Design Method of Angle Sensing Chip Based on Anisotropic Magnetoresistive Effect

Abstract

The present invention discloses a design method for an angle sensing chip based on the anisotropic magnetoresistive effect. The angle sensing chip can realize double-angle sine and cosine waveform signals with a phase difference of 45°, and the sensing range is 0 to 180°. It can ensure uniqueness at a certain angle. Moreover, the concentric design of the double-bridge arrangement not only reduces the sensing error, improves the sensing accuracy, and realizes precise measurement of the angle, but also effectively reduces the overall size of the chip, achieves the purpose of miniaturizing the device, and greatly reduces the production cost of the product.

Description

Technical Field

[0001] The present invention relates to the technical field of angle sensing chips, mainly used for measuring the rotation angle of an object to be measured, and can be applied to fields such as robots, industrial automation control, aerospace, etc. Specifically, it is a design method of an angle sensing chip based on the anisotropic magnetoresistive effect. Background Art

[0002] An angle sensing chip is a type of signal sensing device used to measure the included angle between an object to be measured and a reference object. According to different principles, it is mainly divided into an optoelectronic angle sensor and a magnetic angle sensor. Due to the limitation of processing accuracy, the accuracy of optoelectronic angle sensors is not high. Currently, high-end angle sensors on the market all belong to magnetic angle encoders based on magnetic signal detection. According to different magnetic induction principles, there are mainly: TMR type, AMR type, GMR type. The main difference lies in the different graphic shapes and structures of angle sensing chips from different manufacturers. Summary of the Invention

[0003] The purpose of the present invention is to provide a design method of an angle sensing chip based on the anisotropic magnetoresistive effect. The angle sensing chip can realize double-angle sine and cosine waveform signals with a phase difference of 45°, and the sensing range is 0 to 180°. It can ensure uniqueness at a certain angle. Moreover, the concentric design of the double-bridge arrangement not only can reduce the sensing error, improve the sensing accuracy, and achieve precise measurement of the angle, but also effectively reduces the overall size of the chip, realizes the miniaturization of the device, and greatly reduces the production cost of the product, so as to overcome the deficiencies of the prior art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A design method of an angle sensing chip based on the anisotropic magnetoresistive effect, which includes the overall design part of the chip layout and the arrangement structure of the Wheatstone bridge.

[0005] The layout of the AMR angle sensing chip includes two Wheatstone bridges, namely bridge A and bridge B. Bridge A and bridge B are arranged concentrically. Both bridges are connected to PADs with an external circuit. When the external magnetic field H is in the x direction, it is defined as the 0° direction. Among them, the two-by-two resistors in bridge A are parallel to the x and y directions in turn, and the adjacent resistors in bridge A form a 90° angle. The four groups of resistors in bridge B form a 45° angle with both the x and y directions, and the adjacent resistors in bridge B form a 90° angle.

[0006] The arrangement structure of the Wheatstone bridge; the resistors at a 90° angle in Bridge A are connected. The four resistor units in Bridge A are arranged according to the center position of the layout and are in the shape of a four-cornered windmill. Among them, the connection points of the two resistors in Bridge A are connected to the PADs. The four resistor units of Bridge B are arranged in the four regions at the four corners of the square of the AMR angle sensor chip layout according to the remaining positions after the arrangement of the four resistor units of Bridge A. The adjacent resistor parts in Bridge B are connected and connected to the PADs. The centers of the magnetoresistive patterns of Bridge A and Bridge B are located at the same position, that is, the center of the layout. This concentric arrangement not only greatly reduces the overall size of the chip and achieves the purpose of device miniaturization, but also can effectively reduce the measurement error of the chip and improve the measurement accuracy of the angle sensor chip.

[0007] As a further solution of the present invention: the layout of the AMR angle sensor chip is designed as a square with a side length between 700 and 1000 um; the distance between the bridge part and the layout boundary is 4 um to 10 um.

[0008] As a further solution of the present invention: the PAD material is an Al electrode, and the number is 6, namely PAD1, PAD2, PAD3, PAD4, PAD5 and PAD6; among them, PAD1 and PAD5, PAD2 and PAD6, PAD3 and PAD4 are mirror-symmetrical in pairs according to the center of the layout. Among them, PAD1 and PAD5 are the common PADs of Bridge A and Bridge B, PAD5 is the input end VCC of the double bridge, PAD1 is the grounding end GND of the double bridge, PAD2 and PAD6 are the positive voltage output end (VOUTB+) and the negative voltage output end (VOUTB-) of Bridge B in sequence; PAD3 and PAD4 are the positive voltage output end (VOUTA+) and the negative voltage output end (VOUTA-) of Bridge A in sequence.

