Defect review of advanced lithography processes is becoming more and more challenging as feature sizes decrease.
Previous studies using a defect review SEM on immersion lithography generated wafers have resulted in a defect
classification scheme which, among others, includes a category for micro-bridges. Micro-bridges are small connections
between two adjacent lines in photo-resist and are considered device killing defects. Micro-bridge rates also tend to
increase as feature sizes decrease, making them even more important for the next technology nodes.
Especially because micro-bridge defects can originate from different root causes, the need to further refine and split up
the classification of this type of defect into sub groups may become a necessity.
This paper focuses on finding the correlation of the different types of micro-bridge defects to a particular root cause
based on a full characterization and root cause analysis of this class of defects, by using advanced SEM review
capabilities like high quality imaging in very low FOV, Multi Perspective SEM Imaging (MPSI), tilted column and
rotated stage (Tilt&Rotation) imaging and Focused Ion Beam (FIB) cross sectioning.
Immersion lithography material has been mainly used to generate the set of data presented in this work even though, in
the last part of the results, some EUV lithography data will be presented as part of the continuing effort to extend the
micro-bridge defect characterization to the EUV technology on 40 nm technology node and beyond.
Double patterning is one of the enabling techniques to allow for further shrinking of
devices in the future. Many different solutions, like LELE (Litho-Etch-Litho-Etch) and
LPL (Litho-Process-Litho), have been investigated in the past years. In this paper a simplified - "Litho-Cluster-Only" - solution for double patterning is presented. This topcoat-less thermal freeze process has high capability of reaching 26 nm 1:1 LS. In addition it is shown that defect counts for the thermal freeze process approach defect numbers for high end immersion processes.
In a 2009 analysis of microbridging defectivity, a design of experiment methodology was used to show the effect of
filtration parameters on microbridging defectivity, specifically focusing on filter retention rating, filter media and design,
filtration rate, and controlled filtration pressure. In that analysis it was shown that different filter architectures provide
the most effective filtration of microbridging and that different filter architectures show different levels of microbridging
defects even when optimally tuned. Ultimately, filter choice and filtration setup matter in removal of microbridging
defects.
In the new analysis, a similar approach was taken with additional filter types. However, in the new study the retention rating of the filters was kept constant at 10nm while other filter parameters were varied, including membrane material and design. This study will show the specific effect of the membrane material and design on microbridging defectivity in addition to the effects of filtration setup.
The SOKUDO DUO track system incorporates a dual-path wafer flow to reduce the burden on the wafer handling unit
and enables high-throughput coat/develop/bake processing in-line with semiconductor photolithography exposure
(scanner) equipment. Various photolithography-based double patterning process flows were modeled on the SOKUDO
DUO system and it was confirmed to be able to process both Litho-Process-Litho-Etch (LPLE)*2 and negative-tone
develop process wafers at greater than 200 wafer-per-hour (wph) capability for each litho-pass through the in-line
exposure tool. In addition, it is demonstrated that Biased Hot Plates (BHP) with "cdTune" software improves litho
pattern #1 and litho pattern #2 within wafer CD uniformity. Based primarily on JSR Micro materials for Litho-Freeze-
Litho-Etch (LFLE) the coat, develop and bake process CD uniformity improvement results are demonstrated on the
SOKUDO RF3S immersion track in-line with ASML XT:1900Gi system at IMEC, Belgium.
Microbridging defects have emerged as one of the top yield detractor in semiconductor manufacturing as Moore's law
drives towards 32nm processing utilizing immersion lithography. It is generally recognized that there are multiple root
causes for microbridging defectivity. Image and resist contrast and different developer techniques have been studied and
their contribution to microbridging defectivity has been described. In this study we will focus on the effect of point-ofuse
filtration and how it is best used to mitigate microbridging defectivity.
A design of experiment methodology will be utilized to understand the effect of various filter and filtration parameters
on microbridging defectivity, including filter retention rating, filter media and design, filtration rate, and controlled
filtration pressure. It is anticipated that by better understanding the effect of point-of-use filtration on microbridging
defectivity, guidelines for better control of this type of defect may be formulated.
Given the increasingly stringent CD requirements for double patterning at the 32nm node and beyond the question arises
as to how best to correct for CD non-uniformity at litho and etch. For example, is it best to apply a dose correction over
the wafer while keeping the PEB plate as uniform as possible, or should the dose be kept constant and PEB CD tuning
used to correct. In this work we present experimental data, obtained on a state of the art ASML XT:1900Gi and Sokudo
RF3S cluster, on both of these approaches, as well as on a combined approach utilizing both PEB CD tuning and dose
correction.
Given the increasingly stringent CD requirements for double patterning at the 32nm node and beyond, the question arises
as to how best to correct for CD non-uniformity at litho and etch. For example, is it best to apply a dose correction over
the wafer while keeping the PEB plate as uniform as possible, or should the dose be kept constant and PEB plate tuning
used to correct. In this paper we present experimental data using both of these approaches, obtained on an ASML
XT:1900Gi and Sokudo RF3S cluster.
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