Micro thermoelectric equipment processing method

Abstract

The invention provides a micro thermoelectric equipment processing method, and belongs to the technical field of micro thermoelectric equipment manufacturing. According to the method, firstly, a bottom electrode is processed, then, a P-type thermoelectric leg Sb2Te3 and an N-type thermoelectric leg Bi2Te3 are processed, then, a top suspended electrode is processed, developing liquid is diluted, the developing time is gradually prolonged, photoresist is dissolved to the upper surfaces of the thermoelectric legs or is 0-1 m lower than the upper surfaces of the thermoelectric legs, then, washing is carried out immediately, the undissolved photoresist is reserved at the moment, and finally, the top suspended electrode is processed. Therefore, the electrode serves as a sacrificial layer and helps to complete bridging between the top electrode and the thermoelectric leg, and finally annealing treatment is carried out. The manufacturing process provided by the invention is completely compatible with the processing process of the existing silicon-based microelectronic equipment, and has good universality and compatibility; a multi-layer vertical structure is formed by adopting an alternating process of an ultraviolet lithography technology and a magnetron sputtering technology, and wide-band photoelectric detection and on-chip local temperature regulation and control can be realized.

Description

Technical Field

[0001] The invention relates to a micro thermoelectric device processing method, belonging to the technical field of micro thermoelectric device manufacturing. Background Art

[0002] With rapid economic development, the demand for energy is increasing. Fossil fuels, as one of the primary energy sources, are also causing increasingly serious environmental pollution during their extraction and use. Furthermore, fossil fuels are non-renewable resources, and prolonged extraction will eventually lead to depletion. Therefore, developing clean, efficient, and stable energy conversion materials to reduce reliance on fossil fuels is crucial for achieving sustainable development.

[0003] Thermoelectric materials are emerging, environmentally friendly materials that convert thermal energy into electricity based on the thermoelectric effect. Thermal energy that would otherwise be wasted, such as industrial waste heat, geothermal energy, and solar energy, can now be efficiently converted into electricity through thermoelectric materials, thereby promoting sustainable energy development. Thermoelectric effects include the Seebeck effect, the Peltier effect, and the Thomson effect. The Seebeck effect describes the free mobility of charge carriers in metals or semiconductors. When a temperature difference exists between the two ends of the material, charged carriers at the hot end diffuse toward the cold end. Consequently, opposite charges accumulate at the cold and hot ends, generating an electric potential difference. The ratio of the thermoelectric potential to the temperature difference is the Seebeck coefficient. The Peltier effect describes the temperature change at the junction of two different conductors when current flows through it. Therefore, the thermoelectric effect can be applied to both power generation and temperature control.

[0004] Devices based on the thermoelectric effect are called thermoelectric devices (TEDs), including thermoelectric generators (TEGs) and thermoelectric coolers (TECs). They can reversibly convert heat into electricity. TEDs have the advantages of no moving parts, fast thermal response, quiet operation, reliability, and scalability, making them suitable for long-term operation. TEDs can be divided into two categories based on their spatial scale: macro-TEDs and micro-TEDs (µ-TEDs).

[0005] Macroscopic thermoelectric devices (primarily macroscopic thermoelectric coolers) have been commercialized by several companies, including Laird Thermal Systems, KELK, FerroTec, Gentherm, and Marlow. These devices feature a thermopile made of thermocouples that are electrically connected in series and thermally connected in parallel, with overall dimensions ranging from 1 cm 2 to 300cm 2 , the thermocouple density is usually 10 / cm2 , providing a cooling temperature differential of 60-80K and handling heat fluxes up to 200W. Applications for macroscopic thermoelectric devices include thermal management and power supply needs in batteries, telecommunications components, automotive, and biomedical devices. However, the low thermocouple density of macroscopic thermoelectric devices, due to their large size, limits their application in integrated microelectronic device systems.

[0006] In contrast, the thermoelectric legs in micro-thermoelectric devices have a smaller cross-sectional area and shorter height, making them easily integrated with multifunctional devices. Thermocouple densities can reach hundreds or thousands per square centimeter. Based on thermal scaling effects, µ-TEDs can generate large temperature gradients within the micro- and nanoscale range, enabling on-chip temperature control. Furthermore, µ-TEDs can flexibly switch between the Seebeck and Peltier effects to harvest energy or detect weak photoelectric signals, enabling self-powered electronic devices and high-precision, wide-spectrum photoelectric detection.

[0007] It should be noted that the development of micro-thermoelectric devices faces considerable challenges. Materials, processes, and structures are the primary factors influencing µ-TED performance. First, µ-TED performance is highly correlated with the ZT value of the thermoelectric material, but achieving a high ZT is difficult. Optimizing the power factor and suppressing thermal conductivity have also been challenges in thermoelectric material research, particularly in developing high-performance near-room-temperature thermoelectric materials. Second, µ-TED fabrication also presents challenges. The manufacturing process for µ-TED is complex, and the connection between the top electrode and the thermoelectric legs at the micro- and nanoscale significantly increases the processing complexity.

