An infrared thermopile sensing device

Abstract

The present application provides an infrared thermopile sensor device, which includes a thermopile sensor formed on a base layer, the thermopile sensor including an absorption region, a cavity formed on the base layer, the absorption region suspended over the cavity of the base layer, the absorption region including a first metal layer, a dielectric layer and a second metal layer stacked, the first metal layer closer to the cavity of the base layer than the second metal layer, the dielectric layer of the absorption region between the first metal layer and the second metal layer, the second metal layer of the absorption region patterned to form a predetermined pattern. In this way, the infrared absorption rate is enhanced by making the metal layer into a predetermined pattern, the specific wavelength absorption rate is adjusted, and thus the performance of the infrared thermopile sensor device is improved.

Description

Technical field

[0001] The present invention belongs to the technical field of infrared detectors, and in particular relates to an infrared thermopile sensing device based on CMOS technology. [Background Technology]

[0002] Existing MEMS (Micro-Electro-Mechanical System) thermopile structures are mostly based on specialized MEMS processes, making it impossible to integrate sensors and processing circuits on a single chip. This is not conducive to the development of low-cost, high-integration technologies. Furthermore, thermopiles manufactured using standard CMOS (Complementary Metal Oxide Semiconductor) processes have a narrow window for adjusting film thickness and materials due to the limitations of the standard CMOS process. This results in low infrared absorption and a central absorption wavelength that does not match application requirements.

[0003] Therefore, it is necessary to propose a technical solution to overcome the above problems. [Summary of the invention]

[0004] One of the objectives of the present invention is to provide an infrared thermopile sensor device that can not only be manufactured using a COMS process but also can improve or adjust the infrared absorption rate of a specific wavelength.

[0005] According to one aspect of the present invention, the present invention provides an infrared thermopile sensing device, which includes a thermopile sensor formed based on a base layer, the thermopile sensor including an absorption region, a cavity formed on the base layer, the absorption region suspended above the cavity of the base layer, the absorption region including a stacked first metal layer, a dielectric layer, and a second metal layer, the first metal layer being closer to the cavity of the base layer than the second metal layer, the dielectric layer of the absorption region being located between the first metal layer and the second metal layer, and the second metal layer of the absorption region being patterned to form a predetermined pattern.

[0006] Compared with the prior art, the infrared thermopile sensor device of the present invention enhances the infrared absorption rate by making the metal layer of the CMOS process into a predetermined pattern, adjusts the absorption rate of a specific wavelength, and thus improves the performance of the infrared thermopile sensor device.

Brief Description of the Drawings

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0008] Figure 1 FIG1 is a top view of an infrared thermopile sensor device based on CMOS technology in one embodiment of the present invention;

[0009] Figure 2 is a schematic longitudinal cross-sectional view of an infrared thermopile sensor device based on CMOS technology in one embodiment of the present invention;

[0010] Figure 3 is a schematic longitudinal cross-sectional view of an infrared thermopile sensor device based on CMOS technology in another embodiment of the present invention;

[0011] Figure 4 for Figure 2 A magnified view of the absorption region of the thermopile sensor in FIG.

[0012] Figure 5 FIG1 is a top view of an infrared thermopile sensor device based on CMOS technology in another embodiment of the present invention;

[0013] Figure 6 A comparison diagram of the spectral absorption rate of a thermopile sensor with and without an enhanced absorption structure in one embodiment of the present invention;

[0014] Figure 7 FIG1 is a comparison diagram showing the effect of temperature distribution on the absorption region of a thermopile sensor in one embodiment of the present invention when the absorption region is filled with a high thermal conductivity material and when the absorption region is filled with a high thermal conductivity material. [Specific implementation method]

[0015] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] The term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to separate or selective embodiments that are mutually exclusive of other embodiments. Unless otherwise specified, the terms "connected," "connected," and "connected" herein, indicating electrical connection, refer to direct or indirect electrical connection.

[0017] Please refer to Figure 1 FIG. 1 is a top view of an infrared thermopile sensor device based on CMOS technology in one embodiment of the present invention; please refer to FIG. Figure 2 , which is a schematic longitudinal cross-sectional view of an infrared thermopile sensor device based on CMOS technology in one embodiment of the present invention.

[0018] Figure 1 and Figure 2The infrared thermopile sensor device based on CMOS technology shown in the figure includes a base layer 1 (or substrate layer), a thermopile sensor 17 formed based on the base layer 1, and a signal processing circuit 16 formed based on the base layer 1. The signal processing circuit 16 is located in the signal processing circuit area; the thermopile sensor 17 is located in the thermopile area. Figure 1 In the illustrated embodiment, the signal processing circuit 16 is located outside the thermopile sensor 17. The signal processing circuit 16 is electrically connected to the thermopile sensor 17 and is configured to process the sensing signal generated by the thermopile sensor 17. Both the thermopile sensor 17 and the signal processing circuit 16 are fabricated using a CMOS process.

