TFT Gate Insulating Film Segmentation for Trap Removal
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Solution Overview
Problem
Conventional techniques for manufacturing thin-film transistors (TFTs) on glass substrates face challenges in stabilizing TFT characteristics due to damage and contamination of the gate insulating film, leading to inadequate reliability and durability, particularly with the introduction of impurity ions and hydrogen plasma treatment.
Innovation Solution
A semiconductor device and manufacturing method involving a substrate with a semiconductor layer, a gate insulating film, and a gate electrode, where an electrode-protecting insulating film is formed and its surface layer is etched to remove carrier traps, maintaining a specific film thickness ratio and metal concentration to stabilize TFT characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impurity ions are implanted into the semiconductor layer using the gate electrode as mask to form LDD region, then the TFT durability and reliability are improved, but the gate insulating film is damaged and carrier traps are formed reducing TFT reliability
Solution Approach 1:
The gate insulating film is divided into two regions: a first region under the gate electrode that retains full thickness to prevent carrier trap formation, and a second region outside the gate electrode area that is thinned to remove damaged portions from ion implantation. This segmentation allows the LDD region to be formed while preserving the integrity of the gate insulating film in the critical area.
Solution Approach 2:
Different thicknesses of the gate insulating film are applied to different locations: the first region under the gate electrode maintains the original thickness to ensure reliability, while the second region outside the gate electrode area is thinned to remove damaged portions. This local differentiation resolves the contradiction by protecting where needed while allowing necessary processing elsewhere.
2Reliability
If the gate insulating film is left on the entire surface without patterning to maintain insulating properties, then the insulating properties between semiconductor layer and upper layers are maintained, but the gate insulating film is damaged by ion implantation in protruding portions
Solution Approach 1:
The gate insulating film structure is made non-uniform with a first region under the gate electrode maintaining full thickness for insulating properties and a second region outside the gate electrode area being thinned to remove damaged portions. This local quality differentiation maintains insulation where required while eliminating damage elsewhere.
Solution Approach 2:
The gate insulating film is segmented into functional zones: a protected first region that maintains insulating properties and a processed second region where damaged portions are removed. This segmentation resolves the contradiction between maintaining insulation and avoiding ion implantation damage.
3Reliability
If hydrogen plasma treatment is performed on the semiconductor layer, then the semiconductor layer characteristics are improved, but the gate insulating film is damaged and carrier traps are formed
Solution Approach 1:
By segmenting the gate insulating film into a protected first region and a processed second region, the invention enables hydrogen plasma treatment to be performed on the semiconductor layer without damaging the critical gate insulating film area, thus improving semiconductor characteristics while preventing carrier trap formation.
4Object-affected harmful factors
If the portion of gate insulating film protruding from gate electrode area is removed partway in film thickness direction, then the damaged portion from ion implantation is removed, but the TFT characteristics cannot be adequately stabilized
Solution Approach 1:
The invention segments the gate insulating film into a first region under the gate electrode that retains full thickness and a second region outside the gate electrode area that is thinned. This segmentation ensures both removal of damaged portions and adequate stabilization of TFT characteristics by preserving the critical insulating structure under the gate electrode.
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
The method effectively removes carrier traps and stabilizes TFT characteristics, enhancing reliability and durability by maintaining the film thickness ratio and metal concentration within specific limits, thereby reducing threshold voltage fluctuations under bias stress.
Implementation Method 1
the surface layer portion of the electrode-protecting insulating film is etched away after the electrode-protecting insulating film is formed
Implementation Method 2
impurity ions are implanted into a semiconductor layer over a gate insulating film using the gate electrode as the mask
Implementation Method 3
the gate insulating film is usually formed by plasma CVD (Chemical Vapor Deposition) or sputtering
Implementation Method 4
the gate insulating film is usually formed by plasma CVD (Chemical Vapor Deposition) or sputtering
Implementation Method 5
A hydrogen plasma treatment is performed on the semiconductor layer as needed
Data Source
AI summary
A base layer is formed on an insulating substrate, and a semiconductor layer is formed in localized fashion thereon. A gate insulating film is then formed so as to cover the semiconductor layer, and a gate electrode is formed on a portion of the gate insulating film. An impurity is then implanted into the semiconductor layer via the gate insulating film, and a source region, a drain region, and an LDD region are formed. The gate insulating film is etched with dilute hydrofluoric acid. An electrode-protecting insulating film is then formed so as to cover the gate electrode, and the entire surface of the surface layer portion of the electrode-protecting insulating film is etched away using dilute hydrofluoric acid. Carrier traps introduced into the electrode-protecting insulating film and the gate insulating film are thereby removed.