Effects of arsenic doping on chemical vapor deposition of titanium silicide

This work examines the effects of implanted arsenic on nucleation and growt h of TiSi2 formed by rapid thermal chemical vapor deposition using SiH4 and TiCl4 as the precursors. In this study depositions were carried out in a t emperature range of 750 to 850 degrees C on Si substrates implanted with As atoms. The As implant doses ranged from 3 x 10(14) to 5 x 10(15) cm(-2). I t is shown that heavy dose As can result in a barrier to TiSi2 nucleation a nd enhance silicon substrate consumption. A surface passivation model is pr oposed to explain the effects. On Si, As provides a stable surface structur e which inhibits adsorption of SiH4 and TiCl4. Higher temperatures aid As d esorption from the Si surface providing nucleation sites. With moderate imp lant doses, As results in an incubation time whereas very high doses (great er than or equal to 5 x 10(15) cm(-2)) almost completely suppress nucleatio n. During deposition, As diffuses through the TiSi2 layer and plays a simil ar role on the TiSi2 surface. Because TiCl4 adsorption on TiSi2 is favored, the substrate supplies the Si atoms for TiSi2 formation resulting in enhan ced consumption. Because this process relies on Si diffusion through TiSi2, beyond a threshold thickness the efficiency of the Si diffusion process dr ops resulting in suppression of the deposition process. The results indicat e that the As dose also plays a role in grain size and surface morphology o f the deposited layers. Higher As doses result in smaller grained TiSi2 fil ms which san be attributed to the role of As in nucleation. (C) 1999 The El ectrochemical Society. S0013-4651(99)02-083-2. All rights reserved.