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Sequential infiltration synthesis (SIS), when combined with novel polymeric materials capable of self-assembly, such as block copolymers (BCPs), has been shown to effectively improve the pattern transfer of nanoscale templates. Herein, we present a study of the SIS process aimed at elucidating some critical aspects such as the evolution of the BCP morphology and mechanical properties after infiltration. Atomic force microscopy nanomechanical mapping was able to measure a consistent stiffness change within the SIS-infiltrated poly(methyl methacrylate) (PMMA) blocks. Interestingly, the increase in Young’s modulus of the infiltrated blocks is small compared to the final stiffening of the same infiltrated features after a treatment with oxygen plasma.

In this work, an evaluation of various adhesion promoters (or primers) for soft ultra-violet (UV) nanoimprint lithography (NIL) is reported. The evaluation is performed using 200 mm wafer scale in the HERCULES® NIL equipment platform available at the CEA-Leti. First, surface energies of the primers are determined through contact angle measurements. Next, atomic force microscope (AFM) measurements were carried out to evaluate the surface uniformity and roughness of the primed wafers. Thin film thickness measurements were performed by spectroscopic ellipsometry in order to select the most promising primer processes for high resolution etch mask and permanent applications. Afterwards, the adhesion layer performances of the selected primer processes were evaluated by an imprint test using a dedicated patterned master (critical dimension down to 30 nm and aspect ratios up to 1.5). Optical and scanning electron microscope (SEM) defect reviews were systematically performed. This evaluation enabled to benchmark several adhesion promotor solutions based on the grafted technology developed by ARKEMA in order to identify an efficient adhesive layer compatible with various NIL resists and substrates, such as silicon based materials or glass.

Advanced surface affinity control for grapho-epitaxy directed self-assembly (DSA) patterning is essential for providing reliable DSA-based solutions for the development of semiconductor patterning. Independent control of surface affinity between the bottom and the sidewalls of a topographical guiding structure was achieved by embedding an ultrathin layer in the guiding template stack. The implementation of an embedded layer with tunable surface properties for DSA grapho-epitaxy was evaluated and optimized on 300 mm wafers by critical dimension SEM characterization. It was demonstrated that a thin protective layer, placed between the hard mask guiding template and the embedded layer, allows the preservation of the surface properties of the embedded layer during guiding template etching. The DSA performances of this novel grapho-epitaxy integration, using a topographical template patterned with 193 nm immersion lithography, were evaluated by monitoring the success rate and the critical dimension uniformity of the shrunk contacts. FIB-STEM analyses were further carried out to analyze the residual polymer thickness on the resulting contacts. This new integration leads to the control of the polymer residual thickness (a few nanometers) and uniformity (inferior to 1 nm) at the bottom of the guiding template which will facilitate the subsequent DSA pattern transfer.

CH (Contact hole) patterning by DSA (Directed Self-Assembly) of BCP (Block Copolymer) is still attracting interest from the semiconductor industry for its CH repair and pitch multiplication advantages in sub-7nm nodes. For several years, extensive studies on DSA CH patterning have been carried out and significant achievements have been reported in materials and process optimization, CMOS integration and design compatibility and advanced characterization [1-4]. According to these studies, if a common agreement was clearly made for the use of PS-b-PMMA material as a potential candidate for DSA CH patterning integration in advanced nodes, the associated guiding template material was not yet selected and is still under investigation. Whereas the most reported guiding template materials for DSA PS-b-PMMA CH patterning are organic-based (resist or organic hard mask), we propose in this work to investigate a DSA process based on inorganic template material (silicon oxide based). Indeed, this latter offers some advantages over organic template: better surface affinity control, higher thermal stability during BCP self-assembly annealing, easier 3D-morphology imaging of DSA patterns and the possibility of wafer rework after the DSA step. The inorganic template based DSA process was first optimized using the planarization approach [5]. We demonstrated that the silicon oxide thickness should be properly adjusted to allow a good control of the BCP thickness over different guiding template densities. Afterwards, we compared the DSA performances (critical dimension: CD; CD uniformity: CDU, contact misalignment and defectivity) between both inorganic and organic template approaches. Equivalent results were obtained as shown in Figure 1. Finally, we demonstrated that inorganic template allows the rework of DSA wafers: similar CD and CDU for both guiding and DSA patterns were obtained after 3 cycles of rework (Figure 2).

