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SEMI F54-1000 © SEMI 2000 5 g. counting efficiency of the CNC as a function of particle size; and h. the lo wer size sensitivit y of the CNC. Appen dix 1 contains an example report form . 15 Precisio n and Accurac y 15.1…

SEMI F54-1000 © SEMI 2000 4

11 Calibration and Standardization

11.1 All flow meters and voltage indicators used in the

apparatus, including instruments incorporated into the

EC and particle counters, must have been checked for

proper calibration against calibrated standards within

the past 12 months. Record all calibration data.

12 Procedure

12.1 Fill the atomizer reservoir with a solution of NaCl

in water. The required NaCl concentration depends

upon the range of particle sizes to be tested, and must

be determined from the atomizer manufacturer’s

specifications. Record the concentration of NaCl in the

solution.

12.2 Determine the required aerosol, sheath air and

excess air flow rates for the EC. The flow rates depend

upon the range of particle sizes to be tested and the

required mobility bandwidth, and must be determined

from the EC manufacturer’s specifications.

12.3 Close the bypass filter valve. Adjust the flow

rates of the atomizer, CNC, and reference instrument to

their manufacturer’s specified values. Adjust the flow

rates of the

EC to their required values as described in

Section 12.2. Adjust the flow rate of the make-up air or

aerosol vent to the required value as described in

Section 10.

12.4 Set the EC voltage to obtain the selected particle

size for testing. Record the voltage setting and the

selected particle size.

12.5 Observe the particle concentration indicated by

the reference instrument. If the particle concentration

exceeds the concentration limit of the reference

instrument or the CNC, adjust the flow rate through the

bypass filter to lower the aerosol particle concentration.

After adjusting the bypass flow rate, check all flow

rates to ensure that they remain at the required values.

Record all flow rates.

12.6 Wait for the particle concentrations indicated by

the CNC and reference instrument to become steady;

the concentrations indicated by each instrument must

not change by more than 5% over a five minute

interval. In order to minimize the error in the recorded

particle concentrations, a minimum of 500 particles

must be counted in a sample. Record the steady

particle concentrations indicated by the CNC and

reference instrument.

12.7 If another particle size is to be tested, return to

Section 12.4.

NOTE 5: At least eight different particle sizes must be tested.

The particle sizes must be selected such that the measured

CNC counting efficiency at least spans the range 50% to 95%

(0.50 to 0.95). In order to eliminate systematic error, the

particles sizes must be tested in random order.

13 Calculation and Interpretation of Results

13.1 When an aerosol electrometer is used as the

reference instrument, correct the measured particle

concentrations for multiple charging, as described in

Section 7.5.

13.2 For each particle size tested, calculate the ratio of

the concentration of particles reported by the CNC to

that reported by the reference instrument. This ratio

represents the counting efficiency of the CNC.

13.3 Plot the calculated counting efficiency against the

particle size as shown in Figure 2. This plot shows the

measured counting efficiency curve of the CNC.

Particle Size

Counting Efficienc

Figure 2

Schematic Plot of Measured Counting Efficiency

13.4 Determine the lower size sensitivity of the CNC,

as defined in Section 5. (The counting efficiency at any

particle size can be estimated using linear interpolation

between the data points.)

14 Reporting Results

14.1 The test record must include the following items:

a. test date;

b. test operator;

c. serial numbers of the reference instrument, CNC

and EC;

d. all particle transport loss calculations as described

in Section 7.4;

e. all flow meter and voltage indicator calibration

data as described in Section 11;

f. all raw data and calculations utilized in the test

method as listed in Sections 12 and 13;

SEMI F54-1000 © SEMI 20005

g. counting efficiency of the CNC as a function of

particle size; and

h. the lower size sensitivity of the CNC.

Appendix 1 contains an example report form.

15 Precision and Accuracy

15.1 This method requires a minimum of 500 particles

counted in a sample. For Poisson distributed data, the

relative standard deviation of the measured particle

concentration is less than 5% when at least 500

particles are counted in a sample.

APPENDIX 1

EXAMPLE REPORT FORM

NOTE: The material in this appendix is an official part of SEMI F54 and was approved by full letter ballot procedures on July 13,

2000 by the North American Regional Standards Committee.

A1-1 Test dates:

A1-2 Operator(s) performing test:

A1-3 Serial numbers: Reference instrument

CNC EC

A1-4 Attach flow meter and voltage indicator calibration data as described in Section 11.

A1-5 Data and calculations:

Data Point (Use Additional Sheets as Necessary)

12345678

NaCl Concentration (gm/l)

Flow Rates (cm

/s)

EC Aerosol

EC Sheath

EC Excess Air

CNC

Reference Instrument

Make-up Air or

Excess Aerosol Vent

EC Voltage (V)

Particle Size (micrometer)

Measured Particle Concentrations (Particles/cm

)

CNC

(1)

(1) Corrected for Transport Loss

(2)*

Reference Instrument

(3)

(3) Corrected for Multiple Charging

(Electrometers Only)

(4)*

(4) Corrected for Transport Loss

(5)*

Counting Efficiency

= (2)/(5)

A1-6 Attach plot of counting efficiency as a function of particle size

A1-7 Lower size sensitivity (micrometer)

∗

___________

∗ Attach calculations.