[0008] Therefore, it is of great significance to develop a new method for processing and manufacturing micro thermoelectric devices with high thermocouple density, high reliability, high response speed and high temperature regulation capability. Summary of the Invention

[0009] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and further provide a method for processing a micro thermoelectric device.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] A micro thermoelectric device processing method comprises the following steps:

[0012] Step 1: Processing of bottom electrode:

[0013] First, a photoresist is spin-coated on a silicon wafer and pre-baked. Then, a bottom electrode pattern is photoetched on the photoresist and post-baked. A bottom electrode deposition groove is formed by development. Then, the bottom electrode material is sequentially sputtered in the order of Ti-Al-Ti-Ni-Ti layers on the electrode deposition groove using magnetron sputtering technology. Finally, the photoresist is stripped off.

[0014] Step 2: Processing of P-type thermoelectric legs Sb2Te3:

[0015] On the basis of step 1, the photoresist is spin-coated again and pre-baked. Then, a P-type thermoelectric leg pattern is photoetched on the photoresist and post-baked. A P-type thermoelectric leg deposition groove is formed by development. Then, an Sb2Te3 layer is sputtered on the P-type thermoelectric leg deposition groove, followed by an Ni layer immediately thereafter, to complete the deposition of the P-type thermoelectric leg Sb2Te3. Finally, the photoresist is stripped.

[0016] Step 3: Processing of N-type thermoelectric legs Bi2Te3:

[0017] On the basis of step 2, the photoresist is spin-coated again and pre-baked. Then, the N-type thermoelectric leg pattern is photoetched on the photoresist and post-baked. The N-type thermoelectric leg deposition groove is formed by development. Then, a Bi2Te3 layer is sputtered on the N-type thermoelectric leg deposition groove, and then a Ni layer is sputtered immediately to complete the deposition of the N-type thermoelectric leg Bi2Te3. Finally, the photoresist is stripped.

[0018] Step 4: Processing of the top suspended electrode:

[0019] Based on step 3, photoresist is spin-coated again for pre-baking, and then a top electrode pattern is photoetched on the photoresist and post-baked. The resulting silicon wafer is immersed in a diluted developer, and the photoresist is gradually dissolved in the developer by gradually increasing the development time, so that the photoresist is dissolved to the upper surface of the thermoelectric leg or 0-1µm below the upper surface of the thermoelectric leg. Afterwards, it is immediately rinsed, and the undissolved photoresist is retained to serve as a sacrificial layer, thereby forming a top electrode deposition groove. A Ti layer is sputtered on the top electrode deposition groove, and then an Al layer is sputtered to complete the deposition of the top suspended electrode; finally, the photoresist is stripped to complete the assembly and manufacturing of the micro thermoelectric device;

[0020] Step 5: Annealing:

[0021] The micro thermoelectric device is placed in a tube furnace, the annealing atmosphere is vacuum, the temperature is raised to 250 ° C, then kept warm, and then cooled to room temperature to complete the processing.

[0022] Preferably, in step 1, the silicon wafer is a 500µm thick silicon wafer, covered with a 100nm thick SiO2 oxide layer, and the silicon wafer is cut into a size of 1cm×1cm; the thickness of the Ti layer is 20~30 nm per layer, the thickness of the Al layer is 1.5~2.5µm, and the thickness of the Ni layer is 80~120 nm.

[0023] Preferably, in step 1, the pre-baking temperature is 100°C and the time is 120 s, and the post-baking temperature is 100°C and the time is 90 s; the substrate temperature during sputtering is 50°C and the background vacuum is 5×10 -4 Pa, argon pressure was 0.3~0.6Pa, substrate stage rotation speed was 6 r / min, and target substrate distance was 136 mm; first, Ti was sputtered at a DC power of 50 W for 10 min, then Al was sputtered at a DC power of 100 W for 120 min, then Ni was sputtered at a DC power of 50 W for 20 min, and finally Ti was sputtered at a DC power of 50 W for 10 min.

[0024] Preferably, in step 2, the thickness of the Sb2Te3 layer is 3-5 μm.

[0025] Preferably, in step 2, the pre-baking temperature is 100°C and the time is 120 s, and the post-baking temperature is 100°C and the time is 90 s; the substrate temperature during sputtering is 50°C and the background vacuum is 5×10 -4 Pa, argon pressure was 0.3~0.6 Pa, substrate stage speed was 6 r / min, target substrate distance was 136 mm, Sb2Te3 was sputtered for 270 min at RF power of 50 W, and then Ni was sputtered for 10 min at DC power of 50 W immediately.

[0026] Preferably, in step three, the Bi2Te3 layer has a thickness of 3 to 5 μm.

