INDUCTIVELY COUPLED PLASMA ETCHING ON GaN
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Date
2010-01
Authors
ROSLI, SITI AZLINA
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Abstract
In this project, the research mainly focused on the investigation of the
influence of the various plasma mixtures (H2 and Ar) in Ch-based on GaN using dry
etching majoring in Inductively Coupled Plasma etching to obtain highly anisotropic,
vertical sidewalls structures and most importantly, highly etch rates for optimum
device performance. First of all, the wafer was fabricated using the conventional
photolithography method and the Ni metals were coated onto the n-GaN or p-GaN
wafer through evaporator equipment to make lift-off process. After that, the wafer
was etched using ICP-RIE machine. During the process, the gas flow rates for Ar or
H2 were varied while Cb rates were held constant at 60sccm for all experiments. The
conditions consisted of 60sccm of Ch and the total flow rate 60sccm of Ar or 30sccm
of H2• Meanwhile, ICP power, RIE power and RF power was held at lOOW, 250W
and 600W respectively. Prior to etching patterned samples, a simple set of
experiments were conducted to get an understanding of how changes in gas
composition affect the etch rate. For this experiment, the flow rate was varied from
Osccm to 60sccm using Ar gases or from Osccm to 30sccm using H2 gases,
meanwhile the Ch flow rates and the chamber pressure were held constant at 60sccm
and lmTorr, respectiveiy. Then, the various pressures were varied starting of lmTorr
to 15m Torr to observe the effect of etch rates and the roughness of surface and lastly,
the ICP power applied from lOOW to 450W. After that, the wafer will be
characterized using SEM and AFM. SEM will be used to measured the etch rates,
anisotropic etch profiles and sidewalls meanwhile AFM has been used to quantify
the etched surface morphology as root-mean-square (rms) roughness. From our
experiments, the addition of 15sccm H2 together with Chin the chamber at 5mTor of
pressure and 200W ICP power obtained high etching rate about 3000Aimin for nGaN
and 1900Aimin for p-GaN and smooth anisotropic pattern. Meanwhile, for
addition of 60sccm Ar together with 20sccm Ch at pressure of 5mTorr and 20W ICP
power resulting the highest etch rates, better than the addition of H2; 5000Aimin for
n-GaN and 3300Aimin for p-GaN, while maintaining the smooth surface; -0.5nm for
n-GaN and -0.7nm for p-GaN. Hence, it was found that the addition of H2 to
chlorine plasma distributed a smooth etched surface better than Ar, while addition of
Ar resulting the highest etching rates for this research.
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Keywords
NDUCTIVELY , PLASMA ETCHING