The present invention relates to an MTJ or GMR angle sensor element, particularly a angle sensor integrated into a single standard semiconductor package.
Magnetic sensors are widely used in modern systems to measure or detect physical parameters including but not limited to magnetic field strength, current, position, motion, orientation, and so forth. There are many different types of sensors in the prior art for measuring magnetic field and other parameters. However, they all suffer from various limitations well known in the art, for example, excessive size, inadequate sensitivity and/or dynamic range, cost, reliability and other factors. Thus, there continues to be a need for improved magnetic sensors, especially sensors that can be easily integrated with semiconductor devices and integrated circuits and manufacturing methods thereof.
Magnetic tunnel junction (MTJ) sensors have the advantages of high sensitivity, small size, low cost, and low power consumption. Although MTJ devices are compatible with standard semiconductor fabrication processes, methods for building high sensitivity devices with sufficient yield for low cost mass production have not been adequately developed. In particular, yield issues due to difficulty in MTJ process and backend packaging process, and difficulty in matching the magnetoresistive response of MTJ elements when combined to form bridge sensors have proven difficult.
the present invention is to provide a single-package magnetic angle sensor may be used to measure the value of the angle of the magnetic field in order to remedy the above-mentioned problems.
In order to solve the above technical problem, one aspect of the present invention adopts the technical scheme as follows: a single-package bridge magnetic angle sensor, the sensor comprises two half-bridge sensors, each half-bridge sensor includes a sensor chip, wherein the sensor chip is rotted by 90 degrees relative to another sensor, the sensor chips are attached to the leadframe of a standard semiconductor package, each sensor chip includes a fixed resistance as a reference resistor, and a sensing resistor that ahs a response which varies in proportion to an external magnetic field; each reference resistor and the sensing resistor comprises a plurality of MTJ or GMR sensor elements. The MTJ or GMR sensor elements are arranged in an array and interconnected in order to function as a single bridge arm, each of the reference resistor and the sensing resistor bridge arm further comprises a strip-shaped permanent magnets between the rows of MTJ or GMR elements in order to provide a magnetic bias field; bond pads are provided on the sensor chip which are large enough to permit a plurality of bonding wires to be attached to each side of the bridge arm; The sensor chips are interconnected to each other and the leadframe using wire bonding, and finally the sensor chips and leadframe are encapsulated in plastic to form a standard semiconductor package.
A second implementation of the present inventions is a single-package bridge-type magnetic field angle sensor, wherein the sensor includes two full-bridge sensors, called the first full-bridge sensor and the second full-bridge sensors respectively, each full-bridge sensor consists of two half-bridge sensors, and each half-bridge sensor comprises a single MTJ or GMR magneto-resistive sensor chip. The sensor include a fixed resistance of the reference resistor and a variable resistance sensor that provides an output proportional to the external magnetic field. The sensors are attached to a leadframe and encapsulated in a standard semiconductor package.
Each of the reference resistor and the sensing resistor includes a plurality of MTJ or GMR sensor elements, wherein the MTJ or GMR sensor elements are interconnected as a separate magnetoresistive element also known as a bridge arm. Within the bridge arm, the MTJ or GMR sensor elements are arranged in the form of an array. Each of the reference resistor and the sensing resistor including strip-shaped permanent magnets, to provide a bias field for the magneto-resistive elements. The permanent magnet bars are located between rows of magnetoresistive elements in the bridge arm arrays. Each sensor chip has large bond pads to permit one or more wire bonds to be attached to the same bond pad; The magneto-resistive sensor chips are electrically interconnected and connected to the leadframe using wire bonding, in order to constitute a bridge sensor; The leadframe and the sensor chip are encapsulate in plastic to form a standard semiconductor package.
Preferably, the magnetic angle sensor, characterized in that: the first and second full-bridge sensors comprise two sensor chips rotated by 180 degrees with respect to each other, and the two full-bridge sensor rotated by 90 degrees with respect to each other.
Preferably, the magnetoresistive sensing elements have an oval shape.
Preferably, the magnetoresistive elements of the reference resistor of claims 1 and 2 are patterned in different shape aspect ratio from the magnetoresistive elements of the sensing resistor.
