Infrared thermopile device and preparation method thereof

Abstract

The invention provides an infrared thermopile device and a preparation method, the device comprises a substrate, a device layer, a metal reflection structure, an amorphous silicon structure and a cylinder structure, and the cylinder structure comprises a plurality of cylinder units arranged periodically. Each cylinder unit comprises a first wave-absorbing cylinder, and the cross section of the first wave-absorbing cylinder is a rotationally symmetrical graph, so that the absorptivity of the device to infrared waves is improved, and meanwhile, the sensitivity of the device to the incident angle and polarization of infrared light is reduced. And the metal reflection structure reflects the infrared light penetrating through the cylinder structure and the amorphous silicon structure back to the cylinder structure, so that the cylinder structure performs secondary absorption on the penetrating infrared light, and the absorption rate of the device on the infrared light is further improved. And finally, the amorphous silicon structure, the cylinder structure and the metal layer respectively form laminated structures with different complex refractive indexes, and space impedance matching is formed, so that the absorptivity of the device to the infrared light of the specific wave band is further improved, and the absorption bandwidth of the infrared light is widened.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to an infrared thermopile device and its fabrication method. Background Technology

[0002] Infrared thermopile devices are common temperature sensors widely used in non-contact body temperature measurement and human body sensing. They sense infrared signals, absorb infrared radiation, and form a temperature difference on the sensor. Then, through the Seebeck effect, the difference is converted into a voltage signal to measure the temperature.

[0003] As the distance increases, the loss of infrared radiation during propagation gradually increases. In order to enhance signal strength and sensitivity, an absorption layer material (such as carbon black / platinum black) is usually coated in the sensitive area to enhance infrared absorption. Its thickness is generally in the micrometer range.

[0004] However, the absorber layer material in sensitive areas is usually applied using an additional coating process or screen printing, which can lead to peeling after prolonged use. Furthermore, currently used absorber layer materials cannot selectively absorb specific wavelengths of infrared light and typically require the use of filters to absorb specific wavelengths of infrared light. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an infrared thermopile device and its fabrication method, enabling a high-sensitivity and high-signal-to-noise ratio thermopile infrared sensor for a specific wavelength at a low cost.

[0006] According to a first aspect of the present invention, an infrared thermopile device is provided, the device comprising: A substrate having opposing first and second surfaces, wherein the substrate has a cavity opening exposed by the first surface; A device layer located on a second side of the substrate, the device layer including at least one set of thermocouples; A metal reflective structure, wherein the metal reflective structure is located on the device layer; An amorphous silicon structure is located on the metal reflective structure, and the projection of the metal reflective structure onto the substrate surface and the projection of the amorphous silicon structure onto the substrate surface are both located within the cavity. A columnar structure is located on the surface of the amorphous silicon structure. The columnar structure includes several periodically arranged columnar units, and each columnar unit includes a first absorbing column. The cross-sectional shape of the first absorbing column is rotationally symmetric.

[0007] Optionally, the cross-sectional shape of the first absorbing column includes at least a square, a circle, and a regular hexagon.

[0008] Optionally, the bottom area of ​​the first absorbing column is 0.34 μm. 2 ~0.43 μm 2 The height of the first absorbing column is between 650 nm and 750 nm.

[0009] Optionally, the column unit further includes two or more second absorbing columns, the cross-sectional shape of the second absorbing column is a rotationally symmetric shape, and the two or more second absorbing columns are evenly distributed on a circle with the first absorbing column as the center.

[0010] Optionally, the rotational degree of the second absorbing columns spaced apart from each other includes at least 45°, 60° or 90°.

[0011] Optionally, the bottom area of ​​the second absorbing column is 0.048 μm. 2 ~0.078 μm 2 The height of the second absorbing column is between 650 nm and 750 nm.

[0012] Optionally, the minimum spacing between the first absorbing column and the second absorbing column is between 160 nm and 200 nm.

[0013] Optionally, the thickness of the metal reflective structure is between 100 nm and 200 nm, and the thickness of the amorphous silicon structure is between 360 nm and 420 nm.

