A servo guided <i>X</i>–<i>Y</i>–theta stage for electron beam lithography

Kendall, Rodney

doi:10.1116/1.585361

Cited by 13 publications

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“…10 The most commonly used anisotropic etches are KOH-based. Various studies have found that the etch rate on ͕111͖ surface orientations is considerably lower than that on ͕100͖ surfaces, [11][12][13][14] sometimes by a factor of as much as 200. 11 When such an etch is applied to a ͕100͖ oriented surface, pyramidal features, referred to as hillocks, with perfect ͕111͖ faces are formed.…”

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“…Various studies have found that the etch rate on ͕111͖ surface orientations is considerably lower than that on ͕100͖ surfaces, [11][12][13][14] sometimes by a factor of as much as 200. 11 When such an etch is applied to a ͕100͖ oriented surface, pyramidal features, referred to as hillocks, with perfect ͕111͖ faces are formed. 12,13 On arbitrarily oriented crystals, the behavior of anisotropic etches becomes more complicated.…”

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Determination of Grain Orientations in Multicrystalline Silicon by Reflectometry

Wang

Murphy

Wilshaw

2010

J. Electrochem. Soc.

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At present there is no quick and simple method to determine the type and orientation of grains in multicrystalline silicon, which is commonly used for photovoltaic applications. In this paper, a novel method for performing such measurements is described. A laser beam is reflected off an anisotropically etched multicrystalline silicon surface. An optimized KOH-based etch produces defined facets with ͕001͖, ͕111͖, ͕113͖, ϳ͕133͖, and ϳ͕335͖ orientations. Reflections from the different facets then produce spots in a reflection pattern produced on a suitably placed screen. The pattern produced is characteristic of the grain type, with ͕001͖-, ͕110͖-, and ͕111͖-type grains being clearly distinguished in over 90% of the cases. An analysis of the position of the spots allows the orientation of the facets producing them to be determined. These orientations are used to determine the orientations of the underlying grain to within ϳ6°relative to measurements made by electron backscatter diffraction. An algorithm has been developed, which automates this quantification of grain orientation with a success rate of ϳ90% on ͕001͖ and ͕110͖-type grains.Over the past 20 years, the manufacturing output of solar cells has grown by a factor of 200. 1 Presently, ϳ90% of solar cells are produced from silicon; 2 around half of these from multicrystalline silicon ͑mc-Si͒. 3 mc-Si is grown by directional solidification and, consequently, ingots of mc-Si have a columnar grain structure. Wafers from which solar cells are fabricated are cut normal to the growth direction and have grains typically of the order of a millimeter to a centimeter across.Efficiencies of mc-Si solar cells are usually a few percent lower than their single-crystal counterparts, which are mostly made from Czochralski silicon ͑CZ-Si͒. One reason for this difference is that the surface reflectance of mc-Si solar cells cannot be as easily reduced due to the difficulties in texturing a multigranular material effectively. 4 To optimize efficiency by reducing reflectance, it is therefore first necessary to understand the grain orientations of the mc-Si ingots produced. It may then be feasible to cast mc-Si with specific grain orientations. 5 Electron backscatter diffraction ͑EBSD͒ is commonly used to map grain orientations in mc-Si ͑see Ref. 6 for a review of the technique͒. However, this is a difficult technique to use in a manufacturing environment. This technique requires a scanning electron microscope and the microscope's chamber size places restrictions on the size and shape of samples that can be tested. Additionally, the requirement to perform experiments under vacuum limits throughput. The development of a faster, cheaper technique, which gives maps of grain orientations, is the motivation for the work presented in this paper.Techniques relying on optical reflections from textured surfaces have long been known to provide orientation information for silicon crystals. In 1956 Hancock and Edelman developed a reflectographic technique that provided orientation information ...

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