Black silicon technology and applications: Dissertation

This thesis focuses on fabrication, optimisation and integration of black silicon (bSi) for different applications. The research work presented in this thesis is divided into two parts. In the first part, bSi formation was studied in an inductively coupled plasma-reactive ion etcher (ICP-RIE). The design of experiments (DOE) technique was used to evaluate the influence of process parameters on bSi formation. The outcome was used to establish guidelines for fabricating different types of bSi. Applications of bSi are discussed in the second part of this thesis. Process development using standard and novel micro and nanofabrication techniques was performed to enable bSi employment for targeted applications. The developed processes were used to achieve patterned wetting of liquid droplets and a wide band optical enhancement. For patterned wetting, novel fabrication processes were developed to achieve patterns that composed extreme wetting contrast with the substrate. Hydrophobic, hydrophilic and superhydrophilic patterns were fabricated with superhydrophobic surroundings. Upon dispensing, the liquid droplets confined to more wettable patterns and mimicked their shape. Due to an extreme wetting contrast and topographical discontinuity, patterned wetting to a large number of patterns was achieved. A fabricated template containing patterns with extreme wetting contrast and topographical discontinuity with the surrounding substrate was used to demonstrate self-alignment of microchips. High accuracy, reliable and repeatable self-alignment of microchips was recorded. Several techniques were employed to improve the self-alignment of microchips on bSi based self-alignment template. Self-alignment of microchips is an increasingly popular technique for advanced packaging. Optical enhancement was achieved by optimisation of bSi surface structures. Improved anti-reflection and light trapping behaviour were demonstrated in UV-VIS spectrum. In order to extend the anti-reflection behaviour of bSi beyond UV-VIS, conformal pyrolytic carbon (PyC) coating was deposited and a substrate with exceptionally low reflectance over a wide spectrum (UV-NIR) was achieved. The surface structure optimisation was also exploited for plasmonic enhancement. Thin silver (Ag) films and different bSi surface structures were studied to achieve highly sensitive surface-enhanced Raman spectroscopy (SERS) substrate.