Efficient exposure of non-Manhattan layouts using Vistec’s shaped beam systems

Abstract

In emerging optical applications, curvilinear features increase lithography complexity, which leads to long e-beam write times. Multi beam mask writers offer a solution for high-end masks where curvilinear features are predominant. For mid-range masks and emerging optical applications especially variable shaped beam systems still offer advantages. The challenge for optical applications is to expose large-scale non-Manhattan layouts such as slanted gratings, circle arrays, or curved geometrical structures with high fidelity in an efficient way. For arbitrary curved structures, including 3D, a novel shot count optimized and edge roughness aware approximation (JES-approximation) approach by ePLACE data preparation software package (Vistec Electron Beam GmbH, Germany) is applied. In contrast to common fracturing, both throughput and pattern fidelity in optical applications are highly increased. The optical quality by means of high sensitive haze measurements of diffractive axicons is proven. For repetitive structures such as slanted gratings or circle arrays the cell projection (CP) option is the solution of choice, but CP is also effective for arbitrarily curved gratings. Key enabler is the data preparation software ePLACE where cell dose values are calculated to meet the target layout contours precisely. Both JES-approximation as well as cell projection with target contour calculation are powerful tools for an efficient data preparation and final exposure of non-Manhattan layouts.