Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – Having glow discharge electrode gas energizing means
Reexamination Certificate
2001-09-14
2004-09-21
Goudreau, George A. (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
Having glow discharge electrode gas energizing means
C156S345450, C156S345510, C156S345440, C118S728000, C118S7230ER
Reexamination Certificate
active
06793767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for manufacturing a semiconductor device and a method for using the apparatus. More particularly, the present invention relates to a wafer stage including an electrostatic chuck, and to a method for dechucking a wafer using the wafer stage.
2. Description of the Related Art
Semiconductor devices are manufactured after performing many processes such as depositing a material layer on a wafer, patterning the deposited material layer, and removing unnecessary residuals on the wafer. To perform these processes repeatedly, a wafer is loaded on a wafer stage inside a chamber, the wafer is processed, and then unloaded.
In order to successively process a wafer, it is very important to chuck and fix the wafer in the chamber and to dechuck the wafer so that the wafer will not be damaged after processing. As semiconductor devices become highly integrated, the design rule becomes smaller, and the process margin becomes narrower. As a result, there is a greater need to chuck and fix the wafer without damaging the wafer during dechucking.
Methods for fixing the wafer to the wafer stage in the process chamber when the wafer is loaded on the wafer stage include using hardware structures such as clamps, using a vacuum to suction the rear side of the wafer (a vacuum chuck), using gravity, and using a piezoelectric effect. Various methods are available for dechucking the fixed wafer on the wafer stage after processing the wafer. The dechucking method used is chosen in accordance with the method used for fixing the wafer.
The most widely used method for fixing a wafer is the piezoelectric effect. In this method, an electrostatic chuck is used to fix the wafer, and the electrostatic chuck and a lifting means are used to dechuck the fixed wafer.
FIG. 1A
illustrates a sectional view of a method for chucking a wafer using an electrostatic chuck according to the prior art. Referring to
FIG. 1A
, first, the structure of an electrostatic chuck
10
will be described, and then, a method for chucking a wafer
20
will be described. The electrostatic chuck
10
includes an upper insulating layer
2
, an electrostatic electrode
4
, a lower insulating layer
6
, and a lower electrode
8
. The lower electrode
8
controls the reaction speed of plasma when plasma is generated in the chamber (not shown). The electrostatic electrode
4
is connected to a DC generator (not shown), and positive charges or negative charges are distributed on the electrostatic electrode
4
by the DC generator. The electric charges on the electrostatic electrode
4
induce an electrostatic field such that the wafer
20
is chucked or dechucked. The electrostatic electrode
4
and the lower electrode
8
are insulated by the lower insulating layer
6
, and the wafer
20
and the electrostatic electrode
4
are insulated by the upper insulating layer
2
.
In a method for dechucking the wafer
20
according to the prior art, the wafer
20
is put on the electrostatic chuck
10
, and an electrostatic field is induced by supplying power to the electrostatic electrode
4
under the upper insulating layer
2
on the upper surface of the electrostatic chuck
10
. Positive charges accumulate on the electrostatic electrode
4
connected to the external DC generator (not shown), and negative charges accumulate on the lower surface of the wafer
20
by plasma generated on an upper portion of the wafer
20
, thereby inducing an electrostatic field between the wafer
20
and the electrostatic electrode
4
. When the upper surface of the electrostatic chuck
10
is completely in contact with the wafer
20
, a clamping force is produced by the electrostatic field, and thus, the wafer
20
is chucked.
Meanwhile, some of the charges on the electrostatic electrode
4
of the electrostatic chuck
10
flow into the upper surface of the electrostatic chuck
10
through the upper insulating layer
2
, and as time goes by, the electric charges accumulate. The clamping force between the wafer
20
and the electrostatic chuck
10
increases due to the accumulated electric charges. As a result, the magnitude of the clamping force grows larger than the voltage applied to the electrostatic electrode
4
of the electrostatic chuck
10
. The wafer
20
and the electrostatic chuck
10
are stuck together by the increased clamping force when the wafer
20
and the electrostatic chuck
10
are dechucked.
FIG. 1B
illustrates a sectional view of a method for dechucking a wafer
20
using an electrostatic chuck according to the prior art. When the wafer
20
is chucked, plasma formation on the upper portion of the wafer
20
stops, and the voltage supplied to the lower electrode
8
and the electrostatic electrode
4
of the electrostatic chuck
10
is turned off. As a result, the electric charges flow out and the clamping force is reduced. However, since a discharge time is necessary for the charges to flow when the clamping force is reduced, the wafer
20
becomes stuck to the electrostatic chuck
10
.
When lift pins
12
are raised to dechuck a wafer
20
that is stuck to the electrostatic chuck
10
, the force applied to the wafer
20
can easily damage the wafer
20
. In order to prevent the sticking phenomenon, power is again supplied to the electrostatic electrode
4
, in which positive charges remain, and negative charges flow into the electrostatic electrode
4
. That is, electric charges having a charge opposite to those supplied to the electrostatic electrode
4
during chucking flow into the electrostatic electrode
4
during dechucking in order to neutralize the electrostatic electrode
4
, thereby easily dechuck the wafer
20
.
Subsequently, the lift pins
12
of the lifting means (not shown) are raised, and the wafer
20
is dechucked. However, in the method for supplying electric charges having an opposite polarity to the electrostatic electrode
4
, the wafer
20
still possesses electric charges, and thus, the method is not of much help for dechucking.
SUMMARY OF THE INVENTION
In order to solve the aforementioned problems, it is a feature of an embodiment of the present invention to provide a wafer stage which is capable of easy dechucking and includes an electrostatic chuck which does not damage a wafer.
Another feature of an embodiment of the present invention is to provide a method for dechucking a wafer using the wafer stage.
In an effort to satisfy these and other features of the present invention, there is provided a wafer stage installed in a process chamber including: an electrostatic chuck support installed in a lower half of an enclosed chamber for supporting an electrostatic chuck; an electrostatic chuck installed on the electrostatic chuck support for chucking and supporting a wafer; a lifting means installed inside the electrostatic chuck and the electrostatic chuck support for lifting the wafer; and a grounding means including interconnections for connecting the lifting means to ground and a device for connecting the interconnections, which is installed between the interconnections, for allowing electric current flow and preventing electric current flow.
Preferably, the wafer stage further includes a guide ring installed around the electrostatic chuck for guiding the wafer when the wafer is chucked.
Preferably, the process chamber is a device for processing the wafer using plasma or a device for etching plasma.
Preferably, the lifting means includes: a plurality of lift pins for passing the electrostatic chuck and lifting the wafer; a lift pin support for supporting the lift pins in the electrostatic chuck support a connecting axis for connecting the lift pin support to a driving means; and a driving means for lifting the connecting axis. Also, it is preferable that the lift pins are formed of a conductive material and that the conductive material is aluminum.
Preferably, the electrostatic chuck includes: a lower electrode, which is connected to a DC generator located outside the enclosed chamber, for controlling the reaction speed of
Chi Kyeong-koo
Chu Chang-woong
Chung Seung-pil
Kim Ji-soo
Seo Sang-hun
Goudreau George A.
Lee & Sterba, P.C.
Samsung Electronics Co,. Ltd.
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