[0027] Preferably, in step 3, the pre-baking temperature is 100°C and the time is 120 s, and the post-baking temperature is 100°C and the time is 90 s; the substrate temperature during sputtering is 50°C and the background vacuum is 5×10 -4 Pa, argon pressure was 0.3~0.6Pa, substrate stage speed was 6 r / min, target substrate distance was 136 mm, Bi2Te3 was sputtered for 225 min at RF power of 50 W, and then Ni was sputtered for 10 min at DC power of 50 W immediately.

[0028] Preferably, in step 4, the thickness of the Ti layer is 20-30 nm, and the thickness of the Al layer is 1.5-2.5 μm.

[0029] Preferably, in step 4, the pre-bake temperature is 100°C and the time is 120 s, and the post-bake temperature is 100°C and the time is 90 s; the dilution ratio of the developer is: the volume ratio of ultrapure water to the developer = 1:1; the substrate temperature during sputtering is 50°C, and the background vacuum is 5×10 -4Pa, argon pressure was 0.3~0.6 Pa, substrate stage rotation speed was 6 r / min, and target substrate distance was 136 mm; first, Ti was sputtered at a DC power of 50 W for 10 min, and then Al was sputtered at a DC power of 100 W for 180 min.

[0030] Preferably, in step five, the gas pressure in the tube furnace is controlled below 5 Pa, the heating time is 20 min, and the holding time is 90 min.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The manufacturing process of the present invention is fully compatible with existing silicon-based microelectronic device processing (MEMS, Micro-Electro-Mechanical Systems) processes and has good universality and compatibility. Traditional micro thermoelectric devices are generally made by hot pressing or cutting bismuth-tellurium alloys. The device size produced in this way is limited by precision machinery, and the height of the thermoelectric legs is still above 100 microns, which is not compatible with existing silicon-based MEMS processes. It is also difficult to achieve complex integration of high-density thermocouples.

[0033] 2. This invention utilizes ultraviolet lithography technology to achieve extremely high processing precision, enabling personalized design of the device structure and achieving large-area, high-density thermocouple integration. This invention utilizes a four-pass photolithography alignment process for processing. During top electrode processing, the developer is diluted and the dissolution of the photoresist is cleverly controlled during the development process. The photoresist acts as a structural support and sacrificial layer, simply and conveniently achieving good electrical contact between the top electrode and the thermoelectric legs in the bridge structure.

[0034] 3. The present invention uses magnetron sputtering technology to successfully prepare high-quality micron-level thermoelectric films, reducing the vertical size of the device to less than 10 microns, which can be integrated with existing microelectronic devices.

[0035] 4. The present invention forms a multi-layer vertical structure on a silicon-based substrate through alternating processes of ultraviolet lithography and magnetron sputtering, which includes a bottom electrode, a P-type Sb2Te3 thermoelectric leg, an N-type Bi2Te3 thermoelectric leg and a top suspended electrode; a Ti-Al-Ti-Ni-Ti multi-layer metal system is used as the electrode material, in which the Ti layer serves as a bonding layer, the Al layer serves as a conductive body, and the Ni layer serves as a diffusion barrier layer.

[0036] 5. The present invention performs a 250°C annealing treatment on the finished micro-thermoelectric device in a vacuum environment to optimize the thermoelectric performance. The purpose is to promote the crystallization of the thermoelectric material, improve the electrical conductivity and its Seebeck coefficient, and thus improve the ZT value of the new micro-thermoelectric device.

[0037] 6. The present invention continuously adjusts the gas pressure, power and annealing conditions during magnetron sputtering, and finally determines the sputtering power to be 50 W, the sputtering gas pressure to be 0.3~0.6 Pa, and after magnetron annealing at 250°C for 1~1.5 hours, the obtained sputtered thin film layer has the best thermoelectric performance, which can take into account high Seebeck coefficient and electrical conductivity while having low thermal conductivity, thereby optimizing the power factor and suppressing thermal conductivity.

[0038] 7. The micro-thermoelectric device produced by the method of the present invention can achieve wide-band photoelectric detection and on-chip local temperature control, and has high thermocouple density, high reliability, high response speed and high temperature regulation capability; and has the following characteristics:

[0039] (1) The total height of the vertical structure is ≤10μm, and the cross-sectional size of the thermoelectric legs is micron-level;

[0040] (2) Thermocouple density ≥ 100 pairs / cm², using π-type vertical arrangement;

[0041] (3) The top electrode has a suspended bridge structure with a contact resistance of ≤0.1Ω. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the main structure of the thermocouple of the micro thermoelectric device.

[0043] Figure 2 This is a schematic diagram of the top view of the thermocouple structure of the micro thermoelectric device.

