As dynamic random-access memory (DRAM) devices continue to scale, reducing the equivalent oxide thickness (EOT) of capacitors and achieving precise control of the dielectric-electrode interface have become critical challenges. TiO2 has emerged as a promising high-k dielectric material due to its crystalline phases, anatase (dielectric constant of 30-75) and rutile (dielectric constant of 90-170). However, its application is limited by high leakage current that arises from the low conduction band offset with conventional electrodes. In particular, the low-temperature formation of rutile TiO2 is strongly influenced by lattice mismatch with the bottom electrode. Interface engineering strategies, such as the introduction of RuO2 layers on Ru electrodes, have been proposed to mitigate this issue. In this work, TiN, a bottom electrode widely adopted in mass-production processes, was employed to enhance the electrical performance of TiO2-based capacitors through systematic interface control. The effects of different TiN deposition methods on substrate properties were investigated, and argon plasma treatment was introduced to tailor the dielectric-electrode interface and promote rutile TiO2 formation. Both the TiN bottom electrode and the TiO2 dielectric layer were deposited using plasma-enhanced atomic layer deposition to ensure high film quality. As a result, the leakage current density was suppressed to approximately 10-5 A/cm2 at 0.8 V, while the EOT was reduced to 1.32 nm. These results indicate that the crystallization behavior of TiO2 thin films strongly depends on dielectric thickness and substrate crystallinity. The findings provide important guidelines for developing TiO2-based high-k dielectric thin films for advanced capacitor applications.

Molybdenum is a low-resistivity transition metal that can be applied to silicon devices using Si-metal electrode structures and thin film solar cell electrodes. We investigate the deposition of metal Mo thin film by plasma-enhanced atomic layer deposition (PE-ALD). Mo(CO)6 and H2 plasma are used as precursor. H2 plasma is induced between ALD cycles for reduction of Mo(CO)6 and Mo film is deposited on Si substrate at 300℃. Through variation of PE-ALD conditions such as precursor pulse time, plasma pulse time and plasma power, we find that these conditions result in low resistivity. The resistivity is affected by Mo pulse time. We can find the reason through analyzing XPS data according to Mo pulse time. The thickness uniformity is affected by plasma power. The lowest resistivity is 176 μΩ·cm at Mo(CO)6 pulse time 3s. The thickness uniformity of metal Mo thin film deposited by PE-ALD shows a value of less than 3% below the plasma power of 200 W.

TaNx film is grown by plasma enhanced atomic layer deposition (PEALD) using t-butylimido tris(dimethylamido) tantalum as a metalorganic source with various reactive gas species, such as N2+H2 mixed gas, NH3, and H2. Although the pulse sequence and duration are the same, aspects of the film growth rate, microstructure, crystallinity, and electrical resistivity are quite different according to the reactive gas. Crystallized and relatively conductive film with a higher growth rate is acquired using NH3 as a reactive gas while amorphous and resistive film with a lower growth rate is achieved using N2+H2 mixed gas. To examine the relationship between the chemical properties and resistivity of the film, X-ray photoelectron spectroscopy (XPS) is conducted on the ALD-grown TaNx film with N2+H2 mixed gas, NH3, and H2. For a comparison, reactive sputter-grown TaNx film with N2 is also studied. The results reveal that ALD-grown TaNx films with NH3 and H2 include a metallic Ta-N bond, which results in the film’s higher conductivity. Meanwhile, ALD-grown TaNx film with a N2+H2 mixed gas or sputtergrown TaNx film with N2 gas mainly contains a semiconducting Ta3N5 bond. Such a different portion of Ta-N and Ta3N5 bond determins the resistivity of the film. Reaction mechanisms are considered by means of the chemistry of the Ta precursor and reactive gas species.

Aluminum-oxide(Al2O3) thin films were deposited by electron cyclotron resonance plasma-enhanced atomic layer deposition at room temperature using trimethylaluminum(TMA) as the Al source and O2 plasma as the oxidant. In order to compare our results with those obtained using the conventional thermal ALD method, Al2O3 films were also deposited with TMA and H2O as reactants at 280 oC. The chemical composition and microstructure of the as-deposited Al2O3 films were characterized by X-ray diffraction(XRD), X-ray photo-electric spectroscopy(XPS), atomic force microscopy(AFM) and transmission electron microscopy(TEM). Optical properties of the Al2O3 films were characterized using UV-vis and ellipsometry measurements. Electrical properties were characterized by capacitance-frequency and current-voltage measurements. Using the ECR method, a growth rate of 0.18 nm/cycle was achieved, which is much higher than the growth rate of 0.14 nm/cycle obtained using thermal ALD. Excellent dielectric and insulating properties were demonstrated for both Al2O3 films.