Solvent-Dependent Adhesion Strength of Electroless Deposited Ni–P Layer on an Amino-Terminated Silane Compound-Modified Si Wafer

Abstract

Amino-terminated silane compound modification was wet-processed on a silicon wafer using four different solvents to investigate the property of the self-assembled monolayer (SAM) and its influence on the adhesion of electroless deposited nickel–phosphorus (Ni–P) films. Analyzed by various tools including dynamic light scattering, the atomic force microscope, X-ray photoelectron spectroscopy, inductively coupled plasma with mass spectroscopy, a proper link between the processing solvent and SAM quality is established. It is found that at least the chemical compatibility, the polarity, and the acidity of solvents can affect the final morphology of the resultant SAM. Unlike toluene and ethanol that are most frequently chosen in literature, we conclude that isopropyl alcohol (IPA) is a superior solvent for amino-terminated silane compounds. Owing to the good SAM quality formed in IPA, the adhesion of electroless deposited Ni–P films is largely strengthened, even as high as the bulk strength of silicon wafers.

Chemical-Structure Evolution Model for the Self-Assembling of Amine-Terminated Monolayers on Nanoporous Carbon-Doped Organosilicate in Tightly Controlled Environments

“…Notably, toluene has been reported to cause grafting and aggregation of aminosilane molecules with sizes up to submicrometer. ,,,− The toluene-induced grafted groups existing in the solution may further affect the formation of APTMS monolayers in a nonuniform manner, which could therefore cause a rugged surface. To confirm the aggregation of aminosilane in the toluene solvent, Figure S1 and Table S1 in the Supporting Information show the DLS results of aggregates size distributions in the solvent, indicating that submicrometer-sized APTMS grafting aggregates indeed exist in the solvent.…”

“…In this stage, the −NH 3 + disordered groups are gradually transformed into well-aligned −NH 2 groups. Then, the tethered APTMS molecules gradually cross-link together, forming Si–O–Si linkages through mutual bond conversion of the adjacent Si–OH horizontal groups (Si–OH + Si–OH → Si–O–Si + H 2 O) (Reaction 3). ,, This process finally leads to the formation of a highly ordered monolayer terminated by vertically standing −NH 2 groups (Scheme C). The formation of the Si–O–Si linkages is confirmed from the XPS result showing that the parent peak (103.0 eV) from p-SiOCH vanishes as the silanization time exceeds 60 min, while the peak of the APTMS monolayer finally shifts to a characteristic binding energy (102.2 eV) also yielding a saturated intensity level.…”

“…Meanwhile, the unreacted methoxy groups of the assembled molecules could react with the previously released CH 3 OH, forming a Si−OH bond through the reaction of Si− OCH 3 + CH 3 OH → Si−OH + C 2 H 5 OH↑ (Reaction 2). 52 Simultaneously, some of the −NH 2 functional groups topple and detach a proton from the Si−OH groups primarily from 13,17,31 This process finally leads to the formation of a highly ordered monolayer terminated by vertically standing −NH 2 groups (Scheme C). The formation of the Si−O−Si linkages is confirmed from the XPS result showing that the parent peak (103.0 eV) from p-SiOCH vanishes as the silanization time exceeds 60 min, while the peak of the APTMS monolayer finally shifts to a characteristic binding energy (102.2 eV) also yielding a saturated intensity level.…”

“…The uncontrolled environmental humidity level even causes thickness variations of amine-based SAMs up to 140–286% . Accordingly, previous studies concerning SAM growth have proposed various chemical-bonding and monolayer-structure evolution models according to their findings under specific growth conditions, − which could be not clearly stated or precisely controlled (such as humidity issue).…”

Electrochemical Grafting of an Aminated Poly(methyl methacrylate) (PMMA)-like Liner onto a Silicon Surface for the Metallization of Microfeatures

“…Autocatalytic deposition, also known as electroless plating, onto dielectric films (SiO 2 , Si 3 N 4 ) is a key metallization technique in the fabrication of Si-based microelectromechanic systems (MEMS) in industry. − Current electroless plating processes rely on surface modification for grafting amine-terminated groups onto these dielectric substrates, allowing an activation to form nuclei for initiating the plating process. , These dielectric films are conventionally deposited on a Si substrate through different physical techniques, e.g., thermal oxidation, physical vapor deposition, and plasma-enhanced chemical vapor deposition. Various applications requiring these processes mainly face the following challenges: complex and high-maintenance-requiring process equipment, only operative at high temperature, resultant poor film uniformity in high-aspect-ratio features.…”