Browse Prior Art Database

Silicide Formation Process Monitor

IP.com Disclosure Number: IPCOM000121253D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 79K

Publishing Venue

IBM

Related People

Halbout, JM: AUTHOR [+3]

Abstract

A noncontact technique is described for monitoring the formation and evolution of a silicide layer at the buried interface between a metal and silicon.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Silicide Formation Process Monitor

      A noncontact technique is described for monitoring the
formation and evolution of a silicide layer at the buried interface
between a metal and silicon.

      The technology of device fabrication relies on low resistivity
silicides for the device contacts.  The process for silicide
formation consists of cleaning the silicon surface, depositing a
layer of, e.g., Pt, Ti, Co, W, and heating the wafer.  The silicide
grows from the metal silicon interface until the entire metal layer
is consumed. Fig. 1 gives a schematic cross-sectional representation
of this process.

      Monitoring the successful completion of the silicide reaction
usually requires a resistivity measurement, which can only be applied
after further device fabrication and needs physical contact to the
device.  We describe a contactless measurement technique which is
capable of monitoring the growth of the silicide front towards the
top metal surface.  The technique can be implemented in situ inside a
growth furnace for dynamic feedback on the process evolution with
time.

      The method relies on picosecond ultrasonics, which is described
in detail in [1-3].  In brief, a picosecond or subpicosecond laser
pulse impinges on a metal surface where, upon being absorbed, it
generates a transient shear wave (or ultrasonic wave) which
propagates into the metal film.  Fig. 2 represents schematically the
situation.  When this wave encounters an interface, it is partially
reflected and, as this reflected wave reaches the top surface, it
modulates the optical reflectivity of this surface.  This
reflectivity is monitored by a time-delayed replica of the incident
excitation pulse as a function of the delay between excitation and
probe.  The measurement of the delay locates the position of the
interface into the...