How to choose ULPA for processes that are sensitive to boron?

There is a type of process in semiconductor manufacturing that has extremely low tolerance for boron. In the etching process of ion implantation, doping diffusion, and some advanced processes, trace amounts of boron contamination may affect the electrical performance of the device, and this effect is often only exposed in subsequent tests.

When choosing ULPA for this type of process, a problem arises: conventional glass fiber filter materials may themselves contain boron.

Boron is a common additive during the manufacturing process of fiberglass. Boron-sensitive processes are at risk if the filter media releases boron-containing particles in the air stream, or if the filter media retains boron-containing materials during the manufacturing process. This is not a product defect but an inherent property of the material system. Therefore, the selection should not only look at the grade and resistance, but also whether the material itself is suitable for the process.

First, let’s clarify what “sensitive to boron” specifically refers to.

Different processes have different concerns about boron. Please understand the actual project requirements before selecting.

What indicators are you focusing on? Is it the boron content limit of the filter material, the release concentration of boron in the gas flow, or the amount of boron deposition on the surface of the downstream wafer? The detection methods, sample ranges and judgment standards of these three indicators are completely different.

What are the limits? Trace amounts, trace amounts, and ultra-trace amounts, the corresponding materials and testing requirements vary greatly. Some processes limit boron to the ppb level, while others limit it to the ppt level. The tighter the limits, the higher the cost of material screening and verification.

What are the testing conditions? Temperature, humidity, air flow rate, contact time, these conditions can affect the release behavior of boron. The test conditions should be noted on the test report. Boron content data that is out of condition cannot explain the problem. For specific verification methods, please refer to the relevant instructions of the technical agreement.

Where does the risk come from? Is it released by the filter material itself, or is it introduced during the production, transportation, and installation of the filter material? Different sources require different control measures. Only after confirming these clearly can we judge which material solution is more suitable.

From what links can boron be introduced?

Potential sources of boron are not limited to filter media.

Filter body. Boron is a common component in fiberglass filter media, while PTFE filter media usually does not contain boron. If the project is particularly sensitive to boron, PTFE is usually the preferred filter media direction.

Edge sealants and gaskets. Colloids and sealing materials may contain boron compounds or boron-containing additives. Even if the filter material itself does not contain boron, these auxiliary materials can be a source.

Frame and finish. The coating, anodizing treatment, and surface passivation process of the metal frame may involve boron-containing substances. Some surface treatment formulations for aluminum alloys contain boron.

Packaging materials. If the packaging material of the filter element contains boron, cross-contamination may occur during transportation and storage.

production environment. If boron-containing substances are present in the equipment, tools, and environment that are contacted during the filter manufacturing process, pollution may also be introduced.

Therefore, what you need to check when selecting is the entire material list, not just 'does the filter material contain boron?' The PTFE designation or 'low boron' description alone does not prove that all parts will comply with process limitations. Each piece of material must be supported by corresponding information.

How to check and verify

After determining the material direction, the steps for verification and verification are roughly as follows.

Request a materials list. Ask the supplier for the material composition of the entire product - filter material, support layer, edge sealing glue, outer frame, sealing gasket, and packaging materials. Confirm item by item whether it contains boron or whether it has been treated with low boron.

Confirm the test report. If the project requires boron content or release data, confirm the detection method, sample range, test conditions and judgment criteria. The data of the filter material sample cannot represent the entire finished product, and the test object needs to be confirmed according to the project requirements. For specific testing items, please refer to the relevant instructions for factory testing.

Sample verification. For projects with strict boron control requirements, it is recommended to conduct sample verification first. Test under actual working conditions to confirm whether the release level is within the limit. After the sample is approved, it can be used in batches.

Change management. If there are changes to material suppliers, formulations or production processes, the impact of boron should be re-evaluated. It cannot be assumed that 'the material name is the same' means the performance is the same. For specific procedures, please refer to the instructions related to filter material batch changes.

Installation and maintenance should also be paid attention to. Tools, cleaners, and gloves used during installation may also introduce contamination if they contain boron. Operating procedures when replacing filters should incorporate boron control requirements. involving The selection of ULPA ultra-high efficiency filter can be checked based on specific process requirements.

Selection and Acceptance Checklist

Project judgment example

A certain semiconductor process is sensitive to boron, and the equipment needs to be equipped with an optional ULPA filter.

The supplier provides two solutions: conventional fiberglass U15 and PTFE U15. The grade and resistance of the glass fiber solution meet the requirements, but the filter material itself contains boron, and the project team cannot confirm whether the release level is within the limit. The filter material of the PTFE solution does not contain boron, but the edge sealing glue, sealing gasket and outer frame surface treatment need to be further checked.

Check results: The edge sealing glue is a conventional formula and is not specifically labeled as low boron; the outer frame is anodized, and the treatment solution contains boron. The project team requires suppliers to provide data on the boron content of edge sealants and outer frames, and to assess the risk of release under process conditions.

The key point in this case is: choosing PTFE as the filter material does not mean that the entire product is low in boron. Verification of supporting materials is equally important. involving The logic is the same when selecting HEPA/ULPA air filters .

About Aili Industrial’s material configuration packages

For processes that are sensitive to boron, the core of selection is the controllability of the entire material. The filter material is only one link, and the colloid, seals, outer frame and packaging materials all need to be confirmed one by one.

Aili Industry has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing, and can provide ULPA ultra high efficiency filter、HEPA high-efficiency filter and supporting air supply equipment. For projects with special material requirements, we can assist in checking the filter media type and entire material configuration based on process limitations and installation conditions. When the filter is matched with equipment such as FFU and EFU, the material information and interface conditions can also be confirmed uniformly.

When making an inquiry, specify the boron control requirements, detection methods and limit conditions to help confirm the appropriate material solution. The specific selection is subject to the technical documents and test results confirmed by the project.