Seong-Jun Jeong

Soft Graphoepitaxy of Block Copolymer Assembly with Disposable Photoresist Confinement

We demonstrate soft graphoepitaxy of block copolymer assembly as a facile, scalable nanolithography for highly ordered sub-30-nm scale features. Various morphologies of hierarchical block copolymer assembly were achieved by means of disposable topographic confinement of photoresist pattern. Unlike usual graphoepitaxy, soft graphoepitaxy generates the functional nanostructures of metal and semiconductor nanowire arrays without any trace of structure-directing topographic pattern. Our novel approach is potentially advantageous for multilayer overlay processing required for complex device architectures.

One-Dimensional Metal Nanowire Assembly via Block Copolymer Soft Graphoepitaxy

We accomplished a facile and scalable route to linearly stacked, one-dimensional metal nanowire assembly via soft graphoepitaxy of block copolymers. A one-dimensional nanoscale lamellar stack could be achieved by controlling the block copolymer film thickness self-assembled within the disposable topographic confinement and utilized as a template to generate linear metal nanowire assembly. The mechanism underlying this interesting morhpology evolution was investigated by self-consistent field theory. The optical properties of metal nanowire assembly involved with surface plasmon polariton were investigated by first principle calculations.

Surface Energy Modification by Spin-Cast, Large-Area Graphene Film for Block Copolymer Lithography

We demonstrate a surface energy modification method exploiting graphene film. Spin-cast, atomic layer thick, large-area reduced graphene film successfully played the role of surface energy modifier for arbitrary surfaces. The degree of reduction enabled the tuning of the surface energy. Sufficiently reduced graphene served as a neutral surface modifier to induce surface perpendicular lamellae or cylinders in a block copolymer nanotemplate. Our approach integrating large-area graphene film preparation with block copolymer lithography is potentially advantageous in creating semiconducting graphene nanoribbons and nanoporous graphene.

Ultralarge-area block copolymer lithography enabled by disposable photoresist prepatterning.

We accomplished truly scalable, low cost, arbitrarily large-area block copolymer lithography, synergistically integrating the two principles of graphoepitaxy and epitaxial self-assembly. Graphoepitaxy morphology composed of highly aligned lamellar block copolymer film that self-assembled within a disposable photoresist trench pattern was prepared by conventional I-line lithography and utilized as a chemical nanopatterning mask for the underlying substrate. After the block copolymer film and disposable photoresist layer were removed, the same lamellar block copolymer film was epitaxially assembled on the exposed chemically patterned substrate. Highly oriented lamellar morphology was attained without any trace of structure directing the photoresist pattern over an arbitrarily large area.

Flexible and transferrable self-assembled nanopatterning on chemically modified graphene.

Figure 1 . (a) Transferrable self-assembled nanopatterning procedure. See text for details. SEM images of lamellar BCP nanotemplates transferred onto (b) right angled fracture edge of silicon wafer and (c) microscale ZnO hillock. (d) Photograph and (e) SEM image of cylindrical BCP nanotemplates transferred onto syringe needle surface. Block copolymer (BCP) self-assembly generates dense and periodic nanodomains, whose characteristic dimensions can be as small as 3 nm. [ 1–3 ] Such self-assembly in thin fi lms can create two-dimensional lithographic nanotemplates with pattern precision barely attainable by other methods. [ 4–9 ] Substantial progress in the synergistic integration of BCP selfassembly with e-beam lithography and ArF or other photolithography, demonstrates that this self-assembly based nanopatterning is a promising technology to complement the resolution limit of a conventional lithography. [ 10–20 ] Meanwhile, BCP self-assembled nanopatterning has been regarded as an intrinsic two-dimensional patterning method specifi cally useful for hard and fl at inorganic substrates. [ 4 , 21 ] The wellestablished processing steps involved with the formation of uniform thickness, ultrathin (typically less than 100 nm) BCP fi lm via spin casting and subsequent thermal/solvent annealing are generally considered incompatible to three-dimensional geometries or conventional fl exible polymer substrates with low chemical/thermal stability and surface roughness typically larger than nanoscale. In this work, mechanically robust but compliant chemically modifi ed graphene (CMG) fi lm [ 22 , 23 ] is introduced as a transferrable and disposable substrate for the self-assembled nanopatterning of nonplanar, fl exible, and even multistack device oriented structures. Taking advantage of the high chemical/ thermal stability, genuine atomic scale fl atness, and mechanical robustness with compliance, graphene based materials can be excellent substrates for nanopatterning (Supporting Information, Table S1). [ 24 , 25 ] While pristine graphene has a low surface energy, CMG prepared via

Improvement of the Morphological Stability by Stacking RuO2 on Ru Thin Films with Atomic Layer Deposition

