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Silicon Etching Using Chlorine Based Plasma

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Silicon Etching Using Chlorine Based Plasma Silicon Etching using Chlorine based plasma for High Selectivity and High Etch Rate. Abstract : Silicon Etching using Inductively Coupled Plasma (ICP) in Cl2/BCl3 Plasma, under various Source power, Platen power, Pressure, Flow rates and Temperature are presented. We achieved an Etch Rate (ER) of 350 nm/min and Selectivity (SEL) of 35 with SiO2 hard mask. The experiment was conducted on Oxford Instruments Plasma Lab system 100 ICP 180 at James Watt Nanofabrication Centre, University of Glasgow. Introduction : Plasma is an ionized gas with approximately Etchant Radicals ↑ equal number of positively charged particles (positive ions) and Chemical Reaction ↑ negatively charged particles (electrons), and different numbers Thus, Etch rate ↑. of excited and unexcited neutral particles [1]. Plasma based dry etching, enables processing at comparatively low temperature , Now, Selectivity almost wide area can be processed uniformly ,achieve anisotropic etch same Chlorine etch and direction of etching can be controlled [2]. Silicon fast as compared to SiO . ICP generates high density, low pressure plasma which allows 2 independent control of ion flux and ion energy[3].In ICP, a coil is wrapped around a cylindrical dielectric vacuum vessel. When RF current flows through coil, RF magnetic flux is produced Etchant Radicals ↑ along the axis of cylinder. This flux induces RF electric field Chemical Reaction ↑ inside the vessel. Electrons in vacuum vessel are accelerated Thus, Etch rate ↑. by this electric field and dense plasma is produced [1]. Now, Experiment : Consist of analyzing the effects of various Chemical Reaction ↑ plasma parameters on etching of silicon with SiO as hard 2 Thus, Selectivity ↑. mask. Finally deduce an optimized recipe which provides anisotropic etch with high selectivity and high etch rate. Finalized recipe was used to etch silicon with SiN and 8um thick photoresist mask. Temperature was reduced from 200C to 00C. No change was Results and Discussion : observed in etch rate and selectivity, but verticality of etched profile was improved, as a result of enhanced passivation layer. Helium back cooling pressure was varied from 0T to 15T. No change in etch Source Power ↑ rate and selectivity was found, but at low pressure, verticality of Plasma density ↑ profile improved. Ions & Radicals ↑ Thus, Etch rate ↑. Finalized Recipe: Source Power = 2000 Watt, Bias Power=60 Watt, Pressure=25mT, Now, Plasma Density ↑ Temperature=00C,Heluim back cooling=5T, Time=10min.Pictures Etch rate of mask ↑ below show the silicon etched with SiO , SiN and photoresist masks Thus, Selectivity ↓. 2 respectively. Etch rate is in nm/min. Bias Power ↑ Ion Energy ↑ Bias Voltage ↑ Milling Rate ↑ Thus, Etch Rate ↑. Now, Milling Rate ↑ ER=350,Sel=35 ER=320,SEL=16 ER=300,SEL=1 Etch Rate ↑ Thus, Selectivity ↑. References: [1] M. Sugawara , “Plasma Etching ; Fundamentals and Applications” Pressure ↑ , Oxford University Press, New York, 1988. No. of Molecules ↑ Ions & Radicals ↑ [2]. Stephen M.Rossnagel, Jerome J.Cuomo, William D.Westwood, Thus, Etch rate ↑. Handbook of plasma processing technology, Noyes publication, August 11, 2013. Now, No. of Molecules ↑ [3]. C.Y. Chang and S.M. Sze, ULSI Technology, McGraw-Hill(1996). Etch rate ↑ Thus, Selectivity ↑. Author : Kratika Jakhar (2056073J) MS.c in Electronics And Electrical Engineering. Supervisor : Haiping Zhou. University of Glasgow, charity number SC004401 .
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