Subminiature temperature and pressure integrated sensor and preparation method thereof

Abstract

The invention provides a subminiature temperature and pressure integrated sensor and a preparation method thereof. The subminiature temperature and pressure integrated sensor comprises a substrate structure, a pressure signal detection area, a temperature signal detection area, an electrode leading-out area and a metal shading layer. The pressure signal detection area comprises a closed cavity, a thin film structure, a piezoresistor and a pressure concentrated boron lead layer; the temperature signal detection area comprises a temperature sensitive resistor and a temperature concentrated boron lead layer; the electrode leading-out area comprises four electrode signal interfaces. The pressure signal detection area adopts a half-bridge circuit for pressure signal detection, the temperature signal detection area adopts a single temperature-sensitive resistor for temperature signal detection, the tests of the two signals are mutually independent and do not influence each other, and metal shading layers are arranged on the surfaces of the pressure signal detection area and the temperature signal detection area. The sensor is simple in structure, small in size, high in precision, good in shading effect, convenient to install due to the fact that the sensor is packaged into a four-wire mode, safe and reliable in manufacturing material, and capable of being installed in a medical catheter to be placed in a human body to achieve real-time measurement of pressure and temperature.

Description

Technical Field

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

[0002] In recent years, with the continuous maturity of sensor manufacturing technology, small-volume pressure sensors compatible with the human body can be produced. Therefore, human blood pressure can be measured in medical fields such as cardiovascular FFR, intracranial pressure, endoscopy, and ablation examinations.

[0003] During disposable endoscopic examination and treatment, the infusion of liquid usually causes the patient's local blood pressure to rise, and laser treatment causes the patient's local temperature to rise. That is, during the treatment, the doctor needs to obtain the patient's blood pressure and temperature indicators at the same time to facilitate further diagnosis and treatment of the patient's condition. Traditional temperature and pressure integrated sensors mostly use a combination of pressure sensors and temperature sensors to measure temperature and pressure signals. The sensor is large in size, and the manufacturing materials are incompatible with the human body. It cannot be placed in a medical catheter to detect temperature and pressure signals. At the same time, the probe light intensity during endoscopic examination and treatment is high, which has a great impact on the performance of the sensor. Therefore, it is urgent to produce an ultra-small temperature and pressure integrated sensor with small size, strong shading effect, good stability, easy installation, and high precision that can be placed in the human blood vessels to complete the simultaneous measurement of pressure and temperature. Summary of the invention

[0004] The purpose of the present invention is to provide an ultra-small temperature-pressure integrated sensor structure, including a substrate structure, a pressure signal detection area, a temperature signal detection area, an electrode lead-out area, and a metal light-shielding layer. The pressure signal detection area includes a closed cavity, a thin film structure, a varistor, and a pressure concentrated boron lead layer, which is located above the entire structure and is used for measuring and converting pressure signals; the temperature signal detection area includes a temperature-sensitive resistor and a temperature concentrated boron lead layer, which is located below the pressure signal detection area and is used for measuring temperature signals; the pressure concentrated boron lead layer and the temperature concentrated boron lead layer are obtained simultaneously by photolithography patterning and injection; the temperature signal detection area is adjacent to the pressure signal detection area; and the electrode lead-out area is located at the bottom of the sensor structure.

[0005] Furthermore, the varistor and the concentrated boron lead layer are embedded on the thin film structure; the upper surface of the enclosed cavity is connected to the lower surface of the thin film structure; the varistor is located on the upper surface of the enclosed cavity, and is connected to the electrode signal interface by the pressure concentrated boron lead layer to form a half-bridge circuit to detect the pressure signal.

[0006] The lower surface of the metal light shielding layer is connected to the upper surface of the film structure, covering the varistor and the concentrated boron lead layer. The temperature concentrated boron lead layer is located at both ends of the temperature sensitive resistor, and is used to connect the temperature sensitive resistor to the electrode signal interface for temperature signal collection and testing.

