Assessment of contour modeling readiness for curvilinear masks

Abstract

Curvilinear pattern has been introduced as one of solutions for complex and challenging next generation lithography. However mask process correction (MPC) has been developed originally for Manhattan pattern. MPC now is using only orthogonal CD measurement information (so-called conventional modeling) which is not sufficient to represent all information needed to curvilinear pattern. In this reason a new solution for MPC is required for curvilinear pattern. Contour modeling is one of the known modeling techniques, which uses information of many vertices along pattern contour instead of orthogonal CD values. However contour modeling has not been evaluated yet in mass production level. As an evaluating procedure, we introduce a quality assurance (QA) method using virtual SEM contour. By adopting this QA method, we can analyze errors only from modeling itself separated from process induced errors. Moreover, aspect of error budget can be estimated by adding various errors on purpose. In this paper, we present the QA results of contour modeling and the comparison to the conventional modeling. Some discussion and future works will be followed.

Improvements on pattern fidelity at high curvature region of curvilinear mask with a novel method of MPC

“…MPC model was calibrated using extracted SEM contour coordinates, which is generally called contour modeling. It was shown that contour modeling contributes to improvement of model accuracy on curvilinear pattern [6]. Contour coordinates were extracted from denoised SEM image as points where gray level is equal to threshold (Figure 5…”

Novel method for precise curved EUV mask CD characterization by adopting machine learning

“…In addition, mask process correction (MPC) models for the curvilinear shape pattern are developed to mitigate mask process error prior to exposure. These models are develop in various ways, such as OPC model specialized for curvilinear pattern utilizing Bezier splines algorithm and contour-based modeling [4]. As the X or Y directional CD indicating the accuracy of the conventional pattern is insufficient to represent the precision of the curved pattern, so edge placement error (EPE) method is developed to verify the developed model (Figure 2).…”

“…The time, difficulty for patterning, and expense in writing and controlling these remain as barriers to the practicality of the curved pattern type [3]. In addition, since curvilinear patterns cannot be described only by X of Y critical dimension (CD) due to curvature, expressing it has emerged as one of the biggest challenges for the precision of patterning [4]. To enhance accuracy of the curved pattern, model which mitigates mask process error and has been interested and required.…”