Browse Prior Art Database

Copper/Polyimide Structure with Selective Cu3Si/SiO2. Etch Stop

IP.com Disclosure Number: IPCOM000112585D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Cronin, JE: AUTHOR [+6]

Abstract

In the processing of copper interconnection structures on silicon chips with polyimide interlevel insulation, it is necessary to protect the surface of exposed copper lines or studs from oxidation during the plasma etching of the next level of polyimide (using an oxygen-containing etch gas). Present approaches usually require the deposition of an etch-stop layer of insulating material such as silicon nitride. The disadvantage of this material is that it remains in place in the final structure between the polyimide layers, and its high dielectric constant increases the capacitance between interconnection lines, thus slowing the operation of the chip.

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Copper/Polyimide Structure with Selective Cu3Si/SiO2.  Etch Stop

      In the processing of copper interconnection structures on
silicon chips with polyimide interlevel insulation, it is necessary
to protect the surface of exposed copper lines or studs from
oxidation during the plasma etching of the next level of polyimide
(using an oxygen-containing etch gas).  Present approaches usually
require the deposition of an etch-stop layer of insulating material
such as silicon nitride.  The disadvantage of this material is that
it remains in place in the final structure between the polyimide
layers, and its high dielectric constant increases the capacitance
between interconnection lines, thus slowing the operation of the
chip.

      The present invention eliminates the need for this high
dielectric constant etch-stop by providing a selectively-grown etch
stop material on the copper surface which protects the copper from
oxidation.  The etch stop material is copper silicide or copper
germanide.  The etch stop layer is formed by depositing a thin layer
(200-500 A) of silicon (or germanium) onto the exposed
copper/polyimide surface after a short sputter-clean.  By depositing
at 200-400ºC, the exposed copper reacts directly with the Si or
Ge to form Cu&sub3.Si or Cu&sub3.Ge.  These conducting compounds will
form selectively on the exposed Cu surfaces.  Alternatively, heating
the structure after deposition to 200-400ºC will form these
compounds selectively on the Cu...