23 October 2015 Wafer weak point detection based on aerial images or WLCD
Author Affiliations +
Abstract
Aerial image measurement is a key technique for model based optical proximity correction (OPC) verification. Actual aerial images obtained by AIMS (aerial image measurement system) or WLCD (wafer level critical dimension) can detect printed wafer weak point structures in advance of wafer exposure and defect inspection. Normally, the potential wafer weak points are determined based on optical rule check (ORC) simulation in advance. However, the correlation to real wafer weak points is often not perfect due to the contribution of mask three dimension (M3D) effects, actual mask errors, and scanner lens effects. If the design weak points can accurately be detected in advance, it will reduce the wafer fab cost and improve cycle time. WLCD or AIMS tools are able to measure the aerial images CD and bossung curve through focus window. However, it is difficult to detect the wafer weak point in advance without defining selection criteria.

In this study, wafer weak points sensitive to mask mean-to-nominal values are characterized for a process with very high MEEF (normally more than 4). Aerial image CD uses fixed threshold to detect the wafer weak points. By using WLCD through threshold and focus window, the efficiency of wafer weak point detection is also demonstrated. A novel method using contrast range evaluation is shown in the paper. Use of the slope of aerial images for more accurate detection of the wafer weak points using WLCD is also discussed. The contrast range can also be used to detect the wafer weak points in advance. Further, since the mean to nominal of the reticle contributes to the effective contrast range in a high MEEF area this work shows that control of the mask error is critical for high MEEF layers such as poly, active and metal layers. Wafer process based weak points that cannot be detected by wafer lithography CD or WLCD will be discussed.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Guoxiang Ning, Guoxiang Ning, Peter Philipp, Peter Philipp, Lloyd C. Litt, Lloyd C. Litt, Paul Ackmann, Paul Ackmann, Christian Crell, Christian Crell, Norman Chen, Norman Chen, } "Wafer weak point detection based on aerial images or WLCD", Proc. SPIE 9635, Photomask Technology 2015, 96351V (23 October 2015); doi: 10.1117/12.2197025; https://doi.org/10.1117/12.2197025
PROCEEDINGS
8 PAGES


SHARE
RELATED CONTENT

OPC hotspot identification challenges: ORC vs. PWQ on wafer
Proceedings of SPIE (October 16 2008)
Aerial image measuring system at 193 nm a tool...
Proceedings of SPIE (December 05 2004)
Impact of mask errors on full chip error budgets
Proceedings of SPIE (July 25 1999)
A Submicron Lithography Process Using Philips I-Line Stepper
Proceedings of SPIE (December 31 1987)
Some challenges for mask making to keep up with the...
Proceedings of SPIE (December 17 1998)

Back to Top