CN106521457A - Heating device for high-temperature thin film deposition - Google Patents

Abstract

The invention belongs to the technical field of thin film preparation, in particular to a heating device for high temperature thin film deposition. Heating device of the present invention comprises two electrode groups; Electric current I is imported on the metal substrate base band from two edges of metal substrate base band by electrode, and flows on it; Alloy, etc.) under the action of its own resistance, heat up to the temperature required for YBCO growth, and the deposition area is between the two electrode groups. The device principle and structure of the present invention are simple; heating is rapid, and energy efficiency is high; It can be used for the heating of strip-shaped metal substrates or strip-shaped metal substrates prepared with (conductive or insulating) buffer layers; Due to the discharge caused by poor contact, this heating method can realize the continuous winding preparation of single-sided or double-sided YBCO long strips.

Description

A heating device for high temperature thin film deposition

technical field

The invention belongs to the technical field of thin film preparation, and in particular relates to the preparation of thin films in a high-temperature environment on a stationary or moving long strip-shaped metal substrate, which can be used in thin film preparation processes such as sputtering, evaporation, PLD, and MOCVD, and is specifically a method for high-temperature thin films. Deposition heating device.

Background technique

In the field of thin film preparation, in order to realize the controlled growth of the thin film, and then achieve the purpose of controlling the physical and chemical properties of the thin film, it is usually necessary to heat the substrate on which the thin film grows.

Many manufacturers and research institutes are concentrating on designing more superior reaction chambers. To match the design of the reaction chamber, the heater must also be improved accordingly. Since the gas reaction in the chamber has strict requirements on the temperature, it is necessary to develop a high-performance thin film deposition heating system with the characteristics of uniform temperature, fast heating and cooling, fast stability, and good repeatability. Specifically, the film deposition heating system must: have the ability to quickly increase the temperature to the high temperature required to grow each layer of film; after reaching the set temperature, it can stably maintain this temperature without changing, which not only has thermal stability; Realize the rapid rise and fall of temperature in a short period of time, thereby forming a steep layer on the wafer; can control the heater to achieve different set temperatures to meet the needs of growing multi-layer deposition films; have good repeatability, so that every time The grown material has the same properties. At present, there are two main heating methods for preparing thin films on the market: resistance wire heating and high-frequency induction heating.

Resistance wire heating is to use a resistance wire with relatively high resistance and pass a large current to make the resistance wire generate a large amount of Joule heat, and the resistance wire will heat up to 1500-2000°C in a short time. Then the high-temperature resistance wire transfers heat to the graphite base, and the heat transfer form is mainly radiation, so this heat method is also called radiation heating. The main advantages of using resistance wire heating are simple structure, simple heating principle, convenient temperature control, etc.; and as a traditional heating method, its technology is very mature. The main disadvantages are high cost, relatively difficult maintenance, and relatively slow heating and cooling speed. Moreover, this heating method requires a good design of the number and spatial distribution of the heating elements to ensure that the substrate obtains a sufficiently high and evenly distributed temperature, so the design of the heater is more difficult and requires a larger space.

Induction heating is mainly based on the three basic principles of electromagnetic induction, skin effect and heat conduction, that is, the conductor is placed in a high-frequency electromagnetic field, so that a current of the same frequency is induced in the conductor, and heat is generated under the action of the current. Induction heating has been used in industry for more than 40 years in a wide variety of applications. Compared with traditional heating equipment, high-frequency induction heating has many advantages: high heating temperature and non-contact heating, which is very superior for cavities with complex structures; high heating efficiency and energy saving; The surface of the heating object is less oxidized; it is easy to realize automatic control; the working environment is good; it is clean and pollution-free. The disadvantage is that if this method is used to directly heat the substrate, the substrate must be conductive, and the shape is regular, the resistivity distribution is uniform, and there is a skin effect (when there is an alternating current or an alternating electromagnetic field in the conductor, the inside of the conductor The current distribution is uneven, and the current is concentrated in the "skin" part of the conductor, that is to say, the current is concentrated in the thin layer on the outside of the conductor. The closer to the surface of the conductor, the greater the current density, and the actual current inside the conductor is smaller. As a result, the conductor's The resistance increases, so that its power loss also increases.), and the high-frequency magnetic field will affect the surrounding equipment.

