Influence of Hydrogen On The Solid Phase Epitaxial Regrowth of Strained Layer Silicon Germanium Alloys

Abstract

ABSTRACTStrained layer Si/Si0.79Ge0.21 superlattices consisting of 16 alternating 19.0 nm Si0.79Ge0.21 / 18.5 nm Si layers have been amorphized by Si ion irradiation, then implanted with H ions to nominal atomic concentrations of 1%, 0.1% and 0.05% within the amorphized region. Subsequent solid phase epitaxy (SPE) at a regrowth temperature of 575°C was monitored in situ by time resolved reflectivity (TRR) measurements, while changes in the H distribution were measured by elastic recoil detection analysis (ERDA). Analysis was supplemented by Rutherford backscattering spectrometry (RBS), x-ray double crystal diffraction and reflectivity (DCD/XRF) and transmission electron microscopy (TEM). TRR data reveals a decrease in the initial SPE rate in the Si substrate from 4.9 Å/sec (no H) to 2Å/sec for 1% H concentration as well as a rate decrease as the interface enters the Si/SiGe layers. TRR also indicates an increased roughness in the crystal/amorphous interface with increasing H concentration. ERDA reveals that a significant fraction of the implanted H is stable in the amorphous region for the anneal times (10-30 min) at 575°C, while in the regrown lattice the H concentration has dropped below 20 ppm, near the detection limit of the ERDA. DCD shows almost no strain in the regrown structures. TEM and RBS channeling techniques reveal degradation in the crystal quality of epitaxially regrown structures and a large concentration of strain relieving defects originating near the second deepest of eight SiGe layers in all regrown structures. XRF indicates decreasing sharpness of the regrown Si/SiGe interfaces with increasing H concentration.