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Coating equipment principle and process

Addtime:2016/11/24 15:24:07  Views:397


一、Principle of coating equipment


1、Magnetron sputtering:

Magnetron sputtering system at the cathode material is placed behind the 100 ~ 1000 gauss powerful magnets, filling the 011 ~ 10 pa pressure in vacuum chamber of inert gas (Ar), as the carrier of gas discharge. In high pressure under the action of Ar atomic ionization as Ar + ions and electrons, and electronics in the process of acceleration to fly to the substrate, is affected by the magnetic field perpendicular to the electric field, make the electronic produces deflection, bound in the areas near the target surface plasma electrons along the target surface in the form of cycloid, constantly in the process of movement and Ar atoms collide, ionization out lots of Ar + ion, electron energy reduce gradually, after many collision cast off the yoke of the magnetic field lines, eventually fell on the substrate, vacuum interior wall and target source anode. And Ar + ion in the role of high voltage electric field acceleration, and the impact of target material and release energy, cause the target material ?

Simple say: vacuum sputtering chamber first by high vacuum pump to a certain pressure, after through constant pressure instrument or mass flowmeter to splash plating indoor inert gas such as argon to a constant pressure (such as 2 x 10-1 pa pa) or 5 x 10-1 after places must be on the magnetron cathode target power or intermediate frequency power supply, dc power supply in the positive and negative electrodes under the action of high pressure, target ahead between anode and cathode gas atoms are a large number of ionization, glow discharge, ionization process makes the argon atomic ionization of Ar + ion and can independence movement of electrons,Under the action of high pressure electric field, electrons flying to the anode, and positively charged Ar + ion is high speed to fly to target material as a cathode, and with the impact of target material releases its energy in the process, obtain a high-energy target atoms from the constraints of the target material and fly to the substrate, so the target particle deposition film is formed on the substrate opposite the target.
Sputtering yield change simple schematic diagram, with the energy of incident ion sputtering curve for short. Can be seen from the diagram sputtering yield changes with the energy of incident ion has the following characteristics: there is a sputtering threshold, the threshold energy for 20 ~ 100 eV. When the energy of the incident ion is less than the threshold, no atoms are sputtering. Usually when the energy of the incident ion for 1 ~ 10 keV, sputtering yield can reach a maximum value. When the energy of the incident ion more than 10 keV, sputtering yield began to decline with the increase of the energy of the incident ions.

 

2、The main way of sputtering:

Reactive sputtering is in sputtering of inert gas atmosphere, a percentage of the reaction gas is piped in, often used as a reaction gas mainly by oxygen and nitrogen.

直流溅射(DC Magnetron Sputtering)、射频溅射(RF Magnetron Sputtering)、脉冲溅射(PulsedMagnetro n Sp uttering)和中频溅射(Medium Fre2quency Magnetro n Sp uttering)

Dc sputtering method is used for sputtering materials for sputtering of conductive materials and reaction sputtering deposition, its simple processing equipment, has a high sputtering rate.

Intermediate frequency ac magnetron sputtering in a single cathode target system, and the release of the pulsed magnetron sputtering have the same charge, prevent the bowl. Intermediate frequency ac sputtering target (Twin2Mag) technology is applied to the twin sputtering system, the intermediate frequency ac twin sputtering targets are the two output end of the intermediate frequency ac power, respectively, received a non-equilibrium sputtering target of double closed magnetic field respectively on the cathode, and thus on the dual target respectively opposite phase ac voltage, a pair of magnetron sputtering target is alternately as cathode and anode. Twin magnetron sputtering target sputtering technology, greatly improving the stability of, can avoid to be poison of target surface charge accumulation, cause target surface arc ignition and loss of anode, high sputtering rate, lay a foundation for compound film industrialized mass production.

Magnetron sputtering of continuous production line In general can be divided into three parts: pretreatment, sputtering deposition, post-processing.

2. 1 Before the treatment (cleaning process)

To get a solid, dense, no pinhole defect layer, must make the film deposition in clean, has a certain temperature, and even activate the substrate. For the after treatment process including mechanical cleaning (grinding, brush wash, deionized water flushing, hot and cold wind blowing net), baking, glow plasma bombardment, and so on. Mechanical cleaning purpose is to remove the dust on the surface of the substrate and the possible traces of grease and other foreign bodies, and do not contain reactive ion, also can use ultrasonic cleaning when necessary. Baking is the purpose of the residual moisture, thoroughly remove substrate surface and substrate heated to a certain temperature, a lot of material at a higher substrate temperature can increase the density of binding force and membrane layer.Substrate can bake in a vacuum for outdoor, also can be in the vacuum room to continue, to have a better effect. But in the vacuum chamber as heat source of the power supply should be low voltage, otherwise easy to cause discharge. Glow plasma bombardment cleaning can further remove the substrate surface residual bad for film deposition ingredients, can improve the activity of substrate surface atoms at the same time, more conducive to the combination of substrate and deposition of solid material atoms. The use of intermediate frequency power supply will be more obvious effect than dc discharge.

