Vacuum leakage control for semiconductor coating production line

Reconstruction of negative pressure pipelines for coating production line

We have an optical coating factory located in Thailand. The vacuum exhaust pipes of this factory originally used ordinary pneumatic butterfly valves. After the equipment reached the predetermined vacuum level, the pressure would rise within 5 minutes. After replacing the pneumatic vacuum butterfly valve, the rate of pressure recovery was significantly improved, and the replacement of the sealing ring no longer required disassembling the entire valve. The maintenance time was reduced from 4 hours to 40 minutes. Such cases are quite representative in the emerging semiconductor production areas in Southeast Asia.

The impact of vacuum leakage on the semiconductor coating production line

In semiconductor and optical coating production lines in Southeast Asia, the stability of the vacuum system directly affects the quality of the coating layers and the overall efficiency of the equipment. With the concentrated establishment of regional wafer factories and thin film solar production lines, engineering technicians are facing a common problem: vacuum leakage causes fluctuations in chamber pressure and abnormal residual gas partial pressures, ultimately resulting in decreased coating adhesion or pinhole defects. The leakage source is often not in the chamber itself, but in the valve sealing structure at the pipe connection points.

Why are ordinary valves not suitable for vacuum condition

1. Insufficient compression of the sealing ring: At low pressure, the valve plate does not fit tightly with the sealing ring, causing gas to leak along the sealing surface.
2. Leakage at the shaft seal: The rotating part of the valve stem uses a regular O-ring, which will gradually leak over time due to prolonged friction.
3. Valve body gas release contamination: The water vapor and organic substances adsorbed on the surface of the casting slowly release under vacuum conditions, affecting the vacuum degree.

The features of the bidirectional sealed vacuum butterfly valve

1. Bidirectional Seal and Self-Compensating Shaft Seal

   • The vacuum butterfly valve should ensure sealing performance both in the forward and reverse pressure directions. For example, the SONGO GIQ series vacuum butterfly valve has a sealing ring that is simultaneously compressed by the valve plate and the valve body when the valve is closed, achieving zero leakage in both directions; the valve stem adopts a self compensating shaft seal structure, which automatically adjusts the compression force as the wear occurs, preventing external atmospheric reverse infiltration. Such a structure is crucial for the vacuum integrity.
2. Sealing ring material and temperature range
   • The sealing material determines the applicable process window of the valve. FKM can withstand temperatures ranging from -30°C to +150°C and is suitable for medium temperature vacuum pipelines;NBR is also within the temperature range of -25°C to +80°C.
3. Wide pressure adaptability and valve body material
   • The working pressure of the vacuum butterfly valve should cover a wide range from low vacuum to high vacuum. The valve body, valve stem, and valve plate should be made of stainless steel or carbon steel plated with nickel to resist the corrosion of process gases and reduce gas leakage.

In the field of semiconductor coating and vacuum processes, sealing reliability is the foundation for maintaining the vacuum level of the process. Selecting vacuum butterfly valves with bidirectional sealing, self-compensating shaft seals, and wide pressure adaptability helps to reduce leakage risks and unplanned downtime.