Electrical resistors – Resistance value responsive to a condition – Magnetic field or compass
Reexamination Certificate
2000-03-29
2001-03-13
Easthom, Karl D. (Department: 2832)
Electrical resistors
Resistance value responsive to a condition
Magnetic field or compass
C360S112000
Reexamination Certificate
active
06201466
ABSTRACT:
BACKGROUND OF THE INVENTION
The use of magnetoresistors (MRs) and Hall devices as position sensors is well known in the art. For example, a magnetically biased differential MR sensor may be used to sense angular position of a rotating toothed wheel, as for example exemplified by U.S. Pat. Nos. 4,835,467, 5,731,702, and 5,754,042.
Single element magnetic field sensors composed of, for example, an indium antimonide or indium arsenide epitaxial film strip supported on, for example, a monocrystalline elemental semiconductor substrate, are also known. The indium antimonide or indium arsenide film is, for example, either directly on the elemental semiconductor substrate or on an intermediate film that has a higher resistivity than that of silicon. A conductive contact is located at either end of the epitaxial film, and a plurality of metallic (gold) shorting bars are on, and regularly spaced along, the epitaxial film. Examples thereof are exemplified by U.S. Pat. Nos. 5,153,557, 5,184,106 and 5,491,461.
Many kinds of measurements cannot be performed with common magnetic sensors comprising a single or dual sensing element. The most common magnetic sensing element, the Hall sensor, does not quite fit the requirements for an array. Being a 4-terminal device complicates immensely the array connections. Furthermore, its low output signal would mandate the use of an integrated amplifier for each sensing element increasing the die size and its cost. However, compound semiconductor MRs, such as those manufactured from InSb, InAs, etc are simply two-terminal resistors with a high magnetic sensitivity and thus, are very suitable for the construction of single die MR arrays (in most cases one terminal of all the MR elements can be common).
Ultimately, such MR arrays could be integrated on the same die with appropriate processing circuitry. For example, if the MR array was fabricated on a Si substrate then the processing circuitry would be also Si based. For higher operating temperatures, silicon-on-insulator (SOI) could be used. A potentially lower cost alternative to the SOI approach would be to take advantage of the fact that MRs are currently fabricated on GaAs, a high temperature semiconductor, and thus, to fabricate the integrated processing circuitry from GaAs (or related InP) using HBT (Heterojunction Bipolar Transistor) or HEMT (High Electron Mobility Transistor) structures. This technology is now easily available and inexpensive through the explosive growth of the cellular phone industry.
Accordingly, what remains needed is a compact and inexpensive die having at lest one array of magnetic sensing elements and configured so as to produce a variety of array geometries suitable for specialized sensing schemes wherein an array is defined as having three or more rows of MR elements.
SUMMARY OF THE INVENTION
The present invention is a compact and inexpensive single die having at least one MR array, wherein each MR element is composed of a number of serially connected MR segments. The MR elements are arranged and configured so as to produce a variety of MR array geometries suitable for specialized sensing schemes, wherein an MR array is defined as having three or more MR elements.
According to a first aspect of the present invention, an MR array is formed of a plurality of uniformly arranged rows of MR elements, wherein each MR element is composed of a plurality of uniformly arranged, serially connected MR segments. The uniform arrangement is such as to provide a uniform MR array.
Accordingly to a second aspect of the present invention, an MR array is formed of a plurality of selectively arranged rows of MR elements, wherein each MR element is composed of a plurality of selectively varying, serially connected MR segments. The selective arrangement and/or selective variation is such as to provide a nonuniform MR array.
According to a preferred method of fabrication, an indium antimonide epitaxial film is formed, then masked and etched to thereby provide epitaxial mesas characterizing the MR elements. Shorting bars, preferably of gold, are thereupon deposited, wherein the epitaxial mesa not covered by the shorting bars provides the MR segments. The techniques for fabricating epitaxial mesas with shorting bars are elaborated in U.S. Pat. No. 5,153,557, issued Oct. 6, 1992, U.S. Pat. No. 5,184,106, issued Feb. 2, 1993 and U.S. Pat. No. 5,491,461, issued Feb. 13, 1996, each of which being hereby incorporated herein by reference.
Accordingly, it is an object of the present invention to provide an MR die comprising at least one MR array according to the first and second aspects of the present invention which is capable of detecting two-dimensional movement of a magnetic target in relation to the MR array, wherein MR arrays according to the second aspect of the present invention are capable of high resolution detection of movement along an axis generally parallel to the MR elements, as well as along the axis orthogonal thereto.
This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.
REFERENCES:
patent: 3335384 (1967-08-01), Weiss
patent: 4142218 (1979-02-01), Gorter
patent: 4503394 (1985-03-01), Kawakami et al.
patent: 4835467 (1989-05-01), Gokhale
patent: 5049809 (1991-09-01), Wakatsuki et al.
patent: 5153557 (1992-10-01), Partin et al.
patent: 5184106 (1993-02-01), Partin et al.
patent: 5247278 (1993-09-01), Pant et al.
patent: 5351028 (1994-09-01), Krahn
patent: 5491461 (1996-02-01), Partin et al.
patent: 5602471 (1997-02-01), Muth et al.
patent: 5719494 (1998-02-01), Dettmann et al.
patent: 5731702 (1998-03-01), Schroeder et al.
patent: 5754042 (1998-05-01), Schroeder et al.
patent: 5909115 (1999-06-01), Kano et al.
patent: 6011390 (2000-01-01), Loreit et al.
patent: 6100682 (2000-08-01), Schroeder
patent: 61-290784 (1986-12-01), None
Delphi Technologies Inc.
Dobrowitsky Margaret A.
Easthom Karl D.
LandOfFree
Magnetoresistor array does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetoresistor array, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetoresistor array will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2501039