 

2. 2 Sputtering coating

This part should be the main body of the production line, and is in the vacuum state of a system, is made of stainless steel or carbon steel to make a separate room body connection. The two ends of the glass substrate are in a special state, and the vacuum lock chamber is in a special state, in order to repeatedly make the cleaned glass substrate to enter and allow the plating to be made. The two ends of each lock chamber are provided with a valve and a vacuum unit with a strong pumping capacity can be easily converted to the vacuum and atmosphere. The vacuum chamber which is connected with the vacuum lock chamber is called the transition chamber. Its function is to stay by the lock chamber of the substrate to be plated, or to allow the deposition of a good substrate to stay here, waiting for the output lock room, play the role of the deployment of the substrate. The transition room should also be equipped with vacuum unit, and to maintain a high degree of vacuum. The input end of the transition room can be set up glow discharge plasma cleaning device. However, it should be considered that the isolation of the chamber body adjacent to the base plate, which is mainly to maintain the different pressure of the adjacent chambers. The pressure of glow discharge is generally higher, and the working pressure of the sputtering coating is often in the lower order of magnitude. The part between the front and rear chamber is called a coating chamber or a sputtering chamber. Each coating chamber is an independent sedimentary area. The so-called independent refers to the working pressure of the coating chamber and the working atmosphere is not affected by other rooms. Each sputtering chamber is provided with one or two target. Each target can be provided with a magnetron sputtering target, or cathode. The number of sputtering chamber or sputtering target, including the selection of the target depends on the development of film production line and production capacity. The power density of magnetron sputtering target is cm 13W/ 2, which is much higher than that of DC sputtering. But the actual power is often difficult to ensure that the target power. No large power is not high deposition rate, and high deposition rate is highly respected in the modern coating. Power supply in parallel is a way to enhance power. The structure of planar magnetron target is divided into direct cooling and indirect cooling two. Direct cooling type suitable for the target of good air tightness. Because the cooling effect is good, the power is bigger. The target of indirect for poor air tightness, smaller power. Target magnets currently used is more NdFeB permanent magnet, as long as the magnetic field is uniform, and a gas distributing device in gas by reasonable way, in the target surface area, practice can obtain sputter etching uniformity. This is an important guarantee for the transverse uniformity of the film. Taking into account the edge effect produced by both ends of the target, the two ends of the substrate are also obtained with the same film thickness as the middle part. The background of high vacuum is a necessary condition for sputtering deposition, so a high vacuum unit is set up in the sputtering chamber. At present, most of the diffusion pump units are used. Imported equipment, the configuration of the turbo molecular pump, but the maintenance of trouble, the replacement of the bearings need to be carried out by the manufacturer; the configuration of the diffusion pump is also coupled with liquid nitrogen cold trap, so that there is a better oil blocking effect, but the maintenance cost is high. The pump can be used in the feeding chamber to prevent the pollution of oil vapor on the substrate, and can prevent the active gas from mixing in the coating chamber. The necessity to restrain the pollution of oil vapor in the sputtering system should be the undisputed. In order to ensure that each sputtering chamber can work in an atmosphere of independence, the atmosphere isolation measures should be taken between the adjacent sputtering chamber. This can be achieved by means of a slit to isolate the object. The so-called slit is the length of 200 ~, which is two ~ 300mm, which is in the transverse chamber of the chamber, which is 10 ~ 12mm, which is a kind of flow guiding model, which has a very small transmission probability in the molecular state. The cross section of the chamber body at the position of the slit is completely separated from the slit. So the two slits are separated from 40 to 50 cm sets to form a physical separation. Two the two ends of the space of the slit are provided with a high vacuum unit, which enables the isolation effect to be better and the control is less than 1%. The advantage of this structure lies in the separation of the atmosphere and the transmission of glass can be considered at the same time. Should not achieve effective isolation, when the adjacent sedimentary area of the atmosphere is not at the same time, the impact of each other will seriously undermine the uniformity of the film, and even the structure, which is not allowed.

 

2. 3 post-processing

After the plating process, the substrate is transported from the vacuum chamber to the atmosphere. The cleaning requirements are not as strict as before. The purpose is to expose the defects of the film layer more easily, so as to be found in the subsequent detection. The most simple visual detection is, in order to observe the distribution of the bottom substrate, a light source, can be found and the number of pinholes, there is no trace of discharge. The transmission rate of the outlet end can be pointed out that the final transmission rate of the film layer can be pointed out. Multi channel probe can be arranged in the range of the substrate, and the collected data are processed by the computer to evaluate the longitudinal and transverse uniformity of the film and the abnormality. For special purposes after the optical film outlet that enters the purification room, covered with a layer of protective tape after the storage of plastic film.

 

二、Technological process:

2.1 SITO structure coated with OC protective layer: (Huang Guangqu)
2.2 SITO structure coated SiO2 protective layer:
2.3 sputtering process:
2.4 film thickness process requirements:
The thickness of Nb2O5: (150 - 250) - A (single)
SiO2: (150 - 500) - A (double plating thickness at the same time, the same)
ITO: a 250--850 thickness (the thickness of 700 to 800 a, resistance 25 Ohm /sq; the thickness of 250 to 350 a, 75 (/sq) and double plating, same thickness)
Mo/Al/Mo: general use (500-750) / (2000-3000) / a (500-750), <0.4 /sq (double resistance ohm graded plating thickness equivalent)
2.5 coating equipment structure:
ITO: the upper and lower chip transfer mechanism, the preparation room (import buffer), transfer room, coating room, isolation room