In this work, an evaluation of various ASL processes for 200 mm wafer scale in the HERCULES® NIL equipment platform available at the CEA-Leti through the INSPIRE program is reported. The surface and adherence energies were correlated to the AFM and defectivity results in order to select the most promising ASL process for high resolution etch mask applications. The ASL performances of the selected process were evaluated by multiple working stamp fabrication using unpatterned and patterned masters though defectivity monitoring on optical based-inspection tools. Optical and SEM defect reviews were systematically performed. Multiple working stamps fabrication without degradation of the master defectivity was witnessed. This evaluation enabled to benchmark several ASL solutions based on the grafted technology develop by ARKEMA in order to reduce and optimize the soft stamp defectivity prior to its replication and therefore considerably reduce the final imprint defectivity for the Smart NIL process.

High chi organic lamellar-forming block copolymers were prepared with 18 nm intrinsic period Lo value. The BCPs were coated on a neutral layer on silicon substrates and were either thermally annealed or exposed to solvent vapors both in a 300mm track. The effect of lowering the glass transition temperature (Tg) on the high chi BCP was investigated. Process temperatures and times were varied. It was found that the BCP having lower Tg exhibits faster kinetics and is able to reach alignment in a shorter time than a similar BCP having higher Tg. Fingerprint defect analysis also shows that the BCP with lower Tg has lower defects. The results show that fingerprint formation can be achieved with either ether or ester type solvents depending on the BCP used. The results show that a track process for solvent annealing of high-χ BCPs is feasible and could provide the path forward for incorporation of BCP in future nodes. Finally, directed self-assembly was demonstrated by implemented high chi polymers on a graphoepitaxy test vehicles. CD and line width roughness was evaluated on patterns with a multiplication factor up to 7.

DSA patterning is a promising solution for advanced lithography as a complementary technique to standard and future lithographic technologies. In this work, we focused on DSA grapho-epitaxy process-flow dedicated for contact hole applications using polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymers. We investigated the impact on the DSA performances of the surface affinity of a guiding pattern design by ArF immersion lithography. The objective was to control and reduce the polymer residue at the bottom of the guiding pattern cavities since it can lead to lower a DSA-related defectivity after subsequent transfer of the DSA pattern. For this purpose, the DSA performances were evaluated as a function of the template surface affinity properties. The surface affinities were customized to enhance DSA performances for a PS-b-PMMA block copolymer (intrinsic period 35nm, cylindrical morphology) by monitoring three main key parameters: the hole open yield (HOY), the critical dimension uniformity (CDU-3σ) and the placement error (PE-3σ). Scanning transmission electron microscopy (STEM) was conjointly carried out on the optimized wafers to characterize the residual polymer thickness after PMMA removal. The best DSA process performances (i.e., hole open yield: 100%, CDU-3σ: 1.3nm and PE-3σ: 1.3nm) were achieved with a thickness polymer residue of 7 nm. In addition, the DSA-related defectivity investigation performed by review-SEM enabled us to achieve a dense (pitch 120nm) contact area superior to 0.01mm2 free of DSA-related defects. This result represents more than 6x105 SEM-inspected valid contacts, attesting the progress achieved over the last years and witnessing the maturity of the DSA in the case of contact holes shrink application.

International audience; Silicon-containing and modified PS-b-PMMA high-χ block copolymers materials were produced to achieve lamellar mesostructure as low as 14 nm intrinsic period (L$_0$) and ordered by graphoepitaxy or chemoepitaxy processes. Line Edge Roughness (LER) measurements of 2.5 nm (3 σ) can be extracted from CD-SEM pictures of poly [(1,1-dimethylsilacyclobutane)-b-styrene] after etching step. Materials integrations on a 300 mm track process are highlighted. In fingerprint, new BCPs LWR L/S values are 1.5/1.1 nm in comparison to a graphoepitaxy flow where the LWR L/S values are 2.0/1.1 nm. Alternative methods to create high-resolution guiding patterns for directed self-assembly of block co-polymers and the scale-up to obtain industrial BCPs meeting electronic requirement are also reported.

