Directed Self-Assembly (DSA) of block-copolymers, which is an affordable, simple and versatile lithography technique, is still highly investigated as a potential solution for the next generation node in the CMOS industry. DSA graphoepitaxy approach provides physical confinement between two “sidewalls” of fixed surface energy, which will generate well defined line/space structures with a variety of block copolymer materials and process environment [1,2,3]. However, most pilot-line compatible processes found in literature use Electron Beam Lithography (EBL) to generate the guiding structures because non-preferential grafted polymer layers can be incorporated between the HSQ resist (oxide guiding templates) and an inorganic transfer layer [4]. When using a 193nm-immersion lithography, such integration flow is not advised because the 193nm resists are acrylate-based resists that flow during the different annealing steps (CD uniformity and roughness performances impacted). Guiding templates made of standard immersion “hardmask” stack material with proper surface functionalization (sidewalls attractive to one block, bottom non-preferential) are rare.

Context. Within the framework of the second-generation instrumentation of the Very Large Telescope Interferometer of the European Southern Observatory we have developed the four-telescope beam combiner in integrated optics. Aims. We optimized the performance of such beam combiners, for the first time in the near-infrared K band, for the GRAVITY instrument dedicated to the study of the close environment of the galactic centre black hole by precision narrow-angle astrometry and interferometric imaging. Methods. We optimized the design of the integrated optics chip and the manufacturing technology as well, to fulfil the very demanding throughput specification. We also designed an integrated optics assembly able to operate at 200 K in the GRAVITY cryostat to reduce thermal emission. Results. We manufactured about 50 beam combiners by silica-on-silicon etching technology. We glued the best combiners to single-mode fluoride fibre arrays that inject the VLTI light into the integrated optics beam combiners. The final integrated optics assemblies have been fully characterized in the laboratory and through on-site calibrations: their global throughput over the K band is higher than 55% and the instrumental contrast reaches more than 95% in polarized light, which is well within the GRAVITY specifications. Conclusions. While integrated optics technology is known to be mature enough to provide efficient and reliable beam combiners for astronomical interferometry in the H band, we managed to successfully extend it to the longest wavelengths of the K band and to manufacture the most complex integrated optics beam combiner in this specific spectral band.

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).

Incorporated in relevant design of guiding templates, DSA (Direct Self Assembly) patterning offers a cost-effective manufacturing method to support pattern shrink for advanced technology nodes. The physical characteristics of the BCP moieties and the self-assembly process, pose unique 3D metrology challenges. Pattern fidelity issues of DSA caused by dislocations, forms residual later that can impact pattern fidelity after Etch. Addressing this challenge can assist the R&D groups to monitor material and process quality to meet patterning specifications.In this paper, we highlight the usage of BSE (Back Scattered Electron) metrology as an innovative approach to characterize the DSA process. Experimental data demonstrate the possibility to characterize the polymer residual layer quality and even assess its thickness for the pattern etch transfer. The quality of the information brought by the BSE imaging make it a must-have to quantify the bottom opening for processed of DSA techniques of pitch multiplication and shrink, from which are not visible with conventional SEM images.

PS-b-PMMA block copolymer is a well-known DSA material, and there are many DSA patterning methods that make effective use of such 1st generation materials. Consequently, the variety of patterning methods opens a wide array of possibilities for DSA application[1-4]. Last year, during the inaugural International DSA Symposium, researchers and lithographers concurred on common key issues for DSA patterning methods such as: defect density, LWR, placement error, etc. Defect density was specifically expressed as the biggest obstacle for new processes. Coat-Develop track systems contribute to the DSA pattern fabrication, and also influence the DSA pattern performances[ 4]. In this study, defectivity was investigated using an atmosphere-controlled chamber on the SOKUDO DUO track. As an initial step for expanding the DSA process window, fingerprint patterns were used for various atmospheric conditions during DSA self-assembly annealing. In this study, we will demonstrate an improved DSA process window, and then we will discuss the mechanism for this atmospheric effect.

Through three collaborative R&D programs, IDEAL for Directed Self-Assembly Lithography, IMAGINE for Massively Parallel Electron Beam Lithography and INSPIRE for NanoImprint Lithography, CEA-LETI is currently assessing and boosting the development of these alternative technologies through strategic partnerships and innovative mix of them. This paper will present the latest process developments achieved on both chemically and non-Chemically Amplified Resist exposed with a low accelerating voltage (5 kV) exposure platform developed by Mapper Lithography. Several approaches will be presented to manage the Resolution-Sensitivity-Line Width Roughness challenge as well as the etching transfer in the underneath stacks required at the 28 nm node. For the Directed Self-Assembly (DSA) of Block Copolymers (BCP) patterning solution, even if it is considered as a promising patterning solutions due to its simplicity, low cost of processing and capability to generate high density patterns, some challenges (DSA-friendly design, low defectivity and accurate placement error) still need to be addressed for a complete adoption of DSA in manufacturing. We propose to discuss the advanced integration flows using DSA of block copolymer for PS-PMMA materials, like "DSA planarization" approach and also surface guide affinity tuning. Then, NIL wafer scale technology will be assessed thought CDU and printed resist feature height measurements. These result will underline the key process parameters that will define the integration scheme of such technology in high volume manufacturing. This paper will also highlight the specific metrology requirements and method needed to properly evaluate such patterning technology.

