Electron beam lithography developed resist profile improved by quality analysis

A numerical experiment of electron beam lithography (EBL) using the computer simulation tool SELID is presented and analysed. A layout of parallel lines with 0.3 μm width, situated 0.4 μm from each other, is obtained through exposure and development of the positive resist PMMA. Through a model-based approach an analysis of the influence of the exposure dose, the acceleration voltage and the resist thickness on: (i) the width of the developed resist profile, measured at the interface between the resist and the substrate, (ii) the measured width at a height of 5% of the initial resist thickness from the substrate, (iii) the average sidewall angle of the developed resist trench edge and (iv) the thickness loss of the developed resist in the non-irradiated areas is made. Concrete conclusions concerning the role of these factors are drawn. Optimisation is done using the quality criteria of obtaining developed resist profiles with parallel sidewalls. In order to find the parameter areas where the deviation from the target values of the performance characteristics above will be minimal in mass production two models, for the mean value and the variance, are proposed and estimated for tolerance limits of the factors of about 5%. The proposed approaches can be applied also with other simulation models, parameters and resists, as well as with real experimental EBL data.