Chip-Scale Lens Layer for CMOS Image Sensor Isolation and Light Leakage
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Solution Overview
Problem
The manufacturing process of CMOS image sensors faces challenges in achieving efficient electrical isolation and minimizing light leakage, which affects the image sensor's performance.
Innovation Solution
The process involves forming isolation structures, such as shallow trench isolations (STI) and deep trench isolations (DTI), within the semiconductor substrate to enhance electrical isolation. Additionally, a lens layer with a single lens portion is formed on the image capture chip using a patterned mask layer with varying pattern density, allowing for direct contact with the chip and eliminating the need for an external lens module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation structures are formed in the semiconductor substrate, then electrical isolation is improved, but device complexity increases
Solution Approach 1:
The isolation structure is divided into two distinct segments: a shallow trench isolation (STI) structure formed in the first substrate region, and a deep trench isolation (DTI) structure formed in the second substrate region. This segmentation allows each isolation structure to be optimized for its specific function - STI for general electrical isolation and DTI for enhanced light leakage prevention - thereby improving overall reliability while managing complexity through functional specialization.
Solution Approach 2:
Different isolation structures are applied to different regions of the semiconductor substrate based on local requirements. The STI structure is used in regions where standard electrical isolation is sufficient, while the DTI structure is specifically implemented in regions prone to light leakage. This local quality approach ensures that complexity is introduced only where necessary, optimizing the balance between reliability improvement and device complexity.
2Device complexity
If a lens layer is integrated directly on the image capture chip, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The lens layer is merged with the image capture chip substrate, forming an integrated structure where the lens portion is directly formed on the chip. This eliminates the need for separate lens modules and their associated alignment and assembly processes, thereby reducing overall device complexity. The merging approach consolidates multiple components into a single integrated unit, simplifying the device architecture.
Solution Approach 2:
The lens layer is formed during the substrate processing stage, before the chip is finalized and packaged. By performing the lens formation action preliminarily during substrate fabrication, the patent eliminates subsequent complex alignment and assembly steps that would be required if lenses were added after chip completion. This preliminary action approach embeds the lens formation into the existing manufacturing flow, managing precision requirements through process integration.
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 approach improves electrical isolation and reduces light leakage, leading to enhanced image sensor performance. The integration of a chip-scale lens simplifies the manufacturing process, reduces costs, and results in a more compact image sensor design.
Implementation Method 1
a pattern density of the patterned mask layer varies from a central region of the patterned mask layer to a periphery region of the patterned mask layer... The material layer is polished by using the patterned mask layer as a mask to form a lens layer including a single lens portion
Data Source
AI summary
A method includes at least the following steps. A material layer is formed over an image capture chip. A patterned mask layer is formed on the material layer, wherein a pattern density of the patterned mask layer varies from a central region of the patterned mask layer to a periphery region of the patterned mask layer. The material layer is polished by using the patterned mask layer as a mask to form a lens layer including a single lens portion on the image capture chip.