The above two heating methods have their own advantages and disadvantages, and what they have in common is that the energy required to raise the temperature of the substrate is transferred or converted from the outside. However, in the process of transfer or conversion, very little energy is actually required to heat up the substrate, and most of the energy is wasted by the heating element or the power supply itself. When a film is prepared on a long strip-shaped metal substrate, although radiation heating can be used for heating such a strip-shaped metal substrate, the heating source must be well designed to ensure that the temperature along the length and width of the metal substrate Evenly distributed, and such heating sources are often more complex. When high-frequency induction is used to heat thin metal strips, the frequency of the electric field is required to be high to ensure that the skin depth of the alternating electric field is limited to the inside of the material to improve energy efficiency. At high frequencies, the coupling of high-frequency electric fields is easily generated in the vacuum chamber to excite plasma. The simultaneous occurrence of induction heating and plasma is disadvantageous for accurate temperature control.

When heating a strip-shaped metal substrate, compared with the above two common heating methods, it is simpler and more energy efficient to use the resistance of the metal itself to generate heat by introducing current into the metal substrate. At present, a related patent (CN104046963A) adopts a similar method to heat the metal substrate. But in this patent, when the heating electrode heats the moving metal substrate base band, it often causes discharge between the electrode sheet and the base band due to poor contact. The local high temperature caused by this discharge will melt the base tape and affect the surface morphology and electrical conductivity of the YBCO tape.

Therefore, in view of the deficiencies of existing heating methods when heating strip-shaped metal substrates, the patent of the present invention proposes a new heating method and device as follows.

Contents of the invention

In view of the above existing problems or deficiencies, in order to solve the problem of providing an efficient, uniform and reliable heating method for a stationary or moving strip-shaped metal baseband substrate, the present invention provides a heating device for high-temperature thin film deposition.

The heating device for high-temperature film deposition includes a first electrode group and a second electrode group.

The first electrode group and the second electrode group are the same, and are arranged side by side on both sides of the thin film growth area; the two electrode groups are located between the rotating shafts of the two substrate winding disks.

The electrode group is composed of a ceramic plate, a conductive metal sheet, a silver tungsten Ag-W rod, an elastic support device and a resistance metal sheet; the ceramic plate has two pieces, which are used to install the conductive metal sheet and can slide freely on the bracket; There are 12-40 metal sheets, which are equally spaced and fixed in pairs on the inner surfaces of two ceramic plates, with Ag-W rods welded on the upper ends, and between the two opposite Ag-W rods is the channel of the metal substrate baseband. Each pair of Ag-W rods is electrically connected to each other and is electrically connected to the power interface; each pair of resistive metal sheets constitutes an electrode unit, and each electrode unit is electrically connected through a current distribution circuit; the current distribution circuit is a series resistance, each The electrode units are respectively connected to the connection points between the corresponding adjacent resistors; the two ceramic plates are clamped between the Ag-W rods of each electrode unit through the elastic supporting device so that the metal substrate substrate is clamped.

Said channel refers to the position of the metal substrate base tape in the working state, that is, when it is at rest or the movement path of the metal substrate base tape between the winding reels; sticks in contact.

The power interface refers to a circuit interface connected to an external power supply.

Further, the elastic supporting device is a screw passing through two ceramic plates and a matching nut and spring, and the conductive metal sheet is fixed on the ceramic plate through a spring washer.

Further, the specific proportion distributed by the current distribution circuit is determined by the value of the selected resistor.

Further, the conductive metal sheet is connected to the screw in contact with the distribution resistor through a copper wire, so as to realize uniform current distribution.

Further, the Ag-W rod is a cylindrical rod.

Further, positioning slits are also provided at both ends of the electrode group to ensure that the metal substrate base band is always kept perpendicular to the Ag-W rod during the moving process.

