An infrared thermopile sensing device
By combining the cold end with the high thermal conductivity fill zone in the infrared thermopile sensor, the temperature inconsistency problem of MEMS infrared thermopile sensor is solved, and compatible with the CMOS process and high consistency production is achieved, which is suitable for calibration of ASIC integrated chips.
Patent Information
- Application Number
- CN202110705145.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-06-24
- Publication Date
- 2025-09-02
- Estimated Expiration
- 2041-06-24
AI Technical Summary
The cold end of the existing MEMS infrared thermopile sensor is inconsistent with the ambient temperature, resulting in large deviations in sensitivity and response time, affecting the correction accuracy of the ASIC integrated chip, and is incompatible with standard CMOS processes.
An infrared thermopile sensing device is designed, in which the cold end of the thermocouple is located outside the suspended film and is close to the high thermal conductivity filling area. It is produced by the CMOS process to make the cold end temperature consistent with the substrate temperature and reduce the influence of process deviation.
It improves the performance consistency and compatibility of infrared thermopile sensors, reduces the impact of process deviation on sensitivity, facilitates back-end circuit correction, and achieves high consistency and high yield device production.
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Figure CN113310583B_ABST
Abstract
Description
Technical field
[0001] The present invention relates to the field of MEMS (Micro-Electro-Mechanical System) devices, and in particular to an infrared thermopile sensing device with high consistency, high yield, and compatibility with standard CMOS (Complementary Metal Oxide Semiconductor) processes. [Background Technology]
[0002] To ensure that the temperature of the thermopile cold end is consistent with the ambient temperature, the cold end of the existing MEMS thermopile structure is located on the silicon substrate, and the hot end is located on the suspended membrane. The boundary of the suspended membrane is defined by etching. Whether it is forward etching or back etching, the overall deviation caused by photolithography alignment and side etching is 20 to 40 microns. As a result, the boundary of the suspended membrane varies from region to region on the same wafer and from different wafer batches. The sensitivity and response time of the infrared thermopile sensor will have large deviations, resulting in poor consistency and unfavorable back-end calibration. This is especially true for the integrated chip of the thermopile and ASIC (Application Specific Integrated Circuit). To achieve appropriate accuracy, more calibration data bits are required.
[0003] Therefore, it is necessary to propose a technical solution to solve the technical problems that the performance parameters of the infrared thermopile structure have poor consistency and are greatly affected by process deviations. [Summary of the invention]
[0004] One of the objectives of the present invention is to provide an infrared thermopile sensing device that is not only compatible with standard CMOS processes but also makes the thermal parameters of the infrared thermopile insensitive to process deviations, thereby improving the performance consistency of the device.
[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 substrate, the thermopile sensor including: a suspended membrane suspended above a cavity of the substrate; a plurality of thermocouples arranged in the suspended membrane, the hot ends of the thermocouples suspended above the cavity of the substrate, and the hot ends of the thermocouples located on the inner side of the suspended membrane; the cold ends of the thermocouples suspended above the cavity of the substrate, and the cold ends of the thermocouples located on the outer edge of the suspended membrane; and a high thermal conductivity filling area arranged on the outer side of the suspended membrane, adjacent to the cold ends of the thermocouples, crossing the boundary of the cavity of the substrate, and extending onto the substrate.
[0006] Furthermore, there is no electrical connection between the high thermal conductivity filling area and the cold end of the thermocouple; the high thermal conductivity filling area enables the cold end temperature of the thermocouple to be consistent with the substrate temperature.
[0007] Furthermore, the suspended membrane includes a polysilicon layer, a first metal layer and a second metal layer stacked in sequence, and the thermocouple is composed of the polysilicon layer, the first metal layer and / or the second metal layer.
[0008] Furthermore, the high thermal conductivity filling area is formed by stacking materials with high thermal conductivity, and the high thermal conductivity filling area is composed of a polysilicon layer, a first metal layer and / or a second metal layer, wherein the first metal layer of the high thermal conductivity filling area and the first metal layer of the suspended film are different parts of the same layer of metal patterned, the second metal layer of the high thermal conductivity filling area and the second metal layer of the suspended film are different parts of the same another layer of metal patterned, and the polysilicon layer of the high thermal conductivity filling area and the polysilicon layer of the suspended film are different parts of the same layer of polysilicon patterned.
[0009] Furthermore, a dielectric layer is provided between the polysilicon layer and the substrate; a dielectric layer is provided between the polysilicon layer and the second metal layer; and a dielectric layer is provided between the first metal layer and the second metal layer.
[0010] Furthermore, the infrared thermopile sensor device further includes a signal processing circuit formed based on the substrate, wherein the signal processing circuit is electrically connected to the thermopile sensor and is used to process a sensing signal generated by the thermopile sensor.
