In-Soo Park's research while affiliated with Sungkyunkwan University and other places

This study examined imprint lithography with a two-step Ni stamp to solve the laser process problems and simultaneously form a blind via and layer pattern. The Ni stamp was fabricated by electroplating on a dry-etched Si mold, made from a SOI (silicon on insulator) wafer, and pattern replication. For the pattern transfer of the Ni stamp, hot embossing was performed on SU8-coated BT and Si wafer substrates. The residual layer was of a uniform thickness with an embossed shape of acceptable squareness.

Co-Pt alloy thin films were galvanostatically electrodeposited from an aqueous electrolyte consisting of Co sulphamate and PtP salt. A 30-nm-thick Ru buffer layer was used to enhance the perpendicular magnetic anisotropy. The Co-Pt thin films on a Ru buffer layer exhibited high perpendicular magnetic anisotropy. They also exhibited a as high out-of-plane coercivity and a high squareness of up to 6414 Oe and 0.86, respectively, without any heat treatment. The intrinsic perpendicular magnetic anisotropy constant, Ku, of the Co-Pt alloy obtained using a torque magnetometer was 8.3 × 106 erg/cm3. The composition of the electrodeposited Co-Pt alloy was Co-25.19 at.% Pt corresponding to the CosPt phase. According to the transmission electron microscopy (TEM) analysis, the out-of-plane coercivity and squareness increased significantly due to the growth of physically isolated columnar grains with the c-axis perpendicular to the film plane.

Ta/Ta–N multilayer has been developed to control temperature coefficient of resistance (TCR) in a thin-film embedded resistor with the incorporation of Ta layer (+ TCR) inserted into Ta–N layers (− TCR). Electrical and structural properties of sputtered Ta, Ta–N and the multilayer films were investigated. The stable resistivity value of 0.0065 Ω·cm in β-Ta film was obtained, and phase change from fcc-TaN to orthorhombic Ta3N5 in Ta–N films was observed at nitrogen partial pressure of 22%. The multilayer of Si/Ta(60 nm)/Ta3N5(104 nm)/Ta(60 nm)/Ta3N5(104 nm) showed TCR value of − 284 ppm/K, where TCR of Ta was − 183 ppm/K and that of Ta3N5 was − 3193 ppm/K.

In this study, we investigate as-deposited Ta3N5–Ag nanocomposite thin films with near-zero temperature coefficients of resistance (TCRs) that are fabricated by a reactive co-sputtering method; these films can be used in thin-film embedded resistors. In these films, the TCR approaches zero due to compensation between Ag (+TCR) and Ta–N (−TCR) at resistivities higher than 0.005 Ω-cm.Taking into account the fact that Ag counterbalances the resistivity of the Ta3N5–Ag thin film, we performed reactive co-sputtering at a nitrogen partial pressure of 55%, corresponding to a resistivity of 0.384 Ω-cm. The resistivity and power density changed, respectively, from 1.333 Ω-cm and 0.44 W/cm2 for silver to 0.0059 Ω-cm and 0.94 W/cm2 for the Ta3N5–Ag thin film. A near-zero TCR of + 34 ppm/K was obtained at 0.94 W/cm2 in the Ta3N5–Ag thin film without heat treatment.