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Method and System for a Conductive Cu Plug Cap for an Aluminum Pad Elimination Process

IP.com Disclosure Number: IPCOM000197736D
Publication Date: 2010-Jul-20
Document File: 5 page(s) / 147K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method and system for a conductive final wiring level Cu plug cap is disclosed, which enables the replacement of the final aluminum pad level in the BEOL process flow. A conductive layer is used together with a modified final-passivation level polyimide mask, to allow for protection of the underlying copper metal during polyimide cure, and for electrical isolation of the final connection contact structures.

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Method and System for a Conductive Cu Plug Cap for an Aluminum Pad Elimination Process

Disclosed is a method and system for a conductive final wiring level Cu plug cap which enables the replacement of the final aluminum pad level in the BEOL process flow. The method and system involves the use of a refractory metal layer deposited by Physical vapor deposition (PVD) processing to serve as the final copper cap layer after the passivation via Cu-plug processing is complete. The cap material can be TiW, TaN, TiN or any refractory metal layer. The final polyimide mask is modified to include a trench around each final via (or solder bump) location, such that after polyimide processing is complete, the refractory metal cap layer is exposed through the Polyimide trench. Subsequently, the C4 bump processing proceeds either with C4 electroplating or by a physical solder transfer process, such as C4NP. When the wet etch processing is performed in the patterning of the BLM Cu/TiW layer, the wet etch process is extended so as to remove the exposed refractory metal material within the polyimide trenches. This isolates the bump structures electrically from one another, without requiring the use of a unique aluminum pad level, mask and RIE process.

The method involves depositing 50-100nm of PVD refractory conductive layer in place of nitride cap over the hard dielectric passivation via wiring plug. This plug may be comprised of for example, TaN, Ta, TiW. Thereafter, a standard Polyimide level processing using modified PSPI mask with a trench around bump is performed. The trench is centered midway between adjacent bumps, of size varying from 5-30um. Subsequently, a standard C4 processing or either C4NP or C4...