Thermopile infrared detector and manufacturing method therefor

Abstract

Disclosed in the present invention are a thermopile infrared detector and a manufacturing method therefor. The thermopile infrared detector comprises a substrate, a supporting layer, an infrared absorption layer, a plurality of thermocouple strips, and metal electrode structures; the supporting layer is arranged on the substrate; the infrared absorption layer is arranged on the supporting layer and located in the middle of the supporting layer; the thermocouple strips are arranged on the supporting layer, are connected to the infrared absorption layer and are distributed along the edge of the infrared absorption layer, wherein the thermocouple strips are made of a bismuth telluride material, and the thermocouple strips each comprise a P-type bismuth telluride thermocouple strip and an N-type bismuth telluride thermocouple strip; and the metal electrode structures are arranged on the supporting layer, the P-type bismuth telluride thermocouple strips are connected in series by means of the metal electrode structures, and the N-type bismuth telluride thermocouple strips are connected in series by means of the metal electrode structures. According to the present invention, a thermocouple strip of a thermopile infrared sensor is made of a bismuth telluride material, so that the sensitivity of the thermopile infrared sensor can be greatly improved, improving the responsivity and the detectivity of the thermopile infrared sensor, and thus meeting high detection requirements.

Description

A thermopile infrared detector and its preparation method Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a thermopile infrared detector and a preparation method thereof. Background Art

[0002] Currently, infrared detectors are one of the most critical components in infrared systems. Thermopile infrared detectors are an early-developed type of uncooled infrared detector. They utilize numerous thermocouples connected in series based on the Seebeck effect to amplify the response voltage, ultimately achieving measurement. The key thermal sensor, the thermocouple, utilizes the thermoelectric effect of a conductor or semiconductor material to convert a temperature difference into an electrical potential difference. It connects two different conductors or semiconductors to form a closed circuit. One end (the hot end) absorbs radiation energy, causing the temperature to rise, while the other end (the cold end) remains at room temperature. The temperature difference between the two ends creates a potential difference, causing charge carriers in the conductor or semiconductor to migrate and accumulate at the cooler end, resulting in a potential difference. Due to their advantages, such as small size, room-temperature operation, wide-spectrum infrared radiation response, ability to detect constant radiation levels, and low manufacturing costs, thermopile infrared detectors are widely used in security surveillance, medical treatment, and life detection.

[0003] The performance of thermopile infrared detectors is generally measured by responsivity and detectivity. Higher responsivity and detectivity indicate better performance. Currently, conventional thermopile infrared detectors utilize structural design techniques, such as increasing the number of thermocouple strips, to increase the potential difference and, therefore, sensitivity. However, practice has shown that this approach is ineffective in improving device sensitivity. Due to material limitations, the output potential of a thermopile infrared detector is related to the Seebeck coefficient of the two thermoelectric materials. A higher Seebeck coefficient results in a higher output voltage. Increasing the Seebeck coefficient of the sensing element can also improve voltage output and responsivity. Thermal conductivity also influences a material's ability to conduct heat. Better thermal conductivity reduces temperature differences. Therefore, lower thermal conductivity and greater temperature differences contribute to improved responsivity. Lower resistivity also reduces device resistance, effectively improving detection rates. The ZT (thermoelectric figure of merit) is defined as temperature × Seebeck coefficient / (thermal conductivity × resistivity). Higher ZT values ​​indicate better material performance, resulting in higher device responsivity and detectivity.

[0004] The thermoelectric materials of existing thermopile infrared detectors generally use polycrystalline silicon materials. This type of structural device has a low duty cycle and poor material performance, a low Seebeck coefficient, and high thermal conductivity, resulting in a low Z value. As a result, the sensitivity improvement of the thermopile infrared sensor is greatly limited, and the detection rate and response rate cannot meet the high detection requirements of the detector.

[0005] Therefore, the existing technology still needs to be improved and developed.

[0006] Summary of the Invention

[0007] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a thermopile infrared detector and a method for preparing the same, so as to solve the problem that the detection rate and response rate of the existing thermopile infrared sensor cannot meet high detection requirements.

[0008] The technical solutions of the present invention are as follows:

[0009] In a first aspect, the present invention provides a thermopile infrared detector comprising: a substrate, a support layer, an infrared absorption layer, a plurality of thermocouple strips and a metal electrode structure;

[0010] The support layer is provided on the substrate;

[0011] The infrared absorbing layer is arranged on the supporting layer and is located in the middle of the supporting layer;

[0012] The thermocouple strips are arranged on the support layer and connected to the infrared absorption layer, and are distributed along the edge of the infrared absorption layer; wherein the thermocouple strips are made of bismuth telluride material, and the thermocouple strips include P-type bismuth telluride thermocouple strips and N-type bismuth telluride thermocouple strips;

[0013] The metal electrode structure is arranged on the support layer, the P-type bismuth telluride thermocouple bars are connected in series through the metal electrode structure, and the N-type bismuth telluride thermocouple bars are connected in series through the metal electrode structure.

