Arc-shaped pressure sensor and preparation method thereof

Abstract

The invention provides an arc pressure sensor and a preparation method thereof. The arc-shaped pressure sensor comprises an arc-shaped substrate, a convex structure, a pressure-sensitive diaphragm, a cavity structure, a piezoresistive resistor, an electrode signal interface and a highly boron-doped lead area. The pressure sensor is of an arc-shaped structure and can be conveniently attached to the blood vessel wall to measure blood pressure, the piezoresistive resistor outputs signals in a half-bridge mode, the three electrode leading-out interfaces are distributed at the short edge below the arc-shaped substrate at equal intervals, packaging is simple, and operation and treatment of doctors are facilitated. Wafer thinning is carried out by adopting a method of firstly corroding a substrate on the back surface and then etching the substrate, and the preparation of the arc-shaped pressure sensor is realized in a manner of forming a sensor unit structure by designing a convex structure. Compared with a traditional pressure sensor, the pressure sensor is easy to install, safe in manufacturing material, small in size, high in precision and capable of being placed in a medical catheter to be attached to the blood vessel wall for pressure measurement, and a doctor can conveniently, rapidly and accurately formulate a personalized treatment scheme for a patient.

Description

Technical Field

[0001] The invention belongs to the technical field of microelectronic sensors and relates to an arc pressure sensor and a preparation method thereof. Background Art

[0002] In recent years, with the continuous improvement of MEMS technology, the performance of pressure sensors has gradually improved, and they also have broad application prospects in the medical field.

[0003] Coronary artery stenosis is one of the common diseases in modern medicine. Doctors usually need to perform percutaneous coronary intervention on patients, but before the operation, it is necessary to evaluate the severity of the patient's coronary artery stenosis function in order to formulate a surgical treatment plan. Fractional flow reserve (FFR) is a commonly used diagnostic method in medicine to evaluate the impact of coronary artery stenosis on myocardial blood flow. It refers to the ratio of the mean pressure at the distal end of the coronary artery stenosis to the mean pressure of the aorta at the coronary artery orifice under the maximum hyperemia of the myocardium. During the entire blood flow transmission process, there is no energy loss when the normal coronary artery flows from the proximal end to the distal end, so the pressure remains constant and the FFR value is "1"; but if there is a stenotic lesion in the epicardial blood vessel, the pressure will change when the blood flows through the lesion area. If the pressure in the normal blood vessel and the lesion blood vessel is measured separately, the FFR value can be calculated. The lower the FFR value, the more severe the coronary artery stenosis.

[0004] Therefore, it is an urgent problem to produce a small and high-precision arc pressure sensor that can be placed in human blood vessels and attached to the blood vessel wall for fixed-point blood pressure measurement, so that doctors can evaluate the patient's coronary artery blood supply and quickly and accurately formulate personalized surgical plans for patients. Summary of the invention

[0005] The purpose of the present invention is to provide an arc pressure sensor structure, including an arc substrate, a protrusion structure, a pressure-sensitive membrane, a cavity structure, a piezoresistive resistor, an electrode signal interface and a high-boron-doped lead area. The structure is simple, easy to install, has strong biocompatibility, a small size, and high precision, and can be placed in a human blood vessel for pressure measurement.

[0006] An arc pressure sensor comprises an arc substrate, a protruding structure, a pressure-sensitive membrane, a cavity structure, a piezoresistive resistor, an electrode signal interface and a high-boron-doped lead area; the cavity structure is located above the arc substrate structure, the protruding structure is located on the short side of the arc substrate structure, the pressure-sensitive membrane is connected to the arc substrate through an insulating layer and is located above the cavity structure, and the piezoresistive resistor, the electrode signal interface and the high-boron-doped lead area are distributed on the pressure-sensitive membrane.

[0007] The arc pressure sensor is designed to be manufactured in the form of a unit structure; the sensor unit structure includes multiple arc pressure sensors, a fixed end of the unit structure outer frame, and an etched suspended area; the arc pressure sensors contained in a unit structure can be designed according to the size of the sensor and the requirements of the corrosion process, and the number of sensors included is ≥2.

