CN104711527A - Method for magnetron sputtering low-temperature preparation of TiN film - Google Patents

Abstract

The invention relates to a method for preparing TiN thin films by reactive magnetron sputtering at low temperature. Through the improvement of traditional magnetron sputtering technology, a plasma region is introduced into a vacuum chamber, and a Ti metal target is sputtered by intermediate frequency pulse direct current or direct current sputtering. , and control the working gas pressure, temperature, time, sputtering power and other process conditions to deposit TiN thin film on the substrate. The method can produce a TiN thin film with good performance in low temperature environment, the crystallinity, compactness and hardness of the thin film are improved, the surface roughness is small, the thin film and the substrate have high binding force, and it is difficult to produce local shedding. The invention can provide samples for the experimental research or industrial production of the hard film.

Description

A method for preparing TiN thin films by magnetron sputtering at low temperature

technical field

The invention belongs to the field of hard films. In particular, it relates to a new process for preparing TiN thin films by plasma-assisted magnetron sputtering in a low-temperature environment, and a new process for preparing TiN hard films by using plasma-assisted twin-target pulsed DC magnetron sputtering technology.

Background technique

As a multifunctional material, titanium nitride (TiN) film has high temperature stability, high hardness, low electrical conductivity, low friction coefficient, corrosion resistance and other properties, and is used in hard coatings, high temperature resistant coatings and decorative coatings. It has a wide range of applications in many fields. At the same time, due to its excellent solar spectrum selectivity and high temperature oxidation resistance, titanium nitride thin films have attracted much attention in the application of medium and high temperature solar selective absorption coatings. There are many methods for preparing titanium nitride thin films, mainly including arc ion plating and magnetron sputtering. The arc ion plating method is widely used in industrial production due to its fast deposition rate and strong bonding force between the film and the substrate. However, the film prepared by this arc evaporation will retain the micron-sized particles ejected from the cathode material, resulting in a decrease in the surface roughness and friction coefficient of the film. Increase, the compactness of the film is affected, thus limiting the advancement of the arc ion plating method to the field of high-performance thin films. Compared with the arc ion plating method, the magnetron sputtering method can obtain a titanium nitride film with low surface roughness and good uniformity. However, the traditional magnetron sputtering method also has its shortcomings. The high-density plasma region confined by the magnetic field can only be distributed near the target surface, and the plasma density in the entire vacuum chamber is low. Due to the low ionization rate in the coating process, it is difficult to obtain a high stoichiometric titanium nitride film while ensuring a high deposition rate. Moreover, in order to ensure the crystallinity of the titanium nitride film, the entire deposition process must be kept constant. High temperature (usually 300°C) environment. This greatly limits the size and type of workpieces to be plated. For example, most of the materials commonly used in friction and mold parts, data storage (Data Storage) and silicon chip channels (TSV) in the field of micro-electromechanical systems require the coating process temperature Not exceeding 200-250°C. Therefore, the production efficiency and application range of the traditional magnetron sputtering coating technology are restricted.

Contents of the invention

The object of the present invention is to provide a preparation method of TiN hard coating. The method adopts the plasma reactive magnetron sputtering technology, the deposition temperature is a low temperature environment, and the prepared TiN hard film has good performance.

The present invention first adopts the twin target pulsed DC magnetron sputtering method, by introducing a plasma region in the vacuum chamber to increase the plasma density in the vacuum chamber, when the substrate passes through the plasma region near the sputtering Ti target and reacts with nitrogen, it enters the plasma The plasma region generated by the source is further nitridated, and a TiN film with a high stoichiometric ratio can be formed. And depending on the process requirements, the deposition temperature can be kept at room temperature or at a low temperature state, realizing the low temperature (room temperature-200°C) deposition of titanium nitride thin films.

The source used to generate the plasma may be an anode layer linear ion source, a radio frequency ion source, a Hall ion source or a Kaufmann ion source.

The unbalanced magnetic field magnetron sputtering cathode used as a plasma source needs to use hard-to-sputter target materials, such as aluminum oxide or titanium oxide. No matter what material is used, the power of the RF power supply must be controlled at In the range of 100-1000W, it is used to ensure that during the film deposition process, no material is sputtered out of the target used as the plasma generation source, so as not to cause film pollution, that is, the maximum power added to the target by the RF power supply is less than that of the target The minimum power at which the material is splashed.

