Bonding Pad Terrace Structure for Flare Reduction in Imaging Sensors
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Solution Overview
Problem
Imaging elements, such as CCD and CMOS sensors, experience flare issues due to light reflection at the bottom surface of shallow openings in the bonding pad structure, which affects photoelectric conversion units.
Innovation Solution
The imaging element design incorporates a bonding pad section with a first opening exposing a pad electrode and a shallower second opening surrounding it, featuring a terrace surface with multiple materials of different refractive indices, which reduces light reflection by diffusing and scattering incident light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shallow opening is provided around the pad opening to prevent capillary contact, then wire bonding reliability is improved, but light reflection at the bottom surface causes flare
Solution Approach 1:
The patent applies local quality by creating a terrace structure where different regions have different properties. The bottom surface of the shallow opening is structured to have multiple materials with different refractive indices, making each local region serve a specific function: some areas reflect light away from the photoelectric conversion unit while others allow light transmission, thus preventing flare locally without affecting the overall wire bonding structure
Solution Approach 2:
The patent uses composite materials by incorporating multiple materials with different refractive indices at the bottom surface of the shallow opening. This composite structure includes materials such as silicon oxide, silicon nitride, and other dielectric materials that work together to control light reflection and refraction, preventing flare while maintaining the structural integrity needed for wire bonding
2Reliability
If the pad opening is formed deep to expose the pad electrode, then electrical connection is improved, but the capillary contacts the edge of the opening during bonding
Solution Approach 1:
The patent applies the nested doll principle by creating a multi-level structure where the first opening (deep pad opening) is nested within the second opening (shallower opening). This nested configuration allows the deep first opening to expose the pad electrode for electrical connection while the shallower second opening surrounds it to prevent capillary contact, with both openings working together in a hierarchical arrangement
3Object-affected harmful factors
If a terrace structure with multiple materials is formed, then light reflection is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the terrace structure with multiple materials during the semiconductor fabrication process before the wire bonding step. The multi-material structure is prepared in advance using standard semiconductor manufacturing techniques such as selective epitaxial growth, chemical vapor deposition, or atomic layer deposition, so that when light incident occurs during operation, the pre-formed terrace structure is already in place to control light reflection without requiring additional complex manufacturing 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
This configuration effectively minimizes flare caused by light reflection, improving image quality by scattering reflected light and reducing its impact on the photoelectric conversion unit.
Implementation Method 1
a surface of a terrace in the bonding pad section is formed such that multiple types of materials are exposed
Implementation Method 2
multiple types of materials are exposed
Data Source
AI summary
A photoelectric conversion unit that outputs an image signal according to received light and a bonding pad section are disposed on one surface side of the substrate, and the bonding pad section has at least: a first opening provided to expose a pad electrode at a bottom; and a second opening that is arranged to surround the first opening and that is shallower than the first opening. The surface of a terrace in the bonding pad section is formed such that multiple types of materials are exposed.