PAD-Fume

The PAD-Fume is a modular part of the Wafer Surface Preparation System (WSPS) for ultra-trace metal contamination analysis of silicon wafer surfaces and oxides.

It can be used in combination with the automatic droplet scanner PAD-Scan and the PAD-Dry (for TXRF analysis only).

HF - Bottle

PAD - Fume Nozzle

HF vapor is generated in a fumer unit and fed into the reaction chamber via jet inlets. The HF vapor condenses on the cooled wafer dissolving the surface oxide (native or thermal) according to the chemical reaction:

6 HF + SiO₂ → H₂SiF₆ ↑ + 2 H₂O (residue)

The residual wafer contains the impurities from the outer surface, the oxide and the silicon/oxide interface. After the etching process, the chamber is purged by nitrogen to remove the HF vapor, before the chamber hood is opened. For VPD residue collection the wafer is subsequently processed with the PAD-Scan (Programmable Automatic Droplet Scanner).