Temperature Dependence of the Morphology of Copper Sputter Deposited on TiN Coated Substrates

Abstract

DC magnetron sputter deposition of copper thin films is evaluated for resistivity, conformality etc., in this work. Sputter deposition is attractive as an alternative to chemical vapor deposition because sputtering is a well-characterized and cost effective technique which is already widely implemented. Conformal copper deposition may be feasible since copper reflow at temperatures much lower than the melting point of 1083°C has been observed by a number of workers. In this case, an attractive approach is sputter deposition of copper at a sufficiently high temperature so that the need for a separate reflow anneal is eliminated. In the present work, it was found that better conformality is achieved with lower deposition rate, higher pressure, lower sputter power, and lower bias voltage. However, low sputter power may affect adhesion of the copper film to an underlying barrier layer such as TiN, and, of course, the associated low deposition rate affects overall throughput undesirably. Good gap filling of 1:1 aspect ratios with a 0.5 p.m opening is achievable with cop-per sputtering, but a practical manufacturing process remains to be demonstrated since a high defect density has been observed in copper conductors fabricated with conformal sputtering and chemical-mechanical polishing. Introductian Copper metallization has the potential for becoming theintegrated circuit interconnect material of choice in the relatively near future due to its low resistivity and high