Effect of implant temperature on defects created using high fluence of helium in silicon

Extended defects formed by high-fluence helium implantation in silicon have been studied as a function of the implantation temperature, from room temperature up to 800degreesC. Transmission electron microscopy results show that the formation of cavities created by a 50 keV He implantation with a fluence of 5 x 10(16) cm(-2) can be divided into three stages. For implantation temperature up to about 300degreesC the bubble size is relatively constant but the bubble density decreases due to the increase in dynamic annealing. Above 300degreesC, where divacancies are no longer stable and when the helium is mobile, both the density and size of the cavities stay relatively constant. In this stage, helium starts to diffuse out and the cavities become more and more faceted as the temperature increases. Concurrently interstitial-type defects appear: small elongated rod-like defects at relatively low temperatures and large ribbon-like defects at 600degreesC. Finally, for implantation at 800degreesC, no cavities are formed and only dislocation loops and {113}'s (ribbon-like defects and rod-like defects), are observed depending on the deposited energy profile. At this temperature the defect annealing during implantation becomes efficient to convert ribbon-like defects into dislocation loops. (C) 2003 American Institute of Physics.