Abstract

Particles in wet electronic chemicals may cause localized masking, residues, pinholes, bridging, abnormal nucleation, and film defects on wafers, glass substrates, or fine circuitry, ultimately resulting in higher defect rates, increased filtration loads on equipment, and fluctuations in production yield.

When sourcing wet electronic chemicals, it is not sufficient to compare only terms such as “electronic grade,” “low particle,” or a single total particle count. Effective comparison requires alignment of the minimum reported particle size, counting method, unit, sampling point, test method, and sample condition. Particle changes should also be evaluated across the final filtration outlet, filled packaging, post-transport samples, and point-of-use locations.

This guide focuses on three questions: whether particle data from different suppliers can be compared directly, whether a filter rating can represent the particle level of the finished product, and how post-packaging testing and continuous batch data can be used to identify sources of particle contamination.

Three Core Judgments in Wet Electronic Chemicals Particle Control

Particle Data Comparability

Particle data comparability for wet electronic chemicals means that two sets of test results can be used for supplier comparison only when the particle size threshold, counting method, reporting unit, sampling location, detection principle, and sample conditions are consistent, or when correlation has already been established.

If any key condition differs, two reports showing that the particles “pass” cannot be used directly to determine which product has the lower particle level.

Filter Rating Does Not Equal Finished-Product Particle Level

A filter’s rated particle size describes its particle retention or removal performance under specified test conditions. It does not mean that particles larger than the rated size are absent from the filtered liquid.

After passing through the filter, the chemical continues to contact downstream piping, valves, filling equipment, containers, seals, and dip tubes. Any of these components may reintroduce particles.

Post-Packaging Particle Validation

Post-packaging particle validation compares samples from the final filtration outlet, after filling, after transportation, and at the equipment point of use under the same testing conditions. It is used to determine whether filling, packaging, storage, transportation, or the customer’s delivery system introduces additional particle contamination.

For particle-sensitive wet processes, passing a test before filling does not necessarily mean that the delivered product will pass.

How Particles Translate into Wet-Process Defects

Wet electronic chemicals are widely used in wafer cleaning, wet etching, photolithography development, photoresist stripping, electroplating, surface treatment, and precision electronic materials processing, where broader electronic-grade chemicals quality control also requires coordinated management of particles, moisture, trace metals, packaging, and batch consistency.

The effect of particles depends on particle size, quantity, morphology, chemical composition, surface properties, and the interaction between the particles and the process surface.

Particle risk cannot be judged simply by assuming that smaller particles are always more dangerous. Larger particles may directly create visible defects, while smaller particles may become significant when present in high numbers, when they agglomerate, or when they are located in critical pattern areas.

Particle specifications should therefore be linked to the actual process window rather than copied from a universal particle limit.

Four Common Misjudgments in Particle Specification Comparison

Misjudgment 1: Comparing Only One Total Particle Count

If Supplier A reports cumulative particles above 30 nm and Supplier B reports cumulative particles above 50 nm, the two sets of data cannot be compared directly, even when the reporting units are the same.

A larger reporting threshold excludes more small particles, making the result appear lower.

Misjudgment 2: Mixing Cumulative and Differential Particle Counts

A cumulative particle count usually includes all particles greater than or equal to a specified size, such as “≥50 nm.”

A differential particle count represents particles within a defined size range, such as “50–100 nm.”

These two data formats answer different questions. If the counting method is not confirmed, particles may be double-counted or suppliers may be ranked incorrectly.

Misjudgment 3: Treating the Filter Rating as the Finished-Product Specification

The statement “a 20 nm filter is used” only indicates that a filter with a particular rating has been installed in the filtration system. It does not replace finished-product particle testing.

The following information must also be reviewed:

• The test method used to determine the filter rating;
• The test particles and test medium;
• How filtration efficiency is calculated;
• The actual flow rate and differential pressure;
• The stage of filter service life;
• Whether downstream piping and filling systems have been validated.

Misjudgment 4: Testing Only Pre-Filling Samples

When the particle count at the final filtration outlet is low but increases significantly after filling, the contamination may come from the filling line, container surface, valves, seals, or dip tubes.

