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Lattice strain enhanced acidic etching on as cut sawn silicon wafer

  • The mechanical processing of silicon wafers leads to a heterogeneous lateral strain distribution and various modifications of the silicon, both of which influence the resulting topography after acid etching. In this study we investigate the influence of local strains and the initial topography of slurry and diamond wire saw wafers on the acid etching mechanism. The strain distribution is quantified and qualified by Raman microscopy before and after thermal treatment, while the topography is characterized by confocal microscopy before and after etching. The thermal treatment was used to selectively relax strains and investigate the effect of the individual strains on the etching mechanism. We found that amorphous silicon and compressive strained silicon are mainly present on the top most surface of the saw damage and do not influence the chemical reactivity of acid etching. In contrast, highly reactive tensile strained silicon is found up to 2.7 μm deep in the saw damage and acts as an etching mask. Rapid etching of the tensileThe mechanical processing of silicon wafers leads to a heterogeneous lateral strain distribution and various modifications of the silicon, both of which influence the resulting topography after acid etching. In this study we investigate the influence of local strains and the initial topography of slurry and diamond wire saw wafers on the acid etching mechanism. The strain distribution is quantified and qualified by Raman microscopy before and after thermal treatment, while the topography is characterized by confocal microscopy before and after etching. The thermal treatment was used to selectively relax strains and investigate the effect of the individual strains on the etching mechanism. We found that amorphous silicon and compressive strained silicon are mainly present on the top most surface of the saw damage and do not influence the chemical reactivity of acid etching. In contrast, highly reactive tensile strained silicon is found up to 2.7 μm deep in the saw damage and acts as an etching mask. Rapid etching of the tensile strained silicon by HF/HNO3/H2SiF6 leads to the formation of cracks with high local concentrations of intermediate species. These strains induced cracks are etched out together with the original saw damage induced cracks and trenches and form the final surface after etching. Furthermore, we can show how the tensile strain strength must have a relative Raman shift of at least −2 cm−1 to have an effect on the local etch rate. Our data demonstrate how mechanical treatment in combination with thermal treatment and acidic etching can be used to optimize the resulting topography for applications like photovoltaics. In addition, it provides a deeper insight into the acid etching mechanism for non-planar silicon wafers.show moreshow less

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Author: Steven HeroldORCiD, Jörg AckerORCiDGND
URL:https://www.sciencedirect.com/science/article/abs/pii/S1369800120315080
DOI:https://doi.org/10.1016/j.mssp.2020.105575
ISSN:1873-4081
ISSN:1369-8001
Title of the source (English):Materials Science in Semiconductor Processing
Document Type:Scientific journal article peer-reviewed
Language:English
Year of publication:2021
Tag:Raman microscopy; confocal microscopy; etching; lattice strain; reactivity; silicon
Volume/Year:123
Number of pages:11
Article number:105575
Faculty/Chair:Fakultät 2 Umwelt und Naturwissenschaften / FG Physikalische Chemie
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