[0019] For example, on a 6-inch or 8-inch silicon wafer (the base layer is a silicon base, also called a silicon substrate), thin film deposition, ion implantation, etching and other methods are performed on the base layer 1 through standard CMOS processes to produce devices. For example, an infrared thermopile sensor device integrating a thermopile sensor 17 and a signal processing circuit 16 is produced through a process flow such as 1P2M or 2P3M. Figure 1 and Figure 2 In the illustrated embodiment, the structural layers of the thermopile sensor 17 located on the base layer 1 include, stacked in order from the front of the base layer 1 upward, a first dielectric layer 211, a polysilicon layer 3, a second dielectric layer 221, a first metal layer 5, a third dielectric layer 231, a second metal layer 6, and a passivation layer 7. The first dielectric layer 211, the second dielectric layer 221, and the third dielectric layer 231 are collectively referred to as the dielectric layer 2. The dielectric layer 2 is typically composed of materials such as SiO2, Si3N4, and BPSG. The polysilicon 3 is typically used to fabricate MOS tube electrodes, wiring, resistors, and capacitors. The metal layers 5 and 6 represent different layers of metal wiring, and are not limited to two layers of metal. The different metal layers are connected through metal fillers (referred to as via metal) in vias 4. The passivation layer 7 is typically composed of materials such as SiO2, Si3N4, and BPSG.

[0020] exist Figure 2 FIG. 1 shows only a longitudinal cross-sectional view of the thermopile sensor 17 manufactured based on a standard CMOS process.

[0021] The thermopile sensor 17 includes an absorption region 15 and a plurality of thermocouples 18 located around the absorption region 15. In order to improve the performance of the thermopile sensor, thermal isolation is required. A cavity 8 can be formed on the base layer 1 by back etching using a wet or dry process. Figure 2 As shown, the cavity 8 penetrates the base layer 1 to obtain a suspended thin film structure of the thermopile sensor 17; or Figure 3As shown, the base layer 1 is etched forward through the etching hole 10 set in the absorption area 15 to form a cavity 9, and finally a suspended thin film structure of the thermopile sensor 17 is obtained. The cavity 9 extends from the front of the base layer 1 to the inside of the base layer 1. Figure 3 FIG1 is a schematic longitudinal cross-sectional view of an infrared thermopile sensor device based on CMOS technology in another embodiment of the present invention. Figure 3 and Figure 2 The structures of the thermopile sensors shown are basically the same. The main difference between the two is that Figure 3 The absorption region 15 of the thermopile sensor 17 shown is further provided with an etching hole 10 penetrating the structural layer; the cavity 9 and the cavity 8 are formed in different ways and structures.

[0022] The absorption zone 15 is suspended above the cavity of the base layer 1 and includes a stacked first metal layer 5, a dielectric layer 231, and a second metal layer 6. The first metal layer 5 is closer to the cavity of the base layer 1 than the second metal layer 6. The dielectric layer 231 of the absorption zone 15 is located between the first metal layer 5 and the second metal layer 6. The second metal layer 6 of the absorption zone 15 is patterned to form a predetermined pattern. The hot end 20 of the thermocouple 18 is suspended above the cavity of the base layer 1 and adjacent to the absorption zone 15. The cold end 19 of the thermocouple 18 is located on the base layer 1 to maintain a temperature consistent with the ambient temperature.

[0023] Each thermocouple 18 is composed of a polysilicon layer 3, a first metal layer 5, and / or a second metal layer 6. Obviously, the first metal layer 5 of the thermocouple 18 and the first metal layer 5 of the absorption region 15 are different portions of the same patterned metal layer, the second metal layer 6 of the thermocouple 18 and the second metal layer 6 of the absorption region 15 are different portions of the same patterned metal layer, and the polysilicon layer 3 of the thermocouple 18 and the polysilicon layer 3 of the absorption region 15 are different portions of the same patterned polysilicon layer.

[0024] When the absorption area 15 absorbs infrared rays, the surface temperature of the absorption area 15 increases, and the temperature difference between the cold end 19 and the hot end 20 of the thermocouple 18 is converted into a voltage signal, which is provided to the signal processing circuit 16 for signal processing. Finally, the signal processing circuit 16 outputs a temperature signal in analog or digital form.

