Hybrid Bonding Pad Distribution for Uniform Density and Routing
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Solution Overview
Problem
In wafer-to-wafer bonding, existing methods face challenges in achieving uniform pattern density and reducing defects like dishing and pattern-loading effects, which affect bonding strength and metal routing efficiency.
Innovation Solution
The use of hybrid bonding with uniformly distributed metal pads, including active and dummy pads, allows for improved planarity and reduced defects by increasing the metal pad width to spacing ratio, enabling closer pad placement and easier routing through the addition of dummy pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal pads are placed closer together to increase density, then routing efficiency improves, but dishing effects and pattern-loading defects increase
Solution Approach 1:
The patent applies homogeneity by distributing dummy metal pads throughout the die area to create uniform pattern density across the entire wafer surface. This uniform distribution ensures that each region experiences similar processing conditions during CMP, eliminating the dishing effects and pattern-loading defects that occur with non-uniform pad distributions, while still allowing high-density routing in specific areas.
2Ease of operation
If metal pad spacing ratio is increased to simplify routing, then routing ease improves, but bonding strength may be affected
Solution Approach 1:
The patent segments the metal pad distribution into two functional categories: active metal pads for electrical routing and dummy metal pads for process control. This segmentation allows active pads to be spaced farther apart for easier routing, while dummy pads fill the gaps to maintain uniform pattern density and ensure consistent CMP processing, thereby preserving bonding strength without compromising routing ease.
3Manufacturing precision
If dummy pads are added to uniformize pattern density, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent applies universality by designing dummy metal pads that are identical in structure and material to active metal pads. This multi-functionality approach allows the same pad structure to serve dual purposes: active pads provide electrical connectivity while dummy pads provide process control, eliminating the need for separate structural designs and simplifying the overall manufacturing process despite the increased number of pads.
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
This approach enhances bonding strength, reduces defects, and simplifies metal routing by maintaining consistent contact resistance even with misalignment, while allowing for a higher metal pad spacing ratio without increasing dishing effects.
Implementation Method 1
In the hybrid bonding, the metal pads of two wafers are bonded to each other through direct metal-to-metal bonding
Implementation Method 2
In the fusion bonding, an oxide surface of a wafer is bonded to an oxide surface or a silicon surface of another wafer
Implementation Method 3
In the eutectic bonding, two eutectic materials are placed together, and are applied with a high pressure and a high temperature. The eutectic materials are hence molten. When the melted eutectic materials are solidified, the wafers are bonded together
Data Source
AI summary
A chip includes a semiconductor substrate, integrated circuits with at least portions in the semiconductor substrate, and a surface dielectric layer over the integrated circuits. A plurality of metal pads is distributed substantially uniformly throughout substantially an entirety of a surface of the chip. The plurality of metal pads has top surfaces level with a top surface of the surface dielectric layer. The plurality of metal pads includes active metal pads and dummy metal pads. The active metal pads are electrically coupled to the integrated circuits. The dummy metal pads are electrically decoupled from the integrated circuits.