A processing method of GMI magnetic sensor based on thin film self-coiling technology

Abstract

The application belongs to the technical field of micro electro mechanical system (MEMS), and particularly relates to a processing method of a GMI magnetic sensor based on a thin film self-rolling technology. A silicon wafer is used as a silicon substrate layer, a germanium sacrificial layer, a low-frequency silicon nitride layer, a high-frequency silicon nitride layer and a copper metal wire are deposited on the silicon substrate layer, the intrinsic stress between the low-frequency silicon nitride layer and the high-frequency silicon nitride layer is released by etching the germanium sacrificial layer, the self-rolling of the amorphous wire wrapped in the silicon nitride strain layer is triggered, the transition from two-dimensional to three-dimensional is realized, the micro-nanometer tube containing the amorphous wire and the spiral coil, i.e. the GMI magnetic sensor, is formed by self-rolling. The inner diameter of the GMI magnetic sensor is in the order of 100 microns. Meanwhile, the GMI magnetic sensor utilizes the self-rolling technology of the thin film, reduces the process difficulty, and the winding coil is formed by the self-rolling technology of the thin film, so that the amorphous wire will not be bent due to winding. Therefore, the GMI magnetic sensor has superior structural performance and the advantage of small size.

Description

Technical Field

[0001] This invention belongs to the field of microelectromechanical systems (MEMS) technology, and specifically designs a fabrication method for a GMI magnetic sensor based on thin film self-rolling technology. Background Technology

[0002] Microelectromechanical systems (MEMS) are miniature electromechanical devices or systems that integrate micromechanical and microelectronic functions. Devices based on MEMS technology (such as MEMS sensors and drivers) are widely used due to their advantages such as small size, light weight, low power consumption, good durability, low price, and stable performance, especially in the automotive, aerospace, and electronics industries.

[0003] GMI magnetic sensors are based on the giant magnetoresistance effect. When a suitable high-frequency current is applied to the amorphous wire, and a bias magnetic field is applied along the axis of the amorphous wire through a coil, even a slight change in the external magnetic field along the axis of the amorphous wire will cause a huge change in the impedance of the amorphous wire, thereby causing a change in the voltage across the amorphous wire.

[0004] Manufacturing GMI magnetic sensors using traditional processes first requires winding enameled wire coils onto amorphous wire, then soldering the coiled amorphous wire onto pads on a PCB board. Amorphous wire GMI magnetic sensors manufactured using this process are relatively large and still require miniaturization. From a manufacturing perspective, the coil winding process causes the amorphous wire to bend and generate stress, degrading device performance and resulting in poor manufacturing consistency, severely impacting the performance and consistency of amorphous wire GMI magnetic sensors.

[0005] Thin-film self-curling technology is a method that utilizes the residual stress within a material to achieve the self-bending of a tensile / compressive dual-stress layer formed from a two-dimensional thin-film material. Devices fabricated using thin-film self-curling technology can reach the micrometer scale, thus enabling its application in the fabrication of GMI magnetic sensors to achieve miniaturization of magnetic sensors. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of large size and poor processing consistency of existing magnetic sensors, and to provide a processing method for GMI magnetic sensors based on thin film self-rolling technology, so that GMI magnetic sensors have the advantages of small size, high sensitivity, fast response speed and mass production capability.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for fabricating a GMI magnetic sensor based on thin-film self-rolling technology specifically includes the following steps:

[0009] Step 1): Clean the square silicon substrate 1, and use an electron beam to evaporate a germanium sacrificial layer 2 on the front side of the silicon substrate 1 to obtain the substrate;

[0010] Step 2): On the substrate obtained in Step 1), a low-frequency silicon nitride layer 3 and a high-frequency silicon nitride layer 4 are sequentially deposited by plasma chemical vapor deposition.

[0011] Step 3): Based on Step 2), a film is formed, photoresist is spin-coated, the photoresist is baked, and exposure and development are performed. A protrusion is etched on the silicon substrate layer 1 using inductively coupled plasma method, and then the photoresist is removed. The protrusion is, from bottom to top, a germanium sacrificial layer 2, a low-frequency silicon nitride layer 3, and a high-frequency silicon nitride layer 4.

[0012] Step 4): On the protrusion in Step 3), a film is formed, photoresist is spin-coated, the photoresist is baked, and exposure and development are performed. Copper metal wires 5 are formed on the high-frequency silicon nitride layer 4 by electron beam deposition, and then the photoresist is removed.

[0013] The two ends of the copper metal wire 5 are located at one end of the high-frequency silicon nitride layer 4. The copper metal wire 5 is bent to form two wires of different lengths, and the bent end is located at the other end of the high-frequency silicon nitride layer 4.