[0007] The temperature-sensitive resistor is in the form of a single resistor, and the number of folds can be single or multiple, formed by low-doped boron injection. The temperature-sensitive resistor in the form of multiple folds is also low-doped boron injected at the resistor corner, ensuring the consistency of the temperature coefficient of the temperature-sensitive resistor. The temperature-sensitive resistor is embedded in the substrate structure, and its resistance value does not change with the change of pressure.

[0008] The metal light shielding layer can be distributed in a single area, covering the entire sensor area outside the electrode lead-out area; or the metal light shielding layer can be distributed in multiple areas, covering the varistor, the temperature-sensitive resistor and the concentrated boron lead layer respectively, and the specific area distribution can be designed according to the interference intensity of the light intensity on the sensor performance in the application. The metal light shielding layer is a composite film of multiple layers of metal, formed by a sputtering process, and its material can be a metal material or a combination of metal materials with strong light shielding ability and good biocompatibility.

[0009] Furthermore, the length of the sensor is no greater than 950um, the width is no greater than 400um, and the thickness is no greater than 150um.

[0010] The electrode lead-out area includes four electrode signal interfaces, which are located below the entire structure and are used to lead out the detected pressure signal and temperature signal and connect them to the external circuit. The four electrode signal interfaces are parallel and equidistantly distributed below the ultra-small temperature and pressure integrated sensor structure.

[0011] The sensor has a simple structure, small size, high precision, and good light-shielding effect. It can measure pressure signals and temperature signals at the same time, and the tests of the two signals are independent of each other and do not affect each other. It is packaged in a four-wire form for easy installation. The manufacturing materials are safe and reliable, and it can be placed in the human body to realize real-time measurement of pressure and temperature.

[0012] The ultra-small temperature and pressure integrated sensor has four package leads, which are located above the electrode signal interface and are welded to the four corresponding electrode signal interfaces. The surface of the electrode signal interface and the package lead welding point is covered with protective glue. The length and diameter of the package lead can be customized according to user needs and application scenarios to facilitate the subsequent collection of pressure signals and temperature signals.

[0013] Compared with existing sensors, the ultra-small temperature and pressure integrated sensor of the present invention has the following advantages:

[0014] First, it realizes the real-time test of integrated temperature and pressure signals. The integrated temperature and pressure sensor of the present invention prepares the pressure signal detection area and the temperature signal detection area on a single chip at the same time. The signal detection of the two areas does not affect each other, and the simultaneous measurement of the pressure signal and the temperature signal can be realized. The two areas are adjacent, which ensures that the temperature measured in the temperature signal detection area is the ambient temperature of the pressure signal detection area.

[0015] Second, small size. The temperature and pressure integrated sensor of the present invention has a length of no more than 950um, a width of no more than 400um, and a thickness of no more than 150um, which is much smaller than the volume of a traditional temperature and pressure integrated sensor. Therefore, it can be placed in a medical catheter to measure pressure and temperature simultaneously.

[0016] Third, the shading effect is strong and the stability is good. The temperature and pressure integrated sensor of the present invention has a metal shading layer on the surface of the pressure signal detection area and the temperature signal detection area, which can avoid the influence of changes in external light intensity on the performance of the sensor itself. Therefore, the performance of the sensor is stable and the pressure signal and temperature signal can be detected in a strong light environment.

[0017] Fourth, the package is in a four-wire form, which is easy to install. The pressure signal detection area of ​​the temperature and pressure integrated sensor of the present invention uses a half-bridge method to convert the pressure signal into an electrical signal output, and the temperature signal detection area uses a thermistor to detect the temperature signal. The four electrode signal interfaces are located in parallel at the lower end of the sensor, and the package is simple and convenient for users to use.

[0018] Fifth, it is biocompatible. A concentrated boron lead layer is introduced between the piezoresistors and thermistors in the temperature-pressure integrated sensor of the present invention and the electrode signal interface for connection. The electrode signal interface and the metal light-shielding layer are made of biocompatible metal materials, and the metal glue coating and sealing are performed in the subsequent packaging to avoid direct contact with the human body. Therefore, the temperature-pressure integrated sensor of this structure can be placed in the human body to measure pressure and temperature simultaneously.

