Optimizing ULK film properties to enable BEOL integration with TDDB reliability

Increasing circuit density in multilevel back-end-of line (BEOL) interconnects is necessary to improve integrated circuit performance and area scaling. Ultra low-k (ULK) dielectrics are used to minimize capacitance for lower power consumption and better capacitance-resistance (RC) performance. However, these materials pose integration and reliability challenges, which have limited our ability to scale the dielectric constant lower.¹ Minimizing porosity, maximizing carbon content, and altering how carbon is bonded in porous SiCOH films reduces plasma-induced damage (PID) to the ULK and improves TDDB reliability, but these improvement must be balanced by maintaining other film properties such as elastic modulus. This paper describes one technique to achieve this combination of high carbon content and low porosity to allow k scaling while meeting integration and reliability requirements.