[0014] In a further configuration of the present invention, the composition of the P-type bismuth telluride thermocouple strip is Bi 2-x Sb x Te3, wherein 0.5≤x≤2, the thickness of the P-type bismuth telluride thermocouple strip is 0.1-10 microns; the composition of the N-type bismuth telluride thermocouple strip is Bi2Te 3-y Se y , wherein 0≤y≤2, and the thickness of the N-type bismuth telluride thermocouple strip is 0.1-10 microns.

[0015] According to a further configuration of the present invention, one end of the thermocouple strip connected to the infrared absorbing layer is covered by the infrared absorbing layer.

[0016] According to a further configuration of the present invention, a cavity is provided at the bottom of the substrate.

[0017] According to a further configuration of the present invention, the infrared absorbing layer is a square structure or a circular structure.

[0018] According to a further configuration of the present invention, the substrate is a silicon substrate; and the supporting layer is one of a silicon nitride layer, a silicon oxide layer, a silicon oxynitride layer, and a PI film.

[0019] According to a further configuration of the present invention, the infrared absorption layer is a porous silicon nitride layer or an oxide absorption layer.

[0020] In a further arrangement of the present invention, the metal electrode structure includes a metal electrode and a metal electrode sheet;

[0021] The metal electrodes are connected between the P-type bismuth telluride thermocouple strips and between the N-type bismuth telluride thermocouple strips;

[0022] The metal electrode sheets are respectively connected to the head end and the tail end of the series structure formed by the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar;

[0023] The metal electrode includes a barrier layer and an electrode layer which are stacked together; the barrier layer is made of a material selected from the group consisting of Cr, Mo, Ti, Pt, and Au; and the electrode layer is made of a material selected from the group consisting of Al, Cu, and Mo.

[0024] In a second aspect, the present invention further provides a method for preparing the thermopile infrared detector as described above, comprising:

[0025] forming a support layer on a substrate;

[0026] forming a P-type bismuth telluride thermocouple bar and an N-type bismuth telluride thermocouple bar on the support layer;

[0027] Annealing the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar;

[0028] forming a metal electrode structure between the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar;

[0029] forming an infrared absorbing layer on the metal electrode structure;

[0030] A cavity is formed in the back substrate in the substrate.

[0031] According to a further configuration of the present invention, the step of forming a P-type bismuth telluride thermocouple strip and an N-type bismuth telluride thermocouple strip on the support layer comprises:

[0032] On the support layer, a mask is used and a photolithography process is adopted to form a P-type bismuth telluride thermocouple bar pattern and an N-type bismuth telluride thermocouple bar pattern on the surface of the P-type bismuth telluride layer and the surface of the N-type bismuth telluride layer through HMDS coating, coating, pre-baking, developing, and scanning the primer.

[0033] After depositing the bismuth telluride material, an etcher is used to etch away excess P-type bismuth telluride layer and N-type bismuth telluride layer, and an organic cleaning method is used to remove the photoresist, thereby forming a P-type bismuth telluride thermocouple strip and an N-type bismuth telluride thermocouple strip on the support layer;

[0034] The step of forming a metal electrode structure between the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar comprises:

[0035] Depositing a metal layer on the same plane as the P-type bismuth telluride thermocouple strip;

[0036] Using a mask and adopting a photolithography process, the metal layer surface is coated with HMDS, coated with a resin, pre-baked, exposed, developed, and scanned to form metal wiring, metal electrode patterns, and metal electrode sheet patterns;

[0037] The metal layer is etched away by an etcher, and the photoresist is removed by organic cleaning to form metal wiring, metal electrodes and metal electrode sheets to obtain a metal electrode structure;

[0038] The step of forming an infrared absorption layer on the metal electrode structure comprises:

[0039] A mask method or a photolithography process is used to form an infrared absorption layer pattern;

[0040] The infrared absorption layer is formed by physical sputtering or chemical vapor deposition process.

[0041] The present invention provides a thermopile infrared detector and a preparation method thereof. The thermopile infrared detector comprises: a substrate, a support layer, an infrared absorption layer, a plurality of thermocouple strips, and a metal electrode structure; the support layer is arranged on the substrate; the infrared absorption layer is arranged on the support layer and is located in the middle of the support layer; the thermocouple strips are arranged on the support layer and connected to the infrared absorption layer, and are distributed along the edge of the infrared absorption layer; wherein the thermocouple strips are made of bismuth telluride material, and the thermocouple strips include P-type bismuth telluride thermocouple strips and N-type bismuth telluride thermocouple strips; the metal electrode structure is arranged on the support layer, the P-type bismuth telluride thermocouple strips are connected in series through the metal electrode structure, and the N-type bismuth telluride thermocouple strips are connected in series through the metal electrode structure. The present invention uses bismuth telluride material to make the thermocouple bar of the thermopile infrared sensor. Since the bismuth telluride material has a high Seebeck coefficient and electrical conductivity and a low thermal conductivity, it has a high ZT value, which can greatly improve the sensitivity of the thermopile infrared sensor, thereby improving the response rate and detection rate of the thermopile infrared sensor and meeting high detection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary personnel in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0043] FIG1 is a schematic diagram of the overall structure of a thermopile infrared detector with a square structure in the present invention.

