Before silicon wafers are placed in a diffusion furnace, they should be cleaned first to remove impurities and particles from their surfaces. This is known as “pre-diffusion cleaning.”
Pre-diffusion cleaning can be done using various methods:
- RCA wafer cleaning process – It consists of two steps:
- Standard cleaning 1 (SC1) – The silicon wafers are cleaned with a solution containing ammonium hydroxide and hydrogen peroxide, which helps in removing organic particles. However, the metallic ions are still present in the wafers’ surfaces.
- Standard cleaning 2 (SC2) – After undergoing the SC1, the silicon wafers are cleaned in a bath containing hydrochloric acid and hydrogen peroxide. This solution removes leftover metallic traces from the wafers’ surfaces.
- Piranha etch clean – This method uses a solution of sulfuric acid and hydrogen peroxide, which dissolves larger and more stubborn amounts of organic residue from the wafers.
- Megasonic cleaning – Uses cavitation bubbles produced by megasonic waves in a bath to remove impurities from the wafers. Unlike other methods, megasonic cleaning doesn’t use harsh chemical baths.
- Ozone cleaning – Uses deionized (DI) water to rinse the inorganic contaminants away from the wafers. Then the wafers are placed inside the ozone chamber. The ozone’s powerful oxidizing action converts the organic particles to carbon, leaving the wafers clean and free from impurities.
Wafers that are not thoroughly cleaned may affect subsequent diffusion steps and negatively impacts the final product. That’s why pre-diffusion cleaning is important. Modutek offers a complete line of chemical baths and wet processing equipment that supports the wafer cleaning processes mentioned above. These are designed to provide effective cleaning that will leave silicon wafers particle-free and ready for diffusion.
Contact Modutek by email Modutek@modutek.com to learn more or read the complete article titled “Why Pre-Diffusion Cleans Are Critical in Wafer Cleaning Processing.”