The engineering of intrinsic point defects in silicon wafers and crystals

Abstract

Using new techniques which manage intrinsic point defect concentrations during the growth of silicon crystals and subsequent processing of silicon wafers, it is possible to achieve two highly desirable results. First, using techniques which maintain crystals sufficiently close to equilibrium during growth such that it is possible to grow large diameter CZ silicon crystals which are completely free of agglomerates of vacancies (voids) or self interstitials (dislocation loops). Secondly, through the control of quenched-in vacancy concentration profiles in thin silicon wafers during rapid thermal annealing processes, it is possible to obtain ideal oxygen precipitation behavior in silicon wafers. Such vacancy concentration engineered wafers are effectively programmed to produce robust defect distributions suitable for internal gettering (IG) applications. The performance of such wafers is independent of all parameters previously important to engineering of IG structures: oxygen concentration, crystal growth method and even the application in which the wafer is used. These two new types of material represent important simplifications to the successful defect engineering of silicon wafers in advanced IC applications. It is shown that, taken together, results from both crystal growth and wafer processing studies place a large number of constraints on the parameter set used to describe the properties of the vacancies and self interstitials in silicon. A model for the oxygen precipitation enhancement in the MDZ process is given.