High-temperature film thermocouple and preparation method thereof

Abstract

The invention belongs to the technical field of thin film sensors, and relates to a high-temperature thin film thermocouple and a preparation method thereof.The high-temperature thin film thermocouple comprises a ceramic substrate, a bonding layer, a sensitive thin film functional layer and an aluminum oxide protective layer which are sequentially arranged from bottom to top, and electrode layers are arranged on the two sides of a wiring end in the sensitive thin film functional layer; the electrode layer is located between the bonding layer or the ceramic substrate and the aluminum oxide protection layer, the electrode layer comprises a GaOx layer printed at normal temperature and an ultrathin layer Au prepared through deposition, and the ultrathin layer Au is arranged above the GaOx layer. The oxidation layer printed on the ceramic substrate or the bonding layer can improve the adhesion of gold, so that the metal-modified electrode layer has excellent conductivity, thermal stability and mechanical stability, and the thickness of the aluminum oxide monolayer arranged on the electrode layer is controlled to be nanoscale, so that the conductivity of the electrode is not influenced, and the conductivity of the electrode is improved. And oxidation of a transition region of the sensitive film functional layer and the electrode layer under a high-temperature condition is effectively inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of thin film sensors and relates to a high-temperature thin film thermocouple and a preparation method thereof. Background Art

[0002] Continuous casting of steel in the metallurgical industry is the main form of modern steel production. The crystallizer is the core component that determines the continuous casting efficiency and the quality of the ingot in the continuous casting process. The temperature change monitoring of the crystallizer copper plate can reflect the temperature field of the ingot, the solidification status of the shell and the operation status of the equipment in real time, prevent the occurrence of steel leakage, improve production efficiency, and reduce energy consumption and production costs. At present, the temperature measurement method of the crystallizer copper plate mainly adopts the thermocouple temperature measurement method. The traditional thermocouple uses an armored structure to protect the thermocouple wire, which increases the size of the device, slows the response speed and is complicated to install, which limits its use scenarios.

[0003] The working environment of the casting is harsh, the working temperature is high, and it has the characteristics of large surface temperature gradient and rapid temperature change. Therefore, thin-film thermocouples with fast response characteristics that can be integrated with the measured components have obvious technical advantages in the above fields and have broad application prospects. However, during the high-temperature (600℃~1400℃) service process, the sensitive materials of the temperature sensor are also seriously affected by complex physical and chemical factors such as high-temperature oxidation, element diffusion, and high-temperature corrosion. The stability and reliability of its high-temperature performance have been greatly reduced, which has become the main technical bottleneck restricting the application of high-temperature thin-film sensors such as thin-film thermocouples.

[0004] Alumina is often used in the preparation of high-temperature thin film sensors such as thin film thermocouples because of its excellent anti-oxidation and thermal stability. It is often used as a high-temperature protective material for thin film sensors. For example, the embedded thin film thermocouple and its preparation method disclosed in the Chinese invention patent with publication number CN114459624A, wherein an electrode groove is formed on a substrate, an electrode film is arranged in the electrode groove, and a protective film is formed on the surface of the substrate where the electrode groove is arranged. In the preparation method, an embedded thin film thermocouple with good stability can be obtained through simple steps, which reduces the difficulty of preparing the thin film thermocouple and is suitable for large-scale production.

[0005] However, technicians in this field have found in the actual preparation process that thin-film thermocouples with protective layers will still experience oxidation and electrode shedding due to reduced adhesion in a long-term high-temperature environment, and the oxidation phenomenon mainly occurs at the overlap between the electrode layer and the sensitive thin-film functional layer. Most of the existing high-temperature thermocouple protective layer technologies are proposed for the protection of sensitive thin-film functional layers, and there has been no extensive research on the protection strategy for the electrode layer. Summary of the invention

[0006] In view of this, an object of the present invention is to provide a high-temperature thin-film thermocouple and a preparation method thereof, which solves the problems raised in the above-mentioned background technology.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A high-temperature thin-film thermocouple comprises a ceramic substrate (1), an adhesive layer (2), a sensitive thin-film functional layer (3) and an aluminum oxide protective layer arranged in sequence from bottom to top, and electrode layers (4) are provided on both sides of the wiring terminal in the sensitive thin-film functional layer (3);

[0009] The electrode layer (4) is located between the bonding layer (2) or the ceramic substrate (1) and the alumina protective layer, and the electrode layer (4) comprises GaO printed at room temperature. x The ultra-thin layer Au is prepared by layer and deposition, and the ultra-thin layer Au is arranged on GaO x above the layer.

