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SEMI E104-0303 © SEMI 2000, 2003 12 10.1.1 General part : • Date and time of calibration • Name of the operator • Manufacturer of the LPPD • Model and serial number of the LP PD to be calibrated (if sensor and counter ar…
SEMI E104-0303 © SEMI 2000, 2003 11
9.3.5.2 Zero Counting
NOTE 14: The intent of this procedure is not to adjust the
thresholds for the zero count rate but to verify whether the
LPPD is within its specification.
9.3.5.2.1 By running zero gas (with v
L
and V´
L
= V´
0
)
through the system the zero count rate, specified by the
sensor manufacturer, is checked. The reference particle
counter is used to check the quality of the zero gas. The
minimum acceptable sample time is 10 minutes. The
sampling time shall be long enough to provide adequate
sampling statistics. The zero count rate (average counts
per minute) should be recorded in the calibration report
form.
9.3.5.3 Counting Efficiency
NOTE 15: The actual particle concentration is determined
with a reference particle counter with a 100% counting
efficiency for the employed particle size. It is important that
there are no differences between the concentration within the
detection area of the LPPD and the concentration monitored
by the RPC.
9.3.5.3.1 By running a monodisperse aerosol (with v
L
and V´
L
= V´
0
+ V´
G
), the maximum of detected
particles is counted. The ratio of the counts of the
LPPD standardized per mm
2
to the counts of the
reference particle counter per mm
2
detection area (in %)
for each particle size should be recorded in the
calibration report form.
9.3.5.4 Sensitivity
9.3.5.4.1 By running different monodisperse aerosols
(with v
L
and V´
L
= V´
0
+ V´
G
) with particle sizes at the
expected sensitivity where the counting efficiency is
between 40% and 60%, the sensitivity is verified. The
counts of the LPPD per mm
2
detection area compared
to the counts of the reference particle counter per mm
2
detection area (in %) should be determined. The
determined particle size shall have a counting
efficiency between 40% and 60% and should be
recorded in the calibration report form.
9.3.5.5 Particle Size Resolution
NOTE 16: The particle size shall be at least twice the lower
counting limit to ensure measurement of the entire
distribution and accurate characterization of the calibration
response curve below the particle size of interest. The
resolution is specified by the coefficient of variation (in %)
obtained by dividing the portion of the standard deviation of
the distribution σ
LPPD
that is contributed by the LPPD by the
mean size of the distribution d
p
.
9.3.5.5.1 Record the size d
p
and the standard deviation
σ
d,p
of the used particles in the calibration report form.
By running a monodisperse aerosol (with v
L
and V´
L
=
V´
0
+ V´
G
), determine the standard deviation of the
observed particle distribution σ
p,LPPD
. To determine the
standard deviation of the pure sensor signal σ
V,LPPD
, a
pulse height analyzer can measure the voltage peaks at
the analog sensor calibration output. The portion of the
standard deviation of the distribution σ
LPPD
that is
contributed by the LPPD is calculated by the following
formula:
(
)()
2
,
2
, pdLPPDpLPPD
σσσ
−=
9.3.5.5.2 The value of the standard deviation of the
observed distribution σ
p,LPPD
, the standard deviation of
the sensor signal σ
V,LPPD
, and the coefficient of
variation (in %) should be recorded in the calibration
report form.
9.3.6 Non-Sizing LPPD
NOTE 17: For more information and background see
Appendix 2.
9.3.6.1 Zero Counting
9.3.6.1.1 See Section 9.3.5.2.
9.3.6.2 Counting Efficiency
NOTE 18: The actual particle concentration is determined
with a reference particle counter with a 100% counting
efficiency for the employed particle size. It is important that
there are no differences between the concentration within the
detection area of the LPPD and the concentration monitored
by the RPC.
