A New Alternative Electrochemical Process for a Pre-Deposited UPD-Mn Mediated the Growth of Cu(Mn) Film by Controlling the Time during the Cu-SLRR

Jau-Shiung Fang,Yu-Fei Sie,Giin-Shan Chen,Yi-Lung Cheng

doi:10.3390/coatings10020164

Jau-Shiung Fang, Yu-Fei Sie + Show 2 more

Open Access

https://doi.org/10.3390/coatings10020164

Copy DOI

Abstract

A layer-by-layer deposition is essential for fabricating the Cu interconnects in a nanoscale-sized microelectronics because the gap-filling capability limits the film deposition step coverage on trenches/vias. Conventional layer-by-layer electrochemical deposition of Cu typically works by using two electrolytes, i.e., a sacrificial Pb electrolyte and a Cu electrolyte. However, the use of a Pb electrolyte is known to cause environmental issues. This study presents an Mn monolayer, which mediated the electrochemical growth of Cu(Mn) film through a sequence of alternating an underpotential deposition (UPD) of Mn, replacing the conventionally used UPD-Pb, with a surface-limited redox replacement (SLRR) of Cu. The use of the sacrificial Mn monolayer uniquely provides redox replacement by Cu2+ owing to the standard reductive potential differences. Repeating the sequence of the UPD-Mn followed by the SLRR-Cu enables Cu(Mn) film growth in an atomic layer growth manner. Further, controlling the time of open circuit potential (OCP) during the Cu-SLRR yields a technique to control the content of the resultant Cu(Mn) film. A longer OCP time caused more replacement of the UPD-Mn by the Cu2+, thus resulting in a Cu(Mn) film with a higher Cu concentration. The proposed layer-by-layer growth method offers a wet, chemistry-based deposition capable of fabricating Cu interconnects without the use of the barrier layer and can be of interest in microelectronics.

Highlights

A copper interconnect in advanced microelectronic devices conventionally uses a sputter-depositedTa/TaN barrier layer to promote the adhesion and block diffusion of Cu into underlying materials.The Cu interconnect is typically fabricated by the damascene process
We have reported that the Cu(Mn) film can be electrochemically deposited through a sequence of surface-limited redox replacement (SLRR) of Cu to replace the previous sacrificial, underpotentially deposited (UPD) Pb and inserting a underpotential deposition (UPD)-Mn [19]
Afterwards, the Cu electrolyte was pumped into the deposition cell at open circuit potential (OCP) and the Cu-SLRR was allowed to occur by replacing the UPD-Mn for a controlled time of 20, 40, and 60 s, due to the standard potential values difference between Cu and Mn (E0 Cu/Cu2+ = +0.34 VSHE ; E0 Mn/Mn2+ = −1.18 VSHE )

Summary

Introduction

A copper interconnect in advanced microelectronic devices conventionally uses a sputter-deposited. The studied self-forming Cu(Mn) films are normally deposited by the sputtering process, and the sputtering process impedes the film gap-filling capability in the high-aspect-ratio trenches/vias. The literature on the electrochemical deposition of Cu(Mn) alloy thin film is rare, for application to microelectronic devices, because Mn has a low, negative reductive potential (E0 (Mn2+ /Mn) = −1.18 VSHE ) [16,17,18] To tackle this issue, we have reported that the Cu(Mn) film can be electrochemically deposited through a sequence of surface-limited redox replacement (SLRR) of Cu to replace the previous sacrificial, underpotentially deposited (UPD) Pb and inserting a UPD-Mn [19].

Experimental Procedures

Results and Discussion

These charges were of

Conclusions