1 research outputs found
Conformal Electroless Nickel Plating on Silicon Wafers, Convex and Concave Pyramids, and Ultralong Nanowires
Nickel (Ni) plating
has garnered great commercial interest, as it provides excellent hardness,
corrosion resistance, and electrical conductivity. Though Ni plating
on conducting substrates is commonly employed via electrodeposition,
plating on semiconductors and insulators often necessitates electroless
approaches. Corresponding plating theory for deposition on planar
substrates was developed as early as 1946, but for substrates with
micro- and nanoscale features, very little is known of the relationships
between plating conditions, Ni deposition quality, and substrate morphology.
Herein, we describe the general theory and mechanisms of electroless
Ni deposition on semiconducting silicon (Si) substrates, detailing
plating bath failures and establishing relationships between critical
plating bath parameters and the deposited Ni film quality. Through
this theory, we develop two different plating recipes: galvanic displacement
(GD) and autocatalytic deposition (ACD). Neither recipe requires pretreatment
of the Si substrate, and both methods are capable of depositing uniform
Ni films on planar Si substrates and convex Si pyramids. In comparison,
ACD has better tunability than GD, and it provides a more conformal
Ni coating on complex and high-aspect-ratio Si structures, such as
inverse fractal Si pyramids and ultralong Si nanowires. Our methodology
and theoretical analyses can be leveraged to develop electroless plating
processes for other metals and metal alloys and to generally provide
direction for the adaptation of electroless deposition to modern applications