Thermal annealing effects on a representative high-k/metal film stack

A high-k/metal film stack in a conventional complementary metal oxide semiconductor (CMOS) flow is a key candidate in the semiconductor industry for replacing the existing poly-silicon gate and silicon dioxide (SiO₂) gate dielectric to reduce poly depletion and gate leakage. During conventional CMOS integration, the high-k/metal film stack is exposed to a high thermal budget process. In this work, an atomic layer deposition (ALD)-based hafnium oxide (HfO₂)/titanium nitride (TiN) film stack (representative of the high-k/metal film stack) was annealed at 1000 °C to determine any change in the physical and electrical properties, such as thickness, surface roughness, density, sheet resistance, refractive index, extinction coefficient, composition, C-V characteristics, work function and etch rate. Although there was no significant electrical impact, some significant physical changes have been observed, which impact the process of integrating high-k/metal film stacks, especially in dual metal gate CMOSs.