1. Field of the Invention
The present invention generally relates to a method of forming an interlayer insulating film, and more particularly to an improved method thereof wherein the film can be formed uniformly on a substrate of large size.
2. Description of the Background Art
In a method of manufacturing a semiconductor device, a step of forming an interlayer insulating film is indispensable. FIGS. 5A-5C are cross sectional views of a semiconductor device in respective process steps of forming a conventional interlayer insulating film.
Referring to FIG. 5A, an aluminum interconnection pattern 12 is formed on a silicon substrate 11. A first plasma oxide film 13 is then deposited on the silicon substrate 11 such that it covers the surface of the aluminum interconnection pattern.
Referring to FIG. 5B, a silicon oxide film 14 (interlayer insulating film) is formed by chemical vapor deposition using mixed gas including silane gas (SiH.sub.4) and hydrogen peroxide to cover the aluminum interconnection pattern.
Referring to FIG. 5C, a second plasma oxide film 15 is formed on the semiconductor substrate 11 to cover the silicon oxide film 14, thereby a planar insulating film is obtained.
The silicon oxide film 14 formed by CVD using silane gas and hydrogen peroxide can fill the space less than 0.25 .mu.m between densely patterned interconnections. Further, the silicon oxide 14 is excellent in fluidity and therefore shows a self planarization feature, so that this method attracts attention as the next generation way for planarizing an interlayer insulating film alternative to the conventional way employing SOG (Spin on glass). (Technical Digest of IEDM 1994, Proceedings of DUMIC Conference, 1995)
A silicon oxide film has been formed as described above by CVD using silane gas and hydrogen peroxide. However, in the LSI process, as the diameter of a substrate wafer becomes larger, to deposit an uniform film over such a large wafer has become extremely difficult. Even if an interlayer insulating film is formed by CVD using silane gas and hydrogen peroxide as described, the CVD method still has the same problem. Although attempts have been made to improve the uniformity of film thickness by modifying the structure of a reaction chamber and adjusting the conditions of forming a film, an appropriate method has not been established.