[0008] The long side of the arc-shaped substrate structure is an arc, the arc angle is 28°-30°, and the vertical length is 500um-600um; there is a convex structure on the short side of the arc-shaped substrate, and the convex shape can be any polygon with a narrow upper end and a wide lower end, or any polygon with wide ends and a narrow middle. One end of the convex is connected to the fixed end of the unit structure outer frame, and the other end is connected to the short side of the arc-shaped substrate to form a stress concentration area.

[0009] The etched suspended area surrounds the outer side of the arc substrate and the protruding structure and the inner side of the fixed end of the unit structure outer frame and is formed by an etching process to separate the arc substrates of multiple sensors, making it easier to take out the subsequent sensors.

[0010] The two long sides of the arc-shaped substrate structure have the same center and the same arc, and the difference in arc width is between 70um and 80um.

[0011] The piezoresistive resistor is axially symmetrical with the center line of the pressure-sensitive membrane, and is in a vertical or horizontal form. The electrode signal interface is parallel to the lower short side of the arc-shaped substrate structure, and the spacing of the electrode signal interface and the lateral spacing between the electrode signal interface and the inner and outer arcs of the arc-shaped substrate are the same. The piezoresistive resistor is connected inside the cavity through a high-boron-doped lead, and is connected to the electrode signal interface end through a metal outside the cavity to form a half-bridge circuit. The short side of the arc-shaped substrate is perpendicular to the long side of the inner and outer arcs.

[0012] Compared with the existing sensors, the arc pressure sensor of the present invention has the following advantages:

[0013] First, it is easy to install. The pressure sensor of the present invention has an arc-shaped structure, which is convenient for attaching to the blood vessel wall to measure blood pressure. The piezoresistive resistor uses a half-bridge connection to convert the pressure signal into an electrical signal output. The three electrode lead interfaces are equidistantly distributed on the short side below the arc-shaped substrate. The package is simple and convenient for doctors to operate and treat.

[0014] Second, it has strong biocompatibility. The materials used in the arc pressure sensor of the present invention are compatible with the human body. The piezoresistive resistor and the electrode are connected by a combination of high-boron-doped leads and metal leads. The metal lead area is very small, and the material performance is stable and reliable. The subsequent packaging will also cover the metal. Multi-layer protection measures are taken to ensure the compatibility and reliability of the sensor. Therefore, the pressure sensor of this structure can be placed in the blood vessels of the human body for pressure measurement.

[0015] Third, the volume is small. The vertical length of the long side of the arc pressure sensor of the present invention is 500um-600um, the width difference between the outer arc diameter and the inner arc diameter is 70um-80um, that is, the vertical length of the short side is 70um-80um, and the thickness is less than 80um. Its volume is much smaller than that of ordinary pressure sensors, so it can be widely used in medical catheters.

[0016] Fourth, high precision: The thickness of the pressure-sensitive membrane and the size of the cavity of the arc-shaped pressure sensor of the present invention can be precisely controlled through the process, so the manufactured sensor has good sensitivity consistency and high precision.

[0017] Another object of the present invention is to provide a method for preparing the arc pressure sensor, comprising the following steps:

[0018] 1. The substrate silicon wafer is photolithographically and etched to form a cavity structure;

[0019] 2. The substrate silicon wafer is bonded with silicon dioxide and the SOI wafer, a silicon etching mask layer is deposited and the SOI wafer is etched to form a pressure-sensitive membrane;

[0020] 3. Grow silicon dioxide on the front side, photolithography and implantation to form a piezoresistive resistor;

[0021] 4. Deposit silicon dioxide on the front side, and form contact holes by photolithography and etching;

[0022] 5. Sputter metal on the front side and photoetch to form the electrode signal interface;

[0023] 6. Glue coating for protection on the front side, photolithography window and silicon etching for thinning on the back side;

[0024] 7. Photolithography and etching of silicon to form an arc-shaped pressure sensor structure;

[0025] Advantages and positive effects of the present invention:

