Plasma Surface Modification for Ion Penetration Barrier in Organosiloxane Polymer

摘要

The stability of low dielectric constant (low-κ) hybrid organosiloxane polymer (HOSP) was investigated using the bias temperature stressing (BTS) technique on metal/HOSP/SiO{sub}2/Si capacitors. Compared to Cu, Al gate metal capacitors showed larger flatband voltage shifts in the capacitance - voltage (C-V) curves upon BTS. We ascribed this instability to ion penetration from gate metal. A metal diffusion barrier is typically required between interconnect metals and dielectrics. As SiO{sub}2 is a well-known barrier against Al penetration, an attempt was made to create a SiO{sub}2-like surface on HOSP using different plasma treatments. While N{sub}2O and O{sub}2 plasmas caused bulk damage, N{sub}2 and Ar plasma treatments dramatically reduced ion penetration from Al gate into HOSP. A short (1 min) low power (30 W) N{sub}2 plasma treatment at room temperature was effective as aluminum ion penetration barrier, without increasing the refractive index or dielectric constant value of HOSP. Formation of SiO{sub}2-like surface was confirmed from XPS investigations. The above plasma-treatment approach reveals one possible route to attain the "zero barrier thickness" requirement for interconnect systems.