MTJ based magnetic field sensor with ESD shunt trace
First Claim
1. An MTJ sensor for magnetic field and current measurements comprising:
- A first plurality of MTJ structures, each structure containing a second plurality of patterned MTJ cells formed between top and bottom electrodes and connected electrically in parallel thereby, each of said MTJ cells having a resistance that varies in accord with the direction and strength of an external magnetic field applied thereto;
electrical connections to said electrodes of each of said MTJ structures whereby a sensing current may be injected and extracted from each of said first plurality of MTJ structures and whereby equal portions of said current passes through each of said second plurality of MTJ cells and whereby a measurable voltage is established across each of said second plurality of MTJ cells in accord with the resistances thereof;
a conducting shunt formed in two portions on each of said first plurality of MTJ structures, each one of said two portions electrically connecting each one of said electrical connections to an external ground connection, said shunt allowing harmless passage of accumulated electrostatic charges on said MTJ structure to ground during manufacture and handling of the sensor, said charges bypassing said MTJ cells in said MTJ structure and averting electrostatic damage thereto;
whereinsaid shunt is sufficiently resistive so that no more than approximately 5% of said sensing current passes through said shunt during operation of the sensor.
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Accused Products
Abstract
Presented herein is a shunted MTJ sensor formed of a plurality of electrically connected MTJ cells for measuring magnetic fields and currents and its method of fabrication. To provide stable single domain magnetic moments of the MTJ cells and to ensure that the magnetic moments return to a fixed bias point in the absence of external magnetic fields, the cells are formed of sufficiently small size and with elliptical cross-section of aspect ratio greater than 1.2. To eliminate the possibility of ESD damage to the cells, they are protected by a parallel shunt, formed as a trace of sufficiently high resistance that directs accumulated charges harmlessly to ground while bypassing the cells.
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Citations
21 Claims
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1. An MTJ sensor for magnetic field and current measurements comprising:
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A first plurality of MTJ structures, each structure containing a second plurality of patterned MTJ cells formed between top and bottom electrodes and connected electrically in parallel thereby, each of said MTJ cells having a resistance that varies in accord with the direction and strength of an external magnetic field applied thereto; electrical connections to said electrodes of each of said MTJ structures whereby a sensing current may be injected and extracted from each of said first plurality of MTJ structures and whereby equal portions of said current passes through each of said second plurality of MTJ cells and whereby a measurable voltage is established across each of said second plurality of MTJ cells in accord with the resistances thereof; a conducting shunt formed in two portions on each of said first plurality of MTJ structures, each one of said two portions electrically connecting each one of said electrical connections to an external ground connection, said shunt allowing harmless passage of accumulated electrostatic charges on said MTJ structure to ground during manufacture and handling of the sensor, said charges bypassing said MTJ cells in said MTJ structure and averting electrostatic damage thereto;
whereinsaid shunt is sufficiently resistive so that no more than approximately 5% of said sensing current passes through said shunt during operation of the sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of fabricating an MTJ sensor for measuring magnetic fields and electrical currents comprising:
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providing a conductor for carrying a current to be measured, wherein said current produces a measurable magnetic field; forming adjacent to said conductor a first plurality of MTJ structures, wherein each of said structures has two electrical contacts, one contact for injecting a sense current, the other contact for extracting said current, wherein each of said structures includes a second plurality of identical patterned MTJ cells having single domain magnetic moments, substantially elliptical horizontal cross-sections with aspect ratio greater than approximately 1.2 and with a long axis parallel to said conductor; forming a shunt around each said MTJ structure, said shunt being formed as two substantially identical traces of high resistance wherein each said trace connects one of said electrical contacts to a ground connection, said shunt thereby harmlessly directing accumulated electrostatic charges to said ground connection thereby avoiding electrostatic damage to said MTJ cells. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification