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SEMI E129-1103 © SEMI 2003 25 RELATED INFORMATION 3 MEASURING ELECTROMAGNETIC INTERFERENCE FROM ESD NOTICE: The m aterial contained i n this rela ted inform ation is not a n official part of SEMI E129 and is not intended…
SEMI E129-1103 © SEMI 2003 24
ESD TR02 — High Resistance Ohmmeters – Voltage
Measurements
ESD TR03 — Glove & Finger Cots
ESD TR05 — Consideration for Developing ESD
Garment Specifications
ESD TR06 — Static Electricity Hazards of
Triboelectrically Charged Garments
ESD TR11 — Electrostatic Guidelines and
Considerations for Cleanrooms and Clean
Manufacturing
R2-12.4 Federal Standards
FED-STD-101/4046 — Electrostatic Properties of
Materials
FED-STD-101/2065 — Puncture Resistance and
Elongation Test (1/8 Inch Radius Probe Method)
R2-12.5 IDEMA Documents
IDEMA M7 — Organic Contamination as Nonvolatile
Residue (NVR)
IDEMA M9 — Particulate Contamination Test
Methods for Hard Disk Drive Components
IDEMA M11 — General Outgas Test Procedure by
Dynamic Headspace Analysis
IDEMA M12 — Measurement of Extractable
/Leachable Cation Contamination Levels on Drive
Components by Ion Chromatography (IC)
R2-12.6 IEC Documents
IEC EN 61340-5-1 — Electrostatics
– Part 5.1:
Protection of electronic devices from electrostatic
phenomena — General Requirements.
IEC EN 61340-5-2 — Electrostatics – Part 5.2:
Protection of electronic devices from electrostatic
phenomena – Users’ Guide – Elements of a Static
Control Program
R2-12.7 Other Documents
ANSI IEEE STD 142 — IEEE Recommended Practice
for Grounding of Industrial and Commercial Power
Systems
ANSI NFPA 70 — National Electrical Code
ARP 598 — The Determination of Particulate
Contamination in Liquids by the Particle Count Method
ISO 14644 — Cleanrooms and Associated Controlled
Environments
NASA KSC-C-123 — Specification for Surface
Cleanliness of Fluid Systems
IEST-STD-CC1246D — Product Cleanliness Levels
and Contamination Control Program
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
R2-13 Acknowledgement
Contributed by David E. Swenson, Affinity Static
Control Consulting, 2609 Quanah Drive, Round Rock,
TX 78681
email: static2@swbell.net
SEMI E129-1103 © SEMI 2003 25
RELATED INFORMATION 3
MEASURING ELECTROMAGNETIC INTERFERENCE FROM ESD
NOTICE: The material contained in this related information is not an official part of SEMI E129 and is not
intended to modify or supersede the guide in any way. These notes are provided as a source of information to aid in
the application of the guide, and are to be considered reference material. Determination of the suitability of the
material is solely the responsibility of the user. This related information was approved by full letter ballot
procedures on September 3, 2003.
R3-1 Background
R3-1.1 Electrostatic discharges (ESD events) generate
strong electromagnetic fields that cause undesirable
behavior of electronics equipment generally by
inducing extraneous voltages and currents into its
circuits. There are many other sources of
electromagnetic interference (EMI) in the
semiconductor-manufacturing environment that also
cause similar effects. EMI is propagated via different
means such as air, cables and even imperfectly installed
grounding networks.
R3-1.2 There are several regional and international
standards regulating EMI susceptibility and parasitic
emission of electronics products. Compliance of
equipment with those standards is not a guarantee of
complete immunity to EMI for several reasons, among
which are:
• EMI conditions in semiconductor manufacturing
environments often exceed the limits set forth by
those standards.
• EMI performance of equipment can be
substantially affected by installation, although
EMC compliance testing does not take this into
account.
• Interconnection of tools in the actual production
environment creates a network of tools, which has
its own EMI properties that are never tested during
product design and approval cycle.
There are neither guidelines nor regulations at the
moment to guide EMI-conscious design of facilities or
to properly maintain them in that regard. It would be
beneficial to provide (at minimum) guidelines to
cleanroom designers and maintenance personnel to
assist them in implementing good EMI practices in their
facilities.
R3-2 EMI GENERATION
R3-2.1 Controlling EMI generation is a key component
in EMI management. There are several types of
generators of electromagnetic emission that can
eventually cause EMI.
• ESD events (discharges)
• Parasitic emission from equipment
• Intentional emission from equipment that uses
electromagnetic fields as a part of the process
R3-2.2 An ESD event is characterized by a very rapid
transfer of electric charges. As a result, a very fast
transient electromagnetic field is generated. The effect
on the equipment is determined not only by the voltage
that was discharged by the ESD event, but also by the
charge that was dissipated during the event and the
properties of contact. Another important parameter in
assessing EMI impact of ESD events is the propagating
properties of the discharging parts. More effective
antennas lead to a higher magnitude of electromagnetic
field.
