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Method for the formation of wafer sawing fiducial marks on the wafer backside to enable backside wafer dicing

IP.com Disclosure Number: IPCOM000019835D
Publication Date: 2003-Oct-01
Document File: 4 page(s) / 93K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the formation of wafer sawing fiducial marks on the wafer backside to enable backside wafer dicing. Benefits include improved functionality, improved process simplicity, and improved yield.

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Method for the formation of wafer sawing fiducial marks on the wafer backside to enable backside wafer dicing

Disclosed is a method for the formation of wafer sawing fiducial marks on the wafer backside to enable backside wafer dicing. Benefits include improved functionality, improved process simplicity, and improved yield.

Background

The disclosed method addresses the problem of the formation of wafer sawing fiducial marks on the wafer backside to enable wafer backside dicing for thinned wafers.

         With the conventional back-side metallization (BSM) tool, a wafer-mask ring prevents deposition in the edge-exclusion region of the wafer. Modification of these mask rings is relatively straightforward. It accommodates small differences in the size of the wafers, such as 300-mm vs. 304-mm diameter wafers. The mask rings consist of two parts: a base ring in which the wafer is placed, and the actual mask ring, which is placed over the wafer.

An alternative approach used for the backside dicing of some thinned wafers is to find the saw streets using an infrared (IR) camera. However, this approach does not work with BSM because it is opaque to IR light.

Wafer dicing from backside of a wafer which has BSM requires an approach for recognizing the sawing streets from the backside of the thinned wafers.        

General description

         The disclosed method transfers fiducial marks for dicing streets from the front to the back of wafers. The method is used with wafers that are rendered opaque by BSM deposition.

         The disclosed method adds matched front-side and back-side alignment marks, such as teeth projecting from the inside edge of the ring, on the wafer mask ring. A vision or other system aligns the front-side fiducial marks to the wafer front-side dicing streets as the wafer is mounted backside-up in the mask ring. The corresponding back-side alignment marks on the ring mask the BSM deposition on the backside, providing reference points for aligning the saw with the streets from the wafer backside.

         The key elements of the method include:

•         Design of a mask ring, which has matched front and back alignment marks

•         Use of the mask ring to transfer fiducial marks for sawing streets from the wafer frontside to the wafer backside

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