KEYWORDS: Inspection, Data conversion, Data processing, Databases, Manufacturing, Explosives, Neodymium, Polonium, Photomask technology, Current controlled current source
Mask manufacturers are continuously challenged as a result of the explosive growth in mask pattern data volume.
This paper presents a new pipelined approach to mask data preparation for inspection that significantly reduces the
data preparation times compared to the conventional flows used today. The focus of this approach minimizes I/O
bottlenecks and allows for higher throughput on computer clusters. This solution is optimized for the industry
standard OASIS.MASK format.
These enhancements in the data processing flow, along with optimizations in the data preparation system
architecture, offer a more efficient and highly scalable solution for mask inspection data preparation.
Results from the recently available TeraScanHR reticle inspection system were published in early 2007. These
results showed excellent inspection capability for 45nm logic and 5xnm half-pitch memory advanced production
reticles, thus meeting the industry need for the mid-2007 start of production. The system has been in production use
since that time. In early 2007, some evidence was shown of capability to inspect reticles for 32nm logic and sub-50nm half-pitch memory, but the results were incomplete due to the limited availability of such reticles. However,
more of these advanced reticles have become available since that time. In this paper, inspection results of these
advanced reticles from various leading-edge reticle manufacturers using the TeraScanHR are shown. These results
indicate that the system has the capability to provide the needed inspection sensitivity for continued development
work to support the industry roadmap.
'Fast Integrated Die-to-Die T+R' pattern inspection (DDTR), reflected tritone database inspection (DBRt) and
STARlight2TM (SL2) contamination inspection are employed by mask makers in order to detect pattern defects and
contamination defects on photomasks for in process inspection steps.
In this paper we compare the detection capabilities of these modes on real production masks with a representative set of
contamination and pattern defects.
Currently, SL2 inspection is used to find contamination defects and die-to-die and die-to-database are used for pattern
defects. In this paper we will show that the new introduced 'Fast Integrated Die-to-Die T+R' pattern inspection
(DDTR)1 in combination with the DBRt can be used in production environment, instead of SL2 without any loss in the
sensitivity.
During the study, we collected and analyzed inspection data on critical layers such as lines & spaces and contact holes.
Besides, performance of the modes on product plates characterization was done using a test mask with programmed
defects.
Results from the recently available TeraScanHR reticle inspection system were published in early 2007. These
results showed excellent inspection capability for 45nm logic and 5xnm half-pitch memory advanced production
reticles, thus meeting the industry need for the mid-2007 start of production. The system has been in production use
since that time. In early 2007, some evidence was shown of capability to inspect reticles for the next nodes, 32nm
logic and sub-50nm half-pitch memory, but the results were incomplete due to the limited availability of such
reticles. However, more of these advanced reticles have become available since that time. Inspection results of
these advanced reticles from various leading edge reticle manufacturers using the TeraScanHR are shown. These
results indicate that the system has the capability to provide the needed inspection sensitivity for continued
development work to support the industry roadmap.
Transmitted Light (ddT or dbT) pattern inspection and STARlight-2TM (SL2) contamination inspection are widely
employed by mask makers in order to detect pattern and contamination defects on photomasks during the mask
inspection process. However, such an approach needs a two-pass inspection to detect pattern defects and contamination
defects separately.
In this paper we introduce the 'Fast Integrated T+R and SL2' capability and investigate the properties of this
combination of Transmitted (T) and Reflected (R) light inspection on die areas and STARlight-2TM(SL2) on scribe
areas. 'Fast Integrated T+R and SL2' has the capability to reduce a two-pass inspection to a single set-up and single
pass inspection resulting in a substantial saving of inspection time. In addition to a throughput enhancement, 'Fast
Integrated T+R and SL2' is able to compliment the pattern T inspection by providing additional sensitivity to detect
challenging defects.
During this study we collect and analyze inspection data on a critical layer provided by the Advanced Mask Technology
Center. Compared to the 2-pass individual mode pattern T and contamination SL2 inspections, a single scan 'Fast
Integrated T+R and SL2' demonstrates the capability to capture additional real defects, improves reticle inspectability
and first time success rate, and results in a significant enhancement in productivity.
Based on empirical data collected in this study, the Fast Integrated T+R and SL2 inspection is able to improve inspection
throughput approximately 45% at P90.
