Reliable Chemical Batch Sampling Data Collection
Particle Measuring Systems (PMS) has been developing products for the microelectronics industry for decades. We know contamination, how it starts and where it goes in your system. As a result, we know the best methods to counter the spread of impurities and how to greatly reduce them from entering into your process. Learn how to effectively generate reliable data from your sensitive chemical batch sampling processes.
Clean, Clean, Clean
The appearance of contamination on a report comes down to how clean and stable (not shedding particles) your equipment is. For this reason, Particle Measuring Systems recommends the following cleaning procedure with your highly-sensitive batch sampling particle counters:
- Appropriate container cleaning is a prerequisite for stable and repeatable data acquisition. A PMS-tested
“clean” container was found to become contaminated again just by emptying the beaker and refilling it with
another chemical. Nanoparticles are shed as a result of surface tension changes from the gas and/or liquid
- Flushing is necessary to avoid bubbles when sampling the chemical from the bottle. Some chemicals may
need to “settle” for a period of time in a temperature-controlled room to eliminate the bubbles and obtain
- To reduce the influence of external contamination, a preparation of 500 ml or more of the inspection sample
is recommended. To improve the reliability of data, it is also recommended to prepare a separate sample for
flushing. If possible, flush the Chem 20 particle counter before starting sample testing with the SLS-20 chemical batch sampler.
- In the SamplerSight software, recipes include the option of discarding a count equal to or greater than 1 to
allow the removal of the initial sample data due to potential contamination.
PMS has developed an effective multi-step method for clean fluid sampling: 1) rinse, 2) wash, 3) chemical rinse, 4) ultrasonic energy. All steps are usually necessary to cleanliness required for sampling ultrapure fluids. For you, this means reaching the same standard for every batch because the underlying procedure is kept constant. In a study performed by PMS, this cleaning method allowed a container to be flushed with low count levels.
When sampling 20 nm particles, there are some additional parameters to the cleaning procedure. Beakers and other vessels tend to shed particles after they are emptied and filled with sample fluid. Filling and shaking generate particles that adhere to the vessel walls due to surface tension. However, adding a small amount of ultrasonic detergent and scrubbing the inner walls of the container with a soft bristle brush is greatly effective. By following up with 30 minutes of ultrasonic cleaning and flushing with DI water, containers will contribute no additional particles to your sample fluid.
In the next blog in our 20-nm sampling series, we’ll take a close look at the process chemicals studied with the SLS-20 and Chem 20 sampling system. How does sulfuric acid, cyclohexanone, and ammonia hydroxide perform? Download the full paper here or stay tuned and find out!