Preferably, the reference resistor is screened from applied magnetic field by one or more magnetic shields.
Preferably, the magnetic angle sensor, characterized in that: said sensor chip is biased using a voltage or a current.
Preferably, the sensor chips are tested and sorted before assembly in order to better match their transfer curve characteristics.
The magnetic angle sensor may contain sensor chips that are set side-by-side for use in detecting magnetic field angle when there is only a small gradient.
The single-package magnetic rotation sensor may contain sensor chips that are arranged such that the chips have a common center in order to provide the capability to measure angle in the presence of a large magnetic field gradient.
FIG. 1—Schematic drawing of the magnetoresistive response of a spin-valve sensing element with the reference layer magnetization pointing in the negative H direction.
FIG. 2—Schematic drawing of a half-bridge with a fixed reference resistor and a sensing resistor.
FIG. 3—An embodiment of a half-bridge in a magnetoresistive sensor chip where both reference resistor and sensing resistor made of plural MTJ elements arranged in row arrays and bar-shape permanent magnets are used to bias the MTJ elements
FIG. 4—Schematic of a rotation sensor with two half-bridges.
FIG. 5—Schematic of output voltages as functions of rotation angle of the magnetic field relative to the magnetic rotation sensor.
FIG. 6—An embodiment of a rotation sensor comprising of two half-bridge magnetoresistive sensor chips. One is oriented 90° with respect to the other. The chips are placed within a standard semiconductor package
FIG. 7—Schematic of a rotation sensor with two full-bridges.
FIG. 8—An embodiment of a rotation sensor comprising of two full-bridges. Each of the full bridges is flip die comprising of two magnetoresistive sensor chips. The chips are placed within a standard semiconductor package
These sensor elements are configured as spin valves, where one of the magnetic layers has a magnetization with an orientation that is fixed in order to serve as a reference. This fixed layer can be a single magnetic layer or a synthetic ferromagnetic structure, which is pinning by a pinning layer. The other magnetic layer, so called free layer, in a spin valve can rotate in response to the applied magnetic field. The resistance of the spin valve varies with the free layer orientation with respect to the fixed (pinned) layer, and then with the magnetic field on the free layer. In a MTJ element, the free layer and fixed layer are separated by a barrier. Electrical current flows through the barrier. In a GMR element, the free layer and the pinned layer are separated by a non-magnetic metallic layer. Electrical current can flow either in the plane of the multilayer thin film or perpendicular to the plane.
The general form of the magnetoresistive transfer curve of a GMR or MTJ magnetic sensor element suitable for linear magnetic field measurement is shown schematically in
Between the saturation fields, 4 and 5, is the operation field region where ideally the response of the MTJ or GMR resistance is linear. Sensitivity of the MTJ element, the slope 3 of the transfer curve in
Depending on the design of the magnetic magnet that produces the rotating magnetic field, there will be a gradient in the magnetic field that can be divided into three different cases:
The reason for these classifications is if the sensor chips do not have a common center and they are spaced far apart the gradient of the magnetic field generated by the rotating magnet and could have significant errors; When the chips are spaced close together and laid out such that the sensor bridge has a well defined geometric center, a smaller error will result in the angle calculation.
Full-bridges can be used to make magnetic rotation sensors. Full bridge sensor can provide larger output voltage than half-bridge and, therefore, more sensitive to magnetic field.
An embodiment of the rotation sensor 60 built with full-bridges is shown in
The full-bridge angle sensor can be made as shown in
It will be apparent to those skilled in the art that various modifications can be made to the proposed invention without departing from the scope or spirit of the invention. Further, it is intended that the present invention cover modifications and variations of the present invention provided that such modifications and variations come within the scope of the appended claims and their equivalence.
Number | Date | Country | Kind |
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201110050747.4 | Mar 2011 | CN | national |
This application is a 35 U.S.C. §371 national phase application of PCT/CN2012/071879, filed on Mar. 2, 2012, which claims priority to a Chinese Patent Application No. CN201110050747.4, filed on Mar. 3, 2011, incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CN2012/071879 | 3/2/2012 | WO | 00 | 9/2/2013 |