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Special Heat Treatment to Improve the Radiation Hardness of Mos Devices

IP.com Disclosure Number: IPCOM000101007D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Related People

Calise, J: AUTHOR [+3]

Abstract

High energy radiation incident on a MOSFET causes an increase in charge at a Si-SiO2 interface and a consequent degradation of device characteristics. A build-up of positive charge is controlled by the rate of hole trapping at a Si-SiO2 interface. The hole trapping rate at the interface is reduced when oxygen is added to a nitrogen ambient for a high-temperature post-oxidation anneal treatment of a MOSFET device. However, much of this improvement is lost during subsequent heat treatments of the type used in device processing.

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Special Heat Treatment to Improve the Radiation Hardness of Mos Devices

       High energy radiation incident on a MOSFET causes an
increase in charge at a Si-SiO2 interface and a consequent
degradation of device characteristics.  A build-up of positive charge
is controlled by the rate of hole trapping at a Si-SiO2 interface.
The hole trapping rate at the interface is reduced when oxygen is
added to a nitrogen ambient for a high-temperature post-oxidation
anneal treatment of a MOSFET device.  However, much of this
improvement is lost during subsequent heat treatments of the type
used in device processing.

      Improvements due to oxygen addition to the anneal ambient gas
are preserved and the sensitivity to subsequent heat treatments is
eliminated if argon is used as the carrier gas for oxygen instead of
nitrogen.  After annealing n-Si/SiO2 (50 nm)/Al capacitors in forming
gas at 400oC for 20 minutes, hole trapping rates are determined using
an avalanche injection technique in which a current is passed through
the SiO2 film for a set period of time.  This process is repeatedly
interrupted to monitor the flatband voltage shift as a function of
the avalanche time for hole injection.  The lower flatband voltage
shift, which results after avalanche injection into Si-SiO2
structures heat treated for 40 minutes at 1000oC in argon + 4.5%
oxygen (lower curve) when compared with heat treatments in nitrogen +
4.5% oxygen (upper curve), clearly demonstrates the advanta...