Design method for film thickness uniformity of magnetron sputtering coating

The design of film thickness uniformity in magnetron sputtering coating is a complex and critical process, involving multiple factors. Below is a comprehensive design approach:

I. Defining System Attributes
Film thickness uniformity in sputtering coating is an indirect measure of the final standard of the coating process, encompassing various aspects of the coating process. Therefore, producing high-quality films with good film thickness uniformity requires establishing a comprehensive design system for sputtering coating film thickness uniformity, categorizing, summarizing, and identifying the internal connections of all aspects of sputtering coating.

II. Establishing the Design System
The comprehensive design system for large-area sputtering coating can be divided into three major parts: engineering design of coating equipment, design of coating processes, and computer numerical simulation design of various processes. Each part is further divided into several aspects, and they interact with each other.

Engineering Design of Coating Equipment

• Vacuum System: The design of the vacuum system is a relatively mature part, mainly including chamber structure, material selection, design of vacuum components, and selection of vacuum pumps and gauges. The design of the chamber structure should consider strength, stiffness, stability, and also the feasibility and simplicity of processing techniques. Material selection should meet requirements such as low saturated vapor pressure, good thermal and chemical stability, ease of degassing, and low permeability. The design of vacuum components includes vacuum sealing, electrode introduction, piping, and valves. The selection of vacuum pumps and gauges can follow common engineering requirements.

• Electromagnetic Field: Relatively accurate electromagnetic field design involves simulating the electromagnetic field during the sputtering process, rather than just simulating the electromagnetic field of the magnetron sputtering equipment when it is not in operation. The choice of power supply should be determined based on different process requirements, with common options including DC power supplies, medium-frequency power supplies, RF power supplies, and hybrid power supplies capable of multiple power supply modes. In terms of material selection, for RF power supplies, electrode materials with high surface conductivity and good chemical stability are required, and oxygen-free copper is commonly used in industry. Materials within the magnetron target can be classified based on magnetic permeability, with magnetic shoes being high-permeability materials, typically industrial pure iron. The design of the anode and shielding should consider spatial position, potential relationships, dimensions and area, and anode material properties to ensure stable sputtering.

• Gas Distribution: The distribution of gases is extremely important for plate substrate coating. Mechanical structural design should be employed to minimize the variation rate of gas density within the sputtering deposition area, while maximizing the conductance of the system outside the area to improve gas utilization and pumping system efficiency. Mechanical components or structures controlling gas distribution include gas distribution systems, vacuum chamber structures, and pumping systems.

• Heating System: The heating system is used to meet the temperature conditions required for vacuum system baking and film growth.

Design of Coating Processes
Consideration should be given to the need for different deposition processes for different thin film materials, the implementation of different sputtering techniques (DC, medium-frequency, RF, pulsed, reactive sputtering, as well as technologies developed through combinations of these techniques or the application of new technologies), adjustments to process parameters for the same technique (power, pressure, deposition mode, etc.), pretreatment (cleaning, preheating, etc.), and post-treatment (heat treatment, etc.).

Computer Numerical Simulation
High-performance computer simulation design provides strong support for the design of coating equipment and coating processes. Through computer simulation, various parameters in the coating process can be simulated and optimized to improve film thickness uniformity.

III. Key Factors and Optimization

• Magnetic Field Uniformity: Efforts should be made to ensure the uniformity and directional consistency of the magnetic field, creating a relatively uniform spatial magnetic field. Positions with stronger magnetic fields will have thicker films, while those with weaker magnetic fields will have thinner films. The direction of the magnetic field is also an important factor affecting uniformity.

• Pressure Uniformity: Efforts should be made to ensure vertical uniformity of pressure. When designing the vacuum chamber, consider the installation position of the vacuum pump, the gas inlet method, and the layout of process gas pipes within the chamber. Under certain pressure conditions, positions with higher pressure will have thicker films, while those with lower pressure will have thinner films.

• Target-Substrate Distance: The target-substrate distance is also an important factor affecting uniformity. During the coating process, the target-substrate distance should be reasonably controlled to achieve the best coating effect.

IV. Implementation and Monitoring

Implementation Process: Manufacture and install coating equipment according to the design plan, and adjust and optimize coating processes.
Monitoring and Feedback: During the coating process, monitor the quality and uniformity of the coating in real-time, and provide timely feedback and adjustments based on monitoring results.

In summary, the design method for film thickness uniformity in magnetron sputtering coating involves multiple factors, requiring comprehensive consideration and optimization of the design system, coating equipment, and coating processes. Through implementation and monitoring, the quality and uniformity of the coating can be continuously improved to meet various application requirements.