Wet chemical processes
Wafer cleaning is commonly the first step and may be used repeatedly throughout a process fabrication sequence. This may involve the use of acid and basic solutions, followed by a water rinse.
Cleans are designed to remove organic or metallic surface contamination as well as particulates. Furnace pre-cleans consist of a Piranha clean followed by silicon clean 1(SC1) and then silicon clean 2(SC2). Short etch steps are often done prior to metallization to ensure good contacts to semiconductors. Micro Electro-Mechanical Systems (MEMS) processes can utilize a long buffered oxide etches (BOE) for the release step.
Wet chemical etching is available with the following chemicals:
- Buffered oxide etch [BOE = ammonium flouride (NH4F) + hydrogen flouride (HF)] and HF solutions (such as 10 parts H2O + 1 part 49%HF).
- Ammonium hydroxide (NH4OH) + deionized water (diH20).
- Deionized water (diH2O) + nitric acid (HNO3) + phosphoric acid (H3PO4) + acetic acid (C2H4O2) - [Moly and aluminum (Al) etching).
- diH20 + HNO3 + hydrochloric acid (HCl) - (ITO Etching).
- PCT Megasonic clean (can be used with Detergent8 soap or without).
- Each chemical tank has a QDR rinse tank associated with it.
- Spin Rinse Dryer to dry the wafers after rinse.
- SRS Solvent Strip chemistry.
Equipment and hoods
- One acid hood.
- One solvent hood.
- Other chemistries can be used. Please check with FEDC staff.
- Wafer cleaning