[0044] Figure 3 Schematic diagram of the process of integrated processing of micro thermoelectric devices;

[0045] Figure 3 (a) is the decomposition diagram of the μ-TED structure;

[0046] Figure 3 (b) is the circuit diagram of magnetron sputtering bottom;

[0047] Figure 3 (c) is the diagram of the P-type thermoelectric legs produced by magnetron sputtering;

[0048] Figure 3 (d) is the magnetron sputtering N-type thermoelectric leg diagram;

[0049] Figure 3 (e) for making a sacrificial layer map;

[0050] Figure 3 (f) is a diagram of the magnetron sputtering top electrode.

[0051] Figure 4 Photomask pattern for micro-thermoelectric devices.

[0052] Figure 5These are macroscopic and microscopic images of micro thermoelectric devices;

[0053] Figure 5 (a) Macroscopic image of the micro-thermoelectric device placed together with a one-yuan coin;

[0054] Figure 5 (b) Microscopic image of a micro thermoelectric device;

[0055] Figure 5 (c) is the second microscopic image of the micro thermoelectric device;

[0056] Figure 5 (d) is the third microscopic image of the micro thermoelectric device;

[0057] Figure 5 (e) is the fourth microscopic image of the micro thermoelectric device;

[0058] Figure 5 (f) is a microscopic image of the micro thermoelectric device V.

[0059] Figure 6 This is the electrical test diagram of the micro thermoelectric device.

[0060] Figure 7 Schematic diagram of using micro thermoelectric devices to realize photoelectric detection;

[0061] Figure 7 (a) Schematic diagram of emitting laser light towards a micro-thermoelectric device for photoelectric detection.

[0062] Figure 7 (b) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection at a detectable wavelength of 405 nm.

[0063] Figure 7 (c) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection at a detectable wavelength of 532 nm.

[0064] Figure 7 (d) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection at a detectable wavelength of 785 nm.

[0065] Figure 7 (e) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection when the detectable wavelength is 1064 nm;

[0066] Figure 7 (f) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection when the detectable wavelength is 1550nm.

[0067] Figure 8 To realize on-chip local temperature control map using micro thermoelectric devices;

[0068] Figure 8 (a) Diagram of on-chip local temperature control using micro-thermoelectric devices at a current of 1 mA;

[0069] Figure 8 (b) Diagram of on-chip local temperature control using micro thermoelectric devices at a current of 2 mA;

[0070] Figure 8 (c) Diagram of on-chip local temperature control using micro thermoelectric devices at a current of 3 mA;

[0071] Figure 8 (d) Diagram of on-chip local temperature control using micro-thermoelectric devices at a current of 4 mA;

[0072] Figure 8 (e) Diagram of on-chip local temperature control using micro thermoelectric devices at a current of 5 mA;

[0073] Figure 8 (f) Diagram of on-chip local temperature control using micro thermoelectric devices at a current of 1 mA;

[0074] Figure 8 (g) Diagram of on-chip local temperature control using micro thermoelectric devices at a current of 5 mA.

[0075] Figure 9 Figure 2. Wafer-level array integration diagram of micro thermoelectric devices. DETAILED DESCRIPTION

[0076] The present invention will be further described in detail below with reference to the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method is given, but the protection scope of the present invention is not limited to the following embodiment. Specific implementation method one:

[0078] A micro thermoelectric device processing method, the specific steps are as follows:

[0079] 1. Preliminary Preparation: 500µm-thick silicon wafers coated with a 100nm-thick SiO2 oxide layer were cut into 1cm x 1cm sections. Magnetron sputtering targets were provided by Zhongnuo New Materials. They were circular, 50.8mm in diameter, 6mm thick, and 99.99% pure. These targets included Al, Ni, and Ti for the electrodes, as well as N-type Bi2Te3 and P-type Sb2Te3 for the thermoelectric legs. The photoresist and developer were provided by Suzhou Leilichang Semiconductor Co., Ltd. (NR9-3000PY for the photoresist and AZ 300MIF for the developer). A 10cm x 10cm photomask, film-side down, was provided by Shenzhen Jixian Co., Ltd. for patterning the photoresist.

[0080] 2. Processing flow: Micro thermoelectric devices mainly consist of four layers, including substrate, bottom electrode, thermoelectric legs and top electrode. The specific structure is as follows Figure 1 This embodiment adopts a bottom-up assembly method to complete the manufacture of the micro thermoelectric device. Successfully manufacturing a complete micro thermoelectric device requires multiple photolithography alignments and material depositions.

[0081] (1) Processing of bottom electrode:

[0082] a. First photolithography: Spin-coat a 4 µm thick layer of negative-tone photoresist NR9-3000PY onto the silicon wafer at a spin speed of 2000 rpm for 80 seconds. After spin coating, bake the wafer at 100°C for 120 seconds (pre-bake). Then, photolithography the bottom electrode pattern onto the photoresist. Development and exposure of the photoresist transfer the pattern from the mask to the silicon wafer. After photolithography, bake the wafer at 100°C for 90 seconds (post-bake). After post-bake, immerse the wafer in a developer (AZ 300MIF for 10 seconds). This completes the formation of the bottom electrode deposition groove.

