FORMATION OF SHALLOW BORON-DOPED LAYER FOR CHANNEL DOPING USING PREAMORPHIZATION

Formation of a shallow boron-doped layer for channel doping using preamorphization is studied. An extremely shallow boron-doped layer has been formed using preamorphization and rapid thermal annealing. Boron peak concentration around the surface is 3.5 x 1018cm-3 and the depth at which the boron concentration becomes 1 x 1017cm-3 is 450A. In contrast, the depth is as large as 900A for nonpreamorphized samples. The shallow boron-doped layer formation is made possible by enhanced diffusion arising from ion implantation damage as well as the channeling in the boron ion implantation being suppressed by preamorphization. MOS capacitors fabricated in preamorphized substrates have high-frequency steady-state C-V characteristics as good as those for nonpreamorphized MOS capacitors. Minority carrier lifetime for a preamorphized and rapid thermal annealed layer in the shallow region (roughly speaking, shallower than original amorphous/crystalline interface) is the same as that for nonpreamorphized samples. Surface state density is sufficiently small for preamorphized MOS capacitors as well as for nonpreamorphized capacitors. These results indicate that the shallow boron-doped layer formation technique using preamorphization can be applied to channel doping in MOSFET fabrication. copyright. © 1990, The Electrochemical Society, Inc. All rights reserved.