Nanoimprint lithography (NIL) is one of the highest potential candidates for next generation lithography (NGL) in semiconductors. NIL is very useful technology for pattern fabrication in high resolutions and low costs compared to conventional optical lithography. NIL technology makes use of replication from quartz templates. The cross-sectional profile of the template is directly transferred to the resist profile on a wafer. In relationship to that, the management of the cross-sectional profile on the template pattern is much more important than that of photomask. In our past reports, we had studied the performance of measuring cross-sectional profiles using grazing-incidence small-angle X-ray scattering (GISAXS). GISAXS has made it possible to analyze the repeated nanostructure patterns with a 2D X-ray scattering pattern. After much research, we have found the application is very effective using the method of cross-sectional profiling in sub-20 nm half-pitch lines-and-spaces (LS) patterns and additionally in hole patterns. However, regarding the measurement for hole patterns, around a few hours are needed to get one result. We have considered new method for measuring cross-sectional profiles of hole patterns with GISAXS to improve the measurement throughput. We propose the new method to combine GISAXS with SEM images for measuring crosssectional profiles of hole patterns. Using this new method, measurement throughput is achieved less than one hour while almost the same accuracy as the conventional method. We report the results of the cross-sectional profile measurement of hole patterns with new method in comparison to conventional method.
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 mm<sup>2</sup> . 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.
Recently, much attention has been paid on nanoimprint lithography (NIL) because of its capability for fabricating device
at a low cost without multiple patterning. It is considered as a candidate for next generation lithography technology. NIL
is one to one lithography and contact transfer technique using template. Therefore, the lithography performance depends
greatly on the quality of the template pattern. And there are some challenges to be solved for defect repair of template
because pattern size of template is as same as that of wafer.
In order to realize the defect repair of template using electron beam (EB) repair tools, it is necessary to control the EB
irradiated area and dose amount of EB repair process more accurately. By optimizing these conditions, EB repair process
for template has been improved.
In this paper, we evaluated etching repair of a master template and the imprinting to replica. Programmed missing defects
on master template were repaired by changing parameters of EB repair tool. It was confirmed that the relationship of
critical dimension (CD) and depth of etching repair process for master template and the influence on replica imprinting.
As a result, the repair process for master template with hole pattern enables the corresponding CD error of the replica
template to be less than ±10% of the target CD.
We summarize the metrology and inspection required for the development of nanoimprint lithography (NIL), which is recognized as a candidate for next-generation lithography. Template inspection and residual layer thickness (RLT) metrology are discussed. An optical-based inspection tool for replica template inspection showed sensitivity for defects below 10 nm with sufficient throughput. For the RLT control, in-die RLT metrology is needed. Because the metrology requires dense sampling, optical scatterometry is the best solution owing to its ability to measure profile features nondestructively with high throughput. For in-die metrology, we have developed a new hybrid metrology that can combine key information from these complex geometries with scatterometry measurements to reduce the impact on the RLT measurement due to the layers beneath the resist. The technologies discussed here will be important when NIL is applied for IC manufacturing, as well as in the development phases of those lithography technologies.
Mask inspection tool with DUV laser source has been used for Photo-mask production in many years due to its high sensitivity, high throughput, and good CoO. Due to the advance of NGL technology such as EUVL and Nano-imprint lithography (NIL), there is a demand for extending inspection capability for DUV mask inspection tool for the minute pattern such as hp4xnm or less. But current DUV inspection tool has sensitivity constrain for the minute pattern since inspection optics has the resolution limit determined by the inspection wavelength and optics NA. <p> </p>Based on the unresolved pattern inspection capability study using DUV mask inspection tool NPI-7000 for 14nm/10nm technology nodes, we developed a new optical imaging method and tested its inspection capability for the minute pattern smaller than the optical resolution. We confirmed the excellent defect detection capability and the expendability of DUV optics inspection using the new inspection method. Here, the inspection result of unresolved hp26/20nm pattern obtained by NPI-7000 with the new inspection method is descried.