[0025] One of the key points of the present invention is to utilize the metal layers 5 and 6 (also referred to as metal interconnect layers 5 and 6) in the CMOS process to construct a surface plasmon infrared enhanced absorption structure consisting of the metal layer 5, the dielectric layer 231 and the metal layer 6 in the absorption region 15. Figure 4 As shown, it is Figure 2A magnified view of the infrared-enhanced absorption structure constructed in the absorption region 15. The first metal layer 5 fills the entire absorption region 15, forming a reflector 23 that prevents infrared light from passing through the lower surface of the film in the absorption region 15. A second dielectric layer 221, interposed between the first metal layer 5 and the second metal layer 6, absorbs incident infrared light. The second metal layer 6 in the absorption region 15 is patterned to form a predetermined pattern related to the wavelength range of infrared light absorbed by the absorption region 15.

[0026] like Figure 4 As shown, the second metal layer 6 is provided with a plurality of periodic units 13, 14, each periodic unit including a metal region and a non-metal region, the periodic width of the periodic unit is p, the width of the metal region is w1, and the width of the non-metal region is w2, wherein p=w1+w2, and the plurality of periodic units 13, 14 are arranged into the predetermined pattern. By setting the periodic width p of the periodic units 13, 14 and the width w1 of the metal region, perfect electromagnetic coupling can be achieved for infrared light of a specific wavelength, thereby improving the absorption rate. Figure 4 In the illustrated embodiment, the second metal layer 6 is composed of periodic units 13 and 14 of varying lengths. Depending on the absorption spectrum, the periodic width p of each periodic unit 13 and 14 is typically 5-15 μm. The width w1 of the metal region within each periodic unit 13 and 14 also varies. Setting w1 / p (also known as the duty cycle) between 0.2 and 0.8 yields a favorable infrared spectral absorption curve. The operating wavelength of the thermopile sensor 17 is typically between 5 and 20 μm. Depending on the temperature range of the object being detected, the wavelength range to which the thermopile sensor is sensitive also varies. Adjusting the periodic width p of each periodic unit 13 and 14 and w1 / p can be used to adjust the sensitive wavelength and absorptivity of the thermopile sensor 17.

[0027] The predetermined pattern of the second metal layer 6 in the absorption region 15 is an axisymmetric pattern along both the horizontal axis (x-axis) and the vertical axis (y-axis), thereby ensuring the same absorption characteristics for incident infrared rays from different directions.

[0028] Specifically, such as Figure 1 As shown, the predetermined pattern of the second metal layer 6 in the absorption area 15 is a multi-row and multi-column staggered pattern 21, similar to a "well" shape, and the predetermined pattern covers the entire absorption area 15. Figure 5 In the embodiment shown, the predetermined pattern of the second metal layer 6 in the absorption area 15 is a plurality of circular array patterns 22, which fill the entire absorption area 15. In other embodiments, the predetermined pattern of the second metal layer 6 in the absorption area 15 can also be other plurality of polygonal array patterns, which fill the entire absorption area 15. Figure 5FIG is a top view of an infrared thermopile sensor device based on CMOS technology in another embodiment of the present invention, which is Figure 1 The difference lies in that the predetermined pattern of the second metal layer 6 in the absorption region 15 is different.

[0029] The absorption zone 15 further includes a high thermal conductivity filling layer that is closer to the cavity of the base layer 1 than the first metal layer 5. Figure 2 As shown, the high thermal conductivity filling layer is a polysilicon layer 3. Of course, in other embodiments, other high thermal conductivity filling layers may also be used. The high thermal conductivity filling layer also covers the entire absorption region 15, which improves the temperature uniformity of the absorption region 15 and reduces heat dissipation in the gas. This can improve the performance of non-vacuum-encapsulated thermopile sensors by 5% to 20%.

[0030] Please refer to Figure 6 As shown in FIG, it is a comparison of the spectral absorption rate of the thermopile sensor with and without the enhanced absorption structure in one embodiment of the present invention. When the thermopile sensor is used to measure human body temperature, the central wavelength corresponding to human body temperature is 9.3 microns. Using standard CMOS technology, such as Figure 6 As shown, without the enhanced absorption structure used in the present invention, the overall absorptivity is low, the absorptivity fluctuates significantly with wavelength, and there is a valley in the absorptivity curve corresponding to 9.3 microns. This ultimately manifests as increased sensor nonlinearity, making it unsuitable for high-precision temperature measurement applications. With the enhanced absorption structure of the present invention, the overall absorptivity increases by nearly 20%, and the absorption spectrum curve becomes flatter.

