Polycrystalline silicon, polycrystalline silicon photovoltaic materials, is a kind of important polysilicon ingot furnace requires extreme pressure inside the furnace should also have a smoke to less than 1 Pa, vacuum unit is roots pump and a single-stage rotary piston vacuum pump, roots and piston vacuum system is mainly used for smelting of polycrystalline silicon material, the limit of unit pressure can reach 1 x10-2 Pa.Due to polysilicon production plants are tens or even hundreds of furnace concentration within a closed air conditioning workshop, so the requirements for vibration and noise of vacuum unit is extremely limited strictly, and it requires vacuum unit under 60 hours continuously trouble-free operation.
In polycrystalline silicon deposition process PEVCD (plasma enhanced chemical vapor deposition), the activity of electrons in the plasma as a catalyst is used, this is to use the glow effect.Glow effect produce environment is in the high vacuum state through the dc high voltage, rf excitation methods such as inert gas such as argon to obtain active electronic.So be sure to use a vacuum pump.
Roots vacuum unit is light weight, low noise, no vibration, good reliability, so usually we are roots vacuum unit is used to meet the needs of the manufacturer.
Generally speaking, in order to obtain high vacuum cleaning, need series more than one job in the region of the different pressure of vacuum pump unit, to complete the extraction task.Typical high vacuum unit, usually with high concatenated roots vacuum pump and plunger pump to form, high vacuum pump such as molecular vacuum pump, cryogenic pump, pump before such as claw type dry pump, roots pump, vortex pump, screw pump, piston pump, diaphragm pump, etc.
High vacuum unit, not only take into account the working pressure range of all kinds of vacuum pump, vacuum pumps, connecting pipes, valves, and system of vacuum gauge and their auxiliary components such as the control unit makes the system cost is very high.A typical high vacuum system additional needs at least three valves and a bypass line.In polysilicon plants, grade vacuum pump before the next layer is generally installed in the workshop, make the backing pump pumping speed loss increased a lot, so you must choose expensive, good performance of the pump.In addition, in some of the modern industrial vacuum applications, such as solar cell preparation, preparation of semiconductor devices, small precision laboratory equipment, etc., by the vacuum pump units take up the space is large, maintenance trouble, extraction efficiency loss, affect the process.
In order to reduce the cost of equipment in vacuum system, realizes the high vacuum to obtain equipment clean, simplification and miniaturization, people has been seeking to achieve high vacuum, and can be in-line atmospheric vacuum pump.