Thermopile infrared detector and preparation method thereof

Abstract

The present invention provides a thermopile infrared detector and a preparation method thereof, and relates to the technical field of thermopile infrared detectors. The thermopile infrared detector comprises a processed silicon substrate, an infrared absorption layer arranged on the processed silicon substrate, a back cavity with an opening downward formed by patterning and etching the middle of the processed silicon substrate, and a metal reflection layer is arranged in the back cavity. A cavity is formed by enclosing the processed silicon substrate, the metal reflection layer, and the infrared absorption layer, and the cavity is an optical resonant cavity. Infrared rays are focused on the infrared absorption layer through a lens, and the infrared rays reaching the infrared absorption layer and the infrared rays reflected back by the metal reflection layer just form an optical path difference of about 1 / 2 in the infrared absorption layer, thereby forming a standing wave effect, so that the infrared rays focused on the hot end infrared absorption layer are absorbed as much as possible. The infrared absorption rate is greatly improved, thereby increasing the response rate and detection rate of the thermopile infrared detector, and greatly reducing the noise equivalent temperature difference of the thermopile infrared detector.

Description

Technical Field

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

[0002] Non-contact infrared temperature measurement technology can quickly and conveniently measure the surface temperature of an object. It can quickly measure the temperature reading without mechanically contacting the object being measured. It can reliably measure hot, dangerous or difficult-to-reach objects without contaminating or damaging the object being measured. Infrared temperature measurement has the advantages of fast response time, non-contact, safe use and long service life. It plays an important role in product quality control and monitoring, online equipment fault diagnosis, safety protection and energy conservation.

[0003] All objects with a temperature above absolute zero are constantly emitting infrared radiation energy to the surrounding space. The infrared radiation characteristics of an object, such as the size of the radiation energy and its distribution by wavelength, are closely related to its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately determined. This is the objective basis for infrared radiation temperature measurement. Infrared is located between visible light and radio waves. The infrared wavelength is usually expressed in microns, with a wavelength range of 0.7 microns to 1000 microns. In fact, the 0.7 micron to 14 micron band is used for infrared temperature measurement.

[0004] The technologies for achieving non-contact infrared temperature measurement include long-wave infrared focal plane detectors, pyroelectric infrared detectors, and thermopile infrared detectors based on the Seebeck effect. Among them, long-wave infrared focal plane detectors are not suitable for very low-cost applications such as smart homes and smart buildings due to their high cost. Although pyroelectric infrared detectors are low-cost, they require mechanical choppers, which reduces the reliability of the system and limits their application. Thermopile infrared detectors are very suitable for smart homes, smart buildings, and low-cost non-contact temperature measurement due to their low price and suitable performance.

[0005] Non-contact infrared temperature measurement consists of an optical system, a photoelectric detector, a signal amplifier, signal processing, and display output. The optical system gathers the infrared radiation energy of the target within its field of view. The size of the field of view is determined by the optical parts of the thermometer and their positions. The infrared energy is focused on the photoelectric detector and converted into a corresponding electrical signal. The signal passes through the amplifier and signal processing circuit, and is converted into the temperature value of the measured target after correction according to its internal algorithm and target emissivity.

[0006] The infrared absorption rate of the hot end of traditional thermopile devices is low. Summary of the invention

[0007] The purpose of the present invention is to provide a thermopile infrared detector and a method for preparing the same to improve the above problems. In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] The embodiment of the present invention provides a thermopile infrared detector, comprising a processed silicon substrate, an infrared absorption layer disposed on the processed silicon substrate, a back cavity with an opening facing downward formed by patterning and etching the middle of the processed silicon substrate, and a metal reflection layer disposed in the back cavity. A cavity is formed by enclosing the processed silicon substrate, the metal reflection layer, and the infrared absorption layer, and the cavity is an optical resonant cavity.

[0009] Furthermore, the thickness of the optical resonant cavity is not less than 1 μm.

