Deposition of coatings using an atmospheric pressure plasma jet

Details Deposition of coatings using an atmospheric pressure plasma jet Deposition of coatings using an atmospheric pressure plasma jet

1998-10-20

2001-02-27

Meeks, Timothy (Department: 1762)

Coating processes

Direct application of electrical, magnetic, wave, or...

Pretreatment of coating supply or source outside of primary...

C427S579000, C427S580000

Reexamination Certificate

active

06194036

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to plasma-enhanced, chemical vapor deposition of coatings and, more particularly, to the use of an atmospheric-pressure, plasma discharge jet for deposition of films on substrates. This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy to The Regents of the University of California (CULAR UC-Los Alamos National Laboratory Grant). The government has certain rights in the invention.
BACKGROUND OF THE INVENTION
Silicon dioxide is one of the primary materials used in integrated circuit production. Silicon dioxide films are used for interlayer dielectrics and gate oxides for transistors and are presently either grown by thermal oxidation of silicon or deposited by thermal- or plasma-enhanced, chemical vapor deposition. Plasma-enhanced, chemical vapor deposition (PECVD) is often preferred since deposition temperatures are considerably lower than other methods.
The use of silane to deposit silicon dioxide films has been studied in detail. However, PECVD of silicon dioxide using tetraethoxysilane (TEOS) has been found to have several advantages over silane-based CVD processes. Although higher deposition rates are achieved with silane, better conformal coverage of a device is obtained with TEOS due to its lower reactive sticking probability on surfaces (0.045 compared to 0.35 for silane). In addition, TEOS is less hazardous and easier to handle when compared with silane. With the increasing importance of smaller features, step coverage has become an important issue as well. Thus, TEOS has become the primary material for multilevel interconnects in very large-scale, integrated circuit (VLSI) applications. Thermal CVD of silicon dioxide is often carried out with TEOS and ozone. In this process, the deposition is believed to result from the reaction of TEOS and O or O
3
in the gas phase. The atomic oxygen is maintained by the decomposition of O
3
. Plasma-enhanced, chemical vapor deposition of SiO
2
is currently performed using TEOS and a reactive oxygen source which contains O atoms or O
2
+
ions.
Conventional, low-pressure plasma discharges produce ions and atomic species which may damage underlying layers during the film deposition process. Since atmospheric operation offers certain advantages over vacuum processes, it was decided to explore whether the plasma jet could be used for PECVD of SiO
2
.
Accordingly, it is an object of the present invention to generate an intense flux of metastable and/or atomic species for use in plasma-enhanced, chemical vapor deposition onto a substrate without exposing the substrate to a significant flux of ionic species.
Another object of the invention is to generate an intense flux of metastable and/or atomic species for use in plasma-enhanced, chemical vapor deposition onto a substrate at atmospheric pressure.
Yet another object of the present invention is to generate an intense flux of metastable and/or atomic species for use in plasma-enhanced, chemical vapor deposition onto a substrate at atmospheric pressure without significantly heating the substrate with the plasma.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects and, in accordance with the purposes of the present invention as embodied and broadly described herein, the method for depositing a material on a substrate hereof may include the steps of: generating reactive species in an arcless, atmospheric-pressure, rf plasma discharge in a gas flowing through an annular or planar region between an electrically conducting chamber having a closed end and an open end and an electrode located within the chamber and disposed such that the annular or planar region is defined therebetween, whereby the reactive species flow toward the open end of the chamber; introducing a gaseous precursor species of the material into the reactive species in the region of the open end of the chamber, the precursor species being chosen such that it reacts with at least one of the reactive species, the reaction products thereof exiting the open end of the chamber as part of a gaseous atmospheric pressure jet; and placing the substrate in the path of the gaseous jet, whereby the reaction products generate a film of the material on the substrate.
Preferably, substantially all ions produced in the atmospheric-pressure, plasma discharge are consumed in the region where the gaseous jet containing the material exits through the open end of the chamber.
In another aspect of the present invention, in accordance with its objects and purposes, the apparatus for depositing a material onto a substrate hereof may include: an electrically conducting chamber having a closed end and an open end; an electrode located within the chamber defining thereby an annular or planar region; means for flowing gases through the annular or planar region; means for supplying rf energy to either of the central electrode or the electrically conducting chamber such that a continuous plasma discharge occurs between the electrode and the chamber, whereby reactive species are generated which flow toward the open end of the chamber; means for introducing a gaseous precursor species of the material into the reactive species in the region of the open end of the chamber, the gaseous precursor species being chosen such that the precursor species reacts with at least one of the reactive species, whereby a gaseous jet capable of forming the material exits through the open end of the chamber.
It is preferred that the central electrode is disposed collinear with the axis of the chamber.
It is also preferred that the electrode has longitudinal slots therein, each slot having a chosen width and a chosen depth.
Preferably also, substantially all ions generated in the atmospheric-pressure, plasma discharge are consumed in the region where the gaseous jet containing the material exits through the open end of the chamber.
Benefits and advantages of the present invention include the generation of an intense beam of the material to be deposited without exposing the substrate to ions and atomic species and to a high-temperature source.


REFERENCES:
patent: 5807614 (1998-09-01), Sindzingre et al.
S. E. Babayan et al., “Deposition of Silicon Dioxide Films with an Atmospheric-Pressure Plasma Jet,” Plasma Sources Sci. Technol. 7, 286 (Aug. 1998).

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