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In order to enable an oxide-free Cu-to-Cu bonding in a (dual) damascene process, 3-aminopropyltrimethoxysilane- and decanethiol-derived self-assembled monolayers are selectively deposited in a dielectric-Cu based metal-insulator-metal (MIM) capacitor used as a test vehicle, which represents a dual damascene architecture environment. A two-steps SAM coating sequence is investigated for this purpose. In a first step, a ''sacrificial'' SHSAM is deposited on the Cu areas at the bottom of the vias. In a second step, a ''barrier'' NH"2SAM is deposited on the dielectric areas in the field region and via's sidewalls. This deposition sequence followed by the selective thermal ablation of the ''sacrificial'' SAM vs. the ''barrier'' SAM, enable an oxide-free Cu-to-Cu connection at via's bottom. The differential in thermal stability between the amino and thiol SAMs has been studied by water contact angle and cyclic voltammetry. While the sacrificial SAM is selectively desorbed by thermal ablation already at ~200^oC, the barrier SAM on the dielectric sidewall and field regions withstands a thermal budget as high as ~350^oC. The substrate-selective SAMs depositions are revealed by XPS chemical characterization on the Cu and dielectric areas of the MIM structures supported by the SEM visualization of the Au nanoparticles that selectively decorate the NH"2 functionalities of the barrier SAM.

The traditional Cu interconnect barrier/seed process consisting of PVD-Ta based barrier/Cu-seed will reach its limit between 20 nm and 30 nm wide trench dimension. To extend Cu interconnect technology further, possible solutions such as PVD-RuTa, PEALD-Ru-based, CVD-Co, PVD/CVD-self-formed-MnSixOy and self-assembled monolayers (SAMs) are studied. It is shown that both PVD-RuTa and CVD-Co possess the so-called seed enhancement capability allowing Cu filling of narrow recesses. However, they exhibit limitations in terms of Cu-diffusion barrier efficiency, electromigration reliability and scalability. Despite, the concept of SAM [NH2-SAM(C3)] as Cu diffusion barrier is demonstrated, it requires maturity and compatibility within the process flow (e.g. adhesion with the Cu overlayer). Finally, it is considered that PEALD-Ru-based alloys and CVD-based MnSixOy films are serious candidates for sub-30 nm wide trench technologies because of their conformal nature and ability to act as an efficient Cu diffusion barrier in the range of 2 nm thickness.

A 3-aminopropyltrimethoxysilane-derived self-assembled monolayer (NH 2 SAM) is investigated as a barrier against copper diffusion for application in back-end-of-line (BEOL) technology. The essential characteristics studied include thermal stability to BEOL processing, inhibition of copper diffusion, and adhesion to both the underlying SiO 2 dielectric substrate and the Cu over-layer. Time-of flight secondary ion mass spectrometry and X-ray spectroscopy (XPS) analysis reveal that the copper over-layer closes at 1-2-nm thickness, comparable with the 1.3-nm closure of state-of-the-art Ta/TaN Cu diffusion barriers. That the NH 2 SAM remains intact upon Cu deposition and subsequent annealing is unambiguously revealed by energy-filtered transmission electron microscopy supported by XPS. The SAM forms a well-defined carbon-rich interface with the Cu over-layer and electron energy loss spectroscopy shows no evidence of Cu penetration into the SAM. Interestingly, the adhesion of the Cu/NH 2 SAM/SiO 2 system increases with annealing temperature up to 7.2 J m -2 at 400°C, comparable to Ta/TaN (7.5 J m -2 at room temperature). The corresponding fracture analysis shows that when failure does occur it is located at the Cu/SAM interface. Overall, these results demonstrate that NH 2 SAM is a suitable candidate for subnanometer-scale diffusion barrier application in a selective coating for copper advanced interconnects.

