In the field of semiconductor manufacturing, air and liquid filters are the core technologies for building a clean production environment, and their performance directly determines the defect density and yield level of chip manufacturing. Semiconductor manufacturing processes are highly sensitive to pollution, and even nanoscale particles or trace chemical impurities can cause device failure or performance degradation. According to ITRS data, 63% of random defects in advanced processes originate from air/liquid pollutants. Therefore, an efficient and reliable filtration system is the key to ensuring chip production.
Air filters are mainly responsible for gaseous pollution control and are the core of clean room environmental control. Semiconductor manufacturing usually takes place in clean rooms with ISO 1-7 levels, with strict limits on the amount of particulate matter in the air. Among them, high efficiency air filter (HEPA) and ultra-high efficiency air filter (ULPA) constitute a three-level purification system. HEPA can filter out 99.97% of 0.3 micron particles, and ULPA can also intercept 99.9995% of 0.12 micron particles, ensuring that the clean room meets ISO Class 1 standards (the number of particles ≥0.1 micron per cubic meter ≤10). In advanced processes such as 3nm, nanoscale particles smaller than 5nm need to be further intercepted to prevent lithography pattern defects. In addition, the chemical filter uses activated carbon-zeolite composite media, which can control the concentration of air molecular pollutants (AMC) such as ammonia gas and sulfur oxides to ppb level to avoid photoresist poisoning and metal layer corrosion. Combined with the vertical laminar flow design and a wind speed of 0.45 m/s, the air filter can reduce the particle diffusion coefficient to below 0.001 cm²/s, ensuring that the deposition pollution on the wafer surface is less than 0.01/cm², and at the same time protecting lithography machines and other precision equipment is protected from particulate matter damage, ensuring lithography accuracy, and isolating harmful gases generated by the etching process for operators.
Liquid filters focus on the purification of liquid media and deeply purify ultrapure water (UPW), etching solutions, photoresists and other process chemicals. It adopts a multi-layer filtration structure. The pre-filter removes large particles of impurities and extends the life of the main filter; the main filter uses polypropylene (PP), polytetrafluoroethylene (PTFE) and other materials to remove fine particles and dissolved impurities; the terminal nanofiber membrane can filter out ultra-fine particles and bacteria. In ultrapure water treatment, the multilayer filtration system combines ion exchange resin to achieve a resistivity of 18.2 MΩ·cm and a metal ion content of less than 1ppt, meeting the lens cleaning requirements of EUV lithography machines; For corrosive process chemicals such as hydrofluoric acid and hydrogen peroxide, the perfluoropolymer membrane can achieve a particle retention rate of over 99.9999% at 0.05μm, ensuring that the etch rate deviation is less than 0.5%; CMP slurry processing is deeply filtered through nanofibers to remove agglomerated particles larger than 50nm and control the scratch rate on the wafer surface to below 0.1 defects/sheet.
The importance of air and liquid filters is reflected in multiple dimensions: significantly improving chip yield by reducing wafer surface defects and pollution; protecting key equipment from corrosion and wear, reducing maintenance costs; stabilizing chemical reaction rates and selectivity, and improving process repeatability; reducing chemical reagent consumption and reducing wastewater treatment costs. In fact, the iteration of filter technology has reduced the defect density at nodes 28nm to 3nm by two orders of magnitude (from 10³ to 10 ³ defects/cm²), promoting the semiconductor industry to continue to follow Moore's Law. As semiconductor technology moves towards 1nm and more advanced processes, the performance requirements for filters continue to increase. Current research focuses on plasma-assisted catalytic filtration technology (which improves VOCs removal efficiency to 99.99%) and nanoporous graphene membranes (which achieves sub-nanometer molecular sieve separation) to meet the challenge of atomic pollution control. In the future, filters will develop in the direction of higher efficiency, longer life and intelligence, continuing to provide a clean and stable production environment for semiconductor manufacturing.
