Impact of Self-Aligned Metal Capping Method on Submicron Copper Interconnections

概要

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Novel copper (Cu) interconnection technology using self-aligned metallic cap was developed to reduce effective dielectric constant (k-value) as well as to improve reliability. Tungsten (W) was preferentially deposited on Cu wiring by chemical vapor deposition (CVD) using tungsten hexa-fluoride (WF6) and hydrogen (H2). Though W selectivity loss occurred without additional cleaning because of Cu contamination on the dielectric film during the chemical mechanical polishing (CMP) process, this problem was solved by surface cleaning prior to W-CVD combined with lift-off process just after it, resulting in improved yield in the test element group (TEG) during a short check. Using these processes, we fabricated a large-scale integration (LSI) with 4-level Cu interconnections eliminating capping barrier dielectrics such as silicon nitride (SiN), which had a relatively high k-value, and confirmed that there was no degradation in LSI yield. We also confirmed effective k-value was reduced by comparing propagation delay in conventional and metal-capped interconnections.
2004-05-15