阅读说明：本技术 热敏电阻及基于该热敏电阻的微辐射热计 (Thermistor and microbolometer based on thermistor ) 是由 严振洪 谢辉煌 吕胤嘉 于 2020-06-05 设计创作，主要内容包括：本发明公开了一种热敏电阻及基于该热敏电阻的微辐射热计。所述的热敏电阻,是在基板上依序形成第一氮化铝薄膜、氧化钒薄膜及第二氮化铝薄膜的三层堆栈结构,底层的第一氮化铝薄膜具有高导热系数及优良的均温性,并可为氧化钒薄膜的成长基础,中间层的氧化钒薄膜作为热敏反应层,具有较高的温度电阻系数、较快的反应速度、较低的制程温度和提供广域的温度量测范围,顶层的第二氮化铝薄膜作为钝化层,并提供优良的导热性、均温性及保护作用；进一步地,将此三层堆栈结构制作于微辐射热计的微浮桥结构中,可提升温度均匀性和增加10～17μm远红外波长吸收效率。(The invention discloses a thermistor and a microbolometer based on the thermistor. The thermistor is characterized in that a three-layer stack structure of a first aluminum nitride film, a vanadium oxide film and a second aluminum nitride film is sequentially formed on a substrate, the first aluminum nitride film at the bottom layer has high thermal conductivity and excellent temperature uniformity and can be used as a growth base of the vanadium oxide film, the vanadium oxide film at the middle layer is used as a thermosensitive reaction layer and has higher temperature resistivity, higher reaction speed, lower process temperature and wide temperature measurement range, and the second aluminum nitride film at the top layer is used as a passivation layer and provides excellent thermal conductivity, temperature uniformity and protection; furthermore, the three-layer stack structure is manufactured in a micro-floating bridge structure of the microbolometer, so that the temperature uniformity can be improved, and the far infrared wavelength absorption efficiency of 10-17 mu m can be increased.)

1. A thermistor, comprising:

a substrate;

a first aluminum nitride film disposed over the substrate;

a vanadium oxide film disposed on the first aluminum nitride film; and

and the second aluminum nitride film is arranged on the vanadium oxide film.

2. A thermistor according to claim 1, characterized in that the substrate is one of monocrystalline silicon, monocrystalline germanium, titanium dioxide, silicon nitride, titanium nitride, glass, sapphire and elemental metal.

3. The thermistor according to claim 1, characterized in that the vanadium oxide film has the formula VOx, where x is 1.0 to 2.5.

4. A thermistor according to claim 1, characterized in that the vanadium oxide film is a pure monoclinic or tetragonal phase.

5. The thermistor according to claim 1, characterized in that the thickness of the vanadium oxide film is 100 to 300 nm.

6. The thermistor according to claim 1, wherein the first aluminum nitride film and the second aluminum nitride film have a thickness of 200 to 500 nm.

7. A microbolometer, comprising a microbridge structure, an air gap layer being formed between the microbridge structure and a substrate, the microbridge structure comprising:

a first aluminum nitride film disposed over the substrate;

a vanadium oxide film disposed on the first aluminum nitride film; and

and the second aluminum nitride film is arranged on the vanadium oxide film.

8. The microbolometer of claim 7, wherein the substrate is one of single crystal silicon, single crystal germanium, titanium dioxide, silicon nitride, titanium nitride, glass, sapphire, and elemental metal.

9. The microbolometer of claim 7, wherein the vanadium oxide film has a formula VOx, wherein x is 1.0 to 2.5.

10. The microbolometer of claim 7, wherein the vanadium oxide film is a pure phase of a monoclinic or tetragonal phase.

11. The microbolometer of claim 7, wherein the vanadium oxide film has a thickness of 100 to 300 nm.

12. The microbolometer of claim 7, wherein the first aluminum nitride film and the second aluminum nitride film have a thickness of 200 to 500 nm.

Technical Field

The invention belongs to the technical field of semiconductors, and particularly relates to a thermistor and a microbolometer based on the thermistor.

Background

A thermistor (thermistor) is a resistor body extremely sensitive to temperature change, and has been widely used for temperature measurement, temperature control, temperature compensation, air pressure measurement, weather detection, overload protection, and the like by utilizing its sensitivity to temperature.

