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On Chip Electromigration Sensor using Silicon Device

IP.com Disclosure Number: IPCOM000108288D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 94K

Publishing Venue

IBM

Related People

Hsieh, CM: AUTHOR [+2]

Abstract

A new method for detecting, evaluating and measuring the electromigration of metal lines and interlevel studs is proposed. This method is sensitive, effective and convenient. It can sense the progress of metal migration well before an open circuit is resulted during an accelerating high current density and high temperature testings. This is the application of the fact that the I-V characteristics of a diode are changed when it is under mechanical stress.

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On Chip Electromigration Sensor using Silicon Device

       A new method for detecting, evaluating and measuring the
electromigration of metal lines and interlevel studs is proposed.
This method is sensitive, effective and convenient.  It can sense the
progress of metal migration well before an open circuit is resulted
during an accelerating high current density and high temperature
testings.  This is the application of the fact that the I-V
characteristics of a diode are changed when it is under mechanical
stress.

      As the integrated circuit density becomes denser, the metal
lines narrower and the interlevel studs smaller, the electromigration
problem becomes more important.  The conventional method to stress
the metal stripe and interlevel stud for electromigration is by
applying high current density and high temperature.  The line and
stud resistances are measured periodically.  Sometimes, 1/f noise is
also measured for "hair-line" crack.  If the electromigration is
severe, the line or stud becomes an open circuit.  However, in many
cases, the metal mass will migrate at a very slow rate.  The
resistance or noise measurement may not have a noticeable change, and
it may be difficult to evaluate the results after long hours of
stress testing.

      It is well known that mechanical stress on silicon will cause
the change in energy bandgap.  The bandgap of silicon decreases as
the pressure increases.  Its sensitivity is dEg/dP =
-2.4E-6eV/(Kg/cm2) (1).  Note that the forward collector current of a
transistor depends exponentially on the bandgap of the material.
Therefore, the collector current of a silicon transistor is an
exponentially increasing function of pressure.

      The shift of I-V characteristics of a diode subjected to
various degrees of mechanical stress has been shown in (2).  Figu...