TITLE:
Surface Roughness Modification of Free Standing Single Crystal Silicon Microstructures Using KrF Excimer Laser Treatment for Mechanical Performance Improvement
AUTHORS:
Mohamed Elwi Mitwally, Toshiyuki Tsuchiya, Osamu Tabata, Sherif Sedky
KEYWORDS:
Freestanding Mechanical Test Structures, Harsh Laser Treatment, Surface Roughness Improvement
JOURNAL NAME:
Journal of Surface Engineered Materials and Advanced Technology,
Vol.5 No.1,
January
6,
2015
ABSTRACT: Single crystal silicon freestanding structures for tensile and fatigue testing were treated with KrF
excimer laser to improve surface roughness and accordingly mechanical performance. Sample
thickness was 5 μm. Localized laser treatment was successful in eliminating the scallops developed
during Bosch process and in reducing surface roughness. Harsh irradiation at laser energies
up to 4 J/cm2 was only possible due to localized treatment without significant vibrations occurring
on the freestanding samples that led to fracture in preliminary experiments at energies as low as
0.16 J/cm2. Finite element analysis was used to investigate the temperature distribution on the
irradiated structures. Atomic force microscopy (AFM) and Raman spectroscopy were also used to
assess surface roughness, crystallinity changes and surface stresses developing on surfaces subjected
to perpendicular laser irradiation. At a high energy (3.2 J/cm2) the top surface showed a
decrease of roughness compared to fabricated samples. Raman spectroscopy showed the dominance
of crystalline silicon after laser irradiation. The effects of laser energy, number of pulses