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SEMI E43-0301 © SEMI 1995 , 2001 18 be oth er radio frequ ency sources an d reflecting or absorbing m aterials in the area. The actual location of the ESD e vent may be a considerable distance from the EMI locator. It w …

SEMI E43-0301 © SEMI 1995, 200117

that can be performed with the equipment operating on-

line, without altering or disturbing its operation.

R4-4 ESD and EMI

R4-4.1 When ESD occurs, the discharge time is

usually 10 nanoseconds or less. Discharging energy in

this short time interval results in the generation of

broadband electromagnetic radiation

, as well as the

heat that damages semiconductor components. This

electromagnetic radiation, especially in the 10 MHz to

2 GHz frequency range, is the EMI that can affect the

operation of production equipment. In addition to ESD

damage to semiconductor devices and reticles, ESD-

caused EMI results in a variety of equipment operating

problems including stoppages, software errors, testing

and calibration inaccuracies, and mishandling causing

physical component damage.

R4-4.2 EMI Locators

R4-4.2.1 When component damage or equipment

problems due to ESD are suspected, it may be useful to

detect the electromagnetic interference (EMI) generated

by the ESD event. This type of testing is both a starting

point for determining that static charge has been

generated, and it is a measurement point to ascertain

that any static control methods have been successful.

EMI locators measure dynamic operating conditions, as

it is usually not necessary to interrupt equipment

operations to make measurements.

R4-4.3 Types of EMI Locators

R4-4.3.1 EMI locators are available in a number of

different forms. In its simplest form, it consists of an

AM radio tuned off station. A popping noise will be

heard when an ESD event occurs. At the most complex

it consists of a wideband (greater than 1 GHz) digital

storage oscilloscope with a set of appropriate antennas,

probes, and software. Measurements of radiated

interference can be made using antennas while probes

can be connected to equipment parts or electronics and

power lines.

R4-4.3.2 An oscilloscope attached to a single antenna

can assist in pinpointing the actual location of the ESD

event.

8, 9, 10, 11

A set of antennas can be used to not only

8 Tonoya, Watanabe and Honda, “Impulsive EMI Effects from ESD

on Raised Floor,” 1994 EOS/ESD Symposium, pp. 164-169, ESD

Association.

9 Takai, Kaneko and Honda, “One of the Methods of Observing ESD

Around Electronic Equipments,” 1996 EOS/ESD Symposium, pp.

186-192, ESD Association.

10 Greason, Bulach and Flatley, “Non-Invasive Detection and

Characterization of ESD Induced Phenomena in Electronic Systems,”

1996 EOS/ESD Symposium, pp. 193-202, ESD Association.

11 Smith, “A New Type of Furniture ESD and Its Implications,” 1993

EOS/ESD Symposium, pp. 3-7, ESD Association.

detect the presence of an ESD event, but to determine

the location of the pulse in 3 dimensions.

12, 13

Using the

same concept as a global positioning system (GPS), the

difference in the arrival times of the signal to multiple

antennas is directly related to the difference in the

distance of each antenna from the ESD source. With the

time deltas and the locations of the antennas known, the

location of the spark can be uniquely identified

employing the appropriate analysis program.

R4-4.3.3 Several other types of EMI locating

equipment are currently in use. Most consist of high

frequency receiving circuitry followed by level

detectors to determine the magnitude of the signal. For

the purpose of detecting EMI from ESD events, the

equipment should have some way of differentiating the

short impulse of EMI from the ESD event from the

continuous high frequency radiation of other EMI

sources. Some instruments contain a counter to total

the number of ESD events above the threshold, or

alarms to indicate when the number of ESD events

exceeds a preset number. This type of instrument can be

placed near a piece of equipment that is suspected of

causing ESD events and left in place to monitor.

R4-4.3.4 Several EMI Locators are battery-operated

handheld devices that can be easily carried around a

facility or placed directly in equipment to check for

ESD events. This allows the Locator to detect signals

that might otherwise be shielded by the equipment’s

cover panels. (Note that EMI shielding is usually an

important part of the design of most production

equipment to prevent radiation from the equipment.

This makes the detection of ESD events outside the

equipment more difficult.) It allows pinpointing of the

location of an ESD event, which can then be correlated

to particular machine operations.

