As semiconductor devices shrink, the use of three dimensional topology increases. Near band edge work function metals are of increased importance for achieving desirable low power device performance. Due to the reactivity and mobility of electropositive metals, integration problems arise in incorporating such metals in device gate and contact regions. Atomic layer deposition (ALD) and other forms of chemical vapor deposition (CVD) of metal carbides or carbonitrides containing electropositive elements such as titanium, tantalum and aluminum have been used to deposit n-type work function material on silicon. However, these materials tend to exhibit limited n-shift in their electronic properties (particularly, in their flat-band voltages), exhibit relatively high resistivity, and require a metal diffusion barrier in integration.
USPTO Backgrounds
USPTO Backgrounds