In recent years, layer-to-layer overlay methods moved from the linear regime into non-linear high-order methods in order
to meet the shrinking overlay requirements. In this study we investigate a large number of metrology structures in the
overlapped scribe-line between adjacent scanner fields and the opportunity for improved overlay performance. Sampling
and modeling considerations are discussed. In this investigation we consider the opportunities for high-order stitching
analysis in process control and scanner monitoring. The goal of this work is to establish a systematic methodology for
high order stitching to characterize and reduce overlay errors for advanced IC manufacturing.
The minimum design rule of device patterns for LSI implant layers has been shrinking constantly according to the
industry requirements. Wavelength has been shortened and numerical aperture (NA) of the scanner has been enlarged to
catch up with the required shrinkage. Implant layers are unique because the resist is nearly always used without an
antireflective coating, and as a result, the resist is in direct contact with a multitude of substrate materials. In implant
applications, the wafer topography sacrifices some of the lithographic performance in order to obtain adequate features
on both top and bottom of the topography. KrF lithography has applied to most of the ion implant levels at today's
To solve the several issues in ion implant process, New KrF resist was designed specifically for the lithographic /
implantation process requirements.
According to the ITRS roadmap, low k1 imaging requires extremely tight control
of Critical Dimension (CD). Maintaining the same performance from one exposure to
another for new imaging requirements has become increasingly important, particularly
for matching dry and wet systems. Tool to tool CD matching depends on many factors,
for example, lens aberrations, partial coherence, laser spectral bandwidth and short range
We have performed a detailed study of laser bandwidth effects on tool CD matching for
typical 65nm node structures exposed on immersion ArF scanners. A high accuracy
on-board spectrometer was used to characterize the lithography
Laser bandwidth, allowing measurements of both the FWHM and E95 parameters of the
laser spectrum. Spectral bandwidth was adjusted over a larger range than normally
experienced during wafer exposures using Cymer's Tunable Advanced Bandwidth
Stabilization device (T-ABS) to provide controlled changes in bandwidth while
maintaining all other laser performance parameters within specification.
Measurements of both Lines and Contact Holes on 65nm node structures through all
pitches were made and correlated with bandwidth to determine the sensitivity of IDB and
C/H to bandwidth variation. We demonstrated that bandwidth can be adjusted for CD
matching on different tool using the T-ABS function.