INTEGRATED CMOS POROUS SENSOR
A single chip wireless sensor comprises a microcontroller connected by a transmit/receive interface to a wireless antenna. The microcontroller is also connected to an 8 kB RAM, a USB interface, an RS232 interface, 64 kB flash memory, and a 32 kHz crystal. The device senses humidity and temperature, and a humidity sensor is connected by an 18 bit ΣΔ A-to-D converter to the microcontroller and a temperature sensor is connected by a 12 bit SAR A-to-D converter to the microcontroller. The device is an integrated chip manufactured in a single process in which both the electronics and sensor components are manufactured using standard CMOS processing techniques, applied to achieve both electronic and sensing components in an integrated process.
1 . An integrated sensor device comprising:
MOS circuits in a semiconductor substrate,
an interconnect stack comprising interconnect levels having interconnect conductors and insulating dielectric, said interconnect levels being over the substrate and interconnecting the MOS circuits,
a sensor including:
electrodes embedded in the insulating dielectric and being integrally formed with the interconnect conductors, and
a porous material for ingress of gas or humidity being sensed, and
wherein the MOS circuits include an A-to-D converter for processing signals from the sensor electrodes, said A-to-D converter converting analog data to digital data, the digital data utilized when performing gas concentration measurements obtained by detecting together changes of conductivity of the sensor porous material and changes of dielectric constant of the sensor porous material.
2 . The integrated sensor device as claimed in claim 1 , wherein the sensor porous material includes an oxide film deposited over a passivation layer, and the A-to-D converter includes differential capacitors.
3 . The integrated sensor device as claimed in claim 2 , wherein the sensor porous material includes zinc oxide and ferric oxide.
4 . The integrated sensor device as claimed in claim 1 , wherein the sensor porous material further includes a resistor interconnecting the electrodes.
5 . The integrated sensor device as claimed in claim 4 , wherein the resistor is of ferric oxide and zinc oxide composition.
6 . The integrated sensor device as claimed in claim 2 , wherein the passivation layer is of Si 3 N 4 composition.
7 . The integrated sensor device as claimed in claim 1 , wherein the MOS circuits include a temperature sensor.
8 . The integrated sensor device as claimed in claim 1 , wherein the MOS circuits include a temperature sensor, and wherein the temperature sensor comprises a PNP transistor.
9 . The integrated sensor device as claimed in claim 1 , wherein the MOS circuits include a temperature sensor, and wherein the MOS circuits include a microcontroller for processing gas or humidity signals from the gas or humidity sensor and temperature signals from the temperature sensor to provide an enhanced output.
10 . The integrated sensor device as claimed in claim 9 , wherein the enhanced output is temperature-corrected gas or humidity readings.
11 . The integrated sensor device as claimed in claim 1 , wherein the A-to-D converter comprises an array of dummy capacitors with a constant topography surrounding active A-to-D converter capacitors.
12 . The integrated sensor device as claimed in claim 1 , further comprising a light emitting diode.
13 . The integrated sensor device as claimed in claim 12 , wherein said diode is formed in a deep trench to a lower interconnect level lateral of the sensor electrodes.
14 . The integrated sensor device as claimed in claim 1 , wherein the device comprises a photo-detector diode.
15 . The integrated sensor device as claimed in claim 14 , wherein said diode is in a deep trench in a lower interconnect level lateral of the sensor electrodes.
16 . The integrated sensor device as claimed in claim 1 , wherein the MOS circuits include a wireless transceiver.
17 . The integrated sensor device as claimed in claim 16 , wherein the wireless transceiver is for communication with other nodes in a network, and it comprises a means for switching channel frequency according to a low frequency channel switching scheme upon detection of interference.
18 . The integrated sensor device as claimed in claim 1 , wherein the device includes a low noise amplifier.
19 . The integrated sensor device as claimed in claim 1 , wherein the device includes a low noise amplifier, and wherein the low noise amplifier comprises a strained silicon MOS device beneath a MOS conductor.