[0014] Optionally, a passivation layer is also included, which covers the pillar structure, the amorphous silicon structure and the first isolation layer, and exposes the electrical connection structure, wherein the height difference between the surface of the passivation layer and the upper surface of the first absorbing pillar is between 30 nm and 60 nm.

[0015] According to a second aspect of the present invention, a method for fabricating an infrared thermopile device is provided, the method comprising: A substrate is provided, the substrate having opposing first and second surfaces; A device layer is formed on a second surface of the substrate, the device layer including at least one set of thermocouples; A metal reflective structure is formed on the device layer; An amorphous silicon structure is formed on the metal reflective structure, and the amorphous silicon structure is located on the metal reflective structure; A columnar structure is formed on the amorphous silicon structure. The columnar structure is located on the surface of the amorphous silicon structure. The columnar structure includes a plurality of periodically arranged columnar units. Each columnar unit includes a first absorbing column. The cross-sectional shape of the first absorbing column is rotationally symmetric. After forming a pillar structure on the amorphous silicon structure, the substrate is etched from the first surface to form a cavity opening exposed by the first surface in the substrate. The projection of the metal reflective structure on the substrate surface and the projection of the amorphous silicon structure on the substrate surface are both located within the range of the cavity opening.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: In the infrared thermopile device provided by this invention, after fabricating a device layer on a substrate, a metal reflective structure, an amorphous silicon structure, and a pillar structure are sequentially stacked on the device layer. The pillar structure includes several periodically arranged pillar units. Each pillar unit includes a first absorbing pillar with a rotationally symmetric cross-sectional shape to improve the device's absorption rate of infrared waves while reducing the device's sensitivity to the incident angle and polarization mode of infrared light. The metal reflective structure reflects the infrared light that penetrates the pillar structure and the amorphous silicon structure back to the pillar structure, allowing the pillar structure to perform secondary absorption of the penetrated infrared light, thereby further improving the device's absorption rate of infrared light. Finally, the amorphous silicon structure, the pillar structure, and the metal layer respectively form a stacked structure with different complex refractive indices, achieving spatial impedance matching. This not only further improves the device's absorption rate of infrared light in the specific wavelength band but also broadens the infrared light absorption bandwidth.

[0017] Furthermore, this invention integrates a wave-absorbing enhancement structure consisting of a metal reflective structure, an amorphous silicon structure, and a columnar structure into an infrared thermopile device, thus not only avoiding an increase in device size but also eliminating the need for additional processing methods.

[0018] In summary, this invention improves the absorption rate and absorption bandwidth of infrared light while maintaining cost and device size.

[0019] Furthermore, the column unit also includes two or more second absorbing columns, the cross-sectional shape of the first absorbing column is rotationally symmetric, and the two or more second absorbing columns are evenly distributed on a circle with the first absorbing column as the center, thereby further improving the absorption rate of infrared light by the device. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figures 1 to 15 These are schematic cross-sectional views of the infrared thermopile device fabrication method provided in the first embodiment of the present invention under different process steps. Figure 16 A cross-sectional structural schematic diagram of an infrared thermopile device provided in the second embodiment of the present invention; Figure 17 A top view of the cylindrical unit in an infrared thermopile device provided in the second embodiment of the present invention; Figure 18 The infrared light absorption rate curve of the infrared thermopile device provided in the second embodiment of the present invention compared with that of existing infrared thermopile devices. Figure 1 ; Figure 19 The curves showing the absorption rate of infrared light by the infrared thermopile device provided in the second embodiment of the present invention as a function of wavelength at different incident angles. Figure 1 ; Figure 20 The curves showing the absorption rate of infrared light by the infrared thermopile device provided in the second embodiment of the present invention as a function of wavelength at different incident angles. Figure 2 .

[0022] A1 - First page; A2 - Second page; 100-substrate; 110 - Bottom support structure; 111 - First support layer; 112 - Second support layer; 113 - Third support layer; 120 - First polycrystalline silicon structure; 130 - First isolation layer; 140 - Second polycrystalline silicon structure; 150 - Second isolation layer; 160 - Third mask layer; 171 - First contact hole; 172 - Second contact hole; 180-Metallic layer; 181 - Metallic interconnect structure; 182 - Metallic reflective structure; 190 - Third isolation layer; 200-Amorphous silicon layer; 201-Amorphous silicon structure; 210 - Columnar structure; 211 - First absorbing column; 212 - Second absorbing column; 220 - Passivation layer; 230 - Cavity opening. Detailed Implementation

[0023] As described in the background section, as the distance increases, the loss of infrared radiation during propagation gradually increases. In order to enhance signal strength and sensitivity, an absorption layer material (such as carbon black / platinum black) is usually coated in the sensitive area to enhance infrared absorption. Its thickness is generally in the micrometer range.