A Microbolometer (Microbolometer) based on a thermistor is an infrared detector which has been developed rapidly in recent years, and is mainly implemented by a micro-floating bridge structure, and the basic principle is that a light absorption layer of the micro-floating bridge structure absorbs external infrared radiation energy to cause a temperature change, so that a resistance value of the thermistor changes, and the required information is obtained by detecting the change. In the micro-floating bridge structure, the thermistor as a core has a great influence on the sensitivity of the microbolometer. The most commonly used thermistor materials are polysilicon films or transition metal oxide films. Among them, vanadium oxide is one of the transition metal oxides, which has the advantages of higher temperature resistivity, faster reaction speed, lower process temperature and wide temperature measurement range, and can meet the requirement of high-performance microbolometer. However, the growth conditions of the vanadium oxide film are not easy to control, and the problems of unstable output signals caused by poor resistance uniformity and thermal stability often occur, so that the product performance is influenced, and the development of a high-performance microbolometer is not facilitated.

Accordingly, there is room for improvement and development in the above-mentioned prior art.

Disclosure of Invention

In view of the above, the main objective of the present invention is to provide a thermistor and a microbolometer based on the thermistor, in which a first aluminum nitride film, a vanadium oxide film and a second aluminum nitride film are sequentially stacked on a substrate, and the aluminum nitride has excellent thermal conductivity, so as to effectively improve the uniformity of the thermistor and the poor thermal stability, thereby meeting the requirement of a high-performance microbolometer.

In order to achieve the above object, the present invention provides a thermistor, which comprises a substrate, a first aluminum nitride film, a vanadium oxide film and a second aluminum nitride film stacked in sequence. Wherein the first aluminum nitride film has high thermal conductivity and can be the growth base of the vanadium oxide film; the vanadium oxide film is used as a thermosensitive reaction layer, and has higher temperature resistivity, faster reaction speed, lower processing temperature and wide temperature measurement range; the second aluminum nitride film is used as a passivation layer and provides thermal conductivity, temperature uniformity and protection.

In addition, the invention also provides a microbolometer which comprises a micro-floating bridge structure, wherein the micro-floating bridge structure is positioned above a substrate, an air gap layer is formed between the micro-floating bridge structure and the substrate, and the micro-floating bridge structure sequentially comprises a second aluminum nitride film, a vanadium oxide film and a first aluminum nitride film from top to bottom. The first aluminum nitride film is used as a supporting layer of the micro-floating bridge structure, has the characteristics of capability of bearing the stress of about 440MPa and good stability, and can be the growth basis of the vanadium oxide film. In addition, the composite material also has high heat conductivity coefficient, and can improve the temperature uniformity of the micro-floating bridge structure; the vanadium oxide film is used as a thermosensitive reaction layer, and has higher temperature resistivity, faster reaction speed, lower processing temperature and wide temperature measurement range; the second aluminum nitride film is used as a passivation layer, provides heat conductivity and temperature uniformity, and can absorb infrared energy with specific wavelength.

Compared with the prior art, the vanadium oxide film is arranged between the first aluminum nitride film and the second aluminum nitride film, the aluminum nitride film has high heat conductivity coefficient and high heat transfer efficiency, can provide better temperature uniformity and is beneficial to improving the resistance uniformity and the thermal stability of the thermistor, and the aluminum nitride film can simultaneously improve the absorption efficiency of the thermistor on the wavelength of 10-17 mu m and is used in a micro floating bridge structure according to the Wein's displacement law of radiant heat: (lambda): lambda)_mThe x T is 2898 mu m.K, and the thermistor structure of the aluminum nitride/vanadium oxide/aluminum nitride three-layer film can enhance the temperature measurement efficiency of the high-performance microbolometer at 17 to-102 ℃.

The purpose, technical content, features and effects of the present invention will be more readily understood by the following detailed description of the specific embodiments.

Drawings

Fig. 1 is a schematic cross-sectional view of a thermistor according to a first embodiment of the present invention;

fig. 2 is a temperature resistance characteristic curve of a thermistor according to a first embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of a thermistor according to a second embodiment of the present invention;

fig. 4 is a schematic cross-sectional view of a microbolometer according to a third embodiment of the present invention;

fig. 5 is a schematic cross-sectional view of a microbolometer according to a fourth embodiment of the present invention.

