OPTIMIZING STABILITY OF WET CHEMISTRY OXIDE PASSIVATION OF Si (111) AND Si (100)

Abstract

Numerous parameters are regulated in the wet chemical oxidation process for TOPCon/POLO solar cell technology to improve silicon oxide passivation (SiO2). Understanding the electronic properties, particularly the lifetime of the carriers and their thickness, requires knowledge of the properties of the surface of crystalline silicon (c-Si), which is subjected to native oxide etching, followed by wet chemical oxidation, such as nitric acid or hot water oxidation and various hydrogenation methods. The results of these processes are tracked with lifetime measurement equipment, and spectral ellipsometry is used to measure the thickness of the oxide layer by using the single-sided polished wafers with surface orientation (1 1 1). In addition to the actual values, their time stability is also tracked.
Before the hydrogenation step was introduced, the wafers’ lifetime was approximately 0.001 ms, which is less than the bulk lifetime; with the hydrogenation, the lifetime increased by more than an order of magnitude for a relatively long time with no difference between (1 1 1) and (1 0 0) wafers indicating that hydrogenation of the Si/SiO2 interface is performed.