Simple high-yield thermoelectric thin film device preparation method
Through the simplified preparation method of thermoelectric thin film devices, using photolithography and magnetron sputtering technology, the existing thermoelectric thin film devices have been solved with complex processes and low yield rates, and the effects of high yield rates and high output voltages are achieved.
Patent Information
- Application Number
- CN202411611046.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-12
- Publication Date
- 2025-02-25
AI Technical Summary
During the production process, existing thermoelectric thin film devices have problems such as complex process, low yield rate, and insufficient output voltage. Especially because the contact resistance of the antimony-bismuth electrode pair is large, additional connection electrodes are required, which increases the production cycle and cost, and is prone to cause film to fall off and disconnect.
The simple high-yield thermoelectric thin film device preparation method is adopted, and the substrate is treated by ion cleaning or deposition of silicon nitride, and the base glue and top glue are added and spin-coated on the substrate surface using photolithography technology, and the photolithography bismuth electrode and copper electrode are formed to form a Z-shaped electrode structure, and the film is deposited by magnetron sputtering, and finally annealed in vacuum or inert gas to obtain a high-yield thermoelectric thin film device.
This method simplifies the process flow, improves yield, reduces the cycle and cost of device production, reduces the risk of film shedding and disconnection, and enhances the output signal and sensitivity of the device.
Smart Images
Figure CN119522012A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor device processing, and in particular to a simple method for preparing a thermoelectric thin film device with a high yield rate. Background Art
[0002] At present, the most accurate AC / DC conversion standard system in the world is realized by a thermoelectric converter composed of a heating body and a temperature sensor, so that the AC voltage (or current) and the DC voltage (or current) are applied to the heating body in turn, and the temperature sensor measures the temperature of the heating body. By comparing the Joule heat generated by them, the size of the electric power generated by the AC voltage (or current) can be measured. Among them, the temperature sensor mostly uses thermoelectric thin film devices, because the thin film thermocouple has the characteristics of fast response speed, high precision, small hot junction, and easy integration.
[0003] At present, most thermoelectric thin film devices use copper-constantan and antimony-bismuth electrode pairs as the positive and negative electrodes of thin film thermocouples. Although the copper-constantan electrode pair has a simple manufacturing process, the Seebeck coefficient is relatively low, so the thermoelectric potential generated is low. When the output electromotive force is the same, the circuit line width is smaller, and the processing size requirements of the device are higher. The contact resistance between antimony and bismuth in the antimony-bismuth electrode pair is large, which is not conducive to voltage output. If the contact resistance is to be reduced, it is necessary to introduce additional connecting electrodes. The connecting electrodes are generally high-conductivity conductors such as copper and silver. When introducing connecting electrodes, the device needs to add additional photolithography and vacuum coating processes. On the one hand, the device production cycle is longer and the cost is increased. At the same time, it will also cause film shedding, wire breakage, etc., greatly reducing the success rate of device production.
[0004] In view of the above problems, the present invention proposes a method for preparing a thermoelectric thin film device with a high yield rate, which has the characteristics of simple process, high yield rate and high output voltage. Summary of the invention
[0005] The purpose of the present invention is to provide a simple method for preparing a thermoelectric thin film device with a high yield rate. The thermoelectric thin film device obtained by the method of the present invention has a high yield rate and a high thermoelectric potential.
[0006] In order to achieve the above object, the technical solution of the present invention is:
[0007] A simple method for preparing a thermoelectric thin film device with a high yield rate comprises the following steps:
[0008] 1) Processing substrate
[0009] Plasma cleaning or deposition of silicon nitride to treat the substrate;
[0010] 2) Photolithography electrode
[0011] The base glue and the top glue were respectively added on the surface of the treated substrate, the spin coating speed of the base glue and the top glue was 1000 rpm, the drying temperature of the base glue was 160°C, the time was 5 min, and the drying temperature of the top glue was 100°C, the time was 1 min; then the obtained substrate was put into the photolithography machine, and the photolithography wavelength was 385nm and the light intensity was 7.7mW / μm 2 The exposure time is 400ms. After exposure, the bismuth electrode and the copper electrode are photoetched in a NMD-3 developer with a mass concentration of 2.38% for 10 minutes.