Stacked RuO 2 /Ru structures were produced by atomic layer deposition (ALD) using an alternating supply of his(ethylcyclopentadienyl)ruthenium [Ru(EtCp) 2 ] and O 2 gas at a deposition temperature of 270°C. The type of the deposited film, either Ru or RUO 2 , was controlled by the total pressure in the ALD system as well as the ratio of the adsorbed Ru(EtCp) 2 to the partial pressure of O 2 in the following O 2 gas pulse. The resistivity of the deposited Ru and RuO 2 thin films was about 15 and 70 μΩ cm, respectively. The surface morphology of Ru films annealed in O 2 ambient was seriously degraded by surface oxidation. Moreover, RUO 2 films were also agglomerated due to the residual stress releasing during the annealing process. However, a stacked RUO 2 /Ru structure produced using ALD maintained a smooth surface even at an annealing temperature of 800°C in ambient O 2 . Auger electron spectroscopy confirmed that the stacked RuO 2 /Ru structure successfully blocked oxygen and silicon diffusion. Therefore, the stacked RuO 2 /Ru structure produced by ALD is suitable for use as the bottom electrode material for high dielectric applications.

Improvement of Copper Diffusion Barrier Properties of Tantalum Nitride Films by Incorporating Ruthenium Using PEALD

Ru-incorporated TaN (Ru-TaN) films were investigated as a Cu diffusion barrier material. Ru-TaN films were prepared by sequential deposition of Ru and TaN using plasma-enhanced atomic layer deposition (PEALD). The film composition was controlled by the number of Ru unit cycles. While the resistivity of Ru-TaN films was increased abruptly at low Ru composition (∼0.06), the resistivity of Ru-TaN films was decreased gradually as the Ru composition increased after that composition. The crystal structures of Ru-TaN films were amorphous at the Ru composition range from 0.19 to 0.52 due to disturbance of grain growth. However, the Ru-TaN films had TaN-like structure below this range and Ru-like structure above this range. The amorphous Ru-TaN films had nanocrystallite embedded structure in an amorphous matrix. This amorphous Ru-TaN barrier showed a better Cu diffusion barrier property (∼700°C) than the TaN barrier (∼650°C) because the Cu diffusion through the grain boundary was suppressed by the amorphization. In addition, the Ru-TaN barrier exhibited good adhesion to both Cu and SiO 2 .

3D Tailored Crumpling of Block-Copolymer Lithography on Chemically Modified Graphene

Novel 3D self-assembled nanopatterning is presented via tailored crumpling of chemically modified graphene. Block-copolymer self-assembly formed on a layer of chemically modified graphene provides highly dense and uniform 2D nanopatterns, and the controlled crumpling of the chemically modified graphene by mechanical instabilities realizes the controlled 3D transformation of the self-assembled nanopatterns.

Flash Light Millisecond Self-Assembly of High χ Block Copolymers for Wafer-Scale Sub-10 nm Nanopatterning

One of the fundamental challenges encountered in successful incorporation of directed self-assembly in sub-10 nm scale practical nanolithography is the process compatibility of block copolymers with a high Flory-Huggins interaction parameter (χ). Herein, reliable, fab-compatible, and ultrafast directed self-assembly of high-χ block copolymers is achieved with intense flash light. The instantaneous heating/quenching process over an extremely high temperature (over 600 °C) by flash light irradiation enables large grain growth of sub-10 nm scale self-assembled nanopatterns without thermal degradation or dewetting in a millisecond time scale. A rapid self-assembly mechanism for a highly ordered morphology is identified based on the kinetics and thermodynamics of the block copolymers with strong segregation. Furthermore, this novel self-assembly mechanism is combined with graphoepitaxy to demonstrate the feasibility of ultrafast directed self-assembly of sub-10 nm nanopatterns over a large area. A chemically modified graphene film is used as a flexible and conformal light-absorbing layer. Subsequently, transparent and mechanically flexible nanolithography with a millisecond photothermal process is achieved leading the way for roll-to-roll processability.

Improvement of Morphological Stability of PEALD-Iridium Thin Films by Adopting Two-Step Annealing Process

Plasma-enhanced atomic layer deposition PEALD of iridium Ir films was investigated using Ir EtCp COD and NH3 plasma. Deposited Ir films had smooth surface and preferred 111 orientation. After simple annealing in ambient oxygen, surface roughening occurred because Ir was oxidized above 550°C, and the oxidized IrO2 during temperature rising was reduced to Ir at 850°C. However, by adopting two-step annealing, Ir films showed excellent thermal and morphological stability at 850°C. During two-step annealing at 850°C, the oxidation during temperature rising was suppressed by supplying argon, and annealing in ambient oxygen progressed after the temperature reached 850°C.