Variable shaped beam lithography capabilities enhancement by "small-shots" correction

Electron beam Mask Writers based on Variable Shaped Beam lithography (VSB) technology write designs with elementary fragments called shots. The electron dose assigned to each shot is usually defined by mean of a classical e-beam Proximity Effects Correction (PEC) model. However, this model reaches its limits in the case of shots of small size, typically below 50 nm due to machine imperfections. We developed a new "small-shots" model and a related calibration methodology. After calibration, small-shots corrections have been applied on layouts of different complexity using the INSCALE software from Aselta Nanographics. We experimentally demonstrate a 10-fold decrease of Edge Placement Errors (EPE) on photonics and Inverse Lithography Technology structures by using small-shot correction.