High-quality epitaxial layer transfer (ELTRAN) by bond and etch-back of porous Si

The small thickness variation and the high crystalline quality in the SOI films are required for the large scale integration of devices. BESOI is one of the attractive methods due to its layer thickness versatility and productivity particularly in large-scale wafers. Recently, we have reported a novel BESOI method, in which an epitaxial layer on porous Si is transferred onto another handle wafer by bonding and etching back of porous Si (ELTRAN). The structure difference and the abrupt interface between porous and bulk Si gives the very high etching selectivity (10⁴-10⁵), so that it can replace the dopant-sensitive selective etching in the existing BESOI, and allow high-temperature heat treatments (⩾1100°C) both to grow the good epitaxial layer and to increase the bonding strength. In this paper, the high etching selectivity and the resultant SOI thickness uniformity are discussed. The crystalline quality of the SOI layer is evaluated by defect delineate etching and p-n junction diodes