Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Physical stress responsive
Reexamination Certificate
1998-03-11
2001-03-20
Nguyen, Nam (Department: 1753)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Physical stress responsive
C073S721000
Reexamination Certificate
active
06204086
ABSTRACT:
BACKGROUND INFORMATION
It is generally known to combine semiconductor components with micromechanical structures. The result is compact components, which are able to detect an acting physical quantity, such as a pressure, and simultaneously produce an electrical signal proportional to this physical quantity that is then fed to an evaluation circuit of the component. Components of this kind are manufactured, as is generally known, as monolithic components, the sensor part and the evaluation part being produced one after another in a wafer. The inherent drawback here is that because of the different fabrication techniques, significant interventions in each of the other fabrication steps have to be made.
Furthermore, it is known to manufacture the sensor part and the evaluation part separately and to subsequently join them to the component. The sensor part has the micromechanical structures and the semiconductor components for detecting an electrical signal that is proportional to the physical quantity. In the case of a pressure sensor, a membrane that deforms under applied pressure is produced in a silicon wafer. This deformation is taken up by piezoresistors (semiconductor components), which as a result undergo an analog change in resistance. This altered resistance is detected with a later applied evaluation circuit and used to obtain a pressure-proportional output signal.
It is known to fabricate the silicon membrane using an anisotropic etching process. The piezoresistors for detecting membrane deflection are then assigned to this silicon membrane through process steps in the semiconductor component production. The drawback here is that because of the separate processes, the distance between the piezoresistors and the membrane at maximum stress can only be realized with a relatively large deviation of about 50 &mgr;m.
SUMMARY OF THE INVENTION
The method of the present invention has the advantage that the piezoresistors are able to be placed with a much greater accuracy at the point of the membrane's maximum stress. This makes it possible to substantially reduce the size of the sensor part, so that given the same patterning on a wafer of the same size as those of the related art, the number of attainable components can be increased. Besides a higher yield, one derives the benefit here of reduced costs.
Due to the fact that the semiconductor components and the micromechanical structures are defined in a self-aligning manner by process steps acting on one side of the wafer to produce semiconductor components, both the micromechanical structure and the semiconductor components can be defined in the narrowest of spaces by simple process steps to be mastered with a high level of precision, since it is possible using the masking technique of semiconductor fabrication to achieve a very high accuracy, within the range of a few &mgr;m. The regions are defined relative to one another with self-alignment, producing by this means the mechanical structures and the semiconductor components.
The semiconductor components featuring the micromechanical structures are preferably able to be produced in successive process steps using a plurality of masking levels, the process steps being carried out from merely one side of the wafer. Besides the fact that this is easily feasible in terms of process engineering, a multiplicity of variants can be achieved with relatively little outlay for development. Moreover, it is advantageous that when the micromechanical structures are defined with the aid of the semiconductor component production method, the hollow space needed for membrane deflection is enclosed within the component. This simplifies the subsequent mounting of chips containing the evaluation circuit, since the connection between the evaluation circuit and the sensor element no longer needs to be designed compactly. Thus, for example, in the place of costly soldering, the chips containing the evaluation circuit can be bonded (adhesively applied) to the sensor element.
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Baumann Helmut
Muchow Joerg
Cantelmo Gregg
Kenyon & Kenyon
Nguyen Nam
Robert & Bosch GmbH
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