Spacer multi patterning process continues to be a key enabler of future design shrinks in DRAM and NAND process flows. Improving Critical Dimension Uniformity (CDU) for main features remains high priority for multi patterning technology and requires improved metrology and control solutions.

In this paper Spacer Patterning Technology is evaluated using an angle resolved scatterometry tool for both intra field control of the core CD after partition etch (S1) and interfield pitch-walking control after final etch (S1-S2). The intrafield measurements were done directly on device using dense sampling. The inter-field corrections were based on sparse full wafer measurements on biased OCD targets. The CDU improvement after partition-etch was verified by direct scatterometer and CD-SEM measurement on device. The final etch performance across wafer was verified with scatterometer on OCD target.

The scatterometer metrology in combination with the control strategy demonstrated a consistent CDU improvement of core (S1) intrafield CD after partition etch between 23-39% and 47-53% on interfield pitch-walking (S1-S2) after final etch. To confirm these improvements with CD-SEM, oversampling of more than 16 times is needed compared to scatterometer.

Based on the results it is concluded that scatterometry in combination with the evaluated metrology and control strategy in principle qualifies for a spacer process CDU control loop in a manufacturing environment.

Date Published: 8 March 2016
PDF: 11 pages
Proc. SPIE 9778, Metrology, Inspection, and Process Control for Microlithography XXX, 97782B (8 March 2016); doi: 10.1117/12.2219664

Published in SPIE Proceedings Vol. 9778:
Metrology, Inspection, and Process Control for Microlithography XXX
Martha I. Sanchez, Editor(s)