Catalytic breakdown of reactant gases in chemical vapor...

Details Catalytic breakdown of reactant gases in chemical vapor... Catalytic breakdown of reactant gases in chemical vapor...

2000-07-05

2001-10-23

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Coating of substrate containing semiconductor region or of...

C438S680000, C438S681000, C438S785000, C257S764000, C257S769000, C427S250000, C427S252000, C427S255120

Reexamination Certificate

active

06306776

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of films formed using chemical vapor deposition. More particularly, the present invention relates to the catalytic breakdown of reactant gases in chemical vapor deposition of films on semiconductor wafers.
BACKGROUND OF THE INVENTION
Chemical vapor deposition (CVD) is a commonly used means for depositing films on a substrate, such as a semiconductor wafer. Typically, CVD processes rely, at least in part, on thermal energy of the semiconductor to initiate the desired reactions. In some instances, however, it is desirable to reduce or minimize the temperature of a semiconductor wafer to protect the structures and materials that are already present.
One example of a material that can be damaged by excessive heat is a film of aluminum. If excessive heat is used after a layer of aluminum is already in place on a semiconductor wafer, the aluminum may diffuse into the adjoining materials, including the substrate itself. That diffusion can adversely affect the electrical performance of the aluminum and the adjoining layers, potentially leading to a defective semiconductor chip.
One approach at reducing the temperature, or thermal budget, necessary for high quality film deposition on semiconductor wafers is the use of plasma-enhanced CVD (PECVD). In that process, the inlet gases are excited by a radio frequency field that produces a plasma region containing free electrons, normal neutral gas molecules, ionized gas molecules, ionized portions of broken-up gas molecules, and free radicals. Although the additional energy imparted in PECVD processes does assist in the formation of thin films on the semiconductor substrates at lower temperatures, the PECVD processes do require the additional expense associated with purchasing and operating the plasma generating equipment. Furthermore, existing CVD equipment must often be extensively modified to accommodate the plasma generation or new equipment designed for PECVD must be purchased.
Another disadvantage of PECVD processes is that the additional energy present in the plasma region can result in ion implantation, energetic neutral embedment, sputtering and associated damage to the semiconductor wafer. In an attempt to address the problems caused by the additional energy in the plasma region, Markunas et al. described a process and equipment for remote plasma-enhanced CVD (RPECVD) in which the plasma region is located away from the substrate as described in U.S. Pat. No. 4,870,030. That process still relies, however, on plasma generation to reduce the thermal energy required for CVD. As a result, the additional costs associated with purchasing and operating plasma generating equipment still remain. Furthermore, the CVD chambers must be extensively modified to provide for remote plasma generation.
As a result, a need exists for a CVD process with a low thermal budget that can be used chemical vapor deposition of films on thermally-sensitive semiconductor wafers.
SUMMARY OF THE INVENTION
The present invention provides a method of depositing a film on a semiconductor wafer in a chemical vapor deposition process by contacting one or more activated gas precursors with one or more catalysts to produce one or more activated gases, and contacting the semiconductor wafer with the activated gases, wherein a film is formed on the semiconductor.
The catalysts may be heated to improve the production of activated gases using the activated gas precursors. One range of preferred catalyst temperatures is from about 300° C. to about 1200° C., more preferably about 500° C. to about 600° C.
The catalysts may be selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, gold, silver, mercury, rhenium, copper, tungsten, and combinations thereof.
The activated gas precursors are preferably hydrogen-bearing gases, for example, H
2
, HCl, SiH
4
, etc.
By using an activated gas, the temperature of the semiconductor may be held to a temperature of about 600° C. or less, more preferably about 450° C. or less, and even more preferably about 300° C. or less.
The present invention also provides an apparatus for depositing films on semiconductor wafers using chemical vapor deposition, the apparatus including a source of activated gas precursor in communication with the reaction chamber via a gas inlet, catalytic material located between the activated gas precursor source and the gas inlet, the catalytic material being in contact with the activated gas precursor as it moves from the activated gas precursor source to the reaction chamber.
The apparatus may also include a means for heating the catalyst to improve the production of activated gas. The means for heating may heat the catalytic material to temperatures from about 300° C. to about 1200° C., more preferably about 500° C. to about 600° C.
The catalyst may be selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, gold, silver, mercury, rhenium, copper, tungsten, and combinations thereof.
The activated gas precursor is preferably a hydrogen-bearing gas, for example, H
2
, HCl, SiH
4
, etc.
By using an activated gas, the apparatus may need to heat a semiconductor to a temperature of about 600° C. or less, more preferably about 450° C. or less, and even more preferably about 300° C. or less.
These and other features and advantages of the present invention are described in more detail below.


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Matsumura, “Study on catalytic chemical vapor deposition method to prepare hydrogenated amorphous silicon,” (Matsumura II),J. Appl. Phys., 65(11) (1989).

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