CURRENT PROGRESS IN EPITAXIAL LAYER TRANSFER (ELTRAN(R))

The quality of ELTRAN wafers has been improved by pre-injection in epi taxial growth, surface treatment just before bonding, high temperature annealing at bonding, high selective etching and hydrogen annealing. The pre-injection reduces defects. The surface treatment eliminates ed ge-voids. The high temperature bonding dramatically reduces voids all over the wafer. Hydrogen annealing is very effective for surface flatt ening and boron out-diffusion. In particular, the edge-void eliminatio n by the surface treatment just before bonding is greatly effective fo r enlarging the SOI area and reduces the edge exclusion down to only t wo mm. The gate oxide integrity is well evaluated. This process promis es high yield and through-put, because each of the steps can be indepe ndently optimized.