Method of stabilizing the surface properties of objects to be thermally treated in a vacuum

US5400489A · kind A · utility

Inventors

• Frank Hegner · Bad Kötzting, DE
• Ulfert Drewes · Bad Hersfeld, DE

Key dates

• Filing date: Oct 30, 1992
• Grant date: Mar 28, 1995
• Expiry date: Oct 30, 2012

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T29/49103
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

To avoid any deterioration of the surface properties of objects of ceramic, glass, or a single-crystal insulating material which are subjected to a vacuum temperature process, a thin layer of a spin-on glass solution with a silicon-dioxide equivalent of not more than 10% is applied to the objects by spinning or spraying prior to the vacuum temperature process. This is particularly important to avoid the strong moisture dependence of capacitive or resistive pressure sensors having a substrate and a diaphragm to be joined together, forming a chamber sealed at least at the edge. The diaphragm is covered with a layer of silicon carbide, niobium, or tantalum serving as one capacitor electrode, or the surface portion of the diaphragm which will lie within the chamber is coated with at least one strain gage; the portion of the substrate surface which will lie within the chamber is coated with at least one additional capacitor electrode or, in the case of the resistive pressure sensor, not coated therewith; over the entire surface portion of the substrate and diaphragm thus coated, a thin layer of the spin-on glass solution is applied and dried; contact is made to the capacitor electrodes …