Polysilicon Layer Inspection Using Pulsed UV Laser
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Solution Overview
Problem
Conventional methods for inspecting the crystallinity of polysilicon layers often require high-intensity excitation light, which can damage the thin-film polysilicon layer and make it difficult to distinguish between signals from the polysilicon layer and the substrate.
Innovation Solution
A method using a pulsed UV laser beam with specific power and wavelength ranges (1 to 10 W/cm2 average power, 100 to 1000 W/cm2 peak power, and 300 to 400 nm wavelength) to generate a photoluminescence signal, minimizing thermal damage and enhancing signal efficiency by saturating carrier traps and increasing light absorption in the polysilicon layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-intensity excitation light is used to detect photoluminescence signals from polysilicon layers, then detection sensitivity is improved, but thermal damage to the thin-film polysilicon layer occurs
Solution Approach 1:
The patent applies pulsed excitation light instead of continuous high-intensity light. By using periodic pulses with specific duration and interval, the system achieves sufficient signal generation during the pulse while allowing heat dissipation between pulses, thereby avoiding thermal accumulation and damage to the thin-film polysilicon layer.
Solution Approach 2:
The patent optimizes multiple parameters including excitation light wavelength (300-400 nm), pulse duration (1-100 ns), pulse frequency (1-100 kHz), and average power density (1-10 W/cm²). By carefully adjusting these parameters, the system achieves efficient photoluminescence signal generation while keeping thermal damage below detectable levels.
2Measurement precision
If high-intensity excitation light is used to enhance signal generation, then measurement accuracy is improved, but the thin-film polysilicon layer is damaged
Solution Approach 1:
The pulsed excitation approach allows the system to deliver high peak power during brief intervals for accurate measurement, while the off-periods allow thermal relaxation. This periodic action maintains layer integrity by preventing continuous thermal accumulation that would occur with sustained high-intensity illumination.
Solution Approach 2:
The patent maintains continuous measurement capability through rapid pulsing (1-100 kHz), where the useful photoluminescence signal generation occurs continuously across many pulses. This continuous measurement approach ensures reliable data acquisition while the pulsed nature prevents thermal damage.
3Difficulty of detecting and measuring
If conventional excitation methods are used to inspect polysilicon layers, then defect detection is enabled, but the inspection process causes thermal deformation of the substrate
Solution Approach 1:
By using pulsed excitation with low average power density (1-10 W/cm²), the system generates sufficient photoluminescence signals for defect detection while the intermittent nature of the pulses allows heat to dissipate before accumulating to levels that would cause substrate thermal deformation.
Solution Approach 2:
The patent selects specific parameter ranges including wavelength (300-400 nm), pulse duration (1-100 ns), and frequency (1-100 kHz) that optimize signal generation while minimizing thermal effects on the substrate, enabling defect detection without thermal deformation.
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 allows for efficient detection of photoluminescence signals from polysilicon layers without causing thermal damage, enabling effective inspection of crystallinity and defect detection without damaging the thin-film polysilicon layer.
Implementation Method 1
radiating excitation light onto the polysilicon layer, and detecting a photoluminescence signal generated by the excitation light
Implementation Method 2
increasing light absorption in the polysilicon layer
Data Source
AI summary
A method for inspecting a polysilicon layer includes: radiating excitation light to the polysilicon layer; and detecting a photoluminescence signal generated by the excitation light, wherein average power of the excitation light has a range of 1 W/cm2 to 10 W/cm2, and peak power of the excitation light has a range of 100 W/cm2 to 1000 W/cm2.