In electron-beam (e-beam) lithography, electron scattering in the resist causes a written pattern to blur, known as proximity effect. The smaller the feature size is, the more outstanding the proximity effect becomes. Hence, without proximity effect correction, the minimum feature size achievable is severely limited in most nanoscale patterns. Two main issues in proximity effect correction are accuracy and speed.
An effective and efficient approach to proximity effect correction, named PYRAMID, which takes a hierarchical approach for generality and accuracy, employs look-up tables for fast correction, and does not require human interaction, was introduced two decades ago. Since then, the PYRAMID approach has been employed in various implementations, not only for proximity effect correction but also for nanofabrication of 2-D and 3-D structures.