Hybrid Bonding Pad Layout for Uniform Pattern Density
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Solution Overview
Problem
Existing wafer-to-wafer bonding technologies face challenges in achieving uniform distribution of metal pads, leading to issues such as dishing effects and reduced contact areas due to misalignment, which affect bonding strength and resistance.
Innovation Solution
Implementing a hybrid bonding method with uniformly distributed metal pads, including both active and dummy pads, which are uniformly shaped and sized, and aligned to form consistent patterns, allowing for easier metal routing and improved bonding through fusion and metal-to-metal connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal pads are densely distributed on wafer surfaces, then bonding strength is improved, but dishing effects and manufacturing complexity increase
Solution Approach 1:
The patent segments the metal pad structure into two distinct types: through-pads that extend through the entire wafer thickness, and partial pads that exist only on the surface. This segmentation allows different regions of the wafer to have different pad configurations, optimizing bonding strength where needed while reducing dishing effects in other areas, thereby resolving the contradiction between bonding strength and manufacturing complexity
Solution Approach 2:
The patent applies local quality by creating non-uniform metal pad distributions across the wafer surface. Through-pads are strategically placed in regions requiring enhanced bonding strength, while partial pads are used in areas where dishing effects are less critical. This localized differentiation allows the system to achieve high bonding strength overall while minimizing manufacturing complexity and dishing in specific regions
2Strength
If metal pads are placed closer together, then bonding strength is improved, but contact resistance increases
Solution Approach 1:
The patent transitions from a two-dimensional surface-only pad configuration to a three-dimensional structure by extending certain pads through the entire wafer thickness. This dimensional change allows pads to be placed closer together on the surface for improved bonding strength, while the through-pads provide extended contact paths that maintain low contact resistance despite reduced spacing
3Manufacturing precision
If uniform metal pad distribution is achieved, then manufacturing precision is improved, but pattern density uniformity becomes difficult to maintain
Solution Approach 1:
The patent segments the pad distribution pattern into uniform grids of through-pads combined with strategically placed partial pads. The through-pads form a regular, uniform pattern that ensures consistent alignment and manufacturing precision, while the partial pads are added in specific locations to maintain overall pattern density uniformity without disrupting the underlying grid structure
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
Enhances bonding strength and reduces defects like air bubbles and dishing effects, enabling closer pad placement without increasing contact resistance, thus improving the efficiency and reliability of wafer bonding processes.
Implementation Method 1
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 2
The eutectic materials are hence molten. When the melted eutectic materials are solidified, the wafers are bonded together
Implementation Method 3
two metal pads are pressed against each other at an elevated temperature, and the inter-diffusion of the metal pads causes the bonding of the metal pads
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.