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SEMI E43-0301 © SEMI 1995 , 2001 6 10.3 Demonstrating Ability to Meas u r e Examp le Item(s) Acceptably — T he certifier w ill have charged/uncharged example(s ) of items/objects for m eas urement of static field(s) by c…

SEMI E43-0301 © SEMI 1995, 20015

9.2.3 Measurement Limitations — Measurements

made to this guide are only valid for surfaces that are

flat to a radius of 1.5 times the measurement distance

from a point directly below the sensor head. For

surfaces that are not flat, measurements should be made

by moving the sensor over the surface such that the

specified measurement distance is maintained as closely

as possible. These measurements may only be stated as

a range, with rounding as applicable to the meter's

measurement range according to Section 9.2.2. See

Figure 4, Example of a Survey of a Carrier of

Semiconductor Wafers. See Related Information 2 for

notes on test methods environment and measurements.

9.3 Electrostatic Voltmeter Measurements — Refer to

Figure 4.

9.3.1 Verifying the Voltmeter — Verify the

performance of the voltmeter as in Section 7 above.

Check/reset the zero periodically per manufacturer's

instructions. Assure that the voltmeter and operator are

grounded.

9.3.2 Selecting the Voltmeter — Select an electrostatic

voltmeter with a measurement range consistent with the

anticipated levels of charge on the objects to be

measured. The selection of too high a measurement

range will sacrifice voltage resolution, while selection

of too low a range will cause out-of-range operation

(saturation).

9.3.2.1 To measure moving objects, select an

electrostatic voltmeter with a response speed fast

enough to detect the objects when they are moving past

the electrostatic voltmeter probe at the highest

anticipated velocity.

9.3.2.2 Select a side- or end-viewing probe for the

electrostatic voltmeter as is best suited to view the

target object or surface when the probe is installed in an

apparatus.

9.3.3 Measurements — Position the probe in front of

the surface to be measured. Best results are obtained

when the probe is placed less than two (probe) aperture

diameters from the object or surface to be measured.

At these closer spacings, the effects of extraneous fields

are minimized.

9.3.3.1 To resolve a small surface area, the distance

between the probe and the surface-under-measurement

must be less than 1/5

of the diameter of the surface

area to be measured. At wider spacings the surface area

resolved by the probe will exceed the surface area of

interest, and measurement accuracy may be reduced

together with the possibility of introducing effects of

extraneous fields to the measurement.

9.3.4 Measurement Limitations — Voltage levels on

isolated conductors can be measured. Insulators do not

have a uniform surface charge distribution. Therefore,

it is considered that voltage levels measured on

insulators indicate an electrostatic field strength in a

particular area.

9.4 Electrometer Measurements — Measuring with an

Electrometer is very similar to measuring with any

other voltmeter or multimeter.

9.4.1 Connect the “common” terminal of the

electrometer through a test lead to the reference plane

or ground. Connect the “hot” or signal lead to the object

or test point of interest. Some electrometer

measurements will use a separate wire or shield

connected to the electrical ground or a guard ring.

Connect this as recommended by the manufacturer of

the equipment.

9.4.2 The major difference between the ordinary

voltmeter and the electrometer is the orders of

magnitude higher input impedance of the electrometer.

An electrometer will therefore pick up voltage signals

produced by stray electric fields, potentials associated

with noise currents, and artifacts caused by intentional

or unintentional ionization of the ambient air when

measuring high voltages. An electrometer can, for

example, be used to measure the triboelectric and the

piezoelectric properties of a piece of coaxial cable:

connect the cable under test to the electrometer, and

flex it or tap on it with a finger. The voltages induced

on the center conductor can be measured by the

electrometer.

10 Certification

10.1 Certification to survey areas to this guide is for

the person doing the certification (certifier) to assure

that the person being certified (certifyee) can calibrate

the meter and make acceptable measurement of known

static field(s) per Section 7 and applicable example(s)

per Section 9. The certifier shall be someone qualified

by education and/or training to calibrate and make

measurements with the equipment called out in this

guide or someone previously certified. The ESD

Association conducts such training programs and the

National Association of Radio and Television

Engineers (NARTE) administers an ESD Engineer and

ESD technician certification program.

10.2 Demonstrating Ability to Verify the Performance

of the Meter Against Known Source — The certifyee

shall charge the test plate, zero the meter, and perform

the measurement a minimum of two times per Section

7; record values per Section 11. Readings obtained shall

be within 5% of expected values.

SEMI E43-0301 © SEMI 1995, 2001 6

10.3 Demonstrating Ability to Measure Example Item(s) Acceptably — The certifier will have charged/uncharged

example(s) of items/objects for measurement of static field(s) by certifyee(s) a minimum of two times per Section 9;

record values per Section 11.

10.4 Certifying — Readings obtained per Section 10.2 shall be within 12% of expected values and methodology of

obtaining readings shall be acceptable per certifier observation(s). A permanent record of certification is realized by

certifyee when certifier signs record sheet(s) for file in personnel records and/or when certifier issues a certificate.

Refer to Section R1-3.

11 Documentation

11.1 Meter calibration check(s), benchmark or laboratory measurements, items/areas surveys, and/or any other

electrostatic field measurements should be recorded in permanent records. Recorded are initial reading,

second/validation reading, and any subsequent readings taken to acceptable range/bound levels observed. Record

sheet(s) should show meter used, area (name), location, date, and items listed opposite readings, name of person

who took readings, and space for comments.

Charging

Source

STEP 1

Charge

Capacitor

Charging

Source

STEP 2

Disconnect

Charging

Source from

Capacitor

Coulombmeter

STEP 3

Connect

Coulombmeter

to Capacitor

Figure 1

Verifying Performance of the Coulombmeter

A) Connect meter directly to charged plate ground reference.

B) Meter approximately 2.54 cm and parallel to charge plate.

C) Meter reading should be within 5% of voltage applied to plate.

D) Assure that both the meter and the operator are properly grounded.

Meter

Field emanating from charge plate

Plate

Ground Plane

Insulators

Charged Plate monitor

or power supply

Figure 2

Fieldmeter and Voltmeter Verification Check

Coulombmeter

Place object into

Faraday

enclosure.

Faraday Enclosure

Figure 3

Measurement With a Coulombmeter and Faraday Enclosure