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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 appro ved by full letter ballot procedures on July 28, 200 0 by the Europ…
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.
SEMI E104-0303 © SEMI 2000, 2003 14
APPENDIX 2
CALIBRATION NOTES
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.
A2-1 Size Calibration
A2-1.1 Size calibration is performed with
monodisperse particles with known sizes and known
optical properties. The procedure establishes the
voltage response of the LPPD for these particles. The
reported size for unknown particles is the same size of
the monodisperse particle whose voltage response is the
voltage pulse produced by the unknown particle (called
Optical Equivalent Size).
A2-1.2 If an LPPD is able to detect all of the
distribution (see counting efficiency) generated by a
monodisperse aerosol and the size of the particle
standard is known, the calibrating of an LPPD without a
reference particle counter is possible. Ideally, the data
collected by the LPPD observing a monodisperse
aerosol would describe a Gaussian particle size
distribution. However, the reported voltage pulse height
distribution is often not symmetric. Therefore, the mode
and modal values of the pulse height distribution are
not equal. The thresholds for different particle sizes are
set as the mode or median value of the observed
distribution. The modal voltage method is commonly
used.
A2-1.3 The intensity of the scattered light detected by
a photodetector depends on intensity, polarization state,
and wavelength of the incident light beam, diameter,
shape, and refractive index of the particle, as well as on
the geometrical layout of the collection optics and
detector. In the particle size range near the wavelength
(0.1λ < d
P
< 10λ), large oscillations can be seen in the
intensity curve of the light scattered by spherical
particles as a function of all these parameters.
Therefore, the response curve might not be monotonic.
Particles of more than one size will produce the same
voltage output signal. The calibration particles should
be chosen so that their response is not included in such
reversals of the calibration curves.
A2-1.4 For calibration checks, a reference particle
counter (RPC) with a good sizing capability could be
used. The counting efficiency of the RPC shall be 100%
for the particle sizes used in test. The counts of the RPC
and the LPPD under test in the corresponding channel
should be normalized to a standard detection area
(mm
2
).
A2-2 Particle Size Resolution
A2-2.1 Particle size resolution of a particle detector
describes its capability to differentiate between particles
of nearly the same size, or it is a measure of the range
of sizes which the counter would assign to a particular
particle if its size was determined repeatedly. 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 particle size.
A2-2.2 The employed particle size should be at least 2
times larger than the lower detection limit of the
instrument and is within a monotonic response range of
the LPPD response curve. The size d
p
and the standard
deviation σ
d,p
of the used particles is necessary to
calculate the resolution.
A2-2.3 To determine the resolution, the standard
deviation of the observed particle distribution σ
p,LPPD
is
calculated. The quality of the photodetector is checked
by determining the standard deviation of the pure
sensor signal σ
V,LPPD
at the analog calibration output
with a pulse height analyzer. The σ
LPPD
is calculated by
the following formula:
(
)()
2
,
2
, pdLPPDpLPPD
σσσ
−=
A2-3 Zero Counting
A2-3.1 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. It is assumed that
the zero count level of a correct operating LPPD is
sufficiently better than its specification. Failure of the
verification test is due to a physical failure within the
LPPD and not to statistical variation in the
measurement.
A2-3.2 The output of a photodetector and the
electronic circuits of the particle detector is afflicted
with noise. The zero count rate verification is carried
out to ensure that data, especially near the detection
limit of the LPPD, is generated by particles rather than
by noise. To achieve this goal, the basic thresholds for
the LDL are to be set so that a signal-to-noise ratio of at
least 3 dB is ensured. The sampling time shall be long
enough to provide adequate sampling statistics.