PacSurf2024 Session TF-TuP: Thin Films and Surface Modification Poster Session I

In recent years, research and development efforts have focused on the Internet of Things and next-generation communication systems. In these systems, antennas are ideally placed on the surface of the chassis to improve communication characteristics. Hence, to maintain the appealing design features of these devices and systems, optically transparent antennas using transparent conductive films such as indium tin oxide (ITO) are attracting attention. However, there is a trade-off relationship between the optical transmittance and conductivity of transparent conductive films, and it has been challenging to achieve a good balance between the two. Nevertheless, it has been reported that multilayer composites with a dielectric-metal-dielectric (DMD) structure, in which a metallic thin film (e.g., Ag thin film) is introduced as an intermediate layer, can simultaneously achieve high transmittance and conductivity. In this study, we evaluated the transmittance and conductivity of a DMD structure composed of ITO/Ag/ITO with respect to changes in the thickness of Ag in the intermediate layer, and investigated the effects of the transmittance and conductivity on the antenna characteristics following annealing treatment.

ITO/Ag/ITO transparent conducting films were deposited by varying the thicknesses of the Ag and intermediate layers using a facing target sputtering system. The films were annealed at 200–500 °C in air, and their optical transmittance and electrical properties, such as sheet resistance and carrier density, were evaluated. In addition, a monopole antenna of 20 mm length and 5 mm width was fabricated and its radiation efficiency was measured. It was found that with an Ag layer thickness of 7.5 nm, the transmittance and conductivity of the ITO/Ag/ITO film were approximately 69.8% and 7.8 × 10⁵ S/m, respectively. When the transparent conducting film with an Ag film thickness of 7.5 nm was annealed at 200 °C, the transmittance and conductivity of the film increased to approximately 73.4% and 8.5 × 10⁵ S/m, respectively.

The lifetime of plasma torch electrodes is critical, however it is usually limited to 200 hours. Considered in this paper the long life direct current arc plasma torch has the cathode life significantly exceeded 200 hours. To ensure the electrodes’ long life a process of hydrocarbon gas (propane/butane) dissociation in the electric arc discharge is used. In accordance to this method, atoms and ions of carbon from near-electrode plasma deposit on the active surface of the electrodes and form a carbon condensate in the form of carbon nanotubes. It operates as “actual” electrode. To realize aforesaid the construction of a plasma torch using air as the plasma forming gas has been developed and tested. Propane/butane mixture is supplied to the zone of the arc conjunction to the copper water-cooled electrodes (cathode and anode). As a result inside the cathode cavity and internal surface of the anode medium of carbonic gas is formed. Linked with the arc in series, the magnetic coils 3 guaranty stabilization of the discharge on the electrodes. The processes of propane/butane molecules dissociation and carbon atoms ionization start with the rise in temperature. Arisen from ionization positive carbon ions deposit onto the electrodes surface under the influence of near-cathode decline in potential and form coating of the electrode condensate. This coating is “actual” cathode, deterioration of which is compensated by the flow of carbon ions and atoms. The coating thickness depends mainly on ratio of the flows propane/butane and air and the arc current. It is found that when power of the plasma torch was in interval 76–132 kW and propane/butane flow in range of 0.4–0.7 LPM thermal efficiency of the plasma torch reached 90%. At that mass averaged temperature on the exit of the plasma torch increased to 5000 K. The electrode condensate was examined using scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. It is found that the electrode condensate is composite carbonic stuff made of carbon nano-clusters which consists mainly of single and multi-wall carbon nanotubes. The following parameters of the conducting nano carbon deposited at the cathode were determined: chemical composition, wt %: C 96.74–98.47, H 2.26–1.24, Cu 1–0.30; interplanar spacing, nm: 0.333 (100%), 0.207 (1%), 0.168 (5%); apparent density, 1.63 g/cm³; and resistivity, <10^–8 Ohm·m.

Recent advancements in semiconductor applications have emphasized the growing importance of SiN_x due to its exceptional operational reliability.[1,2] In the scaling trends, the need to deposit gate spacers has underscored the significance of SiN_x atomic layer deposition (ALD), which offers uniformity and conformality, andthickness control at the Angstrom level. [3, 4] However, the role of Si precursor chemistry in growth and electrical characteristics of SiN_x films has not been fully explored. Understanding this relationship is crucial, as growth characteristics directly impact the electrical performance and leakage current behavior of SiN_x, which is vital for its effectiveness in electrical insulation applications. This study investigates the relationship between three different Si precursors and the electrical properties of SiN_x films.Three alkyl amine precursors, bis(tertiarybutylamino)silane (BTBAS), bis(diethylamino)silane (BDEAS), and NSi-01 were used for this study. The deposition was done on the substrate temperature of 200 °C with 60 MHz very high frequency (VHF) N₂ plasma as a reactant. Density functional theory (DFT) calculations, Monte Carlo (MC) simulations, and ellipsometry were employed to analyze the growth characteristics during ALD process. Additionally, the film quality evaluation was done by using X-ray photoelectron spectroscopy (XPS), and transmission electron microscope (TEM). The correlation between electrical and growth characteristics was investigated by fabricating and evaluating metal-oxide-semiconductor (MOS) capacitors. This study provides key insights into optimizing precursor selection to enhance device performance, demonstrating how the choice of ligands can significantly impact the leakage characteristics and reliability of SiN_x-based devices.