[0019] Sixth, high precision. The thickness of the thin film structure in the pressure signal detection area of ​​the temperature-pressure integrated sensor of the present invention is precisely controlled by using SOI silicon wafers, the temperature coefficient of the thermistor in the temperature signal detection area is controlled by an injection process, and the surfaces of the pressure signal detection area and the temperature signal detection area are covered with a metal light-shielding layer, which solves the problem of light intensity factors interfering with sensor performance. Therefore, the manufactured temperature-pressure integrated sensor has high measurement accuracy and good consistency.

[0020] Another object of the present invention is to provide a method for preparing the temperature-pressure integrated sensor, comprising the following steps:

[0021] 1. The substrate silicon wafer is patterned by photolithography to form a cavity;

[0022] 2. The front side of the substrate silicon wafer is bonded to the SOI silicon wafer, and silicon dioxide and silicon nitride are deposited and thinned to form a thin film structure;

[0023] 3. Deposit an oxide layer on the front side, and perform photolithography and patterning to form a varistor, a temperature-sensitive resistor, and a concentrated boron lead layer;

[0024] 4. Deposit an oxide layer on the front side and form contact holes by photolithography;

[0025] 5. Sputter metal on the front side, and pattern the electrode signal interface and metal light shielding layer by photolithography;

[0026] 6. Apply glue to protect the front side and thin the back side to the required thickness;

[0027] 7. Slicing;

[0028] Advantages and positive effects of the present invention:

[0029] Compared with the traditional temperature and pressure integrated sensor, the ultra-small temperature and pressure integrated sensor of the present invention has the following advantages: first, the volume is very small, a single chip is used to prepare the pressure signal detection area and the temperature signal detection area at the same time, and only 4 electrode signal interfaces are used to realize the simultaneous measurement of pressure and temperature. The varistor and the temperature sensitive resistor share the same power signal interface, which saves the volume of the sensor, and is packaged into a four-wire connection for subsequent integration and user use; second, the precision is high, the pressure signal detection area uses a half-bridge circuit to detect the pressure signal, and the temperature signal detection area uses a single temperature sensitive resistor to detect the temperature signal, and the temperature signal detection area is located directly below the pressure signal detection area, the distance is short, and the heat is not lost during the transmission process, which ensures the accuracy of the temperature signal detection; third, the shading effect is strong, and there is a shading metal layer on the surface of the pressure signal detection area and the temperature signal detection area, which has a strong ability to resist light signal interference, so the sensor can detect the pressure signal and the temperature signal in an environment with strong light. At the same time, the ultra-small temperature and pressure integrated sensor of the present invention is made of safe materials, packaged in a four-wire form, can be installed in a medical catheter and put into the human body to collect pressure signals and temperature signals, and has a good development prospect in the medical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Fig. 1 is a schematic diagram of the structure of the ultra-small integrated temperature and pressure sensor of the present invention. Fig. 1(a) is a top view, Fig. 1(b) is a cross-sectional view of the central axis of Fig. 1(a). Fig. 1(c) is a top view of the package lead, and Fig. 1(d) is a three-dimensional stereogram of Fig. 1(c).

[0031] Figure 2(a) to Figure 2(f) This is the main preparation process of the ultra-small temperature and pressure integrated sensor of the present invention.

[0032] In the figure:

[0033] 1-substrate structure, 2-sealed cavity, 3-film structure, 4-varistor, 5-thermistor, 6-concentrated boron lead layer,

[0034] 7-metal shading layer, 8-electrode signal interface, 9-pressure signal detection area, 10-temperature signal detection area,

[0035] 11-Electrode lead area 12-Packaging lead DETAILED DESCRIPTION

[0036] Example 1: Ultra-small integrated temperature and pressure sensor structure

[0037] The structure of the ultra-small temperature-pressure integrated sensor is shown in FIGS. 1( a ) and 1 ( b ), and includes a pressure signal detection area 9 , a temperature signal detection area 10 , and an electrode lead-out area 11 .

