Method of using a sacrifical gate structure to make a metal gate finfet transistor

Abstract

A self-aligned SiGe FinFET device features a relaxed channel region having a high germanium concentration. Instead of first introducing germanium into the channel and then attempting to relax the resulting strained film, a relaxed channel is formed initially to accept the germanium. In this way, a presence of germanium can be established without straining or damaging the lattice. Gate structures are patterned relative to intrinsic silicon fins, to ensure that the gates are properly aligned, prior to introducing germanium into the fin lattice structure. After aligning the gate structures, the silicon fins are segmented to elastically relax the silicon lattice. Then, germanium is introduced into the relaxed silicon lattice, to produce a SiGe channel that is substantially stress-free and also defect-free. Using the method described, concentration of germanium achieved in a structurally stable film can be increased to a level greater than 85%.

Description

BACKGROUND[0001]1. Technical Field[0002]The present disclosure generally relates to techniques for fabricating an array of high performance FinFET devices.[0003]2. Description of the Related Art[0004]Advanced integrated circuits often feature strained channel transistors, silicon-on-insulator (SOI) substrates, FinFET structures, or combinations thereof, in order to continue scaling transistor gate lengths below 20 nm. Such technologies allow the channel length of the transistor to shrink while minimizing detrimental consequences such as current leakage and other short channel effects.[0005]A FinFET is an electronic switching device in which a conventional planar semiconducting channel is replaced by a semiconducting fin that extends outward from the substrate surface. In such a device, the gate, which controls current flow in the fin, wraps around three sides of the fin so as to influence current flow from three surfaces instead of one. The improved control achieved with a FinFET de...

AI Technical Summary

Benefits of technology

[0008]Strain and mobility effects in the channel of a FinFET can be tuned by controlling the size and the elemental composition of the fins. It is advantageous for SiGe films to contain a high concentration of germanium, e.g., in the range of at least 25%-40%, to provide enhanced electron mobility compared with lower concentration SiGe films. Carrier mobility in the channel region determines overall transistor performance. Consequently, it is desirable to increase to a level as high as possible the percent concentration of germanium atoms in the fins of a SiGe FinFET.

Problems solved by technology

While a strained silicon lattice is beneficial, creating strain by incorporating germanium atoms using existing methods tends to damage the crystal lattice.

As a result, the lattice structures of germanium-rich films tend to be mechanically unstable, especially if they contain a high number of structural defects such as faults, or dislocations.

Furthermore, such a mechanically unstable fin may be structurally limited with regard to its aspect ratio, or height:width ratio.

Such a limitation is undesirable because one advantage of a FinFET is that the fin, being a vertical structure, has a small footprint.

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