CN111239208A - Constant temperature structure for high-performance humidity detection device and preparation method - Google Patents

Abstract

The invention discloses a constant temperature structure for a high-performance humidity detection device and a preparation method. It comprises a top layer Al ₃ N ₄ substrate (1), a thin film thermistor (2) is integrated on the upper surface of the top layer Al ₃ N ₄ substrate (1), and a TEC unit is integrated on the lower surface of the top layer Al ₃ N ₄ substrate (1) (3), the bottom surface of the TEC unit (3) is integrated with a bottom layer Al ₃ N ₄ substrate (4); the upper surface of the thin film thermistor (2) is integrated with an insulating medium layer (5), the insulating medium layer (5) ) a sensor signal processing chip (7) is pasted on the upper surface via a metallized layer (6). The invention can reduce the temperature drift range of the relevant performance parameter indexes of the components inside the humidity sensor device, avoid temperature sensor devices such as externally attached thermal resistance, save the assembly space of the externally attached device, and be more conducive to the miniaturization of the assembly .

Description

Constant temperature structure and preparation method for high-performance humidity detection device

technical field

The invention relates to the technical field of sensors, in particular to a constant temperature structure and a preparation method for a high-performance humidity detection device.

Background technique

The structure of the traditional humidity detection device is mainly to directly mount the separate components such as the sensing signal processing chip, the humidity sensitive resistor, the metal welding area, and other active/passive components on the aluminum nitride ceramic substrate, and then perform circuit welding. , complete the circuit connection, its structure is shown in Figure 1. However, the humidity detection device of this structure has the following problems: when the whole device works in the natural environment, with the change of temperature, the electrical properties and physical properties of each component will change to a certain extent, thus affecting the detection accuracy of humidity. At the same time, when some limiting devices are used in highly reliable environments or some special fields such as aerospace, aviation, ships, precision instruments, geological exploration, oil exploration, other field operations, communications, industrial control and other environments with complex temperature changes, in order to To ensure the accuracy of the detection, it is necessary to add some bulky and expensive ambient temperature control devices.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a constant temperature structure and a preparation method for a high-performance humidity detection device. The invention can reduce the temperature drift range of the relevant performance parameter indexes of the components inside the humidity sensor device, avoid temperature sensor devices such as externally attached thermal resistance, save the assembly space of the externally attached device, and be more conducive to the miniaturization of the assembly .

Technical scheme of the present invention: a constant temperature structure for a high-performance humidity detection device, comprising a top layer Al3N4 substrate, a thin film thermistor integrated on the upper surface of the top layer Al3N4 substrate, a TEC unit integrated on the lower surface of the top layer Al3N4 substrate, and a lower surface of the TEC unit The bottom layer Al3N4 substrate is integrated; the upper surface of the thin film thermistor is integrated with an insulating medium layer, and the upper surface of the insulating medium layer is pasted with a sensing signal processing chip through a metallized layer.

In the aforementioned constant temperature structure for a high-performance humidity detection device, a conduction band and a bonding region composed of Ni-Cr-Cu-Ni-Cr-Au composite metal films are also integrated on the upper surface of the top layer Al3N4 substrate.

In the aforementioned constant temperature structure for a high-performance humidity detection device, the upper and lower surfaces of the TEC unit are respectively connected to the top and bottom Al3N4 substrates through Ni-Cr-Cu-Ni-Cr-Au composite metal films.

In the aforementioned constant temperature structure for a high-performance humidity detection device, the total thickness of the composite metal film is 1-2 μm, and the thickness of the gold layer is 0.3-0.8 μm.

In the aforementioned constant temperature structure for a high-performance humidity detection device, the insulating medium layer is an insulating medium layer composed of Al2O3.

In the above-mentioned constant temperature structure for a high-performance humidity detection device, the TEC unit is composed of a PN-type semiconductor wafer whose front and back sides have been gold metallized and fully alloyed.

