Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Responsive to non-optical – non-electrical signal
Patent
1999-09-14
2000-08-29
Wojiechowicz, Edward
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Responsive to non-optical, non-electrical signal
257347, 257401, 257414, H01L 2972
Patent
active
061112801
DESCRIPTION:
BRIEF SUMMARY
This invention relates to gas-sensing semiconductor devices for detecting the presence and/or concentration of one or more gases.
It is known to fabricate a gas microsensor within a semiconductor device. In particular it is known to produce high-temperature metal oxide conductimetric sensors using alumina substrates and semi-manual production methods. Recently attempts have been made to manufacture silicon versions of such sensors employing a platinum heater integrated with a thin insulating membrane of oxide or nitride. Such sensors offer a lower power consumption than conventional sensors when operating at 300.degree. C. to 600.degree. C. However the two part deposition of the membrane of such a sensor and the deposition of the metal heater layer sandwiched between the two membrane layers makes the fabrication process incompatible with integrated circuit technology. There has also been much interest in the development of MOSFET potentiometric sensors using catalytic gates, for example of palladium which run at temperatures of between 120.degree. C. and 200.degree. C. However such sensors will have limited application due to their inefficiency and relatively high cost.
It is an object of the invention to provide an improved gas-sensing semiconductor device which can be produced at low cost using conventional bulk fabrication processes.
According to the present invention there is provided a gas-sensing semiconductor device as defined by the accompanying claims.
Such a gas-sensing semiconductor device can be produced so as to have very low power consumption using a series of fabrication steps compatible with known CMOS SOI (silicon on insulator) technology for integrated circuits. As compared with conventional planar integrated gas sensors, this considerably simplifies the fabrication of the device, and thus decreases the manufacturing cost. Furthermore the device may be integrated with processing circuitry, such as a processor unit and a driving circuit, on a single chip so as to produce a "smart" gas microsensor. Unlike in conventional gas microsensors, the heater can be produced without requiring any fabrication steps in addition to those already employed in the IC processing. The use of SOI technology also allows accurate bipolar temperature sensors to be integrated into the device.
SOI technology is commonly based on wafer bonding or implantation of oxygen deep into the substrate followed by epitaxial growth (known as SIMOX techniques). CMOS SOI integrated circuits may be fabricated by forming a thin layer of insulating material, such as silicon oxide, on the semiconductor substrate followed by forming of a thin silicon layer on top of the insulating layer. Other insulating materials can be used in place of silicon oxide, such as silicon nitride or a combination of silicon oxide and silicon nitride. Individual semiconductor devices, such as MOSFET's, are then fabricated within the thin silicon layer using known fabrication steps. Because the devices are formed within a very thin silicon/insulator membrane, of 0.2 .mu.m thickness or example, SOI technology results in high speed/low power CMOS performance, as ell as providing simple and efficient device isolation, reduced parasitic capacitances, latch-up elimination and reduced short-channel effects. In addition fully depleted devices (with an ultra-thin SOI layer) have been reported to have attractive features. They do not exhibit kink phenomena, have a sharp sub-threshold slope, and are stable in terms of dynamic floating body effects relating to impact-ionisation and charge-pumping phenomena The SOI transistors also possess a lower off-state leakage current by a factor of about 10-100 when compared with conventional bulk silicon devices. This is important in reducing the stand-by power dissipation. In addition SOI technology enables device operation at higher temperatures than conventional devices, mainly due to reduced leakage currents.
This allows very high temperatures in the membrane area (up to 600.degree. C. for some sensing materials to react w
REFERENCES:
patent: 4502938 (1985-03-01), Covington et al.
patent: 4878015 (1989-10-01), Schmidt et al.
S. Wessel, et al.; Microelectronics Journal, 23, 1992, 451-456, "A CMOS Thermally-Isolated Heater Structure as a Substrate for Semiconductor Gas Sensors".
Search Report for Application No. GB 9700723.1; Dated Mar. 20, 1997.
Gardner Julian
Udrea Florin
University of Warwick
Wojiechowicz Edward
LandOfFree
Gas-sensing semiconductor devices does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas-sensing semiconductor devices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas-sensing semiconductor devices will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1252588