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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.

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.

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; 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.

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.