Use of perfluoroketones as vapor reactor cleaning, etching,...

Details Use of perfluoroketones as vapor reactor cleaning, etching,... Use of perfluoroketones as vapor reactor cleaning, etching,...

2001-04-24

2003-04-01

Olsen, Allan (Department: 1763)

Etching a substrate: processes

Gas phase etching of substrate

Application of energy to the gaseous etchant or to the...

C216S079000, C134S001100, C134S022100

Reexamination Certificate

active

06540930

ABSTRACT:

FIELD OF INVENTION
The invention relates to methods of using perfluoroketone as a reactive gas for removing unwanted deposits that build up in a vapor reactor, for etching dielectric or metallic materials in a vapor reactor, and for doping various materials in a vapor reactor.
BACKGROUND OF THE INVENTION
The emission of global warming gases has received worldwide attention. The goal of the Kyoto Protocol, established at the United Nations Conference on Global Warming, was to lower emissions of carbon dioxide, methane, nitrous oxide, perfluorocarbon (PFC), hydrofluorocarbon (HFC), and SF
6
to pre-1990 levels. Additionally, most manufacturers of semiconductors in the United States have signed a Memorandum of Understanding with the Environmental Protection Agency pledging to evaluate options for reducing PFC emissions. Perfluorocarbons and perfluorinated nitrogen compounds typically used in the semiconductor industry include CF
4
, C
2
F
6
, NF
3
, and C
3
F
8
. These materials are extremely stable compounds and are difficult to trap or treat with gas scrubbers.
Chemical vapor deposition chambers, physical vapor deposition chambers, and etching chambers are widely used in the semiconductor industry in connection with the manufacture of various electronic devices and components. Such chambers use reactive gases or vapors to deposit, pattern, or remove various dielectric and metallic materials. Perfluorocarbons and perfluorinated nitrogen compounds are widely used in conjunction with vapor reactors for etching or patterning materials and for removing unwanted deposits that build-up on the reactor walls and parts. The semiconductor industry needs alternative chemicals for vapor reaction techniques that do not contribute to global warming. This invention provides methods of using a perfluoroketone in a vapor reactor as a reactive gas to remove unwanted deposits, to etch dielectric and metallic materials, and to dope materials. The perfluoroketones perform as well as or better than perfluorocarbons while offering the advantage of significantly lower global warming potential. Additionally, the perfluoroketones are less toxic than NF
3
, another gas widely used in the semiconductor industry for cleaning purposes.
SUMMARY OF THE INVENTION
The invention provides a method for cleaning a chemical vapor deposition chamber, a physical vapor deposition chamber, or an etching chamber using a reactive gas comprising a perfluoroketone with 4 to 7 carbon atoms. The perfluoroketone is generally mixed with oxygen gas and a radio frequency plasma is generated. Both the cleaning time and global warming emissions are dependent on the power used to generate the plasma, the pressure inside the chamber, the gas flow rate, and the ratio of perfluoroketone to oxygen. The use of the perfluoroketone cleaning gas can result in shorter cleaning times and lower PFC emissions compared to the standard cleaning gases used by the semiconductor industry such as CF
4
, C
2
F
6
, c-C
4
F
8
O, and C
3
F
8
.
The invention also provides a method for etching a dielectric or metallic material using a reactive gas comprising a perfluoroketone with 4 to 7 carbon atoms. The rate of etching is comparable to that of materials commonly used for etching in the semiconductor industry such as CF
4
, C
2
F
6
, c-C
4
F
8
O and C
3
F
8
.
Another aspect of the invention provides a method for using a reactive gas comprising a perfluoroketone with 4 to 7 carbon atoms as a source of fluorine for preparation of fluorine containing or fluorine doped materials.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION
