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SEMI E104-0303 © SEMI 2000, 2003 5 5.2 Space, Distanc es, and Installation 5.2.1 The use of an LPPD should not have a negative impact on t he process perf ormance. The sensor location in the equipment shall en sure an op…
SEMI E104-0303 © SEMI 2000, 2003 4
same detected scattering intensity as the localized light
scatterer (LLS) under investigation under identical test
conditions.
4.2.16 particle size for applications, size is the
optical equivalent diameter of a reference sphere with
known properties as detected by a given light-scattering
particle counter [as defined in SEMI C6.5 and SEMI
C6.6]. For calibration, size is the mean diameter of the
monodisperse sphere.
4.2.17 resolution the capability of the particle
detector to differentiate between particles of similar
size.
NOTE 3: The procedure to define resolution is discussed in
Section 9.2.3.5.
4.2.18 sensitivity in particle measurement: the
smallest standard particle size specified by the
manufacturer that an instrument, method, or system is
capable of measuring under specified conditions (with a
counting efficiency of 50%; see Appendix 2). Also
called minimum detectable particle size.
4.2.19 ultrafine particle a particle with an
equivalent diameter less than 0.1 µm [as defined in ISO
14644-1].
4.2.20 ultra-low penetration air (ULPA) filter filter
with a minimum particle-collection efficiency of
99.9995% on the most penetrating particle size.
4.2.21 zero count the maximum particle count
indicated by a particle counter, in a specified period of
time, that is sampling particle-free air. This value is
specified by the manufacturer, and is commonly also
referred to as false call rate, false count, noise, or noise
level.
4.2.22 zero gas in determining contaminant
contribution by gas distribution system components, a
purified gas that has an insignificant particle
concentration above the lower detectable limit (LDL) of
the analytical instrument. This gas is used for both
instrument calibration and component testing.
4.3 Symbols
4.3.1 A
L
the detection area (mm
2
), defined through
detector optics and light beam of the LPPD.
4.3.2 A
RC
the opening area (mm
2
) of the probe inlet
of the reference particle counter.
4.3.3 C
L
the number concentration (cm
-3
) of
particles in the line at the LPPD.
4.3.4 C
G
the number concentration (cm
-3
) of
particles generated from aerosol generator at given V´
G
.
4.3.5 D
L
the diameter of the pump line (mm) at the
LPPD.
4.3.6 d
p
the diameter of the spherical particle (µm).
4.3.7 D
RC
the diameter of the sample drawing line
(mm) for the reference particle counter.
4.3.8 D
VM
the diameter of the pump line (mm) at the
velocity meter.
4.3.9 p the line pressure (torr or mbar).
4.3.10 RH the relative humidity (%).
4.3.11 T
A
the ambient temperature (° C) around the
measurement or calibration system.
4.3.12 T
G
the gas temperature (° C).
4.3.13 v
L
the velocity (m/s) of the aerosol at the
LPPD.
4.3.14 v
L, min
, v
L, max
for applications, the velocity
range (m/s) of the aerosol at the LPPD specified by the
manufacturer.
4.3.15 V´
L
the volume flow rate (l/min) in the line
at the LPPD.
4.3.16 V´
G
the volume flow rate (l/min) of the
aerosol sample (measured directly behind the aerosol
generator).
4.3.17 v
VM
the velocity (m/s) of the aerosol at the
velocity meter.
4.3.18 V´
ZG
the volume flow rate (l/min) of the zero
gas.
4.3.19 σ
V,LPPD
the standard deviation of the voltage
sensor signal.
4.3.20 σ
p,LPPD
the standard deviation of the observed
particle distribution
4.3.21 σ
d,p
the standard deviation of the particles
given by the particle supplier
5 Mechanical Interfaces
5.1 Flanges
5.1.1 One of the following vacuum flanges should be
used for mounting an LPPD into a pump line or on
process equipment:
ISO 2861-1 and ISO 2861-2 (ISO-KF/MF)
ISO 1609 (ISO-K and ISO-F)
ISO 3669 (ISO-K-CF)
SEMI E104-0303 © SEMI 2000, 2003 5
5.2 Space, Distances, and Installation
5.2.1 The use of an LPPD should not have a negative
impact on the process performance. The sensor location
in the equipment shall ensure an optimum use of the
sensor sensitivity in order to allow a measurement
which is representative of the main particle flow. The
influence of the process and the process equipment on
the LPPD shall be minimized (thermal background
radiation, vibrations etc.)
5.2.2 The standard does not specify where an LPPD
should be located in original equipment, or where space
should be allowed for retro-fitting. It is recognized that
the location is dependent on factors including transport
behavior of particles, thermal background radiation etc.
The designers of semiconductor process equipment
should resort to the experience of application engineers
of the LPPD suppliers and the end users. However, in
either case designers shall take into account access
requirements for maintenance and re-calibration. In the
case of retro-fitting, the design should facilitate sensor
installation rather than hinder it.
6 Electrical Interfaces
6.1 Sensor/Controller Communication
6.1.1 Depending on the choice of the LPPD supplier
and the semiconductor equipment manufacturer, one of
the following interfaces for data exchange between the
LPPD and process equipment controller should be used.
6.1.2 Sensor/Actuator Network (SAN)
6.1.2.1 The electrical interfaces of the Sensor/ Actuator
Network are described in the suite of SEMI E54
standards.
6.1.3 Serial Communication
6.1.3.1 RS 232 C (V.24/V.28)
6.1.3.2 RS 485
6.1.4 Others
6.1.4.1 IEEE 488 or IEC 60625
6.2 Others
6.2.1 Sensor calibration output (direct analog output)
6.2.1.1 The analog output for access to the sensor
signal used for calibration purpose should be supported.
