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Method for a uniform Cu line at the scribe line to prevent cracks caused during wafer thinning in vertically stacked wafer technology

IP.com Disclosure Number: IPCOM000008914D
Publication Date: 2002-Jul-23
Document File: 3 page(s) / 98K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a uniform Cu line at the scribe line to prevent cracks caused during wafer thinning in vertically stacked wafer technology. Benefits include improved reliability.

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Method for a uniform Cu line at the scribe line to prevent cracks caused during wafer thinning in vertically stacked wafer technology

Disclosed is a method for a uniform Cu line at the scribe line to prevent cracks caused during wafer thinning in vertically stacked wafer technology. Benefits include improved reliability.

Background

              With conventional metal line design, wafer cracks occur when a bonded wafer is thinned down to approximately 10 µm. Cracks that start at the edge propagate toward the center of the wafer, following scribe lines (see Figure 1). Cracking occurs due to the lack of Cu lines at the scribe lines so that a large area is not bonded during the Cu-to-Cu bonding process. Creating a guard ring structure around a wafer edge prevents the oxidation of exposed Cu lines and improves mechanical integrity near the saw cut (see Figure 2). However, this structure does not prevent cracks caused by thinning at the scribe lines.

      Additional lithographical patterning at the edge of wafer reduces cracking (see Figure 3). However, patterning is an expensive solution due to additional litho steps.

Description

      The disclosed method is a uniform Cu metal line design to prevent wafer cracking along the scribe line caused during wafer-thinning techniques. Cracks propagate along the unbonded scribe lines during the thinning process. A uniform small-pitch Cu metal line with greater than 50 % density prevents cracking.

              The key element of the method includes uniform small-pitch Cu lin...