High resolution patterning – Preparation of VSB systems for 22 nm node capability

Abstract

Microelectronic technology inevitably continues to develop towards ever shrinking, smaller geometries. For the year 2016, minimum feature sizes requiring 22 nm half pitch (hp) patterning lithography are predicted. To keep abreast of this challenging development, Vistec’s latest variable shaped beam (VSB) column – already described elsewhere [1] – was applied and the electron energy level increased to 100 keV for exposure of such fine pattern dimensions. Based on the electron-optical simulations that were performed, resolving power can be forecast to improve by a factor of 1.4 compared to results reported earlier. This is what 22 nm hp exposure requires as a compulsory precondition. This paper discusses four types of resist to demonstrate the increase in resolution capability. These are: positive and negative tone resists, conventional resists and chemically amplified resists. To provide a sound evaluation, several test patterns containing single lines, groups of seven lines and spaces, as well as extensive line/space areas and contact arrays were exposed. Top-down SEM images and cross-sectional views were both taken into account for a final assessment. It turned out that only the conventional resists are able to deliver the resolution capability for hp 22 nm.