1. CREATING SILICON NANOSTRUCTURES WITH CONTROLLABLE SIDEWALL PROFILES BY USING FLUORINE-ENHANCED OXIDE PASSIVATION Sensing and Actuation in Miniaturized Systems PRESENTATION Ι 陳俊廷 9533701

2. Abstract  Controllable sidewall profiles by fluorine- enhanced oxide passivation  Protects the formed sidewall and ensures high aspect ratio nanostructures  Facilitates development of mechanical nanosensors Keyword ： nanostructure, reactive ion etching, fluorine-enhanced oxidation

3. Introduction  Cantilevers with high aspect-ratios are often desired  Etching rate of deep etching is relatively high, so that is hard to be precisely controlled  Expensive facilities and expertise hinder wide application  To avoid the limitations, this work provides an affordable nanofabrication and easy control of sidewall profiles

4. Fabrication After patterning a masking layer, a reactive ion etching (CF 4 +O 2 ) was performed. Anisotrophy is controlled by operational pressure. The sample was then exposed to the atmosphere with moisture and heated. By alternating the etching cycles and air exposure cycles, forming the nanostructures with flexible sidewall profiles.

5. Working Principle  During plasma etching, F being adsorbed on the surface form a SiO x F y layer.  Then exposed to the coexistence of oxygen and moisture Si-F → Si-OH → SiO 2  The fluorine-enhanced oxide layer postpones the attack of the sidewalls. The sidewall passivation is enabled.

6. Experimental Results (a)Nanopillars with vertical sidewalls. (b)Nanopillars with narrowed sidewalls. (For higher sensitivity)

7. Experimental Results  The sensitivity can be adjusted by changing the thickness of the bottom silicon layer  Apply to the force sensors for determination of mechanical response in small-scale objects

8. Conclusions  Demonstrate herein an approach to fabricate silicon nanostructures with controllable sidewall profiles.  These structures can be potentially used for nanomechnosensors to probe at nanoscale with superior sensitivities.

9. Source  Micro TA Systems 2006  Present by ：