Conference, San Jose CA, Feb 22-25, 2016. Sponsor(s) : SPIE; Tokyo Ohka Kogyo Co; International audience; Properties of new block copolymers systems, specifically designed to reach large periods for the features, are compared to the ones exhibited by classical PS-b-PMMA materials of same dimensions. Conducted studies, like free-surface defects analysis, mild-plasma tomography experiments, graphoepitaxy-guided structures, etch-transfer. indicate much better performances, in terms of achievable film-thicknesses with perpendicular features, defects levels, and dimensional uniformities, for the new system than for the classical PS-b-PMMA. These results clearly highlight unique and original solutions toward an early introduction of DSA technology into large lithographic nodes.

The nanomechanical properties of solvent cast polymer thin films have been investigated using PeakForce TM quantitative nanomechanical mapping. The samples consisted in films of polystyrene and poly(methyl methacrylate) obtained after dewetting of toluene solution on a polymeric brush layer. As a second step, we have probed the mechanical properties of Poly(styrenen- methilmethacrylate) (PS-b-PMMA) block co-polymers (BCP) thin films randomly oriented. The measured films has a critical thickness below 50 nm and present features to be resolved of less than 42 nm. Measured surface elastic modulus obtained present a good agreement with previous literature and show how PeakForce technique could be crucial to BCP investigation predicting the mechanical stability of the different phases.

Directed Self-Assembly (DSA) of Block Copolymers (BCP) is one of the most promising solutions for sub-10 nm nodes. However, some challenges need to be addressed for a complete adoption of DSA in manufacturing such as achieving DSA-friendly design, low defectivity and accurate pattern placement. In this paper, we propose to discuss the DSA integration flows using graphoepitaxy for contact-hole patterning application. DSA process dependence on guiding pattern density has been studied and solved thanks to a new approach called “DSA planarization”. The capabilities of this new approach have been evaluated in terms of defectivity, Critical Dimension (CD) control and uniformity before and after DSA etching transfer.

© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE). The nanomechanical properties of solvent-cast polymer thin films have been investigated using PeakForce™ Quantitative Nanomechanical Mapping. The samples consisted of films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) obtained after the dewetting of toluene solution on a polymeric brush layer. Additionally, we have probed the mechanical properties of poly(styrene-b-methyl methacrylate) block copolymers (BCP) as randomly oriented thin films. The probed films have a critical thickness, This work was partially funded by the projects SNM (FP7-ICT-2011-8) and FORCE-for-FUTURE (CSD2010-00024).

Contact hole (CH) patterning by directed-self-assembly (DSA) of polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymers (BCPs) is extensively studied in this paper. Based on statistical analysis performed on 300mm wafers, a process window (PW) for CH shrink is experimentally evaluated in terms of hole open yield and critical dimension (CD) variation after DSA as a function of BCPs of different natural periods and guiding patterns of different dimensions. The PW allowed us to define the suitable BCP molecular weight with the best guiding CD ranges required to achieve a desired DSA hole CD within a specific tolerance. As example, for a DSA hole CD targeted at 19.5 nm with 10% tolerance, circular guiding patterns of 52 nm CD with 20% guiding CD latitude are needed using a 35nm-natural-period BCP. It is also shown that the CH shrink PW is dependent on guiding pattern pitch and on DSA process conditions such as the self-assembly annealing and spin coating conditions. In addition, the study highlights an interesting property of commensurability between guiding pattern dimensions and BCP’s natural period that governs the CH patterning by DSA for both CH shrink and CH doubling configurations. This permits to predict the guiding pattern dimensions needed for CH patterning by DSA using a given BCP of known natural period.

Careful control and reproducibility of BCP’s synthesis are mandatory parameters to push-down PS-b-PMMA block-copolymer systems toward its lowest dimensions for microelectronic applications. The self-assembly process optimization of different high-resolution cylindrical PS-b-PMMA block-copolymers (i.e. L0 period below 25 nm) is studied to highlight processes-variations as regard to more classical PS-b-PMMA systems while the characterizations of bulk materials provide deeper insights on the parameters addressing the self-assembly of such materials. The integration of a high-resolution BCP on 300 mm track is then studied to check the capabilities of such materials in terms of lithographic applications. CD uniformity measurements in contact hole shrink approach, as well as the transfer of the BCP mask into typical industrial under-layer stacks leading to aggressive features, show that these materials exhibit promising potentials for advanced lithographic nodes.

