Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
1999-07-26
2001-08-07
Mills, Gregory (Department: 1763)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C438S758000
Reexamination Certificate
active
06270862
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a system and a method for delivering reactants to a substrate in a high density plasma chemical vapor deposition reactor. More particularly, the present invention relates to a system and a method for focusing the delivery of reactants via a gas injection system towards a substrate during processing of the substrate in a high density plasma chemical vapor deposition reactor and thermally controlling the gas injection hardware.
BACKGROUND OF THE INVENTION
Vacuum processing chambers are generally used for chemical vapor depositing (CVD) of materials on substrates by supplying process gas to the vacuum chamber and applying an RF field to the gas. A number of gas distribution systems for integrated circuit processing are known, but the vast majority of known systems are designed for plasma etching or for plasma enhanced CVD (PECVD). Conventional gas distribution systems typically deliver reactants at relatively low flow rates. Showerhead gas injection and diffusive transport systems are commonly used to ensure even distribution over the substrate.
These known systems are not optimized for high density plasma CVD (HDPCVD) processes, such as encapsulation and intermetal dielectric gas filling. In HDPCVD it is important to focus the delivery of reactants such as silane related species onto a substrate, because silane and its radicals, e.g., SiH
3
, SiH
2
, SiH, and so on, have high sticking coefficients. Directing the silane preferentially onto the substrate is advantageous because it maximizes the substrate deposition rate and minimizes film deposits on various internal surfaces of the reactor.
Efficient silane utilization in HDPCVD requires the reactant gas to be directed onto the substrate from close proximity, with a high flow rate, and even distribution, to achieve high deposition rates with good uniformity and film quality. A showerhead system positioned close to the substrate is not ideal because it limits the extent of ion diffusion within the plasma which can be detrimental to plasma and deposition uniformity. Diffusive systems are not adequate for HDPCVD because they cause deposition of reactants on surfaces other than the substrate being processed. Deposition on non-substrate surfaces results in an inefficient use of the reactant gases, which necessitates higher flow rates to reach the desired deposition rate and substrate throughput. These higher flow rates are costly because of both the additional gas used and the increased pumping capacity necessary for maintaining low pressure within the processing chamber. Furthermore, deposition on non-substrate surfaces within the chamber can lead to particulate problems (flaking) caused by differential expansion between the films and chamber interior surfaces, and process shifts due to changing wall conditions. Consequently, the chamber must be cleared more often to remove these chamber deposits, which further reduce substrate throughput.
A plasma etching system has been proposed in which gas inlets supply gas into a plasma processing chamber. As shown in
FIG. 1
, this system includes a plasma source
110
for generating a plasma in a chamber
140
and a gas ring
167
with attached gas inlets supplying process gas into the processing chamber
140
for processing a substrate
120
on a substrate support
130
. This type of system may also include an additional gas ring
160
. Conventionally, the deposition rate in such a system is increased by concentrating the process gas above the substrate
120
. This is typically done by changing the distance from the gas ring
167
to the substrate
120
. The more the process gas is concentrated toward the area above the center of the substrate, the larger the peak deposition rate. Unfortunately, in concentrating the process gas near the center of the substrate, the deposition rate on the outer portion of the substrate may not increase as much as the center, which leads to a potential decrease in deposition uniformity.
There is thus a need for a gas distribution system which is optimized for HDPCVD and which provides both an improved deposition rate and an improved deposition uniformity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide gas distribution system for HDPCVD which provides uniform, high flow rate delivery of reactant gases focused preferentially onto the substrate surface, to both maximize deposition rate on the substrate and to minimize the chamber cleaning requirements. It is another object of the present invention to thermally control the gas injection hardware to reduce particle counts within the chamber by minimizing flaking from internal chamber surfaces and by minimizing particle formation caused by thermal pyrolysis within the injection hardware. It is yet another object of the present invention to improve the deposition rate and uniformity of deposition compared to conventional gas distribution systems.
According to one aspect of the invention, a plasma processing system is provided for processing a substrate. The plasma processing system includes a plasma processing chamber, a substrate holder for supporting a substrate within the processing chamber, a dielectric member forming a wall of the processing chamber, a gas supply for supplying process gas (e.g., one or more reactant gases and/or one or more inert gases) into the chamber and towards the substrate, and an RF energy source which inductively couples RF energy through the dielectric member and into the chamber to energize the process gas into a plasma state. The gas supply may include one or more gas rings with or without injectors injecting at least some of the process gas into the processing chamber so as to intersect an exposed surface of the substrate. A cooling mechanism may also be provided to cool the gas supply during processing to minimize film flaking from the gas ring surfaces and prevent excessive heating which could lead to unwanted thermal decomposition of the process gas.
According to another aspect of the present invention, a method is provided for processing a substrate. The method includes placing a substrate on a substrate holder in a processing chamber, an interior surface of a dielectric member forming a wall of the process chamber and facing the substrate holder, supplying process gas into the processing chamber, and energizing the dielectric member into the processing chamber. Substrates may be consecutively processed in the processing chamber by contacting the substrate with plasma gas. The process gas may be injected into the processing chamber such that at least some of the process gas is directed towards the substrate. In addition, the gas supply hardware may be cooled during processing to minimize flaking and preventing excessive heating.
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Barnes Michael
Berney Butch
McMillin Brian
Nguyen Huong
Alejandro Luz L.
Burns Doane , Swecker, Mathis LLP
Lam Research Corporation
Mills Gregory
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