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.
Densely patterned contact holes form a key component of integrated circuits, but there are significant challenges to patterning holes with a sub 10-nm radius. The directed self-assembly (DSA) of block copolymers offers a potential solution, where a larger hole is initially patterned and a cylinder forming block copolymer (BCP) is assembled inside. The radius of the inner BCP cylinder can now be used to template the hole radius. It can be particularly challenging to characterize the internal structure of the DSA patterned contact hole, particularly for features such as the residual layer, which may adversely impact the etching process. The high aspect ratio of these features makes top-down characterization nearly impossible, forcing the use of challenging cross-section based approaches.
Critical Dimension small angle X-ray scattering (CDSAXS) offers the possibility of characterizing the internal structure of DSA patterned contact holes. CDSAXS is a variable angle scattering technique which combines measurements from different sample angles to reconstruct the three-dimensional structure of the sample. In this case the scattering yields a two-dimensional pattern, where the off-axis peaks contain additional information about the structure. A model based inverse analysis is then used to fit the scattering and evaluate the structure of the measured target. Contact holes were prepared with a variety of radii and surface treatments in order to evaluate which conditions resulted in optimal assembly of the BCP inside the template. The results demonstrate a correlation between hole radius, surface treatment and residual layer thickness.
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.
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.
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.
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.
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 densityrelated- 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 L0 = 35nm), high DSA performances are achieved: CDU-3σ = 1.2nm, PE-3σ = 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.
Silicon rich silicon oxynitride layers were deposited by ECR-PECVD in order to form silicon nanoparticles upon high
thermal annealing at 1100°C. The effect of the gas precursor type and flows on the atomic composition and the structural properties was assessed by RBS and ERDA analysis as well as by Raman spectroscopy. The morphological and
crystalline properties of the resulting nanoparticles were investigated by TEM analysis. We have found that the silicon
nanoparticules average size and the crystalline fraction depend strongly on the silicon excess in the SiN and SiON layer.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.