Self-assembled monolayers (SAMs) are investigated as potential Cu diffusion barriers for application in back-end-of-line (BEOL) interconnections. A screening of SAMs derived from molecules with different head group (SiCl"3, Si(OCH"3)"3, Si(OCH"3)Cl"2) bonding to the dielectric substrate, chain lengths (n=3-21) and terminal group (CH"3, Br, CN, NH"2, C"5H"4N and SH) bonding to the Cu overlayer are compared in terms of inhibition of interfacial Cu diffusion and promotion of Cu-SiO"2 adhesion. SAM barrier properties against Cu silicide formation are examined upon annealing from 200 to 400^oC by visual inspection, sheet resistance measurements (Rs) and X-ray Diffraction Spectroscopy (XRD). Cu/SAM/SiO"2 adhesion is evaluated by tape test and four-point probe measurements. Results indicate that NH"2-SAM derived from 3-aminopropyltrimethoxysilane is the most promising for Cu diffusion barrier application. Silicide formation is inhibited to at least 400^oC, essential stability for BEOL integration. However, the 2.9Gc (J/m^2) adhesion of the layer compared with 3.1Gc (J/m^2) on SiO"2 does need improvement.

Two different material-selective Self assembled monolayers (SAMs) were successfully deposited on Cu and SiO 2 structures that mimic the Dual Damascene integration scheme. A two-step SAM coating process is presented. First, a “sacrificial” SAM is deposited at the Cu bottom and secondly, a “barrier” SAM at the SiO 2 surface. The order in the SAMs deposition sequence and the differential thermal release of the thiol “sacrificial” SAM vs. the amino “barrier” SAM, allows an oxide-free Cu-to-Cu connection at the vias bottom. While the sacrificial SAM is selectively released by thermal ablation, the barrier SAM remains intact on the dielectric sidewall and field regions, ready for the subsequent copper metallization.

The effects of suspension and functionalisation on electrical conduction of silicon nanowires (SiNWs) are experimentally investigated towards highly sensitive chemical and biological detection applications. The conductance is found to be affected by the suspension process, while it shows the similar trend against the temperature before and after the suspension. The reduction of conductance after the functionalisation with NH"2 self-assembled monolayer/glutaraldehyde/biotin can be explained based on the assumption that there is a charge transfer from the SiNW to the molecular layers. The temperature insensitive conductance found in the functionalised SiNWs experimentally for the first time is expected to be extremely useful for practical sensing applications.

This paper investigates a selective self-assembly process for formation of a self-assembled monolayers (SAM) barrier to Cu diffusion in dual damascene integration. In selecting a barrier, trichlorosilanes are promising due to their high thermal stability (above 550degC) and dense molecular packing. Overall, this study demonstrates that the tuneable structure and chemistry of SAMs provides a molecular level engineering approach for future device structures.

An alternative bottom-up Cu electroless deposition (ELD) method without other catalyst material activation is the focus of this paper. The process consists of reducing the Cu ions in a solution via standard reducing agents such as dimethylamine borane. The reaction pH and ionic strength values can be modulated to impart to the metallic Cu particle surface an opposite charge with respect to the deposition substrate functionalized by the 3-aminopropyltrimethoxysilane (APTS) self-assembled monolayer used as a diffusion barrier. At neutral pH, the negatively charged Cu particles are electrostatically attracted by the positively charged NH 2 groups, and they can form strong interfacial complexes if the required activation energy budget is supplied. A design of the experiment is carried out to optimize the critical deposition parameters such as temperature, time, Cu ion concentration, and pH. The formed ELD Cu nuclei positioned preferentially on the APTS layer, showing a wetting behavior that is accentuated upon anneal, leading to a decrease in surface roughness that corresponds to an increase in film closure. The observed debonding energy of the ELD Cu/APTS surface is ca. 2.2 J/m 2 before anneal, while it reaches ca. 4.5 and 8 J/m 2 after a 10 min anneal under forming gas at 300 and 450°C, respectively.