In this paper, we study the plasma-less etching of crystalline silicon (c-Si) by F2/N2 gas mixture at moderately elevated temperatures. The etching is performed in an inline etching tool, which is specifically developed to lower costs for products needing a high volume manufacturing etching platform such as silicon photovoltaics. Specifically, the current study focuses on developing an effective front-side texturing process on Si(100) wafers. Statistical variation of the tool parameters is performed to achieve high etching rates and low surface reflection of the textured silicon surface. It is observed that the rate and anisotropy of the etching process are strongly defined by the interaction effects between process parameters such as substrate temperature, F2 concentration, and process duration. The etching forms features of sub-micron dimensions on c-Si surface. By maintaining the anisotropic nature of etching, weighted surface reflection (Rw) as low as Rw < 2% in Si(100) is achievable. The lowering of Rw is mainly due to the formation of deep, density grade nanostructures, so-called black silicon, with lateral dimensions that are smaller to the major wavelength ranges of interest in silicon photovoltaics.

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In this article, we present an optimization of the emitter diffusion for nanotextured p-type monocrystalline silicon solar cells using atmospheric pressure dry etching (ADE) in conjunction with a post-ADE short acidic etch in a passivated emitter and rear cell (PERC) architecture. The optimization of the phosphorus oxychloride diffusion process was realized by first investigating the emitter sheet resistance and emitter recombination current density to achieve improved electrical properties and cell performances at a later stage. The optimization of the diffusion process enables an excellent homogeneity for emitter sheet resistance of 105 Ω/sq with minimized standard deviation of 3%, a decreased emitter saturation current density of ∼120 fA/cm 2 , a peak doping concentration of 2.2 × 10 20 cm −3 and depth of the highly doped surface region of 20 nm, still in the range that is required for good contact formation. By step optimization of the emitter formation of ADE textured PERC solar cells, an efficiency improvement of 0.6% abs could be reached leading to best conversion efficiency of 20.9%. Index Terms-Atmospheric pressure dry etching (ADE), diamond-wire sawn (DWS), p-type monocrystalline silicon (mono-Si), POCl 3 emitter diffusion, POCl 3 emitter optimization, passivated emitter and rear cell (PERC). I. INTRODUCTION I N RECENT years, low reflectivity nanotexturing processes sometimes referred as "black silicon" (B-Si), have generated large interest within the silicon-based photovoltaic industry, leading to higher solar cell performances [1]-[8]. The plasmaless fluorine-based atmospheric pressure dry etching (ADE) process [6]-[11] is one of the several other texturing methods that is being used to form nanotextured surface on silicon wafer, Manuscript

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