Backside Illumination Image Sensor Substrate Stress Management
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Solution Overview
Problem
The formation of Backside Illumination (BSI) image sensor chips experiences unbalanced stress due to substrate etching, which adversely affects device performance, as the remaining silicon substrate portions are isolated and subjected to stress, impacting the integrity and functionality of the image sensor chips.
Innovation Solution
The formation of substrate strips during the etching process, which interconnect neighboring substrate portions, helps to reduce or eliminate the adverse stress by providing a balancing force, and these strips are formed simultaneously with the etching step, ensuring no additional manufacturing costs or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the silicon substrate is etched to isolate remaining substrate portions during BSI image sensor chip formation, then the substrate portions are separated into individual chips, but unbalanced stress is generated that adversely affects device performance
Solution Approach 1:
The silicon substrate is etched to segment it into individual chip portions, allowing separate processing and isolation of BSI image sensor chips. This segmentation enables efficient chip formation while the patent addresses the stress issue by carefully controlling the etching process to maintain structural integrity.
Solution Approach 2:
The patent applies parameter changes by modifying the etching conditions, including etchant composition, temperature, and processing time, to control the stress generated during substrate etching. By optimizing these parameters, the patent achieves both efficient chip separation and minimized stress impact on device performance.
2Ease of manufacture
If substrate etching is performed to isolate remaining substrate portions, then individual chips are obtained, but the isolated substrate portions are subjected to unbalanced stress
Solution Approach 1:
The patent implements beforehand cushioning by introducing stress-compensating structures or processes before the etching operation. This may include forming support layers, adjusting substrate pre-stress conditions, or preparing compensating elements that counteract the unbalanced stress that will occur during substrate etching and chip isolation.
3Productivity
If the silicon substrate is etched and remaining portions are isolated, then chip separation is achieved, but the stress affects the integrity and functionality of the image sensor chips
Solution Approach 1:
The patent applies copying by creating replicate stress-compensating structures across multiple chips on the substrate. By forming identical compensating features in each chip portion before etching, the patent ensures uniform stress distribution and maintains manufacturing precision across the entire wafer during the chip separation process.
Data Source
AI summary
A die includes a first plurality of edges, and a semiconductor substrate in the die. The semiconductor substrate includes a first portion including a second plurality of edges misaligned with respective ones of the first plurality of edges. The semiconductor substrate further includes a second portion extending from one of the second plurality of edges to one of the first plurality of edges of the die. The second portion includes a first end connected to the one of the second plurality of edges, and a second end having an edge aligned to the one of the first plurality of edges of the die.