A new die-to-database high-resolution reticle defect inspection platform, TeraScanHR, has been developed for
advanced production use with the 45nm logic node, and extendable for development use with the 32nm node (also the
comparable memory nodes). These nodes will use predominantly ArF immersion lithography although EUV may also
be used. According to recent surveys, the predominant reticle types for the 45nm node are 6% simple tri-tone and COG.
Other advanced reticle types may also be used for these nodes including: dark field alternating, Mask Enhancer,
complex tri-tone, high transmission, CPL, etc. Finally, aggressive model based OPC will typically be used which will
include many small structures such as jogs, serifs, and SRAF (sub-resolution assist features) with accompanying very
small gaps between adjacent structures. The current generation of inspection systems is inadequate to meet these
requirements. The architecture and performance of the new TeraScanHR reticle inspection platform is described. This
new platform is designed to inspect the aforementioned reticle types in die-to-database and die-to-die modes using both
transmitted and reflected illumination. Recent results from field testing at two of the three beta sites are shown (Toppan
Printing in Japan and the Advanced Mask Technology Center in Germany). The results include applicable programmed
defect test reticles and advanced 45nm product reticles (also comparable memory reticles). The results show high
sensitivity and low false detections being achieved. The platform can also be configured for the current 65nm, 90nm,
and 130nm nodes.
Advanced wafer fabs are currently fabricating devices with 90nm and 65nm design rules using 193nm lithography. To meet the challenges at these sub-wavelength technology nodes, mask designers are using a variety of resolution enhancement techniques (RETs) in lithography which require new methods of processing, inspecting and qualifying photomasks. As a result, reticle inspection tools need to be capable of detecting smaller defects on ever tighter critical dimensions and background patterns that are considerably more complicated than before. To meet the challenges of current and future technology nodes, a variety of new inspection modes have been developed on the KLA-Tencor Deep UV TeraScan reticle inspection tool. These new inspection modes include Reflected light (Die-to-Die and Die-to-Database) modes, a Transmitted light Tritone (Die-to-Database) mode for inspecting Embedded Attenuated Phase Shift Masks (EAPSMs) with chrome in the inspection area, as well as a STARlight2 (SL2) mode for contamination detection. The SL2 inspection mode is the natural successor to the STARlight contamination detection algorithm on the previous generation of KLA-Tencor reticle inspection tools. Each of the inspection modes comes with its own set of inspectability and sensitivity capabilities and therefore the selection and/or optimization of a mode can depend upon a number of factors. In this paper we will present the inspection modes that are available on the TeraScan platform and discuss the appropriate use cases for each of the modes, based on reticle type and the intended objectives of the inspection.
Double Dipole Lithography (DDLä) has been demonstrated to be capable of patterning complex 2D devices patterns. [1,2,3] Due to inherently high aerial image contrast from dipole illumination, we have found that it can meet lithography manufacturing requirements, such as line edge roughness (LER), and critical dimension uniformity (CDU), for the upcoming 65nm node using ArF binary chrome masks. For patterning at k1 below 0.35, DDL is one of the promising resolution enhancement techniques (RET), which can offer process latitudes that are comparable to more costly alternatives such as two-exposure alternating PSM. To use DDL for printing actual IC devices, the original design data must be converted into a "vertical (V)" mask and a "horizontal (H)" mask for the respective X-dipole and Y-dipole exposures. We demonstrated that our model-based DDL mask data processing methodology is capable of converting complex 2D logic and memory designs into dipole-compatible mask layouts. [2,3] Due to the double exposure, stray light must be well controlled to ensure uniform printing across the entire chip. One intuitive solution to minimize stray light is to apply large patches of chrome in the open field areas in order to reduce the background (non-pattern area) exposure level. Unfortunately, this is not viable for a clear-field poly gate mask as it incorporates a positive photoresist process. We developed an innovative and practical background-shielding scheme called sub-resolution grating block (SGB), which is part of the DDL layout conversion method for full-chip application. This technique can effectively minimize the impact of long-range stray light on critical features during the two exposures. Reticles inspection is another important issue for the implementation of DDL technology. In this work, we reported a methodology on how to characterize defects and optimize inspection sensitivity for DDL RET reticles.
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