According to the road map shown in ITRS , the EUV mask requirement for defect inspection is to detect the defect
size of sub- 20 nm in the near future. EB (Electron Beam) inspection with high resolution is one of the promising
candidates to meet such severe defect inspection requirements. However, conventional EB inspection using the SEM
method has the problem of low throughput. Therefore, we have developed an EB inspection tool, named Model EBEYE
M※. The tool has the PEM (Projection Electron Microscope) technique and the image acquisition technique with TDI
(Time Delay Integration) sensor while moving the stage continuously to achieve high throughput .
In our previous study, we showed the performance of the tool applied for the half pitch (hp) 2X nm node in a production
phase for particle inspection on an EUV blank. In the study, the sensitivity of 20 nm with capture rate of 100 % and the
throughput of 1 hour per 100 mm square were achieved, which was higher than the conventional optical inspection tool
for EUV mask inspection -.
Such particle inspection is called for not only on the EUV blank but also on the patterned EUV mask. It is required after
defect repair and final cleaning for EUV mask fabrication. Moreover, it is useful as a particle monitoring tool between a
certain numbers of exposures for wafer fabrication because EUV pellicle has not been ready yet. However, since the
patterned EUV mask consists of 3D structure, it is more difficult than that on the EUV blank.
In this paper, we evaluated that the particle inspection on the EUV blank using the tool which was applied for the
patterned EUV mask. Moreover, the capability of the particle inspection on the patterned EUV mask for the hp 2X nm
node, whose target is 25 nm of the sensitivity, was confirmed. As a result, the inspection and SEM review results of the
patterned EUV masks revealed that the sensitivity of the hp 100 nm Line/Space (LS) was 25 nm and that of the hp 140-
160 nm Contact Hole (CH) was 21 nm. Therefore, we confirmed that particle inspection on the patterned EUV mask
using Model EBEYE M could be available for the EUV mask of the hp 2X nm node. In the future, we will try to inspect
the production mask of the hp 2X nm node, and try to confirm the performance for the EUV mask of the hp 1X nm node.
Recently there has been a demand for high durability MoSi masks. There are some candidates for MoSi mask materials. They are preferable for both mask user and mask manufacture because they show not only high durability against exposure or cleaning process but also process compatibility in production line. They are gaining momentum to practical application. However, there is a drawback for manufacturing regarding the mask repair process. Because ebeam repair employs pure chemical reaction, it faces severe etching difficulty due to higher chemical stability. Meanwhile, the tool supplier has looked into that chemical reaction in detail since the problem was unveiled. They developed a dedicated etching process for high durable materials. It’s so important for the mask manufacturer to evaluate this process properly before they transfer conventional MoSi to new high durability MoSi. A comprehensive understanding of this new process should be acquired by trying several kinds of etching tests. In this paper we will report the results ranging from basic etching rate, selectivity, repair accuracy to flexibility for complicated shaped defects. This data tells us a lot about if it can be applied for practical use. The experiment was performed with e-beam repair tool “MeRiT<sup>Ⓡ</sup>”, which was released as the latest version from ZEISS last year. An improved new etching process was applied to “A6L2” type high durable blanks provided by HOYA corporation. A wide variety of programmed defects were arranged on a line and space featured test mask. These programmed defects were repaired with the procedure developed by ZEISS. After repair, printed image was evaluated by AIMS<sup>TM</sup> system. This paper will discuss the initial results of these first steps into the uncharted territory of high durability MoSi repair.
For sub-10nm lithography for semiconductor devices, inspection technologies for detecting nanometer size defects become quite important. In the case of optical inspection, it is difficult to detect a defect whose size is less than 23nm because of optical resolution limit. This paper describes a cost-effective inspection technology for detecting a nanometer size defect with the optical inspection technology using replicated soft template which is able to enlarge a defect size by expanding. Feasibility of detecting 9.6nm defect with optical inspection is reported.
According to the ITRS Roadmap , within a few years the EUV mask requirement for defect will be detection of defect
size of less than 25 nm. Electron Beam (EB) inspection is one of the candidates to meet such a severe defect requirement.
