Displacement sensing chip based on AMR effect

Abstract

The invention belongs to the field of electronic chips, and discloses a displacement sensing chip based on AMR effect, the displacement sensing chip sequentially comprises a silicon layer, a silicon oxide layer, a magnetic sensitive film layer, a silicon nitride layer and an aluminum layer, the structure of the magnetic sensitive film layer is sequentially divided into a first area, a second area, a third area and a fourth area through magnetic sensitive lines, the number of the magnetic sensitive lines in each area is the same, the size of each magnetic sensitive line is 8-20 [mu] m, and the size of each magnetic sensitive line is 8-20 [mu] m. The magneto-sensitive lines in the first and third areas are alternately connected to form a first Wheatstone bridge, the magneto-sensitive lines in the second and fourth areas are alternately connected to form a second Wheatstone bridge, two ends of the magneto-sensitive lines in each group of Wheatstone bridges are designed into acute angle structures, and the two ends of each group of magneto-sensitive lines etch silicon nitride on the surface layer to enable the silicon nitride to be directly conducted with an aluminum layer electrode. The magnetic sensing lines are connected with each other through the aluminum lines and are collected to a PAD, the temperature output by a chip can basically keep relative stability, and the measurement error of displacement is small through the centering structure design.

Description

Technical Field

[0001] The invention belongs to the field of electronic chips and is mainly used for measuring the displacement of an object to be measured, in particular to a displacement sensor chip based on the AMR effect. Background Art

[0002] There are many sensor chips based on the AMR effect on the market. On the one hand, the temperature of the chip is unstable during use, which has a great impact on its service life, especially the sensitivity and reliability of subsequent operations. In the field of chips for measuring the displacement of objects to be measured, the measurement error is also large, resulting in defects in the use of corresponding electronic products. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a displacement sensor chip based on the AMR effect, and the specific technical solution is as follows:

[0004] A displacement sensor chip based on the AMR effect, the main structure of which includes a silicon layer, a silicon oxide layer, a magnetically sensitive film layer, a silicon nitride layer and an aluminum layer in sequence. The structure of the magnetically sensitive film layer is divided into four regions, namely, one, two, three and four, by magnetically sensitive lines. The number of magnetically sensitive lines in each region is the same, and the size of the magnetically sensitive lines is 8-20um. The magnetically sensitive lines in the one and three regions are alternately connected to form a No. 1 Wheatstone bridge, and the magnetically sensitive lines in the two and four regions are alternately connected to form a No. 2 Wheatstone bridge. The two ends of the magnetically sensitive lines in each group of Wheatstone bridges are designed to be acute-angle structures. The silicon nitride on the surface of the two ends of each group of magnetically sensitive lines is etched to make it directly conductive with the aluminum layer electrode, and the magnetically sensitive lines are connected to each other through the aluminum lines and gathered to the PAD.

[0005] The main material of the magnetic sensitive film layer is NiFe, and its structure is adaptively designed. The magnetic sensitive film in each area can be equivalently divided into two groups of resistors through different connections. The magnetic sensitive lines that make up the two groups of resistors are regularly alternately connected; the two groups of Wheatstone bridges each occupy the magnetic sensitive lines of two areas, and there are 4 groups of equivalent magnetic sensitive resistors, ensuring that the displacement distance of the two groups of Wheatstone bridges for the output curve is the distance between the magnetic sensitive lines of the two areas.

[0006] Further improvements are: the thickness of the silicon oxide layer is 500nm-2um, the thickness of the magnetic sensitive film layer is 20-200nm, the thickness of the silicon nitride layer is 0.5-2um, and the thickness of the aluminum layer is 1-2um.

[0007] Further improvements are as follows: the two ends of the magneto-sensitive lines in each set of Wheatstone bridges are designed with an acute angle of 20°-40°, inducing the orderly arrangement of the magnetic moments inside the magneto-sensitive film and improving the film performance. Each magneto-sensitive resistance line is connected through A1, ensuring good connectivity without destroying the magnetic moment structure inside the line.

