Reactively Sputtered Mo–V Nitride Thin Films as Ternary Diffusion Barriers for Copper Metallization

Abstract

The effectiveness and performance of Mo-based ternary nitride films as copper diffusion barriers were investigated. Thermally stable Mo-V nitride thin diffusion barrier layers were deposited using radio frequency reactive magnetron sputtering and their barrier capability was evaluated and studied. Cu/Mo-V nitride/Si structures were fabricated and annealed at different temperatures. The agglomeration of Cu and the formation of Cu 3 Si due to high-temperature annealing were probed using scanning electron microscopy/energy-dispersive X-ray spectroscopy. The drastic increase in sheet resistance after annealing at 800°C was found to take place due to the formation of highly resistive Cu 3 Si, also evident from X-ray diffraction patterns. The formation of inverted pyramidal structure of Cu 3 Si at the interface penetrated into the Si substrate corroborated the breakdown of the barrier layer at 800°C. Our results suggest that an 8 nm thick Mo-V nitride barrier can effectively prevent the formation of Cu 3 Si up to high annealing temperatures.The resistance-capacitance ͑RC͒ delay in integrated circuits ͑ICs͒ is becoming inevitable with decreasing dimensions of metal oxide semiconductor devices. In order to address this RC delay, Cu has replaced conventional Al as an interconnect material because the former has low bulk resistivity ͑ϳ1.7 ⍀ cm͒, high melting point, and superior electromigration resistance to that of Al. 1 However, the transition from Al to Cu metallization has given rise to numerous challenges. One of the challenges is to develop a suitable diffusion barrier to restrict the interaction of Cu and Si or SiO 2 that form detrimental Cu silicides at temperatures as low as 200°C. 2,3 The barrier material should ideally have high thermal stability, negligible reactivity with Cu and the underlying Si substrate during the manufacture and operation of the device, low resistivity, and good adhesion to Cu and Si. 4,5 Furthermore, the continuous shrinking of feature sizes in future generations of ICs requires thinner diffusion barrier layers. 6 Various transition metals, their alloys, nitrides, borides, carbides, and ternary barriers have been studied over the past few decades as potential diffusion barriers. Kaloyeros and Eisenbraun 5 reviewed the properties of such barrier materials in detail. They reported that the failure of these barrier layers takes place primarily due to the diffusion of Cu atoms through the barrier grain boundaries and/or bulk defects such as vacancies and dislocations, after annealing at higher temperatures.It is known that bilayer and ternary single-layer barrier structures offer higher thermal stability than that of their corresponding singlelayer metal and metal nitrides. It has been reported that the increase in thermal stability of ternary barrier structure is likely due to the delay in the crystallization of the barrier material upon annealing, because the formation of grain boundaries can be delayed with the addition of a third element. 7,8 Thus, ternary nitride alloys, such as W-B-N,

Controllable Synthesis of Band-Gap-Tunable and Monolayer Transition-Metal Dichalcogenide Alloys

“…The recent breakthrough in the chemical vapor deposition (CVD) growth of MoS 2 , WSe 2 , and WS 2 monolayers (Lee et al, 2012(Lee et al, , 2013Huang et al, 2014) has stimulated the direct growth of monolayer TMD alloys. Several recent manuscripts have shown that MoS 2x Se 2(1-x) is obtainable through the gas phase reaction of MoO 3 with the mixture of S and Se (Gong et al, 2013;Li et al, 2014;Mann et al, 2014). These preliminary works prove the theoretical prediction that TMD monolayer alloys are stable at room temperature (Jiang, 2012).…”

General Strategy for Two-Dimensional Transition Metal Dichalcogenides by Ion Exchange

“…The peaks at 232.5, 229.3, 163.4, and 162.2 eV can be assigned to the Mo 4+ 3d 3/2 , Mo 4+ 3d 5/2 , S 2– 2p 1/2 and S 2– 2p 3/2 , respectively. These XPS datum are in agreement with previous reports, − further confirming that the three ion exchange processes are successfully completed.…”

Band Gap‐Tunable Molybdenum Sulfide Selenide Monolayer Alloy

“…Figure displays the detailed XPS scans for the Mo, S and Se binding energies for the as‐grown MoS 2 and those after selenization, where the magnitude of each profile was normalized for easier comparison. The as‐grown MoS 2 exhibits two characteristic peaks at 232.5 and 229.3 eV, attributed to the Mo 3d 3/2 and Mo 3d 5/2 binding energies for Mo 4+ . The peaks, corresponding to the S 2p 1/2 and S 2p 3/2 orbital of divalent sulfide ions (S 2− ) are observed at 163.3 and 162.1 eV .…”