R3-2.3 Parasitic emissions from equipment are a side
product of normal operation of equipment. Though
FCC, CE or similar regulations tightly control parasitic
emission, in actual installations these emissions are
often higher than expected. This is often attributed to
high tool densities, extra long cabling, partially engaged
connectors, and often-open covers that are supposed to
attenuate electromagnetic emission from these cables.
R3-2.4 Intentional radiation generated by some types
of tools causes substantial EMI as a part of normal
operation. Examples include CVD tools and ion
implanters.
R3-2.5 EMI Propagation
R3-2.5.1 Controlling the propagation path is another
key component in EMI management. Electromagnetic
field propagation paths include:
• Radiated – via air
• Conducted – via cables and wires
• Combined – an example of such is EMI picked up
from the air by a cable or a wire and carried into
equipment as a conducted emission.
R3-2.5.2 Poor grounding and power distribution
networks provide paths for EMI to propagate from one
tool to another. It is not uncommon to witness EMI
from one corner of a cleanroom to manifest itself in
another, distant corner.
SEMI E129-1103 © SEMI 2003 26
R3-2.6 The following categories of EMI are
recommended for consideration in setting limits:
• Continuous radiated emission
• Continuous conducted emission
• Transient radiated emission
• Transient conducted emission
• EMI levels on the ground and on the power lines
It is anticipated that FCC and CE regulations would be
considered as one of the factors in setting the limits, but
surveys of the actual environment in the factory will
also need to be considered.
R3-3 EMI Effect on Equipment
R3-3.1 There are three main ways EMI can affect
equipment:
R3-3.1.1 Destruction — The signals created by EMI in
the circuit exceed the breakdown threshold of
components, which leads to their destruction. This is
especially relevant to conducted EMI.
R3-3.1.2 Malfunction — EMI injects pseudo-legitimate
signals into the circuit, which leads to that circuit’s
malfunction. Such malfunction may range from
complete lockup to unwanted operation of the tool.
This is frequently misdiagnosed as software errors.
Often, this type of malfunction involves several tools
connected together.
R3-3.1.3 False Sensor Readings — Signals induced by
EMI add to the signals coming from sensors and leads
equipment to misread sensor data.
R3-4 EMI Measurements
R3-4.1 Measuring EMI can be a very effective tool in
ESD management in the cleanroom, as EMI is a
signature that ESD events are occurring. The following
are some of the parameters and test methods that are
recommended to be checked during such audits.
R3-4.2 Radiated EMI Levels Near Equipment — Both
continuous and transient (peak) should be measured and
identified.
R3-4.3 Conducted EMI on Cables — Both continuous
and transient (peak). Due to practical considerations,
an acceptable method will have to be devised to
measure conducted EMI on hard-to-reach cables.
R3-4.4 Electromagnetic emissions generated by ESD
events have unique properties. These include:
• Very short rise time – as short as hundreds of
picoseconds,
• Very short duration – from a few nanoseconds to
several hundred nanoseconds,
• Very broad frequency range (up to several GHz),
and
• Often high magnitude.
There are several types of equipment available to detect
and measure electromagnetic fields from ESD events.
R3-4.5 AM Radio
R3-4.5.1 Since electromagnetic fields from ESD events
are manifested as short bursts of energy, they may be
detected by a conventional AM radio tuned to a
frequency free of radio stations. The radio produces
“clicks” when it detects ESD events. The AM radio has
difficulties picking up weak and very rapid discharges,
and in industrial environments it is likely to pick up
noise from normal equipment operation.
R3-4.6 EMI Locators
R3-4.6.1 Several types of EMI Locators are available,
including portable handheld types and larger
instruments. The simplest type provides both a visual
and audible indication of the transient EMI from an
ESD event. Although it can discriminate between two
sensitivity levels for EMI, it gives no information
regarding the magnitude of the ESD event that
produced the EMI. Their frequency response is also
limited to approximately 150 MHz and they may miss
the faster EMI signals.
R3-4.6.2 A second type of EMI Locator is a general-
purpose electromagnetic field strength meter with a
bandwidth (up to 2 GHz) to measure EMI from ESD
events. It has a directional antenna to help identify
sources of emission, and provides outputs for emission
levels and the counting of ESD events, including time
stamping. This can be very useful in correlating ESD
events with equipment malfunctions. Some units will
also provide discrimination of multiple ESD events and
provide output signals directly to a computer or factory
management system.
R3-4.7 High-Speed Storage Oscilloscopes
R3-4.7.1 An oscilloscope equipped with proper
antennae provides the most comprehensive information
about waveform and magnitude of EMI caused by ESD
events. The minimum requirements for an oscilloscope
used for this purpose are a 500-MHz bandwidth and a
5-gigasamples/s sampling rate. Instruments with lesser
performance specifications would either miss or
misinterpret EMI parameters.
R3-4.7.2 The use of a high-speed oscilloscope should
be accompanied by the use of a proper antenna for
receiving the electromagnetic fields. For time domain