Measuring and testing – Gas analysis – Detector detail
Reexamination Certificate
1999-10-08
2002-07-16
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
Detector detail
C073S025030, C324S071500, C257S253000
Reexamination Certificate
active
06418784
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to combustible gas sensors, and more specifically, to a gas sensor in combination with a temperature detector.
BACKGROUND
Improved methods for monitoring catalysts are desired an automotive vehicles to provide accurate hydrocarbon measurements to the engine controller. Because of the high temperatures associated with catalysts the technologies available for such applications are severely limited.
Wide band gap semiconductor silicon carbide (SiC) offers advantages over conventional semiconductors such as silicon and galium arsenide for high temperature, harsh environment and high speed applications. Advances in SiC single crystal growth technology, resulting in increased wafer size of higher quality material with reduced costs has provided an area of particular interest in the development of gas sensors.
Two types of gas sensors developed using SiC technology include metal oxide semiconductors (MOS) and metal insulator semiconductors (MIS). Generally, the MOS gas sensor consists of a semiconductor substrate with an ohmic contact on one side and with the other side covered by a SiO
2
insulating layer with a metal gate on top. The metal gate is composed of a metal capable of catalyzing the oxidation of combustible gasses. As a result of the catalytic redox reaction on the gate surface, certain atomic and molecular species are generated which can diffuse through the porous gate to the metal gate/insulator interface where they can ionize. These ions can penetrate through the insulator thereby changing the potential distribution across the device. This changes the potential of the insulator/gate interface and thus the depletion layer inside the semiconductor which in turn shifts the voltage dependent AC admittance characteristic of the device shift along the voltage axis. For a MIS device, the DC resistance characteristics shifts along the voltage axis.
MOS and MIS sensors have an output dependent on temperature of catalytic gate. Therefore, it would be desirable to simultaneously measure temperature and the gas concentration to more accurately determine gas concentration.
SUMMARY OF THE INVENTION
The present invention combines a gas sensing structure and a temperature detecting structure within the same sensor. In one aspect of the present invention, a sensor includes a substrate and a catalytic gate electrode disposed on the substrate. The catalytic gate electrode has a first end having a first contact pad and a second end having a second contact pad. A meander is placed between the first contact and the second contact. A third contact pad is coupled to the underside of the substrate. The temperature is measured between the first contact pad and second contact pad while the gas concentration is sensed between the gate electrode and the third contact.
In a further aspect of the invention, a second meander may be placed adjacent to the first meander. The second meander may be used as a heater to heat the device. A heater may be desirable during a cold startup of the vehicle.
In yet another aspect of the invention, a method of sensing gas concentration and temperature comprises the steps of:
measuring a resistance of a meander on a substrate;
determining a temperature associated with said resistance;
measuring an electrical characteristic between the meander and a third contact on a back side of a substrate; and
determining a gas concentration in response to said electrical characteristic and said temperature.
One advantage of the invention is that because the temperature of the catalytic gate is known, the output of the sensor and gas sensor may more accurately be determined. The colocation of the temperature sensor and gas sensor allows very accurate readings of the temperature at the sensor.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.
REFERENCES:
patent: 4058368 (1977-11-01), Svensson et al.
patent: 4300990 (1981-11-01), Maurer
patent: 4313338 (1982-02-01), Abe et al.
patent: 4878015 (1989-10-01), Schmidt et al.
patent: 4928513 (1990-05-01), Sugihara et al.
patent: 4931851 (1990-06-01), Sibbald et al.
patent: 4944273 (1990-07-01), Baresel et al.
patent: 5017340 (1991-05-01), Pribat et al.
patent: 5345213 (1994-09-01), Semancik et al.
patent: 5362975 (1994-11-01), von Windheim et al.
patent: 5430428 (1995-07-01), Gerblinger et al.
patent: 5656827 (1997-08-01), Kang et al.
patent: 5698771 (1997-12-01), Shields et al.
patent: 5777207 (1998-07-01), Yun et al.
patent: 5902556 (1999-05-01), Van De Vyver et al.
patent: 5948965 (1999-09-01), Upchurch et al.
patent: 6111280 (2000-08-01), Gardner et al.
patent: 6114943 (2000-09-01), Lauf
patent: 6190039 (2001-02-01), Yaguchi
patent: 4008150 (1991-09-01), None
patent: 63128246 (1988-05-01), None
Gebremariam Samuel Admassu
Rimai Lajos
Samman Amer Mohammad Khaled
Cygan Michael
Ford Global Technologies Inc.
Stec Jennifer
Williams Hezron
LandOfFree
Combined combustible gas sensor and temperature detector does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Combined combustible gas sensor and temperature detector, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Combined combustible gas sensor and temperature detector will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2903241