What are PSL’s?
Polystyrene Latex beads are produced with NIST Size Traceability from 20 nanometers to 160 microns. Polystyrene Latex Spheres are used as size standards with a refractive index about 1.53. PSL spheres are suspended in a DI Water solution at a specific size in an atomizer or nebulizer, which is used to create a particle aerosol with a narrow particle size distribution and be analyzed by a laser particle counter or SSIS wafer inspection system for size response calibration.
What are PSL’s in Layman Lingo?
OK, think of them as real precise sized small rubber balls that are deposited onto the Substrate surface.
How do PSL’s stick to the Substrate surface?
They are held on by Surface ElectroStatic Adhesion.
Can I clean a dirty PSL Standard?
No, you cannot remove just the dirt and leave the PSL’s.
I cleaned my PSL Standard and now I get 2 Histogram peaks instead of one! Why?
When you cleaned, it you made the some of the PSL stick to each other and produce a different size that is not NIST traceable. You now have made it completely bad.
Is the PSL Standard a Particle Size and Sphere Count Standard?
No, ONLY a SIZE Standard. NOT a Count Standard.
Why does the 0.30 and 0.50 micron PSL Standards all come out around the 0.30 micron range on 488nm Argon Ion Laser on Tencor 6220 model?
a. The 0.50 micron is close to the 488nm wavelength and will report as close to 0.30 micron. For more details: Look up MIE Scattering effect.
b. It counts all the particles, some Laser Based Inspection Tools just mis-classify them.
Can I send in my Standards to have them ReCertified with NIST paperwork?
a. No, the NIST guide lines do not allow this.
b. You can send them to us and we can rescan them and let you know how dirty they are.
Do NIST Standards go bad?
a. Sometimes. Due to handling or storage they can:
a.i. Grow a haze film on the substrsate or PSL Spheres.
a.ii. Gain dirt on the surface. This causes the Histogram to flatten out.
a.iii. Scan the Standard with too high of Laser power and can melt them.
Bad? What happens when the PSL spheres grow a haze on them?
This is really bad. The Scanning system will now call the Standard a larger size then what was on the wafer and the NIST documentation reports. Example-Your 0.50 um Standard now reads 0.80 um!
Can you make me a Custom Standard on Film Wafer, PHOTOMASK, Clear Wafers?
Absolutely! Tell us what you need and we can Quote it.