The plasma-enhanced atomic layer deposition ͑PEALD͒ of tantalum nitrides ͑TaN͒ thin films has been performed using terbutylimidotris͑diethylamido͒tantalum and hydrogen radicals at a temperature of 260°C. The film thickness per cycle is also self-limited at 0.8 Å/cycle, which is thinner than that of the conventional atomic layer deposition ͑ALD͒, 1.1 Å/cycle. X-ray diffraction analysis indicates that the as-deposited films are not amorphous but polycrystalline mixed with cubic TaN and TaC. The film crystallinity as well as the film density increases with the pulse time and the electrical power of the hydrogen plasma used. By using the hydrogen radical as a reducing agent instead of NH 3 , which is a typical reactant gas used in ALDs and metallorganic chemical vapor depositions of TaN, the films show a much lower electrical resistivity and show no aging effects under exposure to air, owing to the increased film density and crystallinity, and the presence of TaC bonding. In addition, it has been shown that films, which are formed by the PEALD, retain perfect step coverage on the submicrometer holes with an aspect ratio of 10:1.As increasing demand for smaller, faster electronic devices in ultralarge scale integrated devices ͑ULSI͒, copper ͑Cu͒ with a lower resistivity and an enhanced electromigration resistance represents a promising material for providing better performance as an interconnect metal than aluminum ͑Al͒ alloys which are currently in use. 1 However, Cu forms Cu-Si compounds and an easily drift through the oxide at a low temperature. 2 Therefore, a diffusion barrier between Cu and its underlying layers is thought to be a prerequisite for Cu to be used in applications for silicon integrated circuits. For this purpose, transition metal nitrides represent attractive alternatives for use in Cu diffusion barriers. Among these, tantalum nitride has received the most interest because of its high thermal stability and resistance to forming compounds with copper. 3,4 Until now, TaN films have been formed using a collimated and ionized physical vapor deposition ͑PVD͒ technique, since the aspect ratio of contact and via holes continuously increases, this technique will eventually meet application limits in forming conformal TaN films on the holes due to its line-of-sight type approach. In order to overcome this technological barrier, metallorganic chemical vapor deposition ͑MOCVD͒ of TaN films has been studied over the past 10 years, but conformal deposition without generating particles and an improvement in electrical resistivity remain primary issues. 5 In this respect, atomic layer deposition ͑ALD͒ represents an attractive candidate for forming TaN thin films on contact and via holes, because of its inherent abilities to grow conformal thin films almost perfectly and to prevent particle generation caused by intermixing between the reactant gases used, and to control the film thickness digitally on an atomic scale. [6][7][8] In practice, the upper deposition temperature in ALD is determined from the self-decompo...
Hf O 2 films with an enhanced dielectric constant, prepared through phase transition engineering by the addition of Al2O3, were deposited by plasma-enhanced atomic layer deposition adopting a supercycle concept. After an annealing step at 700°C, the tetragonal phase, which is a high-temperature phase of HfO2, was stabilized completely at room temperature and the crystallographic direction was changed to the preferred (002) orientation. As a result, Hf aluminate film with a (002)-oriented tetragonal phase had a dielectric constant of 47, approximately twice as large as the reported value of HfO2 film with a monoclinic phase.
Ruthenium-titanium nitride ͑Ru-TiN͒ thin films were grown by plasma-enhanced atomic layer deposition ͑PEALD͒ at a growth temperature of 200°C. For the Ru-TiN PEALD, Ru and TiN were sequentially deposited to intermix TiN with Ru. The composition of Ru-TiN films was controlled by changing the number of deposition cycles allocated to Ru, while the number of deposition cycles for TiN was fixed to one cycle. The microstructures of Ru-TiN films changed from polycrystalline to amorphous, as the intermixing ratio of Ru increased in the deposited Ru-TiN films. The resistivity of the Ru-TiN film was abruptly increased by adding Ru at the first stage, but after showing a peak resistivity, it decreased with the intermixing ratio of Ru in the films. Especially, the film of Ru 0.67 -͑TiN͒ 0.33 showed an electrical resistivity of 190 ⍀ cm. As a Cu diffusion barrier layer, amorphous Ru-TiN films showed a superior copper diffusion barrier property to TiN or Ru itself, which had a polycrystalline structure. Moreover, Ru-TiN films showed a good adhesion to both chemical vapor deposition copper and an underlayer of SiO 2 .
To cope with the ongoing changing demands of the internet, 'in-network caching' has been presented as an application solution for two decades. With the advent of information-centric network (ICN) architecture, 'in-network caching' becomes a network level solution. Some unique features of ICNs, e.g., rapidly changing cache states, higher request arrival rates, smaller cache sizes, and other factors, impose diverse requirements on the content eviction policies. In particular, eviction policies should be fast and lightweight. In this study, we propose cache replication and eviction schemes, Conditional Leave Cope Everywhere (CLCE) and Least Frequent Recently Used (LFRU), which are well suited for the ICN type of cache networks (CNs). The CLCE replication scheme reduces the redundant caching of contents; hence improves the cache space utilization. LFRU approximates the Least Frequently Used (LFU) scheme coupled with the Least Recently Used (LRU) scheme and is practically implementable for rapidly changing cache networks like ICNs.
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