Projection-Depression Electrode Joining for Solid-State Imaging
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Solution Overview
Problem
In solid-state imaging elements with a three-dimensional structure, voids often form at the joining surface between electrodes, reducing the joining area and increasing contact resistance and peeling due to decreased mechanical strength.
Innovation Solution
The electrodes are designed as a projection electrode on the sensor substrate and a depression electrode on the circuit substrate, allowing for a larger joining area by fitting the projection electrode into the depression electrode, ensuring a substantial joining area even if voids occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heat treatment is performed in a state of electrodes on the sensor substrate and electrodes on the circuit substrate being opposed to each other, then the joining process is simplified, but voids occur at the joining surface reducing the joining area
Solution Approach 1:
The patent applies preliminary action by forming a projection on one electrode and a corresponding depression on the other electrode before the heat treatment joining process. This pre-structured geometry ensures that when the substrates are brought together for heat treatment, the projection fits into the depression, guiding proper alignment and preventing void formation at the joining surface, thus resolving the contradiction between process simplicity and joining quality.
2Ease of manufacture
If flat electrodes are used for joining, then the manufacturing process is simpler, but the joining area is reduced and contact resistance increases
Solution Approach 1:
The patent applies dimensionality change by transitioning from flat, two-dimensional electrode surfaces to three-dimensional structures with projections and depressions. This adds a vertical dimension to the electrode geometry, increasing the effective joining area and improving contact reliability while maintaining manufacturing feasibility through standard semiconductor fabrication techniques.
3Ease of manufacture
If the insulating film surrounding bonding pads is recessed to facilitate joining, then heat treatment effectiveness is improved, but voids still form at the joining surface
Solution Approach 1:
The patent applies the composite materials principle by combining the recessed insulating film structure with projection-depression electrode geometry. The composite structure integrates both the heat treatment facilitation (through insulating film recession) and the void prevention (through projection-depression fitting), achieving both goals simultaneously without compromising joining surface integrity.
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 configuration enhances the mechanical strength and reliability of the joining interface, reducing contact resistance and peeling, thereby improving the overall reliability of the solid-state imaging element.
Implementation Method 1
performing heat treatment in this state
Data Source
AI summary
A solid-state imaging element including: a sensor substrate in which a photoelectric conversion section is arranged and formed; a circuit substrate in which a circuit for driving the photoelectric conversion section is formed, the circuit substrate being laminated to the sensor substrate; a sensor side electrode drawn out to a surface of the sensor substrate on a side of the circuit substrate and formed as one of a projection electrode and a depression electrode; and a circuit side electrode drawn out to a surface of the circuit substrate on a side of the sensor substrate, formed as one of the depression electrode and the projection electrode, and joined to the sensor side electrode in a state of the circuit side electrode and the sensor side electrode being fitted together.