As the semiconductor industry advances towards complex multilayered devices with smaller features, area-selective atomic layer deposition (AS-ALD), a bottom-up method, has gained significant interest for its capability to enable precise and self-aligned deposition within specified areas, i.e., the growth areas. In this study, we primarily utilized small molecular inhibitors as vapor-phase deactivating agents to non-growth areas, due to their small size, high volatility, and ease of process integration into 3D structured devices. More particularly, this AS-ALD methodology is advantageous for manufacturing high aspect ratio SiO₂/SiN structures in V-NAND, where the reduction in tier size leads to cell-to-cell crosstalk between vertically downscaled SiO₂/SiN stacks. To mitigate this issue, it is essential to apply AS-ALD of SiO₂ thin films on SiO₂ surfaces while preventing deposition on SiN surfaces. For this purpose, we employed a vapor-dosing process using silane-based small molecule inhibitors that chemo-selectively adsorb on -NH terminated surface groups of the SiN surface. Moreover, to further improve deposition selectivity, we periodically introduced a post-atomic layer etching step with atomic scale fidelity after a certain number of ALD SiO₂ cycles, which effectively removed SiO₂ moieties from the SiN surfaces. Finally, we achieved a deposition selectivity greater than ~10 nm on blanket SiO₂ and SiN substrates. The approach we present here contributes to the advancement of the manufacturing process for next-generation bottom-up 3D nanofabrication.

Plasma material process in an organic solution uses the interaction between plasma and solution substances. Plasma generated in the solution occurs a strong discharge through an electrode structure designed for ease of ignition. Therefore, most plasma materials processes conducted in solution have been used to form metal or carbon nanoparticles by erosion of electrodes or carbonization of solutions. Recently, studies have been reported on igniting plasma that limits strong discharges in liquid phases and controlling chemical activity (oxidation, reduction) according to the driving waveform. As a result, this method succeeded in creating π-conjugated polymer film, as well as nanoparticles with the molecular structure of the starting solution.

In this study, we conducted research on controlling properties of conductive polymer films synthesized by the plasma process in organic solution. Plasma characteristics affect the chemical activity of the material and consequently change the properties of the polymer film. Therefore, this process is performed using various driving power conditions to control the plasma characteristics. The electrical and optical characteristics of plasma and the changes in solution are analyzed according to driving power conditions. Moreover, the differences in the properties of conductive polymer films are investigated in detail. Finally, it is confirmed that the conductive polymer synthesized in this method has stable electrical properties in room condition.

Graphene is typically considered to be a nonmagnetic material with long spin lifetime and transport distance. The potential to induce magnetic properties in graphene by various methods has generated significant interest since it would enable the development of novel spintronic devices where charge and spin manipulation could be combined. Recent works have predicted the formation of ferromagnetic order in graphene with point defects or functionalization. Ferromagnetic signals at room temperature have been observed for graphene or graphite with point-defects produced by various methods. However, there are debates on (1) the role of possible contamination and (2) the mechanism responsible for the strong interaction required for the formation of ferromagnetic order. According to a more recent report, point-defects in graphene only produce spinhalf paramagnetism, and the ferromagnetic order observed in previous studies was caused by the presence of small amounts of magnetic impurities. In the case of functionalized graphene, it has been reported that the ferromagnetic order is predicted for the oxidized graphene layer where C atoms have C–OH, C–O–C, or C=O bonds, and for the semi-hydrogenated graphene sheet. Although the existence of ferromagnetic order below 100 K in the n-doped graphene oxide layer has been experimentally confirmed with superconducting quantum interference device measurement, the possibility of magnetic contamination was not examined strictly.

Here, we investigate magnetic properties of graphene oxide flake that have been locally oxidized using atomic force microscopy (AFM) lithography. This approach reduces the possibility of magnetic contamination. Our Raman spectroscopy analysis reveals that the graphene oxide contains crystalline defects or disorders and differs from the pristine graphene in terms of its atomic structure. Using magnetic force microscopy measurements, we observe that the graphene oxide has a net magnetization pointing out of the surface plane. Furthermore, our magneto-optical Kerr effect data show small but clear hysteresis loops with non-zero remanent magnetization. We also conduct x-ray magnetic circular dichroism (XMCD) photoemission electron microscope measurements and identify remarkable asymmetry in carbon K edge spectra, which strongly suggests that the observed ferromagnetic order in the graphene oxide layer is intrinsic. A careful analysis of XMCD signals depending on the oxidized condition reveals the effects of chemical states of carbon atoms on the formation of ferromagnetic order in the graphene oxide.