[0011] Furthermore, the thermopile sensor and the signal processing circuit are both manufactured based on CMOS technology.
[0012] Furthermore, the distance between the high thermal conductivity filling area and the cold end of the thermocouple is between 0.2 and 5 μm. When the cold end of the thermocouple is located on the suspended membrane, the size of the cavity, process deviation and alignment deviation need to be considered.
[0013] Furthermore, the multiple thermocouples are divided into four groups, namely the first thermopile unit TP1, the second thermopile unit TP2, the third thermopile unit TP3 and the fourth thermopile unit TP4. The first thermopile unit TP1 and the second thermopile unit TP2 are respectively located on the first and second opposite sides of the suspended membrane; the third thermopile unit TP3 and the fourth thermopile unit TP4 are respectively located on the third and fourth opposite sides of the suspended membrane; the several thermocouples in each of the thermopile units are arranged in parallel along the side where they are located, and along the direction of the side where they are located, the lengths of the several thermocouples first increase one by one and then decrease one by one.
[0014] Compared with the existing technology, the infrared thermopile sensor device in the present invention is manufactured based on MEMS technology or standard CMOS technology. The entire thermopile is located on a suspended membrane, and the cold end of the thermopile is adjacent to a filling area composed of high thermal conductivity material, making the thermal parameters of the thermopile structure insensitive to process deviations, thereby obtaining a highly consistent infrared thermopile sensor on the entire wafer.
Brief Description of the Drawings
[0015] 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:
[0016] Figure 1 FIG1 is a top view of an infrared thermopile sensing device compatible with MEMS and CMOS processes according to an embodiment of the present invention;
[0017] Figure 2 FIG1 is a schematic longitudinal cross-sectional view of an infrared thermopile sensing device compatible with MEMS and CMOS processes according to an embodiment of the present invention;
[0018] Figure 3 FIG1 is a schematic longitudinal cross-sectional view of an infrared thermopile sensing device based on MEMS and CMOS process compatibility in another embodiment of the present invention;
[0019] Figure 4 FIG. 1 is a comparison diagram showing the effect of etching deviation on the sensitivity of the thermopile structure of the present invention and a conventional thermopile structure in one embodiment. [Specific implementation method]
[0020] 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.
[0021] 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.
[0022] Please refer to Figure 1FIG. 1 is a top view of an infrared thermopile sensor device based on MEMS and CMOS process compatibility 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 MEMS and CMOS process compatibility in one embodiment of the present invention.
[0023] Figure 1 and Figure 2 The infrared thermopile sensing device based on MEMS and CMOS process compatibility includes a substrate 1, a thermopile sensor 17 formed based on the substrate 1, and a signal processing circuit 16 formed based on the substrate 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 used to process the sensing signal generated by the thermopile sensor 17.
[0024] Figure 1 and Figure 2 The infrared thermopile sensor device shown can be manufactured on a traditional MEMS process or using a standard CMOS process. Based on a chip integrating a thermopile sensor 17 and a signal processing circuit 16, taking a standard CMOS process as an example, a device is manufactured on a silicon substrate 1 of a 6-inch or 8-inch wafer by performing thin film deposition, ion implantation, etching, and other methods on the substrate 1 through a standard CMOS process. For example, an infrared thermopile sensor device integrating a thermopile sensor 17 and a signal processing circuit 16 is manufactured through a process 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 substrate 1 include, stacked in order from the front of the substrate 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 topmost layer of the device is the passivation layer 7, typically composed of materials such as SiO2, Si3N4, and BPSG.
[0025] exist Figure 2FIG. 1 shows only a longitudinal cross-sectional view of the thermopile sensor 17 manufactured based on a standard CMOS process.
[0026] The thermopile sensor 17 includes a suspended membrane 15 and a high thermal conductivity filling area 18 disposed outside the suspended membrane 15. In order to improve the performance of the thermopile sensor, thermal isolation is required. A cavity 8 can be formed on the substrate 1 by a back etching process using a wet or dry process. Figure 2 As shown, the cavity 8 penetrates the substrate 1 to obtain the suspended membrane 15 of the thermopile sensor 17; or Figure 3 As shown, the substrate 1 is etched forward through the etching hole 9 set in the structural layer to form a cavity 10, and finally a suspended membrane 15 of the thermopile sensor 17 is obtained. The cavity 10 extends from the front surface of the substrate 1 to the inside of the substrate 1. Figure 3 FIG. 1 is a schematic longitudinal cross-sectional view of an infrared thermopile sensor device based on MEMS and CMOS process compatibility 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 structural layer of the thermopile sensor 17 shown is further provided with an etching hole 9 penetrating the structural layer; the cavity 10 and the cavity 8 are formed in different ways and structures.
