Application of electroless nickel-boron films for high-selectivity pattern transfer processes

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.