Fabrication Of Two Dimensional Silicon Photonic Crystal
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Date
2010-03
Authors
Sin, Yew Keong
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Photonic crystals are materials with a periodicity in refractive index. When
electromagnetic waves with a wide range of frequencies propagate through these
materials, certain range of frequencies is prohibited. The prohibited frequencies are
known as photonic bandgap. In this study, a two dimensional silicon photonic crystal
is fabricated by microfabrication method. Electron beam lithography and etching
process are important processes in this method. Hence, preliminary works on
optimization parameters in electron beam lithography are necessary. The relations
between parameters like beam voltage, beam current, beam dosage and packing
factor are studied to ensure lithography process works properly. Subsequently,
various types of etching process are applied to create two dimensional photonic
crystals structure into a silicon wafer. Scanning electron microscope is the
monitoring tool for the whole process by running surface characterization on each
fabricated structure. Photonic bandgap is calculated by MIT Photonic-bands package
software and the structural color effect of photonic crystal is observed with a simple
setup. From the result of preliminary works, the relations of parameters are higher
beam dosage is required when higher beam current and higher beam voltage are
applied, or a low packing factor structure is exposed during electron beam
lithography. With 30kV as electron beam voltage and 75pA as electron beam current,
electron beam dosage for exposing the structure with 0.65 as packing factor was
177μC/cm2. Overexposure occurred when electron beam dosage higher than this
value was applied for this combination of parameters. During fabrication, reactive
ion etching is the appropriate tools for etching. Finally, a two dimensional photonic
crystal structure is successfully fabricated on an n-type silicon wafer with (100)-
orientation. The calculated photonic bandgap of this photonic crystal is in the range
2.08-2.73μm.
Description
Keywords
Photonic crystals are materials , with a periodicity in refractive index