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Cu landing pad with polyimide cap on crack stop

IP.com Disclosure Number: IPCOM000225385D
Publication Date: 2013-Feb-12
Document File: 2 page(s) / 45K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a landing pad structure where the crack stop and the kerf are passivated.

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This is the abbreviated version, containing approximately 100% of the total text.

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Cu landing pad with polyimide cap on crack stop

Cu landing pads under solder bumps improve the electromigration lifetime. To reduce cost, it is desirable to form these structures without an Al landing pad (i.e., replace Al landing pad with Cu landing pad). However, the elimination of the Cu landing pad results in unpassivated Cu in the crack stop and in the kerf, which can lead to problems with corrosion and other defects. Hence, a Cu landing pad structure where the crack stop and the kerf are passivated is needed.

This invention uses a two-step final via (FV) etch to remove thick hard dielectric layers (SiO2 and SiN) over the crack stop by leaving polymide (or thin SiN + polyimide) as a capping layer over the crack stop. This allows Cu landing pads to be used for solder bumps, while still protecting the crack stop from corrosion during processing and during device operation.

Figure 1: Invention 1; Dual FV; polyimide passivation of crack stop

Figure 2: Invention 2; Dual FV; thin SiN passivation of crack stop

Figure 3: Invention 2; process flow

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