Microstructural defects in laser recrystallized, graphite strip heater recrystallized and buried oxide silicon-on-insulator systems: A status report

Abstract

Laser recrystallized silicon-on-oxide, graphite strip heater recrystallized silicon-on-oxide and buried oxide by high dose oxygen ion implantation are three of the silicon-on-insulator technologies that are currently being evaluated for VLSI and VHSIC applications. This status report compares the microstructure of these materials. The main defects in both the laser and graphite strip heater recrystallized material are subgrain boundaries. The misorientations across the boundaries are normally less than one degree. The boundaries are formed by dislocation coalescence. The dislocations are generated by the stresses caused by the volume expansion during solidification of silicon droplets trapped in the solid silicon matrix. The droplets are caused by constitutional supercooling. Buried oxide SOI formed by high dose oxygen ion implantation has fewer crystallographic defects than the other two materials. The entire ion implanted area is a single crystal after high temperature annealing. The primary defects in epitaxial layers grown on implanted substrates are dislocations. The oxide/silicon interfaces are abrupt if the dose is large enough. The sharp interfaces are formed by an internal oxidation mechanism. The minimum MeV He ion channeling yield from epitaxial silicon layers grown on buried oxide is about 2.5%, the lowest of any SOI material.