EB inspection system, Model EBEYE M※1, has been developed for EUV mask inspection. Model EBEYE M employs
Projection Electron Microscope (PEM) technique and image acquisition technique to acquire image with Time Delay
Integration (TDI) sensor while the stage moves continuously . Therefore, Model EBEYE M has high performance in
terms of sensitivity, throughput and cost.
In a previous study, we showed the performance of Model EBEYE M for 2X nm in a development phase whose
sensitivity in pattern inspection was around 20 nm and in particle inspection was 20 nm with throughput of 2 hours in
100 mm square , . With regard to pattern inspection, Model EBEYE M for High Volume Manufacturing (HVM) is
currently under development in the production phase. With regard to particle inspection, Model EBEYE M for 2X nm is
currently progressing from the development phase to the production phase.
In this paper, the particle inspection performance of Model EBEYE M for 2X nm in the production phase was evaluated.
Capture rate and repeatability were used for evaluating productivity. The target set was 100% capture rate of 20 nm.
100% repeatability of 20 nm with 3 inspection runs was also set as a target. Moreover, throughput of 1 hour in 100 mm
square, which was higher than for Model EBEYE M for 2X nm in the development phase, was set as a target. To meet
these targets, electron optical conditions were optimized by evaluating the Signal-to-Noise Ratio (SNR). As a result,
SNR of 30 nm PSL was improved 2.5 times. And the capture rate of 20 nm was improved from 21% with throughput of
2 hours to 100% with throughput of 1 hour. Moreover, the repeatability of 20 nm with 3 inspection runs was 100% with
throughput of 1 hour. From these results, we confirmed that Model EBEYE M particle inspection mode could be
available for EUV mask production.
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.
Based on an acceptable wafer critical dimension (CD) variation that takes device performance into consideration, we
presented a methodology for deriving an acceptable mask defect size using defect printability -. The defect
printability is measurable by Aerial Image Measurement System (AIMS<sup>TM</sup>) and simulated by lithography simulation
without exposure. However, the defect printability of these tools is not always the same as the actual one. Therefore, the
accuracy of these tools is confirmed by fabricating the programmed defect mask and exposing this mask on wafer.
Advanced Binary Film (ABF) photomask has recently been studied as a substitute for the conventional MoSi phase shift
mask. For ABF photomask fabrication, mask performance for process and guarantee for mask defects by repair and
inspection are important. With regard to the mask performance, the ABF photomask has high performance in terms of
resolution of pattern making, placement accuracy, and cleaning durability . With regard to the guarantee for mask
defects, it has already been confirmed that the defect on the ABF photomask is repairable for both clear and opaque
defects. However, it has not been evaluated for inspection yet. Therefore, it is necessary to evaluate the defect
printability, to derive the acceptable mask defect size, and to confirm the sensitivity of mask inspection tool.
In this paper, the defect printability of the ABF photomask was investigated by the following process. Firstly, for opaque
and clear defects, sizes and locations were designed as parameters for memory cell patterns. Secondly, the ABF
programmed defect mask was fabricated and exposed. Thirdly, mask defect sizes on the ABF programmed defect mask
and line CD variations on the exposed wafer were measured with CD-SEM. Finally, the defect printability was evaluated
by comparing the correlation between the mask defect sizes and the wafer line CD variations with that of the AIMSTM
and the lithography simulation. From these results, the defect printability of AIMS<sup>TM</sup> was almost the same as the actual
one. On the other hand, the defect printability of the lithography simulation was relaxed from the actual one for the
isolated defect types for both clear and opaque defects, though the defect printability for the edge defect types was
almost the same. Additionally, the acceptable mask defect size based on the actual defect printability was derived and
the sensitivity of the mask inspection tool (NPI-7000) was evaluated. Consequently, the sensitivity of the NPI-7000 was
detectable for the derived acceptable mask defect size. Therefore, it was confirmed that the ABF photomask could be
guaranteed for mask defects.
