TFT Electrode Etch Stop Layer Protects a-Si Active Layer
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Solution Overview
Problem
In the manufacturing of thin film transistor liquid crystal display (TFT-LCD) array substrates, the etching of a metal barrier layer can destroy the semiconductor layer, leading to adverse effects on image quality due to the use of HF-containing etchants, which etch the amorphous silicon (a-Si) active layer.
Innovation Solution
A multi-layered structure comprising a metal layer and a metal barrier layer is used for the source and drain electrodes, with an etch stop layer protecting the a-Si active layer, and a similar structure for the gate electrode, preventing semiconductor characteristics from being affected by HF-containing etchants during the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal barrier layer is provided to prevent Cu diffusion, then Cu atom diffusion into insulation layer is prevented, but the semiconductor layer is destroyed by etchant during metal barrier layer etching
Solution Approach 1:
An etch stop layer is introduced as an intermediary protective layer between the a-Si active layer and the metal barrier layer. This etch stop layer specifically resists HF-containing etchants, allowing the metal barrier layer to be etched while protecting the underlying semiconductor layer from damage. The etch stop layer acts as a mediator that enables the etching process to proceed without transferring harmful effects to the semiconductor layer.
Solution Approach 2:
The protective structure is segmented into multiple functional layers: the metal barrier layer for preventing Cu diffusion, the etch stop layer for protecting against etchant damage, and the a-Si active layer for semiconductor functionality. This segmentation allows each layer to perform its specific function independently, with the etch stop layer specifically addressing the etchant protection need without interfering with the metal barrier layer's diffusion prevention capability.
2Ease of manufacture
If HF-containing etchant is used to etch metal barrier layer, then metal barrier layer is effectively etched, but a-Si active layer is also etched and damaged
Solution Approach 1:
The etch stop layer serves as a selective intermediary that is resistant to HF-containing etchants. This allows the etching process to effectively remove the metal barrier layer while the etch stop layer blocks the etchant from reaching and damaging the a-Si active layer, thus maintaining manufacturing precision during the etching process.
Solution Approach 2:
The HF-containing etchant, which would normally be harmful to the a-Si active layer, is converted into a beneficial tool for etching the metal barrier layer. The etch stop layer enables this by being selectively resistant to HF, allowing the harmful etchant to perform its useful function of etching the metal barrier layer without causing damage to the semiconductor layer.
Data Source
AI summary
The present disclosure provides a TFT, an array substrate, their manufacturing methods, and a display device. A source electrode and a drain electrode of the TFT are each of a multi-layered structure including a metal layer and a metal barrier layer. An a-Si active layer of the TFT is covered with an etch stop layer, via-holes penetrating through the etch stop layer are provided at positions corresponding to the source electrode and the drain, and the source electrode and the drain electrode are connected to the a-Si active layer through the via-holes.