Atomic Layer Deposition (ALD)


Sample preparation

Silicon

ALD proceeds from the Si-OH bonds on the silicon surface. OH bonds are natively present in the silicon native oxide, and thus a clean sample should react without further preparation.

A silicon sample may be prepared with a highly activated surface with a piranha clean (Thian 2016), or a plasma step in the Fiji itself. For a piranha cleaned surface, it is recommended to do a 5-10 minute piranha step, remove the oxide in BOE (~8 s), then do an additional 5-10 minute piranha step. Note that piranha will increase roughness of the surface. Any freshly HF/BOE dipped silicon sample will require either time for the native oxide to regrow, or a plasma conditioning step before growth can take place. The Si-H terminated surface after an HF/BOE dip will not react with the ALD precursors (Thian 2016).