Silicon Island Elevation Measurement via Laser Dot Tracking
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Solution Overview
Problem
Existing methods for measuring and monitoring the elevation and shape of a silicon island during the silicon meltdown process are inaccurate and prone to errors due to reflection or scattering signals from furnace components, failing to provide continuous and reliable data necessary for optimal crystal growth.
Innovation Solution
A system using a focused bright light source, such as a green or blue laser, projects a bright dot onto the silicon island, and a camera system with detection and tracking software continuously calculates the elevation and shape based on image patterns, avoiding interference with the crystal growth process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser range finder is used to measure silicon island elevation, then measurement capability is provided, but reflection or scattering signals from furnace windows and heat shield cause significant errors
Solution Approach 1:
The patent introduces an intermediary substance (silicon vapor or smoke) between the measurement beam and the silicon island surface. This intermediary scatters the measurement beam to create a visible indication that can be detected by sensors, while preventing direct interaction between the beam and furnace components that would cause erroneous reflections. The intermediary acts as a mediator that enables measurement without the harmful direct path.
Solution Approach 2:
The patent converts the harmful effect of beam scattering (which causes measurement errors) into a beneficial effect by deliberately introducing controlled silicon vapor or smoke that scatters the beam in a predictable and useful manner. The scattering that would normally be harmful is transformed into a useful mechanism for creating visible indicators and enabling accurate elevation measurement through the scattered light pattern.
2Ease of operation
If conventional light sources are used to monitor silicon island, then monitoring capability is provided, but accuracy is insufficient to satisfy control needs
Solution Approach 1:
The patent changes the parameters of the light source by using a laser instead of conventional light sources. The laser provides coherent, monochromatic, and highly directional light with specific wavelength characteristics that enable precise measurement. This parameter change in the light source properties transforms the monitoring system from inadequate conventional lighting to a precision measurement tool capable of satisfying control requirements.
Solution Approach 2:
The patent applies local quality by concentrating the light energy into a focused beam that interacts specifically with the silicon island surface and the introduced vapor/smoke. Rather than using diffuse conventional lighting, the laser beam provides localized, intense illumination at specific measurement points, creating high-contrast visible indicators that enable precise local measurement of elevation and shape changes.
3Productivity
If the silicon island elevation is constantly changing and shape has complex variations, then continuous monitoring is needed, but measurement becomes difficult
Solution Approach 1:
The patent applies preliminary action by introducing the silicon vapor or smoke into the measurement path before the actual elevation measurement is performed. This preliminary introduction of the scattering medium ensures that when the laser beam passes through, the vapor is already in position to create visible indicators on the silicon island surface, enabling immediate and continuous tracking of dynamic shape changes without measurement delay or difficulty.
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 method provides accurate and continuous monitoring of the silicon island's elevation and shape, enhancing the control and quality of the crystal growth process by minimizing errors and ensuring optimal meltdown conditions.
Implementation Method 1
projecting a focused bright light on the silicon island to produce a bright dot on the silicon island
Implementation Method 2
an elevation and a shape of the silicon island are electronically determining by tracking the bright dot during the meltdown process
Data Source
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AI summary
A method of continuously measuring an elevation and shape of an unmelted polycrystalline silicon island during a silicon meltdown process. The method comprises projecting a focused bright light on the silicon island to produce a bright dot on the silicon island. The method also includes electronically determining an elevation and a shape of the silicon island by tracking the bright dot during the meltdown process.