Excimer Laser Energy Controller for Silicon Crystallization

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Solution Overview

Problem

Existing methods for crystallizing silicon layers in flat panel displays using excimer-laser pulses face challenges in maintaining uniformity and stability of energy dosage, leading to variations in crystalline microstructure and manufacturing yield.

Innovation Solution

The use of a high-pass digital filter to control pulse-energy fluctuations in excimer-laser pulses, ensuring that only fluctuations above a certain frequency are minimized, while maintaining the average pulse energy at a set level, results in improved uniformity of energy dosage across the silicon layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional excimer-laser pulsing is used for silicon crystallization, then the crystallization process can be performed, but pulse-energy fluctuations cause variations in energy dosage and crystalline microstructure uniformity

Engineering Contradiction:

Improveuniformity of crystalline microstructureVSAvoidstability of pulse energy

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The system employs a feedback control mechanism where a photodetector monitors the pulse energy of each laser pulse in real-time. The measured pulse energy is fed back to a control circuit that adjusts the discharge timing and duration of the excimer laser to compensate for energy deviations, thereby stabilizing the pulse energy and ensuring uniform crystalline microstructure throughout the silicon layer

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces mechanical adjustment mechanisms with an electronic control system. Instead of physically adjusting laser parameters, the system uses electronic signals to control the discharge timing and duration of the excimer laser based on real-time pulse energy measurements, achieving precise energy stabilization without mechanical intervention

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If the pulse-repetition frequency is increased to improve productivity, then more pulses can be delivered, but pulse-to-pulse energy variations become more significant

Engineering Contradiction:

Improvecrystallization processing speedVSAvoiduniformity of energy dosage

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The real-time feedback control system continuously monitors each pulse's energy and immediately adjusts subsequent pulses to compensate for variations. This allows the system to operate at higher pulse-repetition frequencies while maintaining uniform energy dosage, as each pulse is independently controlled based on previous pulse measurements

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control system performs preliminary adjustment of each pulse's discharge timing and duration based on the measured energy of the previous pulse. This proactive compensation ensures that energy variations are corrected before they affect the crystallization uniformity, enabling higher processing speeds without sacrificing precision

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 significantly reduces energy-dose variations along the substrate, enhancing the uniformity of the crystalline silicon layer and improving manufacturing yield by averaging pulse-to-pulse instabilities through spatial overlapping of pulses.

Implementation Method 1

a pulsed beam of laser-radiation that is shaped into the form of a long line... A favored source of the pulsed laser-radiation is an excimer laser, which delivers laser-radiation having a wavelength in the ultraviolet region... The process... is referred to as excimer-laser annealing (ELA)

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

crystallization is performed using a pulsed beam of laser-radiation... A favored source of the pulsed laser-radiation is an excimer laser

Methodology Applied

Scientific EffectLaser: Laser

Implementation Method 3

a thin layer of amorphous silicon (a 'silicon film') on a glass substrate is repeatedly melted by the pulsed laser-radiation... Repeated melting and re-solidification (recrystallization) through exposure to the pulsed laser-radiation

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 4

Repeated melting and re-solidification (recrystallization) through exposure to the pulsed laser-radiation, at a certain optimum energy-density, take place until a desired crystalline microstructure is obtained in the silicon film

Methodology Applied

Scientific EffectCrystallisation: Crystallisation

Data Source

PatentUS10234765B2Energy controller for excimer-laser silicon crystallization

Publication Date: 2019.03.19 COHERENT LASERSYST

AI summary

Excimer laser annealing apparatus includes and excimer laser delivering laser-radiation pulses to a silicon layer supported on a substrate translated with respect to the laser pulses such that the consecutive pulses overlap on the substrate. The energy of each of the laser-radiation pulses is monitored, transmitted to control-electronics, and the energy of a next laser pulse is adjusted by a high-pass digital filter.