[0010] Furthermore, a support layer is arranged in the back cavity along the back side of the metal reflective layer to support the metal reflective layer.

[0011] Furthermore, the material of the support layer is silicon oxide and / or silicon nitride.

[0012] Furthermore, a plurality of patterned thermocouple first materials are disposed on the infrared absorption layer, and the spacing distance between each adjacent two thermocouple first materials among the plurality of thermocouple first materials is a preset distance.

[0013] Furthermore, the first material of the plurality of thermocouples and the infrared absorption layer are covered with an isolation film.

[0014] Furthermore, two contact holes are provided on the top contact surface between the isolation film and each thermocouple first material, and the thermopile second material is provided on each adjacent two contact holes and on the portion of the isolation film between each adjacent two contact holes to form a metal thermopile interconnection pattern.

[0015] Furthermore, a passivation layer is provided on the surface of the second material of the thermopile.

[0016] Furthermore, the processed silicon substrate includes: an original silicon substrate, a first composite edge portion and a second composite edge portion of a first composite film arranged on the original silicon substrate, a first sacrificial edge portion of a sacrificial layer arranged on the first composite edge portion, and a second sacrificial edge portion of the sacrificial layer arranged on the second composite edge portion.

[0017] In the second aspect, an embodiment of the present invention provides a method for preparing a thermopile infrared detector, the method comprising: providing an infrared absorption layer on a processed silicon substrate; patterning and etching the middle portion of the processed silicon substrate to form a back cavity with an opening facing downward; providing a metal reflective layer in the back cavity, and then forming a cavity by enclosing the processed silicon substrate, the metal reflective layer, and the infrared absorption layer, the cavity being an optical resonant cavity.

[0018] The beneficial effects of the embodiment of the present invention are as follows: the thermopile infrared detector comprises a processed silicon substrate, an infrared absorption layer arranged on the processed silicon substrate, and a back cavity with an opening downward formed by patterning and etching the middle of the processed silicon substrate, wherein a metal reflection layer is arranged in the back cavity. A cavity is formed by enclosing the processed silicon substrate, the metal reflection layer, and the infrared absorption layer, and the cavity is an optical resonant cavity. Infrared rays are focused to the infrared absorption layer at the hot end of the thermopile infrared detector through a lens, a part of the infrared rays are absorbed by the infrared absorption layer, a part of the infrared rays may pass through the infrared absorption layer and then be incident on the metal reflection layer, and then be reflected back to the infrared absorption layer, so that the infrared rays reaching the infrared absorption layer and the infrared rays reflected back by the reflection surface of the metal reflection layer just form an optical path difference of about 1 / 2 in the infrared absorption layer, thereby forming a standing wave effect, so that the infrared rays focused on the infrared absorption layer at the hot end are absorbed as much as possible. The infrared absorption rate is greatly improved, thereby increasing the response rate and detection rate of the thermopile infrared detector, and greatly reducing the noise equivalent temperature difference of the thermopile infrared detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A first structural diagram of a conventional thermopile infrared detector provided by an embodiment of the present invention;

[0021] Figure 2 A second structural diagram of a conventional thermopile infrared detector provided by an embodiment of the present invention;

[0022] Figure 3 A first structural diagram formed in the method for preparing a thermopile infrared detector provided by an embodiment of the present invention;

[0023] Figure 4 A second structural diagram formed in the method for preparing the thermopile infrared detector provided by an embodiment of the present invention;

[0024] Figure 5 A third structural diagram formed in the method for preparing a thermopile infrared detector provided by an embodiment of the present invention;

[0025] Figure 6 A fourth structural diagram formed in the method for preparing a thermopile infrared detector provided by an embodiment of the present invention;

[0026] Figure 7 A fifth structural diagram formed in the method for preparing the thermopile infrared detector provided by an embodiment of the present invention;

[0027] Figure 8 A sixth structural diagram formed in the method for preparing a thermopile infrared detector provided by an embodiment of the present invention;

