Patterning surface with structural DNA origami mask presents a major interest for nanolithography due to its modularity and high ability to achieve a high resolution with 3-5 nm.
In this paper, we demonstrate a sub-ten-nanometer lithography process using anhydrous HF vapor into a SiO2 substrate (figure 1). After optimizing rinsing conditions on SiO2 substrate and HF etching process, we reach a high density (<20 nm pitch) and high resolution (~10 nm CD) patterned surface with a fast etching rate of 0.2 nm.s-1. The resulting SiO2 patterns are used as hard mask in HBr/O2 plasma of Si substrate. Origami pattern features are conserved: lateral dimensions, morphology and structure. For the first time, we developed a high resolution (~10 nm) and high contrast (~65 nm) transfer of patterns into Si substrate.
We will highlight the challenges brought by this new technology and demonstrate the feasibility to control this patterning technique. AFM technique has been previously tested to confirm the pattern fidelity. Using all the available imaging capabilities on the CDSEM, we will establish the best method for each layer to achieve the precision required for the targeted nodes of this technology.
Beyond the resolution capabilities, the precise placement of the DNA pattern on the substrate is investigated. Based on a pre-patterning step using the nanoimprint technology, the affinity of the DNA with respect to the substrate is locally modified and its influence is analyzed.
Thus, DNA origami appears like a promising approach for emerging and engineering of hard mask for patterning.
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.
In this paper the bias table models for the wafer scale SmartNIL™ technology are addressed and validated using complete Scanning Electron Microscopy (SEM) characterizations and polynomial interpolation functions. Like the other nanoimprint lithography (NIL) technics, this replication technology is known to induce Critical Dimension (CD) variations between the master and the imprint, due to polymer shrinkage, soft stamp deformation or thermal expansion. The bias between the former and final object follows peculiar rules which are specific to this process. To emphasis these singularities, Critical Dimension (CD) uniformity analyses were analyzed onto 200 mm wafers imprinted with the HERCULES® NIL equipment platform. Dedicated masters were manufactured to capture the process signatures: horizontal and vertical line arrays, local densities ranging from 0.1 to 0.9 and minimum CD of 250 nm. The silicon masters were manufactured with 248 optical lithography and dry etching and treated with an anti-sticking layer from Arkema. CD measurements were made for the master and the replicates on 48 well selected features to build interpolations. The bias table, modelled by polynomial functions with a degree of 5 for the density and a degree of 3 for the CD, are compared between horizontal and vertical features, and between the center and the edge of the wafers. Finally the focus is made on the validation of the interpolations by comparing the computed bias and the experimental data.
In this paper the bias table models and rules-based correction strategies for the wafer scale nanoimprint lithography (NIL) technology are addressed using complete Scanning Electron Microscopy (SEM) characterizations. This replication technology is known to induce Critical Dimension (CD) variations between the master and the imprint, due to polymer shrinkage, soft stamp deformation or thermal expansion. The bias between the former and final object follows peculiar rules which are specific to this process. To emphasis these singularities, Critical Dimension (CD) uniformity analyses are performed onto 200 mm wafers imprinted with the HERCULES® NIL equipment platform. Dedicated masters were manufactured which have horizontal and vertical line arrays, with local densities ranging from 0.1 to 0.9, with a minimum CD of 250 nm. The silicon masters were manufactured with 248 optical lithography and dry etching and treated with an anti-sticking layer from Arkema. CD measurements were made for the master and the replicates on 48 well selected features to build an interpolation. The data revealed that the CD evolutions can be modelled by polynomial functions with respect to the density, the CD and the orientation (vertical or horizontal) on the GDS. Finally the focus is made on the dependence of the design rules with respect to the position on the master, and it opens the discussion on the strategies for efficient wafer scale corrections for the nanoimprint soft stamp technologies.
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.
KEYWORDS: Directed self assembly, Lithography, Line width roughness, Nanoimprint lithography, Semiconducting wafers, Etching, Electron beam lithography, System on a chip, Critical dimension metrology, Photoresist processing
In the lithography landscape, EUV technology recovered some credibility recently. However, its large adoption remains uncertain. Meanwhile, 193nm immersion lithography, with multiple-patterning strategies, supports the industry preference for advanced-node developments. In this landscape, lithography alternatives maintain promise for continued R&D. Massively parallel electron-beam and nano-imprint lithography techniques remain highly attractive, as they can provide noteworthy cost-of-ownership benefits. Directed self-assembly lithography shows promising resolution capabilities and appears to be an option to reduce multi-patterning strategies. Even if large amount of efforts are dedicated to overcome the lithography side issues, these solutions introduce also new challenges and opportunities for the integration schemes.
In this paper the rules-based correction strategies for the nanoimprint lithography (NIL) technology are addressed using complete Scanning Electron Microscopy (SEM) characterizations. Performed onto 200 mm wafers imprinted with the HERCULES NIL equipment platform, Critical Dimension (CD) uniformity analyses are used to measure the evolution of lines and spaces features dimensions from the master to 50 consecutive imprints. The work brings focus on sub micrometer resolution features with duty cycles from 3 to 7. The silicon masters were manufactured with 193 optical lithography and dry etching and were fully characterized prior to the imprint process. Repeatability tests were performed over 50 wafers for two different processes to collect statistical and comparative data. The data revealed that the CD evolutions can be modelled by quadratic functions with respect to the number of imprints and feature dimension (CD and pitch) on the master. These models are used to establish the rules-based corrections for lines arrays in the scope of nanoimprint master manufacturing, and it opens the discussion on the process monitoring through metrology for the nanoimprint soft stamp technologies.
In this paper a first Critical Dimension (CD) uniformity assessment onto 200 mm wafers printed with the SmartNILTM technology available in the HERCULES® NIL equipment platform is proposed. The work brings focus on sub micrometer resolution features with a depth between 220 and 433 nm. The silicon masters were manufactured with 193 optical lithography and dry etching. A complete Scanning Electron Microscopy (SEM) characterizations were performed over the full masters surface prior to the imprint process. Repeatability tests were performed over 25 wafers first and then on 100 wafers to collect statistics and the CD distribution within a wafer and also wafer to wafer. The data revealed that the CD is evolving imprint after imprint and an explanation based on polymer shrinkage is proposed.
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