Extrinsic Gettering of Silicon Wafers
Below is a list of gettering techniques used to remove defects.
- Intrinsic Gettering - Czochralski grown silicon wafers have large amounts of contaminating dissolved oxygen.
- Halogenic Dopant Sources - Used during diffusion it converts metallic impurities into volatile halides. Halides must be carefully used so as to not pit the semiconductor surface.
- Halogenic Oxydation - is an effective process preventing oxygen-induced staking faults on the silicon. This process works so well that is' often used in MOS circuit fabrication.
- Mechanical Damage - using abrasives including sand blasting and ion implantation creates a damaged layer on the silicon wafer's backside. This damaged region works as a sink to remove metallac impurties and stacking faults.
- Glassy Layers - borosilicate (BSG) and phosphosilicate (PSG) glass when contacting heated silicon are very good at removing a silicon wafer's deep impurities.
- Chemical Cleaning - is considered one of the more powerful ways to reduce process contamination. The RCA Clean Process are used for this purpose.