阅读说明：本技术 基于脉冲激光烧蚀的高精度快速薄膜热电器件及其制备方法 (High-precision rapid thin-film thermoelectric device based on pulse laser ablation and preparation method thereof ) 是由 祝薇 于跃东 邓元 彭康 胡少雄 于 2020-05-22 设计创作，主要内容包括：本发明涉及一种基于脉冲激光烧蚀的高精度快速薄膜热电器件的制备方法。在基底上沉积电极层后,先在电极层表面沉积热电材料,再利用激光烧蚀实现热电材料图案化,接着沉积绝缘层、喷涂上电极后制得薄膜热电器件,此技术可有效降低加工成本、减少加工环节。通过引入激光烧蚀法实现热电对高密度图案化的同时,薄膜热电材料可进行高温沉积,有利于实现高性能核心功能材料的引入。此外,通过将单个热电对的结构设计为“之”字型,实现同类型热电材料相邻排列,有效提高单位面积内热电对的集成数量,从而薄膜热电器件功率密度输出获得大大提升。(The invention relates to a preparation method of a high-precision and rapid thin-film thermoelectric device based on pulse laser ablation. After an electrode layer is deposited on a substrate, a thermoelectric material is deposited on the surface of the electrode layer, patterning of the thermoelectric material is realized by laser ablation, an insulating layer is deposited, and an electrode is sprayed to obtain the thin-film thermoelectric device. The laser ablation method is introduced to realize the high-density patterning of thermoelectric pair, and meanwhile, the thin-film thermoelectric material can be deposited at high temperature, so that the introduction of a high-performance core functional material is facilitated. In addition, the structure of a single thermoelectric pair is designed into a zigzag shape, so that the thermoelectric materials of the same type are adjacently arranged, the integrated number of the thermoelectric pairs in a unit area is effectively increased, and the power density output of the thin film thermoelectric device is greatly improved.)

1. A preparation method of a high-precision and rapid thin-film thermoelectric device based on pulse laser ablation is characterized by comprising the following steps:

(1) depositing an electrode layer

Sequentially depositing a Cu film, a Ni film and an Au film on the pretreated substrate to obtain a patterned electrode layer, namely a lower electrode;

(2) depositing thermoelectric material on surface of electrode layer

Sequentially depositing long n-type and p-type thermoelectric materials on the surface of the electrode layer obtained in the step (1);

(3) laser ablation for thermoelectric material patterning

Placing the sample on which the thermoelectric material is deposited under the condition of short pulse laser to carry out laser ablation, realizing the patterning of the thermoelectric material and forming a thermoelectric arm structure;

(4) depositing an insulating layer

Spin-coating an insulating coating on the surface of the patterned sample, and then patterning an insulating layer through ultraviolet exposure;

(5) spray-coating upper electrode

And (4) spraying a patterned electrode on the sample obtained in the step (4) to obtain the thin film thermoelectric device.

2. The method for manufacturing a thin film thermoelectric device according to claim 1, wherein in the step (3), the laser is an infrared laser.

3. The method as claimed in claim 2, wherein the wavelength of the infrared laser is 808-1064 nm.

4. The method for manufacturing a thin film thermoelectric device as claimed in claim 1, wherein in step (3), the laser ablation is specifically performed by: the pulse width is 600ps to 4ns, and the laser density is set at 1.31mJ cm^-2To 4.11mJ cm^-2The sample is subjected to 5-10 times of linear spacing of 5-10 μm and speed of 200-400mm s^-1The surface is swept.

5. The method as claimed in claim 1, wherein the sample is fixed and aligned with the mask plate on which the corresponding pattern is printed, and then the sample is placed under a short pulse laser to perform laser ablation, wherein the gap between the sample and the mask plate is 200-400 μm.

6. The method for manufacturing a thin-film thermoelectric device according to claim 1, wherein in the step (1), the deposition of the Cu film, the Ni film, and the Au film is performed by a magnetron sputtering process; and after the Cu film, the Ni film and the Au film are deposited, the sheet resistance value of the lower electrode is 6-10m omega/□.

7. The method for manufacturing a thin-film thermoelectric device as claimed in claim 1, wherein in step (2), the deposition of the n-type thermoelectric material and the p-type thermoelectric material is performed by magnetron sputtering, and the n-type thermoelectric material is Bi₂Te₃、Bi₂Te_2.7Se_0.5Any one of the above; the p-type thermoelectric material is Sb₂Te₃、Bi_0.5Sb_1.5Te₃Any one of them.