[0010] Furthermore, the aluminum oxide protective layer comprises an aluminum oxide single layer (5) and a second aluminum oxide layer (6) disposed above the aluminum oxide single layer (5), and the aluminum oxide single layer (5) is arranged in the region where the sensitive thin film functional layer (3) and the electrode layer (4) are located, and the second aluminum oxide layer (6) is only arranged in the region where the sensitive thin film functional layer (3) is located.

[0011] Furthermore, the aluminum oxide single layer (5) is prepared by atomic layer deposition technology and its thickness is controlled to be 20-50 nm, the thickness of the second aluminum oxide layer (6) is controlled to be 200-400 nm, and the second aluminum oxide layer (6) is deposited on the aluminum oxide single layer (5) by a low-temperature mask.

[0012] Furthermore, the materials selected for the bonding layer (2) include titanium and chromium, and the thickness is controlled to be 20-30 nm;

[0013] Furthermore, the selected materials of the sensitive thin film functional layer (3) include nickel-chromium-nickel-aluminum alloy, tungsten-rhenium alloy and nickel-chromium-silicon alloy-nickel-silicon alloy, and the thickness is controlled to be 400nm.

[0014] Furthermore, the selected materials of the ceramic substrate include aluminum oxide, aluminum nitride, silicon nitride and silicon carbide.

[0015] Furthermore, the thickness of the electrode layer is 20-50 nm, and the GaO x The layer thickness is 10 to 30 nm, and the thickness of the ultra-thin Au is 10 to 20 nm.

[0016] A method for preparing a high-temperature thin-film thermocouple, applied to the high-temperature thin-film thermocouple, is characterized by comprising the following specific steps:

[0017] S1: placing the ceramic substrate (1) in acetone, alcohol, and deionized water in sequence, cleaning the surface of the ceramic substrate (1) by ultrasonic cleaning, and drying the surface of the ceramic substrate (1) in a nitrogen atmosphere after cleaning;

[0018] S2: using magnetron sputtering technology to deposit a metal titanium film with a thickness of 20-30 nm as a bonding layer (2) on the ceramic substrate (1) pretreated by S1;

[0019] S3: depositing a sensitive thin film functional layer (3) on the bonding layer (2) by using photolithography, magnetron sputtering and stripping technology, and controlling the thickness of the sensitive thin film functional layer (3) to be 400 nm;

[0020] S4: depositing an electrode layer (4) on the bonding layer (2) or the ceramic substrate (1) by using room temperature printing, photolithography, magnetron sputtering and stripping technology, and controlling the film thickness of the electrode layer (4) to be 20-50 nm;

[0021] S5: using atomic layer deposition technology to deposit an aluminum oxide single layer (5) on the sensitive thin film functional layer (3) and the electrode layer (4), and controlling the thickness of the aluminum oxide single layer (5) to be 20-50 nm;

[0022] S6: Using mask and magnetron sputtering technology, a second layer of aluminum oxide (6) is sputtered on the sensitive thin film functional layer (3) on which a single layer of aluminum oxide (5) has been deposited, and the thickness of the second layer of aluminum oxide (6) is controlled to be 200-400 nm, thereby finally obtaining a high-temperature thin film thermocouple.

[0023] Furthermore, when depositing the aluminum oxide monolayer (5), N2 is used as a carrier gas, the deposition gas pressure is 2×103Pa, the deposition temperature is 150°C, trimethylaluminum is used as an aluminum precursor, H2O is used as an oxygen source, and trimethylaluminum and H2O are kept at room temperature. The pulse cycle of a single deposition cycle for depositing the aluminum oxide monolayer (5) is: TMA purge 0.25s, N2 purge 5s, H2O purge 0.25s, N2 purge 5s, and the deposition thickness of a single deposition cycle is 0.1nm. The thickness of the aluminum oxide monolayer (5) is controlled to be 20-50nm by controlling the number of pulse cycles of the deposition cycle.

[0024] Furthermore, when the second layer of aluminum oxide (6) is sputtered, the vacuum of the chamber used for magnetron sputtering is 1×10 -6 Pa, the sputtering pressure is 1×10 -3 Pa, using radio frequency magnetron sputtering, the target material is 99.99% high-purity alumina target, the sputtering temperature is room temperature, and the sputtering power is 150W.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention adopts low-temperature mask deposition technology to prepare the second layer of aluminum oxide, which avoids deformation of the photoresist and improves the mask effect, so that the high-temperature thin-film thermocouple can be integrated and compatible with small-size sensors, and the oxide layer printed on the ceramic substrate or the bonding layer can improve the adhesion of gold, so that the metal-modified electrode layer has excellent conductivity, thermal stability and mechanical stability.

