Question

In semiconductor precessing, in Gate mask step, because of rough surface of Gate, reflection occurs on the surface, so they use stoichiometric compound TiN film on Gate. Why they use stoichiometric compound?

Answer 1

The thinner insulating layers and smaller dimensions allowed for faster switching, thereby increasing speed and improving performance.

However, smaller sizes presented new challenges. For example, the insulating silicon dioxide (SiO2) layer between the conducting channel and the gate became so thin that quantum tunneling resulted in gate leakage currents too high to sustain stable MOSFET operation

the insulating SiO2 layer is required to be as thin as possible in order to reach the high gate to channel capacitance required for effective switching characteristics, while a physically thicker layer helps to reduce tunneling.

Effective switching and reduced tunneling were achieved by replacing SiO2 with a material with a higher dielectric constant (high-k material), to balance the increased distance between the gate and the channel. The most prominent of those materials used today are Hafnium (Hf)-based insulators, usually HfO2.

The combination of a high dielectric constant and a wide band gap [4], needed to create a potential barrier to the silicon channel and thus to act as an insulator, make HfO2 ideal for this purpose. Therefore, it is the most commonly used material for gate insulation ever since its introduction in the 45 nm technology node