Simple and versatile UV-ozone oxide for silicon solar cell applications

• Published in: Solar energy materials and solar cells Vol. 185; no. C; pp. 505 - 510
• Main Authors: Bakhshi, Sara, Zin, Ngwe, Ali, Haider, Wilson, Marshall, Chanda, Debashis, Davis, Kristopher O., Schoenfeld, Winston V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2018; Elsevier BV; Elsevier
• Subjects: Absorption cross sections; Aluminum; Aluminum oxide; Capture cross section σn(or σp); Carrier lifetime; Cell surface; Cleaning; Conductance; Current density; Deep level transient spectroscopy; Effective carrier lifetime τeff; Field-effect passivation; Frequency dependence; Industry standards; Interfacial trap density Dit; Ozonation; Ozone; Passivity; Photovoltaic cells; Photovoltaics; RCA; Recombination; Resistance; Saturation; Saturation current density J0; Semiconductors; Silicon; Solar cells; Spectroscopy; Surface passivation; TEM; Total fixed charge Qtot; UV-ozone cleaning; Interfacial trap density Dit; Effective carrier lifetime τeff; RCA; Field-effect passivation; Capture cross section σn(or σp); UV-ozone cleaning; Total fixed charge Qtot; TEM; Surface passivation; Saturation current density J0
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2018.06.006

Semiconductor surface clean is sometimes perceived as costly but long recognized as pivotal in determining the final semiconductor device performance and yield. In this contribution, we investigated the effectiveness of crystalline silicon surface cleaning by a simple UV-ozone process in comparison to the industry standard RCA clean for silicon photovoltaic applications. We present a unique method of processing the silicon surface effectively by UV-ozone cleaning. Despite being simple, UV-ozone cleaning results in a superior surface passivation quality that is comparable to high-quality RCA clean. When used as a stack dielectric—UV-ozone oxide overlaid by aluminum oxide—the thickness of UV-ozone oxide plays an important role in determining the passivation quality. Of all treatment times, 15 min of UV-ozone treatment results in an outstanding passivation quality, achieving the effective carrier lifetime of 3 ms and saturation current density of 5 fA/cm2. In addition, we present a simple and effective technique to extract values of electron/hole capture cross-section for the purpose of analyzing the interface passivation quality from already measured surface recombination parameters of saturation current density, interfacial trap density and total fixed charge, instead of measuring on the separately prepared metal-insulated-semiconductor (MIS) samples by the techniques: frequency-dependent parallel conductance or deep-level transient spectroscopy. •UV-ozone clean technique provides an effective cleaning efficiency, comparable to the industry standard high-quality RCA clean.•UV-ozone oxide also provides the outstanding chemical passivation.•Passivation quality is found to vary with UVo thickness, with 15 min of UV-ozone oxide deposition time being an optimum.•UV-ozone oxide/AlOx passivation stack provides high-quality passivation, achieving J0 of 5 fA/cm2 (per side).•A reliable, simple and less-time consuming technique to extract electron/hole capture cross section parameters is presented.