Coplanar Etch Stop Layer for Image Sensor Planarization
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Solution Overview
Problem
Current image sensors, particularly CMOS image sensors, face challenges in manufacturing efficiency and productivity due to the complexity of forming transparent electrodes in trench structures, which can result in process steps that increase costs and reduce productivity.
Innovation Solution
The implementation of a substrate with a sensor region and a pad region, featuring a lower transparent electrode and an etch stop layer, where the upper surface of the transparent electrode is coplanar with the etch stop layer, simplifies the planarization process and reduces the step between the sensor and pad regions, thereby enhancing manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transparent electrodes are formed in trench structures, then the image sensor can achieve proper electrical isolation and functionality, but the manufacturing process complexity increases and productivity decreases
Solution Approach 1:
The patent applies preliminary action by forming the etch stop layer on the insulation layer before forming the transparent electrodes in the trenches. This pre-positioned etch stop layer serves as a reference structure that guides subsequent processing steps, enabling more efficient formation of the transparent electrodes while maintaining proper electrical isolation. The etch stop layer is prepared in advance to facilitate the trench formation and electrode deposition processes.
2Reliability
If complex process steps are used to form transparent electrodes in trenches, then proper electrical isolation is achieved, but manufacturing costs increase
Solution Approach 1:
The etch stop layer serves multiple functions simultaneously: it provides electrical isolation between adjacent pixel regions, acts as a reference structure for trench formation, and enables cost-effective manufacturing by simplifying subsequent processing steps. This multi-functional design eliminates the need for separate structures dedicated to each function, thereby reducing overall manufacturing complexity and cost.
3Productivity
If the upper surface of the transparent electrode is coplanar with the etch stop layer, then the planarization process is simplified and productivity increases, but the structural complexity must be precisely controlled
Solution Approach 1:
The etch stop layer acts as an intermediary reference structure that mediates between the insulation layer and the transparent electrodes. By positioning the etch stop layer at a specific height on the insulation layer, it provides a stable reference plane that simplifies the formation of coplanar transparent electrodes. This intermediary structure makes it easier to control the coplanarity of the upper surfaces without requiring complex precision control mechanisms.
Data Source
AI summary
An image sensor includes a sensor region for receiving light and generating an image data and a pad region adjacent to the sensor region, an insulation layer on the substrate, and a lower transparent electrode on the insulation layer in the sensor region, and an etch stop layer on the insulation layer in the sensor region and pad region. The etch stop layer may include silicon nitride. A height of an uppermost surface of the lower transparent electrode may be substantially equal to a height of an upper surface of the etch stop layer, with respect to the substrate.