Infrared thermopile sensor and method of forming the same

Abstract

An infrared thermopile sensor and its formation method are disclosed. The infrared thermopile sensor includes: an SOI substrate comprising a bottom silicon layer, a buried oxide layer, and a top silicon layer stacked sequentially; the top silicon layer is patterned to form a deflecting mirror with a MEMS micro-mirror, and electrostatically driven comb teeth and a torsion shaft disposed around the deflecting mirror; a first dielectric layer, located at least on the top surface of the deflecting mirror; a thermopile including a plurality of thermocouples located on the first dielectric layer on the deflecting mirror; an infrared absorption layer located on the surface of the thermopile; a first cavity penetrating the bottom silicon layer and the buried oxide layer, the projection of the infrared absorption layer onto the bottom silicon layer being located within the range of the first cavity; a second cavity penetrating the bottom silicon layer and the buried oxide layer around the deflecting mirror, exposing the electrostatically driven comb teeth and the torsion shaft; and further including a driving electrode and a detection electrode. This invention can improve integration, increase detection range, enhance synchronization performance, and reduce the requirements for installation accuracy.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an infrared thermopile sensor and a method for forming the same. Background Technology

[0002] Infrared thermopile sensors utilize the thermocouples made of different materials to detect infrared signals by generating a thermoelectric potential based on the temperature difference after absorbing infrared radiation. They offer advantages such as low cost, low power consumption, and no need for cooling, and are widely used in civilian and industrial fields.

[0003] The field of view (FOV) of a single-point infrared thermopile sensor refers to the spatial range in which it can detect infrared radiation. The FOV of a single-point infrared thermopile sensor is usually conical, extending outward from the sensor as the apex.

[0004] In traditional infrared thermopile sensors, the infrared receiving area is fixed in position, allowing detection of infrared radiation only in a fixed direction (fixed field of view). Expanding the detection range requires an additional mechanical rotating structure, which not only increases the device's size but also leads to poor signal synchronization between the infrared thermopile sensor and the external driving structure. Furthermore, because the infrared receiving area of ​​traditional infrared thermopile sensors is fixed and relatively small (typically below 20° FOV), high installation accuracy is required. Summary of the Invention

[0005] The technical problem solved by this invention is to provide an infrared thermopile sensor and a method for forming the same, so as to improve integration, increase detection range, enhance synchronization performance, and reduce the requirements for installation accuracy.

[0006] To address the aforementioned technical problems, the present invention provides an infrared thermopile sensor, comprising: an SOI substrate, including a bottom silicon layer, a buried oxide layer, and a top silicon layer stacked sequentially, wherein the top silicon layer is patterned to form a deflecting mirror of a MEMS micro-mirror, and electrostatic driving comb teeth and a torsion shaft disposed around the deflecting mirror; a first dielectric layer, at least located on the top surface of the deflecting mirror; a thermopile, including a plurality of thermocouples, the thermocouples being located on the first dielectric layer on the deflecting mirror; an infrared absorption layer, located on the surface of the thermopile; a first cavity, penetrating the bottom silicon layer and the buried oxide layer, wherein the projection of the infrared absorption layer on the bottom silicon layer is located within the range of the first cavity; a second cavity, penetrating the bottom silicon layer and the buried oxide layer around the deflecting mirror, exposing the electrostatic driving comb teeth and the torsion shaft; a driving electrode, the driving electrode being connected to the electrostatic driving comb teeth, for driving the torsion shaft to twist; and a detection electrode, the detection electrode being connected to the thermopile, for transmitting electrical signals to an external circuit.

[0007] Optionally, it further includes: a second dielectric layer located on the surface of the first dielectric layer; the plurality of thermocouples include: a first thermoelectric layer located on the surface of the first dielectric layer, the second dielectric layer also located on the surface of the first thermoelectric layer, and the second dielectric layer having a thermocouple opening therein, the thermocouple opening exposing a portion of the top surface of the first thermoelectric layer as an electrode connection point; a second thermoelectric layer located within the thermocouple opening and on the portion of the top surface of the second dielectric layer, the bottom surface of the second thermoelectric layer contacting the portion of the top surface of the first thermoelectric layer exposed by the thermocouple opening.

[0008] Optionally, the second thermal electrode layer and the driving electrode are the same metal layer.

[0009] Optionally, the material of the first thermoelectric layer is N-type polycrystalline silicon, and the material of the second thermoelectric layer is aluminum or platinum.

[0010] Optionally, the material of the first dielectric layer is silicon oxide or silicon nitride.

[0011] Optionally, the electrostatic drive comb teeth are located on both sides of the deflecting mirror along the first direction, and the torsion shaft is located on both sides of the deflecting mirror along the second direction, the first direction and the second direction being perpendicular to each other; the drive electrode is located on one side of the deflecting mirror along the second direction, and the drive electrode includes a first drive voltage electrode, a second ground electrode, and a third drive voltage electrode distributed sequentially along the first direction.

