Methods for Depositing Thick Aluminum Interconnect Lines by Using a Two-Chamber Aluminum Physical Vapor Deposition Process

摘要

Thick (>2μm) aluminum (AlCu) metal interconnect lines are typically used as inductor coils and RF bus lines for wireless communication applications. This paper describes methods for depositing such metal films using a two-chamber PVD process, and highlights the comparative issues for a single-chamber process. In earlier studies it was observed that when a thick AlCu film was deposited in a single deposition chamber with the target being close to end of life, an "abnormal" grain growth was obtained due to the inherent excess thermal budget. Such abnormal grains are hard to etch during a subsequent metal-etch process, thereby leaving residual AlCu particles. A design of experiments was performed to understand the impact of using a two-chamber deposition process with different process conditions/sequences. This paper describes the electrical performance (metal sheet resistance), defect density, and wafer die yield for different thick AlCu films using different deposition methods.