[0031] Please refer to Figure 7 As shown in FIG. 1 , it is a comparison diagram of the temperature distribution of the thermopile sensor 17 in one embodiment of the present invention with or without a high thermal conductivity filling layer in the absorption area. Figure 7 It can be seen that filling the absorption zone 15 with high thermal conductivity polysilicon 3, metal layers 5 and 6 can not only improve the infrared absorption rate, but also improve the temperature uniformity of the absorption zone 15, reduce heat loss through the gas, increase the temperature difference between the hot end 20 and the cold end 19 of the thermocouple 18, and thus improve the sensitivity.

[0032] In summary, the present invention is based on a standard CMOS process flow and realizes the integration of a single-chip thermopile sensor 17 and a signal processing circuit 16. It utilizes the metal interconnect layers 5 and 6 of the CMOS to produce specific patterns to enhance infrared absorptivity and adjust the absorptivity at specific wavelengths, thereby solving the problem of low infrared absorptivity of thin films in the standard CMOS process and large variations in absorptivity with wavelength, thereby reducing production costs and improving sensor performance.

[0033] In the present invention, words such as “connect,” “connected,” “connect,” and “connected” that represent electrical connection, unless otherwise specified, represent direct or indirect electrical connection.

[0034] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the content disclosed in the present invention should be included in the protection scope recorded in the claims.

Claims

1. An infrared thermopile sensor device, characterized in that: The invention comprises a thermopile sensor formed on a base layer, the thermopile sensor comprising an absorption region, a cavity formed on the base layer, the absorption region being suspended above the cavity of the base layer, the absorption region comprising a stacked first metal layer, a dielectric layer, and a second metal layer, the first metal layer being closer to the cavity of the base layer than the second metal layer, the dielectric layer of the absorption region being located between the first metal layer and the second metal layer, and the second metal layer of the absorption region being patterned to form a predetermined pattern. The first metal layer of the absorption region constitutes a reflector; The dielectric layer in the absorption region is used to absorb incident infrared light; The patterned second metal layer of the absorption region includes a plurality of periodic units, The absorption zone further comprises: a high thermal conductivity filling layer closer to the cavity of the base layer than the first metal layer, wherein the first metal layer and the high thermal conductivity filling layer of the absorption zone cover the entire absorption zone. The thermopile sensor further includes a plurality of thermocouples located around the absorption region, wherein the hot ends of the thermocouples are suspended above the cavity of the base layer, and the cold ends of the thermocouples are located on the base layer. Each thermocouple is composed of a polysilicon layer, a first metal layer and a second metal layer. The first metal layer of the thermocouple and the first metal layer of the absorption zone are different parts formed by patterning the same layer of metal, the second metal layer of the thermocouple and the second metal layer of the absorption zone are different parts formed by patterning the same other layer of metal, and the polysilicon layer of the thermocouple and the polysilicon layer of the absorption zone are different parts formed by patterning the same layer of polysilicon.

2. The infrared thermopile sensor device according to claim 1, characterized in that: The predetermined pattern of the second metal layer in the absorption region is related to the wavelength range of the infrared light absorbed by the absorption region.

3. The infrared thermopile sensor device according to claim 1, characterized in that: The periodic unit includes a metal area and a non-metal area. The periodic width of the periodic unit is p, the width of the metal area is w1, and the width of the non-metal area is w2, wherein p=w1+w2. The periodic units are arranged into the predetermined pattern.

4. The infrared thermopile sensor device according to claim 3, characterized in that: The period width p of the periodic unit is 5-15 μm; w1 / p is between 0.2 and 0.

8.

5. The infrared thermopile sensor device according to claim 3, characterized in that: The predetermined pattern of the second metal layer in the absorption region is an axisymmetric pattern along both the horizontal and vertical axes. The predetermined pattern of the second metal layer in the absorption region is a multi-row and multi-column staggered arrangement pattern, a plurality of circular array arrangement patterns, or a plurality of polygonal array arrangement patterns. The predetermined pattern covers the entire absorption area.

6. The infrared thermopile sensor device according to claim 1, characterized in that: The high thermal conductivity filling layer is a polysilicon layer.

7. The infrared thermopile sensor device according to claim 6, characterized in that: A dielectric layer is further provided between the polysilicon layer and the base layer; A dielectric layer is also provided between the polysilicon layer and the second metal layer; A dielectric layer is also provided between the first metal layer and the second metal layer, and the first metal layer and the second metal layer are connected through via metal.

8. The infrared thermopile sensor device according to claim 1, characterized in that: It also includes a signal processing circuit formed based on the base layer. The signal processing circuit is electrically connected to the thermopile sensor and is used to process the sensing signal generated by the thermopile sensor.

9. The infrared thermopile sensor device according to claim 8, characterized in that: The thermopile sensor and the signal processing circuit are both manufactured based on CMOS technology.

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