[0012] Optionally, the SOI substrate includes a first region and a second region surrounding the first region, the deflection mirror is located in the first region, the electrostatically driven comb and the torsion shaft are located in the second region, the first dielectric layer is also located on the top surface of the torsion shaft and extends to a portion of the top surface of the top silicon layer of the second region connected to the torsion shaft; the probe electrode is located on the first dielectric layer extending to a portion of the top surface of the top silicon layer connected to the torsion shaft.

[0013] Accordingly, the technical solution of the present invention also provides a method for forming an infrared thermopile sensor, for forming an infrared thermopile sensor as described above, comprising: providing an SOI substrate, comprising a bottom silicon layer, a buried oxide layer and a top silicon layer stacked sequentially, the SOI substrate comprising a first region and a second region surrounding the first region; forming a first dielectric layer on the top surface of the first region of the top silicon layer; forming a thermopile on the first dielectric layer, and forming a driving electrode and a detection electrode simultaneously with forming the thermopile; forming an electrostatic driving comb, a torsion shaft and a deflecting mirror in the top silicon layer, the electrostatic driving comb and the torsion shaft being located in the second region, and the deflecting mirror being located in the first region; forming a first cavity and a second cavity in the bottom silicon layer, exposing the electrostatic driving comb, the torsion shaft and part of the deflecting mirror; and forming an infrared absorption layer on the thermopile.

[0014] Optionally, the driving electrode and the detection electrode are formed simultaneously on the first dielectric layer while forming the thermopile, including: forming a plurality of first thermoelectrodes on the first dielectric layer, the plurality of first thermoelectrodes forming a first thermoelectrode layer; forming a second dielectric layer on the first thermoelectrode layer; forming a plurality of second thermoelectrodes on the second dielectric layer, and simultaneously forming the detection electrode and the driving electrode, the plurality of second thermoelectrodes forming a second thermoelectrode layer.

[0015] Optionally, forming an infrared absorption layer on the thermopile includes forming the infrared absorption layer on the second thermoelectrode layer.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: The infrared thermopile sensor and its formation method provided by the present invention include: an SOI substrate comprising a bottom silicon layer, a buried oxide layer, and a top silicon layer stacked sequentially, wherein the top silicon layer includes a deflector of a MEMS micromirror and electrostatically driven comb teeth and a torsion shaft disposed around the deflector; a first dielectric layer located at least on the top surface of the deflector; a thermopile including a plurality of thermocouples located on the first dielectric layer on the deflector; an infrared absorption layer located on the surface of the thermopile; a first cavity penetrating the bottom silicon layer and the buried oxide layer, wherein the projection of the infrared absorption layer on the bottom silicon layer is located within the range of the first cavity; a second cavity penetrating the bottom silicon layer and the buried oxide layer around the deflector, exposing the electrostatically driven comb teeth and the torsion shaft; and a driving electrode and a detection electrode. Therefore, the infrared thermopile sensor is integrated onto a MEMS micromirror, thereby improving integration, increasing the detection range, enhancing synchronization performance, and reducing the requirements for installation accuracy. Attached Figure Description

[0017] Figures 1 to 9This is a cross-sectional structural schematic diagram of each step in the method for forming an infrared thermopile sensor according to an embodiment of the present invention; Figure 10 This is a top view schematic diagram of the infrared thermopile sensor according to an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 100 - SOI substrate; 101 - Hot end region; 102 - Cold end region; 110 - Bottom silicon; 111 - First cavity; 112 - Second cavity; 120 - Buried oxide layer; 130 - Top silicon; 131 - Deflection mirror; 132 - Torsion shaft; 133 - Electrostatically driven comb teeth; 1331 - Fixed comb teeth; 1332 - Movable comb teeth; 210 - First dielectric layer; 211 - First dielectric layer; 220 - Second dielectric layer; 221 - Second dielectric layer; 222 - Thermocouple opening; 310 - First thermoelectric layer; 320 - Second thermoelectric layer; 400 - Driving electrode; 410 - First driving voltage electrode; 420 - Second ground electrode; 430 - Third driving voltage electrode; 500 - Detector electrode; 510 - First detector electrode; 520 - Second detector electrode; 600-Infrared absorption layer. Detailed Implementation

[0019] To make the objectives, features, and beneficial effects of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular 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. Additionally, directional terms such as above, below, up, down, upward, downward, left, right, etc., are used relative to exemplary embodiments as they are shown in the figures, with upward or upper directions pointing towards the top of the corresponding figure and downward or lower directions pointing towards the bottom of the corresponding figure.

[0021] Figures 1 to 9 This is a cross-sectional structural schematic diagram of each step in the method for forming an infrared thermopile sensor according to an embodiment of the present invention.

[0022] Please refer to Figure 1 Provides SOI substrate 100.

[0023] SOI substrate 100 includes: bottom silicon 110, buried oxide layer 120 and top silicon 130 stacked sequentially.

[0024] Among them, the top silicon layer 130 is monocrystalline silicon, and the buried oxide layer 120 is silicon oxide.

[0025] Specifically, the crystal orientation of the SOI substrate 100 is... <100> Crystal orientation.

[0026] The SOI substrate 100 also includes a first region I and a second region II, with the second region II surrounding the first region I. The top silicon 130 of the first region I forms the deflection mirror 131 of the MEMS micro-mirror, and the second region II corresponds to the second cavity 112 formed subsequently.

