Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With workpiece support
Reexamination Certificate
2000-09-28
2003-09-23
Beck, Shrive P. (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With workpiece support
C156S915000, C118S728000
Reexamination Certificate
active
06623597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for manufacturing a semiconductor device. More particularly, the present invention relates to a focus ring for focusing plasma or a reaction gas onto a semiconductor wafer.
This application is a counterpart of, and claims priority to, Korean Patent Application No. 1999-41795, filed Sep. 29, 1999, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, semiconductor device manufacturing processes such as etching or chemical vapor deposition (CVD) are carried out using a plasma reactor. If the plasma is not distributed uniformly over the wafer, the semiconductor wafer will not be etched uniformly or the layer deposited thereon will not have a uniform thickness. A non-uniform plasma distribution can be caused by non-uniform gas flow across the semiconductor wafer, a non-uniform cathode temperature and/or variations in the intensity in an electric field induced within the reactor, etc. A vacuum pump disposed at the bottom of the plasma reactor continuously exhausts gas to the exterior thereof so that the level of the vacuum in the processing chamber of the reactor is maintained constant. The semiconductor wafer is held by a pedestal or chuck that is located at a center of the processing chamber. Plasma, which is introduced downwardly into the chamber, has a higher flow rate around the semiconductor wafer. Such a plasma reactor is disclosed in, for example, U.S. Pat. No. 5,685,914, entitled A Focus Ring For Semiconductor Wafer Processing In A Plasma Reactor, issued to Graham W. Hills et al. on Nov. 11, 1997.
The focus ring which is the subject of this patent is provided to facilitate a uniform etching of the wafer.
FIGS. 1 and 2
show such a conventional plasma reactor. Referring now to these figures, a vacuum chamber
102
has a gate valve
106
at a sidewall
104
thereof for enabling a semiconductor wafer
110
to enter/exit the chamber
102
. The wafer
110
is held by a wafer chuck
112
. The periphery of the wafer
110
rests on the wafer chuck
112
, and is shielded by a focus ring
114
that surrounds the periphery.
During an etching process, an inner peripheral sidewall
114
a
of the focus ring
114
locks in charged processing gases on the wafer
110
. This enhances the etching process and ensures that the rate at which the wafer
110
is etched is constant. However, the inner peripheral sidewall
114
a
chemically reacts with the processing gases to create by-products
118
. These by-products
118
constitute particulate contaminants
118
in the chamber
102
. As successive ones of the etching processes are carried out, the by-products
118
attached to the inner peripheral sidewall
114
a
grow or increase in number. The by-products
118
eventually fall upon the wafer
110
and thereby contaminate the wafer
110
. Thus, these contaminants
118
lower the yield during the mass production of semiconductor devices.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a focus ring of an apparatus for processing a semiconductor wafer, which can prevent particulate contaminants adhering to an inner surface of the focus ring from later falling onto the wafer.
To achieve this object, the present invention provides a focus ring having a stepped inner periphery which is formed by a cylindrical bottom surface having a first diameter, a cylindrical top surface having a second diameter greater than the first diameter, and a collector located between the top surface and the bottom surface for collecting contaminants created at the top surface.
The apparatus for processing a semiconductor wafer includes a process chamber, a circular chuck and the focus ring. The chuck is located in the process chamber and holds the wafer. The focus ring focuses processing media onto a surface of the wafer that is held by the chuck. The cylindrical bottom surface of the focus ring extends around that portion of the chuck which supports the wafer.
The collector may form an upwardly facing concavity.
The collector is located beneath the inner upper surface so as to collect particulate contaminants falling therefrom. Thus, the particulate contaminants do not fall onto the semiconductor wafer, whereby the yield of products produced from the wafer is increased. Further, an RF (radio frequency) on time of the apparatus can be extended as much as two times or more the average RF on time of a conventional apparatus, whereby the productivity of the apparatus is enhanced.
REFERENCES:
patent: 5474649 (1995-12-01), Kava et al.
patent: 5789324 (1998-08-01), Canale et al.
patent: 6344105 (2002-02-01), Daugherty et al.
Choi Byeung-Wook
Han Oh-Yeon
Kim Guk-Kwang
Yang Yun-Sik
Beck Shrive P.
Kackar Ram N
Volentine & Francos, PLLC
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