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Rooted Refractory Metal On Al-Cu Semiconductor Structure for Improved Contact and Enhanced Electromigration Resistance

IP.com Disclosure Number: IPCOM000121715D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 43K

Publishing Venue

IBM

Related People

Estabil, J: AUTHOR [+6]

Abstract

A new preclean method is used to etch an aluminum surface prior to selective tungsten (W) deposition, resulting in a lower via resistance and improved electromigration resistance.

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Rooted Refractory Metal On Al-Cu Semiconductor Structure for Improved
Contact and Enhanced Electromigration Resistance

      A new preclean method is used to etch an aluminum surface
prior to selective tungsten (W) deposition, resulting in a lower via
resistance and improved electromigration resistance.

      Selective W is an economical technology for filling interlevel
vias; however, the contact resistance between W and Al-Cu is poor and
results in tailed distribution if deposition temperatures are not
high enough. This makes the technique more difficult to utilize in
manufacturing. A new preclean method shown will increase the apparent
contact area, producing low contact resistance and high
electromigration resistance so that chemical vapor deposition of
tungsten (CVD W) can be used in selective mode in manufacturing.

      Referring to the figure, first a preclean cycle consisting of a
wet etch of H2O2 + H2SO4 solution on Al-Cu is performed for one
minute to etch about 50 nm of Al-Cu. The etch attacks Al-Cu
isotropically, creating an encroached structure. Next, CVD W is
selectively grown on Al-Cu at wafer temperatures below 430 degrees C.
Since the diffusity of WF6 is very high, CVD W grows into the
encroached areas creating W roots. This technique increases the
apparent stud area, and the contact resistance is lower when compared
with blanket W. The resultant structure and process is compatible
with polyimide-Al-Cu dielectrics and helps to improve the per...