[0027] 2. The double-layer aluminum oxide protective layer (aluminum oxide single layer and a second aluminum oxide layer) in the high-temperature thin-film thermocouple is prepared by atomic layer deposition and magnetron sputtering technology. The deposition preparation can be completed under low temperature conditions, and no complicated post-processing such as annealing is required, which simplifies the process flow. Since the thermal expansion coefficient of the aluminum oxide protective layer is similar to that of the ceramic substrate, the thermal stress generated is small, and it can maintain good adhesion with the substrate under high temperature environment. The double-layer aluminum oxide protective layer can still maintain a high resistance value under a high-temperature working environment of 600°C, which can effectively improve the electrical insulation performance, ensure the stability of the adhesion of the thin-film thermocouple of the protective layer under long-term high-temperature environment, and avoid oxidation and electrode detachment.

[0028] 3. The present invention controls the thickness of the aluminum oxide single layer arranged on the electrode layer to be at the nanometer level, which can effectively inhibit the oxidation of the transition area between the sensitive thin film functional layer and the electrode layer under high temperature conditions without affecting the conductivity of the electrode, thereby ensuring the stable operation of the thin film thermocouple under high temperature conditions. In addition, since the thermal expansion coefficients of the aluminum oxide single layer and the ceramic substrate are similar, and the ceramic substrate, the electrode layer and the aluminum oxide protective layer form a sandwich structure, the adhesion between the electrode layer and the ceramic substrate is improved during the operation of the thin film thermocouple, reducing the risk of its falling off.

[0029] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0031] Figure 1 This is a schematic diagram of the front structure of a high-temperature thin-film thermocouple in the embodiment; Figure 2 It is a schematic diagram of the bottom-up structure of a high-temperature thin-film thermocouple in the embodiment.

[0032] Figure numerals: 1 - ceramic substrate; 2 - bonding layer; 3 - sensitive thin film functional layer; 4 - electrode layer; 5 - aluminum oxide single layer; 6 - second aluminum oxide layer. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Example 1

[0037] like Figure 1 As shown, a high-temperature thin-film thermocouple comprises a ceramic substrate 1, on which a bonding layer 2 and a sensitive thin-film functional layer 3 are deposited, on which the sensitive thin-film functional layer 3 is covered with an aluminum oxide protective layer, the aluminum oxide protective layer is composed of an aluminum oxide single layer 5 covering the sensitive thin-film functional layer 3 and a second aluminum oxide layer 6, the second aluminum oxide layer 6 is arranged on the aluminum oxide single layer 5, the aluminum oxide single layer 5, the sensitive thin-film functional layer 3 and the bonding layer 2 form a closed filling area, in which an electrode layer 4 is arranged, and the ceramic substrate 1, the bonding layer 2, the electrode layer 4 and the aluminum oxide single layer 5 form a sandwich structure, and the bonding layer 2 is printed with GaO at room temperature. xlayer and deposit an ultra-thin layer of Au as the electrode layer 4, with a thickness of about 20 nm. x The thickness of is 10 nm, and the thickness of the ultra-thin Au is 10 nm.

[0038] The aluminum oxide single layer 5 is prepared by atomic layer deposition technology and its thickness is controlled to be 20-50 nm, the second aluminum oxide layer 6 is prepared by low temperature deposition and its thickness is controlled to be 200-400 nm, and the second aluminum oxide layer 6 is deposited on the aluminum oxide single layer 5 through a low temperature mask;

[0039] Furthermore, conventional masking methods include photolithography and metal mask hard mask, etc. Under high temperature conditions, photoresist will be difficult to strip due to denaturation, and metal mask will deform at high temperature, resulting in poor masking effect, which is difficult to be compatible with small-sized sensors. Therefore, a technology for depositing the second layer of aluminum oxide at low temperature or room temperature is required. The specific deposition method proposed in this application is a mask combined with room-temperature magnetron sputtering technology to deposit the second layer of aluminum oxide 6;

[0040] In another embodiment, GaO is directly printed on the ceramic substrate 1 at room temperature. x layer and deposit an ultra-thin layer of Au as electrode layer 4, in which the printed GaO x The technical characteristics of the layer can make it possible to combine ultra-thin Au layers with GaO x In the layer, the metal-modified oxide film layer has excellent conductivity, thermal stability and mechanical stability to improve the adhesion of gold, and the ceramic substrate 1, electrode layer 4 and aluminum oxide single layer 5 form a sandwich structure, which improves the adhesion between the electrode and the substrate during the operation of the thin film thermocouple and reduces the risk of it falling off.

