Thin Film Transistor Gate Insulator Fluorine Diffusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional thin film transistors using oxide semiconductors in the channel region have field effect mobilities limited to 20 cm2/Vs, which are insufficient for large display devices and next-generation display formats requiring higher pixel density and lower power consumption.
Innovation Solution
Incorporating fluorine in the gate insulating film and optimizing the channel region's width-to-length ratio (W/L) to less than 8, along with using fluorinated silicon nitride as the gate insulating film and In-Ga-Zn-O, In-Sn-Zn-O, or In-W-Zn-O amorphous oxide semiconductors, to enhance field effect mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional TFT using oxide semiconductor is used, then the field effect mobility is limited to 20 cm2/Vs, but this is insufficient for large display devices requiring higher pixel density and lower power consumption
Solution Approach 1:
The patent applies parameter changes by incorporating fluorine into the gate insulating film and optimizing the W/L ratio of the channel region. These parameter modifications to the transistor structure enable the field effect mobility to exceed 20 cm2/Vs, resolving the contradiction between achieving high reliability through improved mobility and meeting the productivity requirements for high pixel density in large display devices.
2Area of stationary object
If the display device size is increased to 40-50 inches, then the coverage area is improved, but the field effect mobility of 10-20 cm2/Vs becomes insufficient
Solution Approach 1:
The patent modifies key parameters of the TFT structure, specifically incorporating fluorine in the gate insulating film and optimizing the channel region's W/L ratio. These parameter changes enable the device to achieve field effect mobility greater than 20 cm2/Vs, which is necessary for maintaining reliability in large 40-50 inch display screens where conventional transistors with 10-20 cm2/Vs mobility are insufficient.
3Speed
If a TFT with field effect mobility greater than 20 cm2/Vs is required for Super Hi-Vision, then the operation speed must be improved, but conventional TFTs cannot achieve this threshold
Solution Approach 1:
The patent achieves the required operation speed by implementing parameter changes in the TFT structure. By incorporating fluorine into the gate insulating film and optimizing the W/L ratio, the field effect mobility exceeds 20 cm2/Vs, which directly enables the high operation speed necessary for Super Hi-Vision and next-generation display formats.
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 approach significantly improves field effect mobility to greater than 20 cm2/Vs, achieving high operation speed and reliability for large display devices, with the potential for field effect mobilities exceeding 50 cm2/Vs when the W/L ratio is 0.8 or less, suitable for large screen display applications.
Implementation Method 1
when fluorine contained in the gate insulating film diffuses and moves toward the oxide semiconductor film, fluorine is bonded to and terminates a dangling bond that is present at an interface between the oxide semiconductor film and the gate insulating film
Implementation Method 2
since it is possible to form an active layer by a sputtering method, an oxide semiconductor can be more easily formed than LTPS (low temperature poly-silicon crystal) or amorphous silicon
Data Source
AI summary
A thin film transistor having a high operation speed with a field effect mobility greater than 20 cm2/Vs and a method for manufacturing the same, and a semiconductor device having the same are provided. A thin film transistor in which a gate electrode, a gate insulating film and an oxide semiconductor film are laminated on a substrate, a source region and a drain region are respectively formed in outer portions of the oxide semiconductor film in the width direction, and a channel region is formed in a region between the source region and the drain region; and a source electrode is connected to the source region, while a drain electrode is connected to the drain region. The gate insulating film contains fluorine; and the ratio of the width W of the channel region to the length L thereof, namely W/L is less than 8.