Abrading – Accessory – Guard or housing
Reexamination Certificate
2000-01-31
2001-01-23
Rose, Robert A. (Department: 3723)
Abrading
Accessory
Guard or housing
C451S388000
Reexamination Certificate
active
06176770
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a grindstone in a pin chuck stepper. More particularly, the present invention relates to a grindstone having a vacuum system in a pin chuck stepper.
2. Description of the Related Art
In a semiconductor process, a semiconductor wafer is fixed on a stage of a stepper in order to obtain a desired pattern on the semiconductor wafer through an exposure and development process. This is known as a photolithography process. Conventionally, the stage of the stepper is a ring-type stage, and the ring is a continuous coil. However, the semiconductor wafer cannot be horizontally placed on the ring while the particles produced during processes stick on the surface of the ring. As a result, the light cannot be precisely focused on the semiconductor wafer, and the quality of photolithography is seriously affected. Conventionally, such a situation can be prevented by using a particle-free cloth and alcohol to clean the surface of the stage.
The problem of the particles sticking on the surface of the ring stage can be minimized by decreasing the surface area on which the particles can stick. Thus, a pin chuck stage is introduced to a stepper.
FIG. 1A
is a schematic, cross-sectional view showing a pin chuck stage, and showing a problem resulting from the introduction of the pin chuck stage according to the prior art.
Referring to
FIG. 1A. a
pin chuck stage
12
is introduced to a stepper to decrease the surface area on which the particles
16
can stick, which is possible because the surface areas of the pins
14
are much smaller than that of the ring. However, it is impossible to totally prevent the particles from sticking to the tiny areas of the pins
14
. Thus, a smooth ceramic grindstone
10
is used to sweep the particles
16
from the surfaces of the pins
14
by pushing the particles
16
into gaps
15
between pins
14
as shown in FIG.
1
A. However, the particles
16
can lift and stick on the surfaces of the pins
14
again while the stage is moving or the air is flowing. Furthermore, the pin chuck stage
12
cannot be cleaned with a particle free cloth and alcohol because fibers of the cloth may entangle with the pins and damage the pin chuck stage
12
.
In addition, the particles
16
can be easily accumulated in the dead space
20
between the stage
12
and the pre-alignment element
18
, as shown in
FIG. 1B
, because of the motion of the grindstone
10
. In fact, the particle contamination mainly results in the particles sticking in the dead space
20
in a photolithography process, and it is very difficult to get rid of the particles stuck in the dead space
20
. This is a problem difficult to overcome while using a pin chuck stage in a stepper.
SUMMARY OF THE INVENTION
According to above, the invention provides a grindstone having a vacuum system in a pin chuck stepper to vacuum particles while the grindstone is sweeping the particles away.
The vacuum system comprises a two-layer ring tube and is attached on the edge of the grindstone. The two-layer ring tube comprises a continuous ring upper tube having a joint connected to a vacuum motor and a plurality of sausage-shaped lower tubes wherein the ring upper tube communicates with the plurality of sausage-shaped lower tubes. The sausage-shaped lower tubes are separated from each other by a space which can include a pre-alignment element, and there is a plurality of openings for inhaling particles into the stage on bottoms of the sausage-shaped lower tubes. The vacuum system is activated while the grindstone is moving on the pin chuck stage; thus particles can be inhaled by the vacuum system while the particles are pushed into gaps between pins on the pin chuck stage by the grindstone. In addition, when the grindstone is moved to a pre-alignment element, since there is a space between the sausage-shaped lower tubes, the pre-alignment element is wedged in the space between the sausage-shaped lower tubes. Then, the particles stuck in the dead space between the chuck and the pre-alignment element can be easily inhaled by the vacuum system.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 4213698 (1980-07-01), Firtion et al.
patent: 4697389 (1987-10-01), Romine
patent: 5197089 (1993-03-01), Baker
patent: 5540616 (1996-07-01), Thayer
patent: 6032997 (2000-03-01), Elliot et al.
Chen Mei-Ling
Cheng Patrick
Kao Chung-Hsien
Lee Li-Chung
Huang Jiawei
J. C. Patents
Rose Robert A.
United Microelectronics Corp.
LandOfFree
Grindstone having a vacuum system in a pin chuck stepper does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Grindstone having a vacuum system in a pin chuck stepper, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Grindstone having a vacuum system in a pin chuck stepper will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2487226