Manipulating the adhesion of electroless nickel-phosphorus film on silicon wafers by silane compound modification and rapid thermal annealing

Abstract

In this study, the effect of 3-2-(2-aminoethylamino) ethylamino propyl trimethoxysilane (ETAS) modification and post rapid thermal annealing (RTA) treatment on the adhesion of electroless plated nickel-phosphorus (ELP Ni-P) film on polyvinyl alcohol-capped palladium nanoclusters (PVA-Pd) catalyzed silicon wafers is systematically investigated. Characterized by pull-off adhesion, atomic force microscopy, X-ray spectroscopy and water contact angle, a time-dependent, three-staged ETAS grafting mechanism including islandish grafting, a self-assembly monolayer (SAM) and multi-layer grafting is proposed and this mechanism is well correlated to the pull-off adhesion of ELP Ni-P film. In the absence of RTA, the highest ELP Ni-P film adhesion occurs when ETAS modification approaches SAM, where insufficient or multi-layer ETAS grafting fails to provide satisfactory results. On the other hand, if RTA is applied, the best ELP Ni-P film adhesion happens when ETAS modification is islandish owing to the formation of nickel silicide, where SAM or multi-layer ETAS modification cannot provide satisfactory adhesion because the interaction between ETAS and PVA-Pd has been sabotaged during RTA. Evidenced by microstructural images, we also confirmed that ETAS can act as an efficient barrier layer for nickel diffusion to bulk silicon.

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

“…However, homogeneous assembling of a highly oriented monolayer by the wet process is difficult because of (a) the hydrolysis of a self-assembled molecule by itself and (b) its chemical bonding with either a substrate or an adjacent self-assembled molecule involves a wide variety of organic functional moieties. Moreover, the growth of a highly ordered SAM using a wet process is quite tricky, involving many parameters, such as the type of solvents used, − the presence of trace amounts of water during silanization, the soaking time and temperature of silanization, , and the baking condition after the silanizations. , For example, water exists in an environment at all times with changeable partial pressures depending on humidity levels. Therefore, it has to be critically controlled during wet growth of SAMs because excess (or varying) water content could cause uncontrolled hydrolysis and polymerization of R–Si–X 3 molecules on the surface and/or the formation of oligomers and polymers of silane in situ in a solution of the molecule to be self-assembled .…”

“…Advanced microelectronic devices also require an ultrathin barrier layer with a thickness less than 2 nm . Thus, SAMs have been receiving much attention as the barrier layer of Cu metallization. ,, Moreover, SAM barriers could also serve as a pore sealant for p-SiOCH. ,, However, silanization of p-SiOCH for the growth of a highly ordered monolayer barrier (or pore sealant) has not been well explored. , …”

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

“…It is generally accepted that silane compound modification is achieved by forming a self-assembled monolayer (SAM) between the head group and the substrate, whereas the tail is capable of chemisorbing a variety of materials such as nanoparticles, − metal ions, − polymers, , and so on. Silane compound modification can act as an adhesion promotor for coatings, − surface functionalization for biochemical characterizations, , or copper diffusion barrier layer in semiconductor manufacturing. − Generally, the formation of SAM involves four steps including silanol formation, hydrogen bond formation, condensation of water, and formation of the O–Si–O covalent bond . Although the abovementioned principle is easy to understand, the operation of silane compound modification is, however, tricky and sensitive to process conditions.…”

“…Although the abovementioned principle is easy to understand, the operation of silane compound modification is, however, tricky and sensitive to process conditions. For instance, the number of amino groups, , the solvent used in dissolving silane compounds, , the immersion time of silanization, − and the baking condition during covalent bond formation are reported to affect the final configuration of SAM considerably.…”

Organosiloxane Monolayers Terminated with Amine Groups as Adhesives for Si Metallization

“…Interfacial adhesion of a heterojunction such as metal/semiconductor, metal/oxide, and metal/polymer junctions has been a challenging issue and is more critical in nanoscaled circuits. Molecular nanolayers (MNLs) based on self-assembling organosilanes are reported as the promising candidates of the adhesion enhancer. − Due to strong self-assembling capability, the organosilane molecules form a continuous two-dimensional networked structure with an ultrathin thickness of about 1–2 nm on the substrate surface, which is in possession of superior film uniformity and integrity. The organosilane molecules bear two specific functional groups on their two ends of the main backbone, three hydrolyzed silanol groups and a terminal amino group, having strong affinity toward the substrate and loaded metallic atoms, respectively. − Therefore, the organic molecular nanolayer serves as an efficient adhesive tethering the deposited metal film to the substrate.…”