Reticle critical dimension uniformity (CDU) is one of the major sources of wafer CD variations which include both
inter-field variations and intra-field variations. Generally, wafer critical dimension (CD) measurement sample size interfield
is much less than intra-field. Intra-field CDU correction requires time-consumption of metrology. In order to
improve wafer intra-field CDU, several methods can be applied such as intra-field dose correction to improve wafer
intra-field CDU. Corrections can be based on CD(SEM) or aerial image metrology data from the reticle. Reticle CDU
and wafer CDU maps are based on scanning electron microscope (SEM) metrology, while reticle inspection intensity
mapping (NuFLare 6000) and wafer level critical dimension (WLCD) utilize aerial images or optical techniques. Reticle
inspecton tools such as those from KLA and NuFlare, offer the ability to collect optical measurement data to produce an
optical CDU map. WLCD of Zeiss has the advantage of using the same illumination condition as the scanner to measure
the aerial images or optical CD.
In this study, the intra-field wafer CDU map correlation between SEMs and aerial images are characterized. The layout
of metrology structures is very important for the correlation between wafer intra-field CDU, measured by SEM, and the
CDU determined by aerial images. The selection of metrology structures effects on the correlation to SEM CD to wafer
is also demonstrated. Both reticle CDU, intensity CDU and WLCD are candidates for intra-field wafer CDU
characterization and the advantages and limitations of each approach are discussed.
© (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Guoxiang Ning ; Peter Philipp ; Lloyd C. Litt ; Stefan Meusemann ; Thomas Thaler, et al.
Intra-field CDU map correlation between SEMs and aerial image characterization
", Proc. SPIE 9235, Photomask Technology 2014, 92350I (September 16, 2014); doi:10.1117/12.2066173; http://dx.doi.org/10.1117/12.2066173