Finished-product release data should therefore correspond, whenever possible, to the final commercial packaging rather than only to an intermediate sampling point on the production line.

How to Convert Process Risk into Comparable Particle Specifications

Define Product Identity and Use Conditions

An inquiry or specification review should include at least:

• Product name and CAS number;
• Concentration or mixture composition;
• Product grade;
• Process application;
• Operating temperature;
• Whether the chemical is recirculated;
• Whether additional point-of-use filtration is applied;
• Whether it contacts wafers, glass, metal layers, photoresists, or other materials;
• Whether the process is sensitive to gels, colloids, or polymer particles.

The same chemical may have very different particle tolerance requirements when used for cleaning, development, or etching.

Establish Meaningful Particle Size Channels

Particle specifications may include multiple size channels according to process sensitivity, for example:

• ≥20 nm;
• ≥30 nm;
• ≥50 nm;
• ≥100 nm;
• ≥200 nm.

These particle sizes are examples for specification design and do not represent universal limits for all wet electronic chemicals.

Particle size channels should be selected based on:

• Historical process defect data;
• Device or line dimensions;
• Point-of-use filtration capability;
• Particle baselines of currently qualified products;
• Stable detection capability of the liquid-borne particle counter;
• Wafer or substrate surface defect inspection results.

Standardize Particle Count Units

Common units include:

• particles/mL;
• particles/L;
• counts/sample.

When counts/sample is used, the sample volume must also be stated. Without the volume, the result cannot be converted or compared with other data.

Fix the Sampling Location

Particle data must correspond to a clearly defined sampling point, such as:

• Final filter inlet;
• Final filter outlet;
• Filled container;
• Delivered package after transportation;
• Customer point of use.

Different sampling locations represent different contamination stages.

Conditions That Must Be Aligned Before Comparing Supplier Particle Data

If any critical condition differs, the particle counts should not be used directly to rank suppliers.

How to Review Liquid Particle Testing Methods

Minimum Detectable Particle Size

The minimum detectable particle size of a liquid-borne particle counter determines how small a particle the report can cover.

SEMI C77 addresses the counting efficiency of liquid-borne particle counters with minimum detectable particle sizes between 30 and 100 nm. When such methods are used, the applicable standard version, instrument model, and chemical medium should also be confirmed.

A lower detection limit does not automatically mean more accurate data. The following factors must also be considered:

• Instrument background noise;
• Optical properties of the sample;
• Refractive index of the chemical medium;
• Bubble interference;
• Flow stability;
• Cleanliness of the sampling system;
• Repeatability of the test results.

Equivalent Optical Particle Size

Light-scattering liquid-borne particle counters generally determine particle size from the scattering signal. The reported result is closer to an equivalent optical particle size than to a direct measurement of the true geometric size of each particle.

Particle material, shape, refractive index, and the chemical medium can all affect the scattering signal.

Data from different instruments or suppliers should only be plotted on the same trend chart after correlation has been established.

Online and Offline Testing

Online testing is suitable for monitoring:

• Changes in filter condition;
• Continuous particle trends on the production line;
• Short-term abnormalities;
• Cleaning and product changeover processes.

Offline testing is suitable for:

• Incoming inspection;
• Packaging sample comparison;
• Retained sample retesting;
• Supplier sample qualification.

A stable quality system usually does not rely on only one method. It establishes correlation among online trends, post-packaging release results, and incoming retest data.

How to Validate Filtration Performance

Verify All Wetted Materials

It is not sufficient to review only the name of the filter membrane. Filtration validation should separately confirm:

• Filter media;
• Support layers;
• Filter element structure;
• Housing;
• Sealing materials;
• Fittings and other wetted components.

Identical material names do not necessarily indicate identical resin grade, manufacturing method, cleanliness, or extractables performance.

Filtration Parameters and Their Procurement Significance

Particle Removal Efficiency

Particle removal efficiency for an individual size channel can be expressed as:

Particle Removal Efficiency = (Particle Count at Filter Inlet − Particle Count at Filter Outlet) ÷ Particle Count at Filter Inlet × 100%

This calculation is meaningful only when:

• The inlet and outlet use the same test method;
• Particle size channels are identical;
• Reporting units are identical;
• Flow rate, temperature, and sampling conditions are stable;
• The inlet particle count is sufficient for statistical evaluation;
• Filter condition and test time are recorded.

