Chemical Vapor Deposition of Cobalt Nitride and its Application as an Adhesion-Enhancing Layer for Advanced Copper Interconnects

Abstract

An interlayer of face centered cubic (fcc) Co4N has demonstrated significant improvements in adhesion between copper and diffusion barrier layers. This fcc phase of Co4N was prepared by chemical vapor deposition (CVD) using bis(N-tert-butyl-N′-ethyl-propionamidinato)cobalt(II) and a reactant mixture of NH3 and H2 at substrate temperatures from 100 to 180°C. The Co/N atomic ratio and the phase of cobalt nitride film can be modified by adjusting the ratio of NH3 and H2 in the gas feedstock. The cobalt nitride films prepared by CVD are smooth, highly conformal, and stable against intermixing with copper up to at least 400°C. This fcc cobalt nitride material has very strong adhesion to copper due to the small lattice mismatch (−1 to 2%) between fcc-Co4N and fcc Cu. Copper wires should be stabilized against failure by electromigration when fcc cobalt nitride interlayers are placed between the copper and surrounding diffusion barriers.

Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

“…[11][12][13][14][15][16][17][18][19] Recent theoretical calculations predicted that the spin polarization ratio for Co 4 N is even higher than that of Fe 4 N. 20,21 This has led to somewhat renowned interests in the Co-N system both theoretically and experimentally. [22][23][24][25][26][27][28] Though theoretical studies predict that under large-volume high-moment approach, the magnetic moment of Co 4 N can be larger than Co, 9 experimental results always find a value much smaller than pure Co, for Co 4 N thin films. 22 This can be understood as in all Co 4 N thin films reported so far the value of a has always been smaller than the value predicated theoretically.…”

Direct-liquid-evaporation chemical vapor deposition of smooth, highly conformal cobalt and cobalt nitride thin films

“…Thin films of cobalt (Co) and cobalt nitride (Co x N) have attracted considerable attention for their applications in giant magnetoresistance (GMR) devices, [1][2][3] spintronics, 4 and microelectronics technology. 5,6 For example, Co, 5 Co x N, 7 or Co-based alloy 8,9 have proven to be effective adhesion layers in copper interconnects as they demonstrated enhanced bonding between copper and barrier layers. Co has also been used as a wetting layer to induce void-free filling of narrow copper lines by reflow of nonconformal PVD copper for sub-20 nm nanostructures.…”

A Fundamental Approach to Electrochemical Analyses on Chemically Modified Thin Films for Barrier CMP Optimization

“…Although it has a relatively higher lattice mismatch to Cu, it gives better coverage and wettability. 3 Manganese (Mn) and Molybdenum (Mo) 9 are other alternatives since the Ru CMP generates a poisonous product at low pH values (lower than pH 8). Manganese (Mn) penetrates the silica in nano-scale and makes a barrier layer with high adhesion strength to Cu and hence it is considered as another good barrier layer alternative.…”