[0027] The suspended membrane 15 is suspended above the cavities 8 and 10 of the substrate 1. The suspended membrane 15 includes a polysilicon layer 3, a first metal layer 5, and a second metal layer 6 stacked in sequence from the front of the substrate 1 upward. A plurality of thermocouples 11 are provided in the suspended membrane 15. Figure 1 and Figure 2In the illustrated embodiment, each thermocouple 11 is formed from a polysilicon layer 3, a first metal layer 5, and / or a second metal layer 6. The hot end 13 of the thermocouple 11 is suspended above the cavities 8 and 10 of the substrate 1 and located inside the suspended membrane 15. The cold end 12 of the thermocouple 11 is suspended above the cavities 8 and 10 of the substrate 1 and located at the outer edge of the suspended membrane 15. A high thermal conductivity filling region 18 is disposed outside the suspended membrane 15, adjacent to the cold end 12 of the thermocouple 11, spanning the boundaries 14 of the cavities 8 and 10 of the substrate 1, and extending to the substrate 1. The high thermal conductivity filling region 18 is formed by stacking high thermal conductivity materials and is sufficiently close to the cold end 12 of the thermocouple 11 that no electrical connection exists. For example, the distance between the high thermal conductivity filling region 18 and the cold end of the thermocouple 11 is small enough to meet the process capability limit, typically between 0.2 and 5 μm. The high thermal conductivity filling region 18 ensures that the temperature of the cold end 12 of the thermocouple 11 is consistent with the temperature of the substrate 1, and thus the temperature of the cold end 12 of the thermocouple 11 is consistent with the ambient temperature.
[0028] exist Figure 1 and Figure 2 In the embodiment shown, polysilicon 3 and a metal layer 5 or 6 are used to make a thermocouple 11, a sensitive structural unit of the thermopile, that is, the thermocouple 11 includes a polysilicon layer 3, a first metal layer 5 and / or a second metal layer 6. For example, the thermocouple 11 can be composed of a polysilicon layer 3 and a first metal layer 5; or the thermocouple 11 can be composed of a polysilicon layer 3 and a second metal layer 6; the high thermal conductivity filling area 18 is stacked with a material with high thermal conductivity, such as a polysilicon layer 3, a first metal layer 5 and / or a second metal layer 6. Obviously, the first metal layer 5 of the high thermal conductivity filling area 18 and the first metal layer 5 of the suspended membrane 15 are different parts of the same layer of metal patterned, the second metal layer 6 of the high thermal conductivity filling area 18 and the second metal layer 6 of the suspended membrane 15 are different parts of the same other layer of metal patterned, and the polysilicon layer 3 of the high thermal conductivity filling area 18 and the polysilicon layer 3 of the suspended membrane 15 are different parts of the same layer of polysilicon patterned.
[0029] When the suspended membrane 15 absorbs infrared rays, the surface temperature of the suspended membrane 15 increases, and the temperature difference between the cold end 12 and the hot end 13 of the thermocouple 11 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.
[0030] The key points of the present invention are: placing the cold end 12 of the thermocouple 11 on the suspended membrane 15, and placing a high thermal conductivity filling area 18 in the vicinity of the cold end 12 of the thermocouple 11. The high thermal conductivity filling area 18 is close enough to the cold end of the thermocouple 11, but there is no electrical connection; the high thermal conductivity filling area 18 extends from the cold end 12 of the thermocouple 11, across the boundary 14 of the etched cavities 8 and 10, and onto the silicon substrate 1. By setting the appropriate size of the etched cavities 8 and 10, the cold end 12 of the thermocouple 11 is always located on the suspended membrane 15 under the premise of considering process deviation and alignment deviation. That is to say, when setting the cold end 12 of the thermocouple 11 on the suspended membrane 15, the size, process deviation and alignment deviation of the etched cavities 8 and 10 need to be considered. Since the entire thermocouple 11 is located on the suspended membrane 15 , its heat conduction path is not sensitive to the influence of etching deviation, and the adjacent high thermal conductivity filling area 18 can still ensure that the temperature of the cold end 12 of the thermocouple 11 is the same as the substrate temperature.
[0031] The present invention places the cold end 12 and the hot end 13 of the thermocouple 11 on the suspended membrane 15, and places a high thermal conductivity filling area 18 at the cold end 12 of the thermocouple 11, so that the thermopile performance is not sensitive to etching deviation. Figure 4 The figure shows a comparison of the effect of etching deviation on the sensitivity of the thermopile structure (or thermopile sensor) of the present invention and a conventional thermopile structure in one embodiment. The comparison results show that when the etching deviation varies from 0 to 35 μm, the sensitivity deviation of the conventional thermopile structure is -13.2%, while the sensitivity deviation of the present structure is only 0.7%.
