Browse Prior Art Database

Method for Direct Measurement of Extrinsic Resistance of Field-Effect Transistors

IP.com Disclosure Number: IPCOM000121137D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

El-Kareh, B: AUTHOR [+2]

Abstract

Extrinsic resistance (Rex) is defined as source or drain resistance outside an FET channel. By means of a test structure comprised of two FETs having a common source and separate gates and drains, Rex of one of the two FETs is measured as a function of gate voltage above threshold and drain current.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 88% of the total text.

Method for Direct Measurement of Extrinsic Resistance of Field-Effect
Transistors

      Extrinsic resistance (Rex) is defined as source or drain
resistance outside an FET channel.  By means of a test structure
comprised of two FETs having a common source and separate gates and
drains, Rex of one of the two FETs is measured as a function of gate
voltage above threshold and drain current.

      Referring to Fig. 1, test transistor T1 has drain conductor 2
contacting drain diffusion 4, gate electrode 6, and uses common
source diffusion 8 and source conductor 10. Sense transistor T2 uses
common source conductor 10 contacting source diffusion 8, and has
gate electrode 12, and drain diffusion 14 contacted by drain
conductor 16.

      Sense transistor T2 is first calibrated in the low
sub-threshold mode as a function of source-to-substrate reverse bias
(Vs).  This yields gate current vs. gate voltage characteristics with
Vs as a parameter, as shown in Fig. 2.  In practice, Rex does not
affect the subthreshold characteristics.  To measure Rex, transistor
T1 is driven into saturation at high current with the source
connected externally to ground potential, while transistor T2 is
measured in the low sub-threshold mode.  The voltage drop across Rex
causes the reverse voltage between source and substrate at source
boundary 18 to increase by Vs = Id(Rex), where Id is drain current.
Since boundary 18 is common to both transistors T1 and T2 and is
assumed to be an equip...