Robust self-assembled monolayer as diffusion barrier for copper metallization

Abstract

Excellent results on copper (Cu) diffusion barrier characteristics of a self-assembled monolayer (SAM) of 2-(diphenylphosphino)ethyltriethoxy-silane are reported. The thickness and roughness of the SAM were determined by grazing incidence x-ray reflectometry as 1.7 and 0.3 nm, respectively. To evaluate Cu diffusion barrier performance of the SAM, Cu/SiO2/Si and Cu/SAM/SiO2/Si metal-oxide-semiconductor capacitors were prepared to measure their lifetimes under the 2 MV/cm electric bias at 498–548 K. The mean times to failure obtained from the Weibull plots of time to failures were 33.6, 9.24, 4.57, and 2.03 h at 498, 523, 533 and 548 K, respectively. These values show that the barrier characteristic of the SAM of 1.7 nm in thickness is comparable to that of physical-vapor-deposited Ta film of 20 nm in thickness. The estimated lifetime of the SAM barrier at the device operation temperature of 392 K is longer than 10 yr.

Bottom‐Up Engineering of Subnanometer Copper Diffusion Barriers Using NH2‐Derived Self‐Assembled Monolayers

“…For instance, Cu is the preferred metal for creating multilevel interconnects structures in ultra-largescale-integrated (ULSI) circuits because of its high electromigration resistance and electrical conductivity. [1,2] A typical interconnect structure is composed of Cu/Ta/ TaN/SiO 2 where the Ta/TaN layer is required as a barrier to prevent interdiffusion between Cu and the underlying dielectric resulting in electrical shorting. Due to its poor electrical conductivity relative to Cu, the barrier layer thickness must be minimized while maintaining high-performance diffusion barrier properties and good adhesion strength with neighboring layers.…”

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

“…However in head-to-head comparisons with state-of-the-art TaN/Ta Cu diffusion barriers, SAMS have exhibited order of magnitude lower lifetimes in Cu-MIS TDDB testing indicating that SAMS may not be able to completely meet low-k/Cu interconnect reliability requirements. 477 In this regard, two challenges / areas of research needed for the use of SAMS in low-k metal interconnect applications are (1) the ability to withstand ion bombardment and thermal stresses from various downstream plasma processes, 484,485 and (2) 488,489 However from a diffusion barrier perspective, the relatively high-k of these materials could be accommodated if they allow more aggressive thickness scaling relative to current DB materials in the Si-O-C-N system. In this regard, Majumder has recently evaluated the Cu diffusion barrier performance of 3 nm thick Al 2 O 3 and even higher k HfO 2 ALD films.…”

“…474 Early investigations of SAMS have demonstrated them as effective Cu corrosion inhibitors in wire bonding 475 and other applications. 476 More recently, SAMS have been demonstrated as Cu diffusion barriers, [477][478][479] low-k ILD pore sealants, 480 Cu surface passivation layers, 481 and Cu/ILD adhesion promoters. 482,483 Due these successes and thicknesses <2-3 nm, SAMS are extremely attractive for meeting the ITRS forecast for <2 nm DBs.…”

Preparation of NiO Monolayer by Langmuir–Blodgett Technique and Its Characterization as Diffusion Barrier for Copper Metallization

“…[1] Copper tends to diffuse into adjoining SiO 2 layers and other low K dielectric materials under electrical bias and annealing which may result in short circuit with neighboring traces and interconnects resulting into the failure of device. [1,2] Thus copper-containing structures are generally surrounded by diffusion barriers to prevent such diffusion. Typically Ta/TaN, Ta-Si-N, W-Si-N, W-B-N, and Ta-W-N serve as barrier layers.…”