Low Temperature Deposition of Silicon Nitride Layers by Plasma Enhanced CVD For Large Area High Efficiency MC-Si Solar Cells

Bojan Karunagaran ,  Jinsu Yoo ,  Kim Do Young ,  Kyunghae Kim ,  Suresh Kumar Dhungel ,  Devanesan Mangalaraj ,  Junsin Yi 

Sungkyunkwan University, School of Information and Communication Engineering, 300 Chunchun-dong, Jangan-gu, Suwon 440746, Korea, South

Abstract

Silicon nitride (SiN) deposition using PECVD is a proven technique for obtaining layers that meet the needs of surface passivation and AR coating.In addition, the deposition process appears to provoke bulk passivation as well due to diffusion of atomic hydrogen.A further advantage of PECVD is that the process takes place at a relatively low temperature of 300C.This paper deals with the fabrication of multicrystalline silicon solar cells with PECVD SiN layers combined with high-throughput screen printing and RTP firing. Using this sequence we were able to obtain solar cells with an efficiency of 14% for mc-Si wafers of size 125 mm square. POCl3 doped polished silicon wafers with a junction depth of about 0.5 m and an emitter sheet resistance of 35 ohm/sq were selected for the cell fabrication.The mean cell efficiency, fill factor and Voc for the cells prepared in the present study were found to be 14%, 0.76 & 0.602V respectively. SiN deposition was performed using a horizontal PECVD reactor system consisting of a long horizontal quartz tube that was radiantly heated.Special and long rectangular graphite plates served as both the electrodes to establish the plasma and holders of the wafers.The electrode configuration was designed to provide a uniform plasma environment for each wafer and to ensure the film uniformity. These horizontally oriented graphite electrodes were stacked parallel to one another, side by side, with alternating plates serving as power and ground electrodes for the RF power supply.The plasma was formed in the space between each pair of plates.The optimized flow rates of N2, NH3& SiH4 for the deposition of SiN were 70, 50 & 10 sccm respectively.Working pressure was maintained at 650 mtorr.The SiN layer deposited under these optimized condition were found to have a thickness of approximately 70 nm and a refractive in 1.9 at 630nm.Currently we are on the process designing a new PECVD system which can be used for mass production.

 

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Presentation: oral at E-MRS Fall Meeting 2004, Symposium C, by Bojan Karunagaran
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-30 10:31
Revised:   2009-06-08 12:55