[0044] FIG2 is a top view of the thermopile infrared detector with a square structure according to the present invention.

[0045] FIG3 is a cross-sectional view of a thermopile infrared detector with a square structure according to the present invention.

[0046] Figure 4 shows the ZT values ​​of common thermoelectric materials at room temperature.

[0047] FIG5 is a schematic diagram of the overall structure of a circular thermopile infrared detector according to the present invention.

[0048] FIG6 is a top view of the circular thermopile infrared detector of the present invention.

[0049] FIG7 is a cross-sectional view of a circular thermopile infrared detector according to the present invention.

[0050] FIG8 is a schematic flow chart of a method for preparing a thermopile infrared detector according to the present invention.

[0051] FIG9 is a schematic diagram of a method for preparing a thermopile infrared detector according to the present invention.

[0052] The marks in the accompanying drawings are: 1. substrate; 11. cavity; 2. support layer; 3. P-type bismuth telluride thermocouple bar; 4. N-type bismuth telluride thermocouple bar; 5. metal electrode structure; 51. metal electrode; 52. metal electrode sheet; 6. infrared absorption layer; 301. hot end; 302. cold end. DETAILED DESCRIPTION

[0053] The present invention provides a thermopile infrared detector and a method for manufacturing the same. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is further described below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0054] In the embodiments and patent claims, unless otherwise specified herein, the words "a," "an," "the," and "the" may include plural forms. If the embodiments of the present invention include descriptions of "first," "second," etc., such descriptions are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly specifying the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features.

[0055] It should be further understood that the term "comprising" as used in the description of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when an element is said to be "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there can be intermediate elements. In addition, "connected" or "coupled" as used herein can include wireless connections or wireless couplings. The term "and / or" as used herein includes all or any units and all combinations of one or more associated listed items.

[0056] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0057] In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0058] Early thermopile infrared temperature sensors were made by depositing thermocouple materials on plastic or alumina substrates. This method resulted in large devices and was difficult to mass-produce. With the development and application of micro-electro-mechanical systems (MEMS) technology, thermopile infrared temperature sensors have been further developed. Practice has shown that micro-machined thermopile infrared thermopiles manufactured using MEMS technology can significantly improve their performance compared to traditional thermopile devices because they can effectively reduce their thermal conductivity and increase their integration. In addition, thermopile infrared detectors also have the advantages of light weight, low power consumption, good durability, low price, and stable performance. Therefore, they are widely used in many fields such as the automotive, aerospace, and electronics industries.

[0059] The performance of thermopile infrared detectors is generally expressed by the response rate and detection rate, among which the response rate It is the ratio of the response voltage to the infrared radiation density. The response rate indicates the ability of the thermopile detector to convert infrared radiation energy into electrical energy. The detection rate can be expressed as It reflects the detector's ability to detect infrared radiation and is an indicator of the extent to which the sensor can detect signals.

[0060] In practice, the larger the Seebeck coefficient of the thermocouple material that makes up a thermopile infrared detector, the lower its thermal conductivity. This means the temperature difference generated when absorbing the same amount of infrared radiation heat is greater, and the output voltage of the thermopile infrared detector is also greater, leading to higher sensitivity of the thermopile device. In processes compatible with integrated circuits, N-type and P-type polysilicon, which are compatible with CMOS processes, are generally used to fabricate thermocouple structures. However, polysilicon has a relatively low Seebeck coefficient, with the absolute value of the Seebeck coefficient for both N-type and P-type materials below 100 μV / K. Furthermore, the thermal conductivity is relatively high, exceeding 25 W / mK, and the ZT value is only 0.01 (N-type) and 0.02 (P-type). This significantly limits the sensitivity improvement of silicon-based thermopiles and makes miniaturization difficult.

[0061] To address the above technical issues, the present invention provides a thermopile infrared detector and a method for fabricating the same. The thermocouple strips of the thermopile infrared sensor are made of bismuth telluride. Because bismuth telluride has a high Seebeck coefficient and electrical conductivity, but low thermal conductivity, it has a high ZT value, significantly improving the sensitivity of the thermopile infrared sensor. This improves the responsivity and detectivity of the thermopile infrared sensor, meeting high detection requirements. Furthermore, due to the extremely low thermal conductivity of bismuth telluride, the thermocouple strips can achieve a large temperature difference in a small size, thus facilitating the miniaturization of the thermopile infrared detector.

[0062] Please refer to FIG. 1 to FIG. 7 simultaneously. The present invention provides a preferred embodiment of a thermopile infrared detector.

