Selective silicon epitaxial growth on a submicrometer WSi2 grating: Application to the permeable base transistor

Abstract

We report the silicon epitaxial growth on top of a tungsten disilicide grating using a rapid thermal processing, low pressure chemical vapor deposition reactor. The epitaxial growth of silicon is shown to proceed two dimensionally from the Si surface without reaction with the underlying WSi2 grid. Both lateral diffusion over WSi2 of Si adsorbed species and vertical diffusion of Si through the silicide film are shown to occur with respective weight depending on the width of the WSi2 lines. This allows silicon selective growth on patterned Si/WSi2 structure for grating periodicity below 1 μm. Preliminary electrical measurements of the Si/WSi2/Si overgrown permeable base transistor (PBT) thus fabricated are presented, showing current densities Jmax of up to 6000 A/cm2 and transconductancesg m of 5 mS/mm.