The prevailing industry opinion is that EUV Lithography (EUVL) will enter High Volume Manufacturing (HVM) in the
2015 – 2017 timeframe at the 16nm HP node. Every year the industry assesses the key risk factors for introducing EUVL
into HVM – blank and reticle defects are among the top items.
To reduce EUV blank and reticle defect levels, high sensitivity inspection is needed. To address this EUV inspection
need, KLA-Tencor first developed EUV blank inspection and EUV reticle inspection capability for their 193nm
wavelength reticle inspection system – the Teron 610 Series (2010). This system has become the industry standard for
22nm / 3xhp optical reticle HVM along with 14nm / 2xhp optical pilot production; it is further widely used for EUV
blank and reticle inspection in R and D.
To prepare for the upcoming 10nm / 1xhp generation, KLA-Tencor has developed the Teron 630 Series reticle inspection
system which includes many technical advances; these advances can be applied to both EUV and optical reticles. The
advanced capabilities are described in this paper with application to EUV die-to-database and die-to-die inspection for
currently available 14nm / 2xhp generation EUV reticles.
As 10nm / 1xhp generation optical and EUV reticles become available later in 2013, the system will be tested to identify
areas for further improvement with the goal to be ready for pilot lines in early 2015.
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/cm2 can support very early learning on EUV pilot line production at the 16nm node.
Photomask contamination inspections, whether performed at maskshops as an outgoing
inspection or at wafer fabs for incoming shipping and handling or progressive defect monitoring,
have been performed by KLA-Tencor STARlight systems for a number of design nodes.
STARlight has evolved since it first appeared on the 3xx generation of KLA-Tencor mask
inspection tools. It was improved with the TeraStar (also known as SLF) based tools with the
SL1 algorithm. SL2 first appeared on the TeraScan systems (also known as 5xx) and has been
widely adopted in both mask shops and wafer fabs.
Design rules continue to advance as do inspection challenges. Advances in computer processing
power have enabled more complex and powerful algorithms to be developed and applied to the
STARlight technology. The current generation of STARlight, which is known as SL2+,
implements improved modeling fidelity as well as a completely new paradigm to the existing
STARlight technology known as HiRes5, or simply "H5". H5 is integrated seamlessly within
SL2+ and provides die-to-die-like performance in both transmitted and reflected light, in addition
to the STARlight detection, in unit time. It achieves this by automatically identifying repeating
structures in both X and Y directions and applying image alignment and difference threshold.
A leading mask shop partnered with KLA-Tencor in order to evaluate SL2+ at its facility. SL2+
demonstrated a high level of sensitivity on all test reticles, with good inspectability on advanced
production reticles. High sensitivity settings were used for 45 nm HP and smaller design rule
masks and low false detections were achieved. H5 provided additional sensitivity on production
plates, demonstrating the ability to extend the use of SL2+ to cover 32 nm DR plate inspections.
This paper reports the findings and results of this evaluation.
Semiconductor device manufacturers have made technological advances in fabricating devices at 65nm and 45nm nodes. Technology is advancing towards 32nm node devices. Reticles at these device nodes are designed with tight critical dimension (CD) specifications and sub-resolution features. Inspection tools capable of detecting CD defects on the order of 20 nm are required to accommodate these device nodes. To meet this challenge, KLA-Tencor has developed a new "CD Detector" capability on the TeraScanHR reticle inspection tool that efficiently detects two-sided CD defects on reticles at the 45nm node and beyond. The CD Detector is available in both Die-to-Die (DD) and Die-to-Database (DB) inspection modes. This paper presents results of a CD Detector Beta evaluation on variety of advanced reticles in a production setting at Advanced Mask Technology Center (AMTC) in Germany. Inspection results will demonstrate improved sensitivity to two-sided CD defects and good inspectability, at inspection times similar to a standard HiRes inspection. Discussion will focus on enabling the highest sensitivity to CD defects at 72nm pixel inspections, which is suitable for advanced research and development studies, as well as improved sensitivity at 90nm pixel inspections for higher productivity.
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.