Gas-phase processing of the silicon surface toward controlled coverage with selected species

As the level of contamination introduced to the surface is reduced through the use of cleaner chemicals and processes, the emphasis of cleaning is shifting from one of removing incidental contaminants to that of controlling the condition of the surface inherently produced by the preceding process and bridging the condition of the surface left by the preceding process steps with the requirements for the surface condition prior to the next process. Gas-phase processes, which can be integrated into vacuum based equipment, have generated interest because of the greater degree of process control which can be used to condition the surface. In this study, the differences between silicon surfaces produced through the AHF:methanol and dilute HF oxide etch processes were explored through X-ray Photoelectron Spectroscopy (XPS), metal-silicon contact characteristics, and MOS characterization. The presence of fluorine on the surface following the AHF:methanol process was the most significant difference between these surfaces. Reduced stress at the Si/SiO{dollar}sb2{dollar} interface, retardation of thermal oxidation, and improved gate oxide integrity were observed on the AHF:methanol surface.; A contactless surface photovoltage technique was used to monitor the surface evolution following gas-cleaning sequences, and the differences in surface activity were related to the chemical composition of the surface through XPS. The UV/Cl{dollar}sb2{dollar} process, which is used to remove metallic contamination from the surface in the gas phase, also removed most of the fluorine from the surface after the AHF:methanol. The post-UV/Cl{dollar}sb2{dollar} surface yielded oxides with improved gate oxide integrity, indicating that the level of fluorine remaining on the surface following the AHF:methanol etch process is not optimal for growth of thin oxides. Stable oxygen passivated surfaces were obtained through a methanol adsorption + UV/O{dollar}sb2{dollar} process, which removed chlorine from the surface without introducing Si-OH. MOS characterization showed an improvement in the charge-to breakdown statistics of oxides grown on these surfaces.; Overall, the results obtained indicate that gas-phase cleaning processes offer a potentially greater degree of control of the condition of the surface over aqueous processes and may find useful application in areas where requirements for surface conditioning are not met by liquid-phase chemistries.