves extending between an inner peripheral edge and an outer peripheral edge on a surface contacting with the abrasive cloth;
rotary driving means for driving the wafer and the retainer on the abrasive cloth; and
rotation speed difference generating means for providing a difference of rotation speeds between the wafer and the retainer.
According to the second aspect of the present invention, a wafer polishing method comprises the steps of:
supplying an abrasives to a surface of an abrasive cloth provided on a rotary polishing bed;
driving a wafer as an object for polishing and a retainer arranged surrounding the wafer for rotation with depressing the wafer onto the abrasive cloth at a predetermined pressure by the retainer; and
causing a difference of rotation speeds of the wafer and the retainer.
According to the third aspect of the present invention, a wafer polishing method comprises the steps of:
supplying an abrasives to a surface of an abrasive cloth provided on a rotary polishing bed;
driving a wafer as an object for polishing and a retainer arranged surrounding the wafer for rotation with depressing the wafer onto the abrasive cloth at a predetermined pressure by the retainer, in which the abrasives is supplied to a surface of the wafer to be polished in one rotating direction of the wafer and the retainer, and the abrasive is discharged from the surface of the wafer to be polished in the other ro
Inaba Shoichi
Mitsuhashi Hideo
Ohi Satoshi
Yamamori Atsushi
Mills Gregory
NEC Corporation
Powell Alva C.
Young & Thompson
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