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Techniques for Metal Gate Work Function Engineering to Enable Multiple Threshold Voltage Nanowire FET Devices

a technology of nanowires and function engineering, applied in the field of gate work function engineering, can solve the problems of multiple threshold voltage (vt) devices, becomes extremely problematic, and requires a substantial amount of process complexity

Active Publication Date: 2014-02-20
GLOBALFOUNDRIES US INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

The present invention provides techniques for engineering the gate work function in nanowire field-effect transistor (FET) devices. This is achieved by depositing a work function setting material that is proportional to the nanowire pitch. The method involves fabricating a nanowire FET device by etching nanowires and pads in a semiconductor layer on an insulator, forming interfacial oxide around each nanowire, depositing conformal gate dielectric and material over the nanowires, and depositing conformal first gate material and a second gate material to form at least one gate stack over the nanowires. The volume of the conformal gate material and work function setting material in the gate stack is proportional to the pitch of the nanowires. This invention allows for better control of the device's performance and reliability.

Problems solved by technology

One key problem with undoped devices is the implementation of multiple threshold voltage (Vt) devices.
To do so, however, for aggressively scaled devices has serious drawbacks from random dopant fluctuation (RDF) effects and becomes extremely problematic as the nanowire diameter is scaled.
This however requires a substantial amount of process complexity.

Method used

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  • Techniques for Metal Gate Work Function Engineering to Enable Multiple Threshold Voltage Nanowire FET Devices
  • Techniques for Metal Gate Work Function Engineering to Enable Multiple Threshold Voltage Nanowire FET Devices
  • Techniques for Metal Gate Work Function Engineering to Enable Multiple Threshold Voltage Nanowire FET Devices

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Embodiment Construction

[0017]As described above, there are notable disadvantages associated with using doping and / or different work function gate stacks to produce multiple threshold voltage (Vt) nanowire field-effect transistor (FET) devices. Advantageously, provided herein are techniques for producing multiple Vt nanowire FET devices using a work function setting material in an amount that is modulated as a function of nanowire pitch (wire to wire pitch, where the pitch is defined as the distance from the center of one nanowire to the adjacent nanowire(s)). Namely, a thickness of the materials in the device gate stacks will be chosen such that less work function setting material ends up in the tighter pitch nanowire FETs. Thus, for smaller pitch, higher nanowire FET Vt is obtained and therefore, through nanowire pitch variation, different Vt devices may be fabricated. The technique does come at the cost of significant reduction in active width density, however if the lower Vt (wider pitch) devices are n...

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Abstract

A method of fabricating a nanowire FET device includes the following steps. A SOI wafer is provided having a SOI layer over a BOX. Nanowires and pads are etched in the SOI layer. The nanowires are suspended over the BOX. An interfacial oxide is formed surrounding each of the nanowires. A conformal gate dielectric is deposited on the interfacial oxide. A conformal first gate material is deposited on the conformal gate dielectric. A work function setting material is deposited on the conformal first gate material. A second gate material is deposited on the work function setting material to form at least one gate stack over the nanowires. A volume of the conformal first gate material and / or a volume of the work function setting material in the gate stack are / is proportional to a pitch of the nanowires.

Description

FIELD OF THE INVENTION [0001]The present invention relates to nanowire field-effect transistor (FET) devices, and more particularly, to techniques for gate work function engineering using a work function setting material an amount of which is provided proportional to nanowire pitch so as to enable multiple threshold voltage (Vt) devices.BACKGROUND OF THE INVENTION[0002]In current complementary metal-oxide semiconductor (CMOS) scaling, the use of undoped gate all around (GAA) nanowire devices is a highly investigated structure as a device choice for future CMOS. One key problem with undoped devices is the implementation of multiple threshold voltage (Vt) devices. One solution is to dope the nanowire FET. To do so, however, for aggressively scaled devices has serious drawbacks from random dopant fluctuation (RDF) effects and becomes extremely problematic as the nanowire diameter is scaled. One can also engineer gate stacks with different work functions for different Vt's. This however...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01L21/336
CPCB82Y10/00B82Y40/00H01L29/4232H01L29/66439H01L29/775H01L29/0673H01L29/068H01L29/16H01L29/42392H01L29/78696
Inventor CHANG, JOSEPHINE B.LAUER, ISAACLIN, CHUNG-HSUNSLEIGHT, JEFFREY W.
Owner GLOBALFOUNDRIES US INC
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