Double-Layer Etch Stop Layer for Thin Film Transistors
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Solution Overview
Problem
The traditional oxide thin film transistor manufacturing process faces challenges in maintaining low hydrogen content in the silicon oxide etch stop layer, which affects the stability and deposition rate of the thin film, due to the reaction between hydrogen ions and metal oxides in the active layer.
Innovation Solution
A double-layered etch stop layer structure is implemented, with a bottom layer having a lower hydrogen content and a top layer with a higher hydrogen content, allowing for different process conditions to optimize deposition rates and minimize hydrogen ion interaction with the active layer, using varying deposition temperatures and silane gas flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the deposition temperature is lowered to about 200°C to maintain low hydrogen content in the silicon oxide thin film, then the hydrogen content is reduced, but the deposition rate decreases and thin film stability deteriorates
Solution Approach 1:
The etch stop layer is divided into a multi-layer structure consisting of a first etch stop layer (in contact with the active layer) and a second etch stop layer (disposed on the first etch stop layer). This segmentation allows each layer to have different hydrogen content characteristics, with the first layer maintaining low hydrogen content to protect the active layer and the second layer having higher hydrogen content to enable faster deposition rates.
Solution Approach 2:
Different regions of the etch stop layer structure are assigned different hydrogen content levels. The first etch stop layer near the active layer interface maintains low hydrogen content (≤6%) to prevent damage to the oxide semiconductor, while the second etch stop layer has higher hydrogen content, allowing for improved deposition rates without compromising the interface quality.
2Productivity
If the PECVD method is used to deposit the silicon oxide thin film, then the deposition rate is improved, but hydrogen ions react with metal oxides in the active layer affecting IGZO thin film characteristics
Solution Approach 1:
The etch stop layer is segmented into multiple layers where the first etch stop layer serves as a protective barrier between the PECVD deposition process and the active layer. This segmentation enables the use of PECVD method (with higher deposition rate) for the second layer while the first layer maintains low hydrogen content to protect the active layer from harmful hydrogen ion reactions.
Solution Approach 2:
The first etch stop layer acts as an intermediary layer between the PECVD deposition process and the oxide semiconductor active layer. It mediates the hydrogen content issue by maintaining low hydrogen content itself while allowing the second layer to be deposited at higher rates using PECVD, thus protecting the active layer from direct exposure to hydrogen-rich deposition conditions.
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 approach effectively reduces hydrogen content in the etch stop layer, maintaining the oxide thin film's properties and improving deposition rates while preventing adverse reactions with the active layer, resulting in enhanced stability and performance.
Implementation Method 1
the plasma enhanced chemical vapor deposition (PECVD) method is usually adopted to deposit the silicon oxide thin film
Implementation Method 2
the hydrogen ions generated by silane decomposition are prone to react with In, Zn, O in the metal oxides (e.g., IGZO) in the active layer
Data Source
AI summary
The technical disclosure relates to a thin film transistor and a manufacturing method thereof, an array substrate and a display device. The thin film transistor comprises a base substrate, a gate electrode, an active layer, source/drain electrodes, a pixel electrode and one or more insulating layers, wherein at least one of the insulating layers comprises a bottom insulating sub-layer and a top insulating sub-layer, the top insulating sub-layer having a hydrogen content higher than that of the bottom insulating sub-layer.