Wafer backside protection apparatus

Details Wafer backside protection apparatus Wafer backside protection apparatus

1999-12-15

2001-04-24

Rutledge, D. (Department: 2851)

Photography

Fluid-treating apparatus

Fluid application to one side only of photographic medium

C396S627000, C118S052000, C427S240000

Reexamination Certificate

active

06220771

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a wafer backside protection apparatus and particularly to a protection apparatus that forms a protection liquid film on the wafer backside.
BACKGROUND OF THE INVENTION
In a semiconductor manufacturing process, a bare wafer has to go through hundred of processes to form integrated circuits to function as desired. The processes include coating photoresist, photo developing, depositing and etching. These processes are targeted on the front side of the wafer. Even planarization and cleaning processes focus only the front side. The wafer backside has rarely been protected. However in the processes set forth above, wafer backside also has chance being eroded by chemicals, contaminated by photoresist residuals or other exhaust particles. All this has negative impact on wafer quality and may reduce process yield.
There is a prior art disclosed in U.S. Pat. No. 5,689,749 for protecting wafer backside.
FIGS. 1 and 2
show its general structure. It includes a motor
33
, a chuck
21
and an annular seat
26
.
The motor
33
is mounted on an elevator mechanism
34
and has an output shaft
14
to provide a rotation power source. The elevator mechanism
34
may drive the motor
33
up or down.
The chuck
21
has a vacuum suction means (not shown in the figures) in the center for sucking and holding the backside of the wafer W. The annular seat
26
is located below the wafer W and surrounds the chuck
21
. On the annular seat
26
, there is mounted a water guard ring
42
which has a top rim adjacent the wafer backside. The top rim has a specially formed inner ring
40
b
and an outer ring
40
a.
In the annular seat
26
, there are also a pair of nozzles
32
symmetrically located. Outside the annular seat
26
, there is an annular chamber wall
20
. The nozzles
32
have their ejection openings facing the water guard ring
42
and may eject protection liquid (such as D.I. water). The chamber wall
20
may shield the process chamber from the outside environment.
In the process chamber above the wafer W, there are nozzle heads
23
and
31
for providing reaction agent needed for semiconductor manufacturing process.
When a robot arm (not shown in the figures) moves the wafer W into the process chamber, the elevator mechanism
34
drives the chuck
21
to suck and hold the wafer W and moves the wafer W to an initial position. The motor
33
and the output shaft
14
then drive the chuck
21
and the wafer W to rotate. The nozzle heads
23
and
31
eject reaction agent on the wafer W surface. Because of centrifugal force, the reaction agent on the water surface will be spun out. Some of the reaction agent will hit the chamber wall
20
and rebound on wafer backside.
In order to prevent the backside of the wafer W from contamination by the reaction agent, the nozzles
32
will eject protection liquid to the water guard ring
42
. As the top end of the water guard ring
26
adjacent the wafer backside, when the water guard ring
26
fills with the protection liquid and spills over, the rotating wafer W will pickup some protection liquid to form a protection liquid film around the inner ring
40
b
(or outer ring
40
a
). This liquid film may protect the wafer backside from outside contamination.
However the prior art set forth above has complex components and forms. They are difficult to produce and assemble. The production cost is higher. It also does not provide a closed process environment and is prone to contamination. Furthermore, ejection of protection liquid from the nozzles
32
requires high pressure and often results in return splashing of the protection liquid. This will weaken the suction force of the chuck
21
to the wafer W. The strong liquid impact could even break the wafer W.
In the semiconductor industry, there are some other techniques have been developed to address this issue, using gas film (such as nitrogen gas film) to fill the gap between the wafer backside and the annular seat is one of such techniques. However gas film is not effective to provide a closed process environment. There is still room for improvement regarding the issue of wafer backside protection.
SUMMARY OF THE IVNENTION
It is an object of this invention to provide a wafer backside protection apparatus that uses protection liquid film to protect wafer backside from contamination. The apparatus not only offers a closed process environment, it also may prevent the wafer from breaking. It may be used for the processes such as coating, spin drying, brush scrubber, etching, chemical mechanical polishing, vaporizing or single wafer spin cleaning and the like.
The apparatus according to this invention includes a motor, a vacuum suction chuck, an annular seat and a top cover. The motor has an output shaft for providing output rotation drive. The chuck is mounted on the motor and has a front side for sucking and holding the wafer backside. The backside of the chuck has a water guard ring and a plurality of fine slant bores running from the water guard ring to the front side of the chuck. The annular seat is located below the chuck and has two symmetrical slant nozzles for ejecting protection liquid toward the motor rotating direction at an elevation angle. The top cover covers the top of the chuck to form a closed process chamber.
In this invention, the slant nozzles continuously eject protection liquid to the water guard ring. The motor drives the chuck and wafer to rotate synchronously.
On the other hand, the nozzle slant angle is pointing to the motor rotation direction, therefore protection liquid may be ejected on the wafer backside with less return splashing and may prevent liquid waste and wafer breaking. When the nozzles continuously eject protection liquid to the water guard ring, the chuck is rotated by the motor. The centrifugal force of the water guard ring may spin protection liquid through the slant bores to the water backside to form a protection film to protect wafer backside.


REFERENCES:
patent: 5159374 (1992-10-01), Groshong
patent: 5689749 (1997-11-01), Tanaka et al.
patent: 6027602 (2000-02-01), Hung et al.

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