[0083] b. The bottom and top electrodes of the present invention both utilize a multilayer electrode structure, with the deposited materials consisting of Ti, Al, and Ni. Ti serves as the bond and layer between the SiO2 / Al, Al / Ni, and the electrodes and the thermoelectric legs. The Ti layer thickness is approximately 25 nm per layer, the Al layer thickness is approximately 1.5 µm, and the Ni layer thickness is approximately 100 nm. The material deposition of the present invention is accomplished by magnetron sputtering, with a substrate temperature of 50°C and a background vacuum of 5×10 -4 Pa, argon pressure is 0.5 Pa, substrate stage speed is 6 r / min, and target substrate distance is 136 mm. First, Ti is sputtered for 10 min at a DC power of 50 W, then Al is sputtered for 120 min at a DC power of 100 W, then Ti is sputtered for 10 min at a DC power of 50 W, then Ni is sputtered for 20 min at a DC power of 50 W, and finally Ti is sputtered for 10 min at a DC power of 50 W. At this point, the deposition of the bottom electrode material is completed; immediate sputtering should be performed when performing multi-layer sputtering. Immediate sputtering means continuing the next sputtering in the deposition groove after the previous sputtering is completed. The purpose is to protect the bottom electrode, thermoelectric legs and top electrode to prevent them from being oxidized or damaged;

[0084] c. Soak the silicon wafer in dimethyl sulfoxide (25°C, 120 min). The photoresist will then be stripped off. This completes the bottom electrode fabrication.

[0085] (2) Processing of P-type thermoelectric legs Sb2Te3:

[0086] a. Second photolithography: Spin-coat a 4 µm thick negative photoresist, NR9-3000PY, onto the silicon wafer with the bottom electrode. Follow the same baking process as in the previous steps to photoetch the P-type thermoelectric leg pattern onto the photoresist, followed by baking and development. This completes the formation of the P-type thermoelectric leg deposition grooves.

[0087] b. Prepare to sputter P-type material Sb2Te3. The substrate temperature is 50 °C and the background vacuum is 5×10 -4 Pa, argon pressure of 0.3 Pa, substrate stage rotation speed of 6 rpm, target-substrate distance of 136 mm, RF power of 50 W, and sputtering of Sb2Te3 (approximately 4 µm) for 270 minutes. Immediately thereafter, Ni was sputtered for 10 minutes at 50 W DC power. This completes the deposition of the P-type thermoelectric leg Sb2Te3. In this step, the argon pressure was 0.3 Pa, as this was done to optimize the performance of the P-type thermoelectric leg Sb2Te3 functional material. In this embodiment, this material performs best at an argon pressure of 0.3 Pa.

[0088] c. Afterwards, the film is immersed in dimethyl sulfoxide (25°C, 120 min), and the photoresist is stripped. This completes the fabrication of the P-type thermoelectric leg Sb2Te3.

[0089] (3) Processing of N-type thermoelectric legs Bi2Te3:

[0090] a. Third photolithography: Spin-coat a 6.5 µm thick negative photoresist, NR9-3000PY (1000 rpm, 120 seconds), pre-bake, and then photolithograph the N-type thermoelectric leg pattern on the photoresist. Post-bake and develop. This completes the formation of the N-type thermoelectric leg deposition grooves.

[0091] The reason why the thickness of the spin coating is 6.5 µm is that a 1.5-2.5 µm (1.5 µm in this embodiment) thick Al layer has been deposited in step (1). In order to make the N-type thermoelectric leg deposition groove produced by photolithography meet the deposition requirements of the material, the thickness of the photoresist needs to be increased.

[0092] b. Prepare to sputter N-type thermoelectric leg Bi2Te3. The substrate temperature is 50 °C and the background vacuum is 5×10 -4 Pa, argon pressure 0.5 Pa, substrate stage rotation speed 6 r / min, target substrate distance 136 mm, using RF power 50 W sputtering 225 minutes of Bi2Te3 (about 4 µm), immediately followed by 10 minutes of Ni sputtering at DC power 50 W. This completes the fabrication of N-type Bi2Te3 thermoelectric legs;

[0093] c. Afterwards, soak in dimethyl sulfoxide (25°C, 120 minutes), and then the photoresist will be stripped. This completes the fabrication of the N-type Bi2Te3 thermoelectric leg.