7 Communication Interfaces
7.1 Sensor Bus Communication
7.1.1 It is recommended to use a Sensor/Actuator
Network (SAN) for the intra-tool communication
between the LPPD controller and the controller of the
process equipment. This communication is based on a
suite of SEMI standards including a network
communication standard, several common device
models (DeviceNet, SDS, Lonworks, ProfiBus etc.),
and the specific device model for the sensor. The
Network is described by the following suite of SEMI
standards: SEMI E54. The specific device model for
ISPM is described by SEMI E54.10.
7.2 SEMI Equipment Communication (SECS)
7.2.1 If LPPD controllers provide the collected particle
data to the process equipment controller, factory
automation system, or SPC system, the SECS tool-to-
host communication could be used. SECS is described
in the following standards:
• SEMI E5
• SEMI E4
• SEMI E37
7.3 Attribute Definitions
7.3.1 SEMI E54.10 addresses the minimum attributes,
services and behavior an ISPM-device shall support. If
any attributes and services are used by communication
of the ISPM and the equipment controller via IEEE 488
(IEC 60625) or serial communication, they should be
concurring.
8 Operating Conditions
8.1 To specify the operating conditions of an LPPD
(temperature, humidity, electromagnetic compatibility,
vibrations etc.) refer to the following standards:
• IEC 60654-1
• IEC 60654-2
• IEC 60654-3
• IEC 60654-4
• IEC 60801-1
8.2 Temperature
8.2.1 The LPPD should work correctly at an ambient
temperature range T
A
as specified in ISO 14644-5. If
the use of an LPPD at an extended ambient temperature
range is required, the specific LPPD should comply
with these conditions.
8.2.2 The temperature T
G
inside the pump line or
inside the process equipment depends on the actual
application. The application engineers shall check the
use of LPPDs under these specific conditions. The
temperature T
G
is measured at the flange which the
LPPD is mounted on.
SEMI E104-0303 © SEMI 2000, 2003 6
8.3 Humidity
8.3.1 The LPPD should work correctly at an ambient
humidity range RH as specified in ISO 14644-5. If the
use of an LPPD at an extended ambient humidity range
is required, the specific LPPD should comply with
these conditions.
8.4 Electromagnetic Compatibility
8.4.1 The equipment should comply with SEMI E33.
8.4.2 Sensors will be incorporated into equipment
either as original equipment or retro-fitted. In either
case, the sensors or the equipment of which they are a
part should comply with the current regulations
covering EMC in the country or region where the
equipment or sensor is used.
8.5 Vibrations
8.5.1 Process equipment designers are advised to
consider the impact of vibration on the performance of
the sensor while it is collecting data. Therefore, they
should minimize vibrations. The designers of the LPPD
sensors are also advised to consider the impact of
vibrations on the equipment at a time the sensor is not
collecting any data. It might be possible that these
vibrations are stronger than those occurring while the
sensor is collecting data.
9 Reference Calibration Procedure
9.1 The response of real contamination particles,
typically with refractive indices and shapes different
from calibration particles, will differ slightly from the
results obtained by the procedures in this document. It
is known that LPPDs with different optical design may
not produce the same data from identical aerosol
samples. This may happen even with similar LPPDs if
calibration differences have occurred. Therefore, before
the first use the sensor should be calibrated by the
manufacturer. This calibration should be compliant
with or should be reviewed with the following reference
calibration equipment and procedure. This reference
calibration allows the characterization of the
performance of the LPPD under test. The LPPD should
be recalibrated at regular intervals and also in case of
unusual measurement readings to ensure correct results.
9.1.1 The parameters calibrated for LPPDs with sizing
capability are:
• Sizing calibration,
• Resolution,
• Zero counting,
• Counting efficiency, and
• Sensitivity.
9.1.2 The parameters calibrated for LPPDs with non-
sizing capability are:
• Zero counting, and
• Counting efficiency.
9.1.3 Field calibration may not necessarily require the
calibration of all parameters performed by calibration at
the sensor manufacturers site.
9.1.4 Due to the fact that different LPPDs might be
working with different detection areas A
L
, the number
of counts should be printed out in counts per mm
2
detection area. Therefore, a comparison of the
measurement results of different LPPDs is possible.
The size of the detection area A
L
shall be reported in
the calibration report form. Any changes of calibration
parameters or of the calibration setup shall be reported
in the calibration report form. A copy of the calibration
report form shall be delivered with the sensor.
9.2 Apparatus
9.2.1 Materials
9.2.1.1 Particles
9.2.1.1.1 Calibration particles are polymer spheres
composed of polystyrene or a similar polymer, having a
refractive index of 1.58-1.61+ 0i (absorption coefficient
α = 0), a sizing accuracy of at least 95%, and a size
distribution in which the coefficient of variation is 5%
or less. They should be traceable to a nationally or
internationally recognized standard (e.g. NIST
9
).
9.2.1.1.2 The calibration particles are normally
supplied in concentrations too high to be used directly
in aerosol generators. The particles should be dispersed
and diluted in either deionized, distilled water in
accordance with ASTM D1193, Type 1, or Isopropanol.
The diluent should be cleaned using a filter with a pore
size no more than 10% of the size of the particles being
used. The solution should be stored in a clean container.
For generation and dilution of the suspension see
Appendix 3. After generation the particles should be
neutralized to avoid surface charge. For all tests
described in this document, the concentration should be
no more than 25% of the maximum recommended
concentration limit specified by the manufacturer. For
calibration a suitable set of particle sizes shall be used.
This set should contain at least 5 sizes that cover the
LDL size to at least 80% of the specified maximum size
measurement capability of the LPPD.
NOTE 4: Most of the ISPM sensors are based on light
scattering. The intensity of the scattered light detected by a
photodetector depends on intensity, polarization state, and
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