Solid-State Image Sensor Bonding Structure for Flat Copper Pad Interfaces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing bonding method for solid-state image pickup devices, particularly in CMOS type devices, fails to account for the thermal expansion mismatch between copper bonding pads and insulating films, leading to potential gaps and copper diffusion, which can result in white spots and reduced sensitivity.
Innovation Solution
A method involving a first substrate with photoelectric converters and a second substrate with peripheral circuits, where both substrates have wiring structures with concave portions containing conductive materials, allowing for a flat bonding plane by aligning the substrates such that the conductive material forms the bottom face of the concave portions, thereby minimizing thermal expansion-induced gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper bonding pads are used for bonding substrates, then electrical connection is achieved, but thermal expansion mismatch with insulating films causes gaps and copper diffusion
Solution Approach 1:
The patent changes the physical state and geometry of the bonding pad by forming a concave portion in the insulating film around the copper bonding pad. This structural parameter change allows the copper pad to be recessed below the insulating film surface, compensating for thermal expansion differences and preventing gap formation during bonding while maintaining electrical connection reliability
Solution Approach 2:
The concave portion is formed in advance before the bonding process. By pre-configuring the insulating film with a recessed area around the copper bonding pad, the patent ensures that thermal expansion during subsequent bonding or operation will not create gaps or cause copper diffusion, thus preventing defects before they occur
2Measurement precision
If pixel size is reduced to increase definition, then image resolution is improved, but light receiving area decreases and sensitivity drops
Solution Approach 1:
The patent applies different structural treatments to different parts of the pixel structure. Specifically, the insulating film is recessed only in the region surrounding the bonding pad while maintaining normal structure in other areas. This localized modification allows copper pads to be properly positioned without affecting the overall pixel design, enabling small pixel sizes to maintain both definition and sensitivity
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 approach ensures a gap-free bonding plane, enhancing the sensitivity and reliability of the solid-state image pickup device by preventing copper diffusion and maintaining a stable bonding interface.
Implementation Method 1
the relationship between the coefficient of thermal expansion of the copper bonding pad and that of the insulating film has not been studied, and a gap may be generated at a bonding plane after the bonding
Data Source
AI summary
A member for a solid-state image pickup device having a bonding plane with no gaps and a method for manufacturing the same are provided. The manufacturing method includes the steps of providing a first substrate provided with a photoelectric converter on its primary face and a first wiring structure, providing a second substrate provided with a part of a peripheral circuit on its primary face and a second wiring structure, and performing bonding so that the first substrate, the first wiring structure, the second wiring structure, and the second substrate are disposed in this order. In addition, at least one of an upper face of the first wiring structure and an upper face of the second wiring structure has a concave portion, and a conductive material forms a bottom face of the concave portion.