Frequently Asked Questions about the PT7160 Plasma Reactor
Q. What is the difference between plasma etching or ashing and glow discharge?
A. Glow discharge is an "imperfect plasma". Glow discharge
is used to alter surface energies to convert hydrophobic (water hating)
surfaces
into hydrophilic (water loving). Glow discharge will also remove adsorbed gases
from chambers of vacuum systems and in so doing improve pump down speed and
ultimate vacuum levels. However, this is the limit to what glow discharge can
do. It will not etch or ash samples.
RF plasma reactors can alter surface energies, de-gas and remove materials
from samples in a controlled way (etching or ashing).
Q. What is the difference between etching and ashing?
A. Ashing is the total removal of organic matter by use of an oxygen plasma. If the sample contains no mineral matter it will totally ash away leaving no residue (ash). The by-products of this process are the removal of carbon oxides and water vapour which are pumped away by the vacuum pump. Etching is the controlled removal of layers or part layers of material, and is usually confined to semiconductor applications.
Q. How automated is the PT7160?
A. After initial set up of the operating conditions, further process runs need only two button operation. First button runs the entire process. A second button vents the chamber.
Q. When must a " Fomblin " pump be specified?
A. When oxygen is to be used as a process gas. Oxygen has the potential to combine explosively with normal organic types of rotary pump oils. Fomblin is a synthetic oil and will not react in this way. Fomblin is also more resistant to most of the highly corrosive gases often used in plasma reactions (especially semiconductor).
Q. What is the capacitance manometer (PT7161) and when should it be specified as an option?
A. The capacitance manometer measures vacuum. The PT7160 Plasma Barrel Reactor uses a conventional Pirani gauge for this purpose. However, if corrosive halogenated gases are used on a regular basis, they have the potential to attack and break down the Pirani head. In such cases (mainly semiconductor applications) the capacitance manometer option is strongly recommended, as it unaffected by corrosive gases.
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