8, 14

R4-4.4 Limitation in Using EMI Locators

R4-4.4.1 One caution needs to be observed when using

EMI locators to detect ESD events that cause

component damage. The signal received by these

devices is generated in areas usually surrounded by

grounded metal components. It may have to pass

through equipment panels and travel some distance

through the air before it reaches the detector. There may

12 Bernier, Croft, and Lowther “ESD Sources Pinpointed by Analysis

of Radio Wave Emissions,” Journal of Electrostatics (44) pp. 149-

157, Nov. 1998, Elsevier Science B.V., P.O. Box 211, 1000 AE

Amsterdam Netherlands.

13 Lin, DeChiaro and Jon, “A Robust ESD Event Locator System

with Event Characterization,” 1997 EOS/ESD Symposium, pp. 88-98,

ESD Association.

14 Fujie, A., “Pinpointing Sources of Static Electricity with EMI

Locator”, Parts 1 and 2, Nikkei Electronics Asia, December 1992 and

January 1993, Nikkei Business Publications Asia Ltd., 533 Hennessy

Road, Causeway Bay, Hong Kong.

SEMI E43-0301 © SEMI 1995, 2001 18

be other radio frequency sources and reflecting or

absorbing materials in the area. The actual location of

the ESD event may be a considerable distance from the

EMI locator. It will be difficult to establish any

correlation between the amplitude of the signal received

by the EMI locator and the energy in the ESD event

that produced the signal. The EMI locator primarily

indicates the occurrence of an ESD event and can be

used to illustrate that a particular static control method

has eliminated it. It should not be assumed that every

ESD event detected results in damage to components or

equipment problems. Additional testing will be needed

to establish that connection.

R4-5 Static Event Detectors

R4-5.1 Static event detectors (SED) are devices that

are installed directly on products to detect the presence

of an ESD event. They may be attached in proximity to

an ESD-sensitive component, connected to the external

device leads, or integrated into the device package.

Typically they detect the current pulse of an ESD event

through an antenna or direct connection to the device

circuitry.

R4-5.2 SEDs can be useful in determining the

occurrence of ESD events in operating production

equipment. The SED has the ability to indicate ESD

events of a known level, aiding in the design and

performance verification of automated equipment.

While costly analysis of failed devices can also provide

this information, correlation to machine operations is

usually difficult. An SED that can be monitored

optically as it passes through operating equipment

provides a convenient method to verify that automated

equipment is not generating levels of static charge that

result in ESD damage.

R4-5.3 Types of SED Devices

R4-5.3.1 In some SED devices, the signal is amplified

and processed to produce a reflectance change in the

built-in Liquid Crystal Display (LCD). The SED is

designed to trip at a predetermined threshold voltage,

detecting ESD transients above the selected amplitude.

Some devices can be reset magnetically or optically

making them reusable.

R4-5.3.2 Other devices use the controllable ESD

damage threshold of metal oxide semiconductor field

effect transistors (MOSFET). The test methodology is

to amplify an ESD transient to create sufficient energy

to destroy the gate oxide. The device may be used until

the specified ESD level is achieved, and then the SED

fails. A similar device is based on the metal oxide

semiconductor capacitor (MOSCAP). The current

leakage through the device significantly increases if the

ESD amplitude is sufficient to damage the MOS

structure. Both of these types of SED must be removed

from where they are installed and require additional

instrumentation to determine their status.

R4-5.3.3 Another type of SED employs the magnetic

fields from a current flow to affect a series of magneto-

optic thin films. The magnetic field from the ESD

current alters the film’s magnetic state and affects the

degree of polarization of visible light reflected from the

film. Varying the distance between the film and the

ESD current-carrying conductor indicates different

thresholds. This SED can be read using a microscope

equipped with a polarizing element and does not need

to be removed from the circuitry to be read. It can be

reset with a magnet.

R4-6 Conclusion

R4-6.1 There is little question that static charge

problems continue to result in significant losses in high

technology manufacturing. Increasingly, static control

methods must be applied in the equipment that

produces the product. It will be important to develop

and utilize a range of diagnostic methods and

measurement equipment for ESD in equipment.

NOTICE: SEMI makes no warranties or

representations as to the suitability of the standards set

forth herein for any particular application. The

determination of the suitability of the standard is solely

the responsibility of the user. Users are cautioned to

refer to manufacture's instructions, product labels,

product data sheets, and other relevant literature,

respecting any materials or equipment mentioned

herein. These standards are subject to change without

notice.