In the aforementioned constant temperature structure for a high-performance humidity detection device, the thickness of the semiconductor wafer is 0.3-0.8 mm, and the thickness of the gold metallization layer is 1-2 μm.

The preparation method of the above-mentioned high-performance humidity detection device with a constant temperature structure is prepared according to the following steps:

a. The circuit diagram I of the integrated connection TEC unit is etched on the lower surface of the top Al3N4 substrate;

b. Use a selective metal mask for thin film sputtering to form a thin film thermistor on the upper surface of the top Al3N4 substrate;

c. Use a selective metal mask for thin film sputtering, form an insulating medium layer on the surface of the thin film thermistor, and then form a metallization layer required for pasting the sensor signal processing chip on the surface of the insulating medium layer;

d. The circuit diagram II of the integrated and connected TEC unit is etched on the top surface of the bottom Al3N4 substrate;

e. Align and connect the upper and lower surfaces of the TEC unit with the circuit diagrams I and II according to the specified positions, and then use the fixing fixture for positioning and fixing, and then perform alloy welding of the TEC unit, so that the top layer Al3N4 substrate, the TEC unit, and the bottom layer Al3N4 substrate are formed. integrated substrate;

f. Solder the sensor signal processing chip to the metallization layer of the integrated substrate.

In the aforementioned preparation method of a constant temperature structure for a high-performance humidity detection device, in the steps a and d, the etching of the circuit diagram includes the following steps:

a1. A layer of Ni-Cr-Cu-Ni-Cr-Au composite metal film is formed on the surface of the Al3N4 substrate by thin film sputtering and photolithography;

a2. Etch the circuit diagram on the composite metal film.

In the preparation method of the above-mentioned constant temperature structure for high-performance humidity detection device, in the described step e, the TEC unit is prepared by the following method:

e1. A ternary solid solution crystal material based on bismuth telluride is used, wherein the P-type semiconductor material is: Bi2Te3-Sb2Te3, and the N-type semiconductor material is: Bi2Te3-Bi2Se3;

e2. Gold metallization is performed on the front and back of the wafer, and sufficient alloying is performed;

e3. On the dicing machine, dicing according to the specified size, separating the required N-type and P-type semiconductor crystal grains, to obtain alloy sheets, that is, to obtain the TEC unit.

Beneficial effect: compared with the prior art, when the present invention is applied to a humidity sensitive device, the working environment temperature of the application circuit can be set and adjusted as required, so that there is no need to add a bulky and expensive environment temperature control device when the device is applied. Used together, the equipment cost is reduced and the equipment structure is optimized. At the same time, the invention adopts the integrated technical structure of the thin film thermistor and the sensing signal processing chip, which avoids the temperature sensing devices such as externally attached thermal resistors, saves the assembly space of the externally attached devices, and makes the device structure simpler and more compact. It is more conducive to the miniaturization of equipment.

In the present invention, the integrated technical structure of the thin film thermistor and the sensing signal processing chip is adopted to realize the gapless contact between the thin film thermistor and the sensing signal processing chip on the largest contact surface, and the contact is between atoms; this structure , which can transmit the heat of the sensor signal processing chip to the thin film thermistor to the greatest extent and fastest. After signal processing, the signal is quickly transmitted to the TEC unit (ie semiconductor thermoelectric cooling unit) to control the current of the TEC unit. direction, so as to control the frequency of heating or cooling, and then achieve the purpose of temperature control; through the structure of zero-distance contact between temperature sensing devices such as thin film thermistors and the sensing signal processing chip in the direction of a large area, when the temperature control device When the external working environment temperature changes, the change range of the ambient working temperature can be controlled within ±3°C of the set temperature, thereby reducing the temperature drift range of the relevant performance parameters of each component inside the humidity sensor and improving the detection accuracy.

