Impact of Current Flow Shape in Tapered (Versus Rectangular) FinFET on Threshold Voltage Variation Induced by Work-Function Variation

Depending on the real fin shape in a FinFET (i.e., rectangular versus tapered fin), the impact of the current flow shape in both rectangular and tapered FinFETs on threshold voltage variation induced by work-function variation is investigated by performing extensive 3-D TCAD simulations. It is found that if a FinFET has two independent (versus single and bulky) current flow in the channel, the extended gate area should be (should not be) included in calculating the ratio of average grain size to gate area (RGG) to agree with a previously validated FinFET RGG plot. Depending on the current flow shape in a FinFET, the RGG calculation should be refined.