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A Rigid Pad-Backer for Orbital Chemical-Mechanical Polish Application

IP.com Disclosure Number: IPCOM000006604D
Publication Date: 2002-Jan-16
Document File: 2 page(s) / 23K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is pad backer for orbital chemical-mechanical polish (CMP) application for improved within-a-die (WID) variation.

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A Rigid Pad-Backer for Orbital Chemical-Mechanical Polish Application

Disclosed is pad backer for orbital chemical-mechanical polish (CMP) application for improved within-a-die (WID) variation.  

During orbital CMP polish, the high density (high density of oxide topography from metal lines) regions of a die will polish at a slower rate than the low density regions.  High-density regions polish at a slower rate because the surface area of a dense region is higher.  The higher surface area of the high-density region reduces the local pressure of the polish pad.  In contrast, isolated topography features on the die will have high local pressure.  As areas of varying density polish, a variation in oxide thickness is created (the WID variation).  With traditional pad backers for polish tools, WID variation post-oxide CMP (using orbital polishing) results in depth-of-focus issues at subsequent lithography steps.  Depth-of-focus issues are caused by flexing of the polishing pad.

Traditional pad backers for orbital polish pads are flexible.  Traditional pad backers provide flex so that a uniform pressure is applied across the wafer.  However, the flexible backer also allows the pad to deform over short distances (distances less than the size of the die), which results in larger WID variation.

Traditional pad backers are made of 0.20-inch thick hard urethane on top of a 0.1-inch thick stainless-steel plate (refer to FIG 1).  The urethane material is glued to the thin stainless material.  The urethane material also has machined grooves which are approximately 0.160-inch deep and 0.0625-inch wide.  The grooves are spaced approximately every 1.5 inches.  The grooves are cut in two directions.  One set of grooves is rotated 90 degrees from the other set of grooves.  The combination of the urethane material and the grid of grooves results in flex of the pad backer.  Under polishing pressure, flex of the pad backer allows...