Placement of cylinders in hole multiplication patterns for directed self-assembly is the topic of this computational study. A hole doublet process applying a corner rounded rectangle guide is the focus of this work. Placements including morphology fluctuation can be analyzed by dissipative particle dynamics simulation. When the surface of guides and underlayers are modified from strong polymethyl methacrylate (PMMA) attractive to weak PMMA attractive, two PMMA cylinders can be contacted at the underlayer. Even when the PMMA domain had a separated morphology, hole placement errors (HPE) were similar to those with connected domains which occurred in the strong PMMA affine case. In general, HPE in longitudinal guide direction was larger than in the shorter direction. It is interesting to note that HPE in the longer direction was decreased by increasing the guide size in shorter direction. Cylinder tops likely fluctuate; cylinder middles may fluctuate as well in some cases. Means for HPE reduction were also tested computationally: reducing the guide thickness and employing dimpled structures. Decreasing guide thickness was effective for reducing HPE; however, guide thicknesses that were too thin prevented PMMA domains from forming vertical cylinders. Dimpled structures also reduced HPE. The depth of the dimple had a little influence on the distance of two holes when the guide structure was fitted with hexagonal packing for the block co-polymers.
Directed Self-Assembly (DSA) is being extensively evaluated for application in semiconductor process integration.<sup>1-7 </sup>Since 2011, the number of publications on DSA at SPIE has exploded from roughly 26 to well over 80, indicating the groundswell of interest in the technology. Driving this interest are a number of attractive aspects of DSA including the ability to form both line/space and hole patterns at dimensions below 15 nm, the ability to achieve pitch multiplication to extend optical lithography, and the relatively low cost of the processes when compared with EUV or multiple patterning options. <p> </p>Tokyo Electron Limited has focused its efforts in scaling many laboratory demonstrations to 300 mm wafers. Additionally, we have recognized that the use of DSA requires specific design considerations to create robust layouts. To this end, we have discussed the development of a DSA ecosystem that will make DSA a viable technology for our industry, and we have partnered with numerous companies to aid in the development of the ecosystem. This presentation will focus on our continuing role in developing the equipment required for DSA implementation specifically discussing defectivity reduction on flows for making line-space and hole patterns, etch transfer of DSA patterns into substrates of interest, and integration of DSA processes into larger patterning schemes.
We report computational study for directed self-assembly (DSA) on morphologies’ dislocation caused by block copolymers’ (BCPs’) thermal fluctuation in grapho-epitaxial cylindrical guides. The dislocation factor expressed as DSA-oriented placement errors (DSA-PEs) was numerically evaluated by historical data acquisition utilizing dissipative particle dynamics simulation. Calculated DSA-PEs was compared with experimental results on two kinds of guide pattern, resist guide with no surface modifications (REF guide) and resist guide with polystyrene coated (PS-brush guide). Vertical distribution of DSA-PEs within the cylindrical guides was calculated and relatively high DSA-PEs near top region was deduced particularly in REF guide. The tendency of experimental DSA-PEs was well explained by the calculation including a fluctuation parameter on the wall particles. In PS-brush guide, calculated DSA-PEs was drastically increased with becoming the guide more fluctuating. This result indicates to fabricate hard and steady guide condition in PS-brush guide so as to achieve better placements. From the variety of guide critical dimension (CD) computation, it is suggested that smaller guide CD is better to obtain good placements. The smallest DSA-PE value in this study was observed in PS-brush guide with smaller guide CD because of the strong restriction of BCP arrangement flexibility.
Next-generation lithography technology is required to meet the needs of advanced design nodes. Directed Self Assembly (DSA) is gaining momentum as an alternative or complementary technology to EUV lithography. We investigate defectivity on a 2xnm patterning of contacts for 25nm or less contact hole assembly by grapho epitaxy DSA technology with guide patterns printed using immersion ArF negative tone development. This paper discusses the development of an analysis methodology for DSA with optical wafer inspection, based on defect source identification, sampling and filtering methods supporting process development efficiency of DSA processes and tools.
Proc. SPIE. 9049, Alternative Lithographic Technologies VI
KEYWORDS: Lithography, Polymethylmethacrylate, Particles, 3D modeling, Scanning electron microscopy, Monte Carlo methods, Photomasks, Directed self assembly, Picosecond phenomena, Scanning transmission electron microscopy
In this report, morphology of cylinders by block copolymer (BCP) in the corner rounded rectangle guide patterns is
analyzed by simulation and compared with experimental results. In the case of the hole-multiplication, selection the
guide pattern size and the affinity of wall and under layer is necessary for stable micro structure. To search the good
guide conditions, Ohta-Kawasaki (OK) model and dissipative particle dynamics (DPD) are used. OK model is well
known as low cost simulation method, therefore it is expected to use for searching the good guide area roughly from
wide range. DPD is one of the strong candidates for DSA simulation, and it is used for prediction of the micro structure.