[0024] However, the absorber layer material in sensitive areas is usually applied using an additional coating process or screen printing, which can lead to peeling after prolonged use. Furthermore, currently used absorber layer materials cannot selectively absorb specific wavelengths of infrared light and typically require the use of filters to absorb specific wavelengths of infrared light.

[0025] In view of this, the technical solution of the present invention provides a new infrared thermopile device, including a substrate, a device layer, a metal reflective structure, an amorphous silicon structure, and a pillar structure; by additionally integrating the metal reflective structure, the amorphous silicon structure, and the pillar structure in sequence on the basis of a conventional infrared thermopile, the absorption rate and absorption bandwidth of the device for infrared light are improved without increasing the cost and device size.

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0029] Before introducing the infrared thermopile device provided in this embodiment, the fabrication process of the infrared thermopile device will be described in detail: [First Embodiment] Figures 1 to 15 These are schematic cross-sectional views of the infrared thermopile device fabrication method provided in this embodiment under different process steps.

[0030] This embodiment provides a method for fabricating an infrared thermopile device, which specifically includes the following steps: Please refer to Figure 1 S1: Provide a substrate 100 having opposing first surfaces A1 and second surfaces A2.

[0031] Please refer to Figure 2 S2: A bottom support structure 110 is formed on the second surface A2 of the substrate 100.

[0032] Specifically, the formation of the bottom support structure 110 on the second surface A2 of the substrate 100 in S2 involves the following steps: Please continue to refer to this. Figure 2 A first support layer 111, a second support layer 112, and a third support layer 113 are sequentially deposited on the second surface A2 of the substrate 100.

[0033] Furthermore, the first support layer 111, the second support layer 112, and the third support layer 113 can all be made of silicon dioxide, silicon nitride, or silicon oxynitride, and no limitation is made here.

[0034] S3: A device layer is formed on the surface of the bottom support structure 110, the device layer including at least one set of thermocouples.

[0035] Specifically, the process of forming a device layer on the surface of the bottom support structure 110 in S3 includes the following steps: S31: A first polycrystalline silicon layer is deposited on the surface of the third support layer 113.

[0036] S32: A patterned first mask layer is formed on the surface of the first polysilicon layer, the first mask layer including a first polysilicon barrier region and an etched region.

[0037] S33: Using the patterned first mask layer as a mask, the first polysilicon layer is etched, with the etching endpoint stopping on the surface of the third support layer 113 to form the first polysilicon structure 120, as shown. Figure 3 As shown.

[0038] S34: A first isolation layer 130 is deposited on the surface of the first polysilicon structure 120 and the surface of the first support layer 111, and the surfaces of the first isolation layer 130 are on the same horizontal plane, such as... Figure 4 As shown.

[0039] Specifically, the material of the first isolation layer 130 includes any one of silicon dioxide, silicon nitride, or silicon oxynitride, without limitation.

[0040] S35: Deposit a second polysilicon layer on the surface of the first isolation layer 130.

[0041] S36: A patterned second mask layer is formed on the surface of the second polysilicon layer, the second mask layer including a second polysilicon barrier region and an etched region.

[0042] Specifically, the area of ​​the second polysilicon barrier region is smaller than the surface area of ​​the first polysilicon structure 120, and the projection of the second polysilicon barrier region onto the surface of the third support layer 113 is located within the first polysilicon structure 120.

[0043] S37: Using the patterned second mask layer as a mask, the second polysilicon layer is etched, with the etching endpoint stopping at the surface of the first isolation layer 130 to form the second polysilicon structure 140, as shown. Figure 5 As shown.

[0044] Specifically, the second polysilicon structure 140, the first isolation layer 130, and the first polysilicon structure 120 constitute a set of thermocouples.

