Application of Electroless Nickel−Boron Films for High-Selectivity Pattern Transfer Processes

Abstract

Electroless Ni exhibits excellent plasma etch resistance and has been successfully employed as a hard etch mask in the fabrication of microelectronic and microelectromechanical components and templates for contact printing and biomedical applications. The use of a catalytic agent to initiate electroless deposition is known to directly affect the microstructure and properties of the deposited metal and thus the etch resistance and potential pattern resolution. We have previously reported the development of tin-free colloidal Pd(II) electroless catalysts, which are suitable for initiating the deposition of patterned EL Ni films for use as plasma etch masks. In this work we examine the effect of the Pd(II) precursor on feature resolution, Ni plating rate, and etch resistance. The etch selectivity of deposited films is determined by real-time endpoint detection using laser reflectometry. Both film morphology and the formation of nickel silicides were found to impact the etch resistance in thin (<20 nm) films. Etch selectivity values exceeding 200:1 were observed for thicker EL Ni films on silicon.

A Non-Covalent Approach for Depositing Spatially Selective Materials on Surfaces

“…[26±29] The Pd 0 formed following the reduction of these Pd II colloids functions as an effective catalyst for EL metal deposition, forming a basis for the efficient preparation of negative-tone patterned metal films useful as plasma etch masks or electrical interconnects on the surface. [30] The development of an analogous covalent, positive-tone process for selective metallization of the un-irradiated regions of CMP films is precluded by the inertness of the C±Cl bond under ambient, aqueous reaction conditions. Recently, however, we have demonstrated that alternate surface ligand grafting techniques, based on non-covalent interactions between the CMP groups at the film surface and ligand from aqueous solution, can lead to efficient ligand immobilization at the CMP surface.…”

Noncovalent Deposition of Nanoporous Ni Membranes on Spatially Organized Poly(p‐xylylene) Film Templates

“…In comparison, Ni films of ∼35-40 nm thickness are deposited on flat aminosiloxanecoated Si wafers catalyzed and plated under conditions identical to those used for our NTFs. [26] Such differences are not unexpected, given the magnitude of the NTF surface roughness and the isotropic nature of the EL process. Specifically, the combination of perpendicular and lateral Ni growth from catalyzed PPX-C filament tips and sidewalls, respectively, at the NTF top surface leads to more rapid agglomeration and fusion of adjacent Ni nodules than for a flat surface, enhancing the apparent Ni deposition rate.…”

Selective Metal Pattern Fabrication Through Micro-Contact or Ink-Jet Printing and Electroless Plating onto Polymer Surfaces Chemically Modified by Plasma Treatments

“…More recently, several ''tin-free'' processes have also been developed. They are mainly based on the strong chemical affinity of Pd þ2 species towards nitrogen-containing functionalities [34,35] and the chemisorption of Pd þ2 species (direct activation in a PdCl 2 -based solution) is carried out on surfaces which were previously either: (i) coated with specific self-assembled monolayers (SAMs) such as organosilanes containing amine or pyridine endgroups [36][37][38][39][40][41][42][43]; (ii) grafted with nitrogen-containing species through plasma or UV=VUV treatments in a nitrogenated (NH 3 , N 2 ) atmosphere [44][45][46][47][48][49]; or (iii) coated with thin films obtained by plasma (or UV-induced) graft copolymerisation of either vinylimidazole or vinylpyridine precursors [50][51][52][53][54][55][56]. Whatever the activation mode, it should be noted that to initiate the metallization in the plating bath and make the adhesion at the metal=polymer interface as strong as possible, a key requirement consists in strongly anchoring the catalytic particles at the polymer surface.…”

“…For example, Dressick and co-workers [37][38][39][40][41][42][43] fabricated micrometer and sub-micrometer scale Ni, Co, and Cu patterns at the surface of various substrates including polymers such as poly(tetrafluoroethylene), poly(carbonate), epoxy, ABS, poly(sulfone), and poly-(chloromethylstyrene). To chemically graft the Pd 0 catalyst (from a Pd (II)-based colloidal solution) to the substrate surface, they mainly used two fully additive processes based on both PL and the deposition of organosilane thin films (SAMs) containing specific ligand functional end-groups such as alkylamines, pyridines, or phosphines.…”

“…To chemically graft the Pd 0 catalyst (from a Pd (II)-based colloidal solution) to the substrate surface, they mainly used two fully additive processes based on both PL and the deposition of organosilane thin films (SAMs) containing specific ligand functional end-groups such as alkylamines, pyridines, or phosphines. In the first process [42,43], the substrate was coated successively with the organosilane film and a polymeric photoresist layer [channel constrained metallization (CCM) process]. Localized light exposure (using UV or VUV irradiation and a suitable mask) and development of the photoresist layer allowed the opening of channels in the underlying organosilane thin film, then the selective anchoring of the Pd-based catalyst to the SAM end-groups, and finally the ELD to be carried out.…”