Position measurement method for alignment in UV imprint using a high index mold and “electronic” moiré technique

Abstract

In UV imprint, positioning errors can occur between a mold and a wafer due to pressure when there is a contact with the UV resin. The moiré technique, which is produced by superimposition of two gratings, is a well-known and simple method for high-resolution position measurement. However, the authors believe that a direct observation of two separate gratings is more appropriate for higher positioning accuracy. Here they propose a new method for the position measurement, which obtains “electronic” moiré fringes by combining the images of two separate gratings from different areas of the mold and the wafer. The fundamental detection error was σ=0.15nm. The repeatabilities of the total system was σ=0.68nm in air and σ=0.73nm in resin. The linearity of the measurement value to control signal was R2=0.97.