| Silk has been recently identified as a potential candidate for electrical, optical and bio-optical sensors because of its biocompatibility, biodegradability, mechanical strength and ease of processing. However in order to fabricate sophisticated micro and nano structures in silk, it is necessary to create high aspect ratio and vertical structures in silk. The aim of this project is to investigate the fabrication of deep and anisotropic structures in silk by plasma etching. The etching of silk was investigated in an inductively coupled plasma etching system which has separate control of the ion density and the ion energy of the plasma. Etching behavior of silk was studied as a function of pressure, temperature and gas composition. An etch rate as high as 0.27 mum/min was obtained without external biasing. The silk etch rate was found to be strongly dependent on ion density, but only weakly dependent on silk temperature. To verify the experimental results the plasma chemistry was simulated using MATLAB and etch rates were modeled. A good match between the model and the experimental result was obtained. Etching of silk patterned with gold was also performed with a radio-frequency bias of -40V applied to the silk sample. Anisotropic profiles were obtained and the etch rate for the patterned silk was found to be 0.67 mum/min. |
