Image Sensor Bonding Structure With Copper Diffusion Barriers
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Solution Overview
Problem
The bonding method in existing solid-state image pickup devices using copper can lead to metal impurity diffusion, causing dark current and leakage current, resulting in image defects and operational failures, especially in devices with a large number of pixels.
Innovation Solution
A solid-state image pickup device design where the conductive bonding portions are surrounded by diffusion-preventing films, preventing copper diffusion and thus suppressing the generation of dark and leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper bonding pad is used for bonding in solid-state image pickup device, then electrical connection is achieved, but metal impurity diffusion occurs causing dark current and leakage current
Solution Approach 1:
A barrier metal layer is introduced as an intermediary between the copper bonding pad and the semiconductor substrate. This barrier metal prevents direct contact and diffusion of copper atoms into the semiconductor region, thereby eliminating the harmful effect of metal impurity diffusion while maintaining the electrical connection function of the bonding pad.
Solution Approach 2:
The copper bonding pad is extracted from direct contact with the semiconductor substrate by removing the harmful diffusion pathway. The barrier metal layer separates the copper from the semiconductor region, taking out the problematic interaction while preserving the necessary electrical connection through the barrier metal interface.
2Measurement precision
If pixel size is reduced to achieve high definition images, then resolution is improved, but light receiving area decreases reducing sensitivity
Solution Approach 1:
The patent applies different structural qualities to different regions: the pixel region maintains small size for high resolution, while the bonding pad region uses a multi-layer structure with barrier metal to prevent impurity diffusion. This local differentiation allows small pixels to maintain sensitivity by preventing contamination from bonding materials, thus resolving the contradiction between small size and detection 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 design effectively reduces dark and leakage currents, enhancing the reliability and performance of solid-state image pickup devices by preventing metal impurity diffusion.
Implementation Method 1
the conductive material of the first bonding portion and the conductive material of the second bonding portion are surrounded with diffusion preventing films
Data Source
AI summary
A solid-state image pickup device capable of suppressing the generation of dark current and/or leakage current is provided. The solid-state image pickup device has a first substrate provided with a photoelectric converter on its primary face, a first wiring structure having a first bonding portion which contains a conductive material, a second substrate provided with a part of a peripheral circuit on its primary face, and a second wiring structure having a second bonding portion which contains a conductive material. In addition, the first bonding portion and the second bonding portion are bonded so that the first substrate, the first wiring structure, the second wiring structure, and the second substrate are disposed in this order. Furthermore, the conductive material of the first bonding portion and the conductive material of the second bonding portion are surrounded with diffusion preventing films.