In this paper, we will present a machine learning solution targeted for memory customers including both assist feature and main feature mask synthesis. In a previous paper, we demonstrated machine learning ILT solutions for the creation of assist features using a neural network. In this paper, we extend the solution to include main features masks, which we can create using machine learning models which take into account the full ILT corrected masks during training. In practice, while the correction of main features is often visually more intuitive, there are underlying edge to edge and polygon to polygon interactions that are not easily captured by local influence edge perturbations found in typical OPC solvers but can be captured by ILT and machine learning solutions trained on ILT masks.
Since its introduction at Luminescent Technologies and continued development at Synopsys, Inverse Lithography Technology (ILT) has delivered industry leading quality of results (QOR) for mask synthesis designs. With the advent of powerful, widely deployed, and user-friendly machine learning (ML) training techniques, we are now able to exploit the quality of ILT masks in a ML framework which has significant runtime benefits. In this paper we will describe our MLILT flow including training data selection and preparation, network architectures, training techniques, and analysis tools. Typically, ILT usage has been limited to smaller areas owing to concerns like runtime, solution consistency, and mask shape complexity. We will exhibit how machine learning can be used to overcome these challenges, thereby providing a pathway to extend ILT solution to full chip logic design. We will demonstrate the clear superiority of ML-ILT QOR over existing mask synthesis techniques, such as rule based placements, that have similar runtime performance.