Laterally Crystallized Semiconductor Islands for TFT Uniformity

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Solution Overview

Problem

Existing techniques for crystallizing semiconductor films, such as excimer laser annealing and sequential lateral solidification, often result in microstructural non-uniformities and correlations between adjacent thin film transistors (TFTs), leading to performance inconsistencies and noticeable non-uniformities in display devices like LCDs and OLEDs.

Innovation Solution

The method involves patterning amorphous or polycrystalline silicon films into disconnected islands and applying line scan sequential lateral solidification, ensuring each island crystallizes independently, with unique crystallographic orientations and defect structures, thereby reducing correlations and enhancing uniformity across TFTs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If excimer laser annealing or sequential lateral solidification is used to crystallize semiconductor films, then crystalline structure is achieved, but microstructural non-uniformities and correlations between adjacent TFTs occur

Engineering Contradiction:

Improveperformance consistency of TFTsVSAvoidmicrostructural uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The semiconductor film is divided into spatially separated islands that are physically disconnected from each other. Each island crystallizes independently during laser processing, preventing the formation of correlated grain structures between adjacent TFTs. This segmentation eliminates microstructural non-uniformities that propagate across the film, resulting in consistent performance across all TFTs while maintaining reliable crystalline structure within each island.

Inventive Principle:

Principle #1Segmentation

2Area of stationary object

If continuous laser beam scanning is used to irradiate the entire semiconductor thin film, then complete coverage is achieved, but pulse to pulse energy density fluctuations and non-uniform beam intensity profiles cause microstructural non-uniformities

Engineering Contradiction:

Improvecoverage area of semiconductor filmVSAvoidmicrostructural uniformity

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The semiconductor film is patterned into discrete islands before laser irradiation. This segmentation allows the laser beam to process each island independently, eliminating the propagation of energy density fluctuations and beam intensity non-uniformities that occur during continuous scanning of a continuous film. The complete coverage of all islands is maintained while microstructural uniformity is improved through isolated processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The semiconductor film is pre-patterned into islands before laser crystallization. This preliminary action creates physical boundaries that prevent the propagation of laser-induced microstructural non-uniformities between adjacent regions. The islands are then irradiated with the laser beam, achieving complete coverage while maintaining microstructural uniformity within each isolated region.

Inventive Principle:

Principle #10Preliminary action

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 results in a more uniform distribution of defects and improved performance consistency across TFTs, reducing macroscopic non-uniformities and enhancing the quality of display devices by ensuring each TFT has a random and independent defect structure.

Implementation Method 1

a region of the film is irradiated by an excimer laser to partially melt the film

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

which subsequently crystallizes

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Implementation Method 3

sequential lateral solidification ('SLS') processes

Methodology Applied

Scientific EffectSequential lateral solidification: Freezing

Data Source

PatentUS9012309B2Collections of laterally crystallized semiconductor islands for use in thin film transistors

Publication Date: 2015.04.21 THE TRUSTEES OF COLUMBIA UNIV IN THE CITY OF NEW YORK

AI summary

Collections of laterally crystallized semiconductor islands for use in thin film transistors and systems and methods for making same are described. A display device includes a plurality of thin film transistors (TFTs) on a substrate, such that the TFTs are spaced apart from each other and each include a channel region that has a crystalline microstructure and a direction along which a channel current flows. The channel region of each of the TFTs contains a crystallographic grain that spans the length of that channel region along its channel direction. Each crystallographic grain in the channel region of each of the TFTs is physically disconnected from and crystallographically uncorrelated with each crystallographic grain in the channel region of each adjacent TFT.