Electrochemically Deposited Diffusion Barriers

Abstract

Diffusion barrier properties of electrochemically deposited Ni, Co, and Ni-Co alloys were examined in the Ni(Co)/Cu binary system and the Au/Ni/Cu ternary system. Ni and Co were electrodeposited from sulfate or sulfamate (Ni) solutions in the presence of boric acid, at pH 3.30. Electroless Ni and Co deposited either from sulfate or sulfamate solution using sodium hypophosphite or dimethylamine borane as the reducing agent. Eleetroless gold was deposited from cyanide solutions using potassium borohydride as the reducing agent. The deposits were annealed at 400~ for 14 h in a forming gas atmosphere (10% H2, 90% N2). Auger eiectron spectroscopy and electron probe analysis were used to assess the extent of interdiffusion as a result of the heat-treatment. Only~ electrolessly deposited 1000 A thick Ni, Co, and Ni-Co alloys have barrier properties for Cu diffusion. For Co(P) 1000 A thick barriers, annealed for 14 h, the amount of the interdiffused copper into Co(P) was less than 1 atomic percent. Thicker barriers of Ni(P), Ni(B), and Co(B) are required for the same degree of Cu diffusion. Ni(P) thin films deposited from nickel sulfamate solutions are better diffusion barriers than those deposited under the same experimental conditions, from nickel sulfate solutions. Electrochemically deposited barriers were compared with Ni, Co, and Cr barriers produced by evaporation. The differences between the diffusion barrier properties of Ni(P) deposited from the sulfamate and the sulfate solutions were interpreted in term of microstruetural data and grain growth mechanism.

A Study on the Long-Term Degradation of Crystalline Silicon Solar Cells Metallized with Cu Electroplating

“…The penetration depth for Ni and Co into Cu was deeper than the depth for Cu in Ni, Co or Ni 71 Co 29 . Among them, the penetration of Co profile into Cu was the deepest for the Cu/Co stack as shown in Figure 9b.…”

“…This pulse scheme was to allow the replenishment of metal ions at the vicinity of substrate surface and to avoid the compositional change as a result of ion depletion. The layer plated with each pulse was identical to the NiCo layer used in the previous study and a composition of Ni 71 Co 29 was obtained by SEM-EDS analysis. To be consistent, the pure Ni was plated with the same pulse scheme.…”

Synthesis and structures of Co bis-trifluoromethylpyrazolate complexes

“…Synthesis and structures of [1][2][3][4][5][6] Three new cobalt pyrazolate complexes were synthesized using either standard salt elimination routes from cobalt halides and the sodium or lithium salt of 3,5-(CF 3 ) 2 -Pz or by oxidative addition of the N-H bond of the parent pyrazole (3, ) 2 -PzH) to the highly reactive zero-valent Co complex Co(PMe 3 ) 4 (Scheme 1). The use of n-BuLi to generate the pyrazolate lithium salt was the first route explored.…”

“…While films of pure metallic cobalt do not make good diffusion barrier layers due to the presence of grain boundaries that allow diffusion of copper, it has been shown that cobalt alloys are promising for use as barrier layers in copper interconnects, especially alloys containing phosphorus. 1 For example, Ekerdt and coworkers recently described the CVD growth of amorphous Co(P) alloys containing 1-5% P from [Co 2 (CO) 8 ] and PMe 3 or from the single source precursor [Co(PMe 3 ) 4 ]. These films been shown to be potential diffusion barrier layers, since they allow virtually no copper diffusion after annealing.…”

Electrodeposition Science and Technology in the Last Quarter of the Twentieth Century

“…More recently, electroless plating has found many new applications in electronics manufacturing, especially for packaging and for producing diffusion barriers. 211,212 Electroless plating requires a more elaborate bath control than electroplating, but on the other hand, it provides better throwing power and it does not require conducting substrates.…”