The reason why Ag-W alloy rods are used is that during the experiment, the current for heating the metal substrate baseband is large (above 20A), the temperature of the metal substrate baseband and the vacuum chamber pressure (300-600Pa) are high, which requires electrodes It has a good electrical contact with the baseband of the metal substrate, otherwise it will cause discharge between the baseband and the electrodes and burn the baseband and electrodes, while the Ag-W alloy rod has the characteristics of high conductivity and high melting point, and has strong oxidation resistance , and has the function of suppressing the arc, which is very suitable for this environment.

Work flow of the present invention is: electric current I imports on the metal substrate base band from two edges of metal substrate base band by electrode, and flows on it; Under the action of its own resistance, it generates heat to reach the temperature required for YBCO growth, and the deposition area is between the two electrode groups.

Since the metal substrate baseband and the electrode are relatively sliding, the key to the heating method of the metal substrate baseband is how to ensure that the baseband and the electrode still have good electrical contact in the state of relative sliding, otherwise it will cause the electrode Ag-W A discharge occurs between the chip and the metal substrate baseband. The local high temperature caused by this discharge can melt the base tape. In addition, under the winding tension of the winding reel, this melting may even cause the base tape to snap, resulting in deposition failure. Since the ceramic plate can slide freely on the bracket, the size of the contact force can be adjusted by the spring on the bracket, and the conductive metal sheet is fixed on the ceramic plate through the spring washer, and the Ag-W rod is a cylindrical rod, so that the baseband can always Maintain good electrical contact with the Ag-W rod. In addition, positioning slits are also provided at both ends of the two electrode groups to ensure that the base band is always kept perpendicular to the Ag-W rod during the moving process.

This heating method has obvious advantages:

①The baseband of the metal substrate generates heat by itself, and the temperature gradient outside the baseband is very large, and the temperature away from the surface of the baseband drops rapidly. This makes the temperature of the shower head baked by the heat of the baseband significantly lower. In this way, the decomposition reaction of the metal-organic source at the outlet is effectively suppressed, which not only improves the utilization rate of the metal-organic source, but also eliminates the deposition of reaction products at the outlet of the shower head, so it is more conducive to the long-term stable preparation of YBCO strips ; ②Due to the large gradient of the spatial temperature field, the shower head can be very close to the baseband but its own temperature will not be too high, so the deposition rate of the YBCO film and the utilization rate of metal-organic sources are higher; ③The heating method is mainly through Heat conduction heats up the surface, so the heating is faster and more efficient, so it is more energy-saving; ④During the heating process, the current only flows through the metal baseband part between the two electrodes, and the deposition area is between the two electrodes, so it is very energy-saving. It is easy to expand the deposition area by increasing the distance between electrodes; ⑤ Since the space between the two electrodes is open, shower heads can be set on both surfaces of the metal substrate to realize the preparation of double-sided YBCO strips. As long as the thickness and structure of the buffer layer deposited on the two surfaces of the metal base tape are consistent, the growth temperature of the YBCO film on both sides can be kept consistent, thereby preparing a double-sided YBCO strip with uniformity on both sides.

The invention can rapidly heat the metal substrate to over 800° C., and the temperature distribution on the metal substrate is uniform, and the uniform distribution interval can also be easily adjusted according to needs, and the energy utilization rate is high. Combined with the segmental heating and winding of the metal substrate, the continuous winding preparation of multi-layer films can be realized. These are particularly important for the industrialized preparation of thin films, which can improve the quality of the prepared thin films and reduce the preparation cost of the thin films. In addition, the heating method can also easily realize the preparation of consistent double-sided thin films on both sides of the metal substrate at the same time, which plays an important role in improving the use efficiency of the metal substrate, reducing costs and improving performance.

In summary, the present invention has simplicity, the advantage that energy efficiency is high; Can be used for the heating of strip-shaped metal substrate or the strip-shaped metal substrate that is prepared with (conductive or insulating) buffer layer on it, also can realize Segmental heating of the metal substrate, and the metal substrate can be stationary or moving; realize the continuous winding preparation of multi-layer films, and realize the preparation of consistent double-sided films on both sides of the metal substrate at the same time, which is very important for improving the metal substrate. Efficiency in use, cost reduction, and performance improvement play an important role.