[0094] (4) Processing of top suspended electrodes

[0095] a. Fourth photolithography: spin-coat 8 µm thick negative photoresist NR9-3000PY (twice, 2000 rpm, 80 s), pre-bake, photolithography the top electrode pattern on the photoresist, and post-bake;

[0096] b. Fabrication of a sacrificial photoresist layer: To achieve a good bridge between the top electrode and the thermoelectric leg, photoresist is used as a supporting layer for the structure. The developer is diluted and the silicon wafer is immersed in the diluted developer for development. By gradually increasing the development time, the photoresist is dissolved to the top surface of the thermoelectric leg or slightly below it by 0-1µm. Afterwards, it is immediately rinsed, and any undissolved photoresist is retained, thus acting as a sacrificial layer to help complete the bridge between the top suspended electrode and the thermoelectric leg. This completes the fabrication of the top electrode deposition groove.

[0097] In this step, the developer used is AZ 300MIF, and the dilution ratio of the developer is: the volume ratio of ultrapure water to developer = 1:1. The main purpose is to slow down the development speed of the photoresist, so as to facilitate the control of the thickness of the photoresist and to facilitate the preparation of the photoresist sacrificial layer.

[0098] c. Prepare to deposit the top electrode. The top electrode structure is similar to the bottom electrode structure, both of which are multilayer structures. In the previous process, a Ni barrier layer was pre-sputtered to prevent damage to the thermoelectric leg surface during processing. The substrate temperature during sputtering was 50°C and the background vacuum was 5×10 -4 Pa, argon pressure was 0.5 Pa, substrate stage rotation speed was 6 rpm, and target-substrate distance was 136 mm. First, Ti was sputtered at 50 W DC power for 10 minutes, followed by Al sputtering at 100 W DC power for 180 minutes. This completed the deposition of the top electrode.

[0099] d. Afterwards, the device is immersed in dimethyl sulfoxide (25°C, 120 min). The photoresist is then stripped off, releasing the top electrode. This completes the assembly of the micro-thermoelectric device.

[0100] (5) Annealing

[0101] a. To improve device performance, the processed device is annealed. The main purpose is to promote the crystallization of the thermoelectric material and increase the electrical conductivity and Seebeck coefficient.

[0102] b. Place the device in a tube furnace in a vacuum annealing atmosphere with the pressure controlled below 5 Pa. Raise the temperature to 250°C over 20 minutes, hold for 90 minutes, and then cool to room temperature. This completes the process. Specific implementation method 2:

[0104] like Figure 1 As shown in the figure, it is a schematic diagram of the main structure of the thermocouple of the micro thermoelectric device; the main structure of the thermocouple of the micro thermoelectric device is a Π-shaped vertical structure, which can be mainly divided into four parts: substrate, bottom electrode, thermoelectric leg, and top electrode, among which the bottom and top electrodes are both multi-layer electrode structures. Figure 2 The figure shows a schematic diagram of the partial top view structure of the thermocouple of the micro thermoelectric device.

[0105] like Figure 3 As shown in the figure, the process of integrated processing of micro thermoelectric devices includes: Figure 3 (a) shows the decomposition diagram of the μ-TED structure; Figure 3 (b) shows the bottom circuit of magnetron sputtering; Figure 3 (c) shows a magnetron sputtered P-type thermoelectric leg; Figure 3 (d) shows the magnetron sputtered N-type thermoelectric leg; Figure 3 As shown in (e), a sacrificial layer (photoresist) is prepared; Figure 3 As shown in (f), the top electrode is magnetron sputtered; a bottom-up assembly method is adopted, multiple magnetron sputtering and UV lithography are performed, and photoresist is used as the support and sacrificial layer of the structure to finally complete the integrated manufacturing of the micro thermoelectric device. This method is universal.

[0106] like Figure 4 As shown, the photomask pattern of the micro thermoelectric device includes: a low top electrode pattern, a P-type thermoelectric leg pattern, an N-type thermoelectric leg pattern and a top electrode pattern. In this specific embodiment, a mask pattern integrating 24 thermocouples is provided, and the photomask pattern can be designed as needed.

[0107] like Figure 5 Shown are macroscopic and microscopic images of micro thermoelectric devices. Figure 5 (a) shows a macroscopic image of a micro thermoelectric device placed together with a one-yuan coin. Figure 5 (b) is a microscopic image of a micro thermoelectric device at a magnification of 397 times; Figure 5 (c) is the second microscopic image of the micro thermoelectric device, which is a microscopic image of the micro thermoelectric device at a magnification of 345 times; Figure 5 (d) is the third microscopic image of the micro thermoelectric device, which is a microscopic image of the micro thermoelectric device at a magnification of 172 times; Figure 5(e) is the fourth microscopic image of the micro-thermoelectric device, which is a side view microscopic image of the micro-thermoelectric device at a magnification of 170 times. The hanging top electrode can be clearly seen in the side view; Figure 5 (f) is the fifth microscopic image of the micro thermoelectric device; it is a microscopic image of the overall structure of the micro thermoelectric device at a magnification of 44 times.

