Preoxidation Si cleaning and its impact on metal oxide semiconductor characteristics

Abstract

SiO2/Si interfaces with minimal defect densities will be required for the proper functioning of field effect transistors (FET) and device isolation schemes in future semiconductor technology. Control of the wafer surface contamination will become critical to meet semiconductor device yield and reliability goals. Future processing strategies to meet these stringent requirements include various vapor-phase preoxidation cleaning and passivating chemistries and clustered-tool processing schemes. In this paper, we summarize results from in situ studies on the prospects of the ultraviolet (UV)/O2 and HF chemical treatments as both preoxidation cleaning procedures and as passivation schemes. HF-cleaned Si surfaces were tested for passivation against hydrocarbon uptake using the surface analytical tools of x-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS), and thermal desorption spectrometry (TDS). The impact of organic contamination was studied by fabricating metal oxide semiconductor (MOS) structures on hydrocarbon-contaminated Si surfaces and measuring their electrical characteristics. The gas-phase UV/O2 procedure was studied for organic layer removal. Further, a combined HF+UV/O2 chemistry was studied to understand its effectiveness as a preoxidation treatment for preparing interface hardened MOS structures.