Asymmetric Gate Contact for Image Sensor Integration
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Solution Overview
Problem
Existing image sensors face challenges in enhancing electrical properties and integration while maintaining reliability, particularly in the design and fabrication of contacts within the image sensor structure.
Innovation Solution
The image sensor design incorporates a gate contact with a larger lower part and a smaller upper part, where the lower part has a larger contact area with the gate electrode and a smaller contact resistance, and the upper part has a smaller planar area, allowing for improved electrical properties and increased integration by optimizing the contact geometry and materials used.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact area is increased to reduce contact resistance, then electrical properties are improved, but the device area increases reducing integration
Solution Approach 1:
The contact is designed with an asymmetric geometry where the lower part (contacting the gate electrode) has a larger planar area to reduce contact resistance, while the upper part (extending to the wiring line) has a smaller planar area. This asymmetric design allows the contact to simultaneously achieve low contact resistance through the larger lower area and high integration through the smaller upper area that occupies less space on the interlayer dielectric layer.
2Reliability
If the contact area is increased to improve electrical properties, then contact resistance decreases, but the integration density decreases
Solution Approach 1:
The contact employs asymmetric geometry with a larger lower part for reduced contact resistance and a smaller upper part for improved integration density. The lower part contacts the gate electrode with sufficient area to minimize resistance, while the upper part extends minimally to connect to the wiring line, thereby achieving both low contact resistance and high integration in the image sensor device.
3Reliability
If the contact geometry is optimized for electrical properties, then contact resistance is reduced, but the fabrication complexity increases
Solution Approach 1:
The contact geometry is optimized by adjusting the relative sizes of the lower and upper parts, where the lower part has a larger planar area and the upper part has a smaller planar area. This parameter optimization allows the contact to achieve low contact resistance through the larger lower area while maintaining simple fabrication processes using standard photolithography and etching techniques to form the asymmetric shape.
Data Source
AI summary
Disclosed are image sensors and methods of fabricating the same. The image sensor comprises a substrate including a plurality of pixels, a photoelectric conversion region in the substrate at each of the pixels, a gate electrode on the substrate at each of the pixels, an interlayer dielectric layer on the substrate and the gate electrode, and a contact penetrating the interlayer dielectric layer and on the gate electrode. The contact includes a lower part on the gate electrode and an upper part on the lower part and connected to a wiring line on the interlayer dielectric layer. A planar shape of the lower part of the contact is larger than that of the upper part of the contact.