Performance of Integrated Cu Gap-Filling Process with Chemical Vapor Deposition Cobalt Liner

Abstract

Cu interconnects are used in semiconductor devices and their dimensions are downscaled markedly. Cu interconnects are fabricated by a damascene process, and it becomes difficult to fill Cu into trenches and vias structures by electroplating below the 20 nm feature size. We evaluated the process integration for Cu interconnects using a Co wetting layer by chemical vapor deposition (CVD), a Cu seed by magnetic-field-assisted ionized sputtering (MFIS) and a Cu reflow technique. The properties of a CVD-Co film, such as composition, resistivity, step coverage, and adhesion between Cu and Co, were investigated. By using CVD-Co as the wetting layer, the properties of Cu gap filling in a trench structure were improved, and the filling of Cu into a 14-nm-wide trench structure was achieved.

Low Temperature, Selective Atomic Layer Deposition of Cobalt Metal Films Using Bis(1,4-di-tert-butyl-1,3-diazadienyl)cobalt and Alkylamine Precursors

“…Cobalt metal films have applications as magnetic materials, , intermediate layers in the fabrication of CoSi 2 contacts, and caps and liners of copper metal structures in microelectronics devices to minimize electromigration. − Cobalt metal may even replace copper metal as the conductors in future devices . Cobalt metal films have been traditionally grown by physical vapor deposition (PVD) − and chemical vapor deposition (CVD) from a range of molecular precursors. − Decreasing dimensions to <10 nm in microelectronics devices will require cobalt metal film growth by atomic layer deposition (ALD) to provide conformal, controlled thickness layers. − The self-limiting growth mechanism in ALD inherently leads to conformal films with subnanometer thickness control. , Plasma-enhanced ALD of cobalt metal films has been demonstrated with a variety of cobalt precursors and ammonia or hydrogen reactant gases. − While plasma-based ALD methods provide high quality cobalt metal films, the reactive plasmas can damage substrates and may give poor conformal coverage of narrow and deep features because the reducing species recombine on the feature walls before they are able to promote film growth .…”

“…There is considerable interest in area-selective growth by ALD, since this approach can eliminate many steps associated with conventional patterning . Area-selective ALD growth of cobalt metal is particularly relevant to the deposition of cobalt caps and liners on copper features. − The selective growth of cobalt metal films on various surfaces has been achieved with several different approaches. Self-assembled monolayers derived from octadecyltrimethoxysilane were patterned on silicon substrates, such that there were alternating stripes of self-assembled monolayers and uncoated SiO 2 . − Subsequent thermal ALD using Co­(iPrNCMeNiPr) 2 and NH 3 or H 2 gave growth only on the SiO 2 features up to 1000 cycles.…”

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

“…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. 10 CoSi 2 , fabricated by the reaction of Co with silicon, is a useful material for contacts due to its thermal and chemical stability. 11,12 Cobalt and cobalt nitride have been previously deposited by various means, including physical vapor deposition (PVD), 2,4 chemical vapor deposition (CVD) [7][8][9][12][13][14][15][16][17][18] and atomic layer deposition (ALD) 5,6,8,9,[19][20][21] methods.…”

Proximity Effects of the Selective Atomic Layer Deposition of Cobalt on the Nanoscale: Implications for Interconnects

“…During Co CVD growth, the Co film layer grows inward until the via closes up, leaving behind a void. To eliminate this void, annealing is performed at roughly 350–400 °C to reflow the Co metal to fully fill the via . Another method hypothesized to improve selectivity is to introduce a periodic anneal step in between sets of cycles to act as a mid-deposition reflow.…”

“…According to the simple Ostwald ripening model, atoms from small nuclei can more readily diffuse than atoms from large nuclei; therefore, by annealing the surface periodically during deposition while nuclei are smaller, it may be possible to induce Co diffusion from the nuclei to the Co/Cu stripes at a lower temperature than a typical reflow process. To test this hypothesis, after each 100 Co ALD cycles, annealing to 260 °C for 30 min in ultrahigh vacuum was performed, which is around 140 °C below the normal Co reflow temperature. − As the temperature of Co ALD is far below the anneal temperature and cycle times are on the order of 50× shorter than the anneal time, diffusion of Co nuclei is expected to be negligible during growth, necessitating the periodic anneal step.…”