Frequently asked questions

What's the benefit of low pressure plasma cleaner?

When system is cleaned with low pressure plasma cleaner, there is no need to stop turbo pump. It's safe for turbo pump and improves turbo pump lifetime. User only needs to close gun gate valve and shot down other extreme high voltage components in the chamber.
If the pressure inside is significantly higher than 20 mTorr, newly generated radical species will recombine with each other before they can diffuse out of the remote plasma source. Low pressure discharge not only reduce the radical loss inside the cleaning chamber, but also reduce the loss inside the plasma chamber.
If plasma source can be operated at low pressure, the conductance between the source and the chamber can be made very large so that newly generated radicals can easily diffuse into the cleaning chamber.
Our plasma cleaner can ignite and maintain plasma at pressure lower than 0.1mTorr inside the source. Only highly efficient plasma discharge technology can achieve such a low operation pressure. It's an excellent testimony to the efficiency of our plasma cleaner.

How to set up an optimized recipe?

Different vacuum system have different pump speed and different chamber size. Therefore, optimal gas flow rate may vary from system to system. Our plasma cleaners can electronically control gas flow. A pressure sensor monitors source pressure and a plasma probe measures plasma strength. When users set different source pressures, flow controller will automatically adjust gas flow to maintain the set pressure. In the mean time, plasma probe monitors the plasma strength. User can based on plasma probe feedback to optimize the source operation pressure. Flow controller will automatically adjust the required gas flow rate for optimal operation.

The benefit of auto RF impedance matching?

With automatic impedance matching, user never needs to worry about rf mismatch. Our source is always working in optimal rf delivery conditions. In many rf plasma system, to simply optimize reflected RF power to zero may not necessarily means the best RF coupling inside the plasma source. With the help of the plasma probe, our auto impedance matching algorithm can optimize for the best plasma strength in addition to minimum reflected power.

Why burn mask is darker than other areas in SEM images

Research have shown that dark burn marks in electron or ion microscope images are usually caused by polymer carbon deposition. When high energy primary electrons or ions hit the sample surface, they generates lots of low energy secondary electrons (SEs). SEs have much higher interaction cross-section with the ambient contaminant gas molecules due to their lower speed. They break down the hydrocarbon molecules and cause carbon deposition around in the imaging area. Carbon has almost the lowest secondary electrons yield. When surface is covered with thin layer of hydrocarbon desposit, the secondary electron yield will be reduced. Therefore, the electron exposed area will be darker than surrounding unexposed areas. Carbon deposition can reduce material contrast in electron and ion microscope images, especially for low primary electron energy conditions.