[0028] Fig. 9 A seventh structural diagram formed in the method for preparing a thermopile infrared detector provided by an embodiment of the present invention;

[0029] Fig.10 The eighth structural diagram formed in the method for preparing the thermopile infrared detector provided by the embodiment of the present invention;

[0030] Fig.11 A ninth structural diagram formed in the method for preparing a thermopile infrared detector provided by an embodiment of the present invention;

[0031] Fig.12 A tenth structural diagram formed in the method for preparing a thermopile infrared detector provided by an embodiment of the present invention;

[0032] Fig.13 The eleventh structural diagram formed in the method for preparing the thermopile infrared detector provided by the embodiment of the present invention;

[0033] Fig.14 A twelfth structural diagram formed in the method for preparing a thermopile infrared detector provided by an embodiment of the present invention;

[0034] Fig.15 A structural diagram of a thermopile infrared detector provided in an embodiment of the present invention.

[0035] In the figure: 200-thermopile infrared detector; 210-original silicon substrate; 212-first composite film; 2122-first composite edge; 2124-second composite edge; 214-sacrificial layer; 2142-middle part of sacrificial layer; 2144-first sacrificial edge; 2146-second sacrificial edge; 216-infrared absorption layer; 218-thermocouple first material; 220-isolation film; 2202-contact hole; 222-thermopile second material; 224-passivation layer; 2242-wire hole; 226-back cavity; 228-metal reflective layer; 230-support layer; 232-optical resonant cavity. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0039] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invented product is usually placed when in use, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0040] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the term "disposed" is understood in a broad sense, for example, it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] like Figure 1The traditional thermopile infrared detector shown in the figure is a pyroelectric infrared sensor. The thermopile is composed of two or more thermocouples connected in series based on the thermoelectric effect - Seebeck effect. The thermoelectric potential output by each thermocouple is superimposed on each other to form the output voltage of the thermopile. The structure of the thermopile consists of a hot-end infrared absorption surface and a cold-end reference temperature end. H represents the hot end and C represents the cold end. The structure of the traditional thermopile infrared detector uses a suspended different material with a high Seebeck coefficient difference (such as P-type polysilicon and metal aluminum) to contact to become the hot end of the thermopile; and the different materials located on the substrate contact to become the cold end of the thermopile. In this way, multiple cold and hot ends are connected end to end to form a thermopile device. Usually, the cold end represents the ambient temperature, and the temperature difference between the hot end and the cold end represents the ratio of the net radiant heat absorbed by the hot end of the device (the radiant heat absorbed by the hot end minus the heat conducted, convected and radiated by the hot end) to the heat capacity of the hot end. The greater the temperature difference between the hot end and the cold end, the greater the voltage signal output by the thermopile. Through reasonable optical and thermal design, the hot end has a higher 8-14um long-wave infrared absorption rate and appropriate heat capacity and thermal conductivity, thereby achieving a suitable thermal time constant (time constant = hot end heat capacity / hot end to cold end thermal conductivity) to achieve a higher device response rate and detection rate, as well as a lower noise equivalent temperature difference (NETD, Noise Equivalent Temperature Difference).

[0042] See also Figure 2 , the conventional thermopile infrared detector shown in FIG. 1 includes a substrate 110, a hot end film 120 disposed on the substrate 110, a thermopile material 130 disposed on the hot end film, a metal aluminum 150, a film layer 140 between the thermopile material 130 and the metal aluminum 150, and a hole 160 disposed on the passivation layer. The thickness of the hot end film 120 is only about 1 to 2 um, and it is difficult to simultaneously achieve a high infrared absorption rate, a low heat capacity, and a low thermal conductivity, thereby achieving a high response rate and detection rate and a low NETD.