[0045] S38: A second isolation layer 150 is deposited on the surface of the second polysilicon structure 140 and the surface of the first isolation layer 130, and the surfaces of the second isolation layer 150 are on the same horizontal plane, such as... Figure 6 As shown.

[0046] Specifically, the material of the second insulating layer 150 includes any one of silicon dioxide, silicon nitride, or silicon oxynitride, without limitation.

[0047] After completing the fabrication of the second isolation layer 150, S4: fabricate the metal interconnect structure and the metal reflection structure.

[0048] Specifically, step S4, which involves fabricating the metal interconnect structure and the metal reflection structure, includes the following steps: S41: A patterned third mask layer is formed on the surface of the second isolation layer 150. The third mask layer includes a metal interconnect etched area and a blocking area. The metal interconnect etched areas correspond to the surfaces of the first polysilicon structure 120 and the second polysilicon structure 140, respectively.

[0049] S42: Using the patterned third mask layer 160 as a mask, etch the second isolation layer 150 and the first isolation layer 130, with the etching endpoint stopping at the surface of the first polysilicon structure 120 to form the first contact hole 171. Then etch the second isolation layer 150, with the etching endpoint stopping at the surface of the second polysilicon structure 140 to form the second contact hole 172. Figure 7 As shown.

[0050] Specifically, taking the example that both the first isolation layer 130 and the second isolation layer 150 are made of silicon dioxide, the etching gas is set to have a high etching selectivity for silicon dioxide compared to polysilicon, so that the etching of the second isolation layer 150 can stop on the surface of the second polysilicon structure 140 to form the second contact hole 172, and the first isolation layer 130 is etched, so that the etching endpoint stops on the surface of the first polysilicon structure 120 to form the first contact hole 171.

[0051] S43: Deposit metal to fill the first contact hole 171 and the second contact hole 172, and form a metal layer 180 on the surface of the second insulating layer 150, such as Figure 8 As shown.

[0052] Specifically, the material of the metal layer 180 includes tungsten, aluminum, copper, or other alloys, and is not limited thereto.

[0053] S44: A patterned fourth mask layer is formed on the surface of the metal layer 180. The fourth mask layer includes a metal interconnect structure 181 blocking region, a metal reflection structure blocking region, and an etched region. The projections of the metal reflection blocking region and the first polysilicon structure 120 onto the third support layer 113 do not intersect.

[0054] S45: Using the fourth mask layer as a mask, the metal layer 180 is etched to form the metal interconnect structure 181 and the metal reflective structure 182, such as... Figure 9 As shown.

[0055] The metal interconnect structure 181 is used to bring out the first polysilicon structure 120 and the second polysilicon structure 140. The thickness of the metal reflective structure 182 is between 100 nm and 200 nm.

[0056] Please refer to Figure 10 After completing the fabrication of the metal interconnect structure 181 and the metal reflective structure 182, S5: deposit a third isolation layer 190 on the surface of the second isolation layer 150, the surface of the metal interconnect structure 181 and the surface of the metal reflective structure 182.

[0057] Specifically, the material of the third isolation layer 190 is the same as that of the second isolation layer 150 and the first isolation layer 130, and will not be described again here. The third isolation layer 190 is used to isolate the subsequently fabricated amorphous silicon structure 201 and pillar structure 210 from the metal reflective structure 182 to prevent leakage.

[0058] S6: Deposit an amorphous silicon layer 200 on the surface of the third isolation layer 190, such as Figure 10 As shown.

[0059] Specifically, the thickness of the amorphous silicon layer 200 is between 360nm and 420nm.

[0060] S7: A patterned fifth mask layer is formed on the surface of the amorphous silicon layer 200. The fifth mask layer includes an amorphous silicon structure blocking region and an etched region. The amorphous silicon structure blocking region and the metal reflective structure 182 are vertically opposite each other.

[0061] S8: Using the patterned fifth mask layer as a mask, the amorphous silicon layer 200 is etched, with the etching endpoint stopping at the surface of the third isolation layer 190 to form the amorphous silicon structure 201, as shown. Figure 11 As shown.