[0032] exist Figure 1 In the specific embodiment shown, multiple thermocouples 11 are arranged in the entire suspended membrane 15 area with maximum thermal efficiency. Specifically, the multiple thermocouples 11 are divided into four groups, namely the first thermopile unit TP1, the second thermopile unit TP2, the third thermopile unit TP3 and the fourth thermopile unit TP4, which are respectively arranged in the four directions of the upper, lower, left and right of the suspended membrane 15 (i.e., the surface direction of the substrate 1 or wafer). The first thermopile unit TP1 and the second thermopile unit TP2 are arranged in the X-axis direction and are respectively located on the opposite first and second sides of the suspended membrane 15; the third thermopile unit TP3 and the fourth thermopile unit TP4 are arranged in the Y-axis direction and are respectively located on the opposite third and fourth sides of the suspended membrane 15. The multiple thermocouples 11 in each thermopile unit are arranged in parallel along the side thereof, and the lengths of the multiple thermocouples 11 along the side thereof first increase and then decrease one by one.
[0033] In summary, the present invention provides an infrared thermopile sensor device based on MEMS and compatible with CMOS processes. The device places both the cold end 12 and the hot end 13 of the thermocouple 11 on a suspended membrane 15. By arranging a high thermal conductivity filling area 18 surrounding the cold end 12, the temperature of the device cold end can be kept consistent with the substrate temperature, and the device performance is insensitive to changes in process deviations, thereby obtaining an infrared thermopile sensor with high consistency. In addition, the present invention is compatible with CMOS processes and can produce an integrated chip of the thermopile sensor 17 and the signal processing circuit 16, thereby greatly improving the device performance consistency of the infrared thermopile sensor device of the present invention and facilitating the correction of the back-end circuit.
[0034] 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.
[0035] 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 thermopile sensor includes a thermopile sensor formed on a substrate, the thermopile sensor including: a suspended membrane suspended above the cavity of the substrate; A plurality of thermocouples are provided in the suspended membrane, wherein the hot ends of the thermocouples are suspended above the cavity of the substrate and are located inside the suspended membrane; and the cold ends of the thermocouples are suspended above the cavity of the substrate and are located at the outer edge of the suspended membrane; A high thermal conductivity filling region is provided on the outside of the suspended membrane, the distance between the high thermal conductivity filling region and the cold end of the thermocouple is between 0.2 and 5 μm, and the high thermal conductivity filling region crosses the boundary of the cavity of the substrate and extends onto the substrate. The suspended membrane includes a polysilicon layer, a first metal layer and a second metal layer stacked in sequence. The thermocouple is composed of a polysilicon layer, a first metal layer and / or a second metal layer. The high thermal conductivity filling area is formed by stacking materials with high thermal conductivity, and the high thermal conductivity filling area is composed of a polysilicon layer, a first metal layer and / or a second metal layer. The first metal layer of the high thermal conductivity filling area and the first metal layer of the suspended membrane are different portions of the same metal patterned layer, the second metal layer of the high thermal conductivity filling area and the second metal layer of the suspended membrane are different portions of the same metal patterned layer, and the polysilicon layer of the high thermal conductivity filling area and the polysilicon layer of the suspended membrane are different portions of the same polysilicon patterned layer. A dielectric layer is further provided between the polysilicon layer and the substrate; 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.
2. The infrared thermopile sensor device according to claim 1, characterized in that: There is no electrical connection between the high thermal conductivity filling area and the cold end of the thermocouple; The high thermal conductivity filling region enables the cold end temperature of the thermocouple to be consistent with the substrate temperature.
3. The infrared thermopile sensor device according to claim 1, characterized in that: It also includes a signal processing circuit formed based on the substrate, wherein the signal processing circuit is electrically connected to the thermopile sensor and is used to process the sensing signal generated by the thermopile sensor.
4. The infrared thermopile sensor device according to claim 3, characterized in that: The thermopile sensor and the signal processing circuit are both manufactured based on CMOS technology.
5. The infrared thermopile sensor device according to claim 1, characterized in that: The multiple thermocouples are divided into four groups, namely the first thermopile unit TP1, the second thermopile unit TP2, the third thermopile unit TP3 and the fourth thermopile unit TP4. The first thermopile unit TP1 and the second thermopile unit TP2 are respectively located on the first and second opposite sides of the suspended membrane; the third thermopile unit TP3 and the fourth thermopile unit TP4 are respectively located on the third and fourth opposite sides of the suspended membrane; The plurality of thermocouples in each of the thermopile units are sequentially arranged in parallel along the side where the thermocouples are located, and along the direction of the side where the thermocouples are located, the lengths of the plurality of thermocouples first increase and then decrease one by one.
Citation Information
Patent Citations
Infrared thermopile sensing device
CN215338609U