Abstract

This letter investigates chemical polishing with a hydrofluoric acid, nitric acid, and acetic acid (HNA) mixture as an alternative to chemical mechanical polishing (CMP) to produce smooth surfaces on both slurry- and diamond-cut silicon solar wafers. With 30 µm of silicon etched from each side, as-cut wafers appear mirror-like to the naked eye. A quantitative analysis of the specularity of HNA-polished wafers indicates that 97 % of light reflected from slurry-cut wafers falls within ±10 mrad of the specular beam and is isotropically distributed. Conversely, HNA-polished diamond-cut wafers retain a history of the wafer-sawing process: the reflected light is anisotropic with 99.4 % of light within ±10 mrad of the specular beam in the sawing direction but only 89.1 % within ±10 mrad in the perpendicular direction. Topographical characterization by optical profilometry and atomic force microscopy measurements reveals that HNA-polished slurry-cut wafers are spatially uniform with a surface roughness of 45 nm. Diamond-cut wafers have a roughness of only 18 nm but also have residual sawing grooves tens of micrometers across—these are responsible for the anisotropic scattering of light. The HNA-polished wafers are appropriate alternatives to CMP wafers for high-efficiency solar cells, including interdigitated-back-contact and tandem cells that require single-side polished wafers, as well as for other optical applications such as process monitoring with characterization techniques that require planar substrates.

Original languageEnglish (US)
Pages (from-to)10270-10275
Number of pages6
JournalJournal of Materials Science: Materials in Electronics
Volume27
Issue number10
DOIs
StatePublished - Oct 1 2016

Fingerprint

Chemical polishing
Silicon
Silicon wafers
polishing
Diamond
Sawing
wafers
Light
silicon
Diamonds
Chemical mechanical polishing
Hydrofluoric Acid
Nitric Acid
Surface roughness
Atomic Force Microscopy
Hydrofluoric acid
Profilometry
Acetic Acid
Process monitoring
Nitric acid

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biophysics
  • Bioengineering
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Biomedical Engineering
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Cite this

Silicon wafers with optically specular surfaces formed by chemical polishing. / Yu, Zhengshan; Wheelwright, Brian M.; Manzoor, Salman; Holman, Zachary.

In: Journal of Materials Science: Materials in Electronics, Vol. 27, No. 10, 01.10.2016, p. 10270-10275.

Research output: Contribution to journalArticle

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