[0012] The bismuth electrode and the copper electrode are Z-shaped electrodes with opposite directions, and a plurality of bismuth electrodes and a plurality of copper electrodes are alternately arranged, and the horizontal sections overlap each other to form a first group of circuits; the second group of circuits has the same structure as the first group of circuits, and the bismuth electrodes of the first group of circuits are staggered and opposite to the copper electrodes of the second group of circuits; the bismuth electrode at the right terminal of the first group of circuits and the copper electrode at the right terminal of the second group of circuits are overlapped and connected with each other;
[0013] The first group of circuits and the second group of circuits are arranged vertically, and the lower section of the first group of circuits and the upper section of the second group of circuits form a central area;
[0014] 3) Electrode coating
[0015] Bismuth electrode and copper electrode are plated and deposited, wherein the plated and deposited film is deposited by magnetron sputtering, and the film resistance is monitored in real time after deposition to ensure that the surface resistance of the film is less than 20Ω / cm (the reason is that in order to make the device conductive, if the resistance is too large, the resistance of the device will be particularly large);
[0016] 4) Heat treatment
[0017] The substrate with the thin film deposited is immersed in a degumming solution to remove the photoresist, and then annealed in an inert gas or vacuum to obtain a simple thermoelectric thin film device with a high yield rate. If the central area of the thin film device is heated, the thin film device can output a voltage.
[0018] Step 1) The silicon nitride is deposited by radio frequency magnetron sputtering, and the deposited film thickness is 20 nm.
[0019] Step 1) The substrate is a quartz substrate with a size of 1.5 cm×1.5 cm.
[0020] Step 2) The base glue is LOR 5A and the top glue is AZ5214E.
[0021] Step 2) The width of each electrode: the spacing between adjacent vertical segment electrodes is 1:2, the overlapping length is 4 times the electrode width, the distance between the lower overlapping segment of the first group of circuits and the upper overlapping segment of the second group of circuits is 4 times the electrode width; the area occupied by the entire circuit does not exceed 1cm 2 .
[0022] Step 3) The vacuum coating method is evaporation or magnetron sputtering, preferably magnetron sputtering.
[0023] The specific method of the magnetron sputtering deposition in step 3) is to maintain the vacuum degree at 5×10 -3 Pa, the sputtering gas pressure is 1-2Pa, the DC sputtering of bismuth and copper electrodes has a deposition power of 40W; the RF magnetron sputtering of silicon nitride has a deposition power of 100W.
[0024] Step 4) The degumming solution is one of acetone, AZ300T or N-methylpyrrolidone, preferably N-methylpyrrolidone.
[0025] Step 4) The annealing method is that the substrate is heated to 250°C at a rate of 3°C / min under vacuum conditions, kept at this temperature for 10 minutes, and then cooled to room temperature at a rate of 3°C / min.
[0026] Compared with the prior art, the method of the present invention has the following beneficial effects: the present invention can prepare a thin film thermoelectric device only by a coating method and two photolithography steps, does not need to introduce additional connecting electrodes, has a small number of process flows, is simple, has a high yield rate, and is suitable for mass production. At the same time, since the thin film thermoelectric device obtained by the method of the present invention has only two materials in contact, the contact resistance between the materials is small, the bonding force between bismuth and the quartz substrate is strong, and it is not easy to fall off when the thin film is further deposited on the quartz substrate. Therefore, the thin film thermoelectric device reduces the contact resistance between the positive and negative electrodes of the thin film thermocouple, increases the output signal, and improves the device sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 The circuit structure of the bismuth electrode in the thin film device;
[0028] Figure 2 The circuit structure of the copper electrode in the thin film device;
[0029] Figure 3 The circuit structure of the thin film device as a whole;
[0030] Figure 4 A photograph of the device described in Example 1;
[0031] Figure 5 The voltage output performance of the device described in Example 1;
[0032] Figure 6 This is a photo of the device described in Comparative Example 1;
[0033] Figure 7 This is a photograph of the device described in Comparative Example 3. DETAILED DESCRIPTION
[0034] Embodiment 1:
