<title>Application of top-down CD-SEM metrology in measuring and correlating profile with CD data in resist films with various thickness and sidewall profiles</title>

Abstract

To have a more complete and clear picture for resist characterization, a second metric is needed to supplement the traditional linewidth data. A fast and non-destructive metrology system is desired to provide resist profile information. Electron scan and SEM image correlation capability will provide this second metric to effectively select the correct and precise process window. Monitoring for high electron line scan correlation values allows one to maintain a sharp sidewall profile of photoresist while supporting high aspect ratios. This is ideal for magneto- resistive (MR) and inductive thin film recording head coil plating and many other mission-critical applications. An automated top-down CD-SEM technique, capable of acquiring and analyzing electron waveform profiles of resist lines in addition to the traditional linewidth values is reported here. These measurements were made using a KLA-Tencor 8100 CD SEM, taking advantage of its new Pattern Quality Confirmation (pQC) feature. Process engineer using pQC can correlate signal intensity and images against stored templates, and then output the correlation scores. The technique has been applied to silicon wafers coated with various AZ<SUP>R</SUP> photoresists, such as AZ<SUP>R</SUP> 3300, AZ<SUP>R</SUP>7200, AZ<SUP>R</SUP>7500, and AZ<SUP>R</SUP>7900, with thickness of 1 - 3 microns. Wafers were exposed using a Nikon I line stepper and then developed by AZ<SUP>R</SUP> 300 metal ion free developer. Focus-Exposure dose-array fields were measured to investigate their profiles transformation as well as CD through and beyond their exposure latitude. Correlation scores were derived using aspect ratio of film thickness vs. CD size in each resist family. The study was extended by inspecting 'image correlation' values of high aspect ratio Contact Holes. Possibility of automating determination of open versus closed Contact Holes printed in these photoresists is also discussed. The goal of this study is to optimize determination of acceptable process window, by utilizing line and image correlation to compliment CD data.