By publications of this standard, Semiconductor

Equipment and Materials International (SEMI) takes no

position respecting the validity of any patent rights or

copyrights asserted in connection with any items

mentioned in this standard. Users of this standard are

expressly advised that determination of any such patent

rights or copyrights, and the risk of infringement of

such rights are entirely their own responsibility.

15 Jackson, Tan, and Boehm, “Magneto Optical Static Event

Detector,” 1998 EOS/ESD Symposium, pp.233-244, ESD

Association.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o

the contents in whole or in part is forbidden without express written

consent of SEMI.

SEMI E45-1101

TEST METHOD FOR THE DETERMINATION OF INORGANIC

CONTAMINATION FROM MINIENVIRONMENTS USING VAPOR PHASE

DECOMPOSITION-TOTAL REFLECTION X-RAY SPECTROSCOPY

(VPD/TXRF), VPD-ATOMIC ABSORPTION SPECTROSCOPY

(VPD/AAS), OR VPD/INDUCTIVELY COUPLED PLASMA-MASS

SPECTROMETRY (VPD/ICP-MS)

This test method was technically approved by the Global Metrics Committee and is the direct responsibility

of the European Equipment Automation Committee. Current edition approved by the North American

Regional Standards Committee on August 27, 2001. Initially available at www.semi.org September 2001; to

be published November 2001. Originally published in 1995; previously published March 2001.

1 Purpose

1.1 This test method provides the analytical procedures

to determine the level of inorganic contamination from

a minienvironment.

2 Scope

2.1 This document relates to inorganic impurities,

which includes metallic contaminants, whether they

occur as atoms, molecules, or particles. The number of

metals to be analyzed is restricted to the four elements

sodium (Na), calcium (Ca), iron (Fe), and copper (Cu)

in order to rapidly characterize minienvironments from

a practicable point of view. While Na, Ca, and Fe

represent one ensemble of highly detrimental impurities

with respect to contamination from human sources

(Na), the environment (Ca), or from equipment and

corrosive effects (Fe), Cu is analyzed due to its

increasing importance in semiconductor manufacturing.

Additionally, they are easily analyzed with sufficiently

low detection limits. It is up to the user of this test

method to quantify additional elements. A list of

suggested polished wafer surface metal contamination

inappropriate to circuits and devices is shown in Table

1 (based on SEMI M1). The inorganic contamination

on silicon wafer surfaces is collected by VPD.

2.2 To quantify Ca and Fe, VPD/TXRF is used due to

its sufficiently low detection limits. Na and Cu are

quantified by VPD/GFAAS or VPD/ICP-MS. All

analytical methods are widely used for the

characterization of surface cleanliness.

2.3 This measurement technique can also be used to

check the influence of certain process steps on

minienvironments.

2.4 This standard does not purport to address safety

issues, if any, associated with its use. It is the

responsibility of the users of this standard to establish

appropriate safety and health practices and determine

the applicability of regulatory limitations prior to use.

Table 1 Suggested Polished Wafer Surface Metal

Contamination Inappropriate to Circuits and

Devices

Element Test Method

Na VPD/(AAS or ICP-MS)

Al VPD/(AAS or ICP-MS)

K VPD/(AAS or ICP-MS or TXRF)

Cr VPD/(AAS or ICP-MS or TXRF)

Fe VPD/(AAS or ICP-MS or TXRF)

Ni VPD/(AAS or ICP-MS or TXRF)

Cu VPD/(AAS or ICP-MS or TXRF)

Zn VPD/(AAS or ICP-MS or TXRF)

Ca VPD/(AAS or ICP-MS or TXRF)

3 Referenced Standards

3.1 SEMI Standards

SEMI C28 — Specifications and Guidelines for

Hydrofluoric Acid

SEMI C35 — Specifications and Guidelines for Nitric

Acid

SEMI E19 — Standard Mechanical Interface (SMIF)

SEMI M1 — Specification for Polished

Monocrystalline Silicon Wafers

3.2 ISO Standards

ISO 9001 — Quality Systems—Model for Quality

Assurance in Design, Development, Production,

Installation, and Servicing

ISO 14644-1 — Cleanrooms and associated

environments – Classification of air cleanliness

1 International Organization for Standardization, ISO Central

Secretariat, 1, rue de Varembé, Case postale 56, CH-1211 Geneva 20,

Switzerland. Website: http://www.iso.ch