Threshold Voltage Adjustment For Thin Body Mosfets

Abstract

A structure includes a substrate; a transistor disposed over the substrate, the transistor comprising a fin comprised of Silicon that is implanted with Carbon; and a gate dielectric layer and gate metal layer overlying a portion of the fin that defines a channel of the transistor. In the structure a concentration of Carbon within the fin is selected to establish a desired voltage threshold of the transistor.

What is claimed is: 
     
         1 . A structure, comprising:
 a substrate;   a transistor disposed over the substrate, the transistor comprising a fin comprised of Silicon that is implanted with Carbon; and   a gate dielectric layer and gate metal layer overlying a portion of the fin that defines a channel of the transistor, where   a concentration of Carbon within the fin is selected to establish a desired voltage threshold of the transistor.   
     
     
         2 . The structure of  claim 1 , where the concentration of Carbon is substantially uniform throughout the fin. 
     
     
         3 . The structure of  claim 1 , where the Carbon is implanted into the Silicon prior to the fin being formed. 
     
     
         4 . The structure of  claim 1 , where the Carbon is implanted into the Silicon after the fin is formed. 
     
     
         5 . The structure of  claim 1 , where there are a plurality of transistors disposed over the substrate each comprising an associated fin, and where a concentration of Carbon within at least two fins is different such that each of the associated transistors has a different value of voltage threshold. 
     
     
         6 . The structure of  claim 5 , where a first Carbon concentration in a first fin and a second Carbon concentration in a second fin are each in a range of about 2×10 14  to about 5×10 15  atoms/cm 3 . 
     
     
         7 . The structure of  claim 1 , where at least two Carbon implant operations are carried out using a different implant energy such that the concentration of Carbon is made substantially uniform throughout the fin. 
     
     
         8 . The structure of  claim 1 , where the Silicon is a Silicon-on-Insulator (SOI) layer. 
     
     
         9 . A structure, comprising:
 a substrate;   a first FinFET disposed over the substrate, the first FinFET comprising a first fin comprised of Silicon that is implanted with Carbon having a first concentration, a gate dielectric layer and gate metal layer overlying a portion of the first fin that defines a channel of the first FinFET;   a second FinFET disposed over the substrate, the second FinFET comprising a second fin comprised of Silicon that is implanted with Carbon having a second concentration, a gate dielectric layer and gate metal layer overlying a portion of the second fin that defines a channel of the second FinFET;   where the first FinFET has a first voltage threshold and the second FinFET has a second voltage threshold that differs from the first voltage threshold by an amount related to a difference between the first Carbon concentration and the second Carbon concentration.   
     
     
         10 . The structure of  claim 9 , the first fin and the second fin are each implanted using at least two Carbon implant operations performed one each of two major surfaces of the fin such that the concentration of Carbon is made substantially uniform throughout the thickness of the fin. 
     
     
         11 . The structure of  claim 9 , where the first and second Carbon concentrations are each in a range of about 2×10 14  to about 5×10 15  atoms/cm 3 . 
     
     
         12 . The structure of  claim 9 , where the Silicon is a portion of a Silicon-on-Insulator (SOI) layer.