High-purity gas piping technology is an important part of high-purity gas supply system, which is the key technology to deliver the required high-purity gas to the point of use and still maintain the qualified quality; High-purity gas piping technology includes the correct design of the system, the selection of fittings and accessories, construction and installation, and testing. In recent years, the increasingly strict requirements on the purity and impurity content of high-purity gases in the production of microelectronics products represented by large-scale integrated circuits have made the piping technology of high-purity gases increasingly concerned and emphasized. The following is a brief overview of high-purity gas piping from material selection of construction, as well as acceptance and daily management.
Types of common gases
Classification of common gases in the electronics industry：
Common gases（Bulk gas）: hydrogen (H2), nitrogen (N2), oxygen (O2), argon (A2), etc.
Specialty gases are SiH4 ,PH3 ,B2H6 ,A8H3 ,CL ,HCL ,CF4 ,NH3, POCL3, SIH2CL2 SIHCL3 ,NH3, BCL3 ,SIF4 ,CLF3 ,CO ,C2F6, N2O ,F2, HF ,HBR SF6 …… etc.
The types of special gases can generally be classified as corrosive gas, toxic gas, flammable gas, combustible gas, inert gas, etc. The commonly used semiconductor gases are generally classified as follows.
(i) Corrosive / toxic gas: HCl , BF3, WF6, HBr , SiH2Cl2, NH3, PH3, Cl2, BCl3 …etc.
(ii) Flammability gas: H2, CH4, SiH4, PH3, AsH3, SiH2Cl2, B2H6, CH2F2, CH3F, CO…etc.
(iii) combustibility gas: O2, Cl2, N2O, NF3 … etc.
(iv) Inert gas: N2, CF4, C2F6, C4F8, SF6, CO2, Ne, Kr, He…etc.
Many semiconductor gases are harmful to human body. In particular, some of these gases, such as SiH4 spontaneous combustion, as long as a leak will react violently with the oxygen in the air and begin to burn; and AsH3 highly toxic, any slight leakage may cause the risk of human life, it is because of these obvious dangers, so the requirements for the safety of the system design is particularly high.
Application scope of gases
As an important basic raw material of modern industry, gas products are widely used, and a large number of common gases or special gases are used in metallurgy, steel, petroleum, chemical industry, machinery, electronics, glass, ceramics, building materials, construction, food processing, medicine and medical sectors. The application of gas has an important impact on the high technology of these fields in particular, and is its indispensable raw material gas or process gas. Only with the needs and promotion of various new industrial sectors and modern science and technology, the gas industry products can be developed by leaps and bounds in terms of variety, quality and quantity.
Gas application in microelectronics and semiconductor industry
The use of gas has always played an important role in the semiconductor process, especially the semiconductor process has been widely used in various industries, from the traditional ULSI, TFT-LCD to the current micro-electro-mechanical (MEMS) industry, all of which use the so-called semiconductor process as the manufacturing process of products. The purity of the gas has a decisive impact on the performance of components and product yields, and the safety of the gas supply is related to the health of personnel and the safety of plant operations.
The significance of high-purity piping in high-purity gas transport
In the process of stainless steel melting and making material, about 200g of gas can be absorbed per ton. After the processing of stainless steel, not only its surface sticky with various contaminants, but also in its metal lattice also absorbed a certain amount of gas. When there is airflow through the pipeline, the metal absorbs this part of the gas will re-enter the airflow, polluting the pure gas. When the airflow in the tube is discontinuous flow, the tube adsorbs the gas under pressure, and when the airflow stops passing, the gas adsorbed by the tube forms a pressure drop to resolve, and the resolved gas also enters the pure gas in the tube as impurities. At the same time, the adsorption and resolution are repeated, so that the metal on the inner surface of the tube also produces a certain amount of powder, and this metal dust particles also pollute the pure gas inside the tube. This characteristic of the tube is essential to ensure the purity of the transported gas, which requires not only a very high smoothness of the inner surface of the tube, but also a high wear resistance.
When the gas with strong corrosive performance is used, corrosion-resistant stainless steel pipes must be used for piping. Otherwise, the pipe will produce corrosion spots on the inner surface due to corrosion, and in serious cases, there will be a large area of metal stripping or even perforation, which will contaminate the pure gas to be distributed.
The connection of high-purity and high-cleanliness gas transmission and distribution pipelines of large flow rates.
In principle, all of them are welded, and the tubes used are required to have no change in organization when welding is applied. Materials with too high a carbon content are subject to the air permeability of the welded parts when welding, which makes the mutual penetration of gases inside and outside the pipe and destroys the purity, dryness and cleanliness of the transmitted gas, resulting in the loss of all our efforts.
In summary, for high-purity gas and special gas transmission pipeline, it is necessary to use a special treatment of high-purity stainless steel pipe, to make high-purity pipeline system (including pipes, fittings, valves, VMB, VMP) in high-purity gas distribution occupies a vital mission.
General concept of clean technology for transmission and distribution pipelines
Highly pure and clean gas body transmission with piping means that there are certain requirements or controls for three aspects of the gas to be transported.
Gas purity: The content of impurity atmosphere in the gGas purity: The content of impurity atmosphere in the gas, usually expressed as a percentage of gas purity, such as 99.9999%, also expressed as the volume ratio of impurity atmosphere content ppm, ppb, ppt.
Dryness: the amount of trace moisture in the gas, or the amount called wetness, usually expressed in terms of dew point, such as atmospheric pressure dew point -70. C.
Cleanliness: the number of contaminant particles contained in the gas, particle size of µm, how many particles/M3 to express, for compressed air, usually also expressed in terms of how many mg/m3 of unavoidable solid residues, which covers the oil content.
Pollutant size classification: pollutant particles, mainly refers to pipeline scouring, wear, corrosion generated by metal particles, atmospheric soot particles, as well as microorganisms, phages and moisture-containing gas condensation droplets, etc., according to the size of its particle size is divided into
a) Large particles – particle size above 5μm
b) Particle – material diameter between 0.1μm-5μm
c) Ultra-micro particles – particle size less than 0.1μm.
In order to enhance the application of this technology, to be able to perceptual understanding of particle size and μm units, a set of specific particle status is provided for reference
The following is a comparison of specific particles
|
Name /Particle size (µm) |
Name /Particle size (µm) | Name/ Particle size (µm) |
| Virus 0.003-0.0 | Aerosol 0.03-1 | Aerosolized microdroplet 1-12 |
| Nuclear fuel 0.01-0.1 | Paint 0.1-6 | Fly ash 1-200 |
| Carbon black 0.01-0.3 | Milk powder 0.1-10 | Pesticide 5-10 |
| Resin 0.01-1 | Bacteria 0.3-30 | Cement dust 5-100 |
| Cigarette smoke 0.01-1 | Sand dust 0.5-5 | Pollen 10-15 |
| Silicone 0.02-0.1 | Pesticide 0.5-10 | Human hair 50-120 |
| Crystallized salt 0.03-0.5 | Concentrated sulfur dust 1-11 | Sea sand 100-1200 |
Post time: Jun-14-2022