Optimizing Band-Edge High-κ/Metal Gate n-MOSFETs with ALD Lanthanum Oxide Cap Layers: Oxidant and Positioning Effects

We have previously shown that by varying the position of threshold voltage adjustment cap layers within the gate stack, as well as the oxidant used during processing, it is possible to tune the threshold voltage of n-FET devices, and to concurrently realize a scaling benefit by incorporating group IIA and group IIIB elements into gate dielectrics deposited by metalorganic atomic layer deposition. In this report we have focused on lanthanum oxide cap layers that provide band edge nFET work functions. We compare our previously reported results with ozone oxidation with newly developed processes using oxygen and water as oxidants that result in highly scaled devices with band edge work functions and acceptable leakage characteristics.