Currently, repair machines used for advanced photomasks utilize principle method like as FIB, AFM, and EB. There
are specific characteristic respectively, thus they have an opportunity to be used in suitable situation. But when it comes
to EUV generation, pattern size is so small highly expected as under 80nm that higher image resolution and repair
accuracy is needed for its machines. Because FIB machine has intrinsic damage problem induced by Ga ion and AFM
machine has critical tip size issue, those machines are basically difficult to be applied for EUV generation.
Consequently, we focused on EB repair tool for research work.
EB repair tool has undergone practical milestone about MoSi based masks. We have applied same process which is
used for MoSi to EUV blank and confirmed its reaction. Then we found some severe problems which show
uncontrollable feature due to its enormously strong reaction between etching gas and absorber material. Though we
could etch opaque defect with conventional method and get the edge shaped straight by top-down SEM viewing, there
were problems like as sidewall undercut or local erosion depending on defect shape. In order to cope with these
problems, the tool vender has developed a new process and reported it through an international conference .
We have evaluated the new process mentioned above in detail. In this paper, we will bring the results of those
evaluations. Several experiments for repair accuracy, process stability, and other items have been done under estimation
of practical condition assuming diversified size and shape defects. A series of actual printability tests will be also
included. On the basis of these experiments, we consider the possibility of EB-repair application for 20nm pattern.
We are developing new electron beam inspection system, named EBeyeM, which features high speed and high
resolution inspection for EUV mask. Because EBeyeM has the projection electron microscope technique, the scan time
of EBeyeM is much faster than that of conventional SEM inspection system.
We developed prototype of EBeyeM. The aim of prototype system is to prove the concept of EBeyeM and to estimate
the specification of system for 2Xnm and 1Xnm EUV mask.
In this paper, we describe outline of EBeyeM and performance results of the prototype system. This system has two
inspection mode. One is particle inspection and the other is pattern defect inspection. As to the sensitivity of EBeyeM
prototype system, the development target is 30nm for the particle inspection mode and 50nm for pattern defect
inspection mode. The performance of this system was evaluated. We confirmed the particle inspection mode of the
prototype system could detect 30nm PSL(Polystyrene Latex) and the sensitivity was much higher than conventional
optical blank inspection system. And we confirmed that the pattern defect sensitivity of the prototype system was
around 45nm. It was recognized that both particle inspection mode and pattern defect inspection mode met the
development target. It was estimated by the performance results of the prototype system that the specification of
EBeyeM would be able to achieve for 2Xnm EUV mask. As to 1Xnm EUV mask, we are considering tool concept to
meet the specification.
Currently, repair technology is one of the key factors in mask making process regarding TAT reduction and yield level
enhancement. Since its commercial release EB repair tool has been commonly used for production line and contributed
to high quality repair. But it is not guaranteed whether those conventional machines can keep up with future pattern
reduction trend or not. In 2Xnm generation node some advanced exposure techniques seem to be adopted and that will
inevitably require higher specification of repair machine. A simple lithography simulation predicts 5nm of indispensable
repair accuracy for 2Xnm generation pattern. This number implies the necessity of upper class machine. Generally, the
error budget of EB repair tool is composed of three to four components, stated another way mechanical stability,
electrical (charging) uniformity, process stability, and graphical quality including software ability. If errors from those
components are reduced, overall repair accuracy could be better. A suggestion which can improve those errors was
issued last year from tool vender including new machine concept. We have conducted several kind of experiment in
order to confirm the performance of new machine. In this paper, we will report the result of experiment and consider
which part can effectively contribute to repair accuracy. And we have also evaluated its practical utility value for 2Xnm
node by verifying actual application of some 3Xnm production masks.
We obtained the acceptable mask defect size for both opaque and clear defects in the spacer patterning process using the
fail-bit-map analysis and a mask with programmed defects. The spacer patterning process consists of the development of
photoresist film, the etching of the core film using the photoresist pattern as the etching mask, the deposition of a spacer
film on both sides of the core film pattern, and the removal of the core film. The pattern pitch of the spacer film becomes
half that of the photoresist. Both the opaque defect and the clear defect of the mask resulted in a short defect in the spacer
pattern. From the fail-bit-map analysis, the acceptable mask defect size for opaque and clear defects was found to be
80nm and 120nm, respectively, which could be relaxed from that in ITRS2008. The difference of the acceptable mask
defect size for opaque and clear defects comes from the difference of the defect printability at the resist development.
