Roots vacuum pump in deposition etching process of practical application
With the rapid development of microelectronics technology, and the reliability of the IC integration demand is higher and higher, relatively speaking, the requirement of IC production equipment is becoming more and more strict, and many of production process is under the vacuum state, how to reasonable use of the vacuum to obtain equipment will be for the device itself and IC products is vital. The practical application of roots vacuum pump in the deposition and etching process is very important. This paper mainly describes the experience of reasonable use of roots pump in semiconductor manufacturing process.
Roots pump is a pump that USES two “8” shaped rotors to rotate in the pump housing to produce the extraction and exhaust gas. The working pressure is 1.33×103~6.65×10-2a. The commonly used range is 2.66×102~6.65× 10-1pa (2~5× 10-3torr).
Because roots pump starts quickly, it has a large pumping speed in a wide pressure range of 1.83×103~ 4.33pa (10-10-2tor), which can reach the ultimate vacuum in a short time. It can extract condensible gas and rapidly discharge the suddenly released gas, making up for the small pumping speed of the mechanical pump at 1.3×103~ 1.33pa (10-10-2tor). Therefore, as a mechanical booster pump, it is widely used in plasma enhanced chemical vapor deposition (PECVD) and low pressure chemical vapor deposition (LPCVD) and etching equipment.
It is true that the gas extracted from the reaction chamber by the former mechanical pump is generally the harmful gas with a large number of corrosive components at a certain temperature, which will make the mechanical pump oil “toxic” and make it discolored, cracked and diluted. This will inevitably reduce the pump pumping speed, or the system should have a background vacuum (deposition ≤ 10-1pa (10-3torr); Etch ≤ 1.33pa (1.0-2torr) directly affects the uniformity, repeatability and etch rate of the deposition, so corresponding measures should be taken to suppress it.
1. Choose anti-oxidation and anti-corrosion pump oil; It is recommended to use perfluorinated oil made from perfluoroether (it is chemically inert, antioxidant, corrosion resistant and radiation resistant, and only produces gaseous substances without polymer under electron and ion bombardment radiation); Or fl-vp-50 CFL oil, also known as polytrifluoroethylene (which has strong fluorocorrosion resistance) to replace regular hydrocarbon oil (silicone oil is not used, it will produce polymer at high temperatures and damage mechanical pumps).
2. Oil filtration system: the mechanical pump oil in the deposition equipment is passed through Fuller ‘earth (the main component of which is montmorillonite minerals). It is capable of absorbing colored substances, organic substances and some mineral impurities, and can be neutralized and adsorbed by alkali and acid after filtration. Or make etching equipment of mechanical pump oil by diatomite Diatomaceous earth (it is made up of the cell walls of diatoms of siliceous a biochemistry sedimentary rocks. With strong water absorption, it can absorb 1.5~4.0 times of its own weight of water.
3, the use of bubbler device: that is, in the mechanical pump in the oil seal chamber continuously filled with a certain amount of nitrogen, so that the pump oil constantly produce bubbles, in order to reduce the concentration of harmful gas, so that it is not dissolved in the pump oil was promptly discharged from the pump body.
In recent years, driven by semiconductor manufacturing, liquid crystal injection, solar photovoltaic, electronic devices, thin film and other emerging industries, as well as traditional industries such as chemical industry and pharmaceutical industry, the field of vacuum application is expanding, the extraction process is becoming more and more complex, and the demand for vacuum pump is becoming higher and higher. From the practical application of roots vacuum pump in deposition etching process, it can be seen that the vacuum pump must be low vibration, low noise, high reliability, corrosion resistance, clean and oil-free. As one of the core equipment, the research and production of vacuum pump are paid more and more attention.