Wafer cleaning apparatus

Details Wafer cleaning apparatus Wafer cleaning apparatus

2001-01-12

2002-01-01

Chin, Randall E. (Department: 1744)

Brushing, scrubbing, and general cleaning

Machines

Brushing

C015S088200, C015S102000

Reexamination Certificate

active

06334230

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to semiconductor processing, and more particularly to an improved apparatus for cleaning semiconductor wafers.
BACKGROUND OF THE INVENTION
Wafer cleaning is an essential process in the manufacture of semiconductor devices. A number of other processes (notably chemical-mechanical polishing or CMP) leave residues on the wafer surface; such residues must be removed as completely as possible before further processing can be performed.
Two broad categories of wafer cleaning apparatus may be characterized as “roller-type” and “pencil-type.” A typical roller-type wafer cleaning apparatus (shown, for example, in U.S. Pat. Nos. 5,937,469 and 5,976,267) includes a roller with a brush parallel to the wafer surface and extending across the wafer; the roller turns on its axis while the wafer rotates underneath it. A pencil-type cleaning apparatus, on the other hand, has a cleaning head mounted on a shaft which is perpendicular to the wafer surface and can move radially across the surface.
A typical pencil-type wafer cleaner is shown schematically in FIG.
1
. The wafer
1
, only the outer portion of which is shown, is mounted in a wafer chuck
2
. The wafer chuck is generally connected to a shaft (not shown) for spinning the wafer at high speed, in order to facilitate rapid and thorough drying of the wafer. While the details of the wafer chuck design vary between cleaning tools, it should be noted that there is in general a portion
2
a
of the wafer chuck above the plane of the wafer surface being cleaned.
The pencil-type wafer cleaner
10
includes a cleaning head
11
connected to a shaft
12
. The portion
11
a
of the cleaning head in contact with the wafer is approximately hemispherical in shape. This portion, at least, has a brush, sponge or the like for removing foreign material from the wafer surface. Shaft
12
is connected to a mechanism (not shown) which moves the wafer cleaner
10
in the radial direction. The wafer is thus efficiently cleaned as the cleaning head moves radially across the surface of the spinning wafer.
However, as shown in
FIG. 1
, the arrangement of head
11
and wafer chuck
2
can prevent the complete cleaning of the wafer. Mechanical interference between the cleaning head
11
and the wafer chuck
2
(at contact point
2
c
shown in
FIG. 1
) results in the point of cleaning contact
11
p
lying some radial distance inward from the edge of the wafer. An annular uncleaned region
1
e
thus remains near the edge of the wafer. This problem is commonly termed “edge exclusion.”
It is possible to rotate the wafer by using rollers engaging the edge of the wafer; these rollers leave most of the area exposed, so that the cleaning head
11
may move unimpeded to the wafer edge (see U.S. Pat. No. 5,937,469 and Japanese patent publication JP 11-97397). However, such wafer edge rollers generally cannot spin the wafer at a high speed as is required for fast drying.
There remains a need for a pencil-type wafer cleaner which permits center-to-edge and edge-to-edge cleaning without edge exclusion, and which is compatible with a variety of wafer chuck arrangements.
SUMMARY OF THE INVENTION
The present invention addresses the above-described need by providing an apparatus for cleaning a surface of a wafer without edge exclusion. The apparatus includes a wafer holding mechanism with a portion contacting the outer edge of the wafer and having a surface substantially planar with the wafer surface. The apparatus further includes a wafer cleaning head including a wafer cleaning element; the wafer cleaning element has a flat surface contacting the wafer surface when cleaning the wafer. A portion of the wafer cleaning element overlies the above-mentioned surface of the wafer holding mechanism when cleaning the edge portion of the wafer. The wafer holding mechanism and wafer cleaning head are shaped to avoid mechanical interference therebetween when the edge portion of the wafer is cleaned.
The wafer cleaning element may be a brush, a sponge, or other suitable material.
As part of a pencil-type wafer cleaner, the apparatus also includes a shaft connected to the wafer cleaning head, the axis of the shaft being substantially perpendicular to the wafer surface.


REFERENCES:
patent: 5901399 (1999-05-01), Moinpour et al.
patent: 5911257 (1999-06-01), Morikawa et al.
patent: 5937469 (1999-08-01), Culkins et al.
patent: 5976267 (1999-11-01), Culkins et al.
patent: 11097397 (1999-04-01), None

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