Progressive and haze defects continue to be the primary cause of mask degradation and
mask re-clean due mainly to intensified density of photon energy involved with ArF
exposure. To monitor and prevent haze in production, the methodology of direct reticle
inspection has been widely implemented in wafer fabs to provide early warning of haze
defects before they reach a critical level. With the continuous shrinkage of IC design rules
for scaling devices, reticle inspection systems are increasingly challenged by aggressive
OPC and high sensitivity requirements to detect printable defects. In this paper, two new
reticle inspection technologies: STARlight2+TM (SL2+) and Thin-line De-sense (TLD) on
Die-to-Die (D2D) mode have been studied and evaluated on ArF production test reticles.
The haze defect capture rate, defect residue modulation, and rendering on SL2+ mode
have been compared with STARlight2 (SL2); the false defect count and usable sensitivity
for D2D with TLD have been compared with D2D mode without TLD. The results of the
two new technologies revealed significant improvement on sensitivity, inspectability.
Single mode inspections, using die-to-die Transmitted (ddT) or die-to-die Reflected (ddR)
modes, provides a high level of sensitivity to opaque and clear defects on reticles. Die-to-die (DD)
inspections however, cannot inspect the scribes or frames which are potential locations for haze
growth. Historically, STARLight-2TM (SL2) has been the only mode effectively utilized for
contamination inspection in reticle scribes and frames. However, SL2 is designed for identifying
contamination and not pattern defects on a mask. The solution presented here is Fast Integrated
Inspection which includes ddT, ddR, and SL2, and allows the user to inspect a reticle for pattern and
contamination defects over patterned areas and scribes simultaneously, and in unit time.
This paper discusses the most efficient mask re-qualification inspection mode for 7Xnm
half pitch design node production memory reticles in advanced memory wafer fab. By
comparing overall performance including inspectability, sensitivity, and throughput for 8
different inspection modes, P150 Pixel Die-to-Die Reflected Light (P150 DDR) was
identified to be the most desirable inspection mode for the specific use case where only
one inspection mode is available. The evaluation was executed on the most critical
layers - active, gate and contact layer. P150 DDR demonstrates the capability of
providing early warning for the crystal growth type defects on both quartz and MoSi
surfaces. It also showed good sensitivity for capturing small contamination defects in the
dense Line/Space or Contact/Hole pattern areas. With a fast inspection scan speed and
easy to use set up, TeraScanHR P150 DDR offers the best cost of ownership among all
inspection modes. To gain higher sensitivity for smaller design nodes, TeraScanHR P150
DDR can be easily extended to smaller inspection pixels with minimum impact on
productivity.
For improving productivity and reducing manufacturing cost, it is critical for wafer fabs to reduce the frequency of
reticle re-clean and control the risk of missing defects of lithographic significance from overall haze defected. Haze
classification and haze behavior monitoring are highly time consuming processes. Many wafer fabs skip such operations
and instead re-clean reticles frequently in order to reduce the risk of missing killer haze defects. Such Reticle Re-Qual
rule leads to more than necessary reticle re-cleaning, shortening the life cycle of reticles and increasing the
manufacturing cost. In this paper, we investigate an efficient defect classification method - ReviewSmart, and defect
auto tracking method to classify defects and efficient tracking haze growth. A solution is discussed for wafer fabs to
monitor haze behaviors and improve Reticle Re-Qual rules for controlling and reducing manufacturing cost at lower risk.
A total of more then 30 production reticles of critical layers of OD, Poly, Contact and Metal 1 were inspected by
STARLight2TM on KLA-Tencor TeraScan SL516 system. ReviewSmart processed all the defects detected during Reticle
Re-Qual inspection. The results showed significant reduction in defect review times, with 100% fidelity rate.
In photomask production environments, increasing productivity of defect inspection and improving fidelity of defect
classification are important for mask makers to improve capacity of defect inspection tools and to enhance quality of
production. In particular, defect classification time corresponds directly to the cost and the cycle time of mask
manufacturing and new product development. KLA-Tencor has introduced an automatic defect grouping tool
"ReviewSmart" which automatically bins defects with high fidelity. ReviewSmart has been reported in engineering R&D
and evaluation. In this paper, we focus on implementation of ReviewSmart in photomask production. 592 plates
were processed during the evaluation period. Those plates are for products of logic, memory and flash. Technology
nodes are from 65nm to 180nm. With optimized production setting, the automatic defect grouping tool - ReviewSmart
improves productivity of defect inspection by 7% with 100% fidelity. In addition to improve productivity, ReviewSmart
is helpful to classify aggressive OPC caused nuisance, troubleshoot process issues and expedite product development and
improve usable inspection sensitivity as well.
Inspection strategies of transmitted die-to-database pattern inspection (DBT), reflected die-to-database inspection (DBR)
and STARlight2TM (SL2) contamination inspection are employed by mask makers in order to detect pattern defects and
contamination defects on photo-masks in process inspection steps and outgoing quality control (OQC). Currently, SL2
inspection is used to detect contamination defects while die-to-database inspections are used to detect pattern defects.
However, such inspection strategies need two passes to detect both pattern defects and contamination defects. In this
paper we introduce 'Fast Integrated Die-to-Database T+R' (Fast dbTR) and compare its detection capabilities and the
productivity to conventional standard detection modes, such as, DBT, DBR and SL2. Programmed reticles and
production reticles with pattern defects and contamination defects were used for comparative data collection.
During the study, we collected and analyzed inspection data on critical layers such as lines & spaces and contact holes.
Empirical data show that 'Fast dbTR' is able to cover the sensitivity required by DBT, DBR and SL2 to detect both
pattern defects and contamination defects in one single scan without any loss of productivity in production runs.
IC manufacturing fabs are experiencing mask reliability issues caused by progressive mask defects, such as crystal
growth, haze and etc. with the increase of the usage of DUV, especially 193nm lithography on 90nm technology node
and beyond. 193nm lithography has triggered an increasing demand for mask re-qualification in those manufacturing
fabs which process 90nm technology node wafers in mass production. Due to dramatic increase in re-qualification
demand, the capacity of mask inspection becomes constrain of the manufacturing output. In this paper authors
employed widely used KLA SLF inspection systems and investigated inspection scan modes (Fastscan mode and
Normal scan mode) and algorithms to optimize recipes on STARlight. Economically and practically, it is important for
wafer fabs to optimize mask inspection recipes and improve throughput in order to extend the capacity of mask
inspections without additional equipment investment. The Fastscan mode has the capability to move reticle stage as fast
as twice of the Normal scan mode in x-direction resulting in a substantial saving of inspection time. Even faster stage
move causes slightly reduction on the sampling of contamination defects, the overall defect inspection maintains the
same quality as the Normal scan mode in terms of early warning of mask re-qualification. During the study we collect
and analyze inspection data on two production masks and a standard test mask Orion5B. Based on empirical data
collected in the study, the Fastscan inspection mode is able to reduce inspection time approximately 28% to 38% at
P150.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.