8. The method of claim 1, wherein the deposition temperature of the n-type thermoelectric material and the deposition temperature of the p-type thermoelectric material are both 200 ℃ to 400 ℃, the deposition power is 15W to 25W, and Te targets with different powers are co-sputtered according to the thermoelectric material.

9. The method for manufacturing a thin-film thermoelectric device as claimed in claim 1, wherein in the step (4), the insulating layer is solder resist green oil, and the thickness of the insulating layer is 25 to 30 μm.

10. The thin film thermoelectric device according to any one of claims 1 to 9, wherein individual thermoelectric pairs consisting of an upper electrode, two thermoelectric materials of P/N type and a lower electrode are arranged in a zigzag pattern, and the integrated density of the thermoelectric pairs is 200 to 400 pairs per cm²。

Technical Field

The invention belongs to the technical field of thin film thermoelectric devices, and particularly relates to a high-precision and rapid thin film thermoelectric device based on pulse laser ablation and a preparation method thereof.

Background

The heat energy is an energy form widely existing in the environment, and the micro thermoelectric energy conversion technology based on the environmental temperature difference power generation can realize the mutual conversion of the heat energy and the electric energy, so that the micro thermoelectric energy conversion technology is expected to provide stable and lasting electric energy for low-power-consumption electronic components. Therefore, the thin film thermoelectric device is used as a novel sustainable micro power supply system, and has urgent application requirements and wide market prospect.

The basic constituent unit of the thin-film thermoelectric device is a thermoelectric arm composed of an upper electrode, a lower electrode and a p/n type thermoelectric material. However, the output of a single pair of thermoelectric legs is limited, and in order to achieve high power density of the device, it is necessary to integrate as many thermoelectric legs as possible per unit area, that is, to achieve high-density arrayed integration of the thermoelectric legs. This process requires the accuracy of the thermoelectric material patterning technology to be as high as possible, however, the existing thermoelectric material patterning technology has the problems of high processing cost, complex process and poor compatibility with thermoelectric device fabrication.

At present, a thin film thermoelectric device is mainly based on a traditional silicon-based MEMS micromachining technology, and the specific steps are as follows: depositing a patterned lower electrode prepared by a photoetching stripping process on the surface of an aluminum nitride substrate by adopting a normal-temperature thermal evaporation method, a magnetron sputtering method or an electrochemical deposition method; (II) continuing to deposit n-type thermoelectric materials and p-type thermoelectric materials on the lower electrode patterns through a photoetching stripping process; (III) constructing an insulating layer by adopting an ultraviolet photosensitive material; and (IV) patterning and depositing an upper electrode on the upper surface of the thermoelectric material by adopting a photoetching stripping process. The photoetching stripping process comprises the following specific steps: (1) spin-coating a photoresist on a substrate, and heating to cure the photoresist; (2) aligning the substrate with a photoetching mask plate, and carrying out ultraviolet exposure; (3) the photoresist in a specific area is washed away by a developing solution (for positive photoresist, exposed parts can be washed away, and for negative photoresist, unexposed parts can be washed away), so that the patterning of the photoresist is realized; (4) depositing a material layer on the surface of the photoresist pattern of the substrate, wherein the material layer is on the surface of the photoresist and the photoresist cannot resist high temperature, so that the deposition temperature of the material is normal temperature; (5) and placing the substrate into the photoresist removing solution, dissolving the photoresist by the photoresist removing solution, and simultaneously carrying out the material layer on the surface of the photoresist together to realize the patterning of the material layer.