[0014] Step 5): Based on Step 4), film formation, spin coating of photoresist, photoresist baking, exposure and development are performed. Using atomic layer deposition, an aluminum oxide protective layer 6 is deposited on the two wires of the copper metal wire 5, and then the photoresist is removed.

[0015] Step 6): Based on Step 5), place and fix the amorphous wire 7 with photoresist, so that the amorphous wire 7 is horizontally located at the end of the high-frequency silicon nitride layer 4 corresponding to the bent end of the copper metal wire 5, and the axis of the amorphous wire 7 is parallel to the width direction of the high-frequency silicon nitride layer 4.

[0016] Step 7): Based on Step 6), photoresist is coated and baked so that the upper end of the substrate in Step 6) is covered with a photoresist layer 8;

[0017] Step 8): Based on step 7), perform exposure and development, open the end face of the photoresist layer 8 near the amorphous wire 7 as an etching window, and then immerse the whole in a hydrogen peroxide solution with a mass concentration of 65%~80% for 12h~36h. Etch away at least 1 / 2 length of the germanium sacrificial layer 2 from one end of the amorphous wire 7, and then remove the photoresist.

[0018] Due to the selective etching of the germanium sacrificial layer 2, under the interlayer stress of the low-frequency silicon nitride layer 3 and the high-frequency silicon nitride layer 4, the low-frequency silicon nitride layer 3, the high-frequency silicon nitride layer 4 and the alumina protective layer 6 roll upward to form a micro-nanotube with an amorphous wire 7 wrapped in the middle. At the same time, the two wires of the metal wire 5 form two winding coils connected at one end; thus, a GMI magnetic sensor is obtained, and the volume of the GMI magnetic sensor is on the order of hundreds of micrometers.

[0019] Furthermore, the two wires of the copper metal wire 5 have an acute angle between them, and one of the wires is arranged along one side of the high-frequency silicon nitride layer 4, so that when the metal wire 5 is curled, the connecting terminals of the two winding coils formed by the two wires are located at the lower end of the GMI magnetic sensor.

[0020] Furthermore, the amorphous wire 7 has a diameter of 10um to 80um, and the inner diameter of the micro-nanotube is 10um to 100um.

[0021] Furthermore, the stress of the low-frequency silicon nitride layer 3 is 900-1100 MPa, and the stress of the high-frequency silicon nitride layer 4 is 280-320 MPa.

[0022] Furthermore, the adhesive baking in steps 3), 4), and 5) is performed at 100°C for 60 seconds.

[0023] Furthermore, the thickness of the germanium metal layer 2, the low-frequency silicon nitride layer 3, and the high-frequency silicon nitride layer 4 is 30 nm; the thickness of the metal wire 5 is 100 nm.

[0024] The beneficial technical effects of the present invention are as follows:

[0025] This invention discloses a fabrication method for a GMI magnetic sensor based on thin-film self-rolling technology. Using a silicon wafer as a substrate, a germanium sacrificial layer, a low-frequency silicon nitride layer, a high-frequency silicon nitride layer, and copper metal wires are deposited on the silicon substrate. By etching the germanium sacrificial layer, the interlayer stress of the low-frequency and high-frequency silicon nitride layers is released, triggering the self-rolling of the silicon nitride strain layer around the amorphous wires, achieving a transition from two-dimensional to three-dimensional. The self-rolling forms a micro / nanotube containing amorphous wires and a spiral coil, i.e., the GMI magnetic sensor. The inner diameter of the GMI magnetic sensor is on the order of hundreds of micrometers, and its volume is reduced by more than 50% compared to GMI magnetic sensors fabricated using traditional IC manufacturing processes. Furthermore, the GMI magnetic sensor of this invention utilizes thin-film self-rolling technology to simplify the 3D process to a 2D process, reducing process steps and lowering the manufacturing difficulty. Moreover, the winding coil is formed using thin-film self-rolling technology, preventing the amorphous wires from bending due to winding. Therefore, the GMI magnetic sensor of this invention has superior structural performance and a small size. Attached Figure Description

[0026] Figure 1This is a schematic diagram of the structure of a GMI magnetic sensor based on thin film self-rolling technology according to the present invention.

[0027] Figure 2 This is a schematic diagram of step 1) of the present invention.

[0028] Figure 3 This is a schematic diagram of step 2) of the present invention.

[0029] Figure 4 This is a schematic diagram of step 3) of the present invention.

[0030] Figure 5 This is a schematic diagram of step 4) of the present invention.

[0031] Figure 6 This is a schematic diagram of step 5) of the present invention.

[0032] Figure 7 This is a schematic diagram of step 6) of the present invention.

[0033] Figure 8 This is a schematic diagram of step 7) of the present invention.

[0034] Figure 9 This is a schematic diagram of step 8) of the present invention.

[0035] Figure 10 This is a schematic diagram of step 8) of the present invention.

