Plasma-Enhanced Atomic Layer Deposition of Amorphous Tantalum Thin Films for Copper Interconnects Using an Organometallic Precursor

As integrated circuits continue to shrink in size, the demand for high-quality adhesive layers in copper Damascene interconnects has increased. However, tantalum (Ta) films, used as liners, prepared by atomic layer deposition (ALD) from metal halide precursors, are prone to corrosion and exhibit issues such as low film density and unstable performance. In this study, Ta films are successfully fabricated using a plasma-enhanced ALD (PEALD) process with an organometallic precursor of Ta(NtBu)(NEt2)3 (TBTDET). The study of the growth conditions reveals that introducing 10% Ar in Ar-H2 mixed gas leads to continuous high-quality Ta films. The deposited Ta films are free of halogen impurities, which can avoid the detrimental impact on the stability of the Cu interconnects. Although the films contain some carbon and nitrogen impurities, they do not affect the film adhesive properties. Transmission electron microscopy shows that the Ta films are amorphous, and the amorphous Ta films exhibit superior barrier properties. Moreover, highly uniform Ta films can be conformally deposited into narrow interconnect structures using this PEALD process. These findings suggest that the Ta films prepared by the organometallic precursor can offer a promising solution to address the issues related to the halogen elements in the adhesive layer preparation. A plasma-enhanced atomic layer deposition (PEALD) process using Ta(NtBu)(NEt2)3 (TBTDET) is developed to prepare high-quality halogen-free Ta films. The deposited Ta films show good wettability, adhesion property, and barrier property. Uniform Ta films can be conformally deposited into narrow trench and via interconnect structures, which highlights the suitability of this process for the BEOL interconnect technology.image