[0062] Specifically, taking silicon dioxide as an example of the third isolation layer 190, the etching gas is configured to have a high etching selectivity for amorphous silicon compared to silicon dioxide, so that the etching of the amorphous silicon layer 200 can remain on the surface of the third isolation layer 190.

[0063] S9: Deposit a silicon dioxide layer on the surface of the third isolation layer 190 and the amorphous silicon structure 201.

[0064] Specifically, the thickness of the silicon dioxide layer is between 650 and 750 nm.

[0065] S10: A patterned sixth mask layer is formed on the surface of the silicon dioxide layer. The sixth mask layer includes a plurality of spaced-apart pillar structure blocking regions and etching regions, each pillar structure blocking region being a rotationally symmetric pattern. Furthermore, the plurality of periodically arranged pillar unit blocking regions all fall within the range of the amorphous silicon structure 201.

[0066] S11: Using the sixth mask layer as a mask, the silicon dioxide layer is etched to form the pillar structure 210, such as... Figure 12 As shown.

[0067] Specifically, the column structure 210 includes a plurality of spaced-apart first absorbing columns 211 to improve the absorption rate of the device for infrared waves. Furthermore, because the cross-sectional shape of the first absorbing column 211 is rotationally symmetric, its sensitivity to the incident angle and polarization mode of infrared light is reduced.

[0068] Specifically, the material of the first absorbing column 211 is silicon dioxide.

[0069] S12: Deposit a passivation layer 220 on the surface of the third isolation layer 190, the surface of the amorphous silicon structure 201, and the surface of the pillar structure 210, such as Figure 13 As shown.

[0070] Specifically, the passivation layer 220 is made of silicon nitride, and the height difference between the surface of the passivation layer 220 and the upper surface of the first absorbing column 211 is between 30 nm and 60 nm.

[0071] S13: A patterned seventh mask layer is formed on the surface of the passivation layer 220. The seventh mask layer includes a metal interconnect structure etching area and a blocking area, with the metal interconnect structure etching area and the metal interconnect structure being vertically opposite each other.

[0072] S14: Using the seventh mask layer as a mask, etch the passivation layer 220 until the etching endpoint stops at the metal interconnect structure, thus exposing the metal interconnect structure. Figure 14 As shown.

[0073] S15: After exposing the metal interconnect structure, the substrate 100 is flipped over, and the substrate 100 is etched from its first surface A1 to form a cavity opening 230 exposed by the first surface A1 within the substrate 100, such as... Figure 15 As shown.

[0074] Specifically, the projection of the metal reflective structure 182 onto the surface of the substrate 100 and the projection of the amorphous silicon structure 201 onto the surface of the substrate 100 are both located within the cavity.

[0075] The above describes the fabrication method of the infrared thermopile device provided in this embodiment. The structure of the infrared thermopile device provided in this embodiment will be described in detail below.

[0076] Please refer to Figure 15 Based on the above-mentioned method for fabricating infrared thermopile devices, the infrared thermopile device provided in this embodiment includes: a substrate 100, a bottom support structure 110, a device layer, a metal interconnect structure 181, a metal reflective structure 182, a third isolation layer 190, an amorphous silicon structure 201, a pillar structure 210, and a passivation layer 220.

[0077] The substrate 100 has a first surface A1 and a second surface A2 opposite to each other. The substrate 100 has a cavity opening 230 exposed by the first surface A1. The cavity opening 230 is sealed by subsequent thin film deposition sealing, wafer bonding sealing, or cap sealing.

[0078] The bottom support structure 110 is located on the second surface A2 of the substrate 100.

[0079] The device layer is located on the surface of the bottom support structure 110, and the device layer is composed of a first polysilicon structure 120, a first isolation layer 130, a second polysilicon structure 140 and a second isolation layer 150 stacked in sequence.

[0080] The metal interconnect structure 181 is located on the second isolation layer 150 and leads out the first polysilicon structure 120 and the second polysilicon structure 140.

[0081] The metal reflective structure 182 is also located on the second isolation layer 150, and the projections of the metal reflective structure 182 and the first polysilicon structure 120 on the bottom support structure 110 do not intersect.

