Hideki Ohkawa

Microstructures of ITO films deposited by d.c. magnetron sputtering with H2O introduction

ITO films were deposited by d.c. magnetron sputtering with/without H2O introduction. The structural and optoelectrical properties of the films were analyzed in detail. The films deposited with H2O introduction exhibited an entirely amorphous structure, whereas the as-deposited films deposited without H2O introduction exhibited a polycrystalline In2O3 structure. The amorphous ITO films deposited under the high H2O partial pressure were confirmed to contain a much higher concentration of hydrogen inside the films by secondary ion mass spectroscopy, which remained after post-annealing at 350 °C. The crystallization temperature of the films subjected to post-annealing was increased to higher than 220 °C. These stable amorphous ITO films had a wet-etching rate in oxalic acid solution two orders of magnitude higher than that of the films deposited without H2O introduction.

Double-Level Cu Inlaid Interconnects with Simultaneously Filled Via Plugs

A double-level Cu interconnection process for lower submicron generation ULSIs was developed. Cu interconnects were successfully formed by Cu/WSiN sputtering, XeCl excimer laser annealing and Cu/WSiN chemical mechanical polishing. The composition of the WSiN barrier metal was optimized to WSi0.6N and the diffusion barrier capability was confirmed by physical analyses and electrical measurements. The electrical resistivity of the inlaid Cu was 1.9±0.1 µ Ωcm and contact resistivity between the first-level Cu and the second-level Cu was (1.54–5.78)×10-9 Ωcm2. The electromigration lifetime of laser-annealed Cu/WSiN wiring was found to be one order of magnitude longer than that of previously reported Cu interconnects. The activation energy for electromigration was determined to be 1.1 eV.

Tellurium-carbon (TeC:H) films for a write-once read many (WORM) optical disk memory

Abstract A tellurium-carbon (TeC:H) film was deposited by the reactive sputtering of a Te target in an atmosphere containing methane. Raman spectroscopy. X-ray photoelectron spectroscopy (XPS), and FT-IR absorption spectroscopy have shown that the chemical state of carbon in the TeC:H film is not amorphous carbon but rather sp 3 -hybridized hydrocarbon. Thermal decomposition of the TeC:H film produced sp 2 -hybridized hydrocarbon gas, which was analyzed by FT-IR/TG (thermogravimetry) measurements. Raman and FT-IR spectroscopies have supported the view that the structure of the TeC:H film is a composite structure consisting of amorphous tellurium and hydrocarbon fragments produced in methane plasma. The ablative optical recording sensitivity of the TeC:H film has been confirmed to be superior to that of a Te film, and its long archival and shelf lives have been recognized by accelerated aging tests. The recording sensitivity of the co-sputtered film consisting of tellurium and graphite carbon was found to be insufficient compared with the sensitivity of the Te film.

X-ray photoelectron and vibrational spectroscopic studies of TeC:H films for optical disk memory

The valence band spectrum of a TeC:H film was found to be essentially the same as that of amorphous elemental tellurium using X-ray photoelectron spectroscopy. Raman and Fourier transform far-IR spectra were examined based on the phonon density of states for tellurium, and the far-IR peak corresponding to the vibration of amorphous tellurium was identified at 150 cm−1. Organic TeC bonding was found in the TeC:H film, and the origin of this bonding is discussed by taking into consideration the deposition process, including surface reaction on the tellurium target. The chemical sputtering process is suggested to contribute to the deposition of TeC:H film.

Substrate position dependence of characteristics of Te-C:H film prepared by DC magnetron sputtering in methane atmosphere

A valence band and a Raman spectrum of Te–C:H film deposited in 50% methane atmosphere with argon as a dilution gas have been confirmed to vary according to the substrate arrangement on the anode in dc magnetron sputtering processes. The effect of bombardment by neutralized recoil argon was discussed for the sputtering processes of the Te–C:H film. Optical emission spectroscopy of the sputtering processes on tellurium was carried out for three gas atmospheres: argon, 50% methane, and pure methane. The optical emissions from atomic and ionic tellurium were recognized even in pure methane atmosphere. A chemical reaction and chemical sputtering have been considered to be involved in the sputtering process between the tellurium target and hydrocarbon species in the plasma.