Chemical-mechanical planarization compatible for both copper/lowk level in a 90 nm technology and thick copper level in an RF technology

摘要

The emergence of wireless communication technologies has increased the need for high performance radio frequency (RF) circuits as transceivers or filters (1). These functions imply high quality factor (Q) inductors. One way to reach such high Q value is to increase the ultimate copper thickness (above 3μm). Whereas Cu CMP has been widely reported as one of the leading techniques to integrate copper interconnects, many issues are still encountered for thick copper applications, where uniformity, topology and process time are major concerns. In this study, we develop a copper bulk CMP process compatible for both thick copper/low k interconnects and RF application. Starting from conventional sub-0.18μm slurry, an additive solution is added to enhance its removal rate. Results obtained on a 4 μm thick level are presented. It is shown that electrical performances are preserved, notably sheet resistance uniformity. Other usual CMP parameters, like planarization and consumables aging are also presented. The approach reported here, which emphasizes chemical contribution, is expected to make compatible slurries dedicated to sub-0.18μm copper/low k technologies with thick copper applications, while not inducing significant additional cost of ownership.