Fishing – trapping – and vermin destroying
Patent
1996-07-17
1997-12-23
Nguyen, Tuan H.
Fishing, trapping, and vermin destroying
437 3, 437 51, 437901, 437974, 148DIG159, H01L 21265
Patent
active
057007020
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is directed to a manufacturing method for acceleration sensors in silicon technology wherein micromechanical manufacturing method are applied.
Extremely small and, thus, cost-efficient micromechanical acceleration sensors for acceleration measurements in the region of earth's accelerations require electronic circuits for the interpretation of the measured result. Such intelligent sensors are usually manufactured in hybrid technology because a realization in the same substrate requires a practically additive manufacturing technology. The electronic circuit and the micromechanical sensor are successively manufactured, so that such integrated sensors usually require more than four auxiliary masks in the manufacture, this causing an added outlay of at least 20%.
SUMMARY OF THE INVENTION
An object of the present invention is to specify a beneficial manufacturing method for a micromechanical acceleration sensor with electronics.
In general terms the present invention is a method for manufacturing an acceleration sensor on silicon. In a first step, a structure of doped regions for the fashioning of a transistor is produced proceeding on the basis of a substrate layer of silicon. In a second step, a polysilicon layer is deposited and structured such that this polysilicon layer forms at least one electrode of this transistor and a sensor layer. In a third step, metallizations are applied as electrical terminals for this transistor, for this sensor layer and for at least one further sensor electrode. In a fourth step, this sensor layer is uncovered to such an extent that it is at least partially movable in at least one direction.
Advantageous developments of the present invention are as follows.
The transistor is manufactured as a CMOS transistor, and the polysilicon layer forms the gate electrode and the sensor layer.
The transistor is manufactured as a bipolar transistor. A further polysilicon layer is deposited and structured between the first and the second step such that this further polysilicon layer forms the base electrode and a lower sensor electrode. An insulator layer and spacers are then applied. The polysilicon layer applied in the second step forms the emitter electrode, the collector electrode and the sensor layer.
For CMOS transistor manufacture, in the first step, a doped region (CMOS well) provided for the transistor is produced in the substrate layer and a structured oxide layer is produced on the surface of the substrate layer. The source and drain regions and the gate oxide are then produced in openings of this oxide layer. In the second step, the sensor layer is produced on a portion of this oxide layer. In the third step, a dielectric layer is applied, via holes are produced therein, and the source and drain metallizations and the metallizations for the sensor layer and for a further sensor electrode are introduced into these via holes. In the fourth step, this dielectric layer and this oxide layer are removed to an extent required for the provided mobility of the sensor layer.
For bipolar transistor manufacture, in the first step, an implantation is undertaken for the manufacture of a collector region and a doped epitaxial layer is applied. A structured oxide layer is then produced. A base region doped opposite this epitaxial layer and a collector terminal region are produced through openings of this oxide layer. The further polysilicon layer and an insulator layer thereon are applied and structured, so that the lower sensor electrode is arranged on this oxide layer. The free edges of the base electrode are then insulated by spacers. The second step is then implemented.
The sensor layer is manufactured as a self-supporting polysilicon strip (cantilever) in the fourth step. The sensor layer is manufactured as a mass part suspended at springs in the fourth step. The further sensor electrode and the sensor layer are coplanarly arranged and are arranged vertically above one another with reference to the layer planes. Following the third step,
REFERENCES:
patent: 4918032 (1990-04-01), Jain et al.
patent: 5241864 (1993-09-01), Addie et al.
Thin Solid Films, vol. 220, No. 1/2, Nov. 20, 1992, Properties of Polysilicon Films Annealed by a Rapid Thermal Annealing Process, Ristic et al, pp. 106-110.
IEEE Transactions On Electron Devices, vol. 29, No. 1, Jan. 1992, Micromechanical Accelerometer Integrated with MOS Detection Circuitry, Petersen et al, pp. 23-27.
IEEE International Symposium on Circuits and Systems, vol. 4, No. 1, May 1990, Integrated GaAs Microsensors, Polla et al, pp. 3085-3088.
Biebl Markus
Hierold Christofer
Klose Helmut
Scheiter Thomas
Nguyen Tuan H.
Siemens Aktiengesellschaft
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