Crystal Oscillator Film Thickness Sensor Exfoliation Correction
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Solution Overview
Problem
Conventional crystal type film thickness meters fail to accurately measure film thickness when exfoliation occurs during thin film formation, leading to defective products due to excessive film thickness.
Innovation Solution
A thin film forming apparatus with a vacuum chamber, a thin film material source, and a crystal oscillator, where the resonance frequency of the crystal oscillator is repeatedly measured to calculate film thickness, and a change value is used to determine the thickness of exfoliated film, allowing for a corrected film thickness value to be calculated and compared to an aimed value for precise termination of film growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a crystal type film thickness meter is used to monitor film thickness during deposition, then the film thickness can be controlled to reach the aimed thickness, but if exfoliation occurs on the crystal oscillator surface, the measurement becomes inaccurate and leads to defective products
Solution Approach 1:
The system continuously monitors the resonance frequency of the crystal oscillator and compares it with the aimed resonance frequency. When exfoliation is detected through frequency deviation, the system provides feedback to adjust the deposition process, ensuring accurate film thickness control despite the exfoliation event
Solution Approach 2:
The crystal oscillator is pre-coated with a first thin film before the main thin film deposition. This preliminary coating layer serves as a stable base that prevents exfoliation during the measurement process, allowing accurate thickness monitoring of the main film layer
2Productivity
If the deposition process is terminated when the measured film thickness reaches the aimed value, then the process efficiency is improved, but if exfoliation has occurred, the actual film thickness exceeds the target and produces defective products
Solution Approach 1:
The system continuously monitors the resonance frequency and compares the calculated film thickness with the aimed thickness. When exfoliation is detected through frequency deviation, the system provides feedback to extend the deposition process beyond the nominal target thickness, ensuring the actual film meets specifications
Solution Approach 2:
By pre-coating the crystal oscillator with a stable first thin film, the system ensures reliable thickness measurement throughout the deposition process, allowing accurate termination control when the main film reaches the target thickness without exfoliation interference
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
Enables accurate film thickness measurement and prevention of defective products by accounting for exfoliation, ensuring the film thickness meets the desired target value.
Implementation Method 1
a crystal oscillator disposed in a position inside the vacuum chamber where the particles of the thin film material are to be attached, and a measuring device for measuring a resonance frequency of the crystal oscillator
Implementation Method 2
a thin film material source, disposed inside the vacuum chamber for emitting particles of a thin film material
Implementation Method 3
When a film is formed on a processing object (such as, glass, wafer, etc.) in a vacuum by an evaporation method
Data Source
AI summary
A technology which is capable of an accurate measurement of the film thickness even if an exfoliation occurs is provided. A difference frequency Δf0 is calculated from a resonance frequency f0 of a film thickness sensor at a current time a0 and a resonance frequency f1 at an immediate past time a1, and whether the exfoliation has occurred or not is detected from its sign and a comparison result relative to a reference value. When the exfoliation has occurred, a corrected film thickness value T′ is obtained by adding the thickness Δt0 of the exfoliation film to an increased film thickness value T which is determined from a resonance frequency fx measured at a future time ax to be converted to the thickness of a film on a film forming object, and whether the formation of the film should be terminated is judged in comparison to an aimed value. Thus, even if the exfoliation occurs in the film thickness sensor, the film thickness value of the thin film on the surface of the film forming object can be accurately obtained.