[0063] As shown in Figures 1 to 3, the present invention provides a thermopile infrared detector, which includes: a substrate 1, a support layer 2, an infrared absorption layer 6, a plurality of thermocouple strips, and a metal electrode structure 5. The support layer 2 is disposed on the substrate 1; the infrared absorption layer 6 is disposed on the support layer 2 and located in the middle of the support layer 2; the thermocouple strips are disposed on the support layer 2 and connected to the infrared absorption layer 6, and are distributed along the edges of the infrared absorption layer 6; the thermocouple strips are made of bismuth telluride material and include a P-type bismuth telluride thermocouple strip 3 and an N-type bismuth telluride thermocouple strip 4; the metal electrode structure 5 is disposed on the support layer 2, and the P-type bismuth telluride thermocouple strip 3 and the N-type bismuth telluride thermocouple strip 4 are connected in series through the metal electrode structure 5.

[0064] Specifically, the substrate 1, the support layer 2, and the infrared absorption layer 6 are sequentially arranged from bottom to top, with the infrared absorption layer 6 located at the center of the support layer 2. A plurality of thermocouple bars are provided, each comprising a P-type bismuth telluride thermocouple bar 3 and an N-type bismuth telluride thermocouple bar 4. The P-type bismuth telluride thermocouple bar 3 and the N-type bismuth telluride thermocouple bar 4 are spaced apart and distributed around the infrared absorption layer 6. One end of the P-type bismuth telluride thermocouple bar 3 and the N-type bismuth telluride thermocouple bar 4 are connected to the infrared absorption layer 6. The ends of the P-type bismuth telluride thermocouple bar 3 and the N-type bismuth telluride thermocouple bar 4 that are close to the infrared absorption layer 6 are hot ends 301, and the ends of the P-type bismuth telluride thermocouple bar 3 and the N-type bismuth telluride thermocouple bar 4 that are away from the infrared absorption layer 6 are cold ends 302. The metal electrode structure 5 connects the P-type bismuth telluride thermocouple bars 3 in series, and connects the N-type bismuth telluride thermocouple bars 4 in series to form a thermocouple bar series structure, thereby amplifying the response voltage.

[0065] Thermocouple material is a fundamental factor in determining the performance of thermopile infrared detectors. Figure 4 shows the ZT values ​​of several common thermoelectric materials used in thermopile infrared detectors. The Bi / Sb (bismuth / antimony) thermocouple is the most classic material combination in traditional thermocouples. Among all metal materials, Bi / Sb has a high Seebeck coefficient and very low thermal conductivity. Polycrystalline silicon (SiGe) offers excellent thermoelectric properties, simple manufacturing, and good compatibility, making it the thermocouple material of choice for most thermopile infrared detectors. PolySiGe has a low resistivity, but its Seebeck coefficient is not high.

[0066] As can be seen from Figure 4, bismuth telluride material is the thermoelectric material with the best thermoelectric performance near room temperature. Its ZT value is higher than that of currently commonly used thermoelectric materials. Its Seebeck coefficient can reach 200μV / K, its electrical conductivity is above 1E5S / m, and its thermal conductivity is about 1W / mK. The ZT figure of merit is more than an order of magnitude higher than that of traditional silicon-based materials.

[0067] The present invention uses bismuth telluride material to make the thermocouple strip of the thermopile infrared sensor, that is, uses bismuth telluride material as the sensitive element material of the thermopile infrared sensor device. Because bismuth telluride material has a high Seebeck coefficient and electrical conductivity, and a low thermal conductivity, it has a high ZT value, which can greatly improve the sensitivity of the thermopile infrared sensor, thereby improving the response rate and detection rate of the thermopile infrared sensor, and can meet high detection requirements. Moreover, due to the extremely low thermal conductivity of bismuth telluride, a large temperature difference can be obtained in a small size, and it can be integrated on the CMOS chip, which is conducive to the miniaturization design of the thermopile device. In addition, bismuth telluride is easy to manufacture and has high stability, and its thermoelectric performance is superior to that of traditional polycrystalline silicon. Therefore, the present invention provides a thermopile infrared detector that can achieve device miniaturization and high performance to the greatest extent, and can be applied to thermopile infrared detectors with four-end beam structures or two-end beam structures.

[0068] In some embodiments, the composition of the P-type bismuth telluride thermocouple strip is Bi 2-x Sb x Te3, wherein 0.5≤x≤2, the thickness of the P-type bismuth telluride thermocouple strip is 0.1-10 microns; the composition of the N-type bismuth telluride thermocouple strip is Bi2Te 3-y Se y , wherein 0≤y≤2, and the thickness of the N-type bismuth telluride thermocouple strip is 0.1-10 microns.

[0069] Specifically, the chemical formula of the P-type bismuth telluride thermocouple strip is Bi 2-x Sb x Te3, wherein 0.5≤x≤2, for example, x can be 0.5, 1, 2. When x is 1, the chemical formula of the P-type bismuth telluride thermocouple strip is Bi1Sb1Te3. The chemical formula of the N-type bismuth telluride thermocouple strip is Bi2Te 3-y Se y, where 0≤y≤2, for example, y can be 0, 1, or 2. When y is 1, the chemical formula of the N-type bismuth telluride thermocouple strip is Bi2Te2Se1. In this embodiment, the thickness of the P-type bismuth telluride thermocouple strip and the N-type bismuth telluride thermocouple strip are both in the range of 0.1-10 microns. For example, the thickness of the P-type bismuth telluride thermocouple strip can be 0.1 micron, 5 microns, or 10 microns, and the thickness of the N-type bismuth telluride thermocouple strip can be 0.1 micron, 6 microns, or 10 microns. The thickness of the P-type bismuth telluride thermocouple strip and the N-type bismuth telluride thermocouple strip can be different. For example, when the thickness of the P-type bismuth telluride thermocouple strip is 4 microns, the thickness of the N-type bismuth telluride thermocouple strip can be 7 microns.

