Most leading-edge IC fabs continue to use direct reticle inspection for "early warning" detection of haze defects before
they print on wafers. This inspection strategy enables fabs to cost-effectively maintain the highest product yields
possible. As design rules advance from 45/40 nm nodes to 32/28 nm, mask pattern sizes continue to shrink while
increasing in pattern density. More layers are exposed on 193nm immersion scanners, and as a result, reticle requal
inspection requirements become more challenging in order to meet sensitivity and inspectibility performance.
In this paper, we examine some of the inspection challenges 32/28 nm logic mask designs present. New reticle requal
requirements created by aggressive SRAF and higher MEEF mask designs used at these nodes are first examined. A
new and improved inspection technology to support requal requirements at this level is introduced and tested. These
data are analyzed to evaluate the overall inspection capability and sensitivity of this new product designed to meet 32/28
nm foundry reticle requal needs for high-volume production in IC fabs.
This paper assesses the readiness of EUV masks for pilot line production. The printability
of well characterized reticle defects, with particular emphasis on those reticle defects that
cause electrical errors on wafer test chips, is investigated. The reticles are equipped with
test marks that are inspected in a die-to-die mode (using DUV inspection tool) and
reviewed (using a SEM tool), and which also comprise electrically testable patterns. The
reticles have three modules comprising features with 32 nm ground rules in 104 nm pitch,
22 nm ground rules with 80 nm pitch, and 16 nm ground rules with 56 nm pitch (on the
wafer scale). In order to determine whether specific defects originate from the substrate,
the multilayer film, the absorber stack, or from the patterning process, the reticles were
inspected after each fabrication step. Following fabrication, the reticles were used to print
wafers on a 0.25 NA full-field ASML EUV exposure tool. The printed wafers were
inspected with state of the art bright-field and Deep UV inspection tools. It is observed
that the printability of EUV mask defects down to a pitch of 56 nm shows a trend of
increased printability as the pitch of the printed pattern gets smaller - a well established
trend at larger pitches of 80 nm and 104 nm, respectively. The sensitivity of state-of-the-art
reticle inspection tools is greatly improved over that of the previous generation of
tools. There appears to be no apparent decline in the sensitivity of these state-of-the-art
reticle inspection tools for higher density (smaller) patterns on the mask, even down to
56nm pitch (1x). Preliminary results indicate that a blank defect density of the order of
0.25 defects/cm<sup>2</sup> can support very early learning on EUV pilot line production at the 16nm node.
Source Mask Optimization (SMO) describes the co-optimization of the illumination source and mask pattern in the
frequency domain. While some restrictions for manufacturable sources and masks are included in the process, the
resulting photomasks do not resemble the initial designs. Some common features of SMO masks are that the line edges
are heavily fragmented, the minimum design features are small and there is no one-to-one correspondence between
design and mask features. When it is not possible to link a single mask feature directly to its resist counterpart,
traditional concepts of mask defects no longer apply and photomask inspection emerges as a significant challenge. Aerial
Plane Inspection (API) is a lithographic inspection mode that moves the detection of defects to the lithographic plane.
They can be deployed to study the lithographic impact of SMO mask defects. This paper briefly reviews SMO and the
lithography inspection technologies and explores their applicability to 22nm designs by presenting SMO mask
inspection results. These results are compared to simulated wafer print expectations.
As optical lithography progresses towards 32nm node and beyond, shrinking feature size on photomasks and growing
database size provides new challenges for reticle manufacture and inspection. The new TeraScanXR extends the
inspection capability and sensitivity of the TeraScanHR to meet these challenges. TeraScanXR launches a new function
that can dynamically adjust defect sensitivities based on the image contrast (MEEF) -- applying higher sensitivity to
dense pattern regions, and lower sensitivity to sparse regions which are lithographically less significant. The defect
sensitivity of TeraScanXR for Die-to-Die (DD) and Die-to-Database (DDB) inspection mode is improved by 20-30%,
compared with TeraScanHR. In addition, a new capability is introduced to increase sensitivity specifically to long CD
defects. Without sacrificing the inspection performance, the new TeraScanXR boosts the inspection throughput by 35%-
75% (depending upon the inspection mode) and the dataprep speed by 6X, as well as the capability to process 0.5-1
Terabyte preps for DDB inspection.
A prototype die-to-database high-resolution reticle defect inspection system has been developed for 32nm and below
logic reticles, and 4X Half Pitch (HP) production and 3X HP development memory reticles. These nodes will use
predominantly 193nm immersion lithography (with some layers double patterned), although EUV may also be used.