[0036] The structure consists of: 1. Silicon substrate layer; 2. Germanium sacrificial layer; 3. Low-frequency silicon nitride; 4. High-frequency silicon nitride; 5. Copper conductor; 6. Alumina protective layer; 7. Amorphous wire; and 8. Photoresist layer. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Example

[0038] See Figure 1 A method for fabricating a GMI magnetic sensor based on thin-film self-rolling technology specifically includes the following steps:

[0039] Step 1): Clean the square silicon substrate 1. Then, use an electron beam to evaporate a germanium sacrificial layer 2 on the front side of the silicon substrate 1 to obtain the substrate. (See attached image) Figure 2 ;

[0040] Step 2): On the substrate obtained in Step 1), a low-frequency silicon nitride layer 3 and a high-frequency silicon nitride layer 4 are sequentially deposited using plasma chemical vapor deposition, as shown in [the diagram]. Figure 3 ;

[0041] Step 3): Based on Step 2), a film is formed, photoresist is spin-coated, the photoresist is baked, and exposure and development are performed. Raised protrusions are etched onto the silicon substrate 1 using inductively coupled plasma (ICP-PAP) etching. The photoresist is then removed. The raised protrusions, from bottom to top, consist of a germanium sacrificial layer 2, a low-frequency silicon nitride layer 3, and a high-frequency silicon nitride layer 4. (See...) Figure 4 ;

[0042] Step 4): On the protrusions of Step 3), film deposition, spin-coating of photoresist, photoresist baking, exposure and development are performed. Copper is deposited using an electron beam to form copper metal wires 5 on the high-frequency silicon nitride layer 4. The photoresist is then removed. (See...) Figure 5 ;

[0043] The two ends of the copper metal wire 5 are located at one end of the high-frequency silicon nitride layer 4. The copper metal wire 5 is bent to form two wires of different lengths, and the bent end is located at the other end of the high-frequency silicon nitride layer 4.

[0044] Step 5): Based on Step 4), perform film formation, spin-coating of photoresist, photoresist baking, exposure and development. Using atomic layer deposition, deposit an aluminum oxide protective layer 6 on the two conductive lines of the copper metal conductor 5. Then remove the photoresist. (See...) Figure 6 ;

[0045] Step 6): Based on Step 5), place and fix the amorphous wire 7 using photoresist, so that the amorphous wire 7 is horizontally located at the end of the high-frequency silicon nitride layer 4 corresponding to the bent end of the copper metal wire 5, and the axis of the amorphous wire 7 is parallel to the width direction of the high-frequency silicon nitride layer 4, see... Figure 7 ;

[0046] Step 7): Based on Step 6), photoresist is coated and baked, so that the upper end of the substrate in Step 6) is covered with photoresist layer 8, see... Figure 8 ;

[0047] Step 8): Based on step 7), perform exposure and development, open the end face of the photoresist layer 8 near the amorphous wire 7 as an etching window, and then immerse the whole in a 75% hydrogen peroxide solution for 12h~36h. Etch away at least 1 / 2 length of the germanium sacrificial layer 2 from one end of the amorphous wire 7, and then remove the photoresist.

[0048] Due to the selective etching of the germanium sacrificial layer 2, under the interlayer stress of the low-frequency silicon nitride layer 3 and the high-frequency silicon nitride layer 4, the low-frequency silicon nitride layer 3, the high-frequency silicon nitride layer 4, and the alumina protective layer 6 self-roll upwards to form micro-nanotubes with amorphous wires 7 sandwiched in the middle. Simultaneously, the two wires of the metal wire 5 form two wound coils connected at one end; thus, a GMI magnetic sensor is obtained. The volume of the GMI magnetic sensor is on the order of hundreds of micrometers. Figure 9 and Figure 10 .

[0049] The two conductors of the copper metal wire 5 form an acute angle. One conductor is arranged along one side of the high-frequency silicon nitride layer 4, so that when the metal wire 5 is coiled, the connecting terminals of the two winding coils formed by the two conductors are located at the lower end of the GMI magnetic sensor. When the two electrodes of the metal wire 5 are energized, the currents in the two winding coils are the same in magnitude but opposite in direction, and the electromagnetism formula is: B=μ0IN / L, where I is the current flowing through, N is the number of turns of the coil, and μ0 is a constant, equal to 4π•10 -7 L is the coil length, so an effective magnetic field can be generated in the direction of the amorphous wire axis 7.

[0050] The amorphous wire 7 has a diameter of 10um to 80um, and the inner diameter of the micro-nanotube is 10um to 100um.

[0051] The low-frequency silicon nitride layer 3 has a stress of 280~320MPa, and the high-frequency silicon nitride layer 4 has a stress of 900~1100MPa.

