Oxide Semiconductor TFT with Graded Hydrogen Gate Insulator
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Solution Overview
Problem
Thin film transistors using oxide semiconductor layers face challenges in achieving low resistance for source and drain regions while maintaining high resistance for the channel region, leading to unsatisfactory switching characteristics and off operation stability, especially in inverse-stagger structured TFTs with a bottom gate configuration.
Innovation Solution
The thin film transistor design incorporates a gate insulating film with distinct hydrogen content regions, forming an oxide semiconductor layer with different resistance zones to control the resistance of the channel and source/drain regions, ensuring high resistance for the channel and low resistance for the source/drain contacts, thereby improving switching characteristics and off operation stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If source and drain electrodes are directly connected to oxide semiconductor layer, then structure is simple, but parasitic resistance increases and switching characteristic deteriorates
Solution Approach 1:
The patent applies local quality by creating different hydrogen concentration zones within the oxide semiconductor layer. The source and drain regions are doped with hydrogen to reduce resistance, while the channel region maintains lower hydrogen concentration to preserve high resistance when off, thus achieving local differentiation of electrical properties to resolve the contradiction between simple structure and reliable switching characteristic.
2Speed
If oxide semiconductor layer is used instead of amorphous Si, then mobility increases and high-definition panel is achievable, but resistance control becomes difficult
Solution Approach 1:
The patent applies parameter changes by controlling the hydrogen concentration parameter within the oxide semiconductor layer to achieve the desired resistance characteristics. By adjusting hydrogen content in specific regions during manufacturing, the patent enables resistance control in oxide semiconductor TFTs, making them as manufacturable as amorphous Si TFTs while retaining the high mobility advantage of oxide semiconductors.
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 design achieves satisfactory off characteristics and stable switching performance by maintaining high channel resistance and low contact resistance, enhancing the overall performance of the thin film transistor.
Implementation Method 1
The gate insulating film includes a first insulating region formed on the gate electrode, and a second insulating region that is formed over the insulating substrate without the gate electrode interposed therebetween, and is different in hydrogen content from the first insulating region
Data Source
AI summary
A first oxide semiconductor region serving as a channel region of a TFT is formed on a first insulating region of a gate insulating film whose hydrogen content is comparatively low, and a second oxide semiconductor region that contacts with a source electrode and a drain electrode is formed on a second insulating region of a gate insulating film whose hydrogen content is comparatively high. For this reason, sheet resistance R1 of the first oxide semiconductor region is comparatively high, and sheet resistance R3 of the second oxide semiconductor region is comparatively low so that R1>R3.