T his paper reports on the etch challenges to overcome for the implementation of PS -b-PMMA block c oSRO\PHU¶VDirected Self -Assembly (DSA ) in CMOS via patterning level . Our process is based on a graphoepitaxy approach , employing an industrial PS -b-PMMA block copolymer (BCP) from Arkema with a cylindrical morphology . The process consists in the following step s: a) DSA of block copolymers inside guiding patterns, b) PMMA remov al, c) brush layer opening and finally d ) PS pattern transfer into typical MEOL or BEOL stacks . All results presented here KDYHEHHQSHUIRUPHGRQWKH'6$/HWL¶V PPSLORWOLQH The f irst etch challenge to overcome for BCP transfer involves in removing all PMMA selectively to PS block . In our process baseline, a n acetic acid treatment is carried out to develop PMMA domains . However, this wet development has shown some limitations in te rms of resists compatibility and will not be appropriated for lamellar BCP s. That is why we also investigate the possibility to remove PMMA by only dry etching . In this work the potential of a dry PMMA removal by using CO based chemistries is shown and com pared to wet development . The advantages and limitations of each approach are reported . The second crucial step is the etching of brush layer (PS -r-PMMA ) through a PS mask . We have optimize d this step in order to preserve the PS patterns in terms of CD , holes features and film thickness. Several integrations flow with complex stacks are explored for contact shrink ing by DSA. A study of CD uniformity has been addressed to evaluate the capabilities of DSA approach after graphoepitaxy and after etching . Keyw ords: block copolymer, PS -b-PMMA, contact -hole shrink, PMMA removal, CMOS integration , etching

Directed Self-Assembly (DSA) is today a credible alternative lithographic technology for semiconductor industry [1]. In the coming years, DSA integration could be a standard complementary step with other lithographic techniques (193nm immersion, e-beam, extreme ultraviolet). Its main advantages are a high pattern resolution (down to 10nm), a capability to decrease an initial pattern edge roughness [2], an absorption of pattern guide size variation, no requirement of a high-resolution mask and can use standard fab-equipment (tracks and etch tools). The potential of DSA must next be confirmed viable for high volume manufacturing. Developments are necessary to transfer this technology on 300mm wafers in order to demonstrate semiconductor fab-compatibility [3-7]. The challenges concern especially the stability, both uniformity and defectivity, of the entire process, including tools and Blok Co-Polymer (BCP) materials. To investigate the DSA process stability, a 300mm pilot line with DSA dedicated track (SOKUDO DUO) is used at CEALeti. BCP morphologies with PMMA cylinders in a PS matrix are investigated (about 35nm natural period). BCP selfassembly in unpatterned surface and patterned surface (graphoepitaxy) configurations are considered in this study. Unpatterned configuration will initially be used for process optimization and fix a process of record. Secondly, this process of record will be monitored with a follow-up in order to validate its stability. Steps optimization will be applied to patterned surface configurations (graphoepitaxy) for contact hole patterning application. A process window of contact hole shrink process will be defined. Process stability (CD uniformity and defectivity related to BCP lithography) will be investigated.

International audience; We report the increased crystallization of poly(3-hexylthiophene) (P3HT) in the donor-acceptor mixture of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) with P3HT by the addition of a block copolymer, P3HT-b-PI, where PI refers to polyisoprene. The photovoltaic performance of devices created using this blend is markedly improved by the addition of the diblock copolymer. We have characterized the structure of thin films of the P3HT-b-PI containing mixtures using optical microscopy, scanning force microscopy, UV-vis absorption spectroscopy, neutron reflectometry, and grazing incidence X-ray diffraction (GIXD). The GIXD data provide the information on the crystallinity of the films, the absorption data were used to confirm that the addition of the diblock was responsible for the increase in crystallization, neutron reflectometry data reveal a PCBM-rich region near the hole injection layer, and the two microscopy techniques revealed the structural effect of the crystallization at the surface of the films.

