Methods for Transistor Formation Using Selective Gate Implantation

Abstract

Methods are disclosed for semiconductor device fabrication in which dopants are selectively implanted into transistor gate structures to counteract or compensate for dopant depletion during subsequent fabrication processing. A patterned implant mask is formed over a semiconductor device, which exposes at least a portion of the gate structure and covers the remaining upper surfaces of the device. Thereafter, dopants are selectively implanted into the exposed gate structure.

Description

RELATED APPLICATION [0001] This application is a Continuation-in-Part of Ser. No. 10 / 123,686, filed Apr. 16, 2002, which is entitled “METHODS FOR TRANSISTOR GATE FORMATION USING GATE SIDEWALL IMPLANTATION”.FIELD OF INVENTION [0002] The present invention relates generally to semiconductor devices and more particularly to methods for doping transistor gates in the manufacture of semiconductor devices. BACKGROUND OF THE INVENTION [0003] Field effect transistors (FETs) are widely used in the electronics industry for switching, amplification, filtering, and other tasks related to both analog and digital electrical signals. Most common among these are metal-oxide-semiconductor field-effect transistors (MOSFETs), wherein a doped polysilicon gate is energized to create an electric field within a semiconductor channel underlying the gate, by which current is allowed to conduct between doped source / drain regions formed in a substrate on either side of the channel. In order to provide a conduc...

AI Technical Summary

Benefits of technology

"The invention provides methods for fabricating semiconductor devices that mitigate the adverse effects of gate dopant depletion. This is achieved by selectively implanting extra dopants into the gate structure, using separate implantation steps to dope the transistor source / drain regions of the substrate. This selective implantation can be performed at any point in the fabrication process, and it allows for compensation for dopant depletion in subsequent processing. By providing extra dopants to the gate structure, the invention reduces poly depletion and increases gate capacitance, resulting in improved performance of semiconductor products. The selective implantation involves the use of a patterned implant mask, which is formed over the semiconductor device and used to selectively dope the gate structure. The mask can be made of various materials and can be removed after the implantation. Overall, the invention enables precise control over the doping concentrations and uniformity of both the source / drain regions of the substrate and the gate structure, allowing compensation for process-related dopant depletion from the gate."

Problems solved by technology

In addition, although generally scaled to be smaller, certain devices require larger feature sizes than others, including gate dimensions.

The increase in the effective thickness of the gate oxide under the inversion condition has the effect of an increase in threshold voltage and reduction in gate capacitance, in turn causing a reduction in transistor drive current and increased logic gate delay and processing time.

Images