[0027] The deflector 131 is used to integrate an infrared thermopile sensor.

[0028] Specifically, the top silicon 130 of the first region I includes a hot end region 101 and a cold end region 102, with the cold end region 102 surrounding the hot end region 101. The hot end region 101 corresponds to the first cavity 111 formed subsequently.

[0029] Furthermore, the orthographic projection of the deflecting mirror 131 onto the surface of the SOI substrate 100 can be circular or square.

[0030] Please refer to Figure 2A first dielectric material layer 210 is formed on the top surface of the top silicon 130.

[0031] Among them, at least the first dielectric material layer 210 located on the top surface of the deflection mirror 131 is the first dielectric layer 211 (e.g., Figure 5 As shown in the image).

[0032] Specifically, the material of the first dielectric layer 210 can be silicon oxide (SiO2) or silicon nitride. Furthermore, the silicon oxide can be porous silicon oxide.

[0033] Specifically, a first dielectric material layer 210 can be grown on the surface of the SOI substrate 100 using a thermal oxidation process.

[0034] In this embodiment, before growing the first dielectric material layer 210, the SOI substrate 100 is ultrasonically cleaned with acetone and isopropanol in sequence, and then rinsed with deionized water and dried.

[0035] Please refer to Figure 3 A plurality of first thermal electrodes (not shown) are formed on the first dielectric material layer 210 (i.e., the first dielectric layer 211) on the deflecting mirror 131, and the plurality of first thermal electrodes constitute the first thermal electrode layer 310.

[0036] In this embodiment, the material of the first thermal electrode layer 310 is N-type polycrystalline silicon.

[0037] Specifically, the material of the first thermal electrode layer 310 is phosphorus-doped polycrystalline silicon.

[0038] In this embodiment, the method for forming the first thermoelectric layer 310 includes: forming a first thermoelectric material layer (not shown) on the surface of the first dielectric material layer 210; etching the first thermoelectric material layer until the surface of the first dielectric material layer 210 is exposed to form the first thermoelectric layer 310.

[0039] Furthermore, the thickness of the first thermal electrode layer 310 ranges from 200 nm to 300 nm.

[0040] Specifically, a first thermoelectric material layer can be formed on the surface of the first dielectric material layer 210 using a low-pressure chemical vapor deposition process.

[0041] Specifically, a dry etching process can be used to etch the first thermal electrode material layer. The etching gas may include SF6 gas.

[0042] Next, a second dielectric layer 221 is formed on the first thermoelectric layer 310. For detailed steps, please refer to [link / reference]. Figure 4 and Figure 5 .

[0043] Please refer to Figure 4A second dielectric material layer 220 is formed on the surface of the first dielectric material layer 210 and the surface of the first thermoelectric layer 310.

[0044] The second dielectric material layer 220 provides materials for forming the second dielectric layer 221.

[0045] Specifically, the material of the second dielectric layer 220 can be silicon oxide or silicon nitride.

[0046] Specifically, the second dielectric material layer 220 can be formed using plasma-enhanced chemical vapor deposition (PECVD).

[0047] Please refer to Figure 5 The second dielectric material layer 220 and the first dielectric material layer 210 are etched until the top surface of the top silicon 130 is exposed, so as to remove the second dielectric material layer 220 and the first dielectric material layer 210 other than the first dielectric layer 211 and the second dielectric layer 221.

[0048] Specifically, the material of the first dielectric layer 211 can be silicon oxide or silicon nitride. Furthermore, the silicon oxide can be porous silicon oxide.

[0049] Specifically, the material of the second dielectric layer 221 can be silicon oxide or silicon nitride.

[0050] Specifically, the second dielectric material layer 220 and the first dielectric material layer 210 can be etched using a dry etching process (RIE).

[0051] Please continue to refer to this. Figure 5 Meanwhile, by etching the second dielectric material layer 220, a thermocouple opening 222 is also formed in the second dielectric material layer 220 during the formation of the second dielectric layer 221, that is, the thermocouple opening 222 is located in the second dielectric layer 221.

[0052] Thermocouple opening 222 exposes a portion of the top surface of the first thermoelectric layer 310.

[0053] Thermocouple opening 222 is reserved for forming a second thermoelectric layer 320 that can contact the first thermoelectric layer 310.

[0054] Please refer to Figure 6 A plurality of second thermal electrodes (not shown) are formed on the second dielectric layer 221, and the plurality of second thermal electrodes constitute the second thermal electrode layer 320.

[0055] Specifically, a second thermoelectric layer 320 is formed within the thermocouple opening 222 and on a local top surface of the second dielectric layer 221.

[0056] The bottom surface of the second thermoelectric layer 320 contacts a portion of the top surface of the first thermoelectric layer 310 exposed by the thermocouple opening 222. The first thermoelectric layer 310 and the second thermoelectric layer 320 are alternately connected to form a thermopile. Thus, a plurality of thermocouples constituting the thermopile are formed on the first dielectric layer 211 on the deflecting mirror 131, wherein the top silicon layer 130 and the thermocouples are separated by the first dielectric layer 211.

[0057] Specifically, the material of the second thermal electrode layer 320 can be aluminum or platinum.