[0009] As a further solution of the present invention: the aspect ratio of the length to the width of the magnetoresistive layer of each magnetoresistive unit in the bridge is a magnetoresistive strip with a ratio of 100-200, and the magnetoresistive strips of each unit are neatly arranged. The magnetoresistive strips at the head and tail of each resistor unit are connected to form a snake shape; the width w of the magnetoresistive strip is designed to be maintained at 5 um to 20 um according to actual requirements, the thickness t of the magnetoresistive strip thin film is 15 nm to 50 nm, and the distance d between the magnetoresistive strips is 2 um to 5 um.

[0010] As a further solution of the present invention: The overall chip structure is divided into 5 layers; among them, the substrate uses single-crystal Si in the standard CMOS process; an isolation layer is provided on the substrate, and the isolation layer is composed of SiO2 formed by a thermal oxidation process with a thickness of 250nm - 500nm; the via metal is made of Al material with a thickness of 1um - 2um. After the lithography process, electrodes Al are grown on the Sensor layer by etching SiN, so that the Sensor layer is electrically connected and can be connected to the PAD part; the Sensor layer is made of permalloy material with a thickness of 20nm - 50nm.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention can output double-angle sine and cosine waveform signals with a phase difference of 45°, that is, ensure the uniqueness of the sensed angle and achieve precise measurement of the angle. Through the concentric arrangement design and scientific layout of the double Wheatstone bridge, the structure is simplified. While the chip parameters meet the requirements, the overall area and processing technological process of the chip are reduced as much as possible, thereby effectively reducing the production and manufacturing costs and improving the product quality. Description of the Drawings

[0012] Figure 1 It is the output characteristic diagram of the AMR angle sensing chip in the present invention;

[0013] Figure 2 It is the layout schematic diagram of the AMR angle sensing chip in the present invention;

[0014] Figure 3 It is the structure schematic diagram of the AMR angle sensing chip in the present invention. Detailed Embodiments

[0015] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0016] Please refer to Figures 1-3 , the present invention provides a technical solution: A design solution of an angle sensing chip based on the anisotropic magnetoresistive effect (AMR), which includes the overall design part of the angle sensing chip layout, the arrangement of the Wheatstone bridge, the shape and size design of each resistor of the Wheatstone bridge, and the structure of the angle sensing chip.

[0017] According to the output characteristics of the thin film, when the external magnetic field H is in the x direction, it is defined as the 0° direction. Then, the bridge A outputs a double-angle cosine signal y A = k1cos(2θ), and the bridge B outputs a double-angle sine signal y B= k2sin(2θ), where for a specific chip, k1 and k2 are known constants. As Figure 1 shown, for a specific angle, the outputs of the two bridges are unique, and the actual measured angle can be calculated from the outputs of the two bridges.

[0018] The layout of the AMR angle sensing chip includes: bridge A, bridge B, with bridge A and bridge B arranged concentrically, and 6 PADs for connecting the bridges to the external circuit. As Figure 2 shown, the four groups of resistors of bridge A are respectively parallel to the x and y directions, forming a 90° angle with each other, and the four groups of resistors of bridge B form a 45° angle with both the x and y directions, forming a 90° angle with each other.

[0019] The thin film part of the AMR angle sensing chip mainly includes magnetoresistive lines and electrodes. According to different line resistance requirements, the overall size of the layout can be designed as a square with a side length between (700 - 1000) um. The distance between the bridge part and the layout boundary is 4 um - 10 um. Each resistor part of bridge A with a 90° angle is connected, and its four resistor units are arranged in a four-corner windmill shape according to the center position of the layout and connected to the PADs. The four resistor units of bridge B are arranged in the four regions at the four corners of the square according to the remaining positions after the arrangement of the four resistor units of bridge A. Each resistor part within bridge B is connected and connected to the PADs. The centers of the magnetoresistive patterns of bridge A and bridge B are located at the same position, that is, the center of the layout. This concentric arrangement not only greatly reduces the overall size of the chip and achieves the goal of device miniaturization; but also can effectively reduce the measurement error of the chip and improve the measurement accuracy of the angle sensor chip. The 6 square structures are PADs for connecting the bridges to the external circuit, made of Al electrodes, with a size of 80 um * 80 um. The designed size of the PADs is mainly for convenient wire bonding during packaging, and the actual size can be appropriately increased or decreased according to the packaging process. PAD1 and PAD5, PAD2 and PAD6, PAD3 and PAD4 are mirror-symmetrical in pairs according to the center of the layout. Among them, PAD1 and PAD5 are the common PADs of bridge A and bridge B, PAD5 is the input terminal (VCC) of the double bridge, PAD1 is the ground terminal (GND) of the double bridge, PAD2 and PAD6 are respectively the positive voltage output terminal (VOUTB+) and negative voltage output terminal (VOUTB-) of bridge B; PAD3 and PAD4 are respectively the positive voltage output terminal (VOUTA+) and negative voltage output terminal (VOUTA-) of bridge A.