The magnetron sputtering cathode used to prepare TiN hard coating adopts intermediate frequency power supply or pulsed DC power supply, and the sputtering target material is Ti metal. When preparing thin films, control the pressure of the working gas (argon) at 0.1Pa-3Pa; control the reaction The pressure ratio of gas (nitrogen) to working gas (argon) is 1:5-50; the temperature is constant at a certain value from room temperature to 200°C; the sputtering power supply current is 1A-30A, etc., to deposit TiN film on the substrate .

Advantage of the present invention:

1) Compared with the TiN hard film prepared by the traditional magnetron sputtering method, the crystallinity, compactness and hardness of the film prepared by this technology are improved, the surface roughness is small, the film and the substrate have a high bonding force, and it is difficult to Partial exfoliation

2) Compared with the traditional magnetron sputtering method to prepare TiN hard film, the method of the present invention enlarges the plasma area in the vacuum chamber, improves the gas ionization rate in the vacuum chamber, and uses Ti and N elements to react more fully. Facilitate the deposition of high stoichiometric ratio TiN film.

3) During the entire deposition process, the vacuum chamber is maintained at room temperature to 100°C, which is a low-temperature environment, and TiN thin films are deposited without damaging substrates such as high-speed steel, which increases the types of workpiece materials to be plated. It is beneficial to the application of titanium nitride in many fields. Description of drawings

Fig. 1 Schematic diagram of the new plasma-assisted magnetron sputtering structure; 1. Revolving disk, 2. Twin target, 3. Revolving disk axis, 4. Workpiece disk rotation axis, 5. Workpiece frame, 6. RF plasma generation source;

Fig. 2 transmittance curves of films prepared under different plasma powers;

Fig. 3 Microstructure of films prepared under different plasma powers.

Detailed ways

use equipment:

The thin film deposition device is ACSP70/73 multifunctional ion coating tester. The experimental equipment includes: a Taikeyi mechanical pump and a molecular pump from Osaka Vacuum, Japan to form a vacuum system; there is a revolution disc in the vacuum chamber, and there are several gear chain belts on the disc, and the rotation ratio is 1. :20, the height of each workpiece rack is about 510mm; there are several heating tubes in the vacuum chamber to make the vacuum chamber heated evenly, and to ensure that the temperature error between the vacuum chamber and the substrate is <0.5°C; a 10KW pulsed DC power supply and a 10KW bipolar Pulse bias power supply, the frequency of sputtering power supply is 40kHz, the two targets are alternately used as cathode and anode during the sputtering process, target sputtering occurs in the negative half cycle, and the accumulated charge on the target surface is neutralized in the positive half cycle, effectively The phenomenon of target poisoning and anode disappearance is effectively prevented; the magnetron sputtering cathode area used as a plasma generation source is still 563mm (length) × 106mm (width), and the surface target is made of alumina ceramics produced by Beijing Institute of Nonferrous Metals The target adopts the RSG3500 RF power supply and PSG-IVA RF automatic matching device of Changzhou Ruisijieer Electronic Technology Co., Ltd., and the maximum power of the RF power supply is 3.5kw;

Schematic diagram of the new plasma-assisted magnetron sputtering structure 1; 1. Revolving disk, 2. Twin target, 3. Revolving disk axis, 4. Workpiece disk rotation axis, 5. Workpiece holder, 6. RF plasma source;

The entire vacuum chamber is a cylindrical structure.

The revolution disk is composed of upper and lower disks and several support rods. The revolution axis passes through the center of the upper and lower disks, and the revolution disk rotates at a constant speed around the revolution axis. The revolution speed is adjustable within the range of 5-30r/min. The rotation direction of the revolving disk is set according to the relative position of the plasma source and the sputtering target.

The twin target power supply adopts pulsed DC power supply, the twin target shape is rectangular or cylindrical, the twin target magnetic field adopts an unbalanced magnetic field, and the back of the target adopts a circulating water cooling structure. The twin target materials are both Ti. During the sputtering process, the two targets are alternately used as cathode and anode. Target sputtering occurs in the negative half cycle, and the accumulated charge on the target surface is neutralized in the positive half cycle.