[0070] In some embodiments, as shown in FIG3 , one end of the thermocouple bar connected to the infrared absorbing layer 6 is covered by the infrared absorbing layer 6 .

[0071] Specifically, the end of the thermocouple bar connected to the infrared absorption layer 6 is the hot end 301, and the edge of the hot end 301 of the thermocouple bar is covered by the infrared absorption layer 6, which is conducive to the thermocouple bar absorbing radiation energy, causing the temperature to rise higher, thereby making the temperature difference between the cold end 302 and the hot end 301 of the thermocouple bar higher, and ultimately generating a larger potential difference.

[0072] In some embodiments, as shown in FIG. 1 and FIG. 5 to FIG. 7 , the infrared absorption layer 6 has a square structure or a circular structure.

[0073] Specifically, the thermopile infrared detector can have a square or circular structure. When the thermocouple strips are distributed in a square shape, the cross-sections of the infrared absorption layer 6, the substrate 1, and the support layer 2 are all square, i.e., the thermopile infrared detector has a square structure. When the thermocouple strips are distributed in a circular shape, the cross-sections of the infrared absorption layer 6, the substrate 1, and the support layer 2 are all circular, i.e., the thermopile infrared detector has a circular structure.

[0074] In some embodiments, as shown in Figures 1 to 3, the metal electrode structure 5 includes a metal electrode 51 and a metal electrode sheet 52; the metal electrode 51 is connected between the P-type bismuth telluride thermocouple bars 3 and between the N-type bismuth telluride thermocouple bars 4; the metal electrode sheet 52 is respectively connected to the head end and the end of the series structure formed by the P-type bismuth telluride thermocouple bar 3 and the N-type bismuth telluride thermocouple bar 4; the metal electrode 51 includes a barrier layer and an electrode layer stacked together; the barrier layer is made of a material selected from Cr, Mo, Ti, Pt, and Au; and the electrode layer is made of a material selected from Al, Cu, and Mo.

[0075] Specifically, the metal electrode 51 has a rectangular structure and is connected between the P-type bismuth telluride thermocouple strips 3 and the N-type bismuth telluride thermocouple strips 4, so that the ends of the P-type bismuth telluride thermocouple strips 3 are connected in series, and the ends of the N-type bismuth telluride thermocouple strips 4 are connected in series. The metal electrode 51 located on the hot end 301 is the hot end electrode, and the metal electrode 51 located on the cold end 302 is the cold end electrode. The metal electrode sheets 52, located at both ends of the thermocouple strips, are capable of outputting a response voltage to the detection device.

[0076] In this embodiment, the metal electrode 51 includes a barrier layer and an electrode layer, and the metal electrode 51 is composed of a double or multiple metal layers of the barrier layer and the electrode layer. In some embodiments, the barrier layer can be made of, but not limited to, a material selected from the group consisting of Cr, Mo, Ti, Pt, and Au, and the electrode layer can be made of, but not limited to, a material selected from the group consisting of Al, Cu, and Mo. In some embodiments, the thickness of the metal electrode 51 is 0.1-10 microns, for example, the thickness of the metal electrode 51 can be 0.1 microns, 5 microns, or 10 microns. It should be noted that the metal electrode sheet 52 is made of the same material as the metal electrode 51, and the only difference is the shape.

[0077] In some embodiments, as shown in FIG3 , a cavity 11 is provided at the bottom of the substrate 1 .

[0078] Specifically, since the substrate 1 has good thermal conductivity, it will cause a heat short circuit in the thermopile sensor (i.e., the thermocouple strip), preventing a large temperature difference from being formed. The present invention provides a back cavity, i.e., the cavity 11, in the back substrate 1 of the substrate 1, which allows as much heat as possible to be transferred toward the thermocouple strip, thereby increasing the temperature difference between the hot and cold short ends and enhancing the thermovoltage signal.

[0079] In some embodiments, the substrate 1 is a silicon substrate; the support layer 2 is one of a silicon nitride layer, a silicon oxide layer, a silicon oxynitride layer, and a PI film; and the infrared absorption layer 6 is a porous silicon nitride layer or an oxide absorption layer.