[0082] The third isolation layer 190 is located on the surface of the second isolation layer 150, the surface of the metal interconnect structure 181, and the surface of the metal reflective structure 182.

[0083] The amorphous silicon structure 201 is located on the metal reflective structure 182 and on the third isolation layer 190.

[0084] The column structure 210 is located on the surface of the amorphous silicon structure 201. The column structure 210 includes a plurality of periodically arranged column units, each column unit including a first absorbing column 211, the cross-sectional shape of the first absorbing column 211 being rotationally symmetric.

[0085] The passivation layer 220 is deposited on the surface of the third isolation layer 190, the surface of the amorphous silicon structure 201, and the surface of the pillar structure 210.

[0086] In this embodiment, the metal reflective structure 182, the amorphous silicon structure 201, and the pillar structure 210 are all integrated into the infrared thermopile device, so not only is the device size not increased, but no additional processing methods are required.

[0087] Since the specific composition and material selection of the bottom support structure 110, metal connection structure 181, metal reflection structure 182, third isolation layer 190, amorphous silicon structure 201, column structure 210 and passivation layer 220 have been explained, they will not be repeated here.

[0088] First, the columnar structure 210 includes spaced-apart first absorbing columns 211, and the cross-sectional shape of the first absorbing columns 211 includes at least squares, circles, and regular hexagons. This not only enhances the absorption rate of the fabricated device for infrared light but also reduces its sensitivity to incident angle and polarization. Furthermore, the base area of ​​the first absorbing column 211 is 0.4 μm. 2 The height of the first absorbing column 211 is 700 nm. Of course, in other embodiments, the base area of ​​the first absorbing column 211 can be set to 0.34 μm. 2 ~0.43 μm 2 The height of the first absorbing column 211 can be set between 650 nm and 750 nm.

[0089] Secondly, the metal reflective structure 182 reflects the infrared light that penetrates the pillar structure 210 and the amorphous silicon structure 201 back to the pillar structure 210, so that the pillar structure 210 performs secondary absorption of the penetrated infrared light, thereby further improving the absorption rate of the device for infrared light. Furthermore, in this embodiment, the thickness of the metal reflective layer is set to 100 nm. Of course, in other embodiments, the metal reflective layer can also be set between 100 nm and 200 nm.

[0090] Finally, the amorphous silicon structure 201, the pillar structure 210, and the metal layer 180 form a stacked structure with different complex refractive indices, achieving spatial impedance matching. This not only further improves the absorption rate of the device for the aforementioned specific wavelength of infrared light but also broadens the absorption bandwidth of infrared light. Furthermore, in this embodiment, the layer thickness of the amorphous silicon structure 201 is set to 380 nm. Of course, in other embodiments, the layer thickness of the amorphous silicon structure 201 can also be set between 360 nm and 420 nm.

[0091] In this embodiment, the height difference between the surface of the passivation layer 220 and the upper surface of the first absorbing column 211 is between 30 nm and 60 nm.

[0092] In summary, in the infrared thermopile device provided in this embodiment, after fabricating a device layer on a substrate, a metal reflective structure, an amorphous silicon structure, and a pillar structure are sequentially stacked on the device layer. The pillar structure includes several periodically arranged pillar units. Each pillar unit includes a first absorbing pillar with a rotationally symmetric cross-sectional shape to improve the device's absorption rate of infrared waves while reducing the device's sensitivity to the incident angle and polarization mode of infrared light. The metal reflective structure reflects the infrared light that penetrates the pillar structure and the amorphous silicon structure back to the pillar structure, allowing the pillar structure to perform secondary absorption of the penetrated infrared light, thereby further improving the device's absorption rate of infrared light. Finally, the amorphous silicon structure, the pillar structure, and the metal layer respectively form a stacked structure with different complex refractive indices, achieving spatial impedance matching. This not only further improves the device's absorption rate of infrared light in the specific wavelength band but also broadens the infrared light absorption bandwidth.

[0093] Furthermore, this invention integrates the metal reflective structure, the amorphous silicon structure, and the pillar structure into the infrared thermopile device, thus not only avoiding an increase in device size but also eliminating the need for additional processing methods.

