Thermal evaporation
Thermal evaporation is a straightforward means of thin film deposition with materials being heated to evaporation temperatures via a resistively heated support.
Thermal evaporation is a widely used technique for depositing thin films and coatings. This process involves heating a material to its evaporation point in a high vacuum chamber, allowing the vapourised atoms to travel and condense on a cooler substrate, forming a thin film.
How Thermal Evaporation Works
The material to be deposited (source material) is heated until it vapourises. This is typically achieved using resistive heating or electron beam heating.
The vapourised atoms travel through the vacuum chamber and condense onto the substrate, forming a thin, uniform film. In thermal evaporation it is important to use a high vacuum to reduce contamination and ensure a mean free path long enough for atoms to travel directly to the substrate. This typically means that evaporation chambers are taller than an equivalent magnetron sputtering system.
Depending on the material, resistive heating (using a heated filament or boat), electron beam heating, or induction heating is used to vapourise the source material.
Common thermally evaporated materials include metals (e.g., gold, aluminium), alloys, and compounds. Substrates must be clean and free from contaminants to ensure good adhesion and uniformity. Some processes require heating the substrate to improve film quality and adhesion.
Operation Considerations
- Temperature: Must be carefully controlled to ensure proper evaporation without decomposition of the source material.
- Deposition Rate: Controlled by adjusting the heating power, affecting film thickness and uniformity.
- Vacuum Level: High vacuum levels are essential to reduce contamination and ensure a direct path for vapour atoms.

