| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系 === 98 ===
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nitric acid is lower than 40% in volume, porous etching occurs. The transition
between porous formation and polishing etching occurs when nitric acid content is
lager than 40%. Pore size distributes uniform on the surface of wafer. Stain etching
also provides the rough surface. After etching in the proper etchant solution, the
reflectance of the bare wafer was reduced to 0%. We have also successfully formed
porous layer in large size (7.5x7.5cm) Si (100) which has lower reflectance
compared with conventional AR PECVD-Si3N4, and SiO2 .We conclude that stain
etching porous silicon could be a promising replacement for the conventional AR
coatings.In this dissertation, we numerically study the reflectance of porous silicon
(PS) layer for antireflection applications. Based on the numerical study, we develop
chemical etchant (HF, HNO3, H2O) to form PS layer on crystalline silicon wafer.
As we all know, silicon nitride and silicon dioxide are well known antireflection
coating used in semiconductor industry. However, the deposition of silicon nitride
and silicon dioxide films increase the total cost of solar cell modules which is not
suitable for low-cost photovoltaic devices. In the other hand, the chemical etching
known as stain etching (SE) porous silicon is a cheap, simple and rapid technique
for texturing single-crystalline silicon. In addition, porous silicon shows the
remarkable low reflectance at visible light.
In this study, we have successfully fabricated porous silicon layer on top of
the Si (100) and Si (111) surfaces. We varied the proportion of the solution of nitric
acid, hydrofluoric acid and water to optimize the etching process. We found that
nitric acid plays a very important role in stain etching. When the proportion of the
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