[0008] A further improvement is that the width of the magnetic sensitive lines is 4-40 um, and the spacing between the lines is 1-5 um.

[0009] A further improvement is that each group of bridges in each group of Wheatstone bridges is independently set to prevent mutual interference.

[0010] Further improvements are: the length of each group of bridges is consistent to ensure the minimum offset of the Wheatstone bridge, and the chip utilization is maximized through optimized design.

[0011] Further improvements are: growing a silicon oxide passivation layer with a thickness of 1-2um on the surface of the aluminum layer. The first is to protect the Al lines from oxidation and increase the working stability and reliability of the chip. The second is to cover the A1 lines, enhance the adhesion of the pad position, enhance the tensile strength after wire bonding, and thus enhance the chip reliability.

[0012] Beneficial effects of the present invention: The present invention provides a displacement sensor chip based on the AMR effect, which can basically maintain a relative stability for the temperature output of the chip through the sine and cosine curve output relative to the displacement through a double Wheatstone bridge, and the measurement error of the displacement is small through the centering structure design. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of the structure of a displacement sensor chip based on the AMR effect in an embodiment;

[0014] Figure 2 is a schematic diagram of the structure of the magnetic sensitive film layer in the embodiment;

[0015] Figure 3 Schematic diagram of the exposed structure of the magnetic sensitive film layer in the embodiment;

[0016] Figure 4 Schematic diagram of the connection structure between the magnetic sensitive film layer and the aluminum layer in the embodiment;

[0017] Figure 5 It is a schematic diagram of the surface structure of the aluminum layer and the aluminum electrode;

[0018] Figure 6 This is the overall effect diagram of the chip. DETAILED DESCRIPTION

[0019] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the scope of protection.

[0020] This embodiment provides a displacement sensor chip based on the AMR effect, referring to Figure 1, the materials of the chip are: 1. Si; 2. SiO2; 3. Magnetic sensitive film; 4. Si3N4 / SiO2; 5. A1. The first layer of material is Si, and its main purpose is to meet the needs of semiconductor wafer processing and be used as a substrate. The second layer of material is silicon oxide, with a thickness of 500nm~2um, and its function is passivation to prevent leakage of Si substrate. The third layer of material is magnetic sensitive film material, with a thickness of 20nm~200nm, and its function is to sense the magnetic field signal in the environment and convert it into a voltage signal. The fourth layer of material is Si3N4, with a thickness of 0.5um~2um, which protects the third layer of material from oxidation and plays a role in voltage isolation. The fifth layer of material is Al, with a thickness of 1um~2um. Through a certain structural design, the third layer of material is led out to the PAD position for easy wire bonding and packaging. The sixth layer of material is SiO2, with a thickness of 1um~2um. While protecting the A1 electrode from oxidation, it can also improve the adhesion of the Al electrode at the PAD position and improve the reliability of the chip.

[0021] refer to Figure 2 , the magnetic sensitive lines are divided into 4 areas, from left to right, they are Area 1, Area 2, Area 3, Area 4, the number of lines in each area is the same, which can be adjusted according to the chip size, and the line size is generally between 8um-20um. The chip size can be appropriately increased or decreased according to the different magnetic grating displacement sensor chip resistance requirements, and the size is roughly distributed between 500um*500um and 8000um*8000um. The main structural features are as follows: 1. The magnetic sensitive film in each area can be equivalently divided into two groups of resistors through different connections, and the magnetic sensitive lines that make up the two groups of resistors are regularly connected alternately; 2. The two groups of Wheatstone bridges each occupy the magnetic sensitive lines of two areas, and the four groups of equivalent magnetic sensitive resistors are: No. 1 Wheatstone bridge corresponds to the magnetic sensitive lines of areas 1 and 3, and No. 2 Wheatstone bridge corresponds to the magnetic sensitive lines of areas 2 and 4, ensuring that the displacement distance of the two groups of Wheatstone bridges for the output curve is the distance of the magnetic sensitive lines of the two areas; 3. The two ends of each magnetic sensitive resistor strip are designed as an acute angle structure, and the angle is generally 20°~40°. The main function is to induce the orderly arrangement of the magnetic moment inside the magnetic sensitive film and improve the performance of the film. Each magnetic sensitive resistor line is connected by Al, which ensures good connectivity without destroying the magnetic moment structure inside the line; 4. According to different parameters, the line width is 4um-40um, and the spacing between the lines is 1um-5um; 5. Each group of bridges of the Wheatstone bridge is placed independently to prevent the bridges from interfering with each other. The length of each bridge group is consistent, ensuring the minimum offset of the Wheatstone bridge, and maximizing chip utilization through optimized design.

