Electron beam coater is a kind of film manufacturing equipment commonly used in industry. Because of its characteristics, the evaporation coater plays a great role in film production, and the film is mainly produced by the electron beam heating in the coater.

Main structure of electron beam evaporation coating machine

Electron beam evaporation coating machine is mainly composed of control system, vacuum air path system and electron gun system.

1. Vacuum air path in electron beam evaporation coating machine

There are two pumps in the vacuum gas path, namely the front-stage mechanical pump and the high-vacuum cryopump. The cryopump mainly works at a very low temperature to achieve the purpose of vacuumizing according to the original adsorption of the cold umbrella. In the process of starting the high-vacuum cryopump, the front-stage mechanical pump will first put the pipeline in a vacuum state. When the vacuum degree of the pipeline reaches a certain degree, the Kengee valve will open, so that the front-stage mechanical pump will continue to work, so that both the pipeline and cryopump have a vacuum state, and then the front-stage valve will repeat the above steps.

2. Electron beam heating evaporation source

The evaporation source of electron beam is mainly composed of electron gun and crucible. If necessary, a set of mechanical equipment that can supply raw materials to the coating machine may be attached. In most cases, the control device for generating and controlling the electron beam and the crucible design will be integrated in the coating machine. The following are several structural methods of electron beam heating evaporation source;

① The evaporator heated by linear cathode and electrostatic aggregation method is selected.

② The evaporator heated by annular cathode and electrostatic aggregation method is selected.

③ The evaporator heated by axial gun and electrostatic remote gathering method is selected.

④ The evaporator heated by axial gun, magnetic concentration and magnetic deflection of 90 degrees is selected.

⑤E-type electron gun evaporator and E-type electron beam evaporation source emit electron trajectories similar to the word "E", so they are called E-type gun for short.

At present, the evaporation source of this method is most widely used in the vacuum evaporation coating process.

Principle and coating process of electron beam evaporation coating machine

Electron beam evaporation is used to prepare TiO2 thin films, and the fully automatic optical coating system assisted by ion beam evaporation as shown in the figure below is selected.

1. Cooling water inlet; 2. Cooling water outlet; 3. Crucible; 4. Beam coil; 5. Electron beam emitter; 6. Heating lamp; 7. Substrate holder; 8. Motor; 9. Monitoring film; 10. Ion source

The working voltage of electron gun for plating sample is 10 kV, the current is 200 A, and the stacking temperature of vacuum chamber is 145 ~ 155℃. Black granular Ti2O3 with a purity of 99.99% was selected as the film material, and CC-105 cold cathode ion beam was used for auxiliary deposition. During deposition, O2 with a purity of 99.99% was filled into the vacuum chamber as the reaction gas, and the flow rate of the reaction gas O2 was controlled by 1179A MKS mass flowmeter. The substrate was round K9 glass with a diameter of 25 mm

Before coating, the substrate was first cleaned with glass liquid, rinsed with deionized water, dried with nitrogen, then cleaned with acetone with purity of 99.9% and ethanol with ultrasonic wave for 15 min each, dried with special wiping paper, and then put into a vacuum chamber.

When the vacuum degree is pumped to 6.5×10-4Pa by mechanical pump and diffusion pump, the automatic plating program is set. When the substrate is heated to the stacking temperature of 150℃, the ion source starts to bombard the substrate, and the energy is controlled at 60 ~ 90 EV for 10 min. Then, the electronic gun is automatically started to heat and evaporate the film material, and the film is deposited at a deposition rate of 0.38 ~ 0.42 nm/s. When the film is deposited to the planned thickness of 440 nm, the program automatically closes the electronic gun and finishes the plating.

After coating, the vacuum chamber is naturally cooled to room temperature, the sample is taken out, and the spectrum of the sample TiO2 is checked by Lambda900 spectrophotometer (the inspection scale is 175～3 300 nm), and the actual thickness, extinction coefficient and refractive index of TiO2 film are calculated by Macleod software enveloping method.

Different flows of high purity oxygen were introduced into the vacuum chamber, and the effects of different vacuum degrees on the film quality, refractive index and absorption coefficient of TiO2 were studied.

When TiO2 thin films are deposited by evaporation assisted by ion source under high vacuum degree, the changes of vacuum degree with oxygen flux are listed in the following table.

The oxygen molecules filled in the vacuum chamber are ionized into oxygen ions and fully react with the vapor molecules of Ti2O3, so that the oxygen lost in the differentiation of Ti2O3 is replenished, so that the TiO2 component in the produced film is relatively pure, but if the oxygen flux is insufficient or the reaction between Ti2O3 and O2 is insufficient, the highly absorbing titanium dioxide film TinO2n-1(n=1 (n = 1,2, ..., 10) will be formed. With the increase of oxygen flux, the probability of collision between TiO2 vapor molecules and oxygen molecules in the process of evaporation increases and energy is lost, which reduces the kinetic energy of TiO2 deposited on the substrate surface and affects the adhesion and fineness of the deposited film.

As for the optical film, the kinetic energy of the film molecules on the surface of the substrate can be added with the aid of ion source, which not only has a significant influence on the refractive index of the film, but also can improve the compactness and moisture resistance of the film, and at the same time, the adhesion of the film on the substrate is also significantly improved. Electron beam coater is a kind of film manufacturing equipment commonly used in industry. Because of its characteristics, the evaporation coater plays a great role in film production, and the film is mainly produced by the electron beam heating in the coater.

