Substrate Rotation Speed Control for Vibration Damping
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Solution Overview
Problem
Variations in wafer structure due to differences in thickness and multilayer structures lead to surface vibrations during rotation, causing non-uniform processing results in semiconductor fabrication, especially as wafer diameter increases and natural frequency decreases, resulting in varied processing outcomes even under identical conditions.
Innovation Solution
A substrate processing apparatus that includes a natural frequency calculator to determine the substrate's natural frequency based on specifications like thickness, diameter, and material properties, and a processing controller to adjust the rotational speed to avoid resonance, ensuring uniform processing by controlling the rotational speed and fluid flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same rotational speed is used for all wafers, then processing efficiency is maintained, but processing uniformity deteriorates due to natural frequency variations
Solution Approach 1:
The patent applies parameter changes by adjusting the rotational speed parameter based on the natural frequency characteristics of each wafer. The processing controller modifies the rotational speed to avoid resonance frequencies, thereby preventing violent vibrations while maintaining efficient processing. This dynamic parameter adjustment resolves the contradiction between maintaining high processing efficiency and achieving uniform processing results across wafers with different natural frequencies.
2Area of moving object
If wafer diameter is increased, then processing capacity is improved, but vibration control becomes more difficult due to decreased natural frequency
Solution Approach 1:
The patent implements feedback control by measuring the natural frequency of each wafer and using this information to adjust the rotational speed. The natural frequency measurement unit detects the specific natural frequency of each wafer, and the processing controller uses this feedback to set an appropriate rotational speed that avoids resonance. This feedback mechanism enables effective vibration control for larger wafers with lower natural frequencies, resolving the contradiction between increased processing capacity and maintained vibration stability.
3Speed
If rotational speed is increased to match natural frequency, then processing speed is improved, but vibration amplitude is enlarged causing non-uniform processing
Solution Approach 1:
The patent applies preliminary anti-action by proactively avoiding the harmful resonance condition before it occurs. The system measures the natural frequency of each wafer in advance and deliberately selects a rotational speed that does not match the natural frequency, thereby preventing the amplification of vibrations. This preventive approach resolves the contradiction by ensuring that increased rotational speed does not lead to harmful vibration amplitudes, maintaining both processing speed and uniformity.
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 stabilizes the substrate surface during rotation, preventing violent vibrations and ensuring uniform contact by the cleaning tool, thereby achieving consistent processing results across wafers of varying structures.
Implementation Method 1
a natural frequency calculator configured to determine a natural frequency of the substrate
Implementation Method 2
the natural frequency calculator is configured to emit an acoustic wave toward the substrate while changing a frequency of the acoustic wave, measure an amplitude of the acoustic wave reflected from the substrate, and determine the natural frequency of the substrate from the frequency of the acoustic wave at which the amplitude is maximized
Implementation Method 3
determine the natural frequency of the substrate from the frequency of the acoustic wave at which the amplitude is maximized
Implementation Method 4
the processing controller is configured to control the rotational speed of the substrate such that the substrate is rotated at a rotational speed that is different from a rotational speed corresponding to the natural frequency of the substrate
Data Source
AI summary
A substrate processing apparatus configured to rotate a substrate, such as a wafer, is disclosed. The substrate processing apparatus includes: a substrate holder configured to hold and rotate a substrate; a natural frequency calculator configured to determine a natural frequency of the substrate; and a processing controller configured to control a rotational speed of the substrate based on the natural frequency of the substrate. The processing controller is configured to control the rotational speed of the substrate such that the substrate is rotated at a rotational speed that is different from a rotational speed corresponding to the natural frequency of the substrate.