Si nanostructures have been fabricated by focused ion beam implantation (FIB) followed by etching in KOH/IPA. The FIB implantation into Si at a sufficiently high dose (≥1015/cm2) renders the local Si region much less susceptible to chemical etching. This effect has been observed for FIB implantation with Ga, Au, and Si ions. After etching, the implanted layer forms a cantilever structure whose thickness is a function of the implantation energy. At low energies (<30 keV) nanometer-scale Si structures can be formed using this technique.

The incubation time (ti) for the onset of porous Si formation by stain etching in HF:HNO3:H2O was observed to be a strong function of dopant type and concentration. For B-doped p-Si, ti increased significantly with substrate resistivity (ρ), from ∼0.5 min for 0.004 Ω cm to ∼9 min for 50 Ω cm. P-doped n-Si substrates exhibited a ti which decreased with increasing ρ, from ∼10 min for 0.15 Ω cm to ∼8 min for 20 Ω cm. We have utilized the difference in ti between n- and p-type Si to produce selective area photoluminescence (PL) by Ga+ focused ion beam (FIB) implantation doping and B+ broad beam implantation doping of n-type Si. Using 30 kV FIB Ga+ implantation, PL patterns with submicrometer resolution have been obtained for the first time.

We report on a quantitative investigation of doping-induced contrast in photoelectron emission microscopy (PEEM) images of Si devices. The calibration samples were fabricated using standard photolithography and focussed ion beam (FIB) writing, and consisted of p-type (B) stripes of different nominal dopant concentrations (10 18 -10 20 cm -3 ) and line separations, written on n-type (N d =10 14 cm -3 ) Si(001) substrates.Using a near-threshold light source, we find that the signal intensity increases monotonically with B concentration over the measured range of doping. The measured intensity ratios are in good agreement with a calculation based on photoemission from the valence band.

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Atomic-scale imaging has been achieved on β-SiC surfaces using scanning tunneling microscopy in air. SiC films were grown on Si (100) substrates by chemical vapor deposition using the carbonization reaction of the surface with C3H8, followed (for films thicker than 100 nm) by the reaction of C3H8 and SiH4. For a relatively thick SiC (∼6 μm) film, the average nearest-neighbor surface atomic spacing measured was 3.09 Å, which is very close to the nominal value of 3.08 Å. Several of the thinner (<100 nm) SiC films exhibited significantly larger atomic spacings, indicating the strong effect of the larger atomic spacing (nominally 3.84 Å) of the Si substrate.

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Diodes have been fabricated by on-axis Ga+ focused ion beam (FIB) implantation at 4–25 keV into n-Si 〈100〉 wafers doped to 2×1015/cm3. Post-implantation anneal was performed at 600 °C for 30 s to electrically activate the Ga and to regrow the implanted layer. SIMS measurements performed to obtain the Ga concentration depth profile indicate good agreement with trim simulation even at low energies. At 4 keV an electrical junction depth of 15 nm is obtained from spreading resistance profiling (SRP). The junction depth was found to vary linearly with energy over the range explored. The electrical properties of the diodes were obtained from I-V characteristics. The leakage current density of the 5 keV diode was measured to be 1 and 20 nA/cm2 at a reverse bias of 1 and 5 V, respectively. The corresponding leakage current density values for the 10 and 15 keV diodes were between 25% and 50% lower than those reported for 5 keV. The reverse bias breakdown voltage was between 105 and 110 V for all diodes. The combination of nanometer-scale junction depth, low leakage current density, and high breakdown voltage indicate that low energy Ga FIB implantation is a promising technology for ultrashallow p+ -n junction fabrication.

A novel fabrication technique involving the use of focused ion beam (FIB) selective implantation to fabricate nanostructures on crystalline Si substrates in conjunction with anisotropic etching is described. Using this maskless & resistless approach, Si nanostructures were fabricated by FIB implantation of Ga+ at doses from 1015 to 1016/cm 2. Wet etching in KOH/IPA does not attack the implanted region, while it removes the underlying Si anisotropically, with a very low etch rate on the {111} planes. The result is a cantilever-like structure whose thickness is dependent on the implantation energy and dose. Pre-etching rapid thermal annealing at 600°C for 30 sec does not prevent structure fabrication and post-etching RTA does not affect the shape of the structures.