Han-jin Lim

Improvement of Contact Resistance between Ru Electrode and TiN Barrier in Ru/Crystalline-Ta2O5/Ru Capacitor for 50 nm Dynamic Random Access Memory

The contact resistance (RC) between a Ru electrode and a TiN plug in a crystalline Ta2O5 capacitor using Ru electrodes was evaluated. The TiN plug was oxidized in TiOx to increase the RC to failure. Two origins of oxygen are determined by Auger electron spectroscopy (AES) analysis, namely, the seed step of Ru deposition and the initial step of Ta2O5 deposition. During Ta2O5 crystallization annealing at 700°C, the oxygen molecules from Ru diffused into the TiN plug, forming TiOx. Ru films with Ti exhibited a decreased RC below 1 kΩ/contact and an increased leakage current of a Ru/Ta2O5/Ru capacitor according to the applied voltage, compared with Ru films without Ti. The atomic layer deposition (ALD) Ru process including a H2 plasma treatment decreased the RC to 2.5 kΩ/contact on average. The fabrication scheme for the crystalline Ta2O5 capacitor using the Ru electrode for reducing RC between the Ru storage node and the TiN plug was proposed.

A robust alternative for the DRAM capacitor of 50 nm generation

As a new alternative for the DRAM capacitor of 50 nm generation, Ru/Insulator/TiN (RIT) capacitor with the lowest Toxeq of 0.85 nm has been successfully developed for the first time. TiO/sub 2//HfO/sub 2/ and Ta/sub 2/O/sub 5//HfO/sub 2/ double-layers were used as dielectric materials. After full integration into 512 Mbits DRAM device, the RIT capacitor showed good electrical properties and thermal stability up to 550/spl deg/C and its time-dependent-dielectric-breakdown behavior sufficiently satisfied 10-year lifetime within a DRAM operation voltage.

Investigation of Ru/TiN Bottom Electrodes Prepared by Chemical Vapor Deposition

Ru thin films were prepared by metalorganic chemical vapor deposition (MOCVD) using cyclopentadienyl-propylcyclopentadienlylruthenium(II) [RuCp(i-PrCp)] and the nucleation behaviors of Ru films on Ta2O5, TiN, Si3N4, SiO2, TiO2 substrates were investigated. It appeared that the difference in nucleation behaviors on various substrates is due to the bonding type between atoms in substrate materials. The nucleation property of Ru films on TiN was successfully improved by plasma treatment of the TiN substrate using Ar before film deposition. It was found that the Ar plasma treatment selectively removes N ions from the surface, makes the TiN surface more metallic or ionic (due to the residual Ti-O bonding), and reduces the nucleation barrier. In addition, the oxidation resistance of Ru/TiN layers was improved by H2 annealing, which made the Ru films more dense.

Schottky barrier height engineering for next generation DRAM capacitors

DRAM capacitors are reaching the scaling limit and new approaches are necessary to enable further reduction of the physical thickness of the capacitor dielectric. The Schottky Barrier Height (SBH) of a noble metal electrode (Pt) on atomic layer deposited ZrO2/Al2O3/ZrO2 (ZAZ, 6 nm) was evaluated and compared to a TiN electrode. Internal Photo Emission Spectroscopy (IPE) and Photoconductivity measurement (PC) were used to estimate the SBH and band gap, respectively. The SBH difference between the two electrodes was evaluated in comparison with a previously reported model. Finally, the impact of an increased SBH on dielectric scaling will be discussed based on a leakage current simulation of a ZrO2 capacitor.