[0041] This embodiment also provides a method for preparing a high-temperature thin film temperature thermocouple, which specifically includes the following steps:

[0042] S1: placing the ceramic substrate 1 in acetone, alcohol and deionized water in sequence, cleaning the surface of the substrate by ultrasonic cleaning, and drying it in a nitrogen atmosphere after cleaning;

[0043] S2: using magnetron sputtering technology to deposit a metal titanium film with a thickness of 20-30 nm as a bonding layer 2 on the ceramic substrate 1 pretreated in step S1;

[0044] S3: depositing a sensitive thin film functional layer 3 on the bonding layer 2 by using photolithography, magnetron sputtering, and stripping technology, wherein the thickness of the sensitive thin film functional layer 3 is 400 nm;

[0045] S4: Preparation of GaO by room temperature printing x Layer, GaO x The layer thickness is 10 to 30 nm, using photolithography, magnetron sputtering, and stripping technology GaOx An ultra-thin Au layer is deposited on the GaO x The thickness of the electrode layer 4 composed of the ultra-thin Au layer is controlled at 20-50nm;

[0046] S5: Atomic layer deposition technology is used to deposit an aluminum oxide single layer 5 on the sensitive thin film functional layer 3 and the electrode layer 5, N2 is used as the carrier gas, the deposition pressure is 2×103Pa, the deposition temperature is 150°C, trimethylaluminum is used as the aluminum precursor, H2O is used as the oxygen source, trimethylaluminum and H2O are kept at room temperature, and the pulse cycle of a single deposition cycle for depositing the aluminum oxide single layer 5 is: TMA purge 0.25s, N2 purge 5s, H2O purge 0.25s, N2 purge 5s, and the deposition thickness of a single deposition cycle is 0.1nm. By controlling the number of pulse cycles of the deposition cycle, the thickness of the aluminum oxide single layer 5 deposited is 20-50nm;

[0047] S6: Using mask and magnetron sputtering technology, a second layer of aluminum oxide 6 is sputtered on the sensitive thin film functional layer 3 on which the aluminum oxide single layer 5 has been deposited. The vacuum of the chamber body is 1×10 -6 Pa, the sputtering pressure is 1×10 -3 Pa, using radio frequency magnetron sputtering, the target material is 99.99% high-purity aluminum oxide target, the sputtering temperature is room temperature, the sputtering power is 150W, and the sputtering time is controlled to obtain a second layer of aluminum oxide 6 with a thickness of 200-400nm, and finally a high-temperature thin film thermocouple is obtained.

[0048] In another embodiment, the aluminum oxide single layer 5 is prepared by atomic layer deposition technology and the thickness is controlled to be 20-50 nm, and the second aluminum oxide layer 6 is prepared by magnetron sputtering technology and the thickness is controlled to be 200-400 nm.

[0049] The materials selected for the ceramic substrate 1 include but are not limited to aluminum oxide, aluminum nitride, silicon nitride, and silicon carbide.

[0050] The materials used for the bonding layer 2 include but are not limited to metal elements such as titanium and chromium. The thickness of the bonding layer 2 is controlled to be 20-30 nm.

[0051] The selected materials of the sensitive thin film functional layer 3 include but are not limited to nickel-chromium-nickel-aluminum alloy, tungsten-rhenium alloy, nickel-chromium-silicon alloy-nickel-silicon alloy, etc. The thickness of the sensitive thin film functional layer 3 is controlled to be 400nm.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A high-temperature thin-film thermocouple, comprising a ceramic substrate (1), an adhesive layer (2), a sensitive thin-film functional layer (3) and an alumina protective layer arranged in sequence from bottom to top, and electrode layers (4) are provided on both sides of the terminal in the sensitive thin-film functional layer (3), characterized in that: The electrode layer (4) is located between the bonding layer (2) or the ceramic substrate (1) and the alumina protective layer, and the electrode layer (4) comprises GaO printed at room temperature. x The ultra-thin layer Au is prepared by layer and deposition, and the ultra-thin layer Au is arranged on GaO x above the layer.

