Browse Prior Art Database

End Point Detection of Material Removal in Polishing Processes

IP.com Disclosure Number: IPCOM000119749D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 37K

Publishing Venue

IBM

Related People

Cote, WJ: AUTHOR [+4]

Abstract

By monitoring current drawn by a polishing wheel or rotating wafer carrier, completion of removal of a material from a high percentage of area of a surface is detected. For instance, removal of tungsten (W) from an insulating surface on a semiconductor wafer in planarizing for damascene wiring results in a large drop in current to the wafer carrier motor.

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End Point Detection of Material Removal in Polishing Processes

      By monitoring current drawn by a polishing wheel or rotating
wafer carrier, completion of removal of a material from a high
percentage of area of a surface is detected.  For instance, removal
of tungsten (W) from an insulating surface on a semiconductor wafer
in planarizing for damascene wiring results in a large drop in
current to the wafer carrier motor.

      In chemical/mechanical polishing (CMP) for planarizing wafer
surfaces in integrated circuit processing, current drawn by the motor
which rotates the wafer against a pad on a polishing wheel drops
significantly when W is removed from all but the recessed wiring
areas of the wafer surface. Power required to maintain wafer rotation
speed of the wafer is much less when the W is removed exposing an
insulator, e.g., silicon dioxide, to the polishing pad.  This power
or current drop is used to detect the point at which polishing must
be stopped to avoid over-polishing effects, e.g., metal dishing or
thinning.

      Amount of change in current at this end point may be maximized
by the use of relatively hard polishing pads, high rotation speed,
and low pressure between wafer and polishing pad.

      Planarization of surfaces without there being a change in
material exposed to the polishing pad may also be detected as a lower
carrier motor current drawn after surface roughness is reduced.

      Disclosed anonymously.