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AC MEASUREMENT OF MESFET RECESS PARAMETERS

IP.com Disclosure Number: IPCOM000006519D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-11
Document File: 1 page(s) / 80K

Publishing Venue

Motorola

Related People

J. Michael Golio: AUTHOR [+2]

Abstract

Conventional GaAs MESFET fabrication involves a recess gate etch step which must be tightly controlled. This etch is done to (1) increase breakdown voltage, (2) reduce access resistance and (3) improve the effective doping protile of the implanted active area Unfortunately, the control required to effectively implement this proc- ess step is often greater than can be accomplished in a high yield manufacturing environment.

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MOTOROLA INC. Technical Developments Volume 16 August 1992

AC MEASUREMENT OF MESFET RECESS PARAMETERS

by J. Michael Golio and George B. Norris

  Conventional GaAs MESFET fabrication involves a recess gate etch step which must be tightly controlled. This etch is done to (1) increase breakdown voltage, (2) reduce access resistance and (3) improve the effective doping protile of the implanted active area Unfortunately, the control required to effectively implement this proc- ess step is often greater than can be accomplished in a high yield manufacturing environment.

  In order to improve the control of the recess etch step, DC current-voltage measurement is oflen used to indicate when the etch process should be halted. To accomplish this, ohmic scwce and drain contacts as well as the active channel region are tirst fabricated on the wafer. A voltage is then applied between the source and drain contacts and the current is monitored. The active region is then etched until the current is reduced to some specified acceptable current level. Although simple semi- conductor theory would indicate that this process accu- rately controls the (doping density x epi-thickness) product of the device, the situation is complicated by the existence of slow acting surface, interface and bulk traps. These traps cause the DC electron transport char- acteristic to differ from the high frequency characteris-

tics. These differences are not generally predictable or repeatable. As a resul...