With shrinkage of device pattern, optical proximity correction (OPC) will be used for EUV lithography, which leads to need sub resolution assist features (SRAF) on EUV mask. Currently, it is difficult to fabricate EUV mask with SRAF of sub-30nm using conventional resist mask process stably. Moreover, it is necessary to improve line width roughness (LWR) of mask absorber pattern for achieving the lithographic specifications beyond hp15nm patterning. In this paper, in order to meet the requirements of Ta based absorber EUV mask with SRAF, mask fabrication process using new structure blank is studied for sub-30nm SRAF patterning and for improved LWR of primary feature. New mask process using new blank with thinner resist and Cr based hard mask was developed. By using new mask process, resolution of absorber pattern was achieved to 30nm for SRAF patterning, and LWR was improved comparing with conventional process.
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.
UV nano imprint lithography (UV-NIL) has high-throughput and cost-effective for complex nano-scale patterns and is
considered as a candidate for next generation lithography tool. In addition, NIL is the unmagnified lithography and
contact transfer technique using template. Therefore, the lithography performance depends greatly on the quality of the
According to ITRS 2013, the minimum half pitch size of Line and Space (LS) pattern will reach 1x nm level within
next five years. On the other hand, in hole pattern, half pith of 2x nm level will be required in five years. Pattern shrink
rate of hole pattern size is slower than LS pattern, but shot counts increase explosively compared to LS pattern due to its
data volume. Therefore, high throughput and high resolution EB lithography process is required.
In previous study, we reported the result of hole patterning on master template which has high resolution resist
material and etching process. This study indicated the potential for fabricating 2xnm hole master template .
After above study, we aim at fabricating the good quality of 2xnm master template which is assured about defect, CD
uniformity(CDU), and Image placement(IP). To product high quality master template, we develop not only high
resolution patterning process but also high accuracy quality assurance technology. We report the development progress
about hole master template production.
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.
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.
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.
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.