Fishing – trapping – and vermin destroying
Patent
1989-04-10
1993-03-16
Chaudhuri, Olik
Fishing, trapping, and vermin destroying
437195, 437209, 437229, 257415, H01L 2144, H01L 2160
Patent
active
051944022
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method of producing microsensors with integrated signal processing wherein the electronic circuits for the signal processing and the sensor structures coupled therewith are produced on a common substrate immediately adjacent one another in space.
It is known to produce microsensors of this type by combining methods of semiconductor technology and the anisotropic silicon etching technology so as to produce on a silicon wafer in one process sequence the electronic circuits and the sensor structures coupled therewith. Such a manner of proceeding for the production of a capacitive acceleration sensor is described and illustrated by K. E. Petersen, A. Shartel and N. F. Raley, in "Micromechanical Accelerometer Integrated with MOS Detection Circuitry," IEEE Transactions on Electron Devices, Vol. ED-29, No. 1, January, 1982, pages 23 to 27. According to FIG. 1 of that publication, a structured p-doped layer is initially produced in the surface of an Si wafer as the electrode and etch stop layer. Then silicon is precipitated epitaxially to a thickness corresponding to the spacing of the electrodes and a structured silicon oxide layer is produced. By means of anisotropic etching, a contact hole is made through the opening in the silicon oxide layer, through the epitaxial silicon layer, down to the buried electrode. The source and drain regions and the electrical connection in the contact hole are produced by doping. Then the gate oxide is produced and an etching window is opened in the silicon oxide layer for the later formation of the sensor structure in the form of a reed. Then, the electrical connections are made and the reed region is metallized. As the last step, anisotropic silicon etching forms a trough between the buried electrode and the silicon oxide, thus creating a metallized silicon oxide reed which is able to vibrate.
The drawback of this processing sequence is that standard semiconductor processes such as, for example, oxidizing and doping, are employed in alternating succession with anisotropic silicon etching processes. This leads to problems in mass production since the use of alkali etching agents in the anisotropic etching process involves the danger of undesirable changes in the characteristics of the electronic circuits.
SUMMARY OF THE INVENTION
It is an object of the invention to make available a method of producing microsensors of this type in which the manufacturing steps for the sensor structures have no negative effect on the electronic circuits coupled therewith.
The above object is generally achieved according to the present invention by a method which includes the steps of: known in the semiconductor art; applying a galvanic electrode on the substrate; applying a layer of an X-ray resist material on the substrate which has been provided with the galvanic electrode, with the thickness of the layer corresponding to a characteristic height of the sensor structures; producing negatives of the sensor structures in the layer by means of X-ray lithography; electrochemically depositing a metal or a metal alloy in the negatives of the sensors structures with the use of the galvanic electrode; and separating the substrate including the sensor structures applied thereto into individual functional units or chips.
The production of microstructures by X-ray lithographic means (LIGA method) is described and illustrated in Bericht KfK (Report KfK) 3995, November, 1985, published by Kernforschungszentrum Karlsruhe, to which reference is made.
The method according to the invention has the advantage that the production of the sensor structures is independent of the production of the electronic circuits and does not influence the latter.
Embodiments of the invention will be described below with reference to the drawing FIGS.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1a to FIG. 1e are schematic sectional views which depict various steps in the production of an inductive distance sensor according to the inventive method.
FIG. 2 is a schematic plan o
REFERENCES:
patent: 3993515 (1976-11-01), Reichert
patent: 4078963 (1978-03-01), Symersky
patent: 4943539 (1990-07-01), Wilson et al.
IEEE Transactions on Electronic Devices, vol. ED-29, No. 1, Jan. 82, IEEE (NY), Peterson et al., pp. 23-27.
Technische Rundschau, vol. 79, No. 13, 27 Mar. 1987, pp. 54-57.
Technische Rundschau, vol. 78, No. 35, Aug. 1986, pp. 32-37.
Ehrfeld Wolfgang
Gotz Friedrich
Schelb Werner
Schmidt Dirk
Chaudhuri Olik
Kernforschungszentrum Karlsruhe GmbH
Trinh Loc Q.
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