[0080] Specifically, the substrate 1 is a silicon-based substrate, and the thickness of the substrate 1 is 50-1000 microns. For example, the thickness of the substrate 1 can be 50 microns, 500 microns, or 1000 microns. The supporting layer 2 can be a silicon nitride layer, a silicon oxide layer, or a silicon oxide layer. In addition, the supporting layer 2 can also be an insulating material layer, such as a PI film (polyimide film). The thickness of the supporting layer 2 is 0.2-10 microns. For example, the thickness of the supporting layer 2 can be 0.02 microns, 5 microns, or 10 microns. The infrared absorption layer 6 can be, but is not limited to, a porous silicon nitride layer or an oxide absorption layer. The thickness of the infrared absorption layer 6 is 0.1-10 microns. For example, the thickness of the infrared absorption layer 6 can be 0.1 microns, 5 microns, or 10 microns.

[0081] In some embodiments, as shown in FIG8 and FIG9 , the present invention further provides a method for preparing the thermopile infrared detector as described above, the method comprising the steps of:

[0082] S100, forming a support layer on a substrate;

[0083] Specifically, the substrate is made of silicon, which primarily serves as a heat sink and support. If it is too thin, the cold end temperature cannot be maintained at a constant high temperature when subsequently receiving infrared radiation, resulting in a small temperature difference between the cold and hot ends, further reducing the performance of the thermopile infrared detector. If the substrate is too thick, the thermopile infrared detector will be too large, which may affect the miniaturization of the device. Therefore, the thickness of the substrate needs to be between 50 and 1000 microns, for example, 50 microns, 500 microns, or 1000 microns.

[0084] When the substrate has not been processed, the support layer is prepared on the substrate. The selection of the material of the support layer is very critical for the design of the thermopile infrared detector. The material of the support layer should have low thermal conductivity and good mechanical strength. Because the support layer, like the substrate, also plays a role in heat conduction, if the thermal conductivity of the support layer is too high, when infrared radiation acts on the thermopile infrared detector, the infrared absorption zone will convert the absorbed infrared radiation into heat that will be dissipated through the support layer, thereby reducing the performance of the detector. In the actual application of thermopile infrared detectors, the support layer is in a suspended state, so it is required that the support layer should have a certain mechanical strength to play a good supporting role for the infrared absorption layer, thermocouple strips, metal electrode structure, etc. thereon. In some embodiments, the support layer can be one of a silicon nitride layer, a silicon oxide layer, or a silicon oxide layer. In addition, the support layer can also be an insulating material layer, for example, a PI film (polyimide film).

[0085] S200, forming a P-type bismuth telluride thermocouple bar and an N-type bismuth telluride thermocouple bar on the support layer;

[0086] Specifically, the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar are successively prepared on the support layer. When preparing the P-type bismuth telluride thermocouple bar, a mask is first used on the support layer and a photolithography process is adopted to form a P-type bismuth telluride thermocouple bar pattern by coating HMDS (hexamethyldisilazane) on the surface of the P-type bismuth telluride layer, performing photoresist coating, pre-baking, developing, and scanning the primer. After the P-type bismuth telluride material is deposited, an etcher is used to etch away the excess P-type bismuth telluride layer, and an organic cleaning method is used to remove the photoresist to form the P-type bismuth telluride thermocouple bar on the support layer. The deposition of the P-type bismuth telluride material can be achieved by using one of the processes selected from magnetron sputtering, thermal evaporation, metal-organic chemical vapor deposition (MOCVD), and chemical deposition.

[0087] After the P-type bismuth telluride thermocouple bar is prepared, the N-type bismuth telluride thermocouple bar is prepared. The preparation process of the N-type bismuth telluride thermocouple bar is the same as that of the P-type bismuth telluride thermocouple bar, except that the N-type bismuth telluride thermocouple bar is prepared using N-type bismuth telluride material. It should be noted that when preparing the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar, a hard mask or photolithography-liftoff process can also be used to form a pattern, and the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar can be formed by magnetron, thermal evaporation, MOCVD, or electrochemical deposition, thus eliminating the etching step.

[0088] S300, annealing the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar;

[0089] Specifically, after the preparation of the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar is completed, the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar are annealed at 250-400°C in a vacuum or inert gas environment for 0.5-4 hours. This can prevent impurities from contaminating the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar and reduce the volatilization of the tellurium element. In some embodiments, the annealing temperature can be 250°C, 300°C, or 400°C, and the annealing time can be 0.5h, 2.5h, or 4h. It should be understood that if the annealing temperature is too low or the annealing time is too short, the impurity ions cannot be activated well. If the annealing temperature is too high or the annealing time is too long, the thermal budget introduced will increase, which may affect stress. At the same time, the extended process time will also affect production capacity.

[0090] In existing methods for preparing P-type and N-type bismuth telluride thermocouples, the P-type bismuth telluride thermocouple material layer must be annealed before the P-type bismuth telluride thermocouple is prepared, and the N-type bismuth telluride thermocouple material layer must be annealed before the N-type bismuth telluride thermocouple is prepared. Compared to existing methods for preparing thermocouples, the present invention anneals the P-type and N-type bismuth telluride thermocouples after they are obtained. This reduces the number of steps required to prepare the thermopile infrared detector, thereby reducing production costs. In some embodiments, the annealing process can be performed using rapid thermal annealing or furnace annealing.