[0038] The pressure signal detection area 9 includes a closed cavity 2, a thin film structure 3, a varistor 4, a concentrated boron lead layer 6, and a metal light shielding layer 7, and is located above the entire sensor structure. When the thin film structure 3 is subjected to external pressure, it will deform, causing the resistance of the varistor 4 on it to change, thereby converting the pressure signal to facilitate the subsequent pressure signal collection.

[0039] The varistor 4 and the concentrated boron lead layer 6 are embedded on the thin film structure 3; the upper surface of the enclosed cavity 2 is connected to the lower surface of the thin film structure 3; the lower surface of the metal shading layer 7 is connected to the upper surface of the thin film structure 3, covering the varistor 4 and the concentrated boron lead layer 6, so that they are not disturbed by changes in external light intensity, thereby improving the stability of the ultra-small temperature and pressure integrated sensor.

[0040] The temperature signal detection area 10 includes a temperature-sensitive resistor 5, a concentrated boron lead layer 6, and a metal light-shielding layer 7, and is located below the pressure signal detection area 9, and is used to measure the temperature signal. The temperature signal detection area 10 and the pressure signal detection area 9 are on the same chip, in the same space and adjacent to each other, and there is no heat loss between the two areas during the temperature transfer process. Therefore, the temperature measured by the temperature signal detection area 10 is the actual temperature of the pressure signal detection area 9, which reduces the measurement error of the ultra-small temperature and pressure integrated sensor.

[0041] The temperature-sensitive resistor 5 is in a single-fold or multi-fold form, and is formed by low-doped boron injection. The temperature-sensitive resistor in the multi-fold form is also low-doped boron injected at the resistor corner, which ensures the consistency of the temperature coefficient of the temperature-sensitive resistor 5. The temperature-sensitive resistor 5 is embedded in the substrate structure 1, and the bottom surface of the substrate structure 1 is fixed, so the substrate structure 1 will not be deformed by the external pressure, that is, the temperature-sensitive resistor 5 will not change its resistance due to the change of external pressure, and the resistance change of the temperature-sensitive resistor 5 can only be caused by the temperature change, which avoids the influence of the pressure signal on the temperature measured by the temperature-sensitive resistor 5, and improves the measurement accuracy of the ultra-small temperature-pressure integrated sensor.

[0042] The concentrated boron lead layer 6 is located at both ends of the temperature-sensitive resistor 5, and is used to connect the temperature-sensitive resistor 5 to the electrode signal interface 8 for temperature signal collection and testing. The lower surface of the metal light-shielding layer 7 is connected to the upper surface of the substrate structure 1, and is located above the temperature-sensitive resistor 5 and the concentrated boron lead layer 6, ensuring that the temperature-sensitive resistor 5 is not interfered by light intensity factors when measuring temperature.

[0043] The electrode lead-out area 11 includes four electrode signal interfaces 8, which are parallel and equidistantly distributed below the ultra-small temperature-pressure integrated sensor structure, and are used to lead the detected pressure signal and temperature signal to connect with the external circuit. The varistor 4 and the temperature-sensitive resistor 5 share one electrode signal interface 8 for power supply, which saves the width of the sensor. Only four electrode signal interfaces 8 are used to complete the testing and collection of pressure signals and temperature signals, which is convenient for subsequent packaging and user use.

[0044] Figure 1 (c) and (d) show schematic diagrams of package leads of the ultra-small temperature and pressure integrated sensor. There are four package leads 12, which are located above the electrode signal interface 8 and are welded to the four electrode signal interfaces 8 respectively. The length and diameter of the package leads can be customized according to user needs and application scenarios to facilitate the subsequent collection of pressure signals and temperature signals.

