FOUP storage areas should evaluate molecular contamination according to the specific requirements of wafers, containers and equipment, paying attention to external inputs, material outgassing and operating processes. The fact that the room particles are qualified or that there is no peculiar smell cannot be used as a substitute for the relevant gas investigation. The interior of FOUP is a micro-environment, and the data in the room cannot represent it.

First make it clear which air boundary is being evaluated

The assessment of molecular contamination in FOUP storage areas is prone to ambiguity at the boundaries. The room air, the air inside the storage cabinet, and the air inside the FOUP box are three different sets of conditions. The qualified particle cleanliness of the room can only indicate the particle level in the room; whether the FOUP box is affected by molecular contamination depends on the sealing state of the box, box opening operation, circulation in the cabinet and the residence time of the wafer itself. Before evaluation, it should be clear whether the protection object is the wafer surface, the environment inside the box, or the air in the cabinet, and then decide the detection point. Regarding the difference between microenvironment and room conditions, please refer toHow should gaseous contamination be prevented from crossing into the wafer transfer area?。

External input and internal outgassing should be checked separately.

The sources of molecular contamination in the FOUP storage area can be roughly divided into two categories: external input and internal outgassing. External inputs include acidic and alkaline gases in adjacent process areas, volatiles in the cleaning area, and air brought in by opening doors and logistics channels; internal outgassing comes from the FOUP body material, wafer box lining, storage cabinet seals, and cleaning residues. The control positions of the two types of sources are different: external input relies on door area pressure difference, buffering and inlet filtration, and internal air release relies on in-cabinet circulation filtration and material management. Without distinguishing the source, it is easy to change the circulation filter element in the cabinet frequently, but it still cannot solve the input problem at the moment of opening the door.

The evaluation object should follow the wafer process

Different process nodes and products have different sensitivity to molecular contamination, and a general list cannot cover all FOUP storage areas. Lithography-related areas may be more concerned about alkaline gases, wet processes may be concerned about acidic components, and metal layers or special materials may also be sensitive to organic components and siloxanes. When evaluating, the process steps, wafer materials and equipment requirements of the storage area service should be combined to list key gas objects, rather than just measuring a total TVOC. For methods involving the determination of alkaline gas sensitive targets, please refer toHow should the filtration target be determined when the photoresist is sensitive to alkaline gases?。

Detection points and time periods must cover actual operations

The contamination level in the FOUP storage area fluctuates with door opening, access and cleaning operations, and static background data is not enough to explain the problem. The detection points should cover the inside of the cabinet, the door of the cabinet and adjacent areas, and the time period should cover different states such as opening the door for access, storage after cleaning, and long-term resting. If you only sample when no one is operating, you may miss short-term peak values; if you only measure the air in the cabinet without looking inside the FOUP box, you may underestimate the actual contact conditions of the wafer. The sampling method should also correspond to the target gas and cannot be inferred from odor or particle counts alone. For the arrangement of sampling periods, please refer toThere is a peculiar smell only when the machine is turned on. At what time should the gas be measured?。

Aili industrial supporting equipment

For micro-environment projects such as FOUP storage, we usually confirm with the customer whether the protection boundary is the air in the cabinet or the environment in the box, and then determine whether the filter section should be placed in the cabinet circulation, entrance or local air supply position. Aili Industry can provide selection packages for box-type, flat-plate and V-type chemical filtration products. For box-type MAU packages, please refer toMAU box type chemical filter , product series can be viewedChemical filter product range . Equipment-side applications can adopt the form of chemical filtration FFU, integrating chemical adsorption layer and HEPA/ULPA particle filtration. The chemical-first-particle structure is suitable for micro-environments that require AMC control. The compact filter element can be adapted non-standardly according to the cabinet space and circulating air volume. The V-shaped structure provides a large filtration area in a limited space, helping to control surface velocity and resistance. The manufacturing end covers motors, fans, control systems, sheet metal and complete machine assembly. The interfaces between the filter section and the cabinet circulation fan can be aligned in the same package. The specific gas effect, applicable environment and replacement cycle still need to be verified based on the corresponding configuration data and on-site working conditions. The actual results are subject to on-site leak detection and gas detection results.

Related questions and answers

If the particles in the room are qualified, does the FOUP box still need to be assessed for molecular contamination?
need. Particle and molecular pollution are two different indicators. Qualified particles in the room do not mean that the gas in the box meets the wafer requirements. The tightness of the microenvironment within the box and material outgassing need to be evaluated individually.

What gases will the FOUP storage area focus on evaluating?
Depending on the process step and wafer material being served, common areas of concern include alkaline gases, acidic gases, and organic components. Key objects should be listed in conjunction with process requirements rather than just measuring the total amount.

Can Aili Industrial assist in filtering and selecting FOUP storage areas?
The filter section position and product form can be checked based on the storage cabinet structure, circulating air volume and target gas, and the compact space can be adapted in a non-standard way. The specific configuration needs to be confirmed based on product information and site conditions.

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Key points for selection and acceptance inspection