[0091] S400, forming a metal electrode structure between the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar;

[0092] Specifically, a metal layer is first deposited on the same plane as the P-type bismuth telluride thermocouple strip, and then a mask is used and a photolithography process is adopted to form metal wiring, metal electrode patterns and metal electrode sheet patterns on the surface of the metal layer through coating HMDS, coating, pre-baking, exposure, development, and scanning the bottom film. The metal layer is further etched away by an IBE etcher, and the photoresist is removed by organic cleaning to form metal wiring, metal electrodes and metal electrode sheets to obtain a metal electrode structure. Among them, the deposition of the metal layer includes the deposition of the barrier layer and the electrode layer, and the deposition method can adopt magnetron sputtering or chemical vapor deposition process. It should be noted that the width of the metal electrode and the metal electrode sheet is determined according to actual needs, and this embodiment does not make specific restrictions on this.

[0093] The metal electrode sheets are located at both ends of the thermocouple strips and are capable of outputting a response voltage to a detection device. The metal connecting wires are conductive wires connecting the P-type bismuth telluride thermocouple strips or the N-type bismuth telluride thermocouple strips via the metal electrodes. Furthermore, the P-type bismuth telluride thermocouple strips, the N-type bismuth telluride thermocouple strips, and the metal electrode sheets are also conductively connected via the metal connecting wires.

[0094] S500, forming an infrared absorption layer on the metal electrode structure;

[0095] Specifically, the infrared absorption layer is used to receive infrared radiation, and therefore requires a high infrared absorptivity and a low heat capacity. When preparing the infrared absorption layer, a masking method or photolithography process can be used to form the infrared absorption layer pattern, followed by physical sputtering or chemical vapor deposition. The infrared absorption layer needs to cover the hot end of the thermocouple to facilitate heat transfer.

[0096] S600 , forming a cavity in a back substrate in a substrate.

[0097] Specifically, a pattern is first formed on a layer on the back side of the substrate by a photolithography process using a mask, and then a deep silicon etcher is used to etch the support layer to form a cavity.

[0098] The present invention is described below with reference to specific embodiments.

[0099] Example 1

[0100] As shown in Figures 1 and 9, Figure 1 is a square structure thermopile infrared detector, and its manufacturing process is as follows: a SiO2 support layer is formed on a silicon substrate by thermal oxidation, specifically, a silicon wafer is prepared, the silicon wafer is cleaned using a standard RCA, and a layer of silicon oxide is grown by thermal oxidation; a P-type bismuth telluride thermocouple bar and an N-type bismuth telluride thermocouple bar are sequentially prepared by magnetron sputtering, and an exposure and development + liftoff process is used to form the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar layout respectively; after the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar are completed, After the preparation, Ti is used as the barrier layer material, and copper electrodes are used to complete the preparation of the metal electrode structure to realize the series connection of the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar; then the infrared absorption layer is prepared, and a mask is used to coat HMDS on the surface of the infrared absorption layer, perform photoresist coating, pre-bake, expose, develop, scan the base film, and etch the absorption area pattern through an etcher, and the infrared absorption layer is covered with silicon nitride using a chemical vapor deposition process; finally, the back of the substrate is etched to the support layer through a deep silicon etcher to form a cavity, and a square thermopile infrared detector can be obtained.

[0101] Example 2

[0102] As shown in FIG5 , FIG5 is a circular structure thermopile infrared detector, and its manufacturing process is: a PI film support layer is formed on a silicon substrate by a spinning method. P-type bismuth telluride thermocouple bars and N-type bismuth telluride thermocouple bars are sequentially prepared by electrochemical deposition, and the P-type bismuth telluride thermocouple bars and N-type bismuth telluride thermocouple bar patterns are formed respectively by exposure, development and liftoff processes. After the preparation of the P-type bismuth telluride thermocouple bars and the N-type bismuth telluride thermocouple bars is completed, Mo is used as a barrier layer material, and an aluminum electrode is used to complete the preparation of the metal electrode structure, thereby realizing the series connection of the P-type bismuth telluride thermocouple bars and the N-type bismuth telluride thermocouple bars. A mask is used to coat HMDS on the surface of the infrared absorption layer, perform photoresist coating, pre-bake, expose, develop, and scan the bottom film, and an etcher is used to etch the absorption area pattern. The infrared absorption layer is then covered with nickel oxide by a chemical vapor deposition process. Finally, a deep silicon etcher is used to etch the back side of the substrate to the support layer to form a cavity, thereby obtaining a circular structure thermopile infrared detector.

[0103] In summary, the thermopile infrared detector and the preparation method thereof provided by the present invention have the following beneficial effects:

[0104] The thermocouple strips of thermopile infrared sensors are made of bismuth telluride. Because bismuth telluride has a high Seebeck coefficient and electrical conductivity, and a low thermal conductivity, it has a high ZT value, which can greatly improve the sensitivity of thermopile infrared sensors. This improves the response rate and detection rate of thermopile infrared sensors, meeting high detection requirements. The detection rate can reach above 10E9, which is more than an order of magnitude higher than that of existing commercial silicon-based thermopile devices.

