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Reinforcement Structures to Enable Bonding on Fragile ILD Layers

IP.com Disclosure Number: IPCOM000084987D
Publication Date: 2005-Mar-02
Document File: 2 page(s) / 217K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that inserts metal pillars under the probing and bonding pads. Benefits include reducing stress and preventing pullout and cohesive failures.

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Reinforcement Structures to Enable Bonding on Fragile ILD Layers

Disclosed is a method that inserts metal pillars under the probing and bonding pads. Benefits include reducing stress and preventing pullout and cohesive failures.

Background

Bond and probing pads located over fragile ILD layers can cause the ILD to break (see Figure 1). To address this problem, the following solutions are implemented:

§         Using high lead bumps (instead of copper bumps) to reduce stress on the underlying structures in the device 

§         Increasing the BLM diameter (this increases the minimum bump pitch)

§         Minimizing the undercut on the BLM (this requires tighter process control and/or different equipment)

General Description

The disclosed method uses a set of metal pillars to re-enforce the ILD; this mitigates any stress concentration sites, resulting in less overall stress under the bump and a lower critical adhesion needed for reliability (see Figure 2). The metal pillars extend beyond the perimeter of the BLM in the final metal layer to avoid stress concentration points under the BLM. The metal coverage can be accomplished through other structures as long as the metal density is sufficient to avoid stress concentration points under the BLM.

Advantages

The disclosed method reduces stress and prevents pullout and cohesive failures. The disclosed method also requires no changes to the present design.

Fig. 1

Fig. 2

Disclosed anonymously