Implementation strategy of wafer-plane and aerial-plane inspection for advanced mask manufacture

Abstract

Inspection of aggressive Optical Proximity Correction (OPC) designs, improvement of usable sensitivity, and reduction of cost of ownership are the three major challenges for today's mask inspection methodologies. In this paper we will discuss using aerial-plane inspection and wafer-plane inspection as novel approaches to address these challenges for advanced reticles. Wafer-plane inspection (WPI) and aerial-plane inspection (API) are two lithographic inspection modes. This suite of new inspection modes is based on high resolution reflected and transmitted light images in the reticle plane. These images together with scanner parameters are used to generate the aerial plane image using either vector or scalar models. Then information about the resist is applied to complete construction of the wafer plane image. API reports defects based on intensity differences between test and reference images at the aerial plane, whereas WPI applies a resist model to the aerial image to enhance discrimination between printable and non-printable defects at the wafer plane. The combination of WPI and API along with the industry standard Reticle Plane Inspection (RPI) is designed to handle complex OPC features, improve usable sensitivity and reduce the cost of ownership. This paper will explore the application of aerial-plane and wafer-plane die-to-die inspections on advanced reticles. Inspection sensitivity, inspectability, and comparison with Aerial Imaging Measurement System (AIMSTM[1]) or wafer-print-line will be analyzed. Most importantly, the implementation strategy of a combination of WPI and API along with RPI leading-edge mask manufacturing will be discussed.