Estimation of pattern resolution using NaCl high-contrast developer by Monte Carlo simulation of electron beam lithography

• We put forward a new development model for calculating resist profile.
• The solubility rate reveals the development behavior of resist.
• 2.3 wt.% TMAH/4 wt.% NaCl developer with high contrast (γ = 8.1) is suitable for sub-10 nm patterning.
• High contrast developer can form very fine pattern with high resolution.
• The simulation results are in good agreement with experiments.

The influences of different concentrations of NaCl in tetramethyl ammonium hydroxide (TMAH) developer on the electron beam lithography resolution of hydrogen silsesquioxane (HSQ) resist were studied, using original development model based on the three-dimensional (3D) energy deposition distributions (EDDs) and the experimental developing behaviors. The development behaviors of HSQ resist developed in 2.3 wt.% TMAH, 2.3 wt.% TMAH with 2 wt.% NaCl and 2.3 wt.% TMAH with 4 wt.% NaCl developer were measured, respectively, to provide the solubility rates at different exposure dosages for the simulation. On the basis of the solubility rates and 3D-EDDs, the optimal EDD regions were determined for achieving sharp nanodot patterns. The optimal resist profiles of the three different developers were compared, showing that the 2.3 wt.% TMAH with 4 wt.% NaCl developer is suitable to form 7-nm-sized, 15-nm-pitched nanodots with sufficient height. The simulations were demonstrated to be useful for estimating the pattern resolutions with different solubility rates of developers, especially for sub-10 nm nanodot fabrication.

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