The workpiece holders are cylindrical or cylindrical, and the workpiece holders are evenly distributed on the circumference of the revolution axis, and it is ensured that the substrate-target base distances on all the workpiece holders are the same. According to the process requirements, the number of workpiece racks can be as many as the space allows, and the diameter of the workpiece racks and the target base distance can also be adjusted according to the process.

The motor and the revolving disk are driven by a backing plate, and there is a gear transmission between the workpiece holder and the revolving disk, the motor drives the revolving disk, and the revolving disk drives the workpiece holder to rotate. The rotation speed of the workpiece frame is determined by the revolution speed and the speed ratio between them. The ratio of revolution and rotation is 1:20.

The plasma generation source adopts the radio frequency power supply and the radio frequency automatic matching device to be used together. Through the radio frequency automatic matching device, the reflected power can be controlled to 0w; Balanced magnetic field magnetron sputtering target), unbalanced magnetic field magnetron sputtering target material needs to use difficult sputtering target materials, such as alumina, titanium oxide and other materials, and the power of the radio frequency power supply is controlled within the range of 1000W to ensure that the target is free of sputtering. any sputtering.

The twin target and the plasma source are fixed on the wall of the vacuum chamber, the distance between them is less than 1/2 of the circumference of the vacuum chamber, and the positions of the two are interchangeable, which is directly related to the rotation direction of the revolution disk. The front surface of the twin target is equipped with a pneumatic baffle. Before each coating, only the working gas is introduced to clean the target surface until the metal oxide on the target surface is sputtered off, and pure metal can be sputtered, and then the reaction gas is introduced. After the sputtering process and the rotation speed of the orbiting disk are stable, the baffle is opened to deposit the film.

It should be noted that either the unbalanced magnetic field twin target or the unbalanced magnetic field single target can be used as the Ti target.

Specific process parameters:

Ion source power 0~3.5kw adjustment; Ti target current: 1~15A adjustment; base bias voltage: -80~-200V; target base distance: 120mm; argon flow: 200~300sccm; nitrogen flow: 12~30sccm; Bottom vacuum: 5×10 ^-3 Pa to 5×10 ^-4 Pa; working pressure: 0.1～1Pa adjustment.

Example 1:

Put the 40×40×5mm steel sheet and φ20 silicon sheet into the vacuum chamber of the equipment after cleaning and drying, vacuumize to <3Pa, open the high valve and heating pipe, wait for the temperature to stabilize at 100°C, and vacuum to 5 ×10 ^-3 Pa, filled with argon gas, using a mass flow meter to control the argon gas intake flow rate to keep it stable at 0.5 Pa, turn on the revolution disk, the speed is stable at 5r/min, without ion source assistance, the Ti target power supply current is up to 9A , to make Ti glow, gradually increase the negative bias -80V. Nitrogen is introduced, and the mass flow meter controls the nitrogen intake flow rate to 18 sccm. Open the baffle, start timing, and prepare TiN hard films with different thicknesses by controlling the deposition time.

The prepared film was tested for transmittance by using a Lambda950 UV-Vis-NIR spectrophotometer from PE Company in the United States. The test results are shown in the curve a in Figure 2. The reflectivity of TiO film is low. The microscopic morphology of the prepared film was tested by atomic force microscope. The test results are shown in Figure 3(a). The test results show that the surface of the titanium nitride film is rough, the particle size is different, and the shape is irregular.

Example 2:

Put the 40×40×5mm steel sheet and the φ20 silicon sheet into the vacuum chamber of the equipment after cleaning and drying, vacuumize to <3Pa, open the high valve and heating pipe, wait for the temperature to stabilize at 100°C, and vacuum to 5 ×10-3Pa, fill with argon, use a mass flow meter to control the argon gas intake flow rate to keep it stable at 0.5Pa, turn on the revolution disk, and keep the speed at 5r/min, gradually increase the ion source power to 500W, Ti target power supply current To 9A, make Ti glow, and gradually increase the negative bias -80V. Nitrogen is introduced, and the mass flow meter controls the nitrogen intake flow rate to 18 sccm. Open the baffle, start timing, and prepare TiN hard films with different thicknesses by controlling the deposition time.