[0094] [Second Embodiment] This embodiment provides a method for fabricating an infrared thermopile device, which differs from the first embodiment in that: S11: Using the sixth mask layer as a mask, the silicon dioxide layer is etched to form the pillar structure 210, such as... Figure 16 As shown.

[0095] Specifically, the column structure 210 includes several column units arranged at intervals, and each column unit includes a first absorbing column 211 and two or more second absorbing columns 212, in order to improve the absorption rate of infrared waves by the device.

[0096] Specifically, the first absorbing column 211 and the second absorbing column 212 are made of silicon dioxide.

[0097] S12: Deposit a passivation layer 220 on the surface of the third isolation layer 190, the surface of the amorphous silicon structure 201, and the surface of the pillar structure 210, such as Figure 13 As shown.

[0098] Specifically, the passivation layer 220 is made of silicon nitride, and the height difference between the surface of the passivation layer 220 and the upper surfaces of the first absorbing column 211 and the second absorbing column 212 is between 30 nm and 60 nm.

[0099] The above describes the fabrication method of the infrared thermopile device provided in this embodiment. The structure of the infrared thermopile device provided in this embodiment will be described in detail below.

[0100] Figure 16 A cross-sectional structural schematic diagram of the infrared thermopile device provided in this embodiment. Figure 17 This is a top view of the cylindrical unit in the infrared thermopile device provided in this embodiment.

[0101] Please refer to Figure 16 and Figure 17 Unlike the first embodiment, the column unit, in addition to a single first absorbing column 211, also includes two or more second absorbing columns 212. The cross-sectional shape of the first absorbing column 211 is rotationally symmetric, and the two or more second absorbing columns 212 are evenly distributed on a circle centered on the first absorbing column 211, with a rotational interval of 45° between them. Of course, in other embodiments, this rotational interval of the second absorbing columns 212 can also be set to 60°, 90°, or other degrees, as long as the rotational interval ensures that the second absorbing columns 212 are evenly distributed on a circle centered on the first absorbing column 211, it falls within the protection scope of this embodiment.

[0102] Furthermore, the material of the second absorbing column 212 is also silicon dioxide.

[0103] Furthermore, the cross-sectional shape of the second absorbing column 212 also includes at least a square, a circle, and a regular hexagon.

[0104] Furthermore, the bottom area of ​​the second absorbing column 212 is 0.048 μm. 2 ~0.078 μm 2 The height of the second absorbing column 212 is between 650 nm and 750 nm. The minimum distance between the first absorbing column 211 and the second absorbing column 212 is between 160 nm and 200 nm.

[0105] Based on a single first absorbing column 211, the column unit additionally includes several second absorbing columns 212 with rotationally symmetric cross-sectional shapes, all located on a circle centered on the first absorbing column 211, with rotational intervals between them including 45°. Therefore, the overall shape formed by the single first absorbing column 211 and two or more second absorbing columns 212 is also rotationally symmetric. Furthermore, because the number of first absorbing columns is the largest, the absorption rate of the device for infrared light is further increased without increasing the device's sensitivity to the incident angle and polarization mode of infrared light.

[0106] In one specific embodiment, the column unit includes one first absorbing column 211 and eight second absorbing columns 212, and the eight second absorbing columns 212 are evenly distributed on a circle with the first absorbing column 211 as the center, and the rotation degree between them includes 45°.

[0107] Please refer to Figure 18 , Figure 18 The graph shows the infrared light absorption rate of the infrared thermopile device provided in this embodiment compared to the device without a pillar structure. The graph indicates the structure without a pillar structure and the structure with a pillar structure. As can be seen from the graph, the infrared thermopile device provided in this embodiment has an absorption rate exceeding 80% for infrared light in the 8 μm to 16 μm range, while existing infrared thermopile devices struggle to maintain both high absorption rate and sufficient absorption bandwidth.

[0108] Please refer to Figure 19 , Figure 19 The curves showing the absorption rate of infrared light by the infrared thermopile device provided in this embodiment as a function of wavelength at different incident angles. Figure 1 In this embodiment, TM polarization is set, that is, the magnetic field direction is perpendicular to the incident surface of infrared light, and infrared light is incident on the column structure 210 at incident angles of 0°, 15° and 30° respectively. It can be seen that as the wavelength of infrared light changes, the absorption rate of infrared light provided in this embodiment for infrared light at different incident angles remains basically unchanged, and it can still maintain an absorption rate of over 80% for infrared light between 8 μm and 16 μm.