[0043] In order to achieve a higher infrared absorption rate, it is necessary to increase the thickness of the film at the hot end of the device, which is bound to increase the heat capacity and thermal conductivity of the hot end of the device. From the above analysis, we know that the increase in the heat capacity and thermal conductivity of the hot end will cause most of the infrared radiation heat absorbed by the hot end to be introduced into the cold end through heat conduction, and the net radiation heat absorbed by the hot end will be reduced. In addition, because the heat capacity of the hot end increases, the temperature difference between the hot end and the cold end is directly reduced, thereby reducing the response rate and detection rate of the device and increasing the NETD of the device.

[0044] If the thickness of the hot end film is reduced, the infrared radiation absorption rate of the hot end will inevitably be reduced, and the purpose of improving the device performance will not be achieved. In addition, because the thickness of the hot end film is reduced, the difficulty of process processing will be greatly increased. During the back cavity process, it is very easy to cause the hot end film to rupture, thereby destroying the device.

[0045] In order to solve the defects of the existing thermopile infrared detectors, the embodiments of the present invention provide a thermopile infrared detector and a preparation method thereof. By changing the structure of the infrared detector of the thermopile device, the absorption rate of the hot end film is increased, and the heat capacity and thermal conductivity of the hot end film are reduced, thereby improving the response rate and detection rate, thereby reducing the noise equivalent temperature difference.

[0046] An embodiment of the present invention provides a method for preparing a thermopile infrared detector, which may include:

[0047] providing an infrared absorption layer on the processed silicon substrate;

[0048] Patterning and etching the middle portion of the processed silicon substrate to form a back cavity with an opening facing downward;

[0049] A metal reflective layer is arranged in the back cavity, and then a cavity is formed by enclosing the processed silicon substrate, the metal reflective layer and the infrared absorption layer. The cavity is an optical resonant cavity.

[0050] For further information, see Figure 3-Figure 5 , an infrared absorption layer is provided on a processed silicon substrate, comprising:

[0051] A first composite film 212 is provided on the original silicon substrate 210;

[0052] Disposing a sacrificial layer 214 on the first composite film 212;

[0053] The sacrificial layer 214 is etched into a pattern to form a sacrificial layer middle portion 2142, a first sacrificial edge portion 2144 and a second sacrificial edge portion 2146;

[0054] An infrared absorption layer 216 is disposed on the sacrificial layer middle portion 2142 , the first sacrificial edge portion 2144 , and the second sacrificial edge portion 2146 .

[0055] Further, see Figure 6-Figure 12 After the infrared absorption layer 216 is disposed on the sacrificial layer middle portion 2142, the first sacrificial edge portion 2144 and the second sacrificial edge portion 2146, the method may further include patterning and etching the middle portion of the processed silicon substrate to form a back cavity with an opening downward.

[0056] A thermopile first material is disposed on the infrared absorption layer 216 and patterned to form a plurality of patterned thermocouple first materials 218, wherein the spacing distance between each adjacent two thermocouple first materials 218 in the plurality of thermocouple first materials 218 is a preset distance;

[0057] An isolation film 220 is covered on the plurality of thermocouple first materials 218 and the infrared absorption layer 216; two contact holes 2202 are provided on the top contact surface between the isolation film 220 and each of the thermocouple first materials 218;

[0058] A second thermopile material 222 is disposed on each adjacent two contact holes 2202 and on a portion of the isolation film 220 between each adjacent two contact holes 2202 in the two contact holes 2202 to form a metal thermopile interconnection pattern;

[0059] A passivation layer 224 is disposed on the surface of the second material 222 of the thermopile and patterned; a plurality of line holes 2242 are disposed on the patterned passivation layer 224 .

[0060] Accordingly, the middle portion of the processed silicon substrate is patterned and etched to form a back cavity with an opening facing downward, including:

[0061] The middle portion of the original silicon substrate 210 is patterned and etched to form a back cavity 226 with an opening facing downward.

[0062] Furthermore, the middle portion of the original silicon substrate 210 is patterned and etched to form a back cavity 226 with an opening facing downward, including:

[0063] The middle portion of the original silicon substrate 210 is patterned, deep silicon etched, or single crystal silicon is etched by KOH wet etching to form a back cavity 226 with an opening facing downward.

