ANALYSIS OF N(+)P SILICON JUNCTIONS WITH VARYING SUBSTRATE DOPING CONCENTRATIONS MADE UNDER ULTRACLEAN PROCESSING TECHNOLOGY

Using highly controlled ultraclean processing technology, marked impro vements in n(+)p Si junction quality are achieved presenting a theoret ical significance. Boron-doped substrates with various boron doping co ncentrations N-s were As+ implanted, forming the n(+) junction sides. The diffusion (Id) and generation (I-gen) currents, as well as the ide ality and the generation factors, are significantly reduced, and bulk generation lifetimes are prolonged. Using Shockley-Read-Hall theory it is found that a deviation of the trapping centers energy (E(t)) from the midband-gap energy (E,) is responsible for the improvements. The e xperimental results show that \E(t)-E(i)\ is a function of N,, and tha t the I-gen/I-d ratio is significantly low. Accordingly, it is propose d that I-gen/I-d ratio should be regarded, under certain conditions, a s a figure of merit for junction quality. It is concluded that the \E( t)-E(i)\ deviation is related to the ultraclean processing technology used, due to the formation of new energy levels far from Ei and the su ppression of introduction of new energy levels near Ei. Surface genera tion currents were found experimentally to be significant, and thus no t negligible. Surface effects in general demonstrated similar trends t o the bulk generation effects. (C) 1997 American Institute of Physics.