[0109] like Figure 20 As shown, Figure 20 The curves showing the absorption rate of infrared light by the infrared thermopile device provided in this embodiment as a function of wavelength at different incident angles. Figure 2In other embodiments, TE polarization is set, that is, the electric field direction is perpendicular to the incident surface of infrared light, and infrared light is incident on the column structure 210 at incident angles of 0°, 15° and 30° respectively. It can be seen that as the wavelength of infrared light changes, the absorption rate of infrared light by the infrared thermopile device provided in this embodiment for infrared light at different incident angles is basically unchanged, and the absorption rate of infrared light by the infrared thermopile device provided in this embodiment for infrared light with different polarizations is also roughly the same.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An infrared thermopile device, characterized in that, The device includes: A substrate having opposing first and second surfaces, wherein the substrate has a cavity opening exposed by the first surface; A device layer located on a second side of the substrate, the device layer including at least one set of thermocouples; A metal reflective structure, wherein the metal reflective structure is located on the device layer; An amorphous silicon structure is located on the metal reflective structure, and the projection of the metal reflective structure onto the substrate surface and the projection of the amorphous silicon structure onto the substrate surface are both located within the cavity. A columnar structure is located on the surface of the amorphous silicon structure. The columnar structure includes several periodically arranged columnar units, and each columnar unit includes a first absorbing column. The cross-sectional shape of the first absorbing column is rotationally symmetric.

2. The infrared thermopile device according to claim 1, characterized in that, The cross-sectional shape of the first absorbing column includes at least a square, a circle, and a regular hexagon.

3. The infrared thermopile device according to claim 1, characterized in that, The bottom area of ​​the first absorbing column is 0.34 μm. 2 ~0.43 μm 2 The height of the first absorbing column is between 650 nm and 750 nm.

4. The infrared thermopile device according to claim 1, characterized in that, The column unit further includes two or more second absorbing columns, and the two or more second absorbing columns are evenly distributed on a circle with the first absorbing column as the center.

5. The infrared thermopile device according to claim 4, characterized in that, The rotational degree of the second absorbing columns between each other includes at least 45°, 60° or 90°.

6. The infrared thermopile device according to claim 4, characterized in that, The bottom area of ​​the second absorbing column is 0.048 μm. 2 ~0.078 μm 2 The height of the second absorbing column is between 650 nm and 750 nm.

7. The infrared thermopile device according to claim 4, characterized in that, The minimum spacing between the first absorbing column and the second absorbing column is between 160 nm and 200 nm.

8. The infrared thermopile device according to claim 1, characterized in that, The thickness of the metal reflective structure is between 100 nm and 200 nm, and the thickness of the amorphous silicon structure is between 360 nm and 420 nm.

9. The infrared thermopile device according to claim 1, characterized in that, It also includes a passivation layer that covers the pillar structure, the amorphous silicon structure and the first isolation layer, and exposes the electrical connection structure. The height difference between the surface of the passivation layer and the upper surface of the first absorbing pillar is between 30 nm and 60 nm.

10. A method for fabricating an infrared thermopile device, characterized in that, The method includes: A substrate is provided, the substrate having opposing first and second surfaces; A device layer is formed on a second surface of the substrate, the device layer including at least one set of thermocouples; A metal reflective structure is formed on the device layer; An amorphous silicon structure is formed on the metal reflective structure, and the amorphous silicon structure is located on the metal reflective structure; A columnar structure is formed on the amorphous silicon structure. The columnar structure is located on the surface of the amorphous silicon structure. The columnar structure includes a plurality of periodically arranged columnar units. Each columnar unit includes a first absorbing column. The cross-sectional shape of the first absorbing column is rotationally symmetric. After forming a pillar structure on the amorphous silicon structure, the substrate is etched from the first surface to form a cavity opening exposed by the first surface in the substrate. The projection of the metal reflective structure on the substrate surface and the projection of the amorphous silicon structure on the substrate surface are both located within the range of the cavity opening.

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