When the inlet particle concentration is too low, a single removal-efficiency result can be strongly affected by random variation.

Standard Testing and Actual Chemical-Medium Validation

SEMI C82 is used to evaluate the particle removal performance of liquid filters rated from 20 to 50 nm. SEMI C89 addresses related testing for liquid filters rated below 30 nm.

Standard-particle testing is useful for comparing basic filter performance, but it cannot fully replace validation in the target chemical medium.

Particles in actual wet electronic chemicals may include:

• Inorganic particles;
• Polymer fragments;
• Gels;
• Colloids;
• Corrosion products;
• Materials released from packaging or seals.

The morphology and surface properties of these particles may differ from those of standard test particles.

Four-Stage Validation from the Filter Outlet to the Point of Use

Stage 1: Final Filtration Outlet

This sampling point is used to determine whether the final filtration system can achieve the specified particle level.

The following information should be recorded:

• Filter model and lot number;
• Service time;
• Flow rate;
• Differential pressure;
• Chemical temperature;
• Wetting and flushing conditions;
• Particle counts for each size channel.

Stage 2: Filled Commercial Packaging

Samples should come from a packaging system identical to that used for commercial orders, including:

• The same container material;
• The same capacity;
• The same valve;
• The same sealing components;
• The same dip tube;
• The same filling line and filling method.

Laboratory sample bottles cannot replace commercial packaging validation.

Stage 3: Delivered Sample After Transportation and Storage

This stage is mainly used to identify:

• Particle release from container surfaces or components;
• Effects of transportation vibration;
• Precipitation or agglomeration caused by temperature changes;
• Particle drift during storage;
• Abnormalities in sealing or venting structures.

Stage 4: Equipment Point of Use

Point-of-use data reflect the actual condition of the delivered product after passing through connection lines, chemical delivery systems, recirculation tanks, and point-of-use filters.

If the delivered sample passes but particle levels increase at the point of use, the problem is more likely to be located in the customer’s delivery or equipment system rather than in the chemical production stage.

How to Locate Particle Sources Through Sampling Results

This table is intended to establish investigation priorities and does not replace on-site sampling or failure analysis.

How to Use Packaging Particle Increment

A project may use “packaging particle increment” internally to determine whether filling and packaging introduce additional particles:

Packaging Particle Increment = Post-Filling Particle Count − Final Filtration Outlet Particle Count

This indicator should only be used when:

• Both datasets use the same particle size channels;
• Reporting units are identical;
• The same test method is used;
• Sampling and flushing procedures are consistent;
• Sample temperature and condition are comparable.

Packaging particle increment is not a universal industry release standard and should not be used to draw supplier conclusions from a single batch. Its main purpose is to monitor continuous batch trends and changes in the packaging system.

How to Identify Particle Drift Using Continuous Batch Data

A passing result from one batch only shows that the tested sample met the requirements at the time of testing. It does not prove that the supplier has consistent control capability.

Different Containers from the Same Batch

This comparison is used to identify:

• Differences in container cleanliness;
• Stability of the filling line;
• Differences among valves and dip tubes;
• Representativeness of packaging sampling.

Consecutive Production Batches

This comparison is used to identify:

• Changes in filter service life;
• Changes in upstream particle load;
• Equipment cleaning effectiveness;
• Effects of raw material or production changeover;
• Gradual contamination of the packaging system.

Different Production Periods

This comparison is used to identify:

• Changes before and after maintenance;
• Effects of restart after extended shutdown;
• Changes in production location;
• Changes in filling line or packaging supplier;
• Seasonal temperature and storage effects.

Trend analysis should include at least:

• Average;
• Maximum;
• Minimum;
• Batch-to-batch variation;
• Direction of change in each particle size channel;
• Continuous trends approaching the specification limit;
• Investigation and corrective action results.

Even if consecutive batches remain below the specification limit, a gradual movement toward the limit may indicate deterioration in filter loading, equipment cleanliness, or packaging stability.