Description of the symbols

100. 200-thermistor

10-substrate

11-holes

20-three-layer stack structure

21-first aluminum nitride film

Film of 22-vanadium oxide

23-second aluminum nitride film

30-support foot

300. 500-microbolometer

50-micro floating bridge structure

60-space gap layer

Detailed Description

Referring to fig. 1, a thermistor 100 according to a first embodiment of the invention is shown. The thermistor 100 of the present embodiment forms a three-layer stack 20 of an aluminum nitride film/vanadium oxide film/aluminum nitride film over a substrate 10, wherein the three-layer stack 20 includes a first aluminum nitride film 21, a vanadium oxide film 22 and a second aluminum nitride film 23.

In this embodiment, the substrate 10 is a silicon substrate; for practical applications, the material of the substrate 10 may be selected from one of monocrystalline silicon, monocrystalline germanium, titanium dioxide, silicon nitride, titanium nitride, glass, sapphire and elemental metal.

The bottom layer of the three-layer stack structure 20 is a first aluminum nitride film 21, the first aluminum nitride film 21 is used as a buffer layer (buffer layer) between the substrate 10 and the vanadium oxide film 22, and simultaneously, the first aluminum nitride film can be used as a growth foundation of the vanadium oxide film 22, and in addition, because the aluminum nitride material has high thermal conductivity, the reaction speed and the temperature uniformity of the thermistor can be increased.

The middle layer of the three-layer stack structure 20 is a vanadium oxide film 22, the vanadium oxide film 22 is used as a heat sensitive reaction layer, the structural formula of the vanadium oxide film 22 is VOx, wherein x is 1.0-2.5, and the vanadium oxide film 22 has a high temperature resistivity (TCR), a fast reaction speed, a low process temperature and a wide temperature measurement range. The vanadium oxide film 22 can be a pure monoclinic phase or a tetragonal phase, and the thickness of the vanadium oxide film 22 is preferably 100-300 nm, and the vanadium oxide film 22 is pure vanadium oxide or vanadium oxide doped with other elements.

The top layer of the three-layer stack structure 20 is the second aluminum nitride film 23, and the second aluminum nitride film 23 is used as a passivation layer, which can provide high thermal conductivity and temperature uniformity, and can achieve the purpose of protection. The thickness of the first aluminum nitride thin film 21 and the second aluminum nitride thin film 23 is preferably 200 to 500 nm.

Referring to fig. 2, a temperature resistance characteristic curve of the thermistor 100 according to the first embodiment of the invention is shown. As shown in the figure, the sheet resistance value of the thermistor decreases with an increase in temperature (negative temperature resistance characteristic), and changes in a quadratic polynomial relationship. In this embodiment, the temperature resistance characteristic curve equation of the thermistor may be expressed as y ═ 0.019x²-3.5745x+219.05，R²When the temperature of the thermistor is 25 ℃, the sheet resistance value of the thermistor is 141.56 kq, y represents the sheet resistance value of the thermistor, x represents the measured temperature, R represents the curvature of the temperature resistance characteristic curve, and y represents the measured temperature.

The thermistor 100 of the present embodiment can be fabricated by sequentially depositing the first aluminum nitride film 21, the vanadium oxide film 22 and the second aluminum nitride film 23 on the substrate 10.

Referring to fig. 3, a cross-sectional structure diagram of a thermistor 200 according to a second embodiment of the invention is shown. Unlike the first embodiment, the thermistor 200 of the present embodiment partially hollows the substrate 10, and the hole-type thermistor 200 can be manufactured by sequentially depositing the first aluminum nitride thin film 21, the vanadium oxide thin film 22 and the second aluminum nitride thin film 23 on the substrate 10, and then etching the back surface of the substrate 10 to form the plurality of holes 11, thereby reducing the thermal capacity of the substrate 10 and increasing the thermal sensitivity of the thermistor 200.

Fig. 4 is a schematic cross-sectional view of a microbolometer 300 according to a third embodiment of the present invention. Unlike the first and second embodiments, the microbolometer 300 of the present embodiment is manufactured by suspending the three-layered stack structure above the substrate 10 by using 2 supporting legs 30, and the manufacturing process thereof may be completed by coating a polymer material on the substrate 10, sequentially depositing the first aluminum nitride thin film 21, the vanadium oxide thin film 22 and the second aluminum nitride thin film 23, and then removing the polymer material to form the supporting legs 30 connected between the three-layered stack structure 20 and the substrate 10.