[0035] (1) Circuit design: The device is fabricated on a quartz substrate coated with a silicon nitride transition layer. The circuit structure of the bismuth electrode is as follows: Figure 1 As shown, the circuit structure of the copper electrode is as follows Figure 2 The overall structure of the device is shown in Figure 3 As shown, each electrode has a width of 40 μm, an overlap area of 160 μm, an electrode spacing of 80 μm, and a device size of 1 cm × 1 cm;
[0036] (2) Fabrication of silicon nitride transition layer: The device was fabricated on a quartz substrate coated with a silicon nitride layer. The substrate size was 1.5 cm × 1.5 cm. Silicon nitride was deposited by radio frequency magnetron sputtering. Before depositing silicon nitride, the pressure in the deposition vacuum chamber was evacuated to 5 × 10 -4 Pa, then argon gas is introduced with a gas flow rate of 20 sccm, the vacuum valve is adjusted to control the vacuum chamber pressure to 1.5 Pa, the sputtering power is 100 W, the sputtering target is silicon nitride ceramic, and the deposited film thickness is 20 nm;
[0037] (3) Bismuth electrode photolithography process: 150 μL of LOR 5A photoresist was added to the surface of the quartz substrate after silicon nitride deposition, and the substrate was spin-coated at 1000 rpm for 1 min. After that, the substrate was placed in a 160°C environment for 5 min. The substrate was then transferred to room temperature and 150 μL of AZ5214E photoresist was added. The substrate was spin-coated at 1000 rpm for 1 min, and then transferred to a 100°C environment for 1 min. Finally, the substrate was placed in a photolithography machine and pressed. Figure 1 Photolithography was performed with a wavelength of 385 nm and a light intensity of 1.55 mW / mm 2 The exposure time is 400ms. After the exposure is completed, the substrate is placed in NMD-3 (2.38%) developer for 10 minutes, and then the substrate is washed with deionized water and blown dry before the bismuth film is deposited;
[0038] (4) Preparation of bismuth electrode: The substrate in (3) was transferred into the chamber of a magnetron sputtering deposition chamber, and the pressure of the vacuum chamber was evacuated to 5×10 -3 Pa or less, then introduce argon gas with a gas flow rate of 5 sccm, adjust the vacuum valve to control the vacuum chamber pressure to 1.5 Pa, the sputtering current is 60 mA, the corresponding sputtering power is 40 W, the sputtering target is a bismuth target, and the film resistance is monitored in real time after deposition to ensure that the film surface resistance is less than 100 Ω / cm. Then, soak the substrate in N-methylpyrrolidone for 8 hours to remove the photoresist, wash with deionized water and blow dry;
[0039] (5) 150 μL of LOR 5A photoresist was added to the substrate treated in (4), and the substrate was spin-coated at 1000 rpm for 1 min, and then placed in a 160°C environment for 5 min. The substrate was then transferred to room temperature and 150 μL of AZ5214E photoresist was added, and the substrate was spin-coated at 1000 rpm for 1 min, and then transferred to a 100°C environment for 1 min. Finally, the substrate was placed in a photolithography machine and pressed. Figure 2 Photolithography was performed with a wavelength of 385 nm and a light intensity of 1.55 mW / mm 2 The exposure time is 400ms. After the exposure is completed, the substrate is placed in NMD-3 (2.38%) developer for 10 minutes, and then the substrate is washed with deionized water and blown dry before the copper film is deposited;
[0040] (6) Transfer the substrate in (5) into the chamber of the magnetron sputtering deposition chamber and evacuate the vacuum chamber to a pressure of 5 × 10 -3 Pa or less, then introduce argon gas with a gas flow rate of 5 sccm, adjust the vacuum valve to control the vacuum chamber pressure to 1.5 Pa, the sputtering current is 60 mA, the corresponding sputtering power is 40 W, the sputtering target is a copper target, and the film resistance is monitored in real time after deposition to ensure that the film surface resistance is less than 20Ω / cm. Then, soak the substrate in N-methylpyrrolidone for 8 hours to remove the photoresist, wash with deionized water and blow dry;
[0041] (7) The substrate in (6) was transferred to a tube furnace and cleaned by introducing 200 sccm of argon gas. After 15 minutes, the tube furnace was evacuated to make the pressure inside the tube below 10 Pa. The temperature was then raised at 3°C / min to make the temperature inside the tube reach 250°C. The temperature was maintained for 10 minutes and then cooled at a rate of 3°C / min to room temperature. After taking out the substrate, a thermoelectric thin film device was obtained. The device effect is shown in FIG. Figure 4 As shown;
[0042] (8) The central area of the device is heated. When the heating temperature reaches 25°C, the output voltage of the device is about 0.013V. The output voltage curve after stabilization is as follows: Figure 5 shown.
