Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Temperature
Patent
1996-01-05
1998-10-13
Meier, Stephen
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Temperature
257 77, H01L 31058, H01L 310312
Patent
active
058215999
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to temperature sensors, in particular temperature sensors that can be used over a broad range of high temperatures. The electronic properties of semiconductor components, such as the density and mobility of the charge carriers, are generally temperature-dependent. If the intention is to use a component in a broad temperature range, it may be necessary to compensate for the influences of temperature using measurement technology. In order to compensate for temperature, the temperature at the component must be measured by a temperature sensor. This temperature sensor should be disposed as closely as possible to the component and preferably be integrated together with the component on a semiconductor chip. This would keep the thermal contact resistances between the component and the temperature sensor as low as possible.
Known temperature sensors are temperature-dependent resistors (thermistors) and thermal elements. With the aid of thin film technology, both sensor types can be integrated as thin metal films on a semiconductor component. One problem encountered is measuring temperatures in high-temperature and power electronics due to the high temperatures associated with the environments in which they are used. Another common problem is high temperature resulting from thermal power dissipation. For example, at temperatures of about 400.degree. C., the use of known sensor films is restricted because of metallurgical changes in the films. Changes in resistance occur in thermistor films because of granular growth processes, and changes in the contact material occur in the thermal element films because of diffusion processes.
A semiconductor material suitable for high-temperature applications up to at least 800.degree. C. and for high power output is silicon carbide (SiC). SiC is distinguished by a low intrinsic charge carrier density, a high breakdown field strength, a high thermal conductivity, and good thermal and chemical properties. A few components using SiC have already been developed, including a JFET (Junction Field Effect Transistor), MESFET (MEtal Oxide Semiconductor Field Effect Transistor) and a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Certain electronic properties of the SiC components depend on temperature because temperature affects charge carrier densities and mobilities in the component ("Diamond and Related Materials", vol. I (1992), pp. 109-120, Elsevier Science Publishers, Amsterdam).
An object of the present invention is to provide a temperature sensor that can measure temperatures of at least 400.degree. C. A further object is to monolithically integrate the sensor with a semiconductor component on a substrate. This allows the effect of temperature variations on the component to be controlled and compensated for.
SUMMARY OF THE INVENTION
These objectives are achieved in accordance with the present invention, which provides a temperature sensor having a junction of two oppositely doped semiconductor regions, each with a band gap greater than 2 eV. The two regions meet to form a p-n junction. A source electrode and a drain electrode are connected through the first region. A certain source-drain voltage is applied, and the current signal between these two electrodes is measured. Alternatively, a certain source-drain current is applied, and the voltage signal between these electrodes is measured. The magnitude of the current or voltage signal is related to the size of the space charge region of the p-n junction, which is related to the temperature. Hence, by measuring the current or voltage signal, the temperature may be measured over a range of at least 400.degree. C.
Silicon Carbide is a material that has the proper physical and electrical properties for use as the semiconductor material for the sensor.
The sensor may advantageously be provided with a gate electrode to adjust the measuring sensitivity. Applying a voltage to the gate electrode changes the size of the space charge region, thus adjusting the sensitivity an
REFERENCES:
patent: 5154514 (1992-10-01), Gambino et al.
patent: 5252840 (1993-10-01), Shiomi et al.
patent: 5264713 (1993-11-01), Palmour
Patent Abstracts of Japan, vol. 10, No. 145, 28 May 1986 & JP-A-61 006881 (Touhoku Kinzoku Kogyo K.K.), 13 Jan. 1986.
Patent Abstracts of Japan, vol. 7, No. 64, 17 Mar. 1983 & JP-A-57 207834 (Shinnihon Musen K.K.), 20 Dec. 1982.
Patent Abstracts of Japan, vol. 12, No. 228, 28 Jun. 1988 & JP-A-63 019869 (Fujitsu LTD.), 27 Jan. 1988.
Diamond and Related Materials, vol. 1 (1992), pp. 109-120, Elsevier Science Publishers, Amsterdam, NL; Robert F. Davis et al.: Epitaxial thin film growth, characterization and device development in monocrystalline .alpha.-and .beta.-silicon carbide.
Meier Stephen
Siemens Aktiengesellschaft
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