Electric lamp and discharge devices – Fluent material supply or flow directing means – Plasma
Reexamination Certificate
1999-04-27
2002-04-09
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Fluent material supply or flow directing means
Plasma
C315S111210, C315S111010, C313S231010, C313S231410, C118S7230MW, C118S7230ME
Reexamination Certificate
active
06369493
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to semiconductor wafer processing equipment. More specifically, the invention relates to apparatus for cooling a microwave plasma applicator in a remote plasma source for a semiconductor wafer processing system.
2. Description of the Background Art
Many industrial applications utilize reactive gases and gas mixtures to process a workpiece. Such applications include the processing of semiconductor wafers during integrated circuit fabrication. A simplified depiction of a semiconductor wafer processing system
100
of the prior art is depicted in FIG.
1
. The system
100
comprises a gas source
114
, a remote plasma source
101
, and a process chamber
102
. The source
101
comprises a plasma applicator
116
, a waveguide
110
and a microwave source (magnetron)
108
. In the system
100
, reactive gas species are produced, for example, in the plasma applicator
116
and are coupled to the processing chamber
102
wherein the semiconductor wafer W is positioned such that the wafer is exposed to the reactive gas species. Such an applicator
101
generates and sustains a plasma
105
of reactive species such as free radicals and ions. Often it is desirable to process a workpiece W with the free radicals but not the ions. In such a situation, the applicator
101
is coupled to the processing chamber by a channel or tube
104
. The processing chamber
102
is generally maintained at a lower pressure than the applicator
101
. Consequently, ions and free radicals tend to drift through the channel
104
towards the chamber
102
. If the residence time in the channel
104
is sufficiently long, the ions will recombine before reaching the chamber
102
. The free radicals, however, will enter the chamber and process the wafer W.
The plasma applicator
101
comprises a microwave transmissive tube
106
and a coaxially aligned, cylindrical cooling jacket
112
. The tube
106
is connected to the microwave source, such-as a magnetron
108
, by the waveguide
110
. Microwaves, delivered by the waveguide
110
to the applicator
116
excite a process gas within the tube
106
to produce and sustain a plasma
105
therein. The process gas absorbs some microwave energy which heats the gas. Additional heat is generated by recombination of ionized species in the plasma
105
. A substantial amount of heat is produced in the tube
106
. As such, the tube
106
is surrounded by the cooling jacket
112
to remove heat generated by absorption of microwaves and plasma recombination. Such cooling is accomplished by flowing a coolant through the cooling jacket
112
that surrounds the tube
106
. Specifically, the coolant flows through conduits or channels
118
formed in the cooling jacket
112
.
To couple energy to the process gas, the microwaves pass through the cooling jacket, the cooling fluid and the tube. Although the cooling jacket
112
and tube
106
are fabricated from microwave transmissive material such as quartz, these elements and the coolant attenuate the microwave energy. As such, to achieve a particular plasma energy level, the magnetron must produce enough energy to overcome this attenuation.
Therefore, a need exists in the art for an a plasma applicator that is cooled in a manner that optimizes thermal transfer from the applicator while maximizing microwave energy transmission to the plasma.
SUMMARY OF THE INVENTION
The disadvantages heretofore associated with the prior art are overcome by a plasma applicator having a cooling jacket with a low absorption of electromagnetic energy. The applicator comprises a tube that is surrounded by a cooling jacket where the cooling jacket is spaced apart from the tube to define a volume between the jacket and the tube. This volume is filled with a thermal transfer medium. The thermal transfer medium transfers heat from the tube to the cooling jacket while transmitting electromagnetic radiation to the plasma.
The plasma applicator can be employed in a microwave plasma processing system to process a workpiece. The system generally comprises a processing chamber, a microwave plasma applicator and a process gas source. The process gas source is coupled to the applicator and the applicator is coupled to the processing chamber. The applicator has a microwave-transparent tube, and a cooling jacket with at least one water channel. The cooling jacket surrounds the tube such that a volume is defined between said water jacket and the tube. A thermal transfer medium fills the volume to promote heat transfer from the tube to the cooling jacket.
This invention fulfills the need for an apparatus that can effectively cool the microwave transparent tube of an applicator while transferring microwave power to the plasma with minimal absorption by the cooling jacket.
REFERENCES:
patent: 4849146 (1989-07-01), Tanji et al.
patent: 5126635 (1992-06-01), Doehler et al.
patent: 5262610 (1993-11-01), Huang et al.
patent: 5439175 (1995-08-01), Okamura et al.
patent: 5747917 (1998-05-01), Herchen
patent: 5902404 (1999-05-01), Fong et al.
Herchen Harald
Lubomirsky Dmitry
Olgado Donald J.
Palagashvili David
Yavelberg Simon
Applied Materials Inc.
Moser Patterson and Sheridan
Patel Nimeshkumar D.
Santiago Mariceli
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