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Trench and Via Filling with Electroplated Copper: Effect of Current Density and Pulse Waveform

Published online by Cambridge University Press:  17 March 2011

C. H. Seah
Affiliation:
Thin Film Dept., Chartered Silicon Partners Pte Ltd., 60 Woodlands Industrial Park D, Street 2, Singapore 738406, Singapore Phone/Fax: (65)-3946348/3946516 Email: seahch@charteredsemi.com
S. Mridha
Affiliation:
School of Applied Science, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore
Y. K. Siew
Affiliation:
School of Applied Science, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore
G. Sarkar
Affiliation:
School of Applied Science, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore
L. H. Chan
Affiliation:
Research & Development Dept., Chartered Semiconductor Manufacturing Ltd., 60 Woodlands Industrial Park D, Street 2, Singapore 738406, Singapore
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Abstract

A study was carried out to investigate the effect of current density and pulse waveform on the filling of line trenches and contact vias with aspect ratio of 2:1 for sub-0.25 µm device manufacturing using normal pulse plating of copper. The growth pattern of the copper films deposited using 0.05 and 0.10 A/cm2 current density gave no significant difference. Small grains were seen to have nucleated uniformly across the line trenches and via holes after 1 second of electroplating. With increasing the deposition time to 2 seconds, a slight buildup of the film thickness was observed in both trenches and vias without significant increase in the size of the copper grains. Grain growth involving the coalescence of small grains occurred after 5 seconds of plating and a further buildup in thickness and fill up of the trenches and vias occurred after 10 seconds of deposition.

When the patterned wafers were plated with a pulse waveform of 3 ms on and 0.5 ms off, the filling of trenches could not be complete after 30 seconds of electroplating. A complete filling of the trenches was achieved within 30 seconds of deposition using a pulse waveform of 6 to 8 ms on and 1 to 2 ms off. When the on-period was increased above this range to 9.9 ms, voids were observed at the centre of the via holes.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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