Changes That Require Revalidation

The following changes may alter particle performance:

• Filter media;
• Rated filtration level;
• Filter supplier;
• Filtration flow rate or differential pressure;
• Final filtration location;
• Filling line;
• Container resin grade;
• Packaging supplier;
• Valve, seal, or dip tube;
• Production location;
• Filling location;
• Liquid-borne particle counter model;
• Minimum reported particle size;
• Sampling procedure;
• Cleaning and pre-flushing procedure.

A change notification should not state only that “the product specification remains unchanged.” Even when chemical composition and purity specifications remain unchanged, particle distribution may still be affected by changes in equipment, filtration, or packaging.

How to Review Particle Fields in Specifications and COAs

Particle results should also be reviewed through cross-checking COAs, product specifications, TDSs, and SDSs, because each document serves a different purpose and cannot replace batch-specific numerical data.A statement such as “Particle: Pass” cannot be used for batch trend analysis.

A particle-related COA should include at least:

• Particle size threshold;
• Actual particle count;
• Reporting unit;
• Specification limit;
• Test method;
• Corresponding lot number.

An SDS can help define storage, transportation, and material-compatibility boundaries, but it cannot demonstrate that the particle specification has been met.

Wet Electronic Chemicals Supplier Particle-Control Capability Assessment

Supplier scoring cannot replace sample testing and actual equipment validation, but it can reduce the number of candidates without adequate testing or packaging-control capability entering mass-production trials.

Total Cost of Particle Control

The cost of particle control for wet electronic chemicals is not limited to the purchase price.

The following costs should also be considered:

• Point-of-use filter replacement frequency;
• Chemical consumption for delivery-system flushing;
• Isolation of abnormal batches;
• Wafer or substrate reinspection;
• Particle abnormality investigation;
• Packaging change and revalidation;
• Equipment downtime or validation delays;
• Emergency qualification of alternative products;
• Return, replacement, and disposal of nonconforming packaging.

A lower-priced product with unstable post-packaging particle performance may increase point-of-use filtration load and abnormality-investigation costs.

Lead-time evaluation should also consider:

• Preparation time for dedicated packaging;
• Supply of filters and wetted components;
• Filling-line scheduling;
• Dangerous-goods transportation arrangements;
• Export and destination documentation;
• Time required for revalidation.

Common Risk Signals

The following situations require further investigation:

• The specification only states “low particle” without particle size channels;
• The COA only shows “Pass” without actual results;
• Different batches use different minimum reported particle sizes;
• Particle data do not identify the sampling point;
• Cumulative and differential particle counts are mixed;
• The filter rating has no corresponding test method;
• Only standard-particle test data are provided, without describing performance in the target chemical medium;
• Only the filter outlet is tested, while the final packaging is not;
• Laboratory samples and commercial products use different packaging systems;
• Significant differences exist among containers from the same batch;
• Filtration or packaging changes occur without revalidation;
• Reported values are extremely low, but no blank or repeatability data are provided;
• Production location, filling location, or packaging supplier changes without notification;
• Continuous batch results gradually approach the specification limit.

Wet Electronic Chemicals Particle-Control Procurement Checklist

Product and Process Information

• Product name and CAS number are consistent
• Concentration, composition, and product grade are defined
• Process application and contact materials are specified
• Operating temperature, recirculation mode, and point-of-use filtration conditions are defined
• Purity and process-relevant critical impurity requirements are listed

Particle Specification

• Minimum reported particle size is defined
• Particle size channels are defined
• Cumulative and differential counting methods are distinguished
• Particle reporting units are consistent
• Limits for each particle size channel are defined
• Sampling points correspond to the reported particle data
• Requirements for gels, colloids, or soft particles are specified where relevant

Test Method

• Liquid-borne particle counter model or detection principle is defined
• Counting efficiency or calibration method is defined
• Sampling-line and sample-container materials are defined
• Pre-flush volume and stabilization time are defined
• Bubble and background-noise handling methods are defined
• Test temperature, flow rate, and number of replicates are defined
• Data averaging and outlier-handling rules are defined

Filtration Validation

• Filter media and all wetted materials are defined
• The rated filtration level is linked to a test method
• Filter inlet and outlet data are comparable
• Removal efficiency has been evaluated for each particle size channel
• Flow rate and differential pressure ranges are recorded
• New-filter wetting, flushing, and initial release have been validated
• Compatibility in the target chemical medium has been evaluated
• Filter replacement criteria and change-notification requirements are defined