In the present invention, each layer structure is connected by the Ni-Cr-Cu-Ni-Cr-Au composite metal film. Since the composite metal film of this structure is excellent in electrical conductivity, thermal conductivity and solderability, it is It can not only effectively ensure the fast transmission and precise processing of signals, but also facilitate the welding of various components, reduce the manufacturing difficulty of component integration, and optimize the manufacturing process; and the inventor found in the research that when the total thickness of the composite metal film is When the thickness of the gold layer is 1 to 2 μm (optimally 1.5 μm), and the thickness of the gold layer is 0.3 to 0.8 μm (optimally 0.5 μm), its electrical conductivity, thermal conductivity and welding performance are the best. At the same time, the inventor also found that: when the thickness of the semiconductor wafer in the TEC unit is 0.3-0.8mm (optimally 0.5mm), and the thickness of the gold metallization layer is 1-2μm (optimally 1.5μm), the TEC unit It showed the best temperature control performance.

The present invention is mainly used for humidity sensitive devices in the fields of precise measurement and precise control. The humidity sensing device made by the invention can quickly transmit, precisely process and amplify the sensor signal. At the same time, the temperature difference ΔT between the cold end and the hot end of the humidity sensor can reach more than 70°C at room temperature, and the typical working environment temperature is -40°C to 85°C, which can fully meet the requirements of high-end technical fields such as aerospace, aviation, ships, and precision instruments. application requirements.

Description of drawings

Fig. 1 is the structure diagram of the traditional humidity sensor;

FIG. 2 is a structural diagram of a humidity sensitive device made by the present invention.

Reference numerals: 1- Top layer Al ₃ N ₄ substrate, 2- Thin film thermistor, 3- TEC unit, 4- Bottom Al ₃ N ₄ substrate, 5- Insulating dielectric layer, 6- Metallization layer, 7- Sensing signal processing chip, 8-humidity resistance, 9-metal bonding area, 10-device base.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but not as a basis for limiting the present invention.

Example. A constant temperature structure for a high-performance humidity detection device is composed as shown in Figure 2, including a top layer Al ₃ N ₄ substrate 1, a thin film thermistor 2 integrated on the upper surface of the top layer Al ₃ N 4 substrate 1, and a top layer Al ₃ N ₄ substrate 1. _4. The lower surface of the substrate 1 is integrated with a TEC unit 3, and the lower surface of the TEC unit 3 is integrated with a bottom layer Al ₃ N ₄ substrate 4; A sensor signal processing chip 7 is pasted on the surface through the metallization layer 6 .

In Figure 2, the black square bars on both sides of the TEC unit 3 are its pins.

A conduction band and a bonding region composed of Ni-Cr-Cu-Ni-Cr-Au composite metal films are also integrated on the upper surface of the aforementioned top layer Al ₃ N ₄ substrate 1 .

The upper and lower surfaces of the aforementioned TEC unit 3 are respectively connected to the top and bottom Al ₃ N ₄ substrates through Ni-Cr-Cu-Ni-Cr-Au composite metal films.

The total thickness of the aforementioned composite metal film is 1-2 μm, wherein the thickness of the gold layer is 0.3-0.8 μm.

The aforementioned insulating dielectric layer 5 is an insulating dielectric layer composed of Al ₂ O ₃ .

The aforementioned TEC unit 3 is composed of a PN-type semiconductor wafer whose front and back sides have been gold metallized and fully alloyed.

The thickness of the aforementioned semiconductor wafer is 0.3-0.8 mm, and the thickness of the gold metallization layer is 1-2 μm.