[0052] The adhesive is baked at 100°C for 60 seconds in steps 3), 4) and 5).

[0053] The thickness of the germanium metal layer 2, the low-frequency silicon nitride layer 3, and the high-frequency silicon nitride layer 4 is 30 nm; the thickness of the metal wire 5 is 100 nm.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a GMI magnetic sensor based on thin-film self-rolling technology, characterized in that: Specifically, it includes the following steps: Step 1): Clean the square silicon substrate (1), and use an electron beam to evaporate a germanium sacrificial layer (2) on the front side of the silicon substrate (1) to obtain the substrate; Step 2): On the substrate obtained in Step 1), a low-frequency silicon nitride layer (3) and a high-frequency silicon nitride layer (4) are deposited sequentially by plasma chemical vapor deposition. Step 3): Based on Step 2), a film is formed, photoresist is spin-coated, the photoresist is baked, and the film is exposed and developed. The protrusions are etched on the silicon substrate layer (1) using inductively coupled plasma method, and then the photoresist is removed. The protrusions are, from bottom to top, germanium sacrificial layer (2), low-frequency silicon nitride layer (3) and high-frequency silicon nitride layer (4). Step 4): On the protrusion in Step 3), a film is formed, photoresist is spin-coated, the photoresist is baked, and the exposure and development are performed. Copper metal is deposited using an electron beam to form copper metal wires (5) on the high-frequency silicon nitride layer (4), and then the photoresist is removed. The two electrodes of the copper metal wire (5) are located at one end of the high-frequency silicon nitride layer (4). The copper metal wire (5) is bent to form two wires of different lengths, and the bent end is located at the other end of the high-frequency silicon nitride layer (4). Step 5): Based on Step 4), film formation, spin coating of photoresist, baking of photoresist, exposure and development are performed. Using atomic layer deposition, an aluminum oxide protective layer (6) is deposited on the two wires of the copper metal wire (5), and then the photoresist is removed. Step 6): Based on step 5), place and fix the amorphous wire (7) with photoresist, so that the amorphous wire (7) is horizontally located at the end of the high-frequency silicon nitride layer (4) corresponding to the bent end of the copper metal wire (5), and the axis of the amorphous wire (7) is parallel to the width direction of the high-frequency silicon nitride layer (4). Step 7): Based on Step 6), photoresist is applied and baked so that the upper end of the substrate in Step 6) is covered with a photoresist layer (8). Step 8): Based on step 7), perform exposure and development, open the end face of the photoresist layer (8) near the amorphous wire (7) as an etching window, and then immerse the whole in a hydrogen peroxide solution with a mass concentration of 65%~80% for 12h~36h. Etch away at least 1 / 2 length of germanium sacrificial layer (2) from one end of the amorphous wire (7), and then remove the photoresist. Due to the selective etching of the germanium sacrificial layer (2), under the interlayer stress of the low-frequency silicon nitride layer (3) and the high-frequency silicon nitride layer (4), the low-frequency silicon nitride layer (3), the high-frequency silicon nitride layer (4) and the aluminum oxide protective layer (6) curl upward to form a micro-nanotube with an amorphous wire (7) in the middle. At the same time, the two wires of the metal wire (5) form two winding coils connected at one end; thus, a GMI magnetic sensor is obtained, and the volume of the GMI magnetic sensor is on the order of hundreds of micrometers.

2. The fabrication method of a GMI magnetic sensor based on thin-film self-rolling technology according to claim 1, characterized in that: The two wires of the copper metal wire (5) have an acute angle between them. One of the wires is arranged along one side of the high-frequency silicon nitride layer (4), so that when the metal wire (5) is curled, the connecting terminals of the two winding coils formed by the two wires are located at the lower end of the GMI magnetic sensor.

3. The fabrication method of a GMI magnetic sensor based on thin-film self-rolling technology according to claim 1, characterized in that: The amorphous filament (7) has a diameter of 10um to 80um, and the inner diameter of the micro-nanotube is 10um to 100um.

4. The fabrication method of a GMI magnetic sensor based on thin-film self-rolling technology according to claim 1, characterized in that: The low-frequency silicon nitride layer (3) has a stress of 900~1100MPa, and the high-frequency silicon nitride layer (4) has a stress of 280~320MPa.

5. The fabrication method of a GMI magnetic sensor based on thin-film self-rolling technology according to claim 1, characterized in that: The adhesive is baked at 100°C for 60 seconds in steps 3), 4) and 5).

6. The fabrication method of a GMI magnetic sensor based on thin-film self-rolling technology according to claim 1, characterized in that: The thickness of the germanium sacrificial layer (2), the low-frequency silicon nitride layer (3), and the high-frequency silicon nitride layer (4) is 30 nm; the thickness of the metal wire (5) is 100 nm.

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