[0108] like Figure 6 As shown, it is an electrical test diagram of the micro thermoelectric device. Through experimental testing and theoretical calculations, it is known that the resistance of a single pair of thermocouples is 0.229Ω, and the contact resistance of a single thermocouple is about 0.075Ω, which proves that the processing scheme of the present invention can achieve good electrical contact between the top electrode and the thermoelectric legs.

[0109] Table 1 Resistance values ​​of bottom electrode, thermoelectric leg and top electrode

[0110]

[0111] Table 1 shows the resistance values ​​of the bottom electrode, thermoelectric leg, and top electrode, where R bottom is the resistance of the bottom electrode, R Ti is the resistance of the Ti layer, R Al is the resistance of the Al layer, R Ni is the resistance of the Ni layer, R teg is the resistance of the thermoelectric leg, R Bi2Te3 is the resistance of Bi2Te3, R Sb2Te3 is the resistance of Sb2Te3, R top is the resistance of the top electrode;

[0112] like Figure 7 As shown in the figure, it is a schematic diagram of using micro thermoelectric devices to realize photoelectric detection. Figure 7 (a) Schematic diagram of emitting laser light to a micro-thermoelectric device for photoelectric detection. Figure 7 (b) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection at a detectable wavelength of 405 nm. Figure 7 (c) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection when the detectable wavelength is 532 nm; Figure 7 (d) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection at a detectable wavelength of 785 nm. Figure 7 (e) Schematic diagram of the micro-thermoelectric device realizing photoelectric detection when the detectable wavelength is 1064 nm; Figure 7 (f) Schematic diagram of the micro-thermoelectric device implementing photodetection at a detectable wavelength of 1550 nm. The detectable wavelength range covers 405–1550 nm, and the device exhibits high responsivity within the tested wavelength range.

[0113] like Figure 8Figure 2 shows the use of micro thermoelectric devices to achieve local temperature control on a chip. During the test, the substrate temperature was kept constant at 28.3°C, with a maximum temperature difference of 2.8K. Figure 8 (a) is a diagram showing the on-chip local temperature control using a micro thermoelectric device at a current of 1 mA. Figure 8 (b) is a diagram showing the on-chip local temperature control using a micro thermoelectric device at a current of 2 mA. Figure 8 (c) is a diagram showing the on-chip local temperature control using a micro thermoelectric device at a current of 3 mA. Figure 8 (d) is a diagram showing the on-chip local temperature control using a micro thermoelectric device at a current of 4 mA. Figure 8 (e) is a diagram showing the on-chip local temperature control using a micro thermoelectric device at a current of 5 mA. Figure 8 (f) is a diagram showing the on-chip local temperature control using a micro thermoelectric device at a current of 1 mA. The left and right sides show two different color schemes. Figure 8 (g) is a diagram of on-chip local temperature control using a micro-thermoelectric device at a current of 5 mA, with two different color schemes on the left and right. The temperature control method can change the surface temperature of the micro-thermoelectric device very quickly (<10 ms) by applying currents of different magnitudes, thereby achieving rapid on-chip local temperature control. Figure 8 It can be seen that a temperature gradient of nearly 3K can be achieved quickly (<10 ms) at a current of 5 mA, and the temperature gradient capability is about 450 K / mm.

[0114] like Figure 9 As shown in the figure, it is a wafer-level array integration diagram of a micro thermoelectric device. It can be clearly seen in the figure that the micro thermoelectric device is small in size, so it can be used in integrated microelectronic device systems to achieve large-area and high-density thermocouple integration.

[0115] The foregoing are merely preferred embodiments of the present invention. These embodiments are all different implementations based on the overall concept of the present invention. The scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A micro thermoelectric device processing method, characterized in that: The following steps are involved: Step 1: Processing of bottom electrode: First, a photoresist is spin-coated on a silicon wafer and pre-baked. Then, a bottom electrode pattern is photoetched on the photoresist and post-baked. A bottom electrode deposition groove is formed by development. Then, the bottom electrode material is sequentially sputtered in the order of Ti-Al-Ti-Ni-Ti layers on the electrode deposition groove using magnetron sputtering technology. Finally, the photoresist is stripped off. Step 2: Processing of P-type thermoelectric legs Sb2Te3: On the basis of step 1, the photoresist is spin-coated again and pre-baked. Then, a P-type thermoelectric leg pattern is photoetched on the photoresist and post-baked. A P-type thermoelectric leg deposition groove is formed by development. Then, an Sb2Te3 layer is sputtered on the P-type thermoelectric leg deposition groove, followed by an Ni layer immediately thereafter, to complete the deposition of the P-type thermoelectric leg Sb2Te3. Finally, the photoresist is stripped. Step 3: Processing of N-type thermoelectric legs Bi2Te3: On the basis of step 2, the photoresist is spin-coated again and pre-baked. Then, the N-type thermoelectric leg pattern is photoetched on the photoresist and post-baked. The N-type thermoelectric leg deposition groove is formed by development. Then, a Bi2Te3 layer is sputtered on the N-type thermoelectric leg deposition groove, and then a Ni layer is sputtered immediately to complete the deposition of the N-type thermoelectric leg Bi2Te3. Finally, the photoresist is stripped. Step 4: Processing of the top suspended electrode: Based on step 3, photoresist is spin-coated again for pre-baking, and then a top electrode pattern is photoetched on the photoresist and post-baked. The resulting silicon wafer is immersed in a diluted developer, and the photoresist is gradually dissolved in the developer by gradually increasing the development time, so that the photoresist is dissolved to the upper surface of the thermoelectric leg or 0-1µm below the upper surface of the thermoelectric leg. Afterwards, it is immediately rinsed, and the undissolved photoresist is retained to serve as a sacrificial layer, thereby forming a top electrode deposition groove. A Ti layer is sputtered on the top electrode deposition groove, and then an Al layer is sputtered to complete the deposition of the top suspended electrode; finally, the photoresist is stripped to complete the assembly and manufacturing of the micro thermoelectric device; Step 5: Annealing: The micro thermoelectric device is placed in a tube furnace, the annealing atmosphere is vacuum, the temperature is raised to 250 ° C, then kept warm, and then cooled to room temperature to complete the processing.

