VPI Tech Support: Methods for Estimating Film Thickness During Sample Coating Preparation Using a Coating Machine and Specific Calculation Logic

VPI Tech Support: Methods for Estimating Film Thickness During Sample Coating Preparation Using a Coating Machine and Specific Calculation Logic

In the fields of materials science and engineering, thin film preparation is a critical step. Accurately controlling the thickness of the thin film is essential for ensuring product performance and quality. This article introduces how to estimate film thickness and the specific calculation logic when using a coating machine for sample preparation, helping researchers and engineers improve experimental efficiency and result reliability.

Importance of Film Thickness Estimation

The thickness of a thin film directly affects its optical, electrical, and mechanical properties. In industries such as semiconductors, optical coatings, and biomedical applications, precise control of film thickness is key to ensuring stable product performance. Therefore, mastering film thickness estimation methods and calculation logic is of great significance to experimental and production processes.

Methods for Estimating Film Thickness During Sputtering

 1. Sputtering Rate Method

The sputtering rate refers to the thickness of the film deposited on the substrate per unit time, usually expressed in nanometers per minute (nm/min). The sputtering rate is influenced by the following factors:

- Target Material Characteristics: Different materials have different sputtering yields.

- Power Density: Higher power increases the sputtering rate.

- Gas Pressure and Type: Affects plasma density and energy.

- Substrate Position: The closer to the target material, the higher the sputtering rate.

Calculation Logic:

1. Conduct a preliminary experiment, recording the sputtering time `t₁` under specific conditions and the corresponding film thickness `d₁`.

2. Calculate the sputtering rate `R = d₁ / t₁`.

3. When estimating the required film thickness `d₂`, calculate the necessary sputtering time `t₂ = d₂ / R`.

2. Quartz Crystal Microbalance Method (QCM)

QCM is a real-time monitoring technique for film thickness changes, measuring the change in oscillation frequency of a quartz crystal to calculate the deposited mass.

Calculation Logic:

1. Use the Sauerbrey equation: `Δf = - (2f₀²Δm) / (A√(ρqμq))`, where `Δf` is the frequency change, `f₀` is the crystal's fundamental frequency, `Δm` is the mass change, `A` is the effective area, and `ρq` and `μq` are the density and shear modulus of the quartz crystal.

2. By using known parameters and the measured frequency change, calculate the film thickness `d`.

3. Optical Monitoring Method

Utilizing the principle of optical interference, film thickness is calculated in real-time by monitoring changes in reflected or transmitted light.

Calculation Logic:

1. Establish the relationship between film thickness and optical signal based on optical interference conditions.

2. Real-time monitoring of optical signal changes allows for the calculation of corresponding film thickness.

Specific Calculation Example

Using the sputtering rate method as an example for film thickness estimation:

Known Conditions:

- Preliminary experiment sputtering time `t₁ = 10 minutes`.

- Measured film thickness in the preliminary experiment `d₁ = 50 nm`.

Calculate Sputtering Rate:

R = d₁ / t₁ = 50 nm / 10 min = 5 nm/min

Objective:

- Required film thickness `d₂ = 100 nm`.

Calculate Necessary Sputtering Time:

t₂ = d₂ / R = 100 nm / 5 nm/min = 20 minutes

Conclusion:

Under the same sputtering conditions, sputtering for 20 minutes will achieve a film thickness of 100 nm.

VPI's Professional Coating Solutions

VPI (www.vpichina.com / www.vpi2004.com ) specializes in providing advanced coating equipment and technical support, helping customers achieve high-precision film thickness control.

- High-Precision Equipment: Our coating machines are equipped with advanced sputtering sources and precise control systems to ensure stable sputtering rates.

- Real-Time Monitoring: Supports multiple real-time film thickness monitoring methods such as QCM and optical monitoring.

- Professional Support: Offers comprehensive technical training and after-sales service to help customers master film thickness estimation and calculation methods.

Accurate estimation and control of film thickness are crucial for high-quality thin film preparation. By mastering estimation methods such as the sputtering rate method, QCM method, and optical monitoring method, along with the related calculation logic, the controllability of the coating process can be effectively enhanced. VPI Boyuan Weilang is committed to providing customers with the highest quality coating solutions and looks forward to collaborating with you to drive innovation and development in the industry.