[0105] Bismuth telluride has extremely low thermal conductivity, which can achieve a large temperature difference in a small size and can be integrated on-chip with CMOS, thus facilitating the miniaturization design of thermopile devices.

[0106] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A thermopile infrared detector, characterized in that: include: Substrate, support layer, infrared absorption layer, several thermocouple strips and metal electrode structure; The support layer is provided on the substrate; The infrared absorbing layer is arranged on the supporting layer and is located in the middle of the supporting layer; The thermocouple strips are arranged on the support layer and connected to the infrared absorption layer, and are distributed along the edge of the infrared absorption layer; wherein the thermocouple strips are made of bismuth telluride material, and the thermocouple strips include P-type bismuth telluride thermocouple strips and N-type bismuth telluride thermocouple strips; The metal electrode structure is arranged on the support layer, the P-type bismuth telluride thermocouple bars are connected in series through the metal electrode structure, and the N-type bismuth telluride thermocouple bars are connected in series through the metal electrode structure.

2. The thermopile infrared detector according to claim 1, characterized in that: The composition of the P-type bismuth telluride thermocouple strip is Bi 2-x Sb x Te3, wherein 0.5≤x≤2, the thickness of the P-type bismuth telluride thermocouple strip is 0.1-10 microns; the composition of the N-type bismuth telluride thermocouple strip is Bi2Te 3-y Se y , wherein 0≤y≤2, and the thickness of the N-type bismuth telluride thermocouple strip is 0.1-10 microns.

3. The thermopile infrared detector according to claim 1, characterized in that: One end of the thermocouple bar connected to the infrared absorption layer is covered by the infrared absorption layer.

4. The thermopile infrared detector according to claim 1, characterized in that: A cavity is provided at the bottom of the substrate.

5. The thermopile infrared detector according to claim 1, characterized in that: The infrared absorption layer has a square structure or a circular structure.

6. The thermopile infrared detector according to claim 1, characterized in that: The substrate is a silicon substrate; the supporting layer is one of a silicon nitride layer, a silicon oxide layer, a silicon oxynitride layer, and a PI film.

7. The thermopile infrared detector according to claim 1, characterized in that: The infrared absorption layer is a porous silicon nitride layer or an oxide absorption layer.

8. The thermopile infrared detector according to claim 1, characterized in that: The metal electrode structure includes a metal electrode and a metal electrode sheet; The metal electrodes are connected between the P-type bismuth telluride thermocouple strips and between the N-type bismuth telluride thermocouple strips; The metal electrode sheets are respectively connected to the series connection formed by the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar. the beginning and end of the structure; The metal electrode includes a barrier layer and an electrode layer which are stacked together; the barrier layer is made of a material selected from the group consisting of Cr, Mo, Ti, Pt, and Au; and the electrode layer is made of a material selected from the group consisting of Al, Cu, and Mo.

9. A method for preparing a thermopile infrared detector according to any one of claims 1 to 8, characterized in that: include: forming a support layer on a substrate; forming a P-type bismuth telluride thermocouple bar and an N-type bismuth telluride thermocouple bar on the support layer; Annealing the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar; forming a metal electrode structure between the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar; forming an infrared absorbing layer on the metal electrode structure; A cavity is formed in the back substrate in the substrate.

10. The method for preparing a thermopile infrared detector according to claim 9, wherein: The step of forming a P-type bismuth telluride thermocouple strip and an N-type bismuth telluride thermocouple strip on the support layer includes: On the support layer, a mask is used and a photolithography process is adopted to form a P-type bismuth telluride thermocouple bar pattern and an N-type bismuth telluride thermocouple bar pattern on the surface of the P-type bismuth telluride layer and the surface of the N-type bismuth telluride layer through HMDS coating, coating, pre-baking, developing, and scanning the primer. After depositing the bismuth telluride material, an etcher is used to etch away excess P-type bismuth telluride layer and N-type bismuth telluride layer, and an organic cleaning method is used to remove the photoresist, thereby forming a P-type bismuth telluride thermocouple strip and an N-type bismuth telluride thermocouple strip on the support layer; The step of forming a metal electrode structure between the P-type bismuth telluride thermocouple bar and the N-type bismuth telluride thermocouple bar comprises: Depositing a metal layer on the same plane as the P-type bismuth telluride thermocouple strip; Using a mask and adopting a photolithography process, the metal layer surface is coated with HMDS, coated with a resin, pre-baked, exposed, developed, and scanned to form metal connection patterns, metal electrode patterns, and metal electrode sheet patterns; The metal layer is etched away by an etcher, and the photoresist is removed by organic cleaning to form metal wiring, metal electrodes and metal electrode sheets to obtain a metal electrode structure; The step of forming an infrared absorption layer on the metal electrode structure comprises: A mask method or a photolithography process is used to form an infrared absorption layer pattern; The infrared absorption layer is formed by physical sputtering or chemical vapor deposition process.

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