Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-04-01
2001-04-24
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S7230ER, C118S7230AN
Reexamination Certificate
active
06221202
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a structure utilized to contain a plasma and/or electromagnetic field within a desired space while maintaining high conductance across the structure.
2. Description of Related Art
Plasma processing is often used under circumstances where it is beneficial to restrict the presence of the plasma to a certain region in the chamber while maintaining the ability to flow gasses through the plasma containing region. Several methods of plasma containment are currently in practice, including magnetic confinement, inertial confinement and confinement by solid or nearly solid barriers. Inertial confinement works only for short periods of time and has been shown useful only in power generating and explosive devices. Magnetic confinement has strong limitations in its application to many industrial applications. Because of the shortcomings of inertial and magnetic confinement systems, industrial plasma confinement is most often achieved by using a physical barrier within the chamber to confine the plasma.
For systems confining the plasma by physical barriers, this has been accomplished by placing openings in the physical barrier for the gases to flow through. Plasma confinement has been maintained by making at least one dimension of the cross section of these openings similar in size or smaller than the plasma sheath or dark space as disclosed in U.S. Pat. Nos. 4,384,938 and 5,605,637. However, utilizing such small holes in the physical barrier has been found to lead to low conductance, particularly when the molecular mean free path is similar to or longer than the dark space. Further, these small holes tend to clog in the presence of a depositing chemistry such as is typically used in selective etching. This clogging not only restricts the useful time between cleaning of the chamber but creates continually changing process conditions which can reduce process yields.
In the case of highly selective etch chambers utilized in the semiconductor manufacturing industry, it is common to have plasma conditions where the molecular mean free path is long compared to the dark space of the RIE chamber and where there is the problem of film deposited on the physical barrier. Accordingly, there is a long-felt need for plasma barriers in RIE systems that have a high, relatively stable conductance and excellent plasma confinement properties even when the molecular mean free path is long compared to the dark space and/or when a film is being deposited on the barrier.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a barrier useful in systems that has a high, relatively stable conductance.
It is another object of the present invention to provide a barrier useful in systems that has excellent plasma confinement properties even when the molecular mean free path is long compared to the dark space.
A further object of the invention is to provide a barrier useful in systems that has excellent plasma confinement properties even when a film is being deposited on the barrier.
It is yet another object of the present invention to provide a system that incorporates a barrier having the aforementioned advantages.
SUMMARY OF THE INVENTION
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a containment structure for a plasma which includes means for containing a plasma, that is sustained by an electromagnetic field, within a desired space by attenuating the electromagnetic field outside of the space to levels which do not sustain the plasma while maintaining high conductance across the containment structure; and which further includes means for permitting gas flow through the containment structure even though contaminants build up on the containment structure. Details of operations of a similar device may be found in a co-pending patent application Ser. No. 08/957,412 filed on Oct. 24, 1997 now U.S Pat. No. 6,051,100 which is assigned to the same assignee as this case and is hereby included herein by reference.
In a related aspect, the present invention provides a plasma reactor containing a reactor chamber adapted to create and sustain a plasma in a space therein, along with a containment structure. The containment structure includes means for containing a plasma within a desired portion of space in the chamber by attenuating an electromagnetic field generated in the chamber while maintaining high conductance across the containment structure; and means for permitting gas flow within the chamber and through the containment structure while allowing significant deposit to accumulate before the structure's conductance is appreciably changed.
The plasma has a plasma sheath and two dimensions of the openings along a surface of the containment structure are greater than the plasma sheath. The structure is electrically conductive and comprises a lower and upper portion. The portions may be separated into two separate and distinct units or combined into a single unit. The upper portion closest to the electromagnetic energy has widely spaced openings which attenuates the energy of surrounding plasma. The wider spaced openings permit deposits to accumulate without severely affecting the conductance of the gas which passes through both the upper and lower portions. The lower portion which is farther away from the electromagnetic energy has narrowly spaced openings in which the plasma density is lowered sufficiently to where it is no longer sustained.
In another aspect, the present invention provides a plasma reactor comprising a reactor chamber adapted to create and sustain an active plasma in a space therein and a plasma containment structure while avoiding build up of contaminants which would block the flow of gases through the smaller openings of the lower portion of the containment structure. The plasma containment structure includes means for containing an active plasma within a desired portion of space in the chamber on one side of the structure by attenuating an electromagnetic field in the chamber while maintaining high conductance across the containment structure. The containment structure may permit formation of a cold plasma on the other side of the structure. The containment structure also includes means for permitting gas flow within the chamber and through the containment structure.
All three dimensions of the openings may be greater than the molecular mean free path of the plasma, and may be greater than the plasma sheath. As previously indicated, the structure may comprise spaced, wide and narrow openings having conductive surfaces and the conductive surfaces may form the openings for the gas flow.
In yet another aspect, the present invention relates to a plasma reactor comprising a reactor chamber adapted to create and sustain a plasma in a space containing an electromagnetic field and a containment structure in the chamber. The containment structure is made of an electrically conductive material and is configured to contain a plasma within a desired space in the chamber by attenuating an electromagnetic field in the chamber while maintaining high conductance across the structure. The structure contains openings for permitting gas flow within the chamber, the openings having the two dimensions parallel to a surface of the containment structure greater than the plasma sheath. The structure may comprise a plurality of containment plates adapted to progressively attenuate the plasma and electric field while reducing the build up of contaminants which would block the flow of gases and change the conductance of the structure. The structure may comprise spaced, wide and narrow slits, holes or openings in the conductive surfaces, and the spaces between the surfaces may comprise the openings for the gas flow.
It is also preferred that the structure contain conductive surfaces oriented to prevent line of sight transmission of a vector
Dang Thi
International Business Machines - Corporation
Walsh Robert A.
LandOfFree
Efficient plasma containment structure does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Efficient plasma containment structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Efficient plasma containment structure will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2471729