Multilayer Pixel Electrode Structure for Low-Noise Imaging
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Solution Overview
Problem
The fluctuation in electric charge due to parasitic resistance in the pixel electrode of imaging devices leads to noise, degrading image quality, and this is exacerbated by tensile stress and crystal defects caused during thermal treatment.
Innovation Solution
The imaging device incorporates a pixel electrode with a multilayer structure, where the first layer has a protrusion on its surface and the second layer covers it, mitigating tensile stress and reducing crystal defects, and includes a Ti layer for heat diffusion prevention and a TiN layer for efficient charge extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel electrode structure is used, then the device is simple to manufacture, but parasitic resistance increases leading to noise and degraded image quality
Solution Approach 1:
The pixel electrode is divided into multiple layers (first layer and second layer) with different materials and functions. The first layer provides mechanical support and stress management, while the second layer optimizes electrical conductivity and charge extraction, thereby reducing parasitic resistance without excessive complexity
Solution Approach 2:
The pixel electrode uses composite material structure combining different materials in the first and second layers. This composite approach allows optimization of both mechanical properties (stress management) and electrical properties (conductivity and charge extraction), resolving the contradiction between reliability and complexity
2Stability of the object's composition
If thermal treatment is applied during manufacturing, then the device structure is stabilized, but tensile stress and crystal defects increase leading to higher parasitic resistance
Solution Approach 1:
The first layer of the pixel electrode is designed with specific local properties to manage stress distribution. By controlling the thickness, material composition, and structural characteristics of the first layer, tensile stress during thermal treatment is localized and managed, preventing crystal defects while maintaining overall structural stability
Solution Approach 2:
The multi-layer structure is designed in advance to cushion against thermal stress effects. The first layer acts as a buffer that absorbs and distributes tensile stress before it can cause crystal defects in the second layer, thereby preventing parasitic resistance increase before it occurs
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 configuration suppresses parasitic resistance and crystal defects, enhancing image quality by reducing noise and improving charge extraction efficiency.
Implementation Method 1
a photoelectric conversion layer, a counter electrode provided above the photoelectric conversion layer
Data Source
AI summary
An imaging device includes a photoelectric conversion layer, a counter electrode provided above the photoelectric conversion layer, a pixel electrode that faces the counter electrode with the photoelectric conversion layer disposed between the counter electrode and the pixel electrode, and a contact plug covered with the pixel electrode and connected to the pixel electrode. The pixel electrode includes a first layer and a second layer provided on the first layer in contact with the first layer. A surface of the first layer that is in contact with the second layer has a protrusion that protrudes upward.