Date of Award

12-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Committee Member

Professor Rodrigo Martinez-Duarte, Committee Chair

Committee Member

Professor Mark A. Blenner

Committee Member

Professor Xiangchun Xuan

Abstract

The phenomenon of T-topping has been deemed as an imperfection of the SU-8 photolithography process, due to light diffraction, overexposure of the SU-8, and other process parameters. The first objective of this work is to demonstrate that T-topping can be used as a microfabrication resource to produce suspended structures between photo-patterned high aspect ratio SU-8 posts, as precursors for carbon wires (width>1µm) and bridges (width>1µm). Such carbon structures could be used in a number of applications, such as the fabrication of nanowire based biosensors for the medical and food industry. The second objective is to develop a model able to predict what type of structures will be featured by an array of SU-8 posts, and in case of suspended structures, their length and width, in function of the particular choice of process parameters. The parameters examined are: type of contact, exposure time, type of gap, nominal size and nominal gap. A variety of suspended structures are obtained, and repeatable carbon wires of diameter as low as 800nm can be fabricated with the right choice of parameters. Given a choice of the parameters, the model proposed succeeds into predicting the presence and length of posts of hexagonal, squared and circular shape, but fails in calculating their width. The model needs future work to reliably calculate the width of the suspended structures, and needs to be calibrated for triangles and diamonds. Also, the SU-8 thickness will have to be integrated in the model.

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