[0064] For further information, see Fig.13 After patterning, deep silicon etching or KOH wet etching of single crystal silicon in the middle of the original silicon substrate 210 to form a back cavity 226 with an opening downward, and before providing a metal reflective layer in the back cavity, the method may further include:

[0065] The middle portion of the first composite film 212 is etched to form a first composite edge portion 2122 and a second composite edge portion 2124 .

[0066] For further information, see Figure 14-15 , a metal reflective layer is arranged in the back cavity, including:

[0067] A metal reflective layer 228 is provided in the back cavity 226 by evaporation or sputtering;

[0068] A support layer 230 is disposed on the metal reflective layer 228 along the back side of the metal reflective layer 228 by plasma enhanced chemical vapor deposition to support the metal reflective layer 228;

[0069] The optical resonant cavity 232 is formed by chemically reacting DHF, XeF2 or O2 plasma with the sacrificial layer middle portion 2142 .

[0070] The method for preparing a thermopile infrared detector provided by an embodiment of the present invention comprises the following steps: providing an infrared absorption layer on a processed silicon substrate; patterning and etching the middle part of the processed silicon substrate to form a back cavity with an opening facing downward; providing a metal reflection layer in the back cavity, and then enclosing a cavity through the processed silicon substrate, the metal reflection layer, and the infrared absorption layer, and the cavity is an optical resonant cavity. Infrared rays are focused on the infrared absorption layer at the hot end of the thermopile infrared detector through a lens, part of the infrared rays are absorbed by the infrared absorption layer, and part of the infrared rays may pass through the infrared absorption layer and then be incident on the metal reflection layer, and then be reflected back to the infrared absorption layer, so that the infrared rays reaching the infrared absorption layer and the infrared rays reflected back from the reflection surface of the metal reflection layer just form a light path difference of about 1 / 2 in the infrared absorption layer, thereby forming a standing wave effect, so that the infrared rays focused on the infrared absorption layer at the hot end are absorbed as much as possible. The infrared absorption rate is greatly improved, thereby increasing the response rate and detection rate of the thermopile infrared detector, and greatly reducing the noise equivalent temperature difference of the thermopile infrared detector.

[0071] See also Fig.15 The embodiment of the present invention provides a thermopile infrared detector 200, comprising a processed silicon substrate, an infrared absorption layer 216 disposed on the processed silicon substrate, and a back cavity 226 with an opening downward formed by patterning and etching the middle of the processed silicon substrate, wherein a metal reflection layer 228 is disposed in the back cavity 226. A cavity is formed by enclosing the processed silicon substrate, the metal reflection layer 228, and the infrared absorption layer 216, and the cavity is an optical resonant cavity 232.

[0072] Furthermore, the thickness of the optical resonant cavity 232 is not less than 1 μm. In this embodiment, the thickness of the optical resonant cavity 232 can be about 1 / 4 wavelength of 8-14 μm long-wave infrared. For example, the thickness of the optical resonant cavity 232 can be 2 μm. The thickness of the infrared absorption layer 216 can be 0.5 μm. This can significantly reduce the thickness of the hot-end infrared absorption layer. This can improve the infrared absorption rate of the hot end of the thermopile infrared detector and reduce the heat capacity and thermal conductivity of the hot-end film.

[0073] Furthermore, a support layer 230 is disposed in the back cavity 226 along the back side of the metal reflective layer 228 to support the metal reflective layer 228 .

[0074] Furthermore, the material of the support layer 230 may be silicon oxide and / or silicon nitride.

[0075] Furthermore, a plurality of patterned thermocouple first materials 218 are disposed on the infrared absorption layer 216 , and the spacing distance between each two adjacent thermocouple first materials 218 in the plurality of thermocouple first materials 218 is a preset distance.

[0076] Furthermore, the plurality of thermocouple first materials 218 and the infrared absorption layer 216 are covered with an isolation film 220 .

