case studies

California Measurements instruments have been used for diverse applications in laboratories and at unique onsite locations all over the world. Our samplers are portable and rugged with an excellent track record of reliability for use in the field. Learn more about specific case studies and how results were achieved.

Sampling Airborne Particles in Clean Rooms

Our MPS-4G1 Microanalysis Particle Sampler enables engineers in clean rooms to efficiently collect samples of airborne particles for species identification to solve contamination problems.

When airborne particles cause contamination problems that affect production of devices in a clean room, steps beyond particle counting are required to pinpoint their sources. Samples of the particles need to be collected and analyzed to determine their morphology and physical make-up so that their sources can be ascertained and eliminated. Since particles are mostly in the submicron size range, optical microscopes are not powerful enough to get images of them. A scanning electron microscope (SEM) with much higher magnification capability must be utilized. In addition, with a suitable X-ray detector attachment to the SEM, not only can the morphology of the particles be determined, information on their elemental composition can be gathered as well through the use of energy dispersive X-ray spectroscopy (E.D.X.S.).

Resorting to SEM analysis imposes constraints on how the samples must be presented for analysis in the microscope. For example, the scanning electron beam in the SEM traverses only a small distance, and samples to be analyzed must be mounted on a holder that is usually smaller than an inch in diameter. Furthermore, the holder configuration must fit a mounting jig in the SEM specimen chamber. Thus, if samples are collected on a filter larger than 1 in. dia., only a small portion is cut out and mounted on the sample holder for analysis. When samples are but a few and they are spread out on the filter, they will be difficult to find under high magnification. Therefore, such a filter is not the best collection medium.

It is to overcome this and other constraints that the MPS-4G1 Clean Room Microanalysis Particle Sampler was designed. It utilizes well-established inertial impaction techniques to segregate and collect particles in four size fractions, down to 0.05 microns; it incorporates a standard 0.5 inch dia. SEM sample holder in each impactor stage to have samples collect directly on its substrate. Moreover, the impactor nozzle is designed such that particles are impacted and collected in a highly concentrated spot on the substrate which allows the microscopist to find the samples easily under high magnification.

After samples are collected, the SEM holders are removed and can be inserted directly into the SEM for analysis with minimal or even no sample preparation, saving much of the microscopist’s time. Thus, the MPS-4G1 is a system designed especially for the collecting of samples for SEM analysis. Over more than a decade, it has proven itself to be a most useful tool for helping solve airborne particle contamination problems at many clean facilities for producing semiconductors, computer disk drives and other technology-based products.