The preparation method of the above-mentioned high-performance humidity detection device with a constant temperature structure is prepared according to the following steps:

a. The circuit diagram I of the integrated connection TEC unit 3 is etched on the lower surface of the top layer Al ₃ N ₄ substrate 1;

b. Use selective metal mask to carry out thin film sputtering, and form thin film thermistor 2 (that is, platinum thin film thermistor) on the upper surface of the top layer Al ₃ N ₄ substrate 1;

c. Use a selective metal mask to perform thin film sputtering, form an insulating medium layer 5 on the surface of the thin film thermistor 2, and then form a metallization layer 6 on the surface of the insulating medium layer 5 required to paste the sensing signal processing chip 7;

d. The circuit diagram II of the integrated connection TEC unit 3 is etched on the upper surface of the bottom Al ₃ N ₄ substrate 4;

e. Align and connect the upper and lower surfaces of the TEC unit 3 with the circuit diagrams I and II according to the specified positions, and then use the fixing fixture for positioning and fixing, and then perform alloy welding of the TEC unit 3, so that the top layer Al ₃ N ₄ substrate 1, TEC unit 3. The bottom layer Al ₃ N ₄ substrate 4 constitutes an integrated substrate;

f. Solder the sensor signal processing chip 7 to the metallization layer 6 of the integrated substrate.

In the aforementioned steps a, d, the etching of the circuit diagram includes the following steps:

a1. A layer of Ni-Cr-Cu-Ni-Cr-Au composite metal film is formed on the surface of the Al ₃ N ₄ substrate by thin film sputtering and photolithography;

a2. Etch the circuit diagram on the composite metal film.

In the aforementioned step e, the TEC unit 3 is prepared as follows:

e1. A ternary solid solution crystal material based on bismuth telluride is used, wherein the P-type semiconductor material is: Bi ₂ Te ₃ -Sb ₂ Te ₃ , and the N-type semiconductor material is: Bi ₂ Te ₃ -Bi ₂ Se ₃ ;

e2. Gold metallization is performed on the front and back of the wafer, and sufficient alloying is performed;

e3. On the dicing machine, perform dicing according to the specified size, and separate the required N-type and P-type semiconductor crystal grains to obtain alloy sheets, that is, the TEC unit 3 is obtained.

When using the present invention to make a humidity sensitive device, the structure of the humidity sensitive device is shown in FIG. 2, and the thin film structure of the humidity sensitive resistor 8 (that is, the nickel-chromium thin film resistor) film is directly sputtered and photoetched on the thin film thermistor 2. The upper surface of the top layer Al ₃ N ₄ substrate 1, in addition, other separate components such as active or passive components are directly mounted on the substrate, and finally, circuit welding is performed to complete the entire electrical connection to form a high-performance humidity sensor device; when the humidity sensitive device is used, it can be soldered on the device base 10 using a conventional soldering process.

The temperature of the TEC unit 3 is controlled according to the refrigeration principle of the semiconductor PN junction - the Peltier effect. , quickly transmit the signal to the TEC unit 3 to control the current direction of the TEC unit 3: when the PN junction in the TEC unit 3 is reverse biased (that is, the N-type semiconductor lead terminal is connected to the positive power supply, and the P-type semiconductor is connected to the negative power supply), The hybrid integration surface is cooled, and the internal operating temperature of the device decreases; when the PN junction is forward-biased (that is, the N-type semiconductor terminal is connected to the negative power supply, and the P-type semiconductor is connected to the positive power supply), the hybrid integration surface is heated, and the internal operating temperature of the device rises. In this way, the frequency of heating or cooling is controlled, so as to achieve the purpose of temperature control.

Claims (10)

