Effect of tungsten incorporation in cobalt tungsten alloys as seedless diffusion barrier materials

With the increase in the aspect ratio of the interconnect features in integrated circuits, the direct electroplating of Cu on diffusion barrier without sputtered Cu seed layers is attracting more and more attention. In this study, direct electroplating of Cu onto sputtered CoW films with various W c...

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Bibliographic Details
Published in:Microelectronic engineering 2017-03, Vol.171, p.25-30
Main Authors: Su, Yin-Hsien, Kuo, Tai-Chen, Lee, Wen-Hsi, Wang, Yu-Sheng, Hung, Chi-Cheng, Tseng, Wei-Hsiang, Wei, Kuo-Hsiu, Wang, Ying-Lang
Format: Article
Language:English
Subjects:
Adhesion
Alloys
Aspect ratio
Chemical elements
Cobalt base alloys
Copper base alloys
Corrosion
CoW
Diffusion
Diffusion barriers
Diffusion layers
Electroplating
Integrated circuits
Seedless barrier
Surface stability
Thermal stability
Thin films
Tungsten base alloys
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Summary:With the increase in the aspect ratio of the interconnect features in integrated circuits, the direct electroplating of Cu on diffusion barrier without sputtered Cu seed layers is attracting more and more attention. In this study, direct electroplating of Cu onto sputtered CoW films with various W concentration in acidic CuSO4 solution is investigated. Also, the adhesion and anti-diffusion properties of the CoW thin films for Cu are explored. The results show that Cu films cannot be electrodeposited on thin Co layers due to corrosion of Co in the acidic bath. For CoW alloys, higher W concentration is found to be beneficial for suppressing corrosion of CoW films and also improving the thermal stability. However, on the surface of Cu/CoW films with high W concentration, Cu agglomeration and pin-holes were found after annealing, indicating poor adhesion between Cu and high-W-content CoW alloys. In this study, CoW alloys with moderate W concentration around 50% are found to be a direct platable material which also demonstrates desirable adhesion and anti-diffusion characteristics for Cu interconnects application. [Display omitted] •Addition of W over 50% in CoW alloys can suppress corrosion of Co in acidic bath.•Wetting ability of CoW alloys degrades with increasing W content.•Higher W concentration in CoW alloys leads to superior anti-diffusion ability against Cu.•CoW with 50% W content can serve as seedless barriers for Cu interconnects.
ISSN:0167-9317
1873-5568
DOI:10.1016/j.mee.2017.01.029