First multicrystalline silicon ribbons using the continuous SDS process

Abstract

This paper reports the first results with both intrinsic and p-doped multicrystalline silicon ribbons obtained by the Continuous Mode Silicon over Dust Substrate process (SDS). The SDS is a two-step process in which the ribbons are obtained directly from a gaseous source, silane. In the first step the pre-ribbon is deposited by continuous optical fast CVD (COFCVD) on top of silicon powder at atmospheric pressure in a range of temperatures of the order of 700 °C. The powder substrate speed was of the order of 10 mm/min, and it was subjected to passing several heated zones created by a set of halogen lamps with elliptical mirrors. The pre-ribbon is crystallized by a floating molten zone technique known as Zone Melting Recrystallization (ZMR) to increase crystal quality while avoiding impurity contamination. As deposited, pre-ribbons have a porosity of 25-30%, which drops to zero after crystallization. The crystallized ribbons prepared so far have a typical size of 25 × 80 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and thicknesses below 400 μm. The measured effective carrier lifetimes were slightly higher than 3 μs, with as grown samples without surface passivation. The crystal grains are typically centimeters long and millimeters wide.