[0045] Embodiment 2: A method for preparing an ultra-small temperature and pressure integrated sensor, the specific steps are as follows:

[0046] 1. Photolithography and etching of the substrate silicon wafer to produce the cavity, as shown in Figure 2(a);

[0047] 2. The front side of the substrate silicon wafer is bonded to the SOI silicon wafer, silicon dioxide and silicon nitride are deposited on both sides, the silicon layer is thinned and removed, and the buried oxide layer is etched to form a thin film structure and a closed cavity, as shown in Figure 2(b);

[0048] 3. Deposit silicon dioxide on the front side, and perform photolithography and patterning to form varistors, temperature-sensitive resistors, and concentrated boron lead layers, as shown in Figure 2(c);

[0049] 4. Deposit silicon dioxide on the front side and form contact lead holes by photolithography, as shown in Figure 2(d);

[0050] 5. Sputter metal on the front side, and photoetch to form the electrode signal interface and metal light shielding layer, as shown in Figure 2(e);

[0051] 6. Apply glue to protect the front side and thin the back side substrate to the required thickness of the sensor, as shown in Figure 2(f);

[0052] 7. Slicing;

[0053] The above method is used to prepare an ultra-small temperature and pressure integrated sensor, and its structure is divided into three parts from top to bottom, namely, the pressure signal detection area, the temperature signal detection area and the electrode lead-out area. The three structures are formed by a single chip and do not need to be assembled and connected. The pressure signal detection area is mainly used for the conversion and testing of the pressure signal; the temperature signal detection area is used for the testing of the temperature signal; the electrode lead-out area leads the signals collected by the pressure signal detection area and the temperature signal detection area and connects them to the external circuit. When the external pressure acts on the upper surface of the film structure 3 of the pressure signal detection area 9, the film structure 3 will deform, and the varistor 4 will transmit the pressure signal to the external detection circuit through the concentrated boron lead layer 6 and the electrode signal interface 8 after the signal conversion. At the same time, the temperature-sensitive resistor 5 in the temperature signal detection area transmits the collected temperature signal to the external detection circuit through the concentrated boron lead layer 6 and the electrode signal interface 8. The pressure signal detection area and the temperature signal detection area do not affect each other during testing. Therefore, the ultra-small temperature and pressure integrated sensor of the present invention can realize the simultaneous measurement of temperature signal and pressure signal.

[0054] The ultra-small integrated temperature and pressure sensor proposed in the present invention is a sensor in which a pressure signal detection area, a temperature signal detection area and an electrode lead-out area are respectively manufactured on the same chip. When the sensor is subjected to external pressure, the thin film structure in the pressure signal detection area will be deformed, causing the resistance of the varistor to change and be connected to the detection circuit through a concentrated boron lead layer and an electrode signal interface for pressure signal collection and testing. The temperature-sensitive resistor in the temperature signal detection area is manufactured on a substrate structure, and the substrate structure will not be deformed even if subjected to external pressure, so the resistance value of the temperature-sensitive resistor will not change with changes in pressure. However, when the ambient temperature of the sensor changes, the resistance value of the temperature-sensitive resistor in the temperature signal detection area will change, and will be connected to the detection circuit through a concentrated boron lead layer and an electrode signal interface for temperature signal collection and testing.

[0055] The electrode lead-out area is located at the bottom of the sensor, which is convenient for subsequent lead welding and installation. The four electrode signal interfaces are equidistantly distributed in parallel in the width direction of the sensor, one of which is the power common end of the pressure signal detection area and the temperature signal detection area, and the other three are the positive signal output, negative signal output and output end of the pressure signal detection area and the temperature signal detection area. Only four electrode signal interfaces are used to complete the collection of pressure signals and temperature signals, which reduces the width of the sensor and increases the number of sensors that can be produced on each wafer. At the same time, a metal shading layer is made on the pressure signal detection area and the temperature signal detection area to prevent the external light intensity from interfering with the collection of the pressure signal and temperature signal of the sensor.

[0056] The present invention also describes the packaging lead form of the ultra-small temperature-pressure integrated sensor, which can be customized according to the application of the sensor, so as to facilitate real-time measurement of pressure signals and temperature signals when placed in a medical catheter.