[0022] refer to Figure 3, the two ends of each group of lines are etched away by reactive ion etching, the silicon nitride on the surface is etched away, and the magnetic sensitive film on the lower layer is exposed, so as to facilitate interconnection with the Al electrode on the upper layer. Figure 4 At the joint of the Wheatstone bridge, the silicon nitride in the area that needs to be connected has been etched away through the front-end process, exposing the NiFe film at the bottom. Through a certain Al line pattern, the various resistor bridges are connected and gathered at the PAD position. The design of the Al line ensures that the length-to-width ratio from the pad to the magnetic sensitive line connection point is the same, further reducing the offset at the output end of the chip bridge. Figure 5 After the Al electrode structure is grown, a SiO2 passivation layer will be grown on the surface. The main purpose is to protect the Al line from oxidation and increase the working stability and reliability of the chip. The second is to cover the A1 line, enhance the adhesion of the pad position, enhance the tensile strength after wire bonding, and thus enhance the chip reliability. The overall chip structure effect is as follows Figure 6 shown.

[0023] Beneficial effects of this embodiment: This embodiment provides a displacement sensor chip based on the AMR effect, which can basically maintain a relative stability for the temperature output of the chip through the sine-cosine curve output of the double Wheatstone bridge relative to the displacement, and the measurement error of the displacement is small through the centering structure design.

[0024] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A displacement sensor chip based on the AMR effect, comprising a silicon layer, a silicon oxide layer, a magnetic sensitive film layer, a silicon nitride layer and an aluminum layer in sequence, characterized in that: The structure of the magnetically sensitive film layer is divided into four regions, namely, one, two, three and four, by magnetically sensitive lines. The number of magnetically sensitive lines in each region is the same, and the size of the magnetically sensitive lines is 8-20um. The magnetically sensitive lines in the one and three regions are alternately connected to form a No. 1 Wheatstone bridge, and the magnetically sensitive lines in the two and four regions are alternately connected to form a No. 2 Wheatstone bridge. The two ends of the magnetically sensitive lines in each group of Wheatstone bridges are designed to be acute-angle structures. The silicon nitride on the surface of the two ends of each group of magnetically sensitive lines is etched to make it directly conductive with the aluminum layer electrode, and the magnetically sensitive lines are connected to each other through the aluminum lines and gathered to the PAD.

2. The displacement sensor chip based on the AMR effect according to claim 1, characterized in that: The thickness of the silicon oxide layer is 500nm-2um, the thickness of the magnetic sensitive film layer is 20-200nm, the thickness of the silicon nitride layer is 0.5-2um, and the thickness of the aluminum layer is 1-2um.

3. The displacement sensor chip based on the AMR effect according to claim 1, characterized in that: The two ends of the magnetically sensitive lines in each set of Wheatstone bridges are designed to have an acute angle of 20°-40°.

4. The displacement sensor chip based on the AMR effect according to claim 1, characterized in that: The width of the magnetic sensitive lines is 4-40um, and the spacing between the lines is 1-5um.

5. The displacement sensor chip based on the AMR effect according to claim 1, characterized in that: Each group of bridges in each group of Wheatstone bridges is set independently to prevent mutual interference.

6. The displacement sensor chip based on the AMR effect according to claim 5, characterized in that: The length of each bridge group is the same.

7. The displacement sensor chip based on the AMR effect according to claim 1, characterized in that: A silicon oxide passivation layer is grown on the surface of the aluminum layer.

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