As results, the guide size area which has two PMMA cylinders by 2D OK model seems consistent with experimental
results, 3D micro structure by OK model and DPD are comparable, 3D simulations have good agreements with
experimental results observed by CD-SEM and STEM. Especially two cylinders connected each other at some point
predicted by 3D simulation is observed actually. These simulation approaches will be important to decide the lithography
mask design, film stack and pre-treatment conditions for more complex multiplication process, for example, the cut mask
Directed Self-Assembly (DSA) is one of the most promising technologies for scaling feature sizes to 16 nm and below.
Both line/space and hole patterns can be created with various block copolymer morphologies, and these materials allow
for molecular-level control of the feature shapes—exactly the characteristics that are required for creating high fidelity
lithographic patterns. Over the past five years, the industry has been addressing the technical challenges of maturing this
technology by addressing concerns such as pattern defectivity, materials specifications, design layout, and tool
requirements. Though the learning curve has been steep, DSA has made significant progress toward implementation
in high-volume manufacturing.
Tokyo Electron has been focused on the best methods of achieving high-fidelity patterns using DSA processing. Unlike
other technologies where optics and photons drive the formation of patterns, DSA relies on surface interactions and
polymer thermodynamics to determine the final pattern shapes. These phenomena, in turn, are controlled by the
processing that occurs on clean-tracks, etchers, and cleaning systems, and so a host of new technology has been
developed to facilitate DSA. In this paper we will discuss the processes and hardware that are emerging as critical
enablers for DSA implementation, and we will also demonstrate the kinds of high fidelity patterns typical of mainstream
This paper discusses the defect density detection and analysis methodology using advanced optical wafer inspection capability to enable accelerated development of a DSA process/process tools and the required inspection capability to monitor such a process. The defectivity inspection methodologies are optimized for grapho epitaxy directed self-assembly (DSA) contact holes with 25 nm sizes. A defect test reticle with programmed defects on guide patterns is designed for improved optimization of defectivity monitoring. Using this reticle, resist guide holes with a variety of sizes and shapes are patterned using an ArF immersion scanner. The negative tone development (NTD) type thermally stable resist guide is used for DSA of a polystyrene-<i>b</i>-poly(methyl methacrylate) (PS-<i>b</i>-PMMA) block copolymer (BCP). Using a variety of defects intentionally made by changing guide pattern sizes, the detection rates of each specific defectivity type has been analyzed. It is found in this work that to maximize sensitivity, a two pass scan with bright field (BF) and dark field (DF) modes provides the best overall defect type coverage and sensitivity. The performance of the two pass scan with BF and DF modes is also revealed by defect analysis for baseline defectivity on a wafer processed with nominal process conditions.
We report morphology of cylinder of diblock copolymers (BCP), which consist of polymer A and B, in cylindrical prepattern
holes by dissipative particle dynamics simulation in order to predict optimal cylinder profile. Configuration of
cylinder which consists of polymer <i>B</i> changes along with change of affinity of underlayer and guide wall for BCP. In the case of underlayer, neutral to both the polymer species shows the most stable cylinder shape. When affinity converts to either polymer, cylinder shape gets distorted. In the case of intergrading guide wall condition from A wet to <i>B</i> wet for a certain hole CD, polymer <i>B</i>, that constitutes cylinder, gradually loosen and stack on the guide eventually. Moreover
cylinder forms again for <i>B</i> wet larger hole. Free energy for hole CD is also investigated and the profile shows A wet wall
and B wet wall are suitable for hole shrink in a narrow and wide range of hole CD, respectively. Because free energy of
<i>A</i> wet wall varies widely for hole CD change. In contrast, free energy of <i>B</i> wet wall exhibits no significant changes and
the profiles signify that cylinder shapes relatively stable in wider range than <i>A</i> wet wall.
Immersion lithography has been developed for 45nm technology node generation during the last several years. Currently, IC manufacturers are moving to high volume production using immersion lithography. Due to the demand of IC manufactures, as the critical dimension (CD) target size is shrinking, there are more stringent requirements for CD
Post Exposure Bake (PEB) process, which is the polymer de-protection process after exposure, is one of the important processes to control the CD in the 193nm immersion lithography cluster. Because of the importance of the PEB process for CD uniformity, accurate temperature control is a high priority. Tokyo Electron LTD (TEL) has been studying the temperature control of PEB plates. From our investigation, total thermal history during the PEB process is a key point for controlling intra wafer and inter wafer CD <sup></sup>. Further, production wafers are usually warped, which leads to a nonuniform thermal energy distribution during the PEB process. So, it is necessary to correct wafer warpage during the baking process in order to achieve accurate CD control on production wafers. TEL has developed a new PEB plate for 45nm technology node mass production, which is able to correct wafer warpage. The new PEB plate succeeded in
controlling the wafer temperature on production wafers using its warpage control function.
In this work, we evaluated CD process capability using the wafer warpage control PEB plate, which is mounted on a
CLEAN TRACK<sup>TM</sup> LITHIUS Pro<sup>TM</sup><i>-i</i> (TEL) linked with the latest immersion exposure tool. The evaluation was performed together with an IC manufacturer on their 45nm production substrates in order to determine the true performance in production.