1. a thermostatic structure for a high-performance humidity detection device, characterized in that: it comprises a top layer Al ₃ N ₄ substrate (1), and the upper surface of the top layer Al ₃ N ₄ substrate (1) is integrated with a thin film thermistor (2) , a TEC unit (3) is integrated on the lower surface of the top layer Al ₃ N ₄ substrate (1), and a bottom layer Al ₃ N ₄ substrate (4) is integrated on the lower surface of the TEC unit (3); the thin film thermistor (2) ) an insulating medium layer (5) is integrated on the upper surface, and a sensing signal processing chip (7) is pasted on the upper surface of the insulating medium layer (5) via a metallized layer (6). 2. The constant temperature structure for a high-performance humidity detection device according to claim 1, characterized in that: the upper surface of the top layer Al ₃ N ₄ substrate (1) is further integrated with Ni-Cr-Cu-Ni-Cr -Conduction band and bonding area composed of Au composite metal film. 3. The constant temperature structure for a high-performance humidity detection device according to claim 1, characterized in that: the upper and lower surfaces of the TEC unit (3) are respectively treated with Ni-Cr-Cu-Ni-Cr-Au composite metal film and top, Bottom _Al3N4 substrate connection _. 4 . The constant temperature structure for a high-performance humidity detection device according to claim 2 or 3 , wherein the total thickness of the composite metal film is 1-2 μm, and the thickness of the gold layer is 0.3-0.8 μm. 5 . 5 . The constant temperature structure for a high-performance humidity detection device according to claim 1 , wherein the insulating medium layer ( 5 ) is an insulating medium layer composed of Al ₂ O ₃ . 6 . 6 . The constant temperature structure for a high-performance humidity detection device according to claim 1 , wherein the TEC unit ( 3 ) is composed of a PN-type semiconductor wafer whose front and back sides have been gold metallized and fully alloyed. 7 . 7 . The constant temperature structure for a high-performance humidity detection device according to claim 6 , wherein the thickness of the semiconductor wafer is 0.3-0.8 mm, and the thickness of the gold metallization layer is 1-2 μm. 8 . 8. A preparation method of a constant temperature structure for a high-performance humidity detection device as claimed in any one of claims 1-7, characterized in that: prepare according to the following steps: a. The circuit diagram I of the integrated connection TEC unit (3) is etched on the lower surface of the top layer Al ₃ N ₄ substrate (1); b. Use selective metal mask for thin film sputtering to form thin film thermistor (2) on the upper surface of the top layer Al ₃ N ₄ substrate (1); c. Use a selective metal mask for thin film sputtering, form an insulating medium layer (5) on the surface of the thin film thermistor (2), and then form a sticking sensor signal processing chip (7) on the surface of the insulating medium layer (5) the required metallization layer (6); d. The circuit diagram II of the integrated connection TEC unit (3) is etched on the upper surface of the bottom Al ₃ N ₄ substrate (4); e. Align and connect the upper and lower surfaces of the TEC unit (3) with the circuit diagrams I and II respectively according to the specified positions, and then use the fixing fixture for positioning and fixing, and then perform alloy welding of the TEC unit (3), so that the top layer Al ₃ N ₄ substrate (1), the TEC unit (3), and the bottom layer Al ₃ N ₄ substrate (4) constitute an integrated substrate; f. Solder the sensor signal processing chip (7) to the metallization layer (6) of the integrated substrate. 9. The method for preparing a constant temperature structure for a high-performance humidity detection device according to claim 8, wherein in the steps a and d, the etching of the circuit diagram comprises the following steps: a1. A layer of Ni-Cr-Cu-Ni-Cr-Au composite metal film is formed on the surface of the Al ₃ N ₄ substrate by thin film sputtering and photolithography; a2. Etch the circuit diagram on the composite metal film. 10. The method for preparing a constant temperature structure for a high-performance humidity detection device according to claim 8, characterized in that: in the step e, the TEC unit (3) is prepared by the following method: e1. A ternary solid solution crystal material based on bismuth telluride is used, wherein the P-type semiconductor material is: Bi ₂ Te ₃ -Sb ₂ Te ₃ , and the N-type semiconductor material is: Bi ₂ Te ₃ -Bi ₂ Se ₃ ; e2. Gold metallization is performed on the front and back of the wafer, and sufficient alloying is performed; e3. On a dicing machine, perform dicing according to a specified size, and separate the required N-type and P-type semiconductor crystal grains to obtain alloy sheets, that is, to obtain the TEC unit (3).

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