Sensor and method for manufacturing a sensor

Details Sensor and method for manufacturing a sensor Sensor and method for manufacturing a sensor

1997-01-21

2001-07-10

Easthom, Karl D. (Department: 2832)

Electrical resistors

Resistance value responsive to a condition

Ambient temperature

C338S308000, C338S009000

Reexamination Certificate

active

06259350

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a sensor and a method for manufacturing a sensor.
BACKGROUND INFORMATION
A sensor having a microbridge, on which is arranged a heating element of platinum, is described in European Patent Application No. 0 375 399. Sensors of this type are preferably used as mass flow sensors. To ensure adequate adhesion of the platinum layer, out of which the heating element is patterned to the dielectric substrate, metal oxides are used for the adhesion-promoting layer between Pt and Si
3
N
4
.
SUMMARY OF THE INVENTION
One of the advantages of the sensor and the method for manufacturing a sensor according to the present invention is that an improved adhesion of the platinum layer to the dielectric substrate is achieved, which remains constant during long-term exposures to temperatures elevated (approximately greater than 250°) over ambient temperature and to high levels of atmospheric humidity. In addition, the sensor according to the present invention can be produced using especially advantageous methods.
The adhesion layer of platinum silicide (PtSi2), molybdenum silicide (MoSi2), tungsten silicide (WSi2), tantalum silicide (TaSi2), titanium silicide (TiSi2) and/or cobalt silicide (CoSi2) being used has no effect on the properties of the platinum layer, in particular on the resistance as a function of temperature. In comparison to the complicated deposition of metal oxides, the adhesion layer of metal silicide can be simply produced.
A plurality of materials, which contain silicon (SiO
2
, Si
3
N
4
, SiO
x
N
y
, etc. in accordance with various coating methods), are suitable materials for the substrate, which can be formed as a closed membrane over an Si cavity. A thin metal silicide layer, which introduces only negligible, additional thermally produced stresses, can be successful as an adhesion layer between the substrate (membrane) and the platinum. Typical dimensions of the metal layer lie between 140 and 160 nm. As a rule, the metal silicide layer is substantially between 3 and 6 nm thick. To protect the heating element, a dielectric coating layer can be provided, with an adhesion layer of one of the metal silicides provided between the heating element and the coating layer.


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patent: 36 28 017 (1987-03-01), None
patent: 0 375 399 (1990-06-01), None

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