Main structure of electron beam evaporation coating machine

Electron beam evaporation coating machine is mainly composed of control system, vacuum air path system and electron gun system.

1. Vacuum air path in electron beam evaporation coating machine

There are two pumps in the vacuum gas path, namely the front-stage mechanical pump and the high-vacuum cryopump. The cryopump mainly works at a very low temperature to achieve the purpose of vacuumizing according to the original adsorption of the cold umbrella. In the process of starting the high-vacuum cryopump, the front-stage mechanical pump will first put the pipeline in a vacuum state. When the vacuum degree of the pipeline reaches a certain degree, the Kengee valve will open, so that the front-stage mechanical pump will continue to work, so that both the pipeline and cryopump have a vacuum state, and then the front-stage valve will repeat the above steps.

2. Electron beam heating evaporation source

The evaporation source of electron beam is mainly composed of electron gun and crucible. If necessary, a set of mechanical equipment that can supply raw materials to the coating machine may be attached. In most cases, the control device for generating and controlling the electron beam and the crucible design will be integrated in the coating machine. The following are several structural methods of electron beam heating evaporation source;

① The evaporator heated by linear cathode and electrostatic aggregation method is selected.

② The evaporator heated by annular cathode and electrostatic aggregation method is selected.

③ The evaporator heated by axial gun and electrostatic remote gathering method is selected.

④ The evaporator heated by axial gun, magnetic concentration and magnetic deflection of 90 degrees is selected.

⑤E-type electron gun evaporator and E-type electron beam evaporation source emit electron trajectories similar to the word "E", so they are called E-type gun for short.

At present, the evaporation source of this method is most widely used in the vacuum evaporation coating process.

Principle and coating process of electron beam evaporation coating machine

Electron beam evaporation is used to prepare TiO2 thin films, and the fully automatic optical coating system assisted by ion beam evaporation as shown in the figure below is selected.

1. Cooling water inlet; 2. Cooling water outlet; 3. Crucible; 4. Beam coil; 5. Electron beam emitter; 6. Heating lamp; 7. Substrate holder; 8. Motor; 9. Monitoring film; 10. Ion source

The working voltage of electron gun for plating sample is 10 kV, the current is 200 A, and the stacking temperature of vacuum chamber is 145 ~ 155℃. Black granular Ti2O3 with a purity of 99.99% was selected as the film material, and CC-105 cold cathode ion beam was used for auxiliary deposition. During deposition, O2 with a purity of 99.99% was filled into the vacuum chamber as the reaction gas, and the flow rate of the reaction gas O2 was controlled by 1179A MKS mass flowmeter. The substrate was round K9 glass with a diameter of 25 mm

Before coating, the substrate was first cleaned with glass liquid, rinsed with deionized water, dried with nitrogen, then cleaned with acetone with purity of 99.9% and ethanol with ultrasonic wave for 15 min each, dried with special wiping paper, and then put into a vacuum chamber.

When the vacuum degree is pumped to 6.5×10-4Pa by mechanical pump and diffusion pump, the automatic plating program is set. When the substrate is heated to the stacking temperature of 150℃, the ion source starts to bombard the substrate, and the energy is controlled at 60 ~ 90 EV for 10 min. Then, the electronic gun is automatically started to heat and evaporate the film material, and the film is deposited at a deposition rate of 0.38 ~ 0.42 nm/s. When the film is deposited to the planned thickness of 440 nm, the program automatically closes the electronic gun and finishes the plating.

After coating, the vacuum chamber is naturally cooled to room temperature, the sample is taken out, and the spectrum of the sample TiO2 is checked by Lambda900 spectrophotometer (the inspection scale is 175～3 300 nm), and the actual thickness, extinction coefficient and refractive index of TiO2 film are calculated by Macleod software enveloping method.

Different flows of high purity oxygen were introduced into the vacuum chamber, and the effects of different vacuum degrees on the film quality, refractive index and absorption coefficient of TiO2 were studied.

When TiO2 thin films are deposited by evaporation assisted by ion source under high vacuum degree, the changes of vacuum degree with oxygen flux are listed in the following table.

The oxygen molecules filled in the vacuum chamber are ionized into oxygen ions and fully react with the vapor molecules of Ti2O3, so that the oxygen lost in the differentiation of Ti2O3 is replenished, so that the TiO2 component in the produced film is relatively pure, but if the oxygen flux is insufficient or the reaction between Ti2O3 and O2 is insufficient, the highly absorbing titanium dioxide film TinO2n-1(n=1 (n = 1,2, ..., 10) will be formed. With the increase of oxygen flux, the probability of collision between TiO2 vapor molecules and oxygen molecules in the process of evaporation increases and energy is lost, which reduces the kinetic energy of TiO2 deposited on the substrate surface and affects the adhesion and fineness of the deposited film.

As for the optical film, the kinetic energy of the film molecules on the surface of the substrate can be added with the aid of ion source, which not only has a significant influence on the refractive index of the film, but also can improve the compactness and moisture resistance of the film, and at the same time, the adhesion of the film on the substrate is also significantly improved.