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.