Magnetoresistive sensor element and method of assembling magnetic field sensor elements with on-wafer functional test

• US 7,323,870 B2
• Filed: 02/23/2006
• Issued: 01/29/2008
• Est. Priority Date: 02/23/2005
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Zimmer, Juergen, Tatschl, David, Hammerschmidt, Dirk
• Primary Examiner(s): Patidar; Jay M
• Application Number:
  US11/360,315
• Publication Number:
  US 20060202692A1
• Time in Patent Office: 705 Days
• Field of Search: 324/252, 324/207.21, 324/224, 324/263, 324/226, 324/225
• US Class Current: 324/252
• CPC Class Codes: G01L 25/00 Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency
• CPC Class Codes: G01L 25/003 for measuring torque
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: G01R 31/315 by inductive methods
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• CPC Class Codes: G01R 35/00 Testing or calibrating of apparatus covered by the other groups of this subclass

Abstract

A method of performing an on-wafer function testis provided for multiple magnetic field sensor elements on a wafer. Each sensor element includes a magnetic-field-sensitive structure and a current conductor structure. The current conductor structure provides a test magnetic field in response to a test signal, and a change in an electrical characteristic of the respective magnetic-field-sensitive structure is sensed. The functionality of the respective magnetic field sensor element is then evaluated based on electrical characteristic change.

Claims

1. A method of performing an on-wafer function test comprising:

providing a wafer with a plurality of magnetic field sensor elements arranged thereon, wherein each magnetic field sensor element comprises a magnetic-field sensitive structure and an associated current conductor structure, wherein the magnetic-field-sensitive structure has a magnetic-field-dependent electrical characteristic, and wherein each of the current conductor structures is formed to generate a predetermined test magnetic field component in the associated magnetic-field-sensitive structure;

testing each magnetic-field-sensitive structure of the magnetic field sensor elements by;

generating a test signal through each of the current conductor structures, to generate the predetermined test magnetic field component in the associated magnetic-field-sensitive structure;

sensing a change in the electrical characteristic of the magnetic-field-sensitive structure due to the test magnetic field component; and

evaluating the functionality of the magnetic field sensor element, based on the sensed change in the electrical characteristic of the magnetic-field-sensitive structure.

2. A method of claim 1, wherein the step of sensing a change comprises a sub-step of sensing an output signal of the magnetic-field-sensitive structure, wherein the output signal depends on the electrical characteristic of the magnetic-field-sensitive structure and the test signal.

3. A method of claim 2, wherein the step of evaluating further comprises a step of comparing the output signal dependent on the electrical characteristic and the test signal with a predetermined comparison value.

4. A method of claim 3, wherein reaching or exceeding the comparison value indicates a malfunction of the magnetic field sensor element, and under running the comparison value indicates a normal function of the magnetic field sensor element.

5. A method of claim 3, wherein reaching or under running the comparison value indicates a malfunction of the magnetic field sensor element, and exceeding the comparison value indicates a normal function of the magnetic field sensor element.

6. A method of claim 2, wherein the output signal further depends on an environment value, wherein the step of sensing the change further comprises a sub-step of determining the proportion of the output signal dependent on the electrical characteristic and the test signal.

7. A method of claim 6, wherein the step of determining the proportion of the output signal further comprises a sub-step of filtering out the signal portion due to the environment value.

8. A method of assembling magnetic field sensor elements with on-wafer function test, comprising the steps of:

providing a substrate;

arranging a plurality of permanently magnetizable magnetic field sensor structures on the substrate, wherein the permanently magnetizable magnetic field sensor structures have a magnetization minimum temperature;

arranging a plurality of current conductor structures on the substrate, so that a current conductor structure is associated with each permanently magnetizable magnetic field sensor structure;

generating local, permanent magnetization in each magnetic field sensor structure by;

heating the permanently magnetizable magnetic field sensor structure to a temperature value above the magnetization minimum temperature; and

generating a magnetization signal in the current conductor structure, to effect a defined magnetization magnetic field component in the permanently magnetizable sensor structure, so that permanent, local magnetization of the magnetic field sensor structure arises and the magnetic field sensor element with the permanently magnetized magnetic field sensor structure has a magnetic-field-dependent dependent electrical characteristic;

testing each magnetic-field-sensitive structure of the magnetic field sensor elements by;

generating a test signal through the current conductor structure, to generate a predetermined test magnetic field component in the magnetic-field-sensitive structure;

sensing a change in the electrical characteristic of the magnetic field sensor structure due to the test magnetic field component; and

evaluating the functionality of the magnetic field sensor element based on the sensed change in the electrical characteristic of the magnetic field sensor structure.

9. A method of claim 8, wherein the step of heating comprises a sub-step of generating a heating current signal through the current conductor structure.

10. A method of claim 9, wherein the sub-step of generating a heating current signal through the current conductor structure for heating the permanently magnetizable magnetic field sensor structure is performed so that the permanently magnetizable magnetic field sensor structure has a temperature value above the magnetization minimum temperature while generating the magnetization signal in the current conductor structure.

11. A magnetic field sensor element, comprising:

a permanently magnetizable magnetic field sensor structure with a first and a second sensor element contact, wherein the permanently magnetizable magnetic field sensor structure has permanent magnetization, and wherein a magnetic-field-dependent electrical characteristic of the magnetic field sensor structure is detectable via the sensor element contacts, and

a current conductor structure with a first and a second current conductor contact, wherein the current conductor structure is formed so that a magnetization signal is applicable between the first and the second contact, to obtain a defined magnetization magnetic field component in the magnetic field sensor structure, in order to effect permanent, local magnetization of the magnetic field sensor structure, and so that also a test signal is applicable between the current conductor contacts, to obtain a defined test magnetic field component in the magnetic field sensor structure, wherein the current conductor structure is further formed so that a heating signal is applied between the first and the second contact, to raise the permanently magnetizable magnetic field sensor structure to a temperature value above the magnetization minimum temperature.

12. A magnetic field sensor element of claim 11, wherein the current conductor structure is formed and arranged with reference to the permanently magnetizable magnetic field sensor structure so as to generate a substantially homogeneous magnetic field in the permanently magnetizable magnetic field sensor structure.

13. A magnetic field sensor element, comprising:

a permanently magnetizable magnetic field sensor structure with a first and a second sensor element contact, wherein the permanently magnetizable magnetic field sensor structure has permanent magnetization, and wherein a magnetic-field-dependent electrical characteristic of the magnetic field sensor structure is sensed via the sensor element contacts, and

a current conductor structure with a first and a second current conductor contact, wherein the current conductor structure is formed so that a magnetization signal is applied between the first and the second contact, to obtain a defined magnetization magnetic field component in the magnetic field sensor structure, in order to effect permanent, local magnetization of the magnetic field sensor structure, and so that also a test signal is applied between the current conductor contacts, to obtain a defined test magnetic field component in the magnetic field sensor structure.

wherein the permanently magnetizable magnetic field sensor structure has a width C2 and the associated current conductor structure has a width C1, wherein the width C2 of the magnetizable magnetic field sensor structure is smaller than or equal to the width Cl of the associated current conductor structure, and

wherein the permanently magnetizable magnetic field sensor structure and the associated current conductor structure are arranged at a distance C3 from each other,

wherein the distance C3 is smaller than about 20% and preferably smaller than 10% of the width C1 of the current conductor structure.

14. A magnetic field sensor element of claim 13, wherein the width C1 of the current conductor structure ranges from 2 to 25 μ

m.