Image Sensor Through-Via Keep-Out Zone Design
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Solution Overview
Problem
Existing image sensor devices face thermal stress issues from through-vias, which can negatively impact the performance of photodiodes in the pixel array region, and there is a need to optimize the design to avoid these deleterious effects while maintaining effective electrical connections.
Innovation Solution
The design optimizes the ratio of the through-via region's length to the keep-out zone's length between the through-via region and the pixel array region, ranging from 0.2 to 0.8, to minimize thermal stress and ensure improved performance, with through-vias arranged in columns and rows to provide vertical electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If through-vias are placed close to the pixel array region to reduce chip area, then chip area is saved, but thermal stress on photodiodes increases and pixel performance deteriorates
Solution Approach 1:
A keep-out zone is introduced as an intermediary region between the pixel array region and the through-via region. This keep-out zone acts as a buffer that isolates the photodiodes from thermal stress generated by through-vias, allowing the through-vias to be placed closer to the pixel array while maintaining pixel performance. The keep-out zone effectively mediates the conflict between chip area reduction and thermal stress reduction.
Solution Approach 2:
The design implements local quality by creating a specific region (keep-out zone) with different properties than the surrounding areas. Within this keep-out zone, through-vias are prohibited, creating a localized area free from thermal stress that protects the adjacent photodiodes. This allows different parts of the chip to have different characteristics - the pixel array region maintains high sensitivity while the through-via region can be densely packed.
2Reliability
If through-vias are arranged densely to improve electrical connections, then electrical connection efficiency is improved, but thermal stress on photodiodes increases
Solution Approach 1:
The keep-out zone serves as an intermediary buffer that allows dense through-via arrangements to be implemented without directly exposing photodiodes to thermal stress. The through-vias can be densely packed in their designated regions while the keep-out zone prevents thermal interference with the pixel array, thus maintaining both electrical connection efficiency and photodiode performance.
3Object-affected harmful factors
If keep-out zone size is increased to reduce thermal stress, then photodiode performance is maintained, but chip area increases
Solution Approach 1:
The patent applies parameter changes by optimizing the ratio of the keep-out zone length to the through-via region length within a specific range (0.2 to 0.8). This parameter optimization allows the keep-out zone to be sufficiently large to protect photodiodes from thermal stress while preventing excessive chip area consumption. By tuning this ratio parameter, the design achieves a balance between thermal protection and area efficiency.
Data Source
AI summary
A design method for an image sensor device includes providing an initial design for an image sensor device. The initial design includes a pixel array region and a through-via region disposed proximate the pixel array region. The initial design has a first length between the pixel array region and the through-via region. The initial design has a second length that is a width of the through-via region. The design method includes analyzing a ratio of the second length and the first length, and modifying the initial design to achieve a ratio of the second length and the first length within a particular range.