CMOS Image Sensor Bonding Interface With Metal Oxide Diffusion Barrier
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Solution Overview
Problem
Conventional solid state image sensors face issues with misalignment during wafer bonding, leading to reduced bonding strength and increased risk of copper diffusion into insulation layers, which can cause leakage and reduce reliability.
Innovation Solution
A semiconductor device with connection pads formed in interlayer films of two substrates and a metal oxide film formed between these pads and interlayer films, which is spontaneously formed through a heat treatment process, acting as a diffusion barrier and enhancing adhesion strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wafer bonding is performed without additional barrier structures, then the manufacturing process is simple, but copper diffusion into the insulation layer occurs causing leakage
Solution Approach 1:
A metal film is formed on the bonding surface before wafer bonding occurs. This preliminary action ensures that when bonding takes place, the metal film is already in position to react with the insulation layer and prevent copper diffusion, eliminating the need for complex post-bonding barrier structures
Solution Approach 2:
The insulation layer is subjected to heat treatment at specific temperatures (400-600°C) that trigger a chemical reaction between the metal film and the insulation layer. This parameter change transforms the insulation layer into a compound insulation layer with diffusion barrier properties, effectively preventing copper diffusion without adding complex structural elements
2Manufacturing precision
If misalignment occurs during wafer bonding, then bonding precision is reduced, but adhesion strength between connection pad and insulation layer is insufficient
Solution Approach 1:
The metal film acts as an intermediary layer between the connection pad and the insulation layer. Even when misalignment occurs during bonding, this intermediary layer reacts with the insulation layer to form a compound insulation layer that provides both mechanical adhesion and diffusion barrier functions, compensating for alignment errors
Solution Approach 2:
The insulation layer transforms into a composite structure (compound insulation layer) through chemical reaction with the metal film. This composite material has enhanced properties including improved adhesion strength and copper diffusion barrier capabilities, addressing both the precision and strength issues simultaneously
3Device complexity
If barrier metal is not provided at the connection pad interface, then the manufacturing process is simpler, but copper diffusion into the insulation layer occurs
Solution Approach 1:
The metal film serves multiple functions: it acts as a diffusion barrier, an adhesion promoter, and a reactant that transforms the insulation layer into a compound insulation layer. This multi-functionality eliminates the need for separate barrier metal layers, reducing device complexity while maintaining reliability
Solution Approach 2:
Heat treatment parameters are controlled to induce a chemical reaction between the metal film and the insulation layer, transforming the insulation layer into a compound insulation layer with inherent diffusion barrier properties. This parameter-driven transformation provides copper diffusion resistance without requiring additional barrier metal structures
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 metal oxide film effectively prevents copper diffusion and enhances adhesion strength, thereby improving the reliability of the semiconductor device by reducing the risk of leakage and electromigration.
Implementation Method 1
a metal oxide film which has been formed by a reaction between a metal film and an interlayer film
Implementation Method 2
by applying a heat treatment in a state where the first semiconductor substrate and the second semiconductor substrate are in close contact with each other with the metal film interposed between the first semiconductor substrate and the second semiconductor substrate
Data Source
AI summary
Connection pads are formed in interlayer films provided respectively in interconnection layers of a sensor substrate on which a sensor surface having pixels is formed and a signal processing substrate configured to perform signal processing on the sensor substrate to make an electrical connection between the sensor substrate and the signal processing substrate. Then, a metal oxide film is formed between the interlayer films of the sensor substrate and the signal processing substrate, between the connection pad formed on a side toward the sensor substrate and the interlayer film on a side toward the signal processing substrate, and between the connection pad formed on the side toward the signal processing substrate and the interlayer film on the side toward the sensor substrate. The present technology can be applied to a laminated-type CMOS image sensor, for example.