Chemical reaction and diffusion kinetics during laser-induced submillisecond heating for lithographic applications

Abstract

Reactions in solid-state chemistry are controlled by both underlying chemical reaction rates and temperature-dependent diffusion of reactants and products. Due to distinctly different activation energies, the relative rates of reaction and diffusion may shift dramatically with temperature. In this work, the acid catalyzed deprotection of acid labile groups of model chemically amplified photopolymers was studied to understand the effects of temperature on diffusion-coupled reactions. In these systems, strong acids form during exposure of photoacid generators (PAGs) to ultraviolet radiation and then diffuse and catalyze deprotection reactions. By using very short duration laser-induced heating for the postexposure bake step, the potential reaction temperature range is extended by several hundred degrees compared to traditional thermal processing temperatures. Thermal degradation at these temperatures is avoided by simultaneously reducing the heating time from minutes to submilliseconds. Both diffusion and reaction rates were measured in this high temperature region for three different photoresists combined with two different PAGs, with activation energies of the key processes determined. The interplay of diffusion and reaction rates was also examined by comparing results of high-resolution pattern formation. The best image formation at high temperature was achieved using photoresists with high deprotection rates combined with PAGs exhibiting low diffusivity.

Selection approach of critical patterns for calibrating the physical resist model based on spectrum coverage

“…They are used in the calibration of rigorous resist models 40 – 42 The parameters utilized for calibrating the resist model in this paper are listed in Table 6.…”

A novel dual-tone molecular glass resist based on adamantane derivatives for electron beam lithography

“…It is attributed to the low thermal activation energy ( E a ) of the t -Boc group, and the AD-10Boc molecule can react with the EB-generated acid at room temperature. 45 The wide lithographic window of PEB processes is beneficial for practical applications in EBL. It should be noted that patterns with line widths of 30 nm were obtained in the 40 nm L/S layouts.…”

Predicting the critical features of the chemically-amplified resist profile based on machine learning

“…There are many photoresist models, some of them are rigorous models describing the physical and chemical processes in lithography, while some of them are empirical models fitting data by observation and experiment. For example, the reaction-diffusion model is a rigorous model introduced in simulating the reactant distribution in photoresist during the post exposure bake 1,2 (PEB), and the lumped parameter model is an empirical model introduced in simulating the photoresist profile 3,4,5 . However, the tradeoff between accuracy and efficiency of these models holds back their development in other fields, like optical proximity correction 6 (OPC) and source mask optimization 7 (SMO).…”