Coating processes – Coating by vapor – gas – or smoke – Mixture of vapors or gases utilized
Patent
1989-09-05
1991-11-05
Beck, Shrive
Coating processes
Coating by vapor, gas, or smoke
Mixture of vapors or gases utilized
4272481, 427255, 4272552, C23C 1640, C23C 1644, C23C 1646, C23C 1652
Patent
active
050630865
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the deposition of films of materials, such as polysilicon or silicon dioxide, on substrates, using a low-pressure chemical vapour deposition (LPCVD) process. Such deposition techniques may be used in the fabrication of integrated circuits. The low-pressure deposition process is then particularly advantageous, as it allows a high IC wafer throughput to be achieved.
2. Description of the Related Art
Although deposition of some materials by the LPCVD process is simple, for some multi-compound reactions serious problems are encountered. One example is the deposition of silicon dioxide by the reaction of silane with oxygen, in which non-uniformity of the resultant films across the wafers is a problem. The same problem also arises with certain other compounds.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an LPCVD process in which such problem is alleviated.
According to one aspect of the invention there is provided a low-pressure chemical vapour deposition process for depositing a film of a material on at least one major surface of a substrate, the process comprising the steps of mounting the substrate in a deposition chamber; feeding into the chmber at least one reactant gas for forming the film while maintaining the pressure in the chamber at a level below 10 mTorr, the substrate being so orientated that the general direction of gas flow is substantially perpendicular to said surface of the substrate; and applying heat to cause reaction of the gas or gases to form the film on said surface.
According to another aspect of the invention there is provided apparatus for forming a film of a material on at least one major surface of a substrate, the apparatus comprising a deposition chamber; means to maintain a pressure below 10 mTorr in the chamber; means to feed at least one reactant gas into the chamber so that the gas or gases flow through the chamber; means to support the substrate within the chamber so that said surface is substantially perpendicular to the gas flow; and means to apply heat to cause reaction of the gas or gases to form said film on said surface.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein
FIG. 1 is a schematic view in cross-section through a known vacuum deposition chamber, and
FIG. 2 is a schematic view showing schematically the gas flow around substrates mounted in the chamber of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, a conventional deposition apparatus comprises a deposition chamber 1 having a closure 2 at one of its ends and a connection 3 to a pump 4 at the other end. An inlet 5 is provided at the closure end, so that reactant gas or gases can be fed into the chamber. The resultant gas flow will be generally in the direction of arrows 6. Substrates 7 on which films are to be deposited are mounted in the chamber with their major surfaces substantially perpendicular to the general gas flow.
Films are deposited on the major surfaces of the substrates by heating the gas or gases at the substrate surfaces to cause the required reaction.
A typical deposition process involves the reaction of silane gas with oxygen to produce a silicon dioxide film i.e., and the reaction temperature is around 420.degree. C.
A problem which is encountered with that process is illustrated schematically in FIG. 2. The general direction is represented by arrows 6, as above. It will be seen that the main gas flow takes place generally in an annular region 8 around the edges of the substrates. However, in order to deposit the required films on the major surfaces of the substrates, some part of the gas flow must make contact with those surfaces, as indicated by arrows 9.
As the reactant gases diffuse from the annular region 8 towards the centre of a substrate, the gases become partially used up by the reaction at the surface. If the rate of reaction is grea
REFERENCES:
patent: 4239811 (1980-12-01), Kentage
patent: 4268538 (1981-05-01), Toole et al.
patent: 4513026 (1985-04-01), Miyamoto et al.
patent: 4780334 (1988-10-01), Ackerman
patent: 4810673 (1989-03-01), Freeman
patent: 4832986 (1989-05-01), Gladfeller et al.
patent: 4849259 (1989-07-01), Biro et al.
Blocher, Deposition Tech. for Films & Coatings, (Noyes, Park Ridge N.J.) c. 1982, pp. 335, 351-356.
Beck Shrive
Burke Margaret
The General Electric Company p.l.c.
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