[0043] Comparative Example 1:
[0044] Steps (1) to (3) are the same as those in Example 1.
[0045] (4) Preparation of bismuth electrode: The substrate in (3) was transferred into the cavity of the electron beam evaporation deposition chamber, and the pressure of the vacuum chamber was evacuated to 5×10 -3Pa, heating the bismuth particles, adjusting the electron beam current to make the deposition rate 0.01-0.02nm / s, monitoring the film resistance in real time after deposition to ensure that the film surface resistance is less than 100Ω / cm, and then immersing the substrate in N-methylpyrrolidone for 8h to remove the photoresist, washing with deionized water and drying;
[0046] Step (5) is the same as in Example 1.
[0047] (6) Transfer the substrate in (5) into the electron beam evaporation deposition chamber, and evacuate the vacuum chamber to a pressure of 5×10 -3 Pa, heating the bismuth particles, adjusting the electron beam current to make the deposition rate 0.01-0.02nm / s, monitoring the film resistance in real time after deposition to ensure that the film surface resistance is less than 20Ω / cm, and then immersing the substrate in N-methylpyrrolidone for 8h to remove the photoresist, washing with deionized water and drying;
[0048] Step (7) is the same as in Example 1.
[0049] The film-substrate bonding force of the evaporation deposition method described in Comparative Example 1 is weaker than that of magnetron sputtering deposition. The substrate area is consistent with the device circuit area, and the thickness of the photoresist is higher at the edge of the substrate during the coating process. Therefore, the selected substrate area is preferably larger than the circuit area. The device produced by the method described in Comparative Example 1 has a low yield rate, and the bismuth electrode is very easy to fall off the substrate. The actual device produced is as follows: Figure 6 shown.
[0050] The device of the present invention is more suitable for magnetron sputtering.
[0051] Comparative Example 2:
[0052] (1) The steps are the same as those in Example 1.
[0053] (2) Fabrication of silicon nitride transition layer: The device was fabricated on a quartz substrate coated with a silicon nitride layer. The substrate size was 1 cm × 1 cm. Silicon nitride was deposited by radio frequency magnetron sputtering. Before depositing silicon nitride, the pressure in the deposition vacuum chamber was evacuated to 5 × 10 -4 Pa, then argon gas is introduced with a gas flow rate of 20 sccm, the vacuum valve is adjusted to control the vacuum chamber pressure to 1.5 Pa, the sputtering power is 100 W, the sputtering target is silicon nitride ceramic, and the deposited film thickness is 20 nm;
[0054] Steps (3) to (7) are the same as those in Example 1.
[0055] The substrate of this comparative example is 1cm×1cm. The residual photoresist about 1-2mm near the edge of the substrate is much thicker than the central area. It is difficult to photolithography and deposit at the edge. Therefore, the electrode of the device made by this method cannot be deposited near the boundary of the substrate.
[0056] Comparative Example 3:
[0057] Steps (1)-(2) are the same as in Example 1
[0058] (3) Bismuth electrode photolithography process: 150 μL of LOR 5A photoresist was added to the surface of the quartz substrate after silicon nitride deposition, and the substrate was spin-coated at 4000 rpm for 1 min. After that, the substrate was placed in a 160°C environment for 5 min. The substrate was then transferred to room temperature and 150 μL of AZ5214E photoresist was added. The substrate was spin-coated at 4000 rpm for 1 min, and then transferred to a 100°C environment for 1 min. Finally, the substrate was placed in a photolithography machine and pressed. Figure 1 Photolithography was performed with a wavelength of 385 nm and a light intensity of 1.55 mW / mm 2 The exposure time is 400ms. After the exposure is completed, the substrate is placed in NMD-3 (2.38%) developer for 10 minutes, and then the substrate is washed with deionized water and blown dry before the bismuth film is deposited;
[0059] Steps (4)-(7) are the same as in Example 1.
