Measuring and testing – Specimen stress or strain – or testing by stress or strain... – Specified electrical sensor or system
Reexamination Certificate
2001-10-29
2004-12-21
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
Specified electrical sensor or system
C073S723000
Reexamination Certificate
active
06832523
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a micromechanical component having a substrate and a diaphragm positioned on the substrate, and to a corresponding manufacturing method.
BACKGROUND INFORMATION
Even though it may be applied to any number of micromechanical components and structures, particularly sensors and actuators, the present invention as well as the problem it is based on are explained with reference to a micromechanical dew point sensor which can be manufactured within the technology of silicon surface micromechanics.
Already published in PCT Publication No. 96/05506 is the principle of sensing the dew point by cooling a micromechanical sensor element by a Peltier element until moisture condenses on the surface. The temperature of the sensor element at which condensation begins is measured using a temperature sensor, thereby determining the dew point.
In particular, PCT Publication No. 96/05506 describes a device including a Peltier element, a temperature sensor, an interdigital capacitor and a microprocessor for evaluation. The beginning of dew formation can be determined by changing the capacitance of the interdigital capacitor.
A further possibility is to determine dew formation by an optical measurement (also see D. Heinze, “Semiconductor Technologies for Manufacturing Modern Moisture Sensors”, Sensor 91, Nuremberg 1991, Kongre&bgr;band (Convention Volume) IV, 112-121).
The manufacture of a Peltier element using—and p-doped semiconductors connected by a metal bridge has long been known (see, for example, M. von Ardenne et al., “Effekte der Physik und ihre Anwendungen” (The Effects of Physics and their Applications), Publishing House Harri Deutsch, Frankfurt on Main 1990, page 399).
U.S. Pat. No. 5,714,791 describes a Peltier element by way of—and p-doped semiconductor areas on a diaphragm, the diaphragm being thermally insulated by etching a cavity from the reverse side of the substrate.
The method of etching silicon porous (“anodizing”) is a part of the related art and is described in numerous publications. The method of producing a cavity under porous silicon has likewise been published (G. Lammel, P. Renaud, “Free-standing Mobile 3D Microstructures of Porous Silicon”, Proceedings of the 13th European Conference on Solid-State Transducers, Eurosensors XIII, The Hague, 1999, 535-536).
With regard to the known dew point sensors, the disadvantageous fact has become apparent that their manufacture is difficult and costly.
SUMMARY OF THE INVENTION
The micromechanical component according to the present invention and the corresponding manufacturing method, respectively, have the advantage that simple and cost-effective manufacture of a component is possible, having a thermally decoupled diaphragm area.
For example, by using porous silicon, a deep cavity having a diaphragm lying above it can be manufactured relatively simply. Furthermore, there is the possibility of making a defined region on a wafer porous up to a defined thickness, and, as an option, of oxidizing to a higher valency in order to create a stable framework having low thermal conductivity. When producing a dew point sensor using this method, the following further advantages are available:
low power consumption because of good thermal decoupling
integration of a sensor element, e.g. a Peltier element, on the chip
possible integration of a circuit on the sensor element
very small size
low response time because of the small mass that has to be retempered
The idea at the basis of the present invention is that, underneath the diaphragm, a region of porous material supporting the diaphragm and thermally insulating it is provided.
According to a preferred further development, the porous material is formed from the substrate material. This is particularly well possible in the case of a silicon substrate.
According to a further preferred development, a hollow space is formed underneath the region made of porous material.
As in still another preferred further development, the diaphragm layer is formed by oxidizing the substrate surface and the surface of the porous region. Thereby the deposition of an additional diaphragm layer can be dispensed with.
According to a further preferred development, the region made of porous material is completely oxidized. Such an oxidation is easily possible based on the porous structure, and raises the thermal insulating capability.
According a further preferred refinement, the component has a dew point sensor in turn including a thermocouple for measuring the temperature, provided above the region made of porous material; an interdigital capacitor provided above the region made of porous material; a Peltier element device having one or a plurality of Peltier elements for heating and cooling the diaphragm; and a dew point measuring device for measuring the dew point with the aid of the capacitance of the interdigital capacitor and the temperature measured by the thermocouple.
In another further preferred development the component has a heat radiation sensor, which further includes an absorption device, provided above the region made of porous material, for absorbing heat radiation; a Peltier element device having one or a plurality of Peltier elements for creating a thermoelectric voltage corresponding to a temperature difference between a diaphragm region next to the region made of porous material and a diaphragm region above the region made of porous material; and a temperature measuring device for measuring the temperature in the diaphragm region above the region made of porous material.
In still another preferred development the temperature measuring device measures the temperature based on the thermoelectric voltage.
And in yet another further preferred development, a control device is provided for controlling the temperature in the diaphragm region above the region made of porous material, using the Peltier element device, and the temperature measuring device measures the temperature based on the regulated output.
REFERENCES:
patent: 5714791 (1998-02-01), Chi et al.
patent: 5852245 (1998-12-01), Wesling et al.
patent: 6076404 (2000-06-01), Muchow et al.
patent: WO 96 05506 (1996-02-01), None
patent: WO 03 012420 (2001-07-01), None
D. Heinze,Semiconductor Technologies for Manfuctring Modern Moisture Sensors,Sensor 91. Nuremberg 1991, Kongre&bgr;band (Convention Volume) IV, 112-121).
Lammel et al.,Free-standing Mobile 3D Microstructures of Porous Silicon, Proceedings of the 13th European Conference on Solid-State Transducers, Eurosensors XIII, The Hague, 1999, 535-536.
Benzel Hubert
Schaefer Frank
Weber Heribert
Allen Andre
Kenyon & Kenyon
Lefkowitz Edward
Robert & Bosch GmbH
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