[0026] Compared with the traditional pressure sensor, the arc pressure sensor of the present invention has the following advantages: first, its long side is in an arc shape, which is similar to the structure of the human blood vessel wall. It can be attached to the blood vessel wall to measure blood pressure. Measuring blood pressure in this installation method can save space and facilitate doctors to perform complex operations; second, its manufacturing process uses materials compatible with the human body, and the piezoresistive resistor is connected by a combination of high-boron-doped leads and metal leads to form a half-bridge circuit for converting pressure signals and electrical signals. When encapsulating, the electrode signal interface is coated with glue to ensure the safety and reliability of the sensor; third, it adopts a manufacturing method of first back-etching the substrate and then etching the substrate to thin the wafer, and the arc pressure sensor is prepared by designing a protruding structure and forming a sensor unit structure. Fourth, it has a very small size and high precision. It can be installed in a medical catheter and attached to the blood vessel wall to measure the pressure difference between the coronary artery stenosis area and the normal blood vessel area, thereby evaluating the coronary artery blood supply. Therefore, it has a good development prospect in the medical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1( a ) is a top view of the arc pressure sensor structure of the present invention, and FIG. 1( b ) is a side view of the arc pressure sensor structure of the present invention.

[0028] FIG1(c) is a top view of a conventional pressure sensor installed in a blood vessel.

[0029] FIG1( d ) is a top view schematically showing the installation of the arc-shaped pressure sensor of the present invention placed in a blood vessel.

[0030] Figure 2(a) to Figure 2(g) This is the main preparation process of the arc pressure sensor of the present invention.

[0031] Figure 3(a) to Figure 3(b) Schematic diagram of the convex structure of the arc pressure sensor of the present invention and the stress simulation result diagram

[0032] Figure 4 Schematic diagram of the unit structure of the arc pressure sensor of the present invention.

[0033] In the figure:

[0034] 1-arc substrate, 2-convex structure, 3-pressure-sensitive membrane, 4-cavity structure, 5-piezoresistive resistor, 6-electrode signal interface,

[0035] 7-highly doped boron lead area, 8-unit structure outer frame fixed end, 9-etched suspended area, 10-blood vessel, 11-traditional pressure sensor

[0036] Substrate DETAILED DESCRIPTION

[0037] Example 1: Arc-shaped pressure sensor structure

[0038] The structure of the arc pressure sensor is shown in Figure 1, including an arc substrate 1, a protruding structure 2, a pressure-sensitive membrane 3, a cavity structure 4, a piezoresistor 5, an electrode signal interface 6 and a high-boron-doped lead area 7. The cavity structure 4 is located above the arc substrate 1, and is formed by etching the substrate silicon wafer and bonding it to the SOI wafer; the protruding structure 2 is located on the short side of the arc substrate 1, and is made by an etching process to form a stress concentration area for subsequent wafer removal; the pressure-sensitive membrane 3 is located above the cavity structure 4, and is connected to the arc substrate 1 as a whole through an insulating layer; the piezoresistor 5, the electrode signal interface 6 and the high-boron-doped lead area 7 are distributed on the pressure-sensitive membrane 3, and the piezoresistor 5 is connected to the electrode signal interface 6 through the high-boron-doped lead area 7 to form a circuit for signal acquisition and output.

[0039] The substrate of a traditional pressure sensor is rectangular or square and can only be placed in the middle of a blood vessel to avoid touching the blood vessel wall and causing damage, as shown in FIG1(c), where 10 is a plan view of the blood vessel and 11 is a traditional pressure sensor substrate.

[0040] The pressure sensor substrate of the present invention is arc-shaped and can be attached to one end of the blood vessel wall, as shown in FIG1(d), where 10 is a schematic diagram of the blood vessel plane, and 1 is the arc-shaped substrate of the pressure sensor of the present invention. This arc-shaped substrate structure not only solves the problem that the sensor may damage the blood vessel wall during placement in the blood vessel, but also leaves enough space on one side of the blood vessel for doctors to operate and use, thus reducing the treatment time. At the same time, the arc-shaped pressure sensor of the present invention can be placed in a narrow area of ​​the artery for blood pressure testing due to its small size and arc-shaped substrate structure, so that doctors can quickly diagnose the patient's condition.

[0041] Embodiment 2: Preparation method of arc pressure sensor

[0042] Figure 2 shows the main preparation process of the arc pressure sensor.