Fig. 5 is a schematic cross-sectional view of a microbolometer 500 according to a fourth embodiment of the present invention. The microbolometer 500 of the present embodiment includes a microbridge structure 50, the microbridge structure 50 is suspended above the substrate 10, and an air gap layer 60 is formed between the microbridge structure 50 and the substrate 10, the microbridge structure 50 has a three-layer stack structure 20 of an aluminum nitride film/a vanadium oxide film/an aluminum nitride film, and the three-layer stack structure 20 includes a second aluminum nitride film 23, a vanadium oxide film 22 and a first aluminum nitride film 21 from top to bottom. The three-layer stack structure 20 of the micro-floating bridge structure 50 of the present embodiment has been described in detail in the above embodiments, and for brevity, will not be described again. Meanwhile, a person skilled in the art can also understand the specific structure and modifications of the microbolometer 500, and further details are not described herein.

Further illustrating the efficacy of the thermistor of the present invention in a microbolometer. In the three-layer stack structure of the thermistor, the first aluminum nitride film at the bottom layer is used as a supporting layer of the micro-floating bridge structure, has the characteristics of capability of bearing about 400MPa stress and good stability, can be used as a growth foundation of the vanadium oxide film, and can improve the temperature uniformity of the micro-floating bridge structure by utilizing the high thermal conductivity coefficient of the aluminum nitride material. The vanadium oxide film of the middle layer is used as a thermosensitive reaction layer, and has higher temperature resistivity, faster reaction speed, lower process temperature and wide temperature measurement range. The second aluminum nitride film on the top layer is used as a passivation layer, and can provide thermal conductivity and temperature uniformity, and can improve the absorption efficiency of infrared rays with the wavelength of 10-17 mu m.

In the invention, the aluminum nitride film can simultaneously improve the absorption efficiency of the microbolometer at the infrared ray with the wavelength of 10-17 μm, and the radiation heat Wien displacement law (Wein's displacement law): lambda_mThe x T is 2898 mu m.K, and the thermistor structure of the aluminum nitride/vanadium oxide/aluminum nitride three-layer film can enhance the temperature measurement efficiency of the high-performance microbolometer at 17 to-102 ℃.

TABLE 1 light and Heat Properties of aluminum nitride, silicon

Further, it is known that the silicon nitride film can also be used as the substrate material of the thermal sensitive film, and the vanadium oxide film is disposed between two aluminum nitride films of the thermistor of the present invention, and it can be seen from table 1 above that the aluminum nitride films have the following excellent properties compared to the silicon nitride films:

1. the aluminum nitride film has a high thermal conductivity and a high heat transfer efficiency.

2. The thermal expansion coefficient of the aluminum nitride film and the silicon substrate is closer to that of the silicon nitride film and the silicon substrate, and the aluminum nitride film is less prone to fall off due to thermal stress.

3. The dispersion of the silicon nitride film at a wavelength of 6-12 μm is higher than that of the aluminum nitride film, and the dispersion at a wavelength of 11 μm is significant, which is not favorable for spectrum detection.

4. For the thermal detector, the heat conduction efficiency (reaction speed) of the aluminum nitride film and the light absorption efficiency of the vanadium oxide film with the wavelength of 10-17 μm are superior to those of the silicon nitride film.

It should be noted that in the three-layer stack structure of the thermistor of the present invention, the first aluminum nitride film of the bottom layer must be limited to the lowest temperature that does not affect other layers and the electrical condition of the vanadium oxide, and the second aluminum nitride film of the top layer must be limited to the process temperature that does not affect the characteristics of the vanadium oxide film. The vanadium oxide film is a heat reaction layer and can present higher temperature resistivity.

In summary, according to the thermistor and the microbolometer based on the thermistor provided by the invention, the thermistor is a three-layer stack structure of the aluminum nitride film/the vanadium oxide film/the aluminum nitride film formed above the substrate, which is beneficial to improving the radiant heat detection degree, the resistance uniformity and the thermal stability of the thermistor.

The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive various changes or substitutions within the technical scope of the present invention, and these should be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.