Method and apparatus for preparing a silicon oxide film

An apparatus for forming a silicon oxide film, comprising:

• microwave generation means for generating microwaves;
• microwave transmission means for transmitting the microwaves generated by said microwave generation means;
• a plasma generation chamber having a wall, said plasma generation chamber being in communication with said microwave transmission means and having gas supply means and an opening defined at an end portion in opposing relationship with said microwave transmission means;
• a first excitation solenoid, disposed around said plasma generation chamber in coaxial relationship therewith, for producing a magnetic field for generating plasma from gas introduced into said plasma generation chamber by the resonant effect with said microwaves;
• a plasma reaction chamber for forming a silicon oxide film on a surface of a substrate disposed therein with said plasma, said plasma reaction chamber being in communication with said plasma generation chamber through said opening, and having a side wall, a substrate holder with a substrate holding surface on which the substrate is mounted, reactive gas supply means for supplying a reactive gas into said plasma reaction chamber, and gas exhaust means in communication with said plasma reaction chamber for exhausting gas in the plasma reaction chamber, said gas exhaust means having a vacuum pump;
• a second excitation solenoid, disposed in opposing relationship with said first excitation solenoid relative to the substrate, for producing a magnetic field whose polarity is opposite to that of the magnetic field produced by said first excitation solenoid so as to provide a cusp-shaped magnetic field in the vicinity of said surface of said substrate;
• a power supply for applying high frequency power to the substrate;
• pressure control means associated with said plasma reaction chamber for controlling gas pressure in said plasma reaction chamber so that the gas pressure is within the range of 7.times.10.sup.-3 to 1.times.10.sup.-1 Torr;
• and
• wherein said second solenoid has an end opposing the surface of said substrate on which a silicon oxide film is to be formed, which end is disposed at a distance of 10 cm or more from the surface of said substrate on which a film is to be formed, so that said cusp-shaped magnetic field has a cusp plane in a region between a distance of 10 cm above the surface of said substrate on which a silicon oxide film is to be formed and a distance of 10 cm below the surface of said substrate on which a silicon oxide film is to be formed.