[0057] Therefore, the ultra-small temperature-pressure integrated sensor proposed in the present invention can realize the testing of pressure signals and temperature signals without assembly. At the same time, the two signal acquisitions are independent of each other and do not affect each other. The length of the sensor is not more than 950um, the width is not more than 400um, and the thickness is not more than 150um, which is much smaller than the volume of the traditional temperature-pressure integrated sensor. At the same time, it also has the characteristics of strong shading effect, good stability, easy installation, high precision, strong biocompatibility and low cost, and has broad application 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 ultra-small temperature and pressure integrated sensor, comprising a substrate structure, a pressure signal detection area, a temperature signal detection area, an electrode lead-out area, and a metal shading layer; the pressure signal detection area comprises a closed cavity, a thin film structure, a varistor, and a pressure concentrated boron lead layer, and is located above the entire sensor structure; the temperature signal detection area comprises a thermistor and a temperature concentrated boron lead layer, and is located below the pressure signal detection area and adjacent to the pressure signal detection area; the electrode lead-out area is located at the bottom of the sensor structure; the metal shading layer covers the varistor, the pressure concentrated boron lead layer, the thermistor, and the temperature concentrated boron lead layer.

2. The ultra-small integrated temperature and pressure sensor according to claim 1, characterized in that: The varistor and the pressure concentrated boron lead layer are embedded on the thin film structure; the upper surface of the closed cavity is connected to the lower surface of the thin film structure; the temperature concentrated boron lead layer is located at both ends of the temperature sensitive resistor, and is used to connect the temperature sensitive resistor to the electrode signal interface for facilitating temperature signal collection and testing.

3. The ultra-small integrated temperature and pressure sensor according to claim 1, characterized in that: The electrode lead-out area includes four electrode signal interfaces, one of which is the common power supply end of the pressure signal detection area and the temperature signal detection area, and the remaining three electrode signal interfaces are the signal output positive, signal output negative and output ends of the pressure signal detection area and the temperature signal detection area, respectively.

4. The ultra-small integrated temperature and pressure sensor according to claim 3, characterized in that: The four electrode signal interfaces are distributed in parallel and equidistantly below the ultra-small temperature and pressure integrated sensor structure.

5. The ultra-small integrated temperature and pressure sensor according to claim 1, characterized in that: The temperature-sensitive resistor is in the form of a single resistor, and the number of folds can be single or multiple, formed by low-doped boron injection. The multi-fold temperature-sensitive resistor is also low-doped boron injected at the resistor corners, ensuring the consistency of the temperature coefficient of the temperature-sensitive resistor; the temperature-sensitive resistor is embedded in the substrate structure, and its resistance value does not change with changes in pressure.

6. The ultra-small integrated temperature and pressure sensor according to claim 1, characterized in that: The metal shading layer can be distributed in a single area to fully cover the sensor area outside the electrode lead-out area; or the metal shading layer can be distributed in multiple areas to cover the varistor, thermistor, pressure and temperature concentrated boron lead layers respectively.

7. The ultra-small integrated temperature and pressure sensor according to claim 1, characterized in that: The metal light-shielding layer is a composite film of multiple layers of metals, which is formed by a sputtering process. The material of the metal light-shielding layer can be a metal material or a combination of metal materials with strong light-shielding ability and good biocompatibility.

8. The ultra-small integrated temperature and pressure sensor according to claim 1, characterized in that: The length of the ultra-small temperature and pressure integrated sensor is no more than 950um, the width is no more than 400um, and the thickness is no more than 150um.

9. The ultra-small integrated temperature and pressure sensor according to claim 1, characterized in that: The varistor is located on the upper surface of the closed cavity and is connected to the electrode signal interface via a pressure concentrated boron lead layer to form a half-bridge circuit to detect the pressure signal.

10. A method for preparing an ultra-small temperature and pressure integrated sensor, characterized in that: The following steps are involved: (1) Photolithography of the substrate silicon wafer to form a cavity; (2) The front side of the substrate silicon wafer is bonded to the SOI silicon wafer, and silicon dioxide and silicon nitride are deposited and thinned to form a thin film structure; (3) Depositing an oxide layer on the front side, and photolithography and patterning and implanting to form a varistor, a temperature-sensitive resistor, and a concentrated boron lead layer; (4) depositing an oxide layer on the front side and patterning it by photolithography to form contact holes; (5) Sputtering metal on the front side and patterning by photolithography to form an electrode signal interface and a metal light shielding layer; (6) Apply glue to protect the front side and thin the back side to the required thickness; (7) Slicing.

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