Directed Self Assembly (DSA) of block-copolymers (BCPs) used as a complementary technique to the 193nm immersion lithography has demonstrated sub-10nm node applications in both via and line/space patterning. We propose however to study the performance of graphoepitaxy which allows DSA with thicker initial BCP layer, higher multiplication factors and stronger orientation control of lamellae. The aim of this work is to use the 300mm pilot line available at LETI and Arkema’s advanced materials to evaluate the performances of a novel graphoepitaxy process based on the work on a 38nm period lamellar PS-b-PMMA (L38) reported before.

In this paper, we focus on the directed-self-assembly (DSA) application for contact hole (CH) patterning 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 DSA performances as function 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 to significantly enhance CDU and PE. Regarding materials 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 L-0 = 35nm), high DSA performances are achieved: CDU-3 sigma = 1.2nm, PE-3 sigma = 1.2nm and HOY = 100%. The stability of DSA process is also demonstrated through the process follow-up on both patterned and unpatterned surfaces over several weeks. Finally, simulation results, using a phase field model based on Ohta-Kawasaki energy functional are presented and discussed with regards to experiments.

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 L-0 = 35 nm), good DSA performances are achieved: CDU-3 sigma = 1.2 nm, PE-3 sigma = 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. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

Density multiplication and contact shrinkage of patterned templates by directed self-assembly (DSA) of block copolymers (BCP) stands out as a promising alternative to overcome the limitations of conventional lithography. The main goal of this paper is to investigate the potential of DSA to address contact and via levels patterning with high resolution by performing either CD shrink or contact multiplication. Different DSA processes are benchmarked based on several success criteria such as: CD control, defectivity (missing holes) as well as placement control. More specifically, the methodology employed to measure DSA contact overlay and the impact of process parameters on placement error control is detailed.Using the 300mm pilot line available in LETI and Arkema's materials, our approach is based on the graphoepitaxy of PS-b-PMMA block copolymers. Our integration scheme, depicted in figure 1, is based on BCP self-assembly inside organic hard mask guiding patterns obtained using 193i nm lithography. The process is monitored at different steps: the generation of guiding patterns, the directed self-assembly of block copolymers and PMMA removal, and finally the transfer of PS patterns into the metallic under layer by plasma etching.Furthermore, several process flows are investigated, either by tuning different material related parameters such as the block copolymer intrinsic period or the interaction with the guiding pattern surface (sidewall and bottom-side affinity). The final lithographic performances are finely optimized as a function of the self-assembly process parameters such as the film thickness and bake (temperature and time).Finally, DSA performances as a function of guiding patterns density are investigated. Thus, for the best integration approach, defect-free isolated and dense patterns for both contact shrink and multiplication (doubling and more) have been achieved on the same processed wafer.These results show that contact hole shrink and multiplication approach using DSA is well compatible with the conventional integration used for CMOS technology.

The semiconductor devices dimensions continue to shrink to keep up with the ITRS roadmap. Due to delay and extensive cost of EUV for 14nm technology node and beyond, the directed self assembly (DSA) process has great potential for extending optical lithography, and enables to reduce the critical dimension (CD) and pitch of the final feature. After the recent implementation of DSA processes in 300mm clean room environment, it is now time to move to the forward maturity step and demonstrate process stability through time. This study investigates the potential of DSA for contact hole shrink patterning using poly(styrene-block-methyl methacrylate) (PS-b-PMMA) di-block copolymers to target contact holes CD down to 15 nm. Based on the 300mm pilot line available at LETI, the DSA manufacturability is considered through different criteria to achieve high resolution and pattern density multiplication, at a low cost in fully 300mm wafers production line. The DSA process flow performance based on grapho-epitaxy approach is controlled after each step to follow the thicknesses of random and BCP materials supplied by ARKEMA. Moreover, the natural period of block copolymers and CD uniformity on free surface are also measured and defectivity is evaluated after etch transfer by image treatment. The thermal budget of DSA of both random and block copolymers have been evaluated to define optimum conditions. The paper has shown that UV exposure prior to PMMA wet development improves PMMA degradation to enable complete removal by wet development in acetic acid. DSA process for contact hole shrink patterning has shown final contact holes with an average CD of 21nm and intra-wafer CD uniformity of 1.1nm with an open yield of more than 99.9%. (C) 2014 The Japan Society of Applied Physics

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.

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. L-0 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.

This work deals with the development of resistive memories based on oxides and their integration into the interconnection levels. The paper is focused on the screening of different dielectric oxides (metallic or not) showing resistive switching properties in order to lead to the highest performance resistive memories. Nickel oxide which is the most studied material in the literature is compared to other binary metallic oxides. In parallel, cells with silicon based dielectrics and Cu electrodes were developed. Electrical results allowed a comparison between the 3 main mechanisms observed in resistive memories based on oxides. Moreover, a specific resist flowing process and ion beam etching were optimized in order to limit metallic residues on memory cell side walls and prevent short-circuiting.