Using the aerial image measurement technique to speed up mask development for 193-nm immersion and polarization lithography

Abstract

The Aerial Image Measurement System (AIMS) for 193nm lithography emulation is established as a standard for the rapid prediction of wafer printability of critical features, such as dense patterns or contacts, defects or repairs on masks. The benefit of AIMS is to save expensive image qualification consisting of test wafer exposures followed by wafer SEM measurements. By adjustment of numerical aperture, illumination type and partial coherence to match the stepper or scanner, AIMS predicts the printability of any 193nm reticle like binary, OPC and PSM. The newly available 193nm 2nd generation AIMS fab systems are able to emulate numerical apertures (NA) up to 0.92 and provide a capability down to 65nm node regardless of the use of an immersion liquid or dry conditions. Rigorous simulation studies have been performed to study the matching of AIMS and scanner results at NA = 0.92 and to study the extension of the AIMS technique for immersion lithography emulation of hyper NA up to at least 1.4. Strong polarization effects depending on mask patterns and material as well as imaging effects will occur below the 65nm node. It will be shown that using the polarization capabilities of such a future immersion AIMS tool will provide a very suitable immersion lithography emulator. Together with low k1 values and polarization effects, 193nm mask design and manufacturing will face increased challenges for design and OPC placement at the 65nm node and below. Aerial image measurements of test masks using AIMS will then be crucial to speed up mask development. We propose to measure reticles on critical points as defined by simulation or areas of concern for manufacture with the AIMS system to analyze defect printability and mask manufacturability.