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NiCu/NNiV BLM to Eliminate BLM Delamination Failures

IP.com Disclosure Number: IPCOM000101583D
Publication Date: 2005-Mar-16
Document File: 2 page(s) / 50K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that deposits a top layer of NiCu/NNiV on the BLM stack-up to reduce BLM delamination failures.

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NiCu/NNiV BLM to Eliminate BLM Delamination Failures

Disclosed is a method that deposits a top layer of NiCu/NNiV on the BLM stack-up to reduce BLM delamination failures.

Background

One of the major BLM reliability issues is oxidation and the subsequent cracking of the V-rich layer in the stack-up, resulting in high levels of dark bumps in CSAM during testing. The current BLM stack-up consists of a Ti1-Al-Ti2-NNiV sputter deposited in layers (see Figure 1). The V-rich layer develops as the Ni is consumed, forming the Ni-Sn IMC during wafer reflow and the subsequent assembly processes. During testing, this porous V-rich layer oxidizes, and either cracks or delaminates from the underlying BLM layer. Figure 2 shows the severity of this delamination. Currently, only a 4000A NiV layer is sputtered as the top layer on the BLM.

General Description

The disclosed method minimizes Ni consumption in the NNiV layer by sputtering a sacrificial NiCu layer on top of the NNiV (see Figure 3). This in turn eliminates the formation of the V-rich layer in the NiV, which leads to the BLM delamination failures.

Note.  A 50-50 wt% Ni-Cu sputtering target is used to sputter the NiCu top layer.

V is present in the Ni to make the Ni target non-magnetic and to improve the sputter rates.

N is present in the NiV layer to slow down the kinetics if the NiSn IMC reaction, as well as the vanadium oxidation reaction.

Advantages

The deposition of NiCu alloy film over the existing NiV BLM layer allows the Sn...