[0077] Furthermore, two contact holes 2202 are provided on the top contact surface between the isolation film 220 and each thermocouple first material 218, and the thermopile second material 222 is provided on each adjacent two contact holes 2202 and on the portion of the isolation film 220 between each adjacent two contact holes 2202 to form a metal thermopile interconnection pattern.

[0078] Furthermore, the thermopile second material 222 may be aluminum.

[0079] Furthermore, a passivation layer 224 is disposed on the surface of the thermopile second material 222 .

[0080] Furthermore, a plurality of line holes 2242 are provided on the passivation layer 224. It does not affect the absorption rate of 8-14um long-wave infrared, and also reduces the heat capacity and thermal conductivity of the bridge surface, thereby further improving the response rate and detection rate of the thermopile infrared detector, and can significantly reduce the noise equivalent temperature difference of the thermopile infrared detector. Under the premise of keeping the performance of the thermopile infrared detector unchanged, the chip area can be significantly reduced, and the area of ​​the hot-end infrared absorption layer and the size of the back cavity can be reduced accordingly, which can further reduce the risk of hot-end film rupture during back cavity etching, and significantly improve the manufacturability of the device.

[0081] Furthermore, the material of the isolation film 220 may be silicon oxide and / or silicon nitride. The material of the passivation layer 224 may be silicon oxide and / or silicon nitride.

[0082] Furthermore, the processed silicon substrate includes: an original silicon substrate 210, a first composite edge portion 2122 and a second composite edge portion 2124 of a first composite film 212 arranged on the original silicon substrate 210, a first sacrificial edge portion 2144 of a sacrificial layer 214 arranged on the first composite edge portion 2122, and a second sacrificial edge portion 2146 of the sacrificial layer arranged on the second composite edge portion 2124.

[0083] Further, the material of the first composite film 212 may be silicon oxide. The material of the first composite edge portion 2122 and the second composite edge portion 2124 may be silicon oxide. The material of the sacrificial layer may be polysilicon or polyimide. That is, the material of the first sacrificial edge portion 2144 and the second sacrificial edge portion 2146 may be polysilicon or polyimide.

[0084] Furthermore, the infrared absorption layer 216 may be made of silicon oxide and / or silicon nitride.

[0085] In addition, the chip area can be significantly reduced, thereby reducing the back cavity area, thereby increasing the manufacturing yield of the thermopile infrared detector, improving the manufacturability of the thermopile infrared detector, and greatly reducing the manufacturing cost of the thermopile infrared detector.

[0086] The working principle of a thermopile infrared detector 200 provided in an embodiment of the present invention is as follows:

[0087] Infrared rays with a wavelength of 8 to 14 um are focused by a lens onto the infrared absorption layer 216 at the hot end of the thermopile infrared detector. Part of the infrared rays are absorbed by the infrared absorption layer 216, and part of them may pass through the infrared absorption layer 216 and then be incident on the metal reflection layer 228, and then be reflected back to the infrared absorption layer 216. In this way, the infrared rays reaching the infrared absorption layer 216 and the infrared rays reflected back from the reflection surface of the metal reflection layer 228 just form a light path difference of about 1 / 2 in the infrared absorption layer, thereby forming a standing wave effect, so that the infrared rays focused on the hot end infrared absorption layer 216 are absorbed as much as possible.

[0088] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the thermopile infrared detector described above can refer to the corresponding process in the aforementioned embodiment of the preparation method of the thermopile infrared detector, and will not be repeated here.

