Polycrystalline Silicon Layer Surface Defect Prevention
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Solution Overview
Problem
The challenge in manufacturing polycrystalline silicon layers for display devices is to achieve excellent device characteristics while minimizing surface defects, particularly circular spots, which affect the performance and reliability of electroluminescent displays.
Innovation Solution
A method involving the formation of a polycrystalline silicon layer by sequentially depositing and doping amorphous silicon layers with N-type and P-type impurities, followed by laser crystallization, with specific doping voltages and concentrations, and thorough cleaning with hydrofluoric acid and deionized water to prevent hydrophobic surface formation and subsequent circular spot generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is cleaned with hydrofluoric acid to remove surface contaminants, then cleaning effectiveness is improved, but the substrate surface becomes hydrophobic leading to circular spot defects
Solution Approach 1:
The patent converts the harmful hydrophobic effect caused by hydrofluoric acid cleaning into a beneficial outcome by subsequently treating the substrate with a phosphoric acid solution. This treatment modifies the hydrophobic surface to become hydrophilic, preventing water droplet formation and circular spot defects during the crystallization process, while preserving the cleaning effectiveness of the hydrofluoric acid step.
2Reliability
If amorphous silicon layers are doped with impurities and then laser crystallized to form polycrystalline silicon, then device characteristics are improved, but surface protrusions and circular spots are generated
Solution Approach 1:
The patent applies preliminary action by treating the substrate with a phosphoric acid solution immediately after hydrofluoric acid cleaning and before the laser crystallization process. This preliminary treatment modifies the surface properties to be hydrophilic, preventing the formation of surface protrusions and circular spots during subsequent crystallization, while preserving the dopant distribution and device characteristics.
3Reliability
If the polycrystalline silicon layer is formed with proper doping to achieve good electrical characteristics, then transistor performance is improved, but hydrophobic surface formation leads to pixel defects
Solution Approach 1:
The patent introduces a phosphoric acid solution treatment as an intermediary step between substrate cleaning and crystallization. This intermediary treatment modifies the surface chemistry to create a hydrophilic state, acting as a mediator that prevents water droplet formation and circular spot defects during crystallization, while not interfering with the dopant distribution and electrical characteristics of the polycrystalline silicon layer.
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 polycrystalline silicon layer with reduced surface protrusions and circular spots, enhancing the device characteristics and reliability of the display devices by maintaining hydrophilicity and preventing pixel defects.
Implementation Method 1
crystalizing the n-doped first amorphous silicon layer and the p-doped second amorphous silicon layer by irradiating a laser beam onto the n-doped first amorphous silicon layer and the p-doped second amorphous silicon layer
Implementation Method 2
cleaning the substrate with hydrofluoric acid
Data Source
AI summary
An embodiment provides a manufacturing method of a polycrystalline silicon layer, including: forming a first amorphous silicon layer on a substrate; doping an N-type impurity into the first amorphous silicon layer; forming a second amorphous silicon layer on the n-doped first amorphous silicon layer; doping a P-type impurity into the second amorphous silicon layer; and crystalizing the n-doped first amorphous silicon layer and the p-doped second amorphous silicon layer by irradiating a laser beam onto n-doped first amorphous silicon layer and the p-doped second amorphous silicon layer to form a polycrystalline silicon layer.