A substrate including an NMOS transistor region and a PMOS transistor region is prepared. A silicon-germanium layer is formed on the PMOS transistor region. Nitrogen atoms are injected in an upper portion of the silicon-germanium layer. A first gate dielectric layer is formed on the NMOS transistor region and the PMOS transistor region. The nitrogen atoms are injected into the upper portion of the silicon-germanium layer before forming the first gate dielectric layer.

Methods of fabricating semiconductor devices

High Resolution reticle inspection is well-established as a proven, effective, and efficient means of detecting yield-limiting
mask defects as well as defects which are not immediately yield-limiting yet can enable manufacturing process
improvements. Historically, RAPID products have enabled detection of both classes of these defects. The newly-developed
Wafer Plane Inspection (WPI) detector technology meets the needs of some advanced mask manufacturers to
identify the lithographically-significant defects while ignoring the other non-lithographically-significant defects. Wafer
Plane Inspection accomplishes this goal by performing defect detection based on a modeled image of how the mask
features would actually print in the photoresist. This has the effect of reducing sensitivity to non-printing defects while
enabling higher sensitivity focused in high MEEF areas where small reticle defects still yield significant printing defects
on wafers.
WPI is a new inspection mode that has been developed by KLA-Tencor and is currently under test with multiple
customers. It employs the same transmitted and reflected-light high-resolution images as the industry-standard high-resolution
inspections, but with much more sophisticated processing involved. A rigorous mask pattern recovery
algorithm is used to convert the transmitted and reflected light images into a modeled representation of the reticle.
Lithographic modeling of the scanner is then used to generate an aerial image of the mask. This is followed by resist
modeling to determine the exposure of the photoresist. The defect detectors are then applied on this photoresist plane so
that only printing defects are detected. Note that no hardware modifications to the inspection system are required to
enable this detector. The same tool will be able to perform both our standard High Resolution inspections and the Wafer
Plane Inspection detector.
This approach has several important features. The ability to ignore non-printing defects and to apply additional effective
sensitivity in high MEEF areas enables advanced node development. In addition, the modeling allows the inclusion of
important polarization effects that occur in the resist for high NA operation. This allows for the results to better match
wafer print results compared to alternate approaches. Finally, the simulation easily allows for the application of
arbitrary illumination profiles. With this approach, users of WPI can make use of unique or custom scanner illumination
profiles. This allows the more precise modeling of profiles without inspection system hardware modification or loss of
company intellectual property.
This paper examines WPI in Die:Die mode. Future work includes a review of Die:Database WPI capability.

A novel approach: high resolution inspection with wafer plane defect detection

According to the ITRS Roadmap, the EUV mask requirement for 2X nm technology node is detection of defect size of
20 nm. The history of optical mask inspection tools involves continuous efforts to realize higher resolution and higher
throughput. In terms of productivity, considering resolution, throughput and cost, we studied the capability of EUV light
inspection and Electron Beam (EB) inspection, using Scanning Electron Microscope (SEM), including prolongation of
the conventional optical inspection. As a result of our study, the solution we propose is EB inspection using Projection
Electron Microscope (PEM) technique and an image acquisition technique to acquire inspection images with Time Delay
Integration (TDI) sensor while the stage is continually moving. We have developed an EUV mask inspection tool,
EBeyeM, whole design concept includes these techniques. EBeyeM for 2X nm technology node has the following targets,
for inspection sensitivity, defects whose size is 20 nm must be detected and, for throughput, inspection time for particle
and pattern inspection mode must be less than 2 hours and 13 hours in 100 mm square, respectively. Performance of the
proto-type EBeyeM was reported. EBeyeM for 2X nm technology node was remodeled in light of the correlation
between Signal to Noise Ratio (SNR) and defect sensitivity for the proto-type EBeyeM. The principal remodeling points
were increase of the number of incident electrons to TDI sensor by increasing beam current for illuminating optics and
realization of smaller pixel size for imaging optics.
This report presents the performance of the remodeled EBeyeM (=EBeyeM for 2X nm) and compares it with that of the
proto-type EBeyeM. Performances of image quality, inspection sensitivity and throughput reveal that the EBeyeM for
2X nm is improved. The current performance of the EBeyeM for 2X nm is inspection sensitivity of 20 nm order for both
pattern and particle inspection mode, and throughput is 2 hours in 100 mm square for particle inspection mode.

