PURPOSE: The wafer is cleaned in chemical baths in order to remove unwanted impurities.

WHERE:  At the wet bench:

CLEANING AGENTS: There are three steps; each one addresses a separate type of contaminant:

• SC1 (ammonia - NH₄OH, hydrogen peroxide - H₂O₂ and deionised -DI water) removes organic contaminants and particles.
• Cleaning mechanism: (see animation below)
• the wafer is introduced in oxidant ambient H₂O₂
• it is oxidized by molecules, forming a thin layer of SiO₂ at the surface
• when the SiO₂ layer is removed by etching, the particle will be also removed, leaving a clean surface

• another cleaning mechanism may take place by ionizing the surface with the ions from the solution, the particle is then pushed away from the surface by repulsive forces.
• SC2 (H₂O, H₂O₂ and HCl) removes metal contaminants.
• Hydrofluoric acid - HF removes native and chemical oxides.

At the end, the wafer is rinsed in DI water and dried by spinning (the spinner can be observed at the bottom of the picture - the round holder).