[0058] The method for forming the second thermoelectric layer 320 may include: depositing a second thermoelectric material layer (not shown) in the thermocouple opening 222, on the surface of the second dielectric layer 221, and on the exposed surface of the top silicon 130 using magnetron sputtering; and patterning the second thermoelectric material layer by etching or stripping processes.

[0059] In this embodiment, a detection electrode 500 and a driving electrode 400 are formed simultaneously with the formation of the second thermal electrode layer 320.

[0060] Specifically, the second thermoelectrode material layer also serves as the material for both the driving electrode 400 and the detection electrode 500. Therefore, when patterning the second thermoelectrode material layer, not only is the second thermoelectrode layer 320 formed, but also the driving electrode 400 and the detection electrode 500. That is, the second thermoelectrode layer 320, the driving electrode 400, and the detection electrode 500 are all the same metal layer. Because the second thermoelectrode layer 320, the driving electrode 400, and the detection electrode 500 are formed simultaneously in the same step, the process compatibility is good.

[0061] In this embodiment, the driving electrode 400 is connected to the subsequently formed electrostatic driving comb teeth 133. When the driving electrode 400 is connected to an external circuit, it generates a driving force through the electrostatic driving comb teeth 133, causing the torsion shaft 132 to twist so that the deflection mirror 131 deflects.

[0062] Specifically, the driving electrode 400 includes a first driving voltage electrode 410, a second grounding electrode 420, and a third driving voltage electrode 430, and in the second direction Y, the driving electrode 400 is located on one side of the deflecting mirror 131. The first driving voltage electrode 410 and the third driving voltage electrode 430 are respectively connected to the electrostatic driving comb teeth 133 on both sides. Specifically, the first driving voltage electrode 410 and the third driving voltage electrode 430 are respectively connected to the subsequently formed fixed comb teeth 1331, and the second grounding electrode 420 is used for grounding.

[0063] Wherein, the first direction X and the second direction Y are mutually perpendicular directions along the surface of the SOI substrate 100.

[0064] Specifically, the method for forming the first driving voltage electrode 410, the second ground electrode 420, and the third driving voltage electrode 430 includes: forming a second dielectric material layer; exposing the top silicon 130 when etching the second dielectric material layer to form the second dielectric layer; and forming the first driving voltage electrode 410, the second ground electrode 420, and the third driving voltage electrode 430 on the top silicon 130.

[0065] In this embodiment, the process of forming the first driving voltage electrode 410, the second ground electrode 420 and the third driving voltage electrode 430 is compatible with the process of forming a thermopile, and no additional process steps are required.

[0066] The probe electrode 500 is connected to a thermopile and is used to transmit electrical signals to external circuits.

[0067] Specifically, the detection electrode 500 includes: a first detection electrode 510 (e.g., ... Figure 10 (as shown in the image) and the second detection electrode 520 (as shown in the image) Figure 10 (As shown in the diagram). The first detection electrode 510 is connected to the second thermoelectric layer 320, and the second detection electrode 520 is connected to the first thermoelectric layer 310.

[0068] Specifically, the method for forming the first detection electrode 510 and the second detection electrode 520 includes: Electrical connection leads are pre-patterned during the formation of the first thermoelectric layer 310. These leads are then covered during the formation of the second dielectric material layer. The second dielectric material layer is etched to form a second dielectric layer 221, which also includes openings for the electrical connection leads. A second thermoelectric material layer is formed during this process. Simultaneously, a first detection electrode 510, metallically connected to the second thermoelectric layer 320, is formed during the etching of the second thermoelectric material layer. A second detection electrode 520 is formed at the openings for the electrical connection leads. The second detection electrode is connected to the first thermoelectric layer 310 via the pre-patterned electrical connection leads. When connected to an external circuit, the first detection electrode 510 and the second detection electrode 520 form a loop, transmitting electrical signals from the thermopile to the external circuit.

[0069] In this embodiment, the process of forming the first detection electrode 510 and the second detection electrode 520 is compatible with the process of forming a thermopile, and no additional process steps are required.

[0070] In this embodiment, the first detection electrode 510 and the second detection electrode 520 are located on both sides of the deflection mirror 131 along the second direction Y.

[0071] Please refer to Figure 7 Next, the top silicon layer 130 of the second region II is etched to pattern the top silicon layer 130, forming the deflection mirror 131 and the torsion shaft 132 (e.g., Figure 10(as shown in the diagram) and electrostatically driven comb teeth 133.

[0072] In this embodiment, by etching the top silicon 130 of the second region II, not only are the torsion shaft 132 and the electrostatic drive comb teeth 133 formed in the same step, but also the deflection mirror 131 is formed, thus achieving high process compatibility.

[0073] Specifically, since the top silicon layer 130 is made of monocrystalline silicon, the deflection mirror 131, the torsion shaft 132, and the electrostatically driven comb teeth 133 are also made of monocrystalline silicon.

[0074] In this embodiment, the first dielectric layer 211 also covers the top surface of the subsequently released torsion shaft 132 and extends to cover the upper and lower ends of the second region II along the second direction Y, so that the probe electrode 500 can be formed on the first dielectric layer 211.