From the above steps, it can be found that the photolithography stripping technique has the defects of complexity, low yield and high cost although it has extremely high processing precision. In order to realize the patterning of the thermoelectric material, multiple links such as spin coating, exposure, development, photoresist removal and the like need to be completed in the photoetching stripping technology, and the cost of the photoresist is high, so that the cost of the final finished device is increased and the yield is low. Moreover, since the photoresist cannot withstand high temperature, in the photolithography lift-off technology, the deposition temperature of the thermoelectric material needs to be limited to normal temperature, so that the performance of the thermoelectric material cannot be improved by high-temperature deposition, and the performance of the core functional material is low, thereby affecting the performance of the device. On the other hand, when a patterning technology other than the photolithography stripping technology, such as a metal mask method, is used for preparing a thin film thermoelectric material, although the process is simple and the cost is low, the micron-sized precision is difficult to achieve, high-density integration cannot be realized, and the power generation performance of a device is greatly limited. Therefore, there is a need to develop a novel thermoelectric thin film power generation device preparation method which can meet the requirement of high-density array integration in precision, is compatible with high-temperature material deposition in the process, and has the advantages of simple preparation process, easy operation and low cost.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a high-precision and rapid thin-film thermoelectric device based on pulsed laser ablation and a preparation method thereof. The invention introduces the pulse laser ablation technology into the patterning of the thin film thermoelectric material, introduces the characteristics of simple and convenient laser ablation operation and low cost into the preparation of the thin film thermoelectric device, and the prepared device can be 1cm²200 to 400 pairs of thermoelectric legs are integrated in the range. Compared with the traditional photoetching stripping technology, the method has the advantages of reducing the operation cost and simplifying the operation steps. Meanwhile, the limitation on the deposition temperature of the thermoelectric material is effectively removed through patterning by a laser ablation technology, and the thermoelectric film is prepared by adopting a high-temperature magnetron sputtering technology, so that the power factor of the film is greatly improved and the device performance is effectively improved compared with normal-temperature depositionOutput performance, data show that Bi integrated in the device prepared by the invention₂Te₃The power factor of the film can reach 8.9 mu W cm at normal temperature^-1K^-2，Sb₂Te₃The power factor of the film can reach 10.1 mu W cm at normal temperature^-1K^-2And the output power of the whole device can realize the output in milliwatt level. The invention adopts the structural design of the zigzag thermoelectric pair, reduces the precision requirement when the thermoelectric material is deposited, and effectively improves the thermoelectric pair density in unit area. Then, solder resist green oil is used as an insulating layer, excellent temperature resistance and electric insulation characteristics are provided for the device insulating layer, and then the upper electrode is prepared in a silver paste painting mode, so that the method is simple and convenient, and the electric connection performance is excellent.

The technical scheme adopted by the invention is as follows:

a preparation method of a high-precision and rapid thin-film thermoelectric device based on pulse laser ablation comprises the following steps:

(1) depositing an electrode layer

Sequentially depositing a Cu film, a Ni film and an Au film on the pretreated substrate to obtain an electrode layer, namely a lower electrode;

(2) depositing thermoelectric material on surface of electrode layer

Depositing an n-type thermoelectric material on the surface of the electrode layer obtained in the step (1), and then depositing a p-type thermoelectric material to finish the deposition of the thermoelectric material;

(3) laser ablation for thermoelectric material patterning

Placing the sample on which the thermoelectric material is deposited under the condition of short pulse laser to carry out laser ablation so as to realize the patterning of the thermoelectric material;

(4) depositing an insulating layer

Depositing an insulating layer on the surface of the patterned sample, and etching a corresponding pattern on the insulating layer;

(5) spray-coating upper electrode

And (4) spraying an upper electrode on the sample deposited with the insulating layer obtained in the step (4) to obtain the thin film thermoelectric device.

In the step (3), the laser is an infrared laser.

The wavelength of the infrared laser is 808-1064 nm.

The specific operation of the laser ablation is as follows: the pulse width is 600ps to 4ns, and the laser density is set at 1.31mJ cm^-2To 4.11mJ cm^-2The sample is subjected to 5-10 times of linear spacing of 5-10 μm and speed of 200-400mm s^-1The surface is swept.

When the laser ablation is carried out, a sample and an optical mask plate printed with a corresponding pattern are fixed and aligned, and then the sample and the optical mask plate are placed under a short pulse laser to carry out the laser ablation, wherein the gap between the sample and the optical mask plate is 200-400 mu m.

In the step (1), the deposition of the Cu film, the Ni film and the Au film is carried out by adopting a magnetron sputtering process, and the magnetron sputtering conditions for depositing different films are as follows:

after depositing the Cu film, the Ni film and the Au film, the sheet resistance value of the lower electrode is 6-10m omega/□.

In the step (2), the n-type thermoelectric material is Bi₂Te₃、Bi₂Te_2.7Se_0.5Wherein the p-type thermoelectric material is Sb₂Te₃、Bi_0.5Sb_1.5Te₃Any one of the above; the deposition temperature of the thermoelectric material is between 200 ℃ and 400 ℃, the deposition power is between 15W and 25W, and Te targets with different powers are co-sputtered according to different thermoelectric materials.

In the step (3), a magnetron sputtering process is adopted to deposit the n-type thermoelectric material and the p-type thermoelectric material, and the magnetron sputtering conditions for depositing different thermoelectric materials are respectively as follows:

in the step (4), the insulating layer is deposited by adopting a spin coating process, and a corresponding pattern is etched on the insulating layer by adopting a photoetching method, which has the specific operations that:

in a darkroom, the device is placed on a spin coater, solder resist green oil is uniformly coated on the surface of the device, the rotation speed is set to 2500 revolutions per minute, spin coating is carried out for 3 minutes, then a heating plate at 150 ℃ is used for heating for 5 minutes, the device is placed for 3 minutes for cooling, then the device is aligned with a photoetching mask plate, a 360nm wavelength ultraviolet lamp is used for carrying out exposure on the solder resist green oil for 1 minute, then the device is placed in acetone for ultrasonic oscillation for 5 minutes, and the unexposed green oil is washed off, so that the pattern can be obtained. The insulating layer is solder resist green oil, and the thickness of the insulating layer is 25-30 mu m.

In the step (5), when the upper electrode is sprayed, the specific operations are as follows: fixing the sample and the metal mask plate engraved with the corresponding pattern together, spraying a silver paste electrode on the surface of the sample by adopting a paint spraying process, heating and curing for 1min by using a 150 ℃ hot air gun, and then separating the metal mask plate from the sample to finish the upper electrode spraying;

the silver paste electrode is prepared by fully mixing silver paste for screen printing and acetone according to the mass ratio of 3:4-3: 6.

In the thin film thermoelectric device, a single thermoelectric pair formed by an upper electrode, two P/N type thermoelectric materials and a lower electrode is distributed in a zigzag manner, and the integration density of the thermoelectric pairs is 200-400 pairs per cm²。

The invention has the beneficial effects that:

(1) the invention relates to a preparation method of a high-precision and rapid thin-film thermoelectric device based on pulsed laser ablation, which comprises the steps of depositing a thermoelectric material on the surface of an electrode layer after the electrode layer is deposited, realizing the patterning of the thermoelectric material by utilizing the laser ablation, depositing an insulating layer, and spraying an upper electrode to obtain the thin-film thermoelectric device; the method realizes the patterning of the core functional material by adopting the ultrashort pulse laser ablation, effectively removes the limit of the photoetching stripping technology on the deposition temperature of the thermoelectric material compared with the traditional process, greatly improves the pattern processing precision compared with a metal mask method, can realize high-density array, and has the characteristics of quick processing, low cost and high processing precision.

(2) The thin film thermoelectric device provided by the invention firstly proposes the idea of designing the structure of a single thermoelectric pair into a zigzag shape, and the design can realize the adjacent arrangement of thermoelectric materials, greatly reduce the precision requirement of device processing, improve the yield, reduce the production cost and overcome the problems of the prior thin film thermoelectric device that the precision requirement of the device is improved and the process is complicated because two thermoelectric materials need to be cross-deposited.

(3) The magnetron sputtering method adopted by the invention for depositing the thermoelectric material can prepare the high-performance P/N type thermoelectric material with the film thickness adjustable from 10 mu m to 20 mu m, and the thermoelectric material has a columnar growth structure which is beneficial to the transmission of current in the thermoelectric material, and the power factor is greatly improved compared with the normal temperature deposition technology.

(4) The invention adopts the solder resist green oil as the insulating layer, has high temperature resistance and low price compared with the insulating layer constructed by the traditional photoresist, and effectively reduces the production cost.

(5) The upper electrode prepared by the silver paste spray painting method has the advantages of simple process, high yield, excellent electric connection performance and micron-sized high patterning precision.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic view of the internal structure of a zigzag-shaped thin film thermoelectric device according to the present invention;

FIG. 2 is a schematic diagram of a thin film thermoelectric device according to the present invention;

FIG. 3 is a schematic diagram of an electrode of a thin film thermoelectric device according to embodiment 1 of the present invention;

FIG. 4 is a microstructure of a thermoelectric material of the thin film thermoelectric device of example 1;

FIG. 5 is a schematic structural view of a conventional thermoelectric device "pi" type thin film thermoelectric device;

FIG. 6 is a pictorial view of a thin film thermoelectric device fabricated in example 1;

FIG. 7 is an SEM image of a device object obtained by laser ablation in the step (3) of the device in example 1;

FIG. 8 is a graph showing the results of a test of the power generation performance of the device described in example 1;

FIG. 9 is a micro-topography of thermoelectric materials in the devices of examples 4 and 5;

FIG. 10 is a microtopography of a thermoelectric material in the device of example 6;

FIG. 11 is a schematic diagram of a thermoelectric material obtained by using different laser ablation parameters in example 1, example 7 and example 8;

FIG. 12 is a graph showing the results of example 11 at 1cm²A physical diagram of a thin film device with internal integration 364 versus a thermoelectric leg.

Fig. 13 is a physical diagram of the thin film thermoelectric device of comparative example 2.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.