Impact of Plasma Pretreatment and Pore Size on the Sealing of Ultra-Low-k Dielectrics by Self-Assembled Monolayers

Abstract

Self-assembled monolayers (SAMs) from an 11-cyanoundecyltrichlorosilane (CN-SAM) precursor were deposited on porous SiCOH low-k dielectrics with three different pore radii, namely, 1.7, 0.7, and lower than 0.5 nm. The low-k dielectrics were first pretreated with either O2 or He/H2 plasma in order to generate silanol groups on the hydrophobic pristine surface. Subsequently, the SAMs were chemically grafted to the silanol groups on the low-k surface. The SAMs distribution in the low-k films depends on the pore diameter: if the pore diameter is smaller than the size of the SAMs precursors, the SAM molecules are confined to the surface, while if the pore diameter exceeds the van der Waals radius of the SAMs precursor, the SAMs molecules reach deeper in the dielectric. In the latter case, when the pore sidewalls are made hydrophilic by the plasma treatment, the chemical grafting of the SAM precursors follows the profile of the generated silanol groups. The modification depth induced by the O2 plasma is governed by the diffusion of the oxygen radicals into the pores, which makes it the preferred choice for microporous materials. On the other hand, the vacuum ultraviolet (VUV) light plays a critical role, which makes it more suitable for hydrolyzing mesoporous materials. In addition to the density of the surface -OH groups, the nanoscale concave curvature associated with the pores also affects the molecular packing density and ordering with respect to the self-assembly behavior on flat surfaces. A simple model which correlates the low-k pore structure with the plasma hydrophilization mechanism and the SAMs distribution in the pores is presented.

Impact of VUV photons on SiO2 and organosilicate low-k dielectrics: General behavior, practical applications, and atomic models

“…ICP plasma in O2/Ar and H2/(Ar or He) mixtures was used for evaluation of damage mechanisms in strip plasma and for low-k pretreatment in order to generate silanol groups on the hydrophobic pristine surface for deposition of self-assembled monolayers for pore sealing and barrier deposition 170 . Also Cu In the DSP reactors, the plasma region is usually separated from the processing region.…”

Vapor-deposited zeolitic imidazolate frameworks as gap-filling ultra-low-k dielectrics

“…One promising class of dielectric materials are metal-organic frameworks (MOFs) 25 , which possess many properties sought for in interconnects: (i) uniformly distributed pores with diameters < 2 nm that significantly reduce possible infiltration during subsequent processing 26,27 and makes the porous dielectric applicable in sub-10 nm intermetal spacings 28,29 ; (ii) a low dielectric constant; and (iii) a suitable mechanical stability 6,7 . The potential of MOFs as advanced low-k dielectrics was first recognized by Zagorodniy et al, who used a simple Clausius–Mossotti model to estimate the dielectric constants of various MOFs 30 .…”

The Origin of the Odd–Even Effect in the Tunneling Rates across EGaIn Junctions with Self-Assembled Monolayers (SAMs) of n-Alkanethiolates

“…Interestingly, the odd-even effect in the capacitance (C SAM ) of the SAMs is remarkably large which suggests that SAMs are promising candidates for high-performance dielectrics. [52][53][54][55][56] Background Molecular vs. interface effects. Although the terms "molecular effects" and "interface effects" have been frequently used in the context of SAM-based junctions 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 to pinpoint which part of the junction dominates the electrical characteristics of the junctions, these terms are usually not well-defined.…”