[0075] Specifically, the electrostatically driven comb teeth 133 are located on both sides of the deflector 131 along the first direction X, and the torsion shaft 132 is located on both sides of the deflector 131 along the second direction Y.

[0076] The electrostatically driven comb teeth 133 include: a plurality of fixed comb teeth 1331 (such as...) Figure 10 (as shown) and several movable comb teeth 1332 (as shown) Figure 10 (As shown in the diagram). A plurality of fixed comb teeth 1331 and a plurality of movable comb teeth 1332 are staggered along the second direction Y to form an interdigitated structure. The fixed comb teeth 1331 are disconnected from the deflecting mirror 131 and connected to the top layer silicon 130 outside the second region II. The movable comb teeth 1332 are connected to the deflecting mirror 131 but disconnected from the top layer silicon 130 outside the second region II.

[0077] Specifically, deep reactive ion etching (DRIE) can be used to etch the top silicon 130 of region II.

[0078] Please refer to Figure 8 After forming the electrostatic drive comb teeth 133 and the torsion shaft 132, the bottom silicon 110 and the buried oxide layer 120 under the hot end region 101 and the second region II are etched from the back side of the bottom silicon 110 until the top silicon 130 is exposed, forming the first cavity 111 and the second cavity 112.

[0079] The first cavity 111 penetrates the bottom silicon 110 and the buried oxide layer 120, and exposes the deflection mirror 131 of the hot end region 101. The second cavity 112 penetrates the bottom silicon 110 and the buried oxide layer 120 around the deflection mirror 131, and exposes the electrostatically driven comb teeth 133 and the torsion shaft 132.

[0080] The first cavity 111 is used to release the hot end region 101 of the deflection mirror 131 to form a heat-insulating area and improve the accuracy of the sensor.

[0081] The second cavity 112 is used to release the electrostatic drive comb teeth 133 and the torsion shaft 132, and also serves to release the deflection mirror 131, thus ensuring high process compatibility.

[0082] Thus, through the first cavity 111 and the second cavity 112, the deflection mirror 131 can be freely deflected and a heat-insulating region can be formed in the hot end region 101 of the deflection mirror 131.

[0083] Specifically, deep reactive ion etching can be used to etch the bottom silicon 110 and buried oxide layer 120 under the hot end region 101 and the second region II.

[0084] Please refer to Figure 9 An infrared absorption layer 600 is formed on the surface of the thermopile within the preset hot end region 101.

[0085] The projection of the infrared absorption layer 600 onto the bottom silicon 110 lies within the area of ​​the first cavity 111.

[0086] Specifically, an infrared absorption layer 600 is formed on the second thermoelectrode layer 320.

[0087] Specifically, the infrared absorption layer 600 can be made of titanium nitride or carbon nanotube film.

[0088] Specifically, the thickness of the infrared absorption layer 600 ranges from 100 nanometers to 200 nanometers.

[0089] Specifically, an infrared absorption layer of 600 can be deposited using a vacuum coating machine.

[0090] Figure 10 This is a top view schematic diagram of the infrared thermopile sensor according to an embodiment of the present invention.

[0091] Accordingly, embodiments of the present invention also provide an infrared thermopile sensor formed using the above-described forming method. Please refer to [link / reference]. Figure 9 and Figure 10 , Figure 9 It is along Figure 10A cross-sectional structural diagram along the A1-A2 direction shows that the infrared thermopile sensor includes: an SOI substrate comprising a bottom silicon layer 110, a buried oxide layer 120, and a top silicon layer 130 stacked sequentially; the top silicon layer 130 being patterned to form a deflector 131 for a MEMS micro-mirror; and electrostatically driven comb teeth 133 and a torsion shaft 132 disposed around the deflector 131; a first dielectric layer 211, at least located on the top surface of the deflector 131; a thermopile including several thermocouples located on the first dielectric layer 211 on the deflector 131; and an infrared absorption layer 600 located on... On the thermopile: a first cavity 111, penetrating the bottom silicon 110 and the buried oxide layer 120, with the projection of the infrared absorption layer 600 onto the bottom silicon 110 located within the first cavity 111; a second cavity 112, penetrating the bottom silicon 110 and the buried oxide layer 120 around the deflecting mirror 131, exposing the electrostatic drive comb teeth 133 and the torsion shaft 132; a drive electrode 400, connected to the electrostatic drive comb teeth 133, used to drive the torsion shaft 132 to twist; and a detection electrode 500, connected to the thermopile, used to transmit electrical signals to an external circuit.

[0092] In this embodiment, the detection electrode 500 is connected to both the thermopile and external pads outside the hot end region 101. This allows it to receive the pressure difference generated by the conversion of thermal infrared radiation and, consequently, output a detection signal.

[0093] Furthermore, the first dielectric layer 211 is also located on the top surface of the torsion shaft 132 and extends to a portion of the top surface of the top silicon 130 of the second region connected to the torsion shaft 132; the probe electrode 500 is located on the first dielectric layer 211 extending to a portion of the top surface of the top silicon 130 connected to the torsion shaft 132.

