Rapid thermal processing, an integral part of shallow junction formation

Abstract

Rapid thermal processing (RTP) has become one of the important processing tools for shallow junction formation in ultralarge scale integration (ULSI). However, its application must be integrated with the choice of ion, energy and dose of the ion implantation to optimize and balance the conflicting requirements of minimum dopant penetration and minimum defect formation. The preamorphization of silicon which is widely used to eliminate channeling can lead to end-of-range dislocation formation and it strongly modulates the enhanced diffusion of boron. Preamorphization by silicon - a light ion - implantation leads to a high density of end-of-range dislocations but it can eliminate the enhanced boron diffusion under certain conditions. End-of-range defects are shown to cause junction leakage. Preamorphization by heavy ions results in fewer defects but its effect on boron diffusion is still being worked out. Both the formation of defects and the enhancement of the boron diffusion are due to excess silicon interstitials originating in the ion implant damage. The two most powerful tools to reduce excess interstitials are the use of heavy ions implanted at low energies and the use of RTP for annealing. © 1989.