Junction formation in FinFET using Arsenic and Phosphorus Co-Doped Epitaxy
Publication Date: 2014-Mar-25
The IP.com Prior Art Database
A method is disclosed for forming one or more n-channel Field Effect Transistor (nFET) junctions using an in-situ co-doped epitaxy of arsenic and phosphorus for merging nFET fins.
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Junction formation in FinFET using Arsenic and Phosphorus Co -Doped Epitaxy
Junction formation in FinFET is usually accomplished by outdiffusion from source/drain merge epitaxy into a channel region under a spacer. Very high dopant levels are desirable to form good contacts and to achieve low contact resistance (Rext). However, high dopant levels close to the gate lead to high diffusion of the dopant under the spacer during extension formation annealing. Also, the merge epitaxy is very highly doped between fins of the n-channel Field Effect Transistor (nFET) and lower doped in the overgrowth region.
Fig. 1 illustrates a cross-sectional view of an nFET parallel to the fins showing low doping on top of epitaxy.
Fig. 2 illustrates high doping in between the fins during extension formation annealing.
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Disclosed is a method for forming one or more nFET junctions using an in-situ co-doped epitaxy of arsenic and phosphorus for merging nFET fins. A phosphorus atom (100 pm) is smaller than silicon (110 pm), while Arsenic atom is bigger than Silicon (115 pm). Therefore, co-doping leads to more overall dopant incorporation and more substitutional (electrical active) dopants. The method works on the principle that arsenic diffuses much slower than phosphorus in silicon at any temperature due to difference in sizes of arsenic and phosphorus. Thus, there is less diffusion in channel region and very high dopant level of arsenic in source drain r...