How to Design a Good Photoresist Solvent Package Using Solubility Parameters and High-Throughput Research

Understanding fundamental properties of photoresists and how interactions between photoresist components affect performance targets are crucial to the continued success of photoresists. More specifically, polymer solubility is critical to the overall performance capability of the photoresist formulation. While several theories describe polymer solvent solubility, the most common industrially applied method is Hansen's solubility parameters. Hansen's method, based on regular solution theory, describes a solute's ability to dissolve in a solvent or solvent blend using four physical properties determined experimentally through regression of solubility data in many known solvents. The four physical parameters are dispersion, polarity, hydrogen bonding, and radius of interaction. Using these parameters a relative cohesive energy difference (RED), which describes a polymer's likelihood to dissolve in a given solvent blend, may be calculated. Leveraging a high throughput workflow to prepare and analyze the thousands of samples necessary to calculate the Hansen's solubility parameters from many different methacrylate-based polymers, we compare the physical descriptors to reveal a large range of polarities and hydrogen bonding. Further, we find that Hansen's model correctly predicts the soluble/insoluble state of 3-component solvent blends where the dispersion, polar, hydrogen-bonding, and radius of interaction values were determined through regression of experimental values. These modeling capabilities have allowed for optimization of the photoresist solubility from initial blending through application providing valuable insights into the nature of photoresist.