[0020] According to the AMR principle of the NiFe thin film and the characteristic that the magnetic moment of the thin film is arranged along the long side direction, we design the magnetoresistive layer as magnetoresistive strips with an aspect ratio of 100 - 200, and the magnetoresistive strips of each unit are neatly arranged. The magnetoresistive strips of each resistor unit are connected end to end to form a snake shape. The width w of the magnetoresistive strip is designed to be maintained at 5 um - 20 um according to actual requirements, the thickness t of the magnetoresistive strip thin film is 15 nm - 50 nm, and the spacing d between the magnetoresistive strips is 2 um - 5 um. The structure of the AMR angle sensor has a total of 5 layers, as Figure 3 shown. Among them, the substrate uses single-crystal Si in the standard CMOS process; the isolation layer is composed of SiO2 with a thickness of 250 nm - 500 nm by thermal oxidation process; the via metal is made of Al material with a thickness of 1 um - 2 um. After photolithography, electrodes Al are grown on the Sensor layer by etching SiN, so that the Sensor layer is electrically connected and can be connected to the PAD part; the Sensor layer is made of permalloy material with a thickness of 20 nm - 50 nm.

[0021] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0022] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A design method for an angle sensing chip based on the anisotropic magnetoresistive effect, characterized in that: The method includes the overall design part of the chip layout and the arrangement structure of the Wheatstone bridge; The layout of the AMR angle sensing chip includes two Wheatstone bridges, namely bridge A and bridge B; bridge A and bridge B are concentrically arranged, and PADs are connected to both of the two bridges and the external circuit; when the external magnetic field H is in the x direction, it is defined as the 0° direction. Among them, the two-by-two resistors in bridge A are parallel to the x and y directions in sequence, and the adjacent resistors in bridge A form a 90° angle; the four groups of resistors in bridge B form a 45° angle with both the x and y directions, and the adjacent resistors in bridge B form a 90° angle; The arrangement structure of the Wheatstone bridge: The resistors forming a 90° angle in bridge A are connected. The four resistor units in bridge A are arranged according to the center position of the layout and are in the shape of a four-corner windmill; among them, the connection of the two resistors in bridge A is connected to the PAD. The four resistor units of bridge B are arranged in the four regions at the four corners of the square of the AMR angle sensing chip layout according to the remaining positions after the arrangement of the four resistor units of bridge A. The adjacent resistor parts in bridge B are connected and connected to the PAD; the centers of the magnetoresistive patterns of bridge A and bridge B are located at the same position, that is, the center of the layout; this concentric arrangement not only greatly reduces the overall size of the chip and realizes the purpose of device miniaturization, but also can effectively reduce the measurement error of the chip and improve the measurement accuracy of the angle sensor chip; The material of the PAD is an Al electrode, and the number is 6, namely PAD1, PAD2, PAD3, PAD4, PAD5, and PAD6; among them, PAD1 and PAD5, PAD2 and PAD6, PAD3 and PAD4 are mirror-symmetrical in pairs according to the center of the layout; among them, PAD1 and PAD5 are the common PADs of bridge A and bridge B, PAD5 is the input end VCC of the double bridge, PAD1 is the grounding end GND of the double bridge, PAD2 and PAD6 are the positive voltage output end VOUTB+ and the negative voltage output end VOUTB- of bridge B in sequence; PAD3 and PAD4 are the positive voltage output end VOUTA+ and the negative voltage output end VOUTA- of bridge A in sequence; The aspect ratio of the length to the width of the magnetoresistive layer of each magnetoresistive unit in the bridge is a magnetoresistive strip of 100-200, and the magnetoresistive strips of each unit are neatly arranged. The magnetoresistive strips at the head and tail of each resistor unit are connected to form a snake shape; the width w of the magnetoresistive strip is designed to be maintained at 5um-20um according to actual requirements, the thickness t of the magnetoresistive strip film is 15nm-50nm, and the spacing d between the magnetoresistive strips is 2um-5um.

2. The design method of an angle sensing chip based on the anisotropic magnetoresistive effect according to claim 1, characterized in that: The layout of the AMR angle sensing chip is designed as a square with a side length between 700 and 1000um; the distance between the bridge part and the layout boundary is 4um-10um.

3. The design method of an angle sensing chip based on the anisotropic magnetoresistive effect according to claim 1, characterized in that: The overall chip structure has five layers; among which, the substrate uses single-crystalline Si in the standard CMOS process; an isolation layer is provided on the substrate, and the isolation layer is composed of SiO2 formed by a thermal oxidation process with a thickness of 250 nm - 500 nm; the via metal is made of Al material with a thickness of 1 μm - 2 μm. After the lithography process, electrodes Al are grown on the Sensor layer by etching SiN, enabling the Sensor layer to be electrically connected and to be connected to the PAD part; the Sensor layer is made of permalloy material with a thickness of 20 nm - 50 nm.

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