International audience; Poly(styrene)-block-poly(methylmethacrylate) (PS-b-PMMA) block-copolymers (BCP) systems synthesized on an industrial scale and satisfying microelectronic's requirements for metallic contents specifications are studied in terms of integration capabilities for lithographic applications. We demonstrate in particular that this kind of polymer can efficiently achieve periodic features close to 10 nm. These thin films can be transferred in various substrates through dry-etching techniques. The self-assembly optimization for each polymer is first performed on free-surface, leading to interesting properties, and the changes in self-assembly rules for low molecular-weight polymers are investigated and highlighted through different graphoepitaxy approaches. The improvements in self-assembly capabilities toward low periodic polymers, as well as the broad range of achievable feature sizes, make the PS-b-PMMA system very attractive for lithographic CMOS applications. We conclude by showing that high-chi polymer materials developed in Arkema's laboratories can be efficiently used to reduce the pattern's size beyond the ones of PS-b-PMMA based BCP's capabilities. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)

We focus on the directed self-assembly (DSA) for contact hole (CH) patterning application using polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymers (BCPs). By employing the DSA planarization process, we highlight the DSA advantages for CH shrink, repair, and multiplication, which are extremely needed to push forward the limits of currently used lithography. Meanwhile, we overcome the issue of pattern density-related defects that are encountered with the commonly used graphoepitaxy process flow. Our study also aims to evaluate the DSA performances as functions of material properties and process conditions by monitoring main key manufacturing process parameters: CD uniformity (CDU), placement error (PE), and defectivity [hole open yield (HOY)]. Concerning process, it is shown that the control of surface affinity and the optimization of self-assembly annealing conditions enable significant enhancement of CDU and PE. Regarding material properties, we show that the best BCP composition for CH patterning should be set at 70/30 of PS/PMMA total weight ratio. Moreover, it is found that increasing the PS homopolymer content from 0.2% to 1% has no impact on DSA performances. Using a C35 BCP (cylinder-forming BCP of natural period L0=35 nm), good DSA performances are achieved: CDU-3σ=1.2 nm, PE-3σ=1.2 nm, and HOY=100%. Finally, the stability of DSA process is also demonstrated through the process follow-up on both patterned and unpatterned surfaces over several weeks.

Overcoming the optical limitations of 193nm immersion lithography can be achieved using Directed Self Assembly (DSA) of block-copolymers (BCPs) as a low-cost and versatile complementary technique. The goal of this paper is to investigate the potential of DSA to address line and space (L/S) high resolution patterning by performing the density multiplication of lines with the graphoepitaxy approach. As surface affinity is a key parameter in self-assembly, three variations, or "flavors", of DSA template affinity are investigated regarding several success criteria such as morphology control or defectivity. More precisely, both the methodology to register DSA defects and the impact of process parameters on defectivity are detailed. Using the 300mm pilot line available in LETI and Arkema’s advanced materials, we investigate process optimization of DSA line/space patterning of a 38nm period lamellar PS-b-PMMA BCP (L38). For this study, our integration scheme, depicted in figure 2-1, is based on BCP self-assembly inside organic hard mask guiding patterns obtained using 193i nm lithography. Defect analysis coupled with the fine tuning of process parameters (annealing, brush material) provided the optimum conditions for the L38 self-assembly. Using such conditions, DSA using the three affinity flavors is investigated by means of SEM top-view and cross-section review. Lithographic performances of one selected flavor are then evaluated with the comparison of Process Windows (PWs) function of either commensurability, morphology or LWR. This work is a first step in finding the best process for an industrial graphoepitaxy approach.

International audience; Herein we propose an approach toward the optimization of the photovoltaic performance of bulk heterojunctions by tuning the composition of the active layer with respect to the molecular weight of the semiconducting polymer. We used a poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blend as a typical system and varied the molecular weight of the P3HT semiconducting polymer in order to determine its influence on the bulk heterojunction morphology as well as on the optoelectronic characteristics of the device. We have systematically mapped out the phase diagram for different molecular weight P3HTs blended with PCBM and observed the presence of a eutectic composition, which shifts to higher content of P3HT for lower molecular weight P3HTs. This shift inherent to the P3HT molecular weight is also apparent in the photovoltaic performance as the eutectic composition corresponds to the best of the photovoltaic properties. The P3HT molecular weight dependence of the eutectic composition is due to the molecular weight dependence of the P3HT crystallization behavior, which leads to dramatic morphological changes of the bulk heterojunction.