[0094] In this embodiment of the invention, the infrared thermopile sensor includes: an SOI substrate comprising a bottom silicon layer 110, a buried oxide layer 120, and a top silicon layer 130 stacked sequentially; the top silicon layer 130 being patterned to form a deflector 131 of a MEMS micro-mirror; and electrostatically driven comb teeth 133 and a torsion shaft 132 disposed around the deflector 131; a first dielectric layer 211, at least located on the top surface of the deflector 131; and a thermopile comprising a plurality of thermocouples located on the deflector. The first dielectric layer 211 is located on the mirror 131; an infrared absorption layer 600 is located on the thermopile; a first cavity 111 penetrates the bottom silicon 110 and the buried oxide layer 120, and the projection of the infrared absorption layer 600 on the bottom silicon 110 is located within the range of the first cavity 111; a second cavity 112 penetrates the bottom silicon 110 and the buried oxide layer 120 around the deflecting mirror 131, exposing the electrostatic drive comb teeth 133 and the torsion shaft 132; a drive electrode 400; and a detection electrode 500. Therefore, an infrared thermopile sensor is integrated onto a MEMS micromirror, thereby improving integration, increasing the detection range, enhancing synchronization performance, and reducing the requirements for installation accuracy.

[0095] Specifically, the top silicon 130 includes a deflecting mirror 131, and electrostatically driven comb teeth 133 and a torsion shaft 132 disposed around the deflecting mirror 131. A first cavity 111 penetrates the bottom silicon 110 and the buried oxide layer 120, and the projection of the infrared absorption layer 600 on the bottom silicon 110 is located within the range of the first cavity 111, that is, the first cavity 111 exposes the deflecting mirror 131 of the hot end region 101. A second cavity 112 penetrates the bottom silicon 110 and the buried oxide layer 120 around the deflecting mirror 131 to expose the electrostatically driven comb teeth 133 and the torsion shaft 132. Therefore, the first cavity 111 forms a heat-insulating region in the hot end region 101 of the deflecting mirror 131, and the second cavity 112 releases the deflection and torsion of the electrostatically driven comb teeth 133 and the torsion shaft 132. Based on this, the electrostatic drive comb 133 can be driven by applying a driving voltage to the drive electrode 400, thereby driving the torsion shaft 132 to rotate, and thus causing the deflection mirror 131 to deflect, thus forming the structure of a MEMS micro-mirror.

[0096] Since the first dielectric layer 211 is located at least on the top surface of the deflection mirror 131, the thermopile includes several thermocouples located on the first dielectric layer 211 on the deflection mirror 131, the infrared absorption layer 600 is located on the thermopile, the first cavity 111 penetrates the bottom silicon 110 and the buried oxide layer 120, the first projection of the infrared absorption layer 600 on the surface of the deflection mirror 131 is located within the range of the second projection of the first cavity 111 on the surface of the deflection mirror 131, and the first cavity 111 exposes the deflection mirror 131 at the first projection location, and the detection electrode 500 is connected to the thermopile and the external pad respectively. Therefore, the sensor part of the infrared thermopile is integrated on the deflection mirror 131.

[0097] The first dielectric layer 211 serves as an insulating layer between the MEMS micromirror and the infrared thermopile, preventing signal interference between the MEMS micromirror's drive signal and the thermopile sensor. Furthermore, by positioning the probe electrode 500 on the first dielectric layer 211 and connecting it to both the thermopile and external pads outside the hot end region 101, a thermoelectric electromotive force (EMF) output is achieved. This, combined with the increased temperature difference, enhances the output EMF.

[0098] By integrating the infrared thermopile sensor onto the MEMS micromirror: Firstly, the infrared thermopile is deflected by the deflection of the deflection mirror 131, thereby adjusting the reflection direction of infrared radiation and realizing dynamic adjustment of the detection field of view. Specifically, the field of view can be extended from less than 20° with a traditional fixed thermopile to an adjustable greater than 60°, and supports multiple scanning modes, improving panoramic detection efficiency and increasing the detection range. Secondly, the integration of the deflection structure and the infrared thermopile measurement part is realized, thereby not only improving the integration and reducing the system size, but also, because it is mounted on a twistable mirror (i.e., deflection mirror 131), the installation position accuracy requirement of the infrared thermopile is reduced, and alignment can be achieved by twisting the mirror without the need for external optical alignment, avoiding the optical path alignment problem in the later assembly. Thirdly, since the deflection drive and the measurement reception are synchronized (in the prior art, the deflection drive structure is an additional external structure relative to the infrared thermopile, resulting in signal synchronization difference between the two), the integrated structure eliminates the transmission delay of the discrete system, thereby enhancing the synchronization performance, and the actual spatiotemporal synchronization accuracy can reach the microsecond level.

[0099] In this embodiment, the top silicon layer 130 is monocrystalline silicon, and the buried oxide layer 120 is silicon oxide.

[0100] Specifically, the crystal orientation of the SOI substrate 100 is... <100> Crystal orientation.

[0101] Correspondingly, the materials of the deflection mirror 131, the torsion shaft 132, and the electrostatically driven comb teeth 133 are all monocrystalline silicon.