Description of drawings

Fig. 1 is a three-dimensional structure and a schematic diagram of circuit connection of the present invention;

Fig. 2 is the schematic diagram of the three-dimensional structure of the electrode group of the embodiment;

Fig. 3 is a schematic top view corresponding to the electrode group in Fig. 2;

Fig. 4 is a schematic view corresponding to the right side of the electrode group in Fig. 2;

Fig. 5 is the equivalent calculation circuit diagram of heating electrode;

Fig. 6 is the X-ray diffraction 2theta scanning figure of the YBa ₂ Cu ₃ O _7-x (YBCO) thin film of three different positions on the belt-shaped metal substrate;

Fig. 7 is the X-ray diffraction ω scan and the phi scan curve of the YBCO thin film of middle position on the strip metal substrate;

Reference signs: 1. ceramic insulating plate, 2. conductive metal sheet, 3. Ag-W rod, 4. wire, 5. metal substrate baseband, 6. current distribution resistor, 7. metal screw, 8. metal nut , 9. Metal screw, 10. Spring, 11. Locating slot.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

The device shown in Fig. 1 was used for the preparation of second-generation high-temperature superconducting coated conductor YBa ₂ Cu ₃ O _7-x (YBCO) thin film. Cut a section of Hastelloy substrate (LaMnO ₃ /homo-epiMgO/IBAD-MgO/SDP-Y ₂ O ₃ /Hastelloy) with a width of 1 cm and a length longer than that of the growth region, on which a buffer layer film has been deposited. Grinding the two sides to remove the oxides deposited on the side to achieve good electrical contact, and then welding its end to end to the stainless steel traction belt by welding, and finally fixing the metal substrate base belt according to the above-mentioned embodiment, and the stainless steel The leash is attached to the winding reel and connected to the electrical circuit. Evacuate the growth chamber of the MOCVD system to below 1Pa. Weighed metal-organic sources were 128.4mg of Y(TMHD) ₃ , 143mg of Gd(TMHD) ₃ , 696mg of Ba(TMHD) ₂ , 356.885mg of Cu(TMHD) ₂ and 16.9175mg of Zr(TMHD) ₄ ( thmd: 2,2,6,6-tetramethyl-3,5-heptanedione), dissolved together in 5ml tetrahydrofuran solvent, and ultrasonically oscillated to fully dissolve to form a uniform and clear metal-organic source solution. Turn on the power supply, and pass a 26A current (voltage is about 30V) to the baseband of the metal substrate. Turn on the pulling motor to pull the metal substrate to the growth area. After the temperature is stabilized, the metal-organic source solution is sent to the evaporation chamber at 300°C by using a peristaltic pump for flash evaporation to become metal-organic source vapor. Driven by Ar gas, the organic source vapor is mixed with O ₂ and N ₂ O gases. After passing through the gas pipeline at 320°C, it is sprayed by the shower head onto the metal substrate passing through the growth area to react to form a YBCO film.

In this embodiment, the electrode group shown in FIG. 2 is used for heating, and its top view and right view are shown in FIG. 3 and FIG. 4 respectively.

The equivalent calculation circuit diagram of the heating electrode is shown in Fig. 5. In Figure 5, the distribution resistance is related to the metal substrate, the distribution spacing of Ag-W rods on the ceramic plate and the number of groups of Ag-W rods. Assuming that the number of groups of Ag-W rods is 8, that is, there are 16 Ag-W alloy rods on two ceramic plates, and assuming that the resistance of Ag-W is negligible relative to the resistance of the baseband, the equivalent circuit of the electrodes and the baseband is as follows: Figure 5 shows. In Figure 5, R represents the equivalent resistance of the baseband between two adjacent groups of Ag-W rods, expressed as the formula R=ρ×l/(w×d), where ρ represents the resistivity of the metal baseband, w and d Respectively represent the width and thickness of the base band, l represents the center-to-center distance of two adjacent groups of Ag-W rods.

Rn (n=1, 2, ..., 7) represents the current distribution resistor, and the Ag-W rod is equivalent to the connection between R and Rn in the circuit. In order to make the current carried by each group of Ag-W sheets equal, assuming that the current is I, the total current output by the current source is 8I. According to Kirchhoff's law, the distribution resistance Rn can be expressed as the formula Rn=R×n/(8-n). ) calculation results are cropped.

