Sub-10Nanometer Feature Size in Silicon Using ThermalScanning Probe Lithography

摘要

High-resolution lithography often involves thin resist layers which pose a challenge for pattern characterization. Direct evidence that the pattern was well-defined and can be used for device fabrication is provided if a successful pattern transfer is demonstrated. In the case of thermal scanning probe lithography (t-SPL), highest resolutions are achieved for shallow patterns. In this work, we study the transfer reliability and the achievable resolution as a function of applied temperature and force. Pattern transfer was reliable if a pattern depth of more than 3 nm was reached and the walls between the patterned lines were slightly elevated. Using this geometry as a benchmark, we studied the formation of 10–20 nm half-pitch dense lines as a function of the applied force and temperature. We found that the best pattern geometry is obtained at a heater temperature of ∼600 °C, which is below or close to the transition from mechanical indentation to thermal evaporation. At this temperature, there still is considerable plastic deformation of the resist, which leads toa reduction of the pattern depth at tight pitch and therefore limitsthe achievable resolution. By optimizing patterning conditions, weachieved 11 nm half-pitch dense lines in the HM8006 transfer layerand 14 nm half-pitch dense lines and L-lines in silicon. For the 14nm half-pitch lines in silicon, we measured a line edge roughnessof 2.6 nm (3σ) and a feature size of the patterned walls of7 nm.