9.3.6.2.1 By running a monodisperse aerosol (using the
smallest particles size which can be counted with v
L
and V´
L
= V´
0
+ V´
G
), the maximum of detected
particles is counted. The counts of the LPPD per mm
2
detection area compared to the counts of the reference
particle counter per mm
2
detection area (in %) and the
employed particle size should be recorded in the
calibration report form. These measurements should be
executed for the defined set of particle sizes including
one size no larger than 1.3 times the sensitivity limit as
specified by the manufacturer.
9.3.7 Interim Procedure
9.3.7.1 Between the settings of the separate thresholds
or the runs with different particle sizes, the system
should be purged with zero gas for a sufficient time.
The aerosol generator should be rinsed with clean
diluent for a sufficient time before adding new
suspension of particles with other size.
10 Calibration Report Form
10.1 The calibration report form shall contain the
following information:
SEMI E104-0303 © SEMI 2000, 2003 12
10.1.1 General part:
• Date and time of calibration
• Name of the operator
• Manufacturer of the LPPD
• Model and serial number of the LPPD to be
calibrated (if sensor and counter are separate,
model and serial number for each)
• Size of the detection area (if detection area is
dependent on the particle size, all established
values)
• Model, serial number, manufacturer, and date of
last calibration of the reference particle counter
• Performance of the reference particle counter
(volume flow, sensitivity, zero count rate)
• Environmental conditions: temperature T
A
, relative
humidity RH, pressure p
• Quality of zero gas as measured with the reference
particle counter (counts per minute)
• Specifications of the particles used for calibration
(manufacturer, certified size and tolerance,
standard deviation σ
d,p
, coefficient of variation,
refractive index, lot number)
• Calibration parameters: particle concentration C
L
,
particle velocity v
L
at the location of the LPPD,
line diameter D
L,
opening area A
RC
of the probe
inlet for each particle size
• Calibration procedure: sizing or non-sizing
10.1.2 For sizing LPPD:
• Size calibration: value of the average voltage of the
different particle sizes, employed particle sizes,
mode or median method
• Size calibration check: values of the thresholds,
employed particle sizes, ratio of the normalized
counts in the corresponding channel (in %)
• Zero counting: value of the zero count rate
(average counts per minute), sampling time
• Particle size resolution: value of coefficient of
variation, value of standard deviation of the
observed distribution, mean size of the distribution,
value of standard deviation of the sensor signal,
employed particle sizes
• Counting efficiency: value of the counting
efficiency (in %), employed particle sizes
10.1.3 For non-sizing LPPD:
• Zero counting: value of the zero count rate
(average counts per minute), sampling time
• Counting efficiency: value of the counting
efficiency (in %), employed particle sizes
10.2 Report significant variations from data reported
from the previous calibration.
11 Related Documents
NOTE 19: These publications related to particle
measurement, vacuum ISPM, and calibration are just
informative to improve understanding of these standard.
Raasch, J.; Umhauer, H.: “Errors in Determination of
Particle Size Distributions Caused by Coincidence in
Optical Particle Counters” Particle Characterization 3,
1990, 424-427
Jaenicke, R.: “The Optical Particle Counter: Cross
Sensitivity and Coincidence” J. Aerosol Sci., 30(5),
1972, 95-111
Borden, P.: “Monitoring Vacuum Process Equipment:
In Situ Monitors – Design and Specification”
Microcontamination, 1991, 43-47
Raabe, O.G.: “The Generation of Aerosols of Fine
Particles” Fine Particles, Ed. Liu, B.; Academic Press,
New York, 1976, 57-110
SEMI E104-0303 © SEMI 2000, 2003 13
APPENDIX 1
PERFORMANCE TESTING
NOTICE: The material in this appendix is an official part of SEMI E104 and was approved by full letter ballot
procedures on July 28, 2000 by the European Regional Standards Committee.
A1-1 The definitions of parameters and measurement
of the terms described in SEMI E10 applies also to
LPPDs and combined LPPD/process equipment.