Vertically Stacked BSI Image Sensor with Carrier Support
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Solution Overview
Problem
The existing methods for forming Backside Illumination (BSI) image sensor chips face challenges in efficiently integrating image sensors and logic circuits while maintaining mechanical support during thinning, which affects the penetration of light and the overall performance of the chip.
Innovation Solution
A vertically stacked BSI image sensor chip is formed by bonding a BSI image sensor chip to a device chip, with vias and metal pads electrically connecting the two, allowing for independent optimization of logic circuit performance without compromising the image sensor chip's efficiency, and additional components like metal grids and micro-lenses are integrated on the top surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the silicon substrate is thinned to enable light penetration from the backside, then light capture efficiency is improved, but mechanical support is compromised
Solution Approach 1:
A carrier substrate is introduced as an intermediary element to provide mechanical support to the thinned silicon substrate during and after the thinning process. The carrier substrate acts as a mediator that compensates for the loss of mechanical strength while enabling the substrate to be thinned sufficiently for backside illumination operation.
2Device complexity
If image sensors and logic circuits are integrated on the same chip, then device complexity is reduced, but logic circuit performance optimization is limited
Solution Approach 1:
The device is segmented into two separate chips: an image sensor chip and a logic circuit chip. This segmentation allows each chip to be independently optimized for its specific function while maintaining a compact integrated structure through close coupling and interconnect structures.
3Reliability
If additional components like metal grids and color filters are added, then image sensor performance is improved, but manufacturing complexity increases
Solution Approach 1:
Additional components such as metal grids, color filters, and micro-lenses are pre-formed on the image sensor chip at defined stages during the manufacturing process. This preliminary action approach allows for systematic integration of multiple components without significantly increasing overall manufacturing complexity.
Data Source
AI summary
A method includes bonding a Backside Illumination (BSI) image sensor chip to a device chip, forming a first via in the BSI image sensor chip to connect to a first integrated circuit device in the BSI image sensor chip, forming a second via penetrating through the BSI image sensor chip to connect to a second integrated circuit device in the device chip, and forming a metal pad to connect the first via to the second via.