Samples and Batches

• Laboratory samples have been obtained
• Samples in final commercial packaging have been obtained
• Filter outlet and post-filling data have been compared
• Delivered samples after transportation have been validated
• Different containers from the same batch have been compared
• Continuous batch data have been obtained
• Abnormal-batch investigation and corrective-action processes are defined

Documentation and Packaging

• COA includes actual particle results, limits, units, and method
• SDS or MSDS version is applicable to the target market
• TDS or product specification has been obtained
• Filtration validation documentation has been obtained
• Packaging materials and all wetted components are defined
• Storage conditions and post-opening use conditions are defined
• Transportation method and dangerous-goods requirements have been reviewed
• Export documents, labels, and destination requirements have been reviewed

Commercial and Delivery Conditions

• Sample quantity and sample cost are defined
• Minimum order quantity is defined
• Commercial packaging specification is defined
• Standard lead time and first-order lead time are defined
• Delivery destination and transportation method are defined
• Payment terms are defined
• Incoterms are defined
• Production, filtration, filling, and packaging change notifications are agreed

ChemicalCell Support

For wet electronic chemicals particle-control projects, ChemicalCell can assist in confirming available products, samples, and documentation based on the product name, CAS number or composition, concentration, target particle size channels, particle limits, test methods, packaging specifications, and delivery destination.

When supplier comparison is required, particle specifications, COA fields, filtration documentation, commercial packaging, continuous batch data, minimum order quantity, and delivery arrangements can also be reviewed.

FAQ

Can particle counts from different suppliers be compared directly?

They can only be compared directly when the minimum reported particle size, counting method, unit, sampling point, test method, and sample conditions are consistent, or when correlation has already been established.

If any key condition differs, a lower numerical result does not necessarily mean better particle control.

Does a 20 nm filter mean that there are no particles larger than 20 nm in the liquid?

No.

A 20 nm rating usually describes the filter under a specified test method and set of conditions. Filtration efficiency is also affected by particle properties, the chemical medium, flow rate, differential pressure, filter condition, and the downstream packaging system.

The final product still requires post-packaging particle testing.

If the filter outlet passes but the particle count increases after packaging, what should be checked first?

Priority areas include:

• Downstream piping after the filter;
• Filling valves;
• Filling connectors;
• Container inner surfaces;
• Seals;
• Dip tubes;
• Sampling and pre-flushing procedures.

Different containers from the same batch should also be compared to determine whether the problem comes from one package or the entire filling system.

What are the respective applications of online and offline particle testing?

Online testing is more suitable for monitoring continuous trends, filter condition, and process abnormalities.

Offline testing is more suitable for incoming inspection, packaging comparison, retained-sample retesting, and supplier sample qualification.

The two methods should be correlated using stable samples.

What fields should a particle-related COA include at minimum?

It should include at least:

• Particle size threshold;
• Actual particle count;
• Reporting unit;
• Specification limit;
• Test method;
• Corresponding lot number.

A statement such as “Particle: Pass” is insufficient for supplier comparison and batch trend analysis.

RFQ Information

When submitting an inquiry for wet electronic chemicals, the following information may be provided:

• Product name;
• CAS number or mixture composition;
• Concentration;
• Product grade;
• Process application;
• Purity and critical impurity requirements;
• Target particle size channels;
• Particle limits for each size channel;
• Test method;
• Sampling-point requirements;
• Sample quantity;
• Per-batch or annual demand;
• Commercial packaging capacity;
• Container and wetted-component material requirements;
• Whether post-filling or post-transportation particle data are required;
• Whether continuous batch data are required;
• COA, SDS, TDS, and special validation-document requirements;
• Storage and transportation conditions;
• Minimum order quantity;
• Target lead time;
• Delivery destination;
• Payment terms;
• Incoterms;
• Change-notification requirements for filtration, filling, and packaging.

To confirm available grades, particle specifications, commercial packaging, sample conditions, and supporting documentation, please submit your wet electronic chemicals requirements with the product identity, target particle channels, quantity, and delivery destination.