[0102] In this embodiment, the orthographic projection of the deflecting mirror 131 onto the surface of the SOI substrate 100 can be circular or square.

[0103] The electrostatically driven comb teeth 133 are located on both sides of the deflecting mirror 131 along the first direction X, and the torsion shaft 132 is located on both sides of the deflecting mirror 131 along the second direction Y. The first direction X and the second direction Y are mutually perpendicular directions along the surface of the SOI substrate 100.

[0104] The electrostatically driven comb teeth 133 include several fixed comb teeth 1331 and several movable comb teeth 1332. The fixed comb teeth 1331 and movable comb teeth 1332 are staggered along the second direction Y, forming an interdigitated structure. The fixed comb teeth 1331 are disconnected from the deflection mirror 131 and connected to the top layer silicon 130 on the outer side of the region corresponding to the second cavity 112. The movable comb teeth 1332 are connected to the deflection mirror 131 but disconnected from the top layer silicon 130 on the outer side of the region corresponding to the second cavity 112. Specifically, the inner side of the region corresponding to the second cavity 112 refers to the side where the region corresponding to the first cavity 111 is located, while the opposite side to the side where the region corresponding to the first cavity 111 is located is the outer side of the region corresponding to the second cavity 112.

[0105] The first dielectric layer 211 is located at least on the top surface of the deflection mirror 131.

[0106] In this embodiment, the first dielectric layer 211 is also located on the top surface of the torsion shaft 132 and extends to a portion of the top surface of the top silicon 130 connected to the torsion shaft 132.

[0107] The material of the first dielectric layer 211 can be silicon oxide or silicon nitride. Furthermore, the silicon oxide can be porous silicon oxide.

[0108] Specifically, the thermocouples include: a first thermoelectrode layer 310 and a second thermoelectrode layer 320.

[0109] The first thermoelectric layer 310 is located on the surface of the first dielectric layer 211.

[0110] In this embodiment, the material of the first thermal electrode layer 310 is N-type polycrystalline silicon.

[0111] Specifically, the material of the first thermal electrode layer 310 is phosphorus-doped polycrystalline silicon.

[0112] Furthermore, the thickness of the first thermal electrode layer 310 ranges from 200 nm to 300 nm.

[0113] In this embodiment, the surface of the first dielectric layer 211 also has a second dielectric layer 221.

[0114] The material of the second dielectric layer 221 can be silicon oxide or silicon nitride.

[0115] In this embodiment, the second dielectric layer 221 is also located on the surface of the first thermoelectric layer 310, and the second dielectric layer 221 has a thermocouple opening 222, which exposes a portion of the top surface of the first thermoelectric layer 310.

[0116] Specifically, the second thermoelectrode layer 320 is located inside the thermocouple opening 222 and on the partial top surface of the second dielectric layer 221, and the bottom surface of the second thermoelectrode layer 320 is in contact with the partial top surface of the first thermoelectrode layer 310 exposed by the thermocouple opening 222.

[0117] The material of the second thermoelectrode layer 320 can be aluminum or platinum.

[0118] In this embodiment, the second thermal electrode layer 320, the driving electrode 400, and the detection electrode 500 are the same metal layer.

[0119] In this embodiment, the driving electrode 400 is located on the surface of the top silicon 130 surrounding the second cavity 112. Therefore, the driving electrode 400 is electrically connected to the top silicon 130 surrounding the second cavity 112, and the electrostatic driving comb teeth 133 and the torsion shaft 132 are both part of the top silicon 130. Thus, the electrostatic driving comb teeth 133 released by the second cavity 112 can be driven to drive the torsion shaft 132 to rotate, thereby deflecting the deflecting mirror 131.

[0120] In this embodiment, the driving electrode 400 includes a first driving voltage electrode 410, a second ground electrode 420, and a third driving voltage electrode 430, which are sequentially distributed along the first direction X. The driving electrode 400 is located on one side of the deflection mirror 131 along the second direction Y.

[0121] The first driving voltage electrode 410 and the third driving voltage electrode 430 are used to connect the driving voltage, and the second grounding electrode 420 is used for grounding, thereby driving the electrostatic drive comb teeth 133. Based on this, the torsion shaft 132 is torn by the electrostatic drive comb teeth 133, and the torsion shaft 132 drives the deflection mirror 131 to deflect around the torsion shaft 132, thereby adjusting the infrared reflection light path of the infrared thermopile on the deflection mirror 131.

[0122] Specifically, the detection electrode 500 includes a first detection electrode 510 and a second detection electrode 520. The first detection electrode 510 is connected to the second thermoelectric layer 320, and the second detection electrode 520 is connected to the first thermoelectric layer 310. When the first detection electrode 510 and the second detection electrode 520 are connected to an external circuit, they form a loop to transmit the electrical signal of the thermopile to the external circuit.

[0123] In this embodiment, the first detection electrode 510 and the second detection electrode 520 are located on both sides of the deflection mirror 131 along the second direction Y.

[0124] The infrared absorption layer 600 can be made of titanium nitride or carbon nanotube film.

[0125] Specifically, the thickness of the infrared absorption layer 600 ranges from 100 nanometers to 200 nanometers.