The invention provides methods of using a perfluoroketone as a reactive cleaning gas, etchant, and dopant in a vapor reactor. As used herein, the term “vapor reactor” includes chemical vapor deposition chambers, physical vapor deposition chambers, and etching chambers. Such reactors use reactive gases or vapors to deposit, pattern, or remove various dielectric and metallic materials. In particular, the invention provides a method for using a reactive gas comprising a perfluoroketone with 4 to 7 carbon atoms for in situ cleaning of a vapor reactor. The invention also provides a method for using a reactive gas comprising a perfluoroketone with 4 to 7 carbon atoms as an etchant to pattern or remove dielectric and metallic materials. Additionally, the invention provides a method for using a reactive gas comprising a perfluoroketone with 4 to 7 carbon atoms as a source of fluorine to prepare fluorine containing or fluorine doped materials.
The perfluoroketones of this invention have a boiling point less than about 80° C. The compounds can be linear, branched, or cyclic and contain 4 to 7 carbon atoms. Preferably, the perfluoroketones contain 5 to 7 carbon atoms. Representative examples of perfluoroketone compounds include CF
3
C(O)CF
2
CF
3
, CF
3
CF
2
C(O)CF
2
CF
3
, CF
3
C(O)CF(CF
3
)
2
, CF
3
CF
2
C(O)CF(CF
3
)
2
, CF
3
(CF
2
)
2
C(O)CF(CF
3
)
2
, (CF
3
)
2
CFC(O)CF(CF
3
)
2
, CF
3
(CF
2
)
2
C(O)CF
2
CF
2
CF
3
, perfluorocyclopentanone, an perfluorocyclohexanone.
Perfluoroketones can be prepared by known methods. One approach involves the dissociation of perfluorinated carboxylic acid esters of the formula R
f
CO
2
CF(R
f′
)
2
with a nucleophilic initiating agent as described in U.S. Pat. No. 5,466,877 (Moore). R
f
and R
f′
are fluorine or a perfluoroalkyl group. The fluorinated carboxylic acid ester precursor can be derived from the corresponding fluorine-free or partially fluorinated hydrocarbon ester by direct fluorination with fluorine gas as described in U.S. Pat. No. 5,399,718 (Costello et al.).
Perfluorinated ketones that are alpha-branched to the carbonyl group can be prepared as described in U.S. Pat. No. 3,185,734 (Fawcett et al.). Hexafluoropropylene is added to acyl halides in an anhydrous environment in the presence of fluoride ion. Small amounts of hexafluoropropylene dimer and/or trimer impurities can be removed by distillation from the perfluoroketone. If the boiling points are too close for fractional distillation, the dimer and/or trimer impurity can be removed by oxidation with alkali metal permanganate in a suitable organic solvent such as acetone, acetic acid, or a mixture thereof. The oxidation reaction is typically carried out in a sealed reactor at ambient or elevated temperatures.
Linear perfluorinated ketones can be prepared by reacting a perfluorocarboxylic acid alkali metal salt with a perfluorocarbonyl acid fluoride as described in U.S. Pat. No. 4,136,121 (Martini et al.) Such ketones can also be prepared by reacting a perfluorocarboxylic acid salt with a perfluorinated acid anhydride in an aprotic solvent at elevated temperatures as described in U.S. Pat. No. 5,998,671 (Van Der Puy).
All the above-mentioned patents describing the preparation of perfluoroketones are incorporated by reference in their entirety.
In the manufacture of various electronic devices or components, vapor reactors are used for depositing as well as etching dielectric and metallic materials. With both deposition and etching processes, unwanted deposits can build-up on the reactor walls and parts over time. These deposits are a source of potential contamination of the electronic device and components being produced in the vapor reactor. Thus, these unwanted deposits must be removed periodically. The deposits can include fluoropolymers containing carbon, hydrogen, oxygen, and fluorine if perfluorochemicals or hydrofluorochemicals have been used in the vapor reactor. The deposits can also contain silicon-based materials as well as various metallic materials such as, for example, tungsten and aluminum. As used herein, the term “cleaning” refers to removing the unwanted deposits that build up over time on the walls and parts of a vapor reactor.
The invention provides a method for cleaning vapor reactors using a reactive gas comprising a perfluoroketone having a boiling point less than 80° C. and containing 4 to 7 carbon atoms. Preferably, the perfluoroketone contains 5 to 7 carbon atoms. Typically, the perfluo

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