Storage Capacitor Electrode Stack for Reliable Display Panels
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Solution Overview
Problem
Display devices face challenges in achieving improved reliability due to limitations in the structure and materials used in their capacitors, which affect the performance and longevity of the storage capacitor.
Innovation Solution
The display device incorporates a storage capacitor with a specific layered structure, including a semiconductor layer, gate electrode, and capacitor electrodes, where the second capacitor electrode has a lower layer, an intermediate layer, and an upper layer with amorphous conductive oxides, and an intermediate layer between the lower and upper layers, enhancing the reliability by preventing damage during the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional capacitor electrode structure is used, then the manufacturing process is simple, but the reliability of the storage capacitor is insufficient
Solution Approach 1:
The second capacitor electrode is divided into three separate layers (lower layer, intermediate layer, upper layer) instead of using a single conventional electrode structure. This segmentation allows each layer to serve specific functions: the lower and upper layers provide conductivity while the intermediate layer prevents damage during etching, thereby improving reliability without requiring fundamentally new manufacturing processes
Solution Approach 2:
The capacitor electrode structure combines multiple conductive oxide materials with different properties. The lower layer uses IGZO (indium gallium zinc oxide), the intermediate layer uses IZO (indium zinc oxide), and the upper layer uses ZIO (zinc indium oxide). This composite structure leverages the complementary properties of each material to achieve both low sheet resistance and damage prevention during processing
2Reliability
If the second capacitor electrode is made with a single layer, then the manufacturing process is simpler, but the sheet resistance is higher and reliability is reduced
Solution Approach 1:
The capacitor electrode is segmented into three depositable layers that can be formed using standard sputtering processes. Each layer is deposited separately with controlled thickness and composition, allowing optimization of electrical properties while maintaining compatibility with existing manufacturing equipment and processes
Solution Approach 2:
The invention changes the compositional parameters of each layer systematically. The lower layer has higher indium content (IGZO), the intermediate layer has balanced composition (IZO), and the upper layer has higher zinc content (ZIO). These parameter changes enable gradient optimization of electrical conductivity and structural stability without requiring new fabrication techniques
3Reliability
If the intermediate layer is made thicker, then the protection against damage is improved, but the sheet resistance increases
Solution Approach 1:
The intermediate layer thickness is precisely controlled within a specific range (5-50 Å) to achieve the optimal balance between protection and conductivity. This parameter optimization ensures that the layer is thick enough to prevent damage during etching but thin enough to maintain low sheet resistance, demonstrating precise control over film deposition parameters
Data Source
AI summary
A display device includes a transistor including a semiconductor layer and a gate electrode overlapping a channel area of the semiconductor layer and a storage capacitor electrically connected to the transistor, the storage capacitor including a first capacitor electrode disposed below the semiconductor layer, a second capacitor electrode disposed on the first capacitor electrode, and a third capacitor electrode disposed on the second capacitor electrode, the second capacitor electrode includes a lower layer, the lower layer and the semiconductor layer being disposed on a same layer, an intermediate layer disposed on the lower layer, and an upper layer disposed on the intermediate layer, and the upper layer of the second capacitor electrode includes an amorphous conductive oxide.