Numerical analysis for resist profile after thermal process in display manufacturing

Abstract

The screen size growth of mobile displays is accompanied with the drastically increased resolution. A display should have high pixel resolution to meet demanding readability and legibility expectations. The manufacturing process should be advanced to meet final device requirements. One of the important process steps is the post-development hardbake, where resist reflow is used to tune the final profile which influences subsequent process steps. Moreover, 3D resist profiles become one of critical design factors for mechanical and optical properties of display pixels. The resist reflow is the main time-and temperature-dependent effect of post-development bake process step. Since the resist is in transitional state (crystalline glassy/amorphous rubbery/viscous melt) the resist profile dynamics are very complex and predictive modeling is necessary. The model presented in this paper is based on a lattice-Boltzmann method, where the resist is considered as multicomponent (polymer-solvent) and multiphase (solid-liquid-vapor) mixture. Simulated resist profile dynamics with time are analyzed in dependency of material parameters (solvent diffusivity and evaporation rate, polymer solid fraction and adhesion with substrate). Temperature-dependent parameter descriptions are used for model calibration. Validation against experimental data shows good model consistency and predictability, demonstrating the benefit of simulation in process development and optimization.