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Figure 8. Calibration setup for the miniature diffusion size classifier (DiSC)

CPC

Nebulizer DMA Neutralizer DiSC

Figure 9. Schematic overview of the diffusion charging sensor [4]

Ion Trap Voltage

High Voltage Charging current measurement D F

The d i f f usion si ze c l a ssi f ie r stainless screens. First, particles are
Figure 10. The miniature DiSC, measures
4x9x18cm,weighs 670grams [4] c o m pa r i s o n e x p e r i m e n t i s captured and generate a diffusion
performed with of condensation current. Second, the rest of the
particle counter (TSI model 3775) particles then are arrested in the
and scanning mobility particle sizer high-efficiency particulate air
(UGZ), shown as Figure 6 and Figure (HEPA) filter stage and also the
7, diffusion size classifier has less filter current is measured. Because
accuracy compared to the traditional smaller particles are dominated by
instrument, but gets satisfying the Brownian motion and larger
result to show the capability to particles belong to inertia effected
detecting particles whose diameter motion. The ratio of filter current
less than 100nm. and diffusion current can be a
measurement of the average particle
The diffusion charging sensor is a
size.
simple instrument based on unipolar
charging, and the particle is charged R=I filter / I diffusion
approximately proportional to its
fluctuation. In cleanroom ambient diameter. Excess ions are removed The diffusion charging senor in
measurement, we may get rid of in ion trap after the corona charger. Figure 9 and Figure 10 should undergo
it. With regard to noise, it can be The particle then goes through the i n st r u me nt c a l ibrat ion f rom
counted as the standard deviation diffusion stage, which consists of ccorresponding curve fitting before
of the measurement. an electrical insulated stack of physical application Figure 8. The

NEW FAB TECHNOLOGY JOURNAL JUNE 2013 27