[0060] The rotation speed of the coating process in this comparative example is too fast, and a thicker metal film cannot be deposited. If a too thick film is deposited by force, the film in the unlithographic area is also easily torn off during the stripping process. The device electrode deposition success rate obtained by the method described in this comparative example is extremely low, and most of them will fall off. Figure 7 shown.
[0061] The comparison between the comparative example and the embodiment shows that the thickness of the photoresist depends on the rotation speed. The faster the rotation speed, the thinner the photoresist. If the photoresist is too thin, the deposited film will be more easily connected into a whole piece, and the photolithographic part will be easily removed during the de-resin process.
Claims
1. A simple method for preparing a thermoelectric thin film device with high yield, characterized in that: There are the following steps: 1) Processing substrate Plasma cleaning or deposition of silicon nitride to treat the substrate; 2) Photolithography electrode The base glue and the top glue were respectively added on the surface of the treated substrate, the spin coating speed of the base glue and the top glue was 1000 rpm, the drying temperature of the base glue was 160°C, the time was 5 min, and the drying temperature of the top glue was 100°C, the time was 1 min; then the obtained substrate was put into the photolithography machine, and the photolithography wavelength was 385nm and the light intensity was 7.7mW / μm 2 The exposure time is 400ms. After exposure, the bismuth electrode and the copper electrode are photoetched in a NMD-3 developer with a mass concentration of 2.38% for 10 minutes. The bismuth electrode and the copper electrode are Z-shaped electrodes with opposite directions, and a plurality of bismuth electrodes and a plurality of copper electrodes are alternately arranged, and the horizontal section is an overlapping area, forming a first group of circuits; the second group of circuits has the same structure as the first group of circuits, and the bismuth electrodes of the first group of circuits are staggered and opposite to the copper electrodes of the second group of circuits; the bismuth electrode at the right terminal of the first group of circuits is connected to the copper electrode at the right terminal of the second group of circuits through the overlapping area; The first group of circuits and the second group of circuits are arranged vertically, and the lower section of the first group of circuits and the upper section of the second group of circuits form a central area; 3) Electrode coating Bismuth electrode and copper electrode coating deposition, the coating deposition adopts magnetron sputtering deposition, and the film resistance is monitored in real time after deposition to ensure that the film surface resistance is less than 20Ω / cm; 4) Heat treatment The substrate with the thin film deposited thereon is immersed in a degumming solution to remove the photoresist, and then annealed in an inert gas or vacuum to obtain a simple thermoelectric thin film device with a high yield rate.
2. The preparation method according to claim 1, characterized in that: Step 1) The silicon nitride is deposited by radio frequency magnetron sputtering, and the deposited film thickness is 20 nm.
3. The preparation method according to claim 1, characterized in that: Step 1) The substrate is a quartz substrate with a size of 1.5 cm×1.5 cm.
4. The preparation method according to claim 1, characterized in that: Step 2) The base glue is LOR 5A and the top glue is AZ5214E.
5. The preparation method according to claim 1, characterized in that: Step 2) The width of each electrode: the spacing between adjacent vertical segment electrodes is 1:2, the overlapping length is 4 times the electrode width, the distance between the lower overlapping segment of the first group of circuits and the upper overlapping segment of the second group of circuits is 4 times the electrode width; the area occupied by the entire circuit does not exceed 1cm 2 .
6. The preparation method according to claim 1, characterized in that: Step 3) The vacuum coating method is evaporation or magnetron sputtering, preferably, magnetron sputtering.
7. The preparation method according to claim 1, characterized in that: The specific method of the magnetron sputtering deposition in step 3) is to maintain the vacuum degree at 5×10 -3 Pa, the sputtering gas pressure is 1-2Pa, the DC sputtering of bismuth and copper electrodes has a deposition power of 40W; the RF magnetron sputtering of silicon nitride has a deposition power of 100W.
8. The preparation method according to claim 1, characterized in that: Step 4) The degumming solution is one of acetone, AZ300T or N-methylpyrrolidone, preferably N-methylpyrrolidone.
9. The preparation method according to claim 1, characterized in that: Step 4) The annealing method is that the substrate is heated to 250°C at a rate of 3°C / min under vacuum conditions, kept at this temperature for 10 minutes, and then cooled to room temperature at a rate of 3°C / min.