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AssigneeInternational Business Machines Corporation
InventorsAnda C. Mocuta, Meikei Ieong, Ricky S. Amos, Diane C. Boyd, Dan M. Mocuta, Huajie Chen
Estimating the term…
High performance (surface channel) CMOS devices with a mid-gap work function metal gate are disclosed wherein an epitaxial layer is used for a threshold voltage Vt adjust/decrease for the PFET area, for large Vt reductions (˜500 mV), as are required by CMOS devices with a mid-gap metal gate. The present invention provides counter doping using an in situ B doped epitaxial layer or a B and C co-doped epitaxial layer, wherein the C co-doping provides an additional degree of freedom to reduce the diffusion of B (also during subsequent activation thermal cycles) to maintain a shallow B profile, which is critical to provide a surface channel CMOS device with a mid-gap metal gate while maintaining good short channel effects. The B diffusion profiles are satisfactorily shallow, sharp and have a high B concentration for devices with mid-gap metal gates, to provide and maintain a thin, highly doped B layer under the gate oxide.
A CMOS device with a mid-gap work function metal gate, comprising:
A method for fabricating a CMOS device comprising:
Dependencies are inferred from the claim text.
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Using Group IV technology, e.g. silicon technology or silicon-carbide [SiC] technology: using silicon technology, e.g. SiGe
The components including complementary IGFETs, e.g. CMOS devices: manufacturing their channels
The components including complementary IGFETs, e.g. CMOS devices: manufacturing their gate conductors
Inorganic electric semiconductor devices
Term end not estimated
1. Field of the Invention
The present invention relates generally to high performance CMOS device structures with a mid-gap metal gate, and more particularly pertains to high performance CMOS device structures with a mid-gap work function metal gate wherein an epitaxial layer is used for a threshold voltage Vt adjust/decrease for the PFET area, for large Vt reductions (˜500 mV), as are required by CMOS devices with a mid-gap metal gate.
2. Discussion of the Prior Art
The foregoing objects and advantages of the present invention for a high performance CMOS device structure with a mid-gap metal gate may be more readily understood by one skilled in the art with reference being had to the following detailed description of several embodiments thereof, taken in conjunction with the accompanying drawings wherein like elements are designated by identical reference numerals throughout the several views, and in which:
FIG. 1 illustrates a CMOS structure having an NFET area on the left and a PFET area on the right, separated by shallow trench isolation (STI) area with a sacrificial oxide layer over the entire CMOS structure, and also illustrates an n dopant As being implanted into the NFET area.
FIG. 2 illustrates a masked etch of the sacrificial oxide layer from over PFET area while the sacrificial oxide layer over the NFET area is preserved by a photoresist mask thereover to prevent etching thereof.
The present invention provides a method for fabricating high performance CMOS devices with a mid-gap workfunction metal gate. The present invention uses the same metal with a mid-gap work function for the gate of both the PFET area and NFET area, and provides a device structure and fabrication method for CMOS devices with a mid-gap workfunction metal gate with an approximately 40 nm gate length.
For CMOS devices with a mid-gap workfunction metal gate, the threshold voltage Vt for both the PFET area and the NFET area become unacceptably high. The threshold voltage has to be adjusted downwardly by implanting a p-type dopant into the surface of the PFET area and an n-type dopant into the surface of the NEFT area. Ideally the dopant should be positioned right at the gate dielectric/silicon interface such that large shifts in the threshold voltage Vt are possible but short channel effects are not degraded. In practice this counter doping layer can have a finite thickness before short channel effects are degraded.
Process/device simulations have indicated that maintaining a junction depth of less than ˜100 A can lead to acceptable short channel effects and effective adjustment of the threshold voltage Vt. Acceptable Vt adjust and short channel effects can be obtained with a shallow As compensating implant for the NFET area (n-type compensating doping) as it is known that As diffusion is relatively slow.