Environmentally friendly single-wafer spin cleaning using ultra-diluted HF/nitrogen jet spray without causing structural damage and material loss

We have developed an ultra-diluted HF/nitrogen jet spray cleaning procedure for single-wafer spin cleaning, which can efficiently remove particulate and metallic contaminants in a short period of time from both silicon and silicon-dioxide surfaces without causing damage to fragile 45nm polysilicon gate structures. The use of a very low HF concentration makes the silicon and oxide losses negligible. This very simple single-step cleaning procedure drastically reduces the chemical and water comumption as well as electrical energy per wafer due to the short spraying time with the ultra-diluted HF at room temperature. HF wastewater, the only effluent of this cleaning, is recycled by forming CaF₂, which can be a raw material for HF or Portland cement, so this cleaning meets the requirements with respect to the environmental control.