Cleaning and liquid contact with solids – Apparatus – With plural means for supplying or applying different fluids...
Reexamination Certificate
1998-08-26
2001-01-09
Markoff, Alexander (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
With plural means for supplying or applying different fluids...
C134S099100, C134S094100, C134S021000, C134S022110, C134S022120, C134S902000
Reexamination Certificate
active
06170496
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus used in servicing a wafer platform and a method for using such apparatus and more particularly, relates to an apparatus for servicing an electrostatic chuck for a wafer in an etch chamber such that a defective conduit to the chamber may be replaced without breaking vacuum in the chamber and vent holes in the electrostatic chuck may be cleared by an inert gas and a method for servicing such electrostatic chuck.
BACKGROUND OF THE INVENTION
Electrostatic chucking (or E-chuck) is a technique used to secure a wafer onto a susceptor in a wafer processing chamber. In recently developed wafer processing technology, the electrostatic wafer holding technique is frequently used in which a chuck electrostatically attracts and holds a wafer. The E-chuck method is a highly desirable technique for use in the vacuum handling and processing of silicon wafers. In contrast to a conventional method by mechanical means such as clamping so that only slow motion of a wafer holder is allowed during wafer transfer, an E-chuck can hold wafers with a force equivalent to several tenths of Torr pressure. Since there are no moving parts acting on the wafer surface, there can be no particle generation or contamination problems in the process chamber.
Another advantage achieved by the electrostatic chuck is the avoidance of non-uniform clamping associated with mechanical clamping device. The E-chuck utilizes an attractive Coulomb force between oppositely charged surfaces to clamp together an article and a chuck. In an electrostatic chucking operation, the force acting between the wafer and the chuck is uniform between a flat wafer and a flat chuck, in contrast to the mechanical clamping system wherein clamping is effected only around the periphery of a wafer. Special provisions must be made in a mechanical clamping system to compensate for the bowing at the center of a wafer caused by the pressure of cooling gas which is pumped in between the wafer and the pedestal that holds the wafer. The bowing phenomena is eliminated in an E-chuck since the wafer is held on a substantially planar chuck surface with an even electrostatic force distributed according to the electrode layout. The electrostatic force is generally sufficient for preventing bowing of the wafer and for promoting uniform heat transfer over the entire wafer surface by flowing an inert gas flow between the wafer and the E-chuck.
A typical vacuum process chamber
10
for etching semiconductor wafers is shown in FIG.
1
. The vacuum process chamber
10
is constructed by a lower chamber
12
, an upper chamber
14
and a cathode assembly
16
which is part of an electrostatic chuck assembly
20
. The process chamber
10
is covered by a dome
18
which forms a hermetically sealed chamber
14
. A vacuum pumping channel
22
is provided for evacuating the chamber interior such that a semiconductor process can be carried out. Internal water cooling channels
26
are also provided for cooling the apparatus during operation of the chamber. Wafer lift bellows
28
which work in conjunction with wafer lift pins
32
lift wafers from the E-chuck
20
after the completion of an etch process. Cathode lift bellows
34
are utilized for the vertical movement of the cathode
16
and the E-chuck
20
. A gas inlet
36
is utilized for feeding an inert gas through the cathode lift bellows
34
to the surface
24
of the E-chuck
20
.
A perspective view of the components that make up the E-chuck assembly
20
is shown in FIG.
2
. In the specific construction, the E-chuck
20
consists of a focus ring
40
, a capture ring
42
, a shell assembly
44
, lift pins
46
which are installed onto a cathode
16
inside an upper chamber
48
, and a bottom chamber
50
. In the operation of the E-chuck
20
, a wafer (not shown) is positioned on top of the surface
24
of the shell assembly
44
. In the top surface
24
, a plurality of ventilation holes
52
are provided which are located at the tips of passageways
54
. The plurality of pin holes, or ventilation holes
52
are provided such that a cooling gas may be fed into the gap
19
. between surface
24
of the shell assembly
44
and the wafer backside.
An enlarged, cross-sectional view of the shell assembly
44
for the E-chuck
20
positioned in a process chamber
10
is shown in FIG.
3
. It should be noted that the E-chuck assembly
20
is shown greatly simplified to merely illustrate the present invention and thus the construction details of the E-chuck
20
are not repeated in
FIG. 3. A
cooling gas
60
of helium is fed into the gas passageway
54
and then flown into a gap between the E-chuck surface
24
and the wafer backside through vent holes
52
. The function of the helium gas
60
is not only to cool the backside of a wafer, but also to achieve a more uniform temperature by transferring heat to the cathode.
In the conventional process chamber
10
shown in
FIG. 3
, the cooling gas of helium is fed into the E-chuck
20
through a control valve
56
, a first conduit
58
and a second conduit
60
which are connected by a coupling
62
. The first conduit
58
is normally constructed of a flexible metal pipe such as a pipe made of braided metal tape. The second conduit
60
, for ease of installation, is normally supplied in a flexible, metal mesh reinforced elastomeric hoses. After repeated usage, the flexible metal pipe
58
may develop a leak such that the ventilation function of the helium gas cannot be satisfactorily performed since the pipe moves up-and-down with the cathode all the time. In order to replace a defective conduit
58
, the upper chamber
14
must be vented to the atmosphere during the procedure. This becomes a time consuming and labor consuming to process and furthermore, the venting of the upper chamber
14
to the atmosphere further increases the possibility of chamber contamination.
Another frequently observed problem in the operation of an E-chuck is the blockage, or partial blockage of the vent holes
52
. When the blockage is severe, the effectiveness of a helium cooling gas for achieving temperature uniformity on the wafer is greatly reduced. The plugging of the vent holes
52
may occur after a wet cleaning process is conducted on the E-chuck
20
. Any cleaning residue may be lodged in the tiny vent holes
52
to form a partial or complete blockage of the holes. A wafer processed on the E-chuck
20
may thus be burned or heated non-uniformly due to the insufficient cooling by the helium cooling gas. This may result in the scrap of the wafer.
It is therefore an object of the present invention to provide an apparatus for servicing a wafer chuck that does not have the drawbacks or shortcomings of the conventional apparatus.
It is another object of the present invention to provide an apparatus for servicing an electrostatic chuck in a semiconductor process chamber that does not require the breaking of vacuum in the chamber.
It is a further object of the present invention to provide an apparatus for servicing an electrostatic chuck in a semiconductor process chamber that is capable of isolating the process chamber when a cooling gas supply line to the chamber is disconnected.
It is another further object of the present invention to provide an apparatus for servicing an electrostatic chuck in a semiconductor process chamber that includes a three-way valve and a high pressure inert gas supply.
It is still another object of the present invention to provide an apparatus for servicing an electrostatic chuck in a semiconductor process chamber which allows the cleaning of vent holes in the surface of the electrostatic chuck by a high pressure inert gas.
It is yet another object of the present invention to provide an apparatus for servicing an electrostatic chuck in a semiconductor process chamber that can be used to replace a gas supply conduit to the chamber when a leakage in the conduit is detected to be larger than 2 m Torr per minute.
It is still another further object of the present invention to provide a metho
Chen Jia Rong
Peng Long Hoang
Markoff Alexander
Taiwan Semiconductor Manufacturing Co. Ltd.
Tung & Associates
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