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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NDUCTIVELY , PLASMA ETCHING
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