Dual Oxide Bonding Structure for High-Strength Wafer Bonding
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Solution Overview
Problem
Achieving a bond with sufficient bond strength, low stress, and high density thin films in chip-to-wafer and wafer-to-wafer bonding is challenging, as existing methods either result in insufficient bond strength or unacceptably high stress.
Innovation Solution
A bonding structure comprising a first oxide layer on a semiconductor substrate and a second oxide layer on top, where the second oxide layer has a higher stress level and density than the first oxide layer, and is thinner, providing enhanced bond strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick oxide layer is formed at low deposition temperature to prevent device damage, then the bond strength is insufficient, but if the oxide layer is made denser to increase bond strength, then the stress becomes unacceptably high
Solution Approach 1:
The bonding structure is divided into two distinct oxide layers: a first oxide layer (5000-15000 nm thick) formed at low temperature to protect devices, and a second oxide layer (250-750 nm thick) formed at higher temperature to provide high bond strength. This segmentation allows each layer to fulfill different functions without compromising the other, resolving the contradiction between bond strength and stress.
Solution Approach 2:
Different regions of the oxide structure have different properties: the first oxide layer has low stress and provides device protection, while the second oxide layer has high density and high bond strength. This local differentiation of material properties allows the system to achieve both low stress and high bond strength simultaneously.
2Strength
If a thick oxide layer is used for bonding, then the bond strength is insufficient, but if the oxide layer is made thinner and denser, then the bond strength increases while stress is reduced
Solution Approach 1:
The total oxide thickness is segmented into two layers with different thicknesses and properties. The first layer is thick (5000-15000 nm) to provide device protection, while the second layer is thin (250-750 nm) to achieve high bond strength with low stress. This segmentation resolves the contradiction between thickness and bond strength.
Solution Approach 2:
The bonding structure uses a composite of two oxide layers with different formation conditions and properties. The first layer provides mechanical protection and the second layer provides bonding functionality, creating a composite structure that achieves superior overall performance compared to a single uniform oxide layer.
3Strength
If conventional single-layer oxide bonding is used, then the bond strength is insufficient, but if a two-layer structure is implemented, then the bond strength increases to at least 1.0 Joules per square meter
Solution Approach 1:
The bonding structure is segmented into two oxide layers formed in sequence, where the first layer provides device protection and the second layer provides high-strength bonding. This segmentation achieves superior bond strength (≥1.0 J/m²) while maintaining process simplicity through sequential formation without requiring complex additional steps.
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 described bonding structure achieves a bond strength of at least 1.0 Joules per square meter, significantly higher than conventional thick oxide bonding layers, while maintaining low stress and high density, thus addressing the challenges of existing methods.
Implementation Method 1
a second oxide layer on the first oxide layer, the second oxide layer for bonding to another structure, wherein the second oxide layer has a higher stress level than the first oxide layer
Data Source
AI summary
A bonding structure for a semiconductor substrate and related method are provided. The bonding structure includes a first oxide layer on the semiconductor substrate, and a second oxide layer on the first oxide layer, the second oxide layer for bonding to another structure. The second oxide layer has a higher stress level than the first oxide layer, and the second oxide layer is thinner than the first oxide layer. The second oxide layer may also have a higher density than the first oxide layer. The bonding structure can be used to bond chips to wafer or wafer to wafer and provides a greater bond strength than just a thick oxide layer.