[0043] 1. The substrate silicon wafer is photolithographically etched to form a cavity structure, as shown in FIG2(a);

[0044] 2. The substrate silicon wafer is bonded with silicon dioxide and the SOI wafer, a silicon etching mask layer is deposited and the SOI wafer is etched to form a pressure-sensitive membrane and a cavity structure, as shown in FIG2(b);

[0045] 3. Grow silicon dioxide on the front side, pattern it with photolithography, and implant it to form piezoresistive resistors and highly boron-doped lead areas, as shown in Figure 2(c);

[0046] 4. Deposit silicon dioxide on the front side, pattern it with photolithography, and etch it to form contact holes, as shown in Figure 2(d);

[0047] 5. Sputter metal on the front side for photolithography and etching to form an electrode signal interface, as shown in Figure 2(e);

[0048] 6. Glue coating for protection on the front side, photolithography of windows on the back side, and etching of silicon to reduce the thickness to the required value for the sensor, as shown in Figure 2(f);

[0049] 7. Photolithography and etching of silicon to form an arc structure and a convex structure of the pressure sensor, as shown in FIG2(g);

[0050] The thickness of the arc pressure sensor of the present invention is less than 80um, which exceeds the thinning capability of the current process, and therefore cannot be manufactured using the traditional thinning process. The thinning process described in the present invention is to first etch the back of the substrate to the thickness of the sensor using an etching process, and then etch the arc structure and convex structure of the pressure sensor from the front of the substrate using an etching process.

[0051] The protruding structure type 1 is an arbitrary polygon with a narrow chip frame fixed end and a wide sensor end. The schematic diagram and simulation results of the protruding structure being a trapezoid are shown in FIG3(a). The simulation results show that the narrow end of the protruding structure connected to the fixed end of the chip frame is a stress concentration area. The protruding structure type 2 is an arbitrary polygon with a narrow middle part and wide ends. The schematic diagram and simulation results of the protruding structure being a dumbbell are shown in FIG3(b). The simulation results show that the narrow end in the middle of the protruding structure is a stress concentration area, and the equivalent stress value of the protruding structure of type 2 dumbbell shape is greater than the equivalent stress value of the protruding structure of type 1 trapezoid shape, indicating that the protruding structure similar to the dumbbell shape is more likely to break when subjected to external impact. However, the design of the protruding structure must also be determined in combination with the actual manufacturing process of the sensor, to ensure that the sensor does not fall off during the manufacturing process, and to ensure that the sensor is easy to remove from the wafer for subsequent testing after the manufacturing is completed.

[0052] The arc pressure sensor of the present invention has a small width and length, and it is impossible to etch the back side of the substrate of a single sensor using an etching process. Therefore, it is necessary to form a unit structure with multiple sensors and then etch the back side of the substrate. Figure 4 As shown, this example provides a schematic diagram of sensor manufacturing in which three sensors form a unit structure. It should be noted that the sensors included in a unit structure can be designed according to the size of the sensors and the requirements of the corrosion process, and the number of sensors included is ≥2.

[0053] The fixed end 8 of the unit structure outer frame connects all sensors in the unit together through the protruding structure 2, so that the sensor is fixed on the wafer. The etched suspended area 9 surrounds the arc-shaped substrate 1, the outer side of the protruding structure 2 and the inner side of the fixed end 8 of the unit structure outer frame, and is formed by etching the substrate through an etching process, so that the arc-shaped substrates of multiple sensors are separated, which is convenient for subsequent sensor retrieval.

[0054] The above preparation method is used to form the arc substrate structure 1, the protruding structure 2, the pressure-sensitive membrane 3, the cavity structure 4, the piezoresistive resistor 5, the electrode signal interface 6, the high-boron-doped lead area 7, the unit structure outer frame fixed end 8, and the etched suspended area 9 of the pressure sensor. If there is pressure on the pressure-sensitive membrane 3, it will deform, so that the resistance of the piezoresistive resistor 5 changes. The resistance change is connected to the circuit formed by the high-boron-doped lead area 7 and the electrode signal interface 6 to collect and convert the signal, thereby realizing the test of the pressure signal.

[0055] The arc pressure sensor of the present invention is thin, and the traditional mechanical thinning method of the wafer cannot meet the design requirements, so the etching process is used to etch and thin the back of the substrate to the design requirements. The width and length of the single arc pressure sensor are much smaller than the window size that can be etched by the etching process, so a unit structure is formed by connecting multiple arc pressure sensors together through the fixed ends of the unit structure outer frame to meet the window size requirements that can be etched by the etching process.

