How to control and optimize vacuum coating parameters to achieve better results

1、Parameter Control and Optimization of Evaporative Coating

Temperature control of evaporation source

The temperature of the evaporation source is a key parameter.For different coating materials,there are specific evaporation temperature ranges.If aluminum metal is evaporated,the temperature is generally between 1200-1400℃.By using temperature sensors and feedback control systems,such as thermocouples combined with PID controllers,temperature can be controlled.Excessive temperature may cause the material to evaporate excessively,resulting in a rapid growth rate of the film layer and the formation of rough thin films;If the temperature is too low,the material will not evaporate enough,which will affect the coating efficiency.

The method of optimizing temperature includes conducting pre experiments based on material characteristics to determine the evaporation temperature,and monitoring and adjusting it in real-time during the coating process.For example,in the preparation of optical thin films,the evaporation temperature is fine tuned according to the optical properties such as refractive index of the desired film to make the film structure more uniform.

A high vacuum environment is beneficial for reducing collisions between evaporated atoms and residual gas molecules.Generally,the vacuum degree should reach 10⁻³-10⁻⁵Pa.Maintain the required vacuum level through a combination of vacuum pump systems,such as mechanical pumps and molecular pumps.

Optimizing the vacuum degree can fully evacuate and bake the vacuum chamber before coating.During the coating process,monitor changes in vacuum level and promptly address issues such as vacuum system leaks.A good vacuum degree can cause evaporated atoms to fly straight towards the substrate,improving the uniformity and purity of the film.

Vacuum coating

2、Parameter Control and Optimization of Sputtering Coating

Sputtering power adjustment

The sputtering power determines the energy of argon ion bombardment on the target material.Excessive power may result in excessive energy of sputtered atoms,causing damage to the substrate and increasing internal stress in the film,leading to film detachment.If the power is too low,the splash rate will be too slow.By adjusting the power supply,such as adjusting the output voltage and current of the DC power supply during DC sputtering,the sputtering power can be controlled.

For different target substrate combinations,it is necessary to determine the appropriate sputtering power through experiments.For example,when sputtering ceramic targets,due to their high chemical bond energy,a relatively high sputtering power is required,but at the same time,attention should be paid to preventing the substrate from overheating.

Target substrate distance setting

The appropriate target substrate distance helps ensure that sputtered atoms are uniformly deposited on the substrate.The general distance is between 3-10cm.The distance is too close,and the incident angle distribution of sputtered atoms on the substrate surface is uneven,resulting in uneven film thickness;The distance is too far,and the energy loss of sputtered atoms during flight is too high,which reduces the deposition rate of the thin film.

When optimizing,factors such as target size and sputtering power can be comprehensively considered.During the coating process,the uniformity of the film on the substrate can be further improved by rotating the substrate and other methods.