In general photomask defect repair process flow, repaired portion is evaluated with AIMS<sup>TM</sup> and if AIMS<sup>TM</sup>'s result is out of
specification, the repaired portion must be re-repaired. With shrinking pattern on device, tighter specification is required.
Therefore re-repair cycle time increases and turn around time of defect repair process becomes much longer.
To solve this problem, we propose a noble evaluation method that enables us to judge without using AIMS<sup>TM</sup> with repair
tool images. Images of EB repair tool is available for our propose because EB repair tool dose not give any damage on
substrate and the resolution of image is quite high compared to other repair tools, FIB and Nanomachining tool. We made
lithography simulation and practical experiments with line & space pattern of ArFatt. PSM with programmed defects.
Consequently, we can predict AIMS-Results immediately after repair and there is a possibility to reduce the turn around
time of defect repair process.
We have studied both the mask CD specification and the mask defect specification for spacer patterning
technology (SPT). SPT has the possibility of extending optical lithography to below 40nm half-pitch devices. Since
SPT necessitates somewhat more complicated wafer process flow, the CD error and mask defect printability on wafers
involve more process factors compared with conventional single-exposure process (SEP). This feature of SPT implies
that it is very important to determine mask-related specifications for SPT in order to select high-end mask fabrication
strategies; those are for mask writing tools, mask process development, materials, inspection tools, and so on. Our
experimental studies reveal that both mask CD specification and mask defect specification are somehow relaxed from
those in ITRS2007. This is most likely because SPT reduces mask CD error enhanced factor (MEF) and the reduction
of line-width roughness (LWR).
We studied the mask defect printability for both opaque and clear defects in the spacer patterning process. The spacer
patterning process consists of the development of photoresist film, the etching of the core film using the photoresist
pattern as the etching mask, the deposition of a spacer film on both sides of the core film pattern, and the removal of the
core film. The pattern pitch of the spacer film becomes half that of the photoresist. The opaque defect and the clear
defect of the mask, respectively, resulted in an "open-short complex" defect and a short defect in the spacer pattern, The
defect size of both the opaque and clear defect became smaller as the process proceeded from the development to the
core film etching and the spacer pattern fabrication. The decrease of the mask defect printability during the spacer
process is likely to be related to the reduction of the line width roughness (LWR) and to the reduction of mask enhanced
factor (MEF). The acceptable mask defect size was also studied from the viewpoint of the defect printability to the
spacer pattern for both the opaque and clear defect, and found to be 55-60nm, which was relaxed from that in ITRS2007.
Although photomask defect repair tools based on FIB, AFM and pulsed laser are mainly used in current production
lines, there is a possibility they will not meet the requirements of 45nm generation photomasks. The EB repair tool is one
of the candidates that has a possibility of meeting those requirements. The EB repair tool, MeRiT-MG<sup>TM</sup>, has already
been announced by Carl Zeiss GmbH. The basic performance of this tool has been reported.<sup>1)</sup>
Recently MoSi mask is most commonly used in leading edge devices, and defects are mainly opaque type. For this
reason, the performance of EB-repair tool for MoSi etching should be investigated. In this paper, we will report the
evaluation results of MeRiT-MG<sup>TM</sup> and consider whether this tool has a possibility of meeting the requirements of 45nm
In order to evaluate the performance of MeRiT-MG<sup>TM</sup>, we prepared 180nm half pitch line & space pattern of ArFatt.
PSM with programmed defects. These programmed defects are not only simple extrusion shape but also of various
shapes and sizes. By using these defects, we made practical experiment which would happen in real production line.
