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Corroded Copper Fuse

IP.com Disclosure Number: IPCOM000234564D
Publication Date: 2014-Jan-17
Document File: 3 page(s) / 86K

Publishing Venue

The IP.com Prior Art Database

Abstract

Metal fuses are used in integrated circuits to program circuits, encode serial numbers, or add other features to integrated circuits. These fuses are difficult to program with a laser because they are inherently reflective, especially at the IR wavelengths used by the preferred lasers. This high reflectivity forces the use of high power to program the fuse, and exposure to high laser power places the rest of the integrated circuit at greater risk of collateral damage when the fuse is blown.

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Corroded Copper Fuse

Abstract

Metal fuses are used in integrated circuits to program circuits, encode serial numbers, or add other features to integrated circuits. These fuses are difficult to program with a laser because they are inherently reflective, especially at the IR wavelengths used by the preferred lasers. This high reflectivity forces the use of high power to program the fuse, and exposure to high laser power places the rest of the integrated circuit at greater risk of collateral damage when the fuse is blown.

We propose a method for forming low reflectivity/high absorptivity copper metal fuses by exposing the fuse to a corrosion environment during the wafer process. This enables a lower laser power setting, reducing stress on circuits near the fuses, resulting in higher product yield.

Introduction

The process of rupturing metal fuses using a laser is common throughout the integrated circuit industry, but the process suffers from difficulty because of the high power required to melt and program the fuse. This is especially true of thick metal fuses, which require even higher laser power settings to program the thick fuses. When high laser power is used, there is a significant risk of damaging the circuitry below or near the metal fuse, so a method of allowing a lower energy laser to be used would be beneficial.

 

Design and Implementation

We propose corroding the copper fuses before laser programming. Sulfate and Chloride containing environments will accomplish this. This will reduce the reflectivity of the exposed copper fuse, making it absorb the laser energy more efficiently. Because it absorbs the laser more efficiently, the corroded copper fuse will melt more quickly and at lower laser power setting than an uncorroded fuse.

Figure 1 below shows the reflectivity of a clean Copper surface (upper graph) and the reflectivity of corroded Copper is shown in the bottom graph of f...