Development of etch hillocks on different Si(hkl) planes in silicon anisotropic etching

Zubel, Irena; Kramkowska, M.

doi:10.1016/j.susc.2008.03.010

Cited by 21 publications

(15 citation statements)

References 24 publications

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“…More careful examination of the features usually suggests otherwise [10,11]. Indeed, in fields of micromachining, texture features have been studied extensively [10][11][12][13][14]. However, relatively few conclusions have been transferred into the analysis of surface texture in silicon solar cell applications.…”

Section: Introductionmentioning

confidence: 99%

Reflection distributions of textured monocrystalline silicon: implications for silicon solar cells

Baker-Finch

McIntosh²

2012

Progress in Photovoltaics

101

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A common misconception is that alkaline textured silicon solar cell surfaces are characterised by features that are pyramidal and bounded by {111} planes. In preference to the typical approach of observing scanning electron microscope images, we analyse reflection distributions from various pyramidal textures and find that {111} faceted pyramids are a poor approximation to the features on such surfaces. We conclude that features are hillocks, with an octagonal base. Furthermore, the characteristic base angle of the texture depends on the etchant and is closer to 50–52° than the commonly accepted value of 54.74°. Analyses of antireflection, light trapping, photogeneration and surface recombination properties of textured surfaces should take this feature morphology into account. The base angle has a strong influence on the hemispherical reflectance of the textured surface, with higher angles resulting in reduced reflectance. The influence of this reflection enhancement upon device performance is smallest when an optimised antireflection coating is applied; compared with an array of {111} faceted pyramids, a hillock morphology with 50° base angle results in a 0.2% reduction in photogenerated current in a typical cell. Additionally, as base angle is reduced, an encapsulant of increasingly higher refractive index is required to drive internal reflection at the air–glass interface of light initially reflected from the cell surface. The development of texturing processes resulting in higher base angles is encouraged. Copyright © 2012 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Reflection distributions of textured monocrystalline silicon: implications for silicon solar cells

Baker-Finch

McIntosh²

2012

Progress in Photovoltaics

101

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“…In those papers, modification of the surface tension is usually achieved by the addition of surfactants to the etchant. The subsequent analysis of the results has often focused mainly on the surfactants impact on the roughness of the etched surfaces produced [8,[12][13][14][15][16][17][18]. Zubel et al determined etch rates for KOH and TMAH solutions with and without additives [9-11, 17, 18].…”

Section: Introductionmentioning

confidence: 99%

Surface tension and its role for vertical wet etching of silicon

Brockmeier

Rodriguez

Harrison

et al. 2012

J. Micromech. Microeng.

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In this paper, we present for the first time a systematic investigation of the role of the surface tension in anisotropic wet etching of silicon, focusing on the sidewall angle. We show that in the KOH and NaOH solutions with high surface tension a reliable fabrication of vertical sidewalls is possible. Etching experiments on (1 0 0)-Si and surface tension measurements via bubble pressure tensiometry were conducted using inorganic etchants in a wide range of concentrations. Finally, the surface tension of the etching solutions was identified as an important quantity that determined the etching behavior, while concentration dependences were eliminated by controlling the surface tension using temperature.

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“…As a result, the silicon post will form an octagonal cross section. 10,12 By combining both isotropic and anisotropic etching, we obtained an optimized equilateral octagonal shape. Figure 1 shows the fabrication process.…”

Section: Fabricationmentioning

confidence: 99%

Octagonal toroid microcavity for mechanically robust optical coupling

et al. 2015

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Light is usually coupled to a whispering gallery mode cavity using a tapered fiber. However, it is difficult to stabilize the optical coupling against mechanical vibration because it requires sub-μm control of the gap distance between the fiber and cavity. In this study, we experimentally demonstrate mechanically robust coupling that we realize by allowing the tapered fiber to touch the sidewall of the cavity. By using an octagonal toroid microcavity, we prevent the cavity-waveguide system from over coupling and achieve critical coupling even when the fiber is in contact with the surface of the cavity. We show by numerical analysis that such a deformed microcavity is required if we need to control the coupling, since a circular cavity usually overcouples when the fiber contacts the surface. The fabricated octagonal silica toroid microcavity exhibits a quality factor of 2.2 × 104 when the tapered fiber touches a cavity with a diameter of 80 μm.

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Development of etch hillocks on different Si(hkl) planes in silicon anisotropic etching

Cited by 21 publications

References 24 publications

Reflection distributions of textured monocrystalline silicon: implications for silicon solar cells

Reflection distributions of textured monocrystalline silicon: implications for silicon solar cells

Surface tension and its role for vertical wet etching of silicon

Octagonal toroid microcavity for mechanically robust optical coupling

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