[0126] It should be noted that, Figure 10 For ease of understanding, the torsion axis 132 located below the first dielectric layer 211 is shown in a dashed box.

[0127] The materials, forming process, working principle, specific implementation method and beneficial effects of the infrared thermopile sensor in the embodiments of the present invention can be found in the forming method of the infrared thermopile sensor in the embodiments of the present invention, and will not be repeated here.

[0128] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An infrared thermopile sensor, characterized in that, include: The SOI substrate includes a bottom silicon layer, a buried oxide layer and a top silicon layer stacked sequentially. The top silicon layer is patterned to form a deflector of a MEMS micro-mirror, as well as an electrostatic drive comb and a torsion shaft disposed around the deflector. A first dielectric layer is located at least on the top surface of the deflecting mirror; A thermopile includes a plurality of thermocouples located on a first dielectric layer on the deflecting mirror; An infrared absorption layer is located on the surface of the thermopile; A first cavity extends through the underlying silicon and the buried oxide layer, and the projection of the infrared absorption layer onto the underlying silicon lies within the range of the first cavity; The second cavity penetrates the underlying silicon and buried oxide layer around the deflector, exposing the electrostatically driven comb teeth and the torsion shaft; A driving electrode, which is connected to the electrostatic driving comb teeth, is used to drive the torsion shaft to rotate; A detection electrode, which is connected to the thermopile, is used to transmit electrical signals to an external circuit.

2. The infrared thermopile sensor as described in claim 1, characterized in that, Also includes: The second dielectric layer is located on the surface of the first dielectric layer; The plurality of thermocouples include: a first thermoelectric layer located on the surface of the first dielectric layer, a second dielectric layer also located on the surface of the first thermoelectric layer, and the second dielectric layer having a thermocouple opening that exposes a portion of the top surface of the first thermoelectric layer as an electrode connection point. The second thermoelectrode layer is located inside the thermocouple opening and on a partial top surface of the second dielectric layer, with the bottom surface of the second thermoelectrode layer in contact with the partial top surface of the first thermoelectrode layer exposed by the thermocouple opening.

3. The infrared thermopile sensor as described in claim 2, characterized in that, The second thermal electrode layer and the driving electrode are the same metal layer.

4. The infrared thermopile sensor as described in claim 2, characterized in that, The first thermoelectric layer is made of N-type polycrystalline silicon, and the second thermoelectric layer is made of aluminum or platinum.

5. The infrared thermopile sensor as described in claim 2, characterized in that, The material of the first dielectric layer is silicon oxide or silicon nitride.

6. The infrared thermopile sensor as described in claim 1, characterized in that, The electrostatically driven comb teeth are located on both sides of the deflecting mirror along the first direction, and the torsion shaft is located on both sides of the deflecting mirror along the second direction, wherein the first direction and the second direction are perpendicular to each other; The driving electrode is located on one side of the deflecting mirror along the second direction, and the driving electrode includes a first driving voltage electrode, a second ground electrode, and a third driving voltage electrode distributed sequentially along the first direction.

7. The infrared thermopile sensor as described in claim 6, characterized in that, The SOI substrate includes a first region and a second region surrounding the first region. The deflection mirror is located in the first region, the electrostatically driven comb and the torsion shaft are located in the second region, the first dielectric layer is also located on the top surface of the torsion shaft and extends to a portion of the top surface of the top silicon layer of the second region connected to the torsion shaft; the probe electrode is located on the first dielectric layer extending to a portion of the top surface of the top silicon layer connected to the torsion shaft.

8. A method for forming an infrared thermopile sensor, characterized in that, For forming an infrared thermopile sensor as described in any one of claims 1 to 7, comprising: An SOI substrate is provided, comprising a bottom silicon layer, a buried oxide layer and a top silicon layer stacked sequentially, wherein the SOI substrate includes a first region and a second region surrounding the first region; A first dielectric layer is formed on the top surface of the first region of the top silicon layer; A thermopile is formed on the first dielectric layer, and a driving electrode and a detection electrode are formed simultaneously with the formation of the thermopile; An electrostatically driven comb, a torsion shaft, and a deflecting mirror are formed within the top silicon layer. The electrostatically driven comb and the torsion shaft are located in the second region, and the deflecting mirror is located in the first region. A first cavity and a second cavity are formed within the underlying silicon, exposing the electrostatically driven comb teeth, the torsion shaft, and a portion of the deflection mirror; An infrared absorbing layer is formed on the thermopile.

9. The method for forming an infrared thermopile sensor as described in claim 8, characterized in that, The driving electrode and the detection electrode are formed simultaneously on the first dielectric layer, including: A plurality of first thermal electrodes are formed on the first dielectric layer, and the plurality of first thermal electrodes constitute a first thermal electrode layer; A second dielectric layer is formed on the first thermoelectric layer; A plurality of second thermal electrodes are formed on the second dielectric layer, and the detection electrode and the driving electrode are formed thereon. The plurality of second thermal electrodes constitute a second thermal electrode layer.

10. The method for forming an infrared thermopile sensor as described in claim 9, characterized in that, Forming an infrared absorption layer on the thermopile includes: forming the infrared absorption layer on the second thermoelectrode layer.

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