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BCB Surface Roughening for Improving Metal Adhesion Via Cryogenic CO2

IP.com Disclosure Number: IPCOM000018755D
Publication Date: 2003-Aug-06
Document File: 2 page(s) / 70K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that improves the adhesion between the metal layer and the BCB layer (for RDL applications), by using cryogenic CO2 to roughen the BCB surface. Benefits include an increased contact surface between the metal and BCB layers.

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BCB Surface Roughening for Improving Metal Adhesion Via Cryogenic CO2

Disclosed is a method that improves the adhesion between the metal layer and the BCB layer (for RDL applications), by using cryogenic CO2 to roughen the BCB surface. Benefits include an increased contact surface between the metal and BCB layers.

Background

During this process, poor adhesion can weaken the metal stacks used in forming redistribution traces to the underlying BCB layer during wire bond application of RDL. (See Figure 1 for an example of the current state of the art.) Currently, no solution exists to solve this poor adhesion between the metal and BCB layer.

General Description

The concept of roughening a surface to increase surface area and improve the mechanical “locking” of two dissimilar materials is widely used in many thin film technologies. In the disclosed method, cryogenic CO2 is used to mechanically roughen the surface. (This is conceptually similar to sand blasting.)  Cryogenic CO2 uses frozen CO2 as the hard penetrating media, thus eliminating the surface contamination associated with normal sand blasting. See Figures 2 and 3 for a detailed process flow.

Advantages

The disclosed method increases the contact surface between the metal and BCB layers, and eliminates the surface contamination associated with normal sand blasting.

Fig. 1

Fig. 2

Fig. 3

Disclosed anonymously