The influence of vapor phase cleaning on the composition and the surface roughness of rapid thermal oxides and nitrided oxides

In this paper, the influence of various pre-oxidation cleanings on the Si/S iO2 interface and the oxide surface roughness is investigated. Different ty pes of Vapor Phase Cleanings (VPC) are performed in an integrated STEAG AST cluster module and are compared to a standard wet cleaning process. The VP C uses Anhydrous Hydrogen Fluoride (AHF) and additional ozone cleaning. Dir ectly after the cleaning, oxidation in pure oxygen (O-2) is carried out in an integrated STEAG AST Rapid Thermal Processing (RTP) cluster module. Nitr ided oxides are formed by annealing in pure nitric oxide (NO) gas directly after the oxidation. The nitrogen incorporation and distribution in the oxi de is investigated using secondary ion mass spectroscopy (SIMS). The nitrog en concentration at the Si/SiO2 interface depends on the time and/or temper ature of the NO annealing. For a 900 degrees C annealing, the nitrogen inco rporation varies from 0.5 at.% for a 5 s anneal to 2.5 at.% for a 60 s anne al. The nitrogen concentration of the oxides can be correlated with the dif ferent types of precleaning sequences which seems to be an effect of the di fferent fluorine contents obtained after various cleaning procedures. The s urface roughness of oxide layers formed after different pre-cleaning sequen ces is analyzed by Atomic Force Microscopy (AFM). A decrease in surface rou ghness is measured for oxidation performed at higher temperature and for ra pid thermal oxides produced after a cleaning procedure using AHF and ozone.