Radiant energy – Ion generation – Electron bombardment type
Patent
1987-01-09
1988-04-19
Anderson, Bruce C.
Radiant energy
Ion generation
Electron bombardment type
250423R, 250251, 31511181, H01J 2700
Patent
active
047391707
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a technique which is used to expand and intensify a plasma from a source region into a working chamber.
In the last two decades, but particularly in recent years, significant developments have taken place in the area of plasma generation. These have been prompted by a usefulness of plasmas in all aspects of semiconductor technology and by an ever increasing number of new applications. Some of the areas where a plasma, or its separated charged particles are used are ion sources, ion rockets, nuclear physics, heavy-ion science, ion plating, crystal growth (ion beam epitaxy), synthesis of compound materials (plasma polymerization, reactive sputtering), ion sputtering activated reactive evaporation, surface analysis, medical applications, surface treatment, ion-assisted thin film deposition, lasers and many others.
As an example of the art reference may be had to the Proceedings of the International Engineering Congress--ISIAT'83 and 1PAT'83 Kyoto (1983) in which a plasma system is described which is used for plasma oxidation of silicon surfaces as used in VLSI production, but the present invention has many applications.
Also reference may be had to the specification of U.S. Pat. No. 3,660,715 of Richard F. Post assigned to the United States Energy Commission which relates to a plasma generator using a stack of pulsed washers to release, ionize and heat the gas.
An object of the present invention is to provide a plasma generating device of simple construction and ease of operation and which allows an enhanced collision probability between charged and neutral particles in the working chamber together with enhanced energy transfer and uniformity of the plasma.
The invention consists of a plasma generator which allows both electrons and ions to oscillate in an applied field at low frequency excitation with electrons and ions moving in opposite directions.
According to this invention a plain cylindrical magnetron communicates with a chamber and both are pumped through by a high vacuum pumping system, the magnetron having means to produce electrons and including magnetic means to cause the electrons to rotate and spiral and ionise gas atoms or molecules introduced to the magnetron to produce plasma, characterised by means to establish an axial oscillation of electrons and ions in opposite direction, the means comprising magnetic mirror means at the outlet of the magnetron adjacent to the chamber and further magnetic mirror means at the opposite side of the chamber whereby to increase significantly ion electron interaction to facilitate multiple ionization and additionally to enhancement of neutral particle ionization, the chamber having in it an electrode adjacent to the plasma field which is polarised to produce either an electrically neutral or positive or negative stream of charged particles.
To enable the invention to be fully understood, it will now be described with reference to the accompanying drawings which show various forms of the invention and in which:
FIG. 1 is a schematic diagramatic view of one form of the invention using three magnets with one magnet related particularly with the magnetron and two magnets positioned one each side of the chamber to form the magnetic mirror means across the chamber, the drawing including block diagrams to show the method of establishing the axial of electrons and ions in opposite direction,
FIG. 2 is a somewhat schematic transverse section of the invention,
FIG. 3 is a view corresponding to FIG. 1 but showing a two magnet system, and
FIG. 4 shows in a view similar to FIG. 1 in which a single magnet is used.
Referring first to FIGS. 1 and 2, the two main components of the source are a plain cylindrical magnetron 1 and a vacuum chamber 2. The vacuum chamber 2 and the magnetron 1 are pumped through the opening 3 by a conventional high vacuum pumping system.
The materials to be ionized are introduced into the system through inlet 4 in a gas or vapour form.
The initial ionization takes place in the plain cylindrical magnetron 1, which has an elec
REFERENCES:
patent: 2837693 (1958-06-01), Norton
patent: 3155593 (1964-11-01), Warnecke et al.
patent: 3660715 (1972-05-01), Post
patent: 3999072 (1976-12-01), Takagi
patent: 4213043 (1980-07-01), Dawson
patent: 4468564 (1984-08-01), Boyer et al.
patent: 4645977 (1987-02-01), Kurokawa et al.
patent: 4661710 (1987-04-01), Verney et al.
patent: 4682026 (1987-07-01), Douglas
Anderson Bruce C.
The Commonwealth of Australia
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