Modification of Porous Silicon Formation by Varying the End of Range of Ion Irradiation

Abstract

We have studied the influence of the end of range defects in silicon created by high energy protons and helium ions on subsequent porous silicon formation. The defect generation rate at the end of range is typically ten times higher than that close to the silicon surface. For low fluence irradiation, only the end-of-range region contains enough defects to prevent anodization whereas the low-defect regions closer to the surface are anodized. By varying the end-of-range depth over small lateral distances, silicon lines with tip radii of nanometers were fabricated for low fluence irradiation. For a high fluence irradiation we demonstrate how porous silicon formation is confined to buried channels by selectively producing regions on the silicon surface with two different ends of ranges.

Thermal Properties of Porous Silicon

“…3. Ion implantation affects the conditions of PSi formation (Ambrazevicius et al 1994;Pavesi et al 1994;Ahmad and Naddaf 2011;Ow et al 2011). For example, Pavesi et al (1994) suggested that the porosity of silicon could be controlled by implanting Si ions into the initial wafer.…”

Three-dimensional silicon micromachining

“…The resist is thin enough, so that protons can penetrate the underlying silicon. Because of the resist thickness, the proton end-of-range depth in the silicon is modified according to the Similarly, patterned photoresists with sloping sidewalls may be used to vary the proton end-of-range laterally to fabricate silicon lines with nano-sized tips [57], figure 9(e). The flat top of the photoresist is thick enough to completely stop the incoming ions from reaching the underlying silicon.…”

Fabrication of complex curved three-dimensional silicon microstructures using ion irradiation

“…Hence, while figure 7 shows results obtained using a period of 10 μm, it becomes increasingly difficult to fabricate with smaller period. We can overcome this limitation by using a more heavily doped p-type wafer, such as that used in previous studies [24,[26][27][28]. The higher doping level makes it easier to leave sufficiently conducting paths for the hole current to flow through a more densely packed structure.…”