Thermal fluid flow sensor and method of manufacturing the same
View Patent ↗In a thermal sensor with a detection part and a circuit part formed on the same substrate, an insulating film for protection of the circuit part causes problems of lowering in sensitivity of a heater, deterioration in accuracy due to variation of a residual stress in the detection part, etc. A layered film including insulating films is formed on a heating resistor, an intermediate layer is formed thereon, and a layered film including insulating films is formed further thereon. The intermediate layer is specified to be a layer made up of any one of aluminum nitride, aluminum oxide, silicon carbide, titanium nitride, tungsten nitride, and titanium tungsten. This configuration enables the layered film on the upper part of the detection part to be removed using the intermediate layer as an etch stop layer, which solves problems of lowering in sensitivity, a variation in residual stress, etc. resulting from these.
1. A thermal sensor, comprising:
a semiconductor substrate;
a first layered film that is provided above the semiconductor substrate and includes a plurality of insulating films;
a detection part that is provided on the first layered film and has a heating resistor;
a circuit part that is provided on the semiconductor substrate and has a control circuit for controlling the heating resistor;
a second layered film that is provided on the heating resistor and above the control circuit, and includes a plurality of insulating films;
an intermediate layer provided on the second layered film; and
a third layered film that is provided on the intermediate layer and above the control circuit, and includes a plurality of insulating films;
wherein the intermediate layer is made up of any one of aluminum nitride, aluminum oxide, silicon carbide, titanium nitride, tungsten nitride, and titanium tungsten.
2. The thermal sensor according to claim 1 ,
wherein the intermediate layer is not provided above the detection part but is provided above the control circuit.
3. The thermal sensor according to claim 1 ,
wherein the intermediate layer is provided both above the detection part and above the control circuit.
4. The thermal sensor according to claim 1 , further comprising:
a wiring layer for connecting the heating resistor and the control circuit,
wherein the wiring layer and the control circuit are brought into conduction through a metal layer provided on the same layer as that of the heating resistor.
5. The thermal sensor according to claim 1 , further comprising:
a wiring layer for connecting the heating resistor and the control circuit,
wherein the electrode for connecting the control circuit and the outside of the thermal sensor is formed on the wiring layer.
6. The thermal sensor according to claim 1 ,
wherein the film thickness of the intermediate layer is less than or equal to 200 nm.
7. The thermal sensor according to claim 6 ,
wherein the film thickness of the intermediate layer is not less than 20 nm and not more than 100 nm.
8. A thermal sensor, comprising:
a semiconductor substrate;
a first layered film that is provided above the semiconductor substrate and includes a plurality of insulating films;
a detection part that is provided on the first layered film and has a heating resistor;
a circuit part that is provided on the semiconductor substrate and has a control circuit for controlling the heating resistor;
a second layered film that is provided on the heating resistor and above the circuit control, and includes a plurality of insulating films;
an intermediate layer provided on the second layered film; and
a third layered film that is provided in a region on the intermediate layer from which a portion above the detection part is excluded, and includes a plurality of insulating filmss.
9. The thermal sensor according to claim 8 ,
wherein the intermediate layer is not provided above the detection part but is provided above the control circuit.
10. The thermal sensor according to claim 8 ,
wherein the intermediate layer is made up of a material whose selection ratio in dry etching with a fluorine containing gas or in wet etching with a hydrofluoric acid aqueous solution is larger than those of any insulating films included in the third layered film.