Overlay Accuracy Measurement Technique Using the Latent Image on a Chemically Amplified Resist

Abstract

An overlay accuracy measurement technique has been devised using the latent image on a chemically amplified resist developed in-house. A latent image with step height of over 0.1 µ m was formed after KrF excimer laser irradiation. It has been confirmed that it is possible to measure overlay accuracy using this latent image with measurement accuracy within 10 nm. This technique is very useful for overlay accuracy measurement of an exposure system using a double exposure method with a chemically amplified resist. It has been verified that heterodyne holographic wafer alignment (HHWA) has the capability to detect a latent image with shallow step height. Overlay accuracy within 60 nm was obtained using overlay error correction with this developed overlay accuracy measurement technique.