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SEMI E114-0302 E © SEMI 2002 2 5 Terminology 5.1 Abbreviations and Acronyms 5.1.1 CVD — Chemical Vapor De position 5.1.2 PVD — Physical Vapor Deposition 5.1.3 VSWR — V oltage Standi ng Wave Ratio 5.2 Definitions of Terms…

SEMI E114-0302

TEST METHOD FOR RF CABLE ASSEMBLIES USED IN

SEMICONDUCTOR PROCESSING EQUIPMENT RF POWER DELIVERY

SYSTEMS

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

of the North American Metrics Committee. Current edition approved by the North American Regional

Standards Committee on March 20, 2002. Initially available at www.semi.org June 2002; to be published

July 2002.

This document was editorially modified in May 2002. A change was made to Section 1.1.

1 Purpose

1.1 The purpose of this document is to define a test

method used to determine the electrical length, power

losses, and characteristic impedance variation of RF

cable assemblies used in RF power delivery systems for

semiconductor processing equipment.

2 Scope

2.1 This document specifies the testing procedures and

test equipment required for the following:

• Determining the electrical length of RF cable

assemblies at the nominal operating frequency in

terms of degrees of phase shift.

• Determining the power dissipation (loss) in the RF

cable assembly at the nominal operating frequency.

• Verifying the characteristic impedance of the RF

cable assembly.

2.2 The primary focus for this specification is

semiconductor processing equipment including, but not

limited to, the following tool types:

• Dry etch equipment,

• Film deposition equipment (CVD and PVD).

2.3 This standard does not address any safety or

performance issues related to RF emissions or electrical

codes (e.g., Underwriter’s Laboratory, Inc. (UL), the

National Electrical Code (NEC



), Federal

Communications Commission (FCC)). It is the

responsibility of the users of this standard to conform to

the appropriate local codes and regulations as applied to

this type of equipment, some of which are covered by

referenced documents.

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.

3 Limitations

3.1 This standard is meant to address RF Cable

Assemblies used in RF systems that primarily operate

in the frequency range of 0.2–100 MHz. It does not

address higher frequency RF systems or microwave

systems.

3.2 This standard assumes that the cable assemblies to

be tested have a nominal characteristic impedance of 50

ohms. This standard can be used with cable assemblies

with a different characteristic impedance if the

appropriate standard termination loads are used.

3.3 International, national, and local codes, regulations

and laws should be consulted to ensure that the

equipment and procedures meet regulatory

requirements in each location.

4 Referenced Standards

4.1 SEMI Standards

SEMI E113 — Specification for Semiconductor

Processing Equipment RF Power Delivery Systems

4.2 IEEE Standards

IEEE-STD-383 — IEEE Standard for Type Test of

Class 1E Electrical Cables, Field Splices, and

Connections for Nuclear Power Generating Stations

4.3 Military Standards

MIL-C-17G — General Specification for Cables, Radio

Frequency, Flexible and Semirigid

MIL-PRF-39012D — General Specification for

Connectors, Coaxial, Radio Frequency

1 Institute of Electrical and Electronics Engineers, IEEE Operations

Center, 445 Hoes Lane, P.O. Box 1331, Piscataway, New Jersey

08855-1331, USA. Telephone: 732.981.0060; Fax: 732.981.1721

2 Available through the Naval Publications and Forms Center, 5801

Tabor Avenue, Philadelphia, PA 19120-5099, USA. Telephone:

215.697.3321

SEMI E114-0302

5 Terminology

5.1 Abbreviations and Acronyms

5.1.1 CVD — Chemical Vapor Deposition

5.1.2 PVD — Physical Vapor Deposition

5.1.3 VSWR — Voltage Standing Wave Ratio

5.2 Definitions of Terms

5.2.1 cable assembly — the section of cable

(transmission line), including the connectors, used to

connect various parts of the RF power delivery system.

5.2.2 device under test (DUT) — the cable assembly

intended to be tested.

5.2.3 electrical length — the length of the cable

assembly at the operating frequency expressed in terms

of degrees, where one wavelength at the nominal

operating frequency is equal to 360 degrees.

5.2.4 half wave resonant frequency — the frequency of

the cable assembly where the electrical length of the

assembly is equal to one half (0.5) of a wavelength.

For example, the half wave resonant frequency of a

cable assembly with an electrical length of 2 meters

would be 74.95 MHz ((c/2-meters)/2).

5.2.5 harmonic frequency — the harmonic frequencies

are defined as integer multiples of the fundamental

frequency. For example, the second harmonic of 13.56

MHz is 27.12 MHz.

5.2.6 quarter wavelength — the length equal to one

quarter of the wavelength at a given frequency, where

the wavelength is equal to the speed of light divided by

the frequency.

5.2.7 S-parameters — the scattering matrix used to

describe a network. The reflection coefficient is the

S11 parameter and the transmission coefficient is the

S21 parameter.

5.2.8 speed of light (c) — the speed of light in free-

space is assumed to be 2.9979 × 10

meters/second.

5.2.9 velocity of propagation (VP) — the velocity of

propagation, VP, is defined as the ratio of the speed of

an electrical signal down a length of cable divided by

the speed in free space. It is the reciprocal of the square

root of the relative dielectric constant of the dielectric

material between the inner and outer conductor of a

coaxial assembly. For example, the VP for cable type

RG-217 is nominally 0.66.

6 Test Apparatus

6.1 RF Vector Network Analyzer — The network

analyzer is used to measure the electrical length and can

also be used to determine the attenuation (power

losses). The network analyzer requires vector

capability so that both the magnitude and phase of the

reflection coefficient and transmission coefficient can

be measured as a function of frequency. The frequency

range shall include the operating frequency and the

quarter-wave resonant frequency of the RF cable

assembly.

6.2 Time Domain Reflectometer (TDR) — The TDR is

used to measure and verify the characteristic impedance

as a function of distance along the transmission line.

6.3 RF Adapters and Terminations — Various adapters

may be necessary to convert between different types of

coaxial connectors (e.g., type N to type HN adapters,

etc.). All adapters used shall have the same nominal

characteristic impedance as the cable assembly to be

tested (DUT), which is typically 50 ohms. For some

measurements, additional coaxial cable assemblies may

be necessary. These cable assemblies, which should

not be confused with the DUT cable assembly, shall be

of the same nominal characteristic impedance as the

DUT cable assembly. Standard terminations will also

be used, such as shorts, opens, and precision 50-ohm

loads.

7 Safety Precautions

7.1 Work should be conducted in accordance with local

safety requirements and test device manufacturer

recommended safety procedures. The tests described in

this document involve using low output power test

instrumentation (typically less than 10 milli-Watt).

7.2 The area immediately surrounding the Test Setup

should be keep free and clear of unnecessary equipment

and materials. Some of the cable assemblies to be

tested may be long and can be trip and lift/weight

hazards.

8 Test Setup for Electrical Length Test

8.1 The Test Setup for the electrical length test consists

of the Network