Nowadays, features with sizes smaller than 10 nm can be obtained with electron beam lithography. For such small structures, high exposure doses are required to stay away from the shot noise limit. We investigated the effect of high-dose electron exposure of silicon substrates and subsequent dry development by reactive ion etching. We found that silicon can be directly patterned at electron doses ranging from 0.05 to 3.06 C/cm2. The effect of backscattered electrons is seen as a halo around the patterns. In the given dose range, a gradual transition from positive tone low-dose to negative tone high-dose behavior is observed. It is demonstrated that the patterning is likely to be caused by structural changes of the silicon substrate, resulting in different etch rates in exposed and unexposed areas. X-ray photoelectron spectroscopy analysis has been applied to determine if the thickness of the native oxide in the irradiated areas is different from the thickness at a reference position not irradiated. Small but significant differences have been observed, the largest increase being 0.3 nm.
Isolated dots and lines with 6 nm width are written in 20-nm-thick hydrogen silsesquioxane (HSQ) layers on silicon substrates, using 100-keV electron beam lithography. The main factors that might limit the resolution, i.e., beam size, writing strategy, resist material, electron dose, and development process, are discussed. We demonstrate that, by adjusting the development process, a very high resolution can be obtained. We report the achievement of 7 nm lines at a 20-nm pitch written in a 10-nm-thick HSQ layer, using a potassium-hydroxide (KOH)-based developer instead of a classical tetra-methyl-ammonium hydroxide (TMAH) developer. This is the smallest pitch achieved to date using HSQ resist. We think that the resolution can be improved further, and is presently limited by either the beam diameter (which was not measured separately) or by the not-fully-optimized development process.
Isolated dots and lines with 6 nm width were written in 20 nm thick Hydrogen silsesquioxane (HSQ) layers on silicon
substrates, using 100 keV electron beam lithography. The main factors that might limit the resolution, i.e. beam size,
writing strategy, resist material, electron dose, development process, are discussed. We demonstrate that, by adjusting
the development process, a very high resolution can be obtained. We report the achievement of 7 nm lines at a 20 nm
pitch written in a 10 nm thick HSQ layer, using a KOH-based developer instead of a classical TMAH developer. This is
the smallest pitch achieved to date using HSQ resist. We think that the resolution can be improved further, and is
presently limited by either the beam diameter (which was not measured separately) or by the not fully optimized
development process.
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