Integrated N-P Thin Film Transistor for Compact CMOS Inverters

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Solution Overview

Problem

Current display devices, such as LCD and OLED, face limitations in size reduction due to the requirement of both N-type and P-type MOSFETs for CMOS inverters, which complicates the manufacturing process and hinders the development of smaller, more efficient thin film transistors.

Innovation Solution

A thin film transistor design that integrates both N-type and P-type semiconductor layers, formed under the same vacuum conditions within one chamber, with the P-type layer being thinner than the N-type layer, allowing for both N-type and P-type semiconductor properties in a single layer, enabling efficient channel formation and operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If both N-type and P-type MOSFETs are used for CMOS inverters, then the display device can operate properly with appropriate signal outputting, but the device size cannot be reduced and the manufacturing process becomes complicated

Engineering Contradiction:
Improvesignal outputting capabilityVSAvoidmanufacturing process complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines both N-type and P-type semiconductor layers within a single thin film transistor structure. The N-type semiconductor layer and P-type semiconductor layer are formed in different regions of the same active area, allowing one TFT to replace the traditional separate N-type and P-type MOSFETs required for CMOS inverters, thereby simplifying the manufacturing process while maintaining proper signal outputting capability

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The thin film transistor structure is designed to perform multiple functions by integrating both N-type and P-type semiconductor properties in one device. This universal structure can function as both N-type and P-type transistors depending on which semiconductor layer is activated, eliminating the need for separate dedicated N-type and P-type MOSFET fabrication processes

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If both N-type and P-type MOSFETs are used for CMOS inverters, then the display device can operate properly with appropriate signal outputting, but the device size increases

Engineering Contradiction:
Improvesignal outputting capabilityVSAvoiddevice size
Core Design Contradiction:
ReliabilityVSArea of stationary object

Solution Approach 1:

The patent merges the functionality of separate N-type and P-type MOSFETs into a single thin film transistor by stacking the N-type semiconductor layer and P-type semiconductor layer within the same active area. This integration allows the display device to maintain proper signal outputting capability while significantly reducing the overall device size compared to traditional CMOS inverter structures requiring separate transistors

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If the P-type semiconductor layer is made thinner, then the mobility and performance of the P-type layer is improved, but the manufacturing precision requirements increase

Engineering Contradiction:
ImproveP-type layer mobilityVSAvoidlayer thickness control
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The patent optimizes the thickness parameter of the P-type semiconductor layer to be thinner than the N-type semiconductor layer. This parameter change improves the mobility and electrical performance of the P-type layer. The invention addresses the increased manufacturing precision requirements through careful process design and control during the sequential formation of the N-type and P-type semiconductor layers

Inventive Principle:
Principle #35Parameter changes

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 enhances the mobility and reduces the threshold voltage of the P-type semiconductor layer, improving the overall performance and size efficiency of the thin film transistor, allowing for more compact and effective display devices.

Implementation Method 1

both N-type and P-type semiconductor layers, which are formed under the same vacuum condition within one chamber

Methodology Applied
Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentEP3276664B1Thin film transistor device, method for manufacturing the same, and display device including the same
Publication Date: 2020.11.11 LG DISPLAY CO LTD
  • EP3276664B1 patent drawingFigure 1~2
  • EP3276664B1 patent drawingFigure 3~4
  • EP3276664B1 patent drawingFigure 5~6

AI summary

Disclosed is a thin film transistor (10) including both an N-type semiconductor layer (131) and a P-type semiconductor layer (132), a method for manufacturing the same, and a display device (1000) including the same, wherein the thin film transistor (10) may include a first gate electrode (110) on a substrate (100); a first gate insulating film (120) for covering the first gate electrode (110); a semiconductor layer (130) on the first gate insulating film (129); a second gate insulating film (150) covering the semiconductor layer (130); and a second gate electrode (160) on the second gate insulating film (150), wherein the semiconductor layer (130) includes the N-type semiconductor layer (131) and the P-type semiconductor layer (132).