In order to prepare for the next generation technology manufacturing, ASML and TEL are working together to
investigate the process performance of the LITHIUSi+/ TWINSCAN XT:1700i lithocluster through decreasing critical
dimension patterning. In this evaluation, process performance with regards to critical dimension uniformity and
defectivity are compared at different critical dimensions in order to determine areas of concentration for equipment and
process development. Specifically, design of experiments were run using immersion rinse processing at 60nm hp and
45nm hp. Defects were classified to generate a pareto for each technology node to see if there is any change in the defect
types as critical dimensions are shrinking. Similarly, critical dimension uniformity was compared through technology
nodes to see if any budget contributions have increased sensitivities to the smaller patterning features. Preliminary gauge
studies were performed for the 45nm hp evaluation, as metrology at this design rule is not yet fully proven. More work
is necessary to obtain complete understanding of metrology capabilities as this is crucial to discern precise knowledge of
processing results. While preliminary results show no adverse impact moving forward, this work is a first screening of
45nm immersion processing and more work is needed to fully characterize and optimize the process to enable robust
manufacturing at 45nm hp.
The development of next-generation exposure equipment in the field of lithography is now underway as the demand
increases for faster and more highly integrated semiconductor devices. At the same time, proposals are being made for
lithography processes that can achieve finer pattern dimensions while using existing state-of-the-art ArF exposure
Immersion exposure technology can use a high-refraction lens by filling the space between the exposed substrate and the
projection lens of the exposure equipment with a liquid having a high refractive index. At present, the development of
193-nm immersion exposure technology is proceeding at a rapid pace and approaching the realm of mass production.
However, the immersion of resist film in de-ionized water in 193-nm immersion exposure technology raises several
concerns, the most worrisome being the penetration of moisture into the resist film, the leaching of resist components
into the water, and the formation of residual moisture affecting post-processing. To mitigate the effects of directly
immersing resist in de-ionized water, the adoption of a top coat is considered to be beneficial, but the possibility is high
that the same concerns will rise even with a top coat.
It has been reported that immersion-specific defects in 193-nm immersion exposure lithography include "slimming,"
"large bridge," "swell," "micro-bridge," and "line pitch expansion," while defects generated by dry lithography can be
summarized as "residue," "substrate induced," "discoloration," and "pattern collapse." Nevertheless, there are still many
unexplained areas on the adverse effects of water seeping into a top coat or resist. It is vitally important that the
mechanisms behind this water penetration be understood to reduce the occurrence of these immersion-induced defects.
In this paper, we use top coats and resist materials used in immersion lithography to analyze the penetration and
diffusion of water. It is found that the water-blocking performance of protective-film materials used in immersion
lithography may not be sufficient at the molecular level. We discuss the diffusion of water in a top coat and its effects.
As a powerful candidate for a lithography technique that can accommodate the scaling-down of semiconductors, 193-nm immersion lithography-which realizes a high numerical aperture (NA) and uses deionized water as the medium between the lens and wafer in the exposure system-has been developing at a rapid pace and has reached the stage of practical application. In regards to defects that are a cause for concern in the case of 193-nm immersion lithography, however, many components are still unclear and many problems remain to be solved. It has been pointed out, for example, that in the case of 193-nm immersion lithography, immersion of the resist film in deionized water during exposure causes infiltration of moisture into the resist film, internal components of the resist dissolve into the deionized water, and residual water generated during exposure affects post-processing. Moreover, to prevent this influence of directly immersing the resist in de-ionized water, application of a protective film is regarded as effective. However, even if such a film is applied, it is still highly likely that the above-mentioned defects will still occur. Accordingly, to reduce these defects, it is essential to identify the typical defects occurring in 193-nm immersion lithography and to understand the condition for generation of defects by using some kinds of protective films and resist materials. Furthermore, from now onwards, with further scaling down of semiconductors, it is important to maintain a clear understanding of the relation between defect-generation conditions and critical dimensions (CD). Aiming to extract typical defects occurring in 193-nm immersion lithography, the authors carried out a comparative study with dry exposure lithography, thereby confirming several typical defects associated with immersion lithography. We then investigated the conditions for generation of defects in the case of some kinds of protective films. In addition to that, by investigating the defect-generation conditions and comparing the classification data between wet and dry exposure, we were able to determine the origin of each particular defect involved in immersion lithography. Furthermore, the comparison of CD for wet and dry processing could indicate the future defectivity levels to be expected with shrinking immersion process critical dimensions.
Utilizing de-ionized water as the medium between the wafer and lens of the exposure system and realizing high numerical aperture (NA), 193-nm immersion lithography is being developed at a great pace towards practical application. Recent improvements in materials, processing and exposure systems have dramatically reduced the defectivity levels in immersion processing. However, in order to completely eradicate immersion related defects and achieve defectivity levels required for ideal productivity, further investigation into the defect generation mechanism and full understanding of the improvements garnered so far is required. It is known that leaching of resist component materials during exposure and penetration of remaining water from the immersion scanning process are two key contributors towards immersion related defects. Additionally, the necessity to increase the hydrophobicity of the resist materials has had a signification effect on remaining resist residues. In order to more fully understand the generation of defects from the these contributions, it is necessary not only to analyze properties of the defects, but also investigate the change in composition originating from advanced processing techniques that have shown improvements in defectivity performance.