Semiconductor manufacturing process is complex, and there are many sensitive areas to airborne molecular contamination (AMC). In terms of corrosion control, semiconductor manufacturing will face multiple challenges in the next few years. According to the new white paper on semiconductor roadmap, the size of traditional semiconductors will reach its limit in 2024. However, there will be more kinds of new devices, chip stacks, and system innovations to continuously optimize computer performance, power consumption, and cost. International Roadmap for Devices and Systems (IRDS) shows that the current chip cost reduction method is mainly to reduce polysilicon spacing, metal interconnection spacing and circuit unit height, which will continue until 2024.

The life cycle of chemical filter has a great influence on AMC removal efficiency. According to the International Technology Roadmap for Semiconductors (ITRS), AMC control requirements for wafer environment of lithography scanner are strict, with total inorganic acid target value of 0.05 ppbv, total alkali target value of 0.2 ppbv and volatile organic compound target value of 0.26 ppbv. This article introduces the elements of chemical filtration system, including AMC contamination source, AMC control target value, configuration scheme of chemical filter for fresh air and FFU chemical filter.

AMC contamination source

AMC contamination sources in the clean workshop of semiconductor manufacturing may originate from external air, operators, process, gas release from materials and leakage of equipment in the clean room. The main components of AMC from external gases include sulfur oxides (SOx), nitrogen oxides (NOx), hydrogen sulfide (H2S), ammonia (NH3), volatile organic compounds (VOCs) and ozone (O3), and Ammonia gas (NH3) mainly from the operator. The following table shows the main components and sources of AMC from semiconductor process, gases release from clean room material and external gases according to AMC classification (see Table 1).

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Deployment scheme of chemical filter for fresh air and FFU chemical filter

According to different manufacturing processes of semiconductors, the deployment scheme of fresh air chemical filter and FFU chemical filter will be changed due to many factors, such as outdoor AMC concentration, AMC concentration produced in clean room, fresh air ratio, service life and efficiency of chemical filter, chemical filter coverage rate and so on.

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Schematic diagram of chemical filtration system for MAU and clean room

Example of deployment scheme

Table 2 is an example of the deployment scheme of chemical filter for fresh air and FFU chemical filter. The target AMC is inorganic acid. Assuming that the outdoor concentration is 30 μ g/m3, the chemical filtration coverage rate is 50%, and the internal generation source is 10 μ g/m3, it is necessary to meet the concentration requirements of ITRS for the clean room air and wafer environment of lithography scanner, which are 5ppb and 0.05 ppb respectively. Through the automatic simulation calculation tool by MayAir, the influence of chemical filtration coverage on chemical filtration efficiency, replacement cycle and annual consumption can be simulated. According to the following example, if the chemical filtration coverage rate ≤30%, it cannot meet the environmental concentration requirements. When the coverage rate reaches 40%, it needs to increase the termination filtration efficiency to 90% to meet the environmental concentration requirements. It is a more reasonable deployment when the coverage rate is around 50%-75%. When the coverage is increased to 100%, which means the deployment is too high, it will increase the annual consumption of chemical filtration material.

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MayAir Puro series chemical filters

Puro-F (PF) is a FFU chemical filter with self-contained fan filtration unit (FFU) and with different filter media to effectively remove AMC such as acidic, alkaline, organic and adulterated. Puro-C (PC) box type and Puro-V (PV) V-shape are suitable for make-up air units (MAU) and recirculating air units (RAU) in order to control AMC in the room. The initial efficiency of chemical filter should be above 90%, and the termination efficiency is generally 50-80%. Chemical filter deployment is to customize different filter media formulas for customers according to AMC types to be removed on site, AMC environmental concentration, AMC control concentration, filter service life and other requirements.

Click on the video to watch the MayAir Puro series chemical filters.