This invention relates to a material of forming silicon oxide film, a silicon oxide film, a method for forming these oxide films and a semiconductor element.
In order to ensure an insulation from other region, an insulating film is generally formed on the surface or wiring layer of a semiconductor element or of a liquid crystal display device. In the formation of an insulating film for covering a wiring layer, a method of depositing a silicon compound film by means of thermal oxidation or CVD method for instance is generally employed. However, an insulating film to be formed by means of CVD method is relatively high in dielectric constant, i.e. approximately 4.2. Therefore, there is a need for a development of an insulating film having lower dielectric constant which is suited for use in a semiconductor device of high capacity and high-speed.
A coating type silicone polymer has been developed for lowering the dielectric constant. However, this coating type silicone polymer is still high in dielectric constant, i.e. approximately 3.0, and is not high enough in heat resistance. On the other hand, it is now studied to lower the dielectric constant of an insulating film by increasing the free volume of the film by introducing an air bubble into the film. However, this method is accompanied with problems that it is difficult to control the volume of the air bubble and that if the air bubble is too large, water may be adsorbed in the air bubble, thus resulting in an increase in dielectric constant of the insulating film. Moreover, the water in the air bubble may be evaporated during a high temperature processing, thus giving rise to a problem of the disconnection of wiring.
As illustrated above, the conventional insulating film to be formed by means of CVD method is too high, i.e. approximately 4.2, in dielectric constant. Even with the coating type silicone polymer, it is difficult to obtain an insulating film exhibiting a sufficiently low dielectric constant. Moreover, the coating type silicone polymer is accompanied with a problem of heat resistance and hence is not suited for use as an insulating film for a semiconductor device.