A photometer was used to test the transmittance of the prepared film, and the test results are shown in the curve b in Figure 2. It can be seen from the figure that the reflectance of the titanium nitride film becomes higher after plasma assistance is applied. The microscopic morphology of the prepared film was tested using an atomic force microscope. The test results are shown in Figure 3(b). The test results show that as the power of the plasma source increases, the crystallinity, compactness and hardness of the film are improved. The surface roughness is small, the film and the substrate have a high bonding force, and it is difficult to produce local shedding.

The invention introduces a plasma region in the vacuum chamber by improving the traditional magnetron sputtering technology, adopts intermediate frequency pulse direct current or direct current sputtering to sputter the Ti metal target, and controls the working gas pressure, temperature, time, sputtering power, etc. Process conditions, deposit TiN film on the substrate. The method can produce a TiN thin film with good performance in low temperature environment, the crystallinity, compactness and hardness of the thin film are improved, the surface roughness is small, the thin film and the substrate have high binding force, and it is difficult to produce local shedding. The invention can provide samples for the experimental research or industrial production of the hard film.

Claims (8)

1. A method for preparing TiN thin films by magnetron sputtering at low temperature; the substrate material is made of conductor or semiconductor materials such as white steel, copper, and single crystal silicon; the deposition equipment adopts magnetron sputtering coating equipment, using twin target sputtering, sputtering During the process, the two targets are alternately used as cathode and anode; An auxiliary unbalanced magnetic field magnetron sputtering cathode is separately installed in the film deposition vacuum chamber of the deposition equipment. The target surface of the unbalanced magnetic field magnetron sputtering cathode is set opposite to the deposition surface of the workpiece. The unbalanced magnetic field magnetron sputtering cathode passes through The wire is connected to the RF power supply through the RF automatic matching device; During the film deposition process, the non-equilibrium magnetic field magnetron sputtering cathode is used as a plasma source to provide a plasma area between the target surface and the coating surface of the workpiece, and the film deposited on the workpiece quickly enters the plasma reaction area. In the zone, the incompletely reacted non-stoichiometric TiN film decomposes into N atoms and Ti atoms react with the N- generated by the ionization of _N2 to obtain a high-stoichiometric high-purity compound film; at the same time in the reaction zone Under the bombardment of the plasma, the prepared film becomes dense and smooth, and the bonding force between the film and the workpiece is stronger. 2. The method according to claim 1, the sputtering power source used for preparing the TiN thin film by magnetron sputtering at low temperature is an intermediate frequency power source or a pulsed DC power source. 3. The method according to claim 1 or 2, what is used for preparing the TiN thin film by magnetron sputtering at low temperature is an unbalanced magnetic field twin target or an unbalanced magnetic field single target. 4. The method according to claim 1 or 2, the low temperature condition for preparing the TiN thin film can be from room temperature to 100°C. 5. The method according to claim 1 or 2, wherein the ion source used for preparing the TiN thin film by magnetron sputtering at low temperature is an anode layer linear ion source, a radio frequency ion source, a Hall ion source or a Kaufmann ion source. 6. The method according to claim 1 or 2, after the workpiece periodically rotates through the sputtering target, it enters the plasma region generated by the ion source, and is further nitrided to increase the stoichiometric ratio of the TiN film. 7. The method as claimed in claim 1 or 2, the non-equilibrium magnetic field magnetron sputtering target material needs to use a difficult sputtering target material, no matter what kind of material is used, the power of the radio frequency power supply must be controlled within a certain range to ensure that the During the film deposition process, no material is sputtered out of the target used as the plasma generation source to avoid contamination of the film, that is, the maximum power applied to the target by the RF power supply is less than the minimum power sputtered by the target; For materials such as alumina or titanium oxide, the power of the RF power supply is controlled within the range of 100-1000W to ensure that the target is free from any sputtering. 8. The method according to claim 1 or 2, introducing a plasma region in the vacuum chamber, using intermediate frequency power supply or pulsed DC power supply to sputter the Ti metal target, and controlling the pressure of the working gas (argon) at 0.1Pa-3Pa; The pressure ratio of the reaction gas (nitrogen) to the working gas (argon) is 1:5-50; the temperature is at room temperature -200°C; the sputtering power supply current is at 1A-30A, and the TiN film is deposited on the substrate.