3D Image Sensor Electrode Bonding Against Copper Pumping
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Solution Overview
Problem
In solid-state imaging devices with three-dimensional structures, bonding defects occur due to the copper pumping phenomenon during heat treatment after substrate bonding, leading to inadequate wafer bonding and electrical connection issues.
Innovation Solution
A diffusion preventing layer is formed between metal electrodes in at least one of the substrates, comprising a metal seed film and a diffusion preventing film, to restrict thermal expansion and reduce the volume of copper, thereby preventing copper pumping and enhancing bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment is performed after substrate bonding, then bonding strength is improved, but copper pumping occurs causing bonding defects
Solution Approach 1:
A diffusion preventing layer is introduced as an intermediary between the copper electrode and the surrounding structure. This layer mediates the thermal expansion behavior, allowing the copper to expand without causing pumping defects while still achieving strong bonding. The diffusion preventing layer absorbs or redistributes the thermal stress, preventing the harmful pumping effect during heat treatment.
Solution Approach 2:
The invention changes the physical parameters of the electrode structure by adding a diffusion preventing layer with specific material properties. This layer has controlled thickness and material composition that modifies the thermal expansion characteristics of the overall electrode structure, enabling heat treatment without copper pumping. The parameter change transforms the electrode from a pure copper structure to a composite structure with controlled thermal behavior.
2Reliability
If copper volume is increased for electrode bonding, then electrical connection is improved, but thermal expansion during heat treatment causes pumping defects
Solution Approach 1:
The invention changes the physical parameters of the electrode structure by adding a diffusion preventing layer with specific material properties. This layer has controlled thickness and material composition that modifies the thermal expansion characteristics of the overall electrode structure, enabling heat treatment without copper pumping. The parameter change transforms the electrode from a pure copper structure to a composite structure with controlled thermal behavior.
Solution Approach 2:
The electrode structure is transformed from pure copper to a composite structure consisting of copper and a diffusion preventing layer. This composite material approach allows the electrode to maintain good electrical conductivity from the copper while the diffusion preventing layer provides controlled thermal expansion properties, preventing pumping defects during heat treatment.
3Reliability
If diffusion preventing layer is added to prevent copper pumping, then bonding defects are reduced, but device structure becomes more complex
Solution Approach 1:
The diffusion preventing layer is applied locally only where needed - specifically at the electrode regions susceptible to copper pumping during heat treatment. This localized approach prevents copper pumping and bonding defects only in the critical areas, rather than requiring complex modifications throughout the entire device structure. The local quality principle maintains simplicity in non-critical areas while providing protection where required.
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 solution effectively reduces bonding defects by controlling thermal expansion and copper volume, ensuring precise electrode bonding and improved electrical connections between substrates.
Implementation Method 1
the diffusion preventing layer of the metal is formed for a layer formed with the metal filling a hole portion... to restrict thermal expansion and reduce the volume of copper
Implementation Method 2
a diffusion preventing layer of the metal is formed for a layer formed with the metal filling a hole portion... preventing copper pumping
Data Source
AI summary
Provided is a solid-state imaging device capable of reducing bonding defects when two substrates are bonded to each other, and a method for manufacturing the solid-state imaging device. The solid-state imaging device includes a first substrate including a first electrode formed with a metal, and a second substrate that is a substrate bonded to the first substrate, the second substrate including a second electrode formed with a metal, the second electrode being bonded to the first electrode. In at least one of the first substrate or the second substrate, a diffusion preventing layer of the metal is formed for a layer formed with the metal filling a hole portion, the metal forming the electrodes.