Comparisonc of remote vemote versus direct PECVD silicon nitride.pdf

Presented at the 2nd World Conference on Photovoltaic Solar Energy Conversion, Vienna, 1998. 1 COMPARISON OF REMOTE VERSUS DIRECT PECVD SILICON NITRIDE PASSIVATION OF PHOSPHORUS-DIFFUSED EMITTERS OF SILICON SOLAR CELLS Beate Lenkeit1, Thomas Lauinger2, Armin G. Aberle1, and Rudolf Hezel1 1Institut für Solarenergieforschung Hameln/Emmerthal (ISFH), Am Ohrberg1, D-31860 Emmerthal, Germany Tel.: (+49)5151-999-304, Fax: (+49)5151-999-400, Email: lenkeit@isfh.uni-hannover.de 2ASE GmbH, Industriestrasse 13, D-63755 Alzenau, Germany ABSTRACT: At present, plasma-enhanced chemical vapour deposited (PECVD) silicon nitride (SiN) films act as the most efficient low-temperature surface passivation and antireflection (AR) coating for Si solar cells. This work presents a comprehensive experimental comparison of the surface passivation properties of n+-diffused silicon surfaces passivated by either remote or direct PECVD SiN films. Carrier lifetime measurements are performed on phosphorus-diffused SiN/n+/p/n+/SiN test structures to determine the emitter saturation current density J0E and the surface passivation quality. Our experimental study includes: (i) determination of the influence of the SiN deposition parameters by means of design-of-experiments methods, (ii) variation of the emitter profile, (iii) UV stability testing, (iv) thermal stability testing at 500°C in a forming gas ambient and at 800°C in air, and (v) the determination of the impact of the front metal grid on J0E. Remote-plasma SiN and high-frequency direct-plasma SiN films both are found to give very good surface passivation on phosphorus-diffused n+-emitters, provided that the refractive index is above 2.0. This emitter surface passivation is stable under UV illumination and during a 60-min post-deposition anneal in forming gas at 500°C. In contrast, low-frequency direct-plasma SiN films give much poorer surface passivation. Keywords: Silicon-Nitride – 1: Passivation – 2: c-Si - 3 1. INTRODUCTION Presently, in a