[0056] The substrate of the arc pressure sensor described in the present invention has an arc shape and needs to be manufactured by an etching process. However, after etching, the back of the arc pressure sensor is suspended in the air and is a fragile silicon wafer. The sensor cannot be separated by scribing. Therefore, the present invention adopts a method of designing a raised structure at the upper and lower ends of the short side of the arc pressure sensor to separate the sensor from the wafer.

[0057] As described above, the arc pressure sensor of the present invention is manufactured by designing a convex structure, forming a sensor unit structure, and adopting a manufacturing method of first back-etching the substrate and then etching the substrate to perform wafer thinning. Compared with traditional pressure sensors, it has the characteristics of small size, strong biocompatibility, and high precision. It can be installed in a medical catheter and attached to the blood vessel wall to measure the blood pressure of the human body. It is easy for doctors to operate and use, and has broad development prospects in the medical field.

[0058] The above content is only one of the embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An arc pressure sensor, comprising an arc substrate, a protruding structure, a pressure-sensitive membrane, a cavity structure, a piezoresistive resistor, an electrode signal interface and a high-boron-doped lead area; the two long sides of the arc substrate are arc-shaped; the cavity structure is located above the arc substrate, the protruding structure is located on the short side of the arc substrate, the pressure-sensitive membrane is connected to the arc substrate through an insulating layer, and is located above the cavity structure, and the piezoresistive resistor, the electrode signal interface and the high-boron-doped lead area are distributed on the pressure-sensitive membrane.

2. The arc pressure sensor according to claim 1, characterized in that: One end of the protruding structure is connected to the fixed end of the unit structure outer frame, and the other end is connected to the short side of the arc-shaped substrate to form a stress concentration area.

3. The arc pressure sensor according to claim 1, characterized in that: The arc angle of the two long sides of the arc-shaped substrate is 28°-30°, and the vertical length is 500um-600um; the shape of the protruding structure can be any polygon with a narrow upper end and a wide lower end, or any polygon with wide ends and a narrow middle.

4. The arc pressure sensor according to claim 1, characterized in that: The two long sides of the arc-shaped substrate have the same center and the same arc.

5. The arc pressure sensor according to claim 1, characterized in that: The difference in arc width between the two long sides of the arc-shaped substrate is between 70um and 80um.

6. The arc pressure sensor according to claim 1, characterized in that: The piezoresistive resistor is axially symmetrically distributed with respect to the center line of the pressure-sensitive membrane, in a vertical or horizontal form.

7. The arc pressure sensor according to claim 1, characterized in that: The electrode signal interfaces are parallelly located at the lower short side of the arc-shaped substrate, and the spacing between the electrode signal interfaces and the lateral spacing between the electrode signal interfaces and the inner and outer arcs of the arc-shaped substrate are the same.

8. The arc pressure sensor according to claim 1, characterized in that: The piezoresistive resistor is connected inside the cavity structure through a high-boron-doped lead wire, and is connected to the electrode signal interface end through a metal outside the cavity structure to form a half-bridge circuit.

9. The arc pressure sensor according to claim 1, characterized in that: The short side of the arc-shaped substrate and the long sides of the inner and outer arcs are perpendicular to each other.

10. A method for preparing an arc pressure sensor, characterized in that: The following steps are involved: (1) Photolithography and etching of the substrate silicon wafer to form a cavity structure: (2) The substrate silicon wafer is bonded with silicon dioxide and the SOI wafer, a silicon etching mask layer is deposited, and the SOI wafer is etched to form a pressure-sensitive membrane; (3) growing silicon dioxide on the front side, patterning it with photolithography, and injecting it to form a piezoresistive resistor; (4) Depositing silicon dioxide on the front side, patterning by photolithography, and etching to form contact holes; (5) Sputtering metal on the front side, photolithography and etching to form an electrode signal interface; (6) Glue coating for protection on the front side, photolithography of windows and etching of silicon thinning on the back side; (7) Photolithography and etching of silicon to form an arc-shaped pressure sensor structure.

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