Tingting Z
Nov 6, 2024
In modern industrial manufacturing, thin-film technology is widely used in semiconductors, optical devices, decorative coatings, and other fields. The thickness of the thin film directly affects the performance and quality of the product. Therefore, real-time monitoring of film thickness during the coating process is crucial. VPI's R&D engineers will introduce why coating equipment needs to be equipped with a film thickness monitor and explain its working principle, focusing on the applications of the 650MH high-vacuum magnetron sputtering coating machine and the 900M sample preparation coating machine.
Why Is a Film Thickness Monitor Needed
Precise control of thin-film thickness is a key factor in ensuring product performance. A film layer that is too thick or too thin can lead to instability in product performance, affecting key indicators such as conductivity, optical properties, or mechanical strength. Real-time monitoring of film thickness can prevent over-deposition, saving material and time costs. It also allows for timely adjustment of process parameters to avoid rework or waste caused by film thickness deviations. Different applications have strict requirements on film thickness; precise control can meet the needs of various complex processes and enhance product competitiveness.
Working Principle of the Film Thickness Monitor
Quartz Crystal Microbalance (QCM)
The Quartz Crystal Microbalance is one of the most commonly used film thickness monitors. Its working principle is based on the piezoelectric effect and resonance frequency changes of quartz crystals.
Piezoelectric Effect
Quartz crystal is a piezoelectric material with an orderly arrangement of internal atomic structures. When mechanical force is applied to it, it causes an uneven distribution of electric charges, generating an electrical signal. Conversely, applying an electric field causes mechanical deformation, making it vibrate.
Relationship Between Frequency Change and Mass
When coating material is deposited on the surface of the quartz crystal, the mass of the crystal increases, leading to a decrease in its resonance frequency. According to the Sauerbrey equation, the change in frequency is proportional to the deposited mass. By measuring the frequency change, the film thickness can be accurately calculated.
Components of QCM
- Quartz Crystal Sensor: Has specific frequency, resistance, and electrode materials.
- Sensor Head: Stabilizes the temperature of the crystal, providing a stable measurement environment.
- Electronic Monitor or Controller: Provides alternating current to make the crystal vibrate, monitors frequency changes in real-time, and calculates film thickness.
Selection of Electrode Materials
Quartz crystal electrodes are usually made of gold or silver. Gold electrodes are suitable for general evaporation or sputtering processes, while silver electrodes perform better in high-current deposition (such as carbon rod evaporation) due to their better conductivity, allowing for a more accurate reflection of film thickness changes.
Applications of the 650MH High-Vacuum Magnetron Sputtering Coating Machine and the 900M Sample Preparation Coating Machine
650MH High-Vacuum Magnetron Sputtering Coating Machine
- High-Precision Film Thickness Control: Equipped with advanced QCM film thickness monitors, capable of achieving nanometer-level film thickness control under high-vacuum conditions.
- Wide Range of Applications: Suitable for fields requiring high purity and high precision, such as semiconductors and optical coatings.
- Strong Stability: The high-vacuum environment reduces the introduction of impurities, improving the quality of the thin film.
900M Sample Preparation Vacuum Coating Machine
- Economical and Efficient: Suitable for coating processes that do not require high vacuum, reducing equipment and operating costs.
- High Flexibility: Also equipped with a film thickness monitor, it can meet the film thickness control needs of general industrial applications.
- Easy Operation: Ideal for the production needs of educational research and small to medium-sized enterprises.
Film thickness monitors play an indispensable role in coating equipment, ensuring precise control of thin-film thickness and improving product quality and production efficiency. The Quartz Crystal Microbalance (QCM), as a mainstream film thickness measurement technology, utilizes the piezoelectric effect and frequency change principles of quartz crystals to provide high-precision film thickness measurements.
Our 650MH high-vacuum magnetron sputtering coating machine and 900M low-vacuum coating machine are respectively suitable for coating needs requiring high precision and general precision. Both are equipped with advanced film thickness monitors to meet the diverse needs of different customers. For more information, please visit our website or contact our technical team.