초록 ▼

A combustible gas sensor that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 .mu.m thick.times.10 .mu.m wide.times.100, 250, 500, or 1000 .mu.m

A combustible gas sensor that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 .mu.m thick.times.10 .mu.m wide.times.100, 250, 500, or 1000 .mu.m-long polycrystalline Si; some are overcoated with a 0.25 .mu.m-thick protective CVD Si.sub.3 N.sub.4 layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac).sub.2 onto microfilaments resistively heated to approximately 500.degree. C.; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300.degree. C. (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H.sub.2 concentrations between 100 ppm and 1% in an 80/20 N.sub.2 /O.sub.2 mixture. Other catalytic materials can also be used.

대표청구항 ▼

[ We claim:] [1.] A sensor for a combustible gas comprising:a first pair of first and second filaments wherein the filaments are disposed above and parallel to a semiconductor substrate comprising Si with an airgap between the base of the filaments and a surface of the substrate and wherein the firs

[ We claim:] [1.] A sensor for a combustible gas comprising:a first pair of first and second filaments wherein the filaments are disposed above and parallel to a semiconductor substrate comprising Si with an airgap between the base of the filaments and a surface of the substrate and wherein the first and second filaments each comprise a core of conductive poly-silicon surrounded by a protective shell of a high resistance material, each of the first and second filaments possessing the same resistance-temperature characteristic, with only the first filament presenting a catalytic surface to the combustible gas, the catalytic surface being electrically isolated from the conductive core;means to resistively heat separately the first and second filaments to a first same temperature;means to measure the amount of power delivered to the first and second filaments to achieve the first same temperature; andmeans to determine the amount of the combustible gas as a function of the difference in the amounts of power delivered to the first and second filaments.