TOPCon Tunnel-Oxide Thickness Control: Process-Window Determination Using In-Line Spectroscopic Ellipsometry and Statistical Tolerance Modeling

Abstract

Tunnel-oxide passivated contact (TOPCon) cell architectures depend on the precise thickness control of an interfacial silicon-oxide layer in the 1.2 to 1.8 nanometer range, where small thickness deviations produce disproportionately large carrier-recombination and contact-resistance penalties. This work presents an in-line spectroscopic ellipsometry methodology adapted for the throughput cadence of industrial cell lines and develops a statistical tolerance model linking measured oxide thickness to expected open-circuit voltage and fill-factor distributions. We characterize the sensitivity of the methodology to absorber-doping background, surface roughness, and interfacial nitride incorporation. Implications for inline qualification gating, recipe-window definition, and supplier wafer-quality specification are discussed in detail. The work supports the broader transition of TOPCon manufacturing from research-line precision to industrial robustness.