Fabrication of Long Range Surface Plasmon Polariton Biosensors incorporating Optical Waveguides and Encapsulated Microfluidic Channels via Wafer Bonding"

Abstract

A microfabricated structure incorporating optical waveguides and closed microfluidic channels is an essential component in realizing a practical long range surface plasmon polariton (LRSPP) biosensor. This has been achieved through advances in fabrication processes to realize reliable optical waveguides, and by development of a reliable wafer bonding process to create closed fluid channels. An existing process for fabrication of gold waveguides was modified by introducing ultra-shallow trenches to recess waveguides and present a planar surface for bonding. An improved fluidic channel etching process was characterized and successfully employed, yielding very smooth channel surfaces free from curtaining and grass issues. Optical performance of the complete bonded chips was demonstrated and verified using a cutback measurement method, producing an attenuation loss of 4.92 dB/mm. An alternative hot embossing process for formation of microfluidic channels on TOPAS substrate was investigated. Embossing die was produced on 4-inch silicon wafer using deep reactive ion etching (DRIE) to create 29 µm raised channels, and the die was subsequently used to transfer the channel structure to the TOPAS material. I would like to thank thesis supervisors Dr. Niall Tait and Dr. Pierre Berini, for providing me an opportunity to work in the area of microfabrication in general, and in particular, optical LRSPP biosensor project. It was a fascinating introduction to the field, and an excellent opportunity to learn from their extensive knowledge and experience. It was a great pleasure to work under their supervision and directions. I acknowledge and thank the Carleton University microfabrication staff, Rob Vandusen, Angela Williams and Rodney Aiton for providing training, consultation, and assistance in fabrication techniques and equipment operations. I also thank the staff at the University of Ottawa fabrication facility, Howard Northfield, Ewa Lisicka-Skrzek, Choloong Hahn, and Anthony Olivieri for their help and assistance in equipment usage and consultation. I extend my appreciation and thank my project colleague, Pengshuai Ren who acted as a close mentor for most of the project. I also thank and acknowledge Alex Krupin, Wei Ru, and Zohreh Hirbodvash for device testing. I acknowledge the assistance, consultation, and support received from Dr. Jeremy Upham and thank him for his contribution. I also appreciate the encouragement and motivation from Muhammad Osama Ali throughout this research work and acknowledge Raheel Ahmed for assistance in drawing the device schematics. Finally, I express deep gratitude to my parents, and my wife Saima and three innocent souls, Usva, Ibrahim and Emama for their continuous support and motivation throughout my studies.