Extended defects formed by high-fluence He implantation into Si were studied as a function of implantation temperatures ranging from room temperature to 800C. Transmission electron microscopy results showed that the formation of cavities created by 50keV He implantation, to a fluence of 5 x 1016/cm2, could be divided into 3 stages. For implantation temperatures of up to about 300C, the bubble size was relatively constant but the bubble density decreased; due to the increase in dynamic annealing. Above 300C, where divacancies were no longer stable and when He was mobile, both the density and size of the cavities remained relatively constant. In this stage, He started to diffuse out and the cavities became more and more faceted as the temperature increased. Interstitial-type defects appeared concurrently: small elongated rod-like defects at relatively low temperatures, and large ribbon-like defects at 600C. Finally, for implantation at 800C, no cavities were formed and only dislocation loops and {113} defects (ribbon-like defects and rod-like defects), were observed; depending upon the deposited energy profile. At this temperature, defect annealing during implantation became efficient in converting ribbon-like defects into dislocation loops.

Effect of Implant Temperature on Defects Created using High Fluence of Helium in Silicon. M.L.David, M.F.Beaufort, J.F.Barbot: Journal of Applied Physics, 2003, 93[3], 1438-42