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Wet Forming Gas Anneal to Remove Radiation Damage from Polysilicon Gate MOSFETS

IP.com Disclosure Number: IPCOM000051203D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Aitken, JM: AUTHOR [+3]

Abstract

Processes such as electron-beam lithography or electron-gun metal evaporation are currently in use in advanced MOSFET (metal oxide semiconductor field-effect transistor) processing. These processes introduce damage into the gate oxides of the devices which impact the operating voltages and stability of the devices if not removed. However, because of metallurgical limitations, anneal temperatures are limited once the contact metal is in place and junction depth and contact resistance limit the final metal anneals to around 400 degrees C.

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Wet Forming Gas Anneal to Remove Radiation Damage from Polysilicon Gate MOSFETS

Processes such as electron-beam lithography or electron-gun metal evaporation are currently in use in advanced MOSFET (metal oxide semiconductor field-effect transistor) processing. These processes introduce damage into the gate oxides of the devices which impact the operating voltages and stability of the devices if not removed. However, because of metallurgical limitations, anneal temperatures are limited once the contact metal is in place and junction depth and contact resistance limit the final metal anneals to around 400 degrees C.

It is known that hydrogen is superior over forming gas ambients for such an anneal with polysilicon gate MOSFETs in this temperature range. However, pure hydrogen is a safety hazard and must be used with care. This article teaches that the addition of water vapor to forming gas (90 percent H ; 10 percent H ) provides an annealing ambient which is almost as effective as pure hydrogen in removing positive charge and neutral electron traps from irradiated polysilicon gate MOSFETs. Experimental data is given below for the positive and neutral trap densities measured in polysilicon gate MOSFETs metallized in an E-gun evaporation system and subjected to various anneals. The data demonstrates that the addition of water vapor to the 90 percent N(2), 10 percent H forming gas mixture dramatically effects its ability to anneal radiation damage.

These anneals prov...