Many different reticle types may be used for these generations including: binary (COG, EAPSM), simple tritone,
complex tritone, high transmission, dark field alternating (APSM), mask enhancer, CPL, and EUV. Finally, aggressive
model based OPC is typically used, which includes many small structures such as jogs, serifs, and SRAF (sub-resolution
assist features), accompanied by very small gaps between adjacent structures. The architecture and performance of the
prototype inspection system is described. This system is designed to inspect the aforementioned reticle types in die-todatabase
mode. Die-to-database inspection results are shown on standard programmed defect test reticles, as well as
advanced 32nm logic, and 4X HP and 3X HP memory reticles from industry sources. Direct comparisons with currentgeneration
inspection systems show measurable sensitivity improvement and a reduction in false detections.
KEYWORDS: Signal to noise ratio, Reticles, Defect detection, Detection and tracking algorithms, Spatial frequencies, Sensors, Image processing, Inspection, Modulation transfer functions, Line edge roughness
The new TeraScanXR reticle inspection system extends the capability of the previous TeraScanHR platform to advanced
32nm logic and 40nm Half Pitch (HP) memory technology nodes. The TeraScanXR has been designed to provide a
significant improvement in image quality, defect sensitivity and throughput relative to the HR platform. Defect
sensitivity is increased via a combination of improved Die-to-Die (D:D) and Die-to-Database (D:DB) algorithms, as well
as enhancements to the image auto-focus (IAF). Modifications to system optics and the introduction of a more powerful
image processing computer have enabled a ~2X faster inspection mode. In this paper, we describe the key features of the
TeraScanXR platform and present preliminary data that illustrate the capability of this tool. TeraScanHR tools currently
at customer sites are field-upgradeable to the TeraScanXR configuration.
Sub-resolution assist features (SRAF) are a common optical proximity correction method to preserve
main feature patterns upon imaging into a photoresist during the lithographic process. The presence
of SRAF can often reduce the inspectability and usable sensitivity in high resolution inspections of
these reticles. KLA-Tencor has developed an improved Thin-Line
De-sense capability for Die-to-Database inspections (dbTLD) on the TeraScanHR that addresses this challenge. The dbTLD
capability provides sensitivity control focused on SRAF, thus improving inspectability without compromising high sensitivity to main features. The key feature of the improved dbTLD capability is that it provides greater flexibility to effectively de-sense
non-critical defects on SRAF in variable sizes oriented at any angle and in variety of shapes including challenging L- and U-shaped structures. This paper will demonstrate the value of dbTLD on improving inspectability where aggressive SRAF structures exist. The selective application of sensitivity on main features and assist features is the key to improvement in database inspections without impacting throughput.
STARlight2+<sup>TM</sup> (SL2+) is a new high-resolution contamination inspection system based upon the KLA-Tencor
TerascanHR platform. Building upon the proven technology of STARlight<sup>TM</sup> (SL2), SL2+ uses transmitted and reflected
images to detect potentially yield-limiting contamination defects on photomasks for wafer fabs and mask shops. It
extends the contamination inspection capability to the 32nm logic/45nm Half Pitch (HP) technology nodes using the
newly developed 72nm pixel image resolution as well as a significantly improved rendering model in the algorithm. In
this paper, we present inspection results on a wide variety of photomasks, spanning the 32nm to 110nm technology
nodes, in the recently concluded period of Alpha tests on the SL2+ system. The test results show that the sensitivity and
the inspection capability of the new SL2+ system have been greatly improved. Such improvement enables wafer fabs
and mask shops to inspect and qualify photomasks for 32nm node development and 45nm node production.
The XMM-Newton observatory is collecting a tremendous amount of X-ray imaging spectroscopy data. To deal with this huge volume of data, we are investigating more efficient methods to classify astronomical sources based purely on their X-ray spectra, and to understand the fundamental physical mechanisms responsible for X-ray emission. Multivariate statistics and pattern classification techniques are powerful tools to provide insight into the spectral similarities between a given target and its neighbors in the same observation. With this goal, we are developing approaches to classification of X-ray CCD spectra obtained by the XMM EPIC CCD instruments. Although X-ray CCD spectra have low resolution, they can be obtained in batches, whereas a high resolution spectrum can be only generated by the XMM RGS spectrometer for the brightest sources. Furthermore, X-ray CCD spectra can yield the relationship, if any, between the target source and other sources in the same field. The initial results are demonstrated by using a field centered on V1647 Ori, a young star that has recently displayed an accretion-driven optical, infrared and X-ray outburst. We applied Principle Component Analysis (PCA) to reduce the data dimensionality and Independent Component Analysis (ICA) to separate the CCD spectra as independently as possible. Then the Hierarchical Clustering classification method was employed to discriminate between this eruptive young star and other pre-main sequence X-ray sources in the field.
One distributed restoration algorithm used to protect optical transport networks against network failures is proposed in the paper. The algorithm takes advantage of the existing IP protocols, and therefore it can restore the affected traffic in the distributed and efficiently manner. By carrying the wavelength availability information in protocol data unit, the algorithm can reserve the required capacities as well as search the restoration routing.