Study of Proximity Effect in Projection based Micro Vat Photopolymerization Process

Abstract

Micro Projection-based Stereolithography (µPSL), also known as micro vat photopolymerization, is a promising technology that could revolutionize microfabrication by providing benefits similar to traditional lithography while reducing production time and cost. However, it faces a significant challenge in the form of the "proximity effect." This effect occurs when adjacent features are too close together, causing undesirable artifacts and limiting the achievable fabrication resolution. The proximity effect is caused by interactions between adjacent pixels of light and affects both the spatial and temporal domains of the fabrication process. Although researchers have been aware of this issue for some time, there has been little progress in understanding and addressing the proximity effect in micro vat photopolymerization. Existing models developed for laser-based systems can explain the effect to some extent, but they do not fully account for the impact of large area projection or explain how local threshold changes affect part size. This research aims to fill this knowledge gap by using in-situ observation systems to experimentally study the spatial and temporal proximity effects in single-shot vat photopolymerization microfabrication. We also investigate the role of oxygen in the proximity effect and lay the groundwork for better understanding how the effect impacts periodic structures with micronic inter-feature distances. In conclusion, while micro vat photopolymerization offers significant advantages over traditional lithography, the proximity effect remains a significant obstacle. This research represents an important step forward in addressing this challenge and improving the accuracy and resolution of vat photopolymerization in microfabrication.