An immersion microscope with high NA condenser lens is evaluated. The effects of high NA condenser lens are studied
with simulation and experiment. The one effect is CD linearity improvement. We have already reported that our
calibration method improves CD linearity of an immersion microscope. The simulation result indicates the high NA
condenser lens improves the accuracy of the calibration method. The other effect is CD repeatability. The experimental
result demonstrates the high NA condenser lens reduces the peak of intensity profile and improves CD repeatability. As
the result, an immersion microscope with high NA condenser lens is available for CD measurement of 45 nm generation
A new calibration method for critical dimension (CD) linearity improvement with an immersion microscope is proposed. Correlation tables of an edge position against CD of the clear pattern and CD of the dark pattern are obtained experimentally. The detected edge position is calibrated with the correction tables. Distance between the calibrated edge positions is output as CD. The experiment result indicates the calibration method improves CD linearity of an immersion microscope. CD repeatability with the calibration method using an immersion microscope is found to be sufficient for 45nm HP masks. As a result, an immersion microscope with our calibration method is available for CD measurement of 45 nm HP masks.
Photomasks are currently inspected based on the standard of defect size. A shortcoming of this standard is that the type of defects which do not impact on a wafer, could be detected as impermissible defects. All of them are subject to repair works and some of them require further inspection by AIMS. This is one of the factors that are pushing down the yield and the turnaround time (TAT) of mask manufacturing. An effective way to improve this situation will be to do the repair works selectively on the defects that are predicted to inflict a functional damage on a wafer. In this report, we will propose a defect evaluation system named <b>ADRES</b> (Advanced Photomask Defect Repair Evaluation System), featuring a function to extract edges from a mask SEM image to be passed on to a litho-simulation. A distinctive point of our system is the use of a mask SEM image with a high resolution.
Linearity improvement for critical dimension (CD) measurement of a photomask by the simulation assist (SA) method with a deep-UV microscope is proposed. In the conventional method, if the measurement pattern is resolved insufficiently with a deep-UV microscope, the CD cannot maintain linearity to the actual pattern size. In the SA method, the insufficient resolution is canceled by the actual image and the simulated image, and therefore the CD can maintain linearity even if the pattern is resolved insufficiently. The experiment result indicates that the SA method improves CD linearity of the conventional method; furthermore, it improves repeatability of hole patterns.
Since higher Critical Dimension (CD) accuracy on mask is required, there is a need to optimize CD definition for lithography. The conventional CD definition is based on the cross-sectional profile of mask pattern, but the cross-sectional profile does not reflect aerial image on wafer. Therefore, CD definition based on aerial image on wafer is preferable to the cross-sectional profile. We formulated a CD definition that reflects aerial image on wafer. In our definition, CD is called CDad. There are two types of CD measurement equipment: top view type such as CD-SEM, and transmitted light type such as deep-UV microscope. By simulation and experiment, we evaluated CD of top view and CD of deep-UV microscope to obtain CDad. The results show that CDad can be obtained with deep-UV microscope, but not to top view. Deep-UV microscope is available for CD measurement of 0.11 and 0.13 um generation masks.
Shrinking device design rule, lithography requires more rigid CD accuracy on a mask. In most cases, cross sectional profiles are not uniformed on a chromium mask. Cross sectional profiles influence not only CD value but also aerial image on wafer. Suitable CD value for lithography is the same influenced one as aerial image. Therefore we studied this influence, and evaluated which CD value is suitable for lithography. As our results, CD result of DUV microscope is most suitable for 0.13 and 0.15 micrometers lithography.
We have developed a new CD measurement method for a chromium pattern on a photomask. Using the scanning confocal laser microscope, we can not only measure CD of a chromium pattern, but also predict width of the chromium pattern tail. Using a scanning confocal laser microscope, we can obtain a reflective intensity profile. We can observe the minima in the profile of a chromium pattern. The position of the minimum almost corresponds to the pattern edge, in spite of a little offset. As a result of our analysis, there is a correlation between the offset and the chromium tail width, and the correlation depends on wavelength of a laser. Using two profiles with two wavelengths, we can obtain the chromium bottom width and the chromium tail width by two equations. By comparing the results of our method and the result of cross-sectional SEM observation, we have confirmed they are god agreement.