Performance of EBeyeM for EUV mask inspection

It is generally said that conventional deep ultraviolet inspection tools have difficulty meeting the defect requirement for extreme ultraviolet masks of hp 1X nm. In previous studies, it has been shown that the newly developed optics and systems using deep ultraviolet, named Super Inspection Resolution Improvement method for UnreSolved pattern (SIRIUS), has high sensitivity for nanoimprint lithography templates with unresolved patterns which are the same scale as the wafer. In this paper, the capability of SIRIUS for the extreme ultraviolet mask of hp 1X nm lines and spaces pattern has been studied by evaluating the signal to noise ratio of inspection images and capture rates with 5 runs to the target defects which cause over 10% printed wafer critical dimension errors calculated by simulation. It was demonstrated that the signal to noise ratio was increased and the all target defects became detectable with the throughput of 120 min per 100 × 100 mm2 . Additionally, the printability of natural defects detected with SIRIUS was analyzed. It was confirmed that SIRIUS was able to detect natural defects under 10% of wafer critical dimension. In conclusion, we confirm that SIRIUS can be available for the extreme ultraviolet mask inspection of hp 1X nm lines and spaces pattern.

DUV inspection beyond optical resolution limit for EUV mask of hp 1X nm

High Resolution reticle inspection is well-established as a proven, effective, and efficient means of detecting yieldlimiting
mask defects as well as defects which are not immediately yield-limiting yet can enable manufacturing process
improvements. Historically, RAPID products have enabled detection of both classes of these defects. The newlydeveloped
Wafer Plane Inspection (WPI) detector technology meets the needs of some advanced mask manufacturers to
identify the lithographically-significant defects while ignoring the other non-lithographically-significant defects. Wafer
Plane Inspection accomplishes this goal by performing defect detection based on a modeled image of how the mask
features would actually print in the photoresist. This has the effect of reducing sensitivity to non-printing defects while
enabling higher sensitivity focused in high MEEF areas where small reticle defects still yield significant printing defects
on wafers.
This approach has several important features. The ability to ignore non-printing defects and to apply additional effective
sensitivity in high MEEF areas enables advanced node development. In addition, the modeling allows the inclusion of
important polarization effects that occur in the resist for high NA operation. This allows for the results to better match
wafer print results compared to alternate approaches. Finally, the simulation easily allows for the application of
arbitrary illumination profiles. With this approach, users of WPI can make use of unique or custom scanner illumination
profiles. This allows the more precise modeling of profiles without inspection system hardware modification or loss of
company intellectual property.
A previous paper [1] introduced WPI in D:D mode. This paper examines the operation and results for WPI in
Die:Database mode.

High resolution inspection with wafer plane die: database defect detection

Extreme Ultra Violet Lithography (EUVL) is one of the most advanced patterning technologies to overcome the critical
resolution limits of current ArF lithography for 30nm generation node and beyond. Since EUVL mask manufacturing
process has not been fully stabilized yet, it is still suffering from many defect issues such as blank defects, defects inside
multilayer causing phase defects, CD defects, LERs (Line Edge Roughness), and so on. One of the most important
roles in mask manufacturing process belongs to mask inspection tools, which monitor and visualize mask features,
defects and process quality for the EUVL process development. Moreover, as the portion of EUV mask production has
been increased due to the EUV Pre-Production Tool (PPT) development, mask inspection technologies for EUVL
become highly urgent and critical to guarantee mask quality. This paper presents a promising inspection technique for
increasing the contrast of pattern imaging and defects capture rate using configurable illumination conditions in 193nm
wavelength inspection tool.

