Method of fabricating a membrane structure
AssigneeNippon Telegraph & Telephone Public Corporation
InventorsSeitaro Matsuo, Mikiho Kiuchi, Misao Sekimoto
Life of this patent
Estimating the term…
Abstract
A thin film which becomes a membrane is formed over one major surface of a substrate by a plasma deposition process utilizing microwave electron cyclotron resonance. The substrate is then removed, other than a portion of the substrate which remains as a frame, so as to form a membrane structure. A dense and high quality membrane is formed at a low temperature and the internal stress of the membrane controlled by varying the conditions under which the plasma deposition process is carried out and by heat treating the thin film after its formation.
Claims12
A process for fabricating a membrane structure having a predetermined internal stress, comprising the steps of
- (a) providing a substrate having first and second surfaces;
- (b) forming by plasma deposition over the first surface of said substrate a thin film selected from the group consisting essentially of silicon nitride, boron nitride and silicon carbide, said plasma deposition utilizing microwave electron cyclotron resonance generated by microwave power within the range 150 to 250 watts, the temperature of said substrate after deposition reaching a value determined primarily by the heat generated by said plasma deposition;
- (c) heating said substrate, after deposition of said thin film on the first surface thereof, to a temperature in the range 300.degree.-800.degree. C., said temperature being higher than the temperature of said substrate after plasma deposition of said thin film and dependent upon the value of said microwave power within said range of 150 to 250 watts;
- and
- (d) removing a portion of said substrate to provide a frame supporting said thin film, whereby a membrane structure is formed having an internal stress in the range 0.5.times.10.sup.9 to 3.times.10.sup.9 dyne/cm.sup.2, the amount of said stress being determined by the temperature to which said substrate was heated in step (c) after deposition of said thin film.
Dependencies are inferred from the claim text.