[0089] A thermopile infrared detector provided by an embodiment of the present invention comprises a processed silicon substrate, an infrared absorption layer arranged on the processed silicon substrate, and a back cavity with an opening downward formed by patterning and etching the middle of the processed silicon substrate, wherein a metal reflection layer is arranged in the back cavity. A cavity is formed by enclosing the processed silicon substrate, the metal reflection layer, and the infrared absorption layer, and the cavity is an optical resonant cavity. Infrared rays are focused to the infrared absorption layer at the hot end of the thermopile infrared detector through a lens, a part of the infrared rays are absorbed by the infrared absorption layer, a part of the infrared rays may pass through the infrared absorption layer and then be incident on the metal reflection layer, and then be reflected back to the infrared absorption layer, so that the infrared rays reaching the infrared absorption layer and the infrared rays reflected back by the reflection surface of the metal reflection layer just form an optical path difference of about 1 / 2 in the infrared absorption layer, thereby forming a standing wave effect, so that the infrared rays focused on the infrared absorption layer at the hot end are absorbed as much as possible. The infrared absorption rate is greatly improved, thereby increasing the response rate and detection rate of the thermopile infrared detector, and greatly reducing the noise equivalent temperature difference of the thermopile infrared detector.

[0090] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A thermopile infrared detector, characterized in that: The invention comprises a processed silicon substrate, an infrared absorption layer arranged on the processed silicon substrate, a back cavity with an opening facing downward formed by patterning and etching the middle of the processed silicon substrate, wherein a metal reflection layer is arranged in the back cavity; a cavity is formed by enclosing the processed silicon substrate, the metal reflection layer and the infrared absorption layer, and the cavity is an optical resonant cavity; wherein a support layer is arranged in the back cavity along the back side of the metal reflection layer to support the metal reflection layer; Wherein, a plurality of patterned thermocouple first materials are arranged on the infrared absorption layer, and the spacing distance between each adjacent two thermocouple first materials in the plurality of thermocouple first materials is a preset distance; an isolation film is covered on the plurality of thermocouple first materials and the infrared absorption layer; two contact holes are arranged on the top contact surface of the isolation film and each thermocouple first material, and a thermopile second material is arranged on the two adjacent contact holes on each adjacent two thermocouple first materials in all the contact holes and on a part of the isolation film between the two adjacent contact holes to form a metal thermopile interconnection pattern, a passivation layer is arranged on the surface of the thermopile second material, and a plurality of line holes are arranged on the passivation layer; wherein, a line hole is arranged on the passivation layer between each adjacent two thermopile second materials.

2. The thermopile infrared detector according to claim 1, characterized in that: The thickness of the optical resonant cavity is not less than 1 μm.

3. The thermopile infrared detector according to claim 2, characterized in that: The material of the support layer is silicon oxide and / or silicon nitride.

4. The thermopile infrared detector according to claim 1, characterized in that: The processed silicon substrate includes: an original silicon substrate, a first composite edge portion and a second composite edge portion of a first composite film arranged on the original silicon substrate, a first sacrificial edge portion of a sacrificial layer arranged on the first composite edge portion, and a second sacrificial edge portion of the sacrificial layer arranged on the second composite edge portion.

5. A method for preparing a thermopile infrared detector, characterized in that: The method comprises: providing an infrared absorption layer on the processed silicon substrate; Patterning and etching the middle portion of the processed silicon substrate to form a back cavity with an opening facing downward; A metal reflective layer is arranged in the back cavity, and a cavity is formed by enclosing the processed silicon substrate, the metal reflective layer and the infrared absorption layer, and the cavity is an optical resonant cavity; Wherein, before forming the back cavity with the opening downward, the method further comprises: Arranging a thermopile first material on the infrared absorption layer and patterning it to form a plurality of patterned thermocouple first materials, wherein the spacing distance between each two adjacent thermocouple first materials in the plurality of thermocouple first materials is a preset distance; An isolation film is covered on the plurality of thermocouple first materials and the infrared absorption layer; two contact holes are provided on the top contact surface between the isolation film and each of the thermocouple first materials; The second thermopile material is disposed on two adjacent contact holes on each adjacent two thermocouple first materials in all the contact holes and on a portion of the isolation film between the two adjacent contact holes to form a metal thermopile interconnection pattern; A passivation layer is arranged on the surface of the second material of the thermopile and patterned; a plurality of line holes are arranged on the patterned passivation layer; wherein one line hole is arranged on the passivation layer between each two adjacent second materials of the thermopile.

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