Rough Copper Metallization for Wire Bonding Reliability
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Solution Overview
Problem
Cu wire bonding processes for logic products face challenges such as metallization cracks and damage to underlying structures due to high bonding forces, and existing solutions like thick pads or tuned bond parameters are complex and costly, or not suitable for fine pitches.
Innovation Solution
A die structure with a metallization layer having a macroscopically rough surface profile, which increases the contact area and reduces bonding forces by distributing friction, allowing for lower bond parameter values and improved contact through ultrasonic wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high bond parameters (ultrasound, force, time) are used for Cu wire bonding, then welding reliability is improved, but mechanical stress increases causing metallization cracks and device damage
Solution Approach 1:
The invention changes the physical state of the Cu metallization surface from smooth to rough, creating a surface profile with peaks and valleys. This parameter change in surface topology allows for lower bond parameters (force, ultrasound, time) to achieve the same welding reliability, thereby reducing mechanical stress and preventing metallization cracks and device damage during Cu wire bonding
2Stability of the object's composition
If Cu based interconnect structures with thick pads or large pads are used, then stability against crack formation is improved, but device complexity and cost increase
Solution Approach 1:
The invention applies local quality by creating a rough surface profile specifically at the bonding site on the Cu pad, while maintaining the original pad thickness and overall structure. This localized surface modification provides crack resistance without requiring thick or large pads, thereby avoiding increased device complexity and cost
3Stability of the object's composition
If Cu based interconnect structures with large pads and large wires are used, then stability is improved, but suitability for fine pitch logic products decreases
Solution Approach 1:
The invention changes the surface topology parameter of the Cu pad from smooth to rough, which enhances bonding stability through increased contact area and friction. This allows the use of smaller pads and wires suitable for fine pitch logic products while maintaining bonding stability, avoiding the need for large pads and wires
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The rough surface profile enables optimal contact with lower bonding forces, reducing mechanical stress and preventing damage to the metallization and underlying structures, while maintaining stability and suitability for fine pitch logic products.
Implementation Method 1
increases the contact area and reduces bonding forces by distributing friction
Implementation Method 2
bonding forces by distributing friction, allowing for lower bond parameter values and improved contact through ultrasonic wire bonding
Data Source
AI summary
A die structure includes a die and a metallization layer disposed over the front side of the die. The metallization layer includes copper. At least a part of the metallization layer has a rough surface profile. The part with the rough surface profile includes a wire bonding region, to which a wire bonding structure is to be bonded.