Semiconductor gas sensor having thermally isolated site

Claim 2

A gas sensor device for detecting a species in an ambient gas and having a localized, thermally isolated gas interaction site, said device comprising a silicon substrate including a film support region at said gas interaction site and a region adjacent the film support region, said substrate being etchedly recessed opposite the gas interaction site such that the thickness of the film support region is substantially reduced relative to the adjacent region, an electrically insulative coating overlying the substrate film support region, a gas sensitive semiconductor thin film supported upon the insulative coating at said gas interaction site and situated for exposure to ambient gas, and means at the gas interaction site for selectively heating the gas sensitive thin film to a temperature operative for detecting the species, whereby heat flow from the gas interaction site through the substrate is substantially reduced as a result of the reduced thickness of the substrate film support region.

Claim 3

A gas sensor device for detecting a species in an ambient gas and having a localized, thermally isolated, independently heated qas interaction site, said device comprisinq a silicon substrate includinq a film support region at said gas interaction site and an adjacent region about the film support region, said substrate having a first major face whereupon is located the gas interaction site and an opposite second major face, said second face being etchedly recessed opposite the gas interaction site such that the thickness at the film support region is substantially reduced relative to the adjacent region, an electrically insulative silicon dioxide coating overlying the substrate first face at the film support region, a gas sensitive semiconductor thin film supported upon the insulative coating at said gas interaction site and situated for exposure to ambient gas, and electrical resistance means interposed between said substrate and said gas sensitive thin film at the gas interaction site for heating the gas sensitive thin film to a temperature operative for detecting the species, said means being electrically insulated from the gas sensitive thin film by a layer of said insulative coating, whereby heat flow from the gas interaction site to the adjacent region is substantially reduced as a result of the reduced thickness of the substrate film support region.

Claim 4

A gas sensor device for detecting a species in an ambient gas and having a localized, thermally isolated, independently heated qas interaction site, said device comprisinq a silicon substrate includinq a film support region at said gas interaction site and an adjacent region about the film support region, said substrate having a first major face whereupon is located the gas interaction site and an opposite second major face, said second face being etchedly recessed opposite the gas interaction site such that the thickness at the film support region is substantially reduced relative to the adjacent region, an electrically insulative silicon dioxide coating overlying the substrate first face at the film support region, a gas sensitive semiconductor thin film supported upon the insulative coating at said gas interaction site and situated for exposure to ambient gas, and electrical resistance means interposed between said substrate and said gas sensitive thin film at the gas interaction site for heating the gas sensitive thin film to a temperature operative for detecting the species, said means being electrically insulated from the gas sensitive thin film by a layer of said insulative coating, whereby heat flow from the gas interaction site to the adjacent region is substantially reduced as a result of the reduced thickness of the substrate film support region.

Claim 5

A gas sensor device for detecting a species in an ambient gas and having a localized, thermally isolated, independently heated gas interaction site, said device comprising a silicon substrate including a film support region at said gas interaction site and an adjacent region surrounding the film support region, said substrate having a first major face and an opposite second major face, said second face being etchedly recessed opposite the gas interaction site such that the thickness at the film support region is substantially reduced relative to the adjacent region, an electrically insulative silicon dioxide coating overlying the substrate first face including the film support region, a gas sensitive semiconductor thin film supported upon the insulative coating at said gas interaction site and situated for exposure to ambient gas, polysilicon heating element interposed between said substrate and said gas sensitive thin film at the gas interaction site for heating the gas sensitive thin film, said element being electrically insulated from the gas sensitive thin film by a first layer of said insulative coating and from the substrate by a second layet of said insulative coating, means for connecting the polysilicon element to an electrical power source for resistively heating the element to a temperature operative for detecting the species, whereupon heat loss into the substrate is reduced as a result of the reduced thickness of the substrate film support region, and means for connecting the thin film to a remote electrical resistance measurement means for measuring the electrical resistance of the film, which resistance provides a basis for detecting the presence of the species in the gas.

Claim 6

A gas sensor device for detecting a species in an ambient gas and having a localized, thermally isolated, independently heated gas interaction site, said device comprising a silicon substrate including a film support region at said gas interaction site and an adjacent region surrounding the film support region, said substrate having a first major face and an opposite second major face, said second face being etchedly recessed opposite the gas interaction site such that the thickness at the film support region is substantially reduced relative to the adjacent region, an electrically insulative silicon dioxide coating overlying the substrate first face including the film support region, a gas sensitive semiconductor thin film supported upon the insulative coating at said gas interaction site and situated for exposure to ambient gas, polysilicon heating element interposed between said substrate and said gas sensitive thin film at the gas interaction site for heating the gas sensitive thin film, said element being electrically insulated from the gas sensitive thin film by a first layer of said insulative coating and from the substrate by a second layet of said insulative coating, means for connecting the polysilicon element to an electrical power source for resistively heating the element to a temperature operative for detecting the species, whereupon heat loss into the substrate is reduced as a result of the reduced thickness of the substrate film support region, and means for connecting the thin film to a remote electrical resistance measurement means for measuring the electrical resistance of the film, which resistance provides a basis for detecting the presence of the species in the gas.