Solar cells can strongly benefit from optical strategies capable of providing the desired broadband absorption of sunlight and consequent high conversion efficiency. While many diffractive light-trapping structures prove high absorption enhancements, their industrial application rather depends on simplicity concerning the integration to the solar cell concept and the process technology. Here, we show how simple grating lines can perform as well as advanced light-trapping designs. We use a shallow and periodic grating as the basic element of a quasi-random structure, which is highly suitable for industrial mass production. Its checkerboard arrangement breaks the mirror symmetry and is shown, for instance, to enhance the bulk current of a 1 µm slab of crystalline silicon by 125%. We explain its excellent performance by drawing a direct link between a structure’s Fourier series and the implied photocurrent, derived from a large and diverse set of structures. Our design rule thus meets all relevant aspects of light-trapping for solar cells, clearing the way for simple, practical, and yet outstanding diffractive structures, with a potential impact beyond photonic applications.

Light trapping in solar cells: simple design rules to maximize absorption

The ability to manufacture a nanogap in between two electrodes has proven a powerful catalyst for scientific discoveries in nanoscience and molecular electronics A wide range of bottom-up and top-down methodologies are now available to fabricate nanogaps that are less than 10 nm wide However, most available techniques involve time-consuming serial processes that are not compatible with large-scale manufacturing of nanogap devices The scalable manufacturing of sub-10 nm gaps remains a great technological challenge that currently hinders both experimental nanoscience and the prospects for commercial exploitation of nanogap devices Here, available nanogap fabrication methodologies are reviewed and a detailed comparison of their merits is provided, with special focus on large-scale and reproducible manufacturing of nanogaps The most promising approaches that could achieve a breakthrough in research and commercial applications are identified Emerging scalable nanogap manufacturing methodologies will ultimately enable applications with high scientific and societal impact, including high-speed whole genome sequencing, electromechanical computing, and molecular electronics using nanogap electrodes

Scalable Manufacturing of Nanogaps

A study of defects on EUV masks using blank inspection, patterned mask inspection, and wafer inspection Sungmin Huh!, Liping Ren!, David Chan!, Stefan Wunn!, Kenneth Goldberg2, Iacopo Mochi2, Toshio Nakajima 3 , Masahiro Kishimot0 , h 4 Byungsup An, Inyong Kang 4 , Joo-on Par k4 ,Kyoungyong Co, h 4 Sang-in Hans, Thomas Laursen ! SEMATECH 255 Fuller Road, Suite 309, Albany, NY 12203 USA 2 2-400, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 3 AGC Electronics America, 257 Fuller Road, Albany NY 12203 Samsung Electronics Co., San#16 Banwol-Dong, Hwasung-City, Gyeonggi-Do, Korea, 445-701 5 ASML 25 Corporate Circle, Albany, NY 12203 ABSTRACT The availability of defect-free masks remains one of the key challenges for inserting extreme ultraviolet lithography (EUVL) into high volume manufacturing. yet link data is availahle for understanding native defects on real masks. In this papeL a full-field EL'V mask is fabricated to investigate the printability \)fvarious defects on the mask. The printability of del~cts and idenlification of their source from mask fabricationlu handling were studied lIsing wafer inspc '\ 2:1'>-;'\ i at C'\.SE. Repeater anal: ses \)f w<lfer inspection and patterned mask inspection were used to classify all defects found during the wafer inspecti,)n. Lsing inf\lrlnmion fI()m repeater defects. the definition of defects induced from the mask blank is dis~'ussed ;{nd \\<1: s l\) imp!()H' the sensitivlt) ()f \\£1 I\:I inspecti()fl w(,is lor better quali iication (lC the Iinal EL \ ma~k alc propl)Seti.

A study of defects on EUV mask using blank inspection, patterned mask inspection, and wafer inspection

ArF immersion lithography combined with double patterning has been used for fabricating below half pitch 40nm devices However, when pattern size shrinks below 20nm, we must use new technology like quadruple patterning process or next generation lithography (NGL) solutions Moreover, with change in lithography tool, next generation mask production will be needed According to ITRS 2013, fabrication of finer patterns less than 15nm will be required on mask plate in NGL mask production 5 years later [1] In order to fabricate finer patterns on mask, higher resolution EB mask writer and high performance fabrication process will be required In a previous study, we investigated a potential of mask fabrication process for finer patterning and achieved 17nm dense line pattern on mask plate by using VSB (Variable Shaped Beam) type EB mask writer and chemically amplified resist [2][3] After a further investigation, we constructed higher performance mask process by using new EB mask writer EBM9000 EBM9000 is the equipment supporting hp16nm generation's photomask production and has high accuracy and high throughput As a result, we achieved 155nm pattern on mask with high productivity Moreover, from evaluation of isolated pattern, we proved that current mask process has the capability for sub-10nm pattern These results show that the performance of current mask fabrication process have the potential to fabricate the next-generation mask

