Effect of Acid Generator Decomposition during Exposure on Acid Image Quality of Chemically Amplified Extreme Ultraviolet Resists

In chemically amplified extreme ultraviolet (EUV) resists, acid generators are mainly sensitized through the reaction with thermalized electrons. The resolution blur (the migration range of thermalized electrons) and quantum efficiency depend on the acid generator concentration. Therefore, the decomposition of acid generators during exposure affects both resolution blur and quantum efficiency. In this study, the effect of acid generator decomposition on the acid image quality was investigated by Monte Carlo simulation. It was found that the degradation of acid image contrast caused by acid generator decomposition increases with a reduction in feature sizes. Independently of the contrast in the EUV aerial image, the acid image contrast was similarly degraded with the increase of exposure dose. The effect of flare on the additional contrast degradation caused by acid generator decomposition during exposure was also estimated. For the suppression of this flare effect, it is important to increase the acid generator concentration.