Heavily‐branched macropore and single‐trench fabrication via breakdown mechanism

Abstract

Usually, etching of n‐type silicon in the dark produces “break down” mesopores. In this letter, by etching with aqueous and strong oxidizing electrolytes respectively, heavily branched macropores with diameters up to 4 μm and depths up to 200 μm were produced without illumination on low doped n‐type silicon. Isolated silicon islands were obtained due to the interconnection of the main pores. The heavily branched macropores on the micron scale could be filled with smooth macropores with diameters up to 500 nm. Due to a small primary length scale no more than 250 nm in their rather short nucleation phases, the main pores should be secondary macropores. Based on these findings, a single trench with long branches, which might facilitate potential applications, was fabricated with prestructured linear nuclei. Current‐burst‐model combined with breakdown mechanism was finally found to be responsible for the formation of heavily‐branched macropores. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Formation of deep periodic trenches in photo-electrochemical etching of n-type silicon

“…Analysis of this effect requires a special study. Here, it should only be noted that the 'diagonal' pores we observed are similar to the so-called breakdown pores, which appear on etching ntype Si at a high voltage without illumination [5,6,20], or to pores formed in photo-electrochemical etching in the region of the geometrical shadow near the boundary of the porous region (figure 13). It is noteworthy that both these cases correspond to pore formation under deficiency of holes, which are either generated as a result of breakdown in the space-charge region of silicon, or diffuse from the illuminated part of a sample to its dark part.…”

“…The length of the seed grooves was 400 μm for photomasks T4k and T4d, and 500 μm for photomask T5. The distance i between the grooves in the longitudinal direction was the same (20 μm) for masks T4k and T4d, and variable (10,15,20,25 and 75 μm) for mask T5. After the anisotropic etching of seed grooves, the oxide was removed and the wafer was cut into 23 × 23 or 30 × 30 mm 2 samples, each having four zones with different periods.…”

Влияние перекиси водорода на фотоанодирование n-Si в режиме пробоя

“…Из рис. 4 и 6 видно, что для электролита на основе перекиси водорода при E = 0 пористая структура типична для той, что обычно наблюдается для пробоя в темноте [3,5,[11][12][13]. Она состоит из основных пор, которые представляют собой тонкие вертикальные каналы, заостренные книзу, и вторичных пор меньшего диаметра, распространяющиеся в горизонтальной плоскости.…”

“…Перекись водорода используется как окислитель в составе фторсодержащего раствора при получении пор бестоковым методом в присутствии катализаторов из благородных металлов (metal assisted electrochemical etching MECE) [7] и для приготовления пористого кремния с использованием внутреннего источника тока [8]. До недавнего времени влияние окислителей на процесс электрохимического растворения n-Si изучался только при отсутствии освещения [9][10][11][12][13][14][15]. Анодирование при освещении в электролите, содержащем H 2 O 2 , стало исследоваться в работах группы Barillaro [6,16,17].…”