Prevention of Microroughness Generation on the Silicon Wafer Surface in Buffered Hydrogen Fluoride by a Surfactant Addition

Abstract

In order to prevent microroughness generation on the Si wafer surface in buffered hydrogen fluoride (BHF), the addition of a surfactant to BHF was investigated. It was found that mieroroughness generation on the Si wafer surface in BHF was prevented by adding the several 10 ppm surfactant. Also, the dissolution of Si into BHF from the Si wafer surface was suppressed by adding the surfactant. Microroughness generation was suppressed by lowering the N[-I4F concentration in BHF and the dissolution oi Si depended on the OH concentration rather than on the HF concentration in BHE For a wide range of HF and NH4F concentrations in BHF, the hydrocarbon anionic surfactant is effective for the prevention f microroughness generation. The prevention ofmicroroughness generation is explained by the adsorption f the surfactant molecules on the Si wafer surface in accordance with the Langmuir type adsorption equation. In semiconductor device fabrication processes, it is very important to clean the Si wafer surface for per formance and reliability of devices. Wet cleaning processes and etch-ing processes increasingly have been necessary in order to remove contaminants such as inorganic ions, organic mat-ter, particles, and native oxide on the Si wafer surface.