/pdf/high-performance-mask-fabrication-process-for-the-next-27jufd978y.pdf

High performance mask fabrication process for the next-generation mask production

Electron beam (EB) lithography used for mask and mold fabrication is an indispensable technology in the lithography used for high-volume production of semiconductor devices. With the reduction in the critical dimensions of semiconductor devices, the requirement for EB lithography also becomes severe. In this study, the feasibility of single nano patterning using EB lithography with a chemically amplified resist process was investigated. The latent images of line-and-space patterns with a 7 nm quarter-pitch (7 nm space width and 21 nm line width) were calculated on the basis of sensitization and reaction mechanisms of chemically amplified EB resists. Simulations indicated that the line-and-space patterns with 7 nm quarter-pitch can be resolved with line edge roughness of 0.9–1.9 nm with a sensitivity of 270 µC cm−2 using a 3 nm electron beam.

https://iopscience.iop.org/article/10.7567/JJAP.54.056501/pdf

Theoretical study of fabrication of line-and-space patterns with 7 nm quarter-pitch (7 nm space width and 21 nm line width) using electron beam lithography with chemically amplified resist processes: I. Relationship between sensitivity and chemical gradient

Extreme Ultraviolet Lithography (EUVL) is a promising technology for the fabrication of ULSI devices with 20nm
half-pitch node. One of the key challenges before EUVL is to achieve defect-free masks. There are three main
categories of mask defects: multilayer defects which cause phase defects, absorber pattern defects, and particles during
blank/mask fabrication or mask handling after mask fabrication. It is important to manage multilayer defect because
small multilayer defects are difficult to be identified by SEM/AFM after mask patterning and can impact wafer
printing.
In this paper, we assess blank defect position error detected by 3 rd generation blank inspection tool, using blank
defect information from blank supplier and 199nm wavelength patterned mask inspection tool NPI-7000. And we rank
blank defect in the order of projection defect size to multilayer in order to estimate blank defect printability. This
method avoids overestimating the number of potential killer defects that hardly be identified by SEM/AFM under the
condition that EUV-AIMS is not available.

Defect management of EUV mask

Nanoimprint lithography (NIL) is one of the highest potential candidates for next generation lithography in
semiconductors. NIL is very useful technology for pattern fabrication in high resolution 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. Accordingly, the management of the cross-sectional
profile on the template pattern is much more important than on each photomask.
In our previous report, 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 various researches, we found the application is very effective in the method of
cross-sectional profiling of sub-20 nm half-pitch lines-and-spaces (LS) patterns.
In this report, we investigated the capabilities of measuring cross-sectional profiles for hole patterns using GISAXS.
Since the pattern density of hole patterns is much lower than that of LS patterns, the intensity of X-ray scattering in hole
measurements is much lower. We optimized some measurement conditions to build the hole measurement system.
Finally, the results suggested that 3D profile measurement of hole pattern using GISAXS has sufficient performance to
manage the cross-sectional profile of template. The measurement system using GISAXS for measuring 3D profiles
establishes the cross-sectional profile management essential for the production of high quality quartz hole templates.

The capability of measuring cross-sectional profile for hole patterns in nanoimprint templates using small-angle x-ray scattering

Nanoimprint lithography (NIL) is one of the highest potential candidates for next generation lithography (NGL) in semiconductors[1][2]. NIL is very useful technology for pattern fabrication in high resolutions and low costs compared to conventional optical lithography[3]. 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[4]. 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[5] and additionally in hole patterns[6]. 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.

Throughput improvement method for cross-sectional profile measurement of hole patterns in nanoimprint templates

Nano imprint lithography (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. In this study, we investigated the resolution and the defect level for hole patterning using chemical amplified resists (CAR) and VSB type EB writer, EBM9000. To form smaller pattern with high quality, high resolution resist process and high sensitivity etching process are needed. After these elements were optimized, we succeeded to form 24 nm dense hole pattern on template. In general, it is difficult to suppress the defect density in a large area because of fogging effect and process loading and so forth. However, from the view point of defect quality, 26 nm hole pattern is achieved to form with practical level in a large area. Therefore, we indicate the capability of forming 26 nm hole master template which will be required in 2019 from ITRS2013. These results show that this process is possible to obtain less than 30 nm hole pattern without enormous writing time. As future work, we will imprint master to replica template and check the printability.

Kazuki Hagihara

Papers

High performance mask fabrication process for the next-generation mask production

Defect management of EUV mask

The capability of measuring cross-sectional profile for hole patterns in nanoimprint templates using small-angle x-ray scattering

Throughput improvement method for cross-sectional profile measurement of hole patterns in nanoimprint templates

High resolution hole patterning with EB lithography for NIL template production