Surf-Cal Particle Size Standards: The Best Calibration Solution for Your Laboratory

Introduction

In the high-precision world of semiconductor manufacturing, accuracy and consistency in particle detection and measurement are paramount. Applied Physics Corporation's SURF-CAL™ Particle Size Standards represent the gold standard in calibration tools for Scanning Surface Inspection Systems (SSIS).

These precision-engineered standards enable semiconductor manufacturers to maintain consistent quality control across multiple inspection tools and facilities, ensuring that wafer inspection scanners deliver reliable, comparable results regardless of location.

What Are Surf-Cal Particle Size Standards?

Surf-Cal standards consist of polystyrene latex (PSL) microspheres suspended in deionized, filtered water. These microspheres are sized with exceptional precision using Differential Mobility Analyzer (DMA) or other size exclusionary techniques, resulting in extremely tight size distributions.

Each product comes with NIST traceability, providing the reliability and consistency required for critical semiconductor manufacturing processes.

The standards serve as reference materials for calibrating and monitoring the performance of wafer inspection tools from manufacturers like KLA-Tencor, Hitachi, ADE, and Topcon.

By depositing these precisely sized particles on silicon and patterned wafers, engineers can verify that their inspection systems detect particles of specific sizes correctly.

Key Features and Specifications

Available Particle Sizes

Surf-Cal standards are available in a wide range of particle diameters, from 0.047 μm to 3.04 μm, covering the spectrum of critical particle sizes relevant to modern semiconductor manufacturing.

Each size variant offers tightly controlled size distribution, typically within 0.003 μm to 0.026 μm, depending on the particle diameter.


Some of the most popular particle sizes include:
  • 0.047 μm (47 nm) - Critical for leading-edge semiconductor nodes
  • 0.100 μm (100 nm) - Commonly used reference point
  • 0.202 μm (202 nm) - Standard calibration size
  • 0.498 μm (498 nm) - Nearly equivalent to 0.5 μm reference
  • 1.112 μm (1112 nm) - Larger calibration standard.

Concentration Options

Each particle size is available in two concentration options:
  1. Standard Concentration: 3 × 10⁸ particles per mL
    Price: $495.00 per 50 mL bottle
    Ideal for routine calibration checks.

  2. High Concentration: 1 × 10¹⁰ particles per mL
    Price: $1,495.00 per 50 mL bottle
    Suitable for applications requiring higher particle density.

Packaging and Stability

  • Each standard comes in a 50 mL bottle
  • 12-month stability period from the date of manufacture
  • Each bottle includes a Certificate of Calibration and Traceability to NIST.

Applications in Semiconductor Manufacturing

Calibration and Verification

The primary application of Surf-Cal standards is the calibration and verification of Scanning Surface Inspection Systems. These tools are critical for detecting contaminants and defects on silicon wafers during the manufacturing process. Regular calibration ensures that:

  1. Particle size detection remains accurate over time
  2. Multiple inspection tools provide consistent measurements
  3. Quality standards are maintained across different manufacturing locations.

Performance Monitoring

Semiconductor manufacturers use these standards to:
  • Perform periodic size calibration checks
  • Conduct weekly size and count monitoring
  • Compare scanner performance across different locations
  • Assess SSIS performance at critical manufacturing stages.

How to Select the Right Surf-Cal Standard

When choosing a Surf-Cal Particle Size Standard, consider these factors:

Particle Size Requirement

Select the particle diameter that matches your tool's calibration requirements or the critical particle size for your manufacturing process.

Concentration Need

Choose between standard (3 × 10⁸ particles/mL) or high concentration (1 × 10¹⁰ particles/mL) based on your application requirements.

Inspection Tool Compatibility

Verify that the selected size is appropriate for your specific inspection equipment. Different tool manufacturers may have different recommended calibration particle sizes.

Manufacturing Node

For advanced semiconductor nodes, smaller particle sizes (e.g., 0.047 μm or 0.064 μm) will be more relevant.