Then put the prepared YBCO sample into a tube furnace with an atmospheric pressure O ₂ , keep it at 500 degrees Celsius for 30 minutes, and finally take out the thin film sample for characterization.

The structures of the prepared thin films are shown in Fig. 6 and Fig. 7 .

Figure 6 shows that the diffraction peaks of the (00l) planes at three different positions are very sharp, and the intensity of the diffraction peaks is similar, and there are no miscellaneous peaks. The YBCO grains at the three positions on the surface are all pure c-axis growth, which also shows that The crystallization quality of the YBCO thin film on the tape-shaped metal substrate is very uniform.

The FWHM values of the two curves in Figure 7 are 1.38° and 2.78°, respectively, indicating that the out-of-plane and in-plane orientation of the YBCO film at this position is very good, and has a biaxial texture similar to that of the YBCO film on a single crystal.

It can be seen that the crystal quality and orientation of the YBCO film prepared by the heating device of the present invention are good.

In summary, this baseband heating method effectively overcomes the shortcomings of the original heating system. Its principle and structure are simple, heating is rapid, and energy efficiency is high. By eliminating the discharge caused by poor contact between the electrode and the baseband, this heating method can Realize the continuous winding preparation of single-sided or double-sided YBCO long strips.

Claims (7)

1. it is a kind of for high temperature film deposition heater, including first electrode group and second electrode group, it is characterised in that：

First electrode group is identical with second electrode group, and is juxtaposed on film-growth zone both sides；Two electrode groups are located at two Between substrate winder rotating shaft；

The electrode group is made up of ceramic wafer, conductive metal sheet, silver-colored tungsten Ag-W rods, resilient supporting unit and resistance metal piece；Pottery Porcelain plate has two panels, for installing conductive metal sheet, and can be on support slidably；Conductive metal sheet has 12-40, equidistantly And the inner surface of two panels ceramic wafer is fixed in couples, its upper end is welded with Ag-W rods, is metal liner between two relative Ag-W rods The passage of base band, each paired Ag-W rods are electrically connected to each other, and electrically connect with power interface formation；Each pair resistance metal piece An electrode unit is constituted, each electrode unit is formed by current dividing circuit and electrically connected；Current dividing circuit is the electricity of series connection Resistance, each electrode unit are connected to the tie point between correspondence adjacent resistor；Two panels ceramic wafer is made by resilient supporting unit Obtain metal substrate base band to be held between the Ag-W rods of each electrode unit；

When the passage refers to that the position of metal substrate base band under working condition is i.e. static or metal substrate base band winder it Between running path；Passage is located between paired conductive metal sheet, and its both sides of the edge is contacted with Ag-W rods；

The power interface refers to the circuit interface being connected with external power source.

2. the heater of high temperature film deposition is used for as claimed in claim 1, it is characterised in that：The resilient supporting unit is Through the screw rod and supporting nut and spring of two panels ceramic wafer, conductive metal sheet is fixed on ceramic wafer by spring shim On.

3. the heater of high temperature film deposition is used for as claimed in claim 1, it is characterised in that：The current dividing circuit point The concrete ratio matched somebody with somebody is determined by the value of selected resistance.

4. the heater of high temperature film deposition is used for as claimed in claim 1, it is characterised in that：The conductive metal sheet passes through Copper cash is connected on the screw with distribution Ohmic contact, to realize uniform CURRENT DISTRIBUTION.

5. the heater of high temperature film deposition is used for as claimed in claim 1, it is characterised in that：The Ag-W rods are cylinder Rod.

6. the heater of high temperature film deposition is used for as claimed in claim 1, it is characterised in that：The two ends of the electrode group are also Positioning slit is provided with, it is vertical with the holding of Ag-W rods all the time in metal substrate base band moving process to ensure.

7. the heater of high temperature film deposition is used for as claimed in claim 1, and its workflow is specific as follows：

Electric current I is imported in metal substrate base band from two edges of metal substrate base band by electrode, and is flowed over；Gold Category substrate base band is generated heat in the presence of self-resistance and reaches the required temperature of YBCO growths, and crystallizing field is in two electrode groups Between.