Bonding Pad Metal Layer Structure for Power Cycling Reliability
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Solution Overview
Problem
Semiconductor devices face limitations in power cycling capabilities due to mechanical constraints and thermal expansion issues at the wire to pad interface, leading to potential cracks and reduced reliability.
Innovation Solution
A semiconductor device structure incorporating a dielectric layer with a thickness ranging from 1% to 30% of the wiring metal layer thickness, electrically connecting the bonding pad metal layer, which is predominantly aluminum, to absorb stress and enhance mechanical tuning, thereby improving interconnect robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonds are used for interconnect, then current density is limited due to material heat up and thermal expansion, but using thicker metallization could improve current carrying capacity
Solution Approach 1:
The patent divides the bonding pad structure into multiple layers: a first bonding pad metal layer in direct contact with the wire bond, and a second bonding pad metal layer underlying the first layer. This segmentation allows each layer to handle different aspects of stress and current distribution, improving power cycling capability while managing thermal expansion effects.
Solution Approach 2:
The patent employs composite material structures by combining different metal layers (aluminum-based bonding pad layers) with specific dielectric layer structures. The dielectric layers with controlled thickness ratios (1% to 30% of wiring metal layer thickness) create a composite structure that optimizes both electrical performance and mechanical stress distribution under thermal cycling.
2Productivity
If bond feet density is increased to shrink device size, then current density requirements increase, but wire bonds become more prone to cracking under thermal stress
Solution Approach 1:
The patent transitions from a single-plane bonding pad structure to a multi-layer vertical structure. By stacking bonding pad metal layers and dielectric layers vertically, the design accommodates higher bond feet density while distributing mechanical stress across multiple dimensions, preventing crack propagation that would occur in planar configurations.
Solution Approach 2:
The patent modifies the dielectric layer thickness parameter to be specifically 1% to 30% of the wiring metal layer thickness. This parameter optimization allows the structure to maintain mechanical flexibility and stress distribution capabilities even as device size shrinks and bond feet density increases, preventing interconnect cracking.
3Ease of manufacture
If mechanical parameters of pad and wire are fixed, then manufacturing is simplified, but maximum energy application is limited to prevent cracking
Solution Approach 1:
The patent incorporates dielectric layer structures between the bonding pad metal layers, which act as cushioning elements before thermal and mechanical stresses can cause cracking. These dielectric layers absorb and distribute bond forces that arise during wire bonding and subsequent thermal cycling, preventing stress concentration that would lead to interconnect failure.
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 dielectric layer structure enhances the semiconductor device's power cycling capabilities by absorbing bond forces, reducing grain size, and preventing cracks, thus improving reliability and current density while allowing for thicker metallization without increasing chip cost.
Implementation Method 1
The intermediate dielectric layer structure may be configured to absorb bond forces
Implementation Method 2
The bonding pad metal layer structure is composed of aluminum by at least 50% of the amount of substance
Implementation Method 3
a dielectric layer structure arranged directly on the wiring metal layer structure
Data Source
AI summary
A semiconductor device is proposed. The semiconductor device includes a wiring metal layer structure. The semiconductor device further includes a dielectric layer structure arranged directly on the wiring metal layer structure. The semiconductor device further includes a bonding pad metal layer structure arranged, at least partly, directly on the dielectric layer structure. A layer thickness of the dielectric layer structure ranges from 1% to 30% of a layer thickness of the wiring metal layer structure. The wiring metal layer structure and the bonding pad metal structure are electrically connected through openings in the dielectric layer structure.