Gas-sensing semiconductor devices
First Claim
1. A smart sensor comprising a gas-sensing device monolithically integrated with an electronic circuit incorporating control elements for drive, control and transducing functions, wherein the sensor has been fabricated using CMOS, Bi-CMOS or SOI based technology and including a fabrication step in which a layer of tungsten is applied to form simultaneously both (i) a metallization layer for contacts and interconnects between the control elements in the electronic circuit and (ii) a heater of the gas-sensing device.
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Abstract
A gas-sensing semiconductor device is fabricated on a silicon substrate having a thin silicon oxide insulating layer in which a resistive heater made of a CMOS compatible high temperature metal is embedded. The high temperature metal is tungsten. The device includes at least one sensing area provided with a gas-sensitive layer separated from the heater by an insulating layer. As one of the final fabrication steps, the substrate is back-etched so as to form a thin membrane in the sensing area. Except for the back-etch and the gas-sensitive layer formation, that are carried out post-CMOS, all other layers, including the tungsten resistive heater, are made using a CMOS process employing tungsten metallisation. The device can be monolithically integrated with the drive, control and transducing circuitry using low cost CMOS processing. The heater, the insulating layer and other layers are made within the CMOS sequence and they do not require extra masks or processing.
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Citations
34 Claims
- 1. A smart sensor comprising a gas-sensing device monolithically integrated with an electronic circuit incorporating control elements for drive, control and transducing functions, wherein the sensor has been fabricated using CMOS, Bi-CMOS or SOI based technology and including a fabrication step in which a layer of tungsten is applied to form simultaneously both (i) a metallization layer for contacts and interconnects between the control elements in the electronic circuit and (ii) a heater of the gas-sensing device.
- 27. A gas-sensing semiconductor device comprising a semiconductor substrate, at least one sensing area provided with a gas-sensitive layer and a heater for heating the gas-sensitive layer to promote gas reaction with the gas-sensitive layer, and a sensor for providing an electrical output indicative of gas reaction with the gas-sensitive layer, wherein the heater has in the heater'"'"'s composition at least one layer of tungsten, and wherein the sensor incorporates laterally spaced tungsten electrodes in the vicinity of the gas-sensitive layer.
- 30. A method of fabricating a smart sensor, comprising a gas-sensing device monolithically integrated with an electronic circuit incorporating control elements for drive, control and transducing functions using CMOS, Bi-CMOS or SOI-based technology, wherein the method includes applying a layer of tungsten to form simultaneously both (i) a metallization layer for contacts and interconnects between the control elements in the electronic circuit and (ii) a heater of the gas-sensing device.
Specification