International audience; We show that the production and the geometrical shape of complex polymersomes can be predicted by varying the flow rates of a simple microdevice using an empirical law which predicts the droplet size. This device is constituted of fused silica capillaries associated with adjusted tubing sleeves and T-junctions. Studying the effect of several experimental parameters, double emulsions containing a controlled number of droplets were fabricated. First, this study examines the stability of a jet in a simple confined microfluidic system, probing the conditions required for droplets production. Then, multicompartmental polymersomes were formed, controlling flow velocities. In this work, poly(dimethylsiloxane)-graft-poly(ethylene oxide) (PDMS-g-PEO) and poly(butadiene)-block-poly(ethyleneoxide) (PBut-b-PEO) amphiphilic copolymers were used and dissolved in chloroform/cyclohexane mixture. The ratio of these two solvents was adjusted in order to stabilize the double emulsion formation. The aqueous suspension contained poly(vinyl alcohol) (PVA), limiting the coalescence of the droplets. This work constitutes major progress in, the control of double emulsion formation in microfluidic devices and shows that complex structures can be obtained using such a process.

In the integration flow of directed self-assembly with block copolymers (BCP), the selective removal of one phase of the polymer with respect to the other one is an important step. Different strategies can be implemented such as wet only, exposure, and wet or dry only, each one presenting its highlights and limitations. In this paper, the authors report a wet etching technique allowing an efficient removal of polymethylmethacrylate (PMMA) in PMMA cylinder-forming polystyrene-b-polymethylmethacrylate (PS-b-PMMA) BCP in order to generate contact holes. They confirm that exposure with ultraviolet (UV) light or electron beam is required for PMMA degradation before its complete removal by wet development in acetic acid. A dose-to-clear of 300 mJ/cm2 and 200 μC/cm2 using UV exposure and e-beam exposure, respectively, is demonstrated for a thin BCP film coated on a silicon substrate. Complementary characterizations are employed: by ellipsometry to monitor the BCP thickness, by scanning electron and atomic force microscopies to monitor the surface topography and precisely determine the dose-to-clear. It is also shown that this UV exposure dose is dependent on the materials stack used underneath the BCP film due to the radiation absorption. Furthermore, the authors have investigated the ion implantation in the BCP film with oxygen and hydrogen ions and it seems to be another alternative for PMMA degradation in the wet development approach.

Contact hole (CH) patterning by directed self-assembly (DSA) of polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymers (BCPs) is extensively studied. Based on statistical analysis of defectivity and CD measurements after DSA, a process window (PW) for CH shrink is experimentally determined as a function of guiding pattern dimensions and BCP molecular weights corresponding to BCP natural periods. This PW permits to define the suitable BCP molecular weight and the best guiding CD ranges required to achieve a desired DSA hole CD within a specific tolerance. As an example, for a DSA hole CD targeted at 19.5 nm with 10% tolerance, circular guiding patterns of 52 nm CD with 20% guiding CD latitude are needed using a 35-nm-natural-period cylindrical BCP. Furthermore, it is shown that the CH shrink PW is also dependent on the guiding pattern density and the DSA process conditions such as the self-assembly annealing and the spin coating conditions. The study also highlights an interesting property of commensurability between guiding pattern dimensions and BCP’s natural period that governs the DSA CH patterning for both CH shrink and CH doubling configurations. This permits one to predict the guiding pattern dimensions needed for CH patterning by DSA using a given BCP of known natural period.

This paper introduces line roughness characterization non-straight patterns made of block copolymers (fingerprint patterns). Line Width Roughness have been determined using Power Spectral Density based on a special edge detection developed at CEA-LETI to extract edges contours. We investigated several process parameters impact on LWR such as the degree of polymerization of different BCPs and the impact of UV irradiation on the roughness of the PS block.