Current status of EUV mask inspection using 193nm optical inspection system in 30nm node and beyond

As design rules continue to shrink towards 4x nm, there are increase usage of aggressive Optical Proximity Correction
(OPC) in reticle manufacturing. One of the most challenging aggressive OPCs is Sub Resolution Assist Feature (SRAF)
such as scattering and anti-scattering bars typically used to overlap isolated and dense feature process windows. These
SRAF features are sub-resolution in that these features intentionally do not resolve on the printed wafer. Many reticle
manufacturers struggle to write these SRAFs with consistent edge quality even the most advanced E-Beam writers and
processes due to resolution limitations. Consequently, this inconsistent writing gives reticle inspection
challenges. Large numbers of such nuisance defects can dominate the inspection and impose an extraordinarily high
burden on the operator reviewing these defects. One method to work around inconsistent assist feature edge quality or
line-end shortening is to adjust the mask inspection system so that there is a substantial sensitivity decrease in order to
achieve good inspectability, which then compromises the sensitivity for the defects on main geometries.
Modern defect inspection tools offer multiple modes of operation that can be effectively applied to optimize defect
sensitivity in the presence of SRAF feature variability. This paper presents the results of an evaluation of advance
inspection methods and modes such as die to database selective thinline desense, transmitted & reflected light
inspections, review system and die to die selective desense to increase inspectability and usable sensitivity using
challenging production and R&D masks.
Key learnings are discussed.

A pragmatic approach to high sensitivity defect inspection in the presence of mask process variability

In the ever-changing semi-conductor industry, new innovations and technical advances constantly bring new
challenges to fabs, mask-shops and vendors. One of such advances is an aggressive optical proximity
correction (OPC) method, sub-resolution assist features (SRAF). On one hand, SRAFs bring a leap forward
in resolution improvement during wafer printing; on the other hand they bring new challenges to many
processes in mask making. KLA-Tencor Corp. working together with Samsung Electronics Co. developed an
additional function to the current HiRes 1 detector to increase inspectability and usable sensitivity during the
inspection step of the mask making process. SRAFs bring an unique challenge to the mask inspection process,
which mask shops had not experienced before. SRAF by nature do not resolve on wafer and thus have a
higher tolerance in the CD (critical dimension) uniformity, edge roughness and pattern defects. 
This new function, Thin-Line De-sense (TLD), increase the inspectability and usable sensitivity by generating
different regions of sensitivity and thus will match the defect requirement on a particular photomask with
SRAFs better. The value of TLD was proven in a production setting with more than 30 masks inspected, and
resulted in higher sensitivity on main features and a sharp decrease in the amount of defects that needed to be
classified.

Improving inspectability with KLA-Tencor TeraScan thin line de-sense

In a method of inspecting a mask, an image of a first die in a corrected mask may be obtained. The corrected mask may be corrected using correction data that may include deformation factors related to an exposure process. The first image may be reversely corrected based on correction data. The reversely corrected first image may be compared with a reference image to determine whether the first die may be properly implemented or not.

Method of inspecting a mask and apparatus for performing the same

EUV lithography has been delayed due to well-known issues such as source power, debris, pellicle, etc. for high volume
manufacturing. For this reason, conventional optical lithography has been developed to cover more generations with
various kinds of Resolution Enhancement Techniques (RETs) and new process technology like Multiple Patterning
Technology (MPT). Presently, industry lithographers have been adopting two similar techniques of the computational
OPC scheme such as Inverse Lithography Technology (ILT) and Source Mask Optimization (SMO) [1]. Sub-20 nm node
masks including these technologies are very difficult to fabricate due to many small features which are near the limits of
mask patterning process. Therefore, these masks require the unseen level of difficulty for inspection. In other words,
from the viewpoint of mask inspection, it is very challenging to maintain maximum sensitivities on main features and
minimum detection rates on the Sub-Resolution Assist Features (SRAFs). This paper describes the proper technique as
the alternative solution to overcome these critical issues with Aerial Imaging (AI) inspection and High Resolution (HR)
imaging inspection.

Sang Hoon Han

Papers

Current status of EUV mask inspection using 193nm optical inspection system in 30nm node and beyond

A pragmatic approach to high sensitivity defect inspection in the presence of mask process variability

Improving inspectability with KLA-Tencor TeraScan thin line de-sense

Method of inspecting a mask and apparatus for performing the same

Study of high sensitivity DUV inspection for sub-20nm devices with complex OPCs