Advancements to the critical ionization dissolution model

Abstract

Polymer structure effect on dissolution characteristics and acid diffusion in chemically amplified deep ultraviolet resists J.The microlithographic process is dependent upon the dissolution of acidic polymers in aqueous base. The fundamental mechanism that governs the dissolution of these polymers has been the subject of considerable discussion, and a number of theories have been proposed to explain this behavior. Our research group has presented the critical ionization ͑CI͒ dissolution model to explain the dissolution of phenolic polymers in aqueous base. Specifically, the model proposes that a minimum or critical fraction of ionized sites, f crit , on a given polymer chain must be ionized in order for that chain to dissolve. The main input parameters to this model are the critical fraction of ionized sites, f crit , and the fraction of ionized surface sites, ␣. In this work methods are established for measuring these parameters. A quantitative link between the CI model and experiment has been demonstrated for the dissolution rate and surface roughness dependence on polymer molecular weight. Methods for calculating ␣ are discussed, including a new method that considers the formation of an electrostatic double layer at the resist-developer interface.

Monte Carlo study of surface and line-width roughness of resist film surfaces during dissolution

“…The analysis presented in this article adopts the critical ionization model [6][7][8][9], which is dependent on the reaction of ionized to protonated phenolic hydroxyl sites on the surface of the film. The dissolution process is visualized as a layer-by-layer 'etching' of the phenolic sites on the surface of the hydroxide ions.…”

“…On the other hand, there are quite a few models that successfully describe certain types of polymer-solvent interactions. Some types of polymer dissolution models are based on the concept of gel layer [15], percolation [16,17], reptation [18] critical ionization [6][7][8][9], and aggregation extraction [3]. All these use a probabilistic consideration of the dissolution process.…”

“…These species, during post-exposure bake can diffuse around the polymer film and create deprotection sites, i.e., they subtract the dissolution inhibiting chemical group, rendering the material more soluble. The critical ionization model was utilized in order to simulate the dissolution process [6][7][8][9].…”

Polymer dissolution model: an energy adaptation of the critical ionization theory

“…The Poisson-Boltzmann (PB) equation can be solved to yield the ion concentration at the charged surface. The following equilibrium reactions and equations are considered to capture the surface ionization phenomenon [10][11][12]:…”

Dissolution Rate Monitor Tool to Measure EUV Photoresist Dissolution

“…Less explored is the development process, playing an important role in roughness formation. Notably, the polymer molecular weight [7,8] and T g [9], or the choice of developer solution [10] have shown to impact the resist dissolution and as such the roughness of the remaining feature.…”