2. A micro thermoelectric device processing method according to claim 1, characterized in that: In step 1, the silicon wafer is 500µm thick, covered with a 100nm thick SiO2 oxide layer, and cut into 1cm×1cm sizes; the thickness of the Ti layer is 20~30nm per layer, the thickness of the Al layer is 1.5~2.5µm, and the thickness of the Ni layer is 80~120nm.

3. A micro thermoelectric device processing method according to claim 1 or 2, characterized in that: In step 1, the pre-baking temperature is 100 °C for 120 s, and the post-baking temperature is 100 °C for 90 s. The substrate temperature during sputtering is 50 °C, and the background vacuum is 5×10 -4 Pa, argon pressure was 0.3~0.6Pa, substrate stage rotation speed was 6 r / min, and target substrate distance was 136mm; first, Ti was sputtered at a DC power of 50 W for 10 min, then Al was sputtered at a DC power of 100 W for 120 min, then Ni was sputtered at a DC power of 50 W for 20 min, and finally Ti was sputtered at a DC power of 50 W for 10 min.

4. A micro thermoelectric device processing method according to claim 1, characterized in that: In step 2, the thickness of the Sb2Te3 layer is 3-5 μm.

5. A micro thermoelectric device processing method according to claim 1 or 4, characterized in that: In step 2, the pre-baking temperature is 100 °C, the time is 120 s, and the post-baking temperature is 100 °C, the time is 90 s; the substrate temperature during sputtering is 50 °C, and the background vacuum is 5×10 -4 Pa, argon pressure was 0.3~0.6 Pa, substrate stage speed was 6 r / min, target substrate distance was 136 mm, Sb2Te3 was sputtered for 270 min at RF power of 50 W, and then Ni was sputtered for 10 min at DC power of 50 W immediately.

6. A micro thermoelectric device processing method according to claim 1, characterized in that: In step 3, the thickness of the Bi2Te3 layer is 3-5 μm.

7. A micro thermoelectric device processing method according to claim 1 or 6, characterized in that: In step 3, the pre-bake temperature was 100 °C for 120 s, and the post-bake temperature was 100 °C for 90 s. The substrate temperature during sputtering was 50 °C, and the background vacuum was 5 × 10 -4 Pa, argon pressure was 0.3~0.6Pa, substrate stage speed was 6 r / min, target substrate distance was 136mm, Bi2Te3 was sputtered for 225 min at RF power of 50 W, and then Ni was sputtered for 10 min at DC power of 50 W immediately.

8. A micro thermoelectric device processing method according to claim 1, characterized in that: In step 4, the thickness of the Ti layer is 20-30 nm, and the thickness of the Al layer is 1.5-2.5 μm.

9. A micro thermoelectric device processing method according to claim 1 or 8, characterized in that: In step 4, the pre-baking temperature is 100 °C for 120 s, and the post-baking temperature is 100 °C for 90 s. The dilution ratio of the developer is: the volume ratio of ultrapure water to developer = 1:

1. The substrate temperature during sputtering is 50 °C, and the background vacuum is 5×10 -4 Pa, argon pressure was 0.3~0.6 Pa, substrate stage rotation speed was 6 r / min, and target substrate distance was 136 mm; first, Ti was sputtered at a DC power of 50 W for 10 min, and then Al was sputtered at a DC power of 100 W for 180 min.

10. A micro thermoelectric device processing method according to claim 1, characterized in that: In step 5, the gas pressure in the tube furnace is controlled below 5 Pa, the heating time is 20 min, and the holding time is 90 min.

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