Measurement Methodology and NIST Traceability

The certified diameters of Surf-Cal standards are transferred by transmission electron or optical microscopy from NIST standard reference materials. This ensures the highest level of accuracy and traceability.

The uncertainty calculations follow the guidelines established in NIST Technical Note 1297, 1994 Edition: "Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results.

Key measurement parameters include:

  1. Expanded Uncertainty: Calculated with a coverage factor of two (K=2)
  2. Peak Diameter: Calculated using approximately the ±2s range of the particle size distribution
  3. Size Distribution: Calculated as the standard deviation of the whole peak
  4. Coefficient of Variation (CV): One standard deviation expressed as a percentage of the peak diameter
  5. FWHM Distribution: The distribution at half of the peak height expressed as a percentage of the peak diameter.

How to Use Surf-Cal Particle Size Standards?

Step Action
Preparation Turn on the instrument, open the software, and keep the Surf-Cal solution ready.
Solution Mixing Gently but thoroughly shake the bottle to ensure the particles are evenly mixed.
Taking Sample Use a sterile pipette or syringe to take the required amount (e.g., 1 mL) of sample.
Adding to Device Add the sample to the calibration device (such as a particle counter).
Calibration Mode Activation Select the “Calibration” option in the device or software.
Recording Data When the device takes the measurement, note the particle size and count.
Comparison Compare the results with the standard values provided by Surf-Cal.
Adjustment If the device result does not match the standard, adjust the settings.
Verification (Repeat) Repeat the process 1-2 times to ensure calibration is correct.
Save & Finish Save the final results and switch the device back to normal mode.

 Step-by-Step Calibration Process

Preparation

First, turn on your instrument, open its software, and keep the Surf-Cal particle solution ready.

Shake the Solution

Gently but thoroughly shake the bottle to ensure the particles are evenly mixed.

Take the Sample

Use a sterile pipette or syringe to take the required amount of solution (e.g., 1 mL)

Add Sample to Device

Insert the sample into your calibration device, such as a microscope or particle counter.

Start Calibration Mode

On your device or software, select the “Calibration” or “Standardize” option.

Measure and Record Data

Let the device take measurements and note down the values, like particle size and count.

Compare with Standard

Compare the results with the standard values provided with the Surf-Cal solution.

Adjust if Needed

If the results don’t match, adjust the device settings or repeat the calibration process.

Repeat for Accuracy

 To ensure accuracy, repeat the calibration process 1–2 times.

Save and Finish

Once the results are accurate, save them and return the device to normal operation mode.

Ordering Information

Surf-Cal Particle Size Standards can be ordered directly through Applied Physics Corporation. Each product has a specific part number that designates both the particle size and concentration. For example:
  • APPD-047: 0.047 μm diameter at 3 × 10⁸ particles/mL
  • APPD-047B: 0.047 μm diameter at 1 × 10¹⁰ particles/mL
The company offers options to request a quote or add products directly to your order through their website.

Conclusion

Surf-Cal Particle Size Standards represent an essential tool for maintaining quality and consistency in semiconductor manufacturing processes. With their precise sizing, NIST traceability, and range of options, these standards ensure that wafer inspection systems perform reliably and consistently.

By incorporating regular calibration with Surf-Cal standards into your quality control protocols, you can enhance confidence in your inspection results and maintain consistency across multiple tools and facilities.

FAQs

1. How long are Surf-Cal Particle Size Standards stable?
Each bottle is stable for 12 months from the date of manufacture when stored properly.

2. Are Surf-Cal standards compatible with all wafer inspection systems?
Yes, Surf-Cal standards can be used with inspection systems from major manufacturers, including KLA-Tencor, Hitachi, ADE, and Topcon.

3. What is the refractive index of the polystyrene microspheres?
The refractive index is 1.59 at 589 nm (25°C) for all polystyrene microspheres in the Surf-Cal product line.

4. How are the particle sizes certified?
Particle sizes are certified through comparison with NIST standard reference materials using transmission electron or optical microscopy.

5. Can I request custom particle sizes or concentrations?
For specific requirements not covered by the standard product line, contact Applied Physics Corporation directly to discuss custom options.

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