Use of TiN(O)/Ti as an effective intermediate stress buffer and diffusion barrier for Cu/parylene-n interconnects

Abstract

Copper and parylene-n (Pa-n) are studied for ultralarge scale integration circuits because of their low electrical resistivity, resistance to electromigration and low dielectric constant, chemical inertness, and compatibility with current integrated circuit manufacturing, respectively. Copper diffusion observed at and above 300 °C in Pa-n correlates to an increase in the crystallinity of the α phase and subsequent transformation to the more open structure of β parylene. Titanium nitride (oxygen) [TiN(O)]/titanium (Ti) bilayers are successfully implemented as a diffusion barrier. TiN is proven to be a very good diffusion barrier up to 500 °C for copper due to its large negative heat of formation and hence its thermal stability. Incorporation of an intermediate titanium layer reduced the residual stress and thermal mismatch between Pa-n and TiN. Without the Ti layer thermal cracking of TiN occurred. The presence of the buffer layer had no detrimental effects on the overall resistivity. The effectiveness of the barrier is attributed to stuffing of the grain boundaries with oxygen and nitrogen. This results in the elimination of rapid diffusion paths. This work provides the foundation for future implementation of Cu/Pa-n for higher temperature microelectronics.

Barrier performance of ultrathin amorphous Nb–Ni film between copper and silicon

“…Compared with Al interconnect, Cu interconnect has some advantages in larger electromigration, and smaller resistance [1,2]. However, some issues are concerned about Cu interconnect related to Cu diffusion, such as poor adhesive ability, and reaction between Cu and Si [3]. Therefore, an ideal barrier layer has to be inserted between Cu and Si to separate the two layers from direct contact [4].…”

Structural, Optical, and Electronic Properties of Cu-Doped TiNxOy Grown by Ammonothermal Atomic Layer Deposition

“…3 Oxygen incorporation stuffs the TiN grain boundaries and improves the effectiveness of the diffusion barrier. 4 TiN x O y also prevents oxidation of the copper routings. 5 Other applications of TiN x O y films include low leakage MIM capacitors, 6 photocatalysts, 7,8 solar-selective absorbing coatings, 9,10 and the photovoltaic device power conversion efficiency boosters.…”

“…The complementary metal–oxide–semiconductor (CMOS) industry typically uses a TiN barrier layer to prevent the copper diffusion from the metal routings in the back-end-of-the-line (BEOL) integrated circuit (IC) fabrication process . Oxygen incorporation stuffs the TiN grain boundaries and improves the effectiveness of the diffusion barrier . TiN x O y also prevents oxidation of the copper routings .…”

Improvement of thermal stability of Ta-N film in Cu metallization by a Zr-Si interlayer

“…Copper metallization has become very popular in the Si industry. Cu possesses significant advantages over Al in terms of RC delay and electromigration [1,2] . However, Cu reacts with oxides, silicon, and silicides and it is a fast diffuser in these materials due to its high mobility.…”