2. The high temperature thin film thermocouple according to claim 1, characterized in that: The aluminum oxide protective layer comprises an aluminum oxide single layer (5) and a second aluminum oxide layer (6) arranged above the aluminum oxide single layer (5), and the aluminum oxide single layer (5) is arranged in the area where the sensitive thin film functional layer (3) and the electrode layer (4) are located, and the second aluminum oxide layer (6) is only arranged in the area where the sensitive thin film functional layer (3) is located.

3. The high temperature thin film thermocouple according to claim 2, characterized in that: The aluminum oxide single layer (5) is prepared by atomic layer deposition technology and its thickness is controlled to be 20-50 nm, the thickness of the second aluminum oxide layer (6) is controlled to be 200-400 nm, and the second aluminum oxide layer (6) is deposited on the aluminum oxide single layer (5) by a low-temperature mask.

4. The high temperature thin film thermocouple according to claim 2, characterized in that: The materials selected for the bonding layer (2) include titanium and chromium, and the thickness is controlled to be 20-30 nm.

5. The high temperature thin film thermocouple according to claim 2, characterized in that: The selected materials of the sensitive thin film functional layer (3) include nickel-chromium-nickel-aluminum alloy, tungsten-rhenium alloy and nickel-chromium-silicon alloy-nickel-silicon alloy, and the thickness is controlled to be 400nm.

6. The high temperature thin film thermocouple according to claim 2, characterized in that: The selected materials of the ceramic substrate include aluminum oxide, aluminum nitride, silicon nitride and silicon carbide.

7. The high temperature thin film thermocouple according to claim 2, characterized in that: The thickness of the electrode layer is 20-50 nm, and the GaO x The layer is 10 to 30 nm, and the thickness of the ultra-thin Au is 10 to 20 nm.

8. A method for preparing a high temperature thin film thermocouple, applied to the high temperature thin film thermocouple described in any one of claims 1 to 7, characterized in that: The specific steps include: S1: placing the ceramic substrate (1) in acetone, alcohol, and deionized water in sequence, cleaning the surface of the ceramic substrate (1) by ultrasonic cleaning, and drying the surface of the ceramic substrate (1) in a nitrogen atmosphere after cleaning; S2: using magnetron sputtering technology to deposit a metal titanium film with a thickness of 20-30 nm as a bonding layer (2) on the ceramic substrate (1) pretreated by S1; S3: depositing a sensitive thin film functional layer (3) on the bonding layer (2) by using photolithography, magnetron sputtering and stripping technology, and controlling the thickness of the sensitive thin film functional layer (3) to be 400 nm; S4: depositing an electrode layer (4) on the bonding layer (2) or the ceramic substrate (1) by using room temperature printing, photolithography, magnetron sputtering and stripping technology, and controlling the film thickness of the electrode layer (4) to be 20-50 nm; S5: using atomic layer deposition technology to deposit an aluminum oxide single layer (5) on the sensitive thin film functional layer (3) and the electrode layer (4), and controlling the thickness of the aluminum oxide single layer (5) to be 20-50 nm; S6: Using mask and magnetron sputtering technology, a second layer of aluminum oxide (6) is sputtered on the sensitive thin film functional layer (3) on which a single layer of aluminum oxide (5) has been deposited, and the thickness of the second layer of aluminum oxide (6) is controlled to be 200-400 nm, thereby finally obtaining a high-temperature thin film thermocouple.

9. The method for preparing a high temperature thin film thermocouple according to claim 8, characterized in that: When depositing the aluminum oxide monolayer (5), N2 is used as a carrier gas, the deposition gas pressure is 2×103Pa, the deposition temperature is 150°C, trimethylaluminum is used as an aluminum precursor, H2O is used as an oxygen source, and trimethylaluminum and H2O are kept at room temperature. The pulse cycle of a single deposition cycle of depositing the aluminum oxide monolayer (5) is: TMA purge 0.25s, N2 purge 5s, H2O purge 0.25s, N2 purge 5s, and the deposition thickness of a single deposition cycle is 0.1nm. The thickness of the aluminum oxide monolayer (5) is controlled to be 20-50nm by controlling the number of pulse cycles of the deposition cycle.

10. The method for preparing a high temperature thin film thermocouple according to claim 8, characterized in that: When the second layer of aluminum oxide (6) is sputtered, the vacuum of the chamber used for magnetron sputtering is 1×10 -6 Pa, the sputtering pressure is 1×10 -3 Pa, using radio frequency magnetron sputtering, the target material is 99.99% high-purity alumina target, the sputtering temperature is room temperature, and the sputtering power is 150W.

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