Advanced Transistors with Threshold Voltage Set Dopant Structures
OwnerLucian Shifren, Pushkar Ranade +1inventors
InventorsLucian Shifren, Pushkar Ranade, Lance Scudder
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Abstract
An advanced transistor with threshold voltage set dopant structure includes a gate with length Lg and a well doped to have a first concentration of a dopant. A screening region is positioned between the well and the gate and has a second concentration of dopant greater than 5×1018 dopant atoms per cm3. A threshold voltage set region is formed by placement of a threshold voltage offset plane positioned above the screening region. The threshold voltage set region may be formed by delta doping and have a thickness between Lg/5 and Lg/1. The structure uses minimal or no halo implants to maintain channel dopant concentration at less than 5×1017 dopant atoms per cm3.
Claims8
A field effect transistor structure, comprising
- a well doped to have a first concentration of a dopant,
- a screening region positioned between the well and the gate and having a second concentration of dopant greater than 5×1018 dopant atoms per cm3,
- a threshold voltage set region formed by placement of a threshold voltage offset plane, with the threshold voltage offset plane positioned above the screening region.
A method for forming a field effect transistor structure, comprising the steps of forming a well doped to have a first concentration of a dopant,
- implanting a screening region into the well having a dopant concentration dopant of greater than 5×1018 dopant atoms per cm3,
- growing an epitaxial layer on top of the screening region, the epitaxial layer having a thickness selected to be between about Lg/5 and about Lg/1,
- forming a threshold voltage offset plane in the layer grown on the screening region, and
- forming a gate having gate length Lg between a source and a drain, and above the screening region.
Dependencies are inferred from the claim text.