Thin-Film Transistor Channel Etching to Remove Metal Oxides
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Solution Overview
Problem
The production of thin film transistors in LCDs is hindered by the formation of metal oxides during etching, which leads to poor display performance due to residual metal oxides affecting subsequent etching processes and increasing contact resistance.
Innovation Solution
A method involving sequential wet and dry etching using specific etching solutions, including acidic and alkaline solutions with nitric acid, acetic acid, and sodium hydroxide, to remove metal oxides and ensure proper etching of the channel region, thereby preventing residual metal or metal oxide interference and improving etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxidizing etching gas is used in dry etching, then etching speed is improved, but metal oxides are formed on the metal layer surface causing poor subsequent etching
Solution Approach 1:
The etching process is divided into multiple sequential steps: first wet etching to remove metal layer, then dry etching with oxidizing gas for active layer and ohmic contact layer, followed by selective removal of metal oxides. This segmentation allows each step to optimize for its specific function without compromising overall quality.
Solution Approach 2:
The metal oxides formed during dry etching are not treated as defects to be avoided, but as temporary features to be selectively removed later. The process converts the harmful oxide formation into a beneficial intermediate state that enables precise pattern transfer while maintaining etching speed.
2Ease of manufacture
If conventional etching process is used, then manufacturing simplicity is maintained, but residual metal oxides increase contact resistance and reduce display performance
Solution Approach 1:
The wet etching step is performed preliminarily to remove the metal layer before dry etching. This preliminary action prevents metal oxides from forming on the metal layer surface during subsequent steps, ensuring low contact resistance while maintaining process simplicity.
Solution Approach 2:
The photoresist thin layer serves as an intermediary that enables selective etching. It protects certain areas during wet etching while allowing controlled exposure during dry etching, achieving both process simplicity and high reliability through precise material mediation.
3Ease of manufacture
If photoresist layer thickness is uniform, then manufacturing simplicity is maintained, but precise etching control in channel region is insufficient
Solution Approach 1:
The photoresist layer is designed with non-uniform thickness: thicker in source/drain regions and thinner in the channel region. This local quality variation enables precise etching control where the thin channel region etches faster to create the desired groove profile, while maintaining relatively simple photoresist application procedures.
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 removes metal oxides and ensures accurate etching, enhancing display performance, increasing yield, and is suitable for large-scale production without requiring additional photomask procedures.
Implementation Method 1
a first wet etching, in which a metal layer corresponding to the photoresist layer of the preset pattern is obtained by etching
Implementation Method 2
an alkaline etching solution containing sodium hydroxide is used for etching to remove the metal oxides produced after etching with the acidic etching solution
Implementation Method 3
a first dry etching, in which an oxidizing etching gas is used for etching
Implementation Method 4
a second dry etching, in which the ohmic contact layer is etched to hollow out the portion of the ohmic contact layer corresponding to the channel region
Implementation Method 5
using a half-tone mask to form a preset pattern on the photoresist layer
Data Source
AI summary
A method of manufacturing a thin film transistor and a display device are disclosed. The method includes: forming a gate metal layer, a gate insulating layer, an active layer, an ohmic contact layer sequentially on a substrate; producing a photoresist layer on the metal layer where the portion of the photoresist layer at the channel region has a smaller thickness than other portions; a first wet etching in which the metal layer corresponding to the photoresist layer is obtained; a first drying etching in which the active layer and ohmic contact layer corresponding to the photoresist layer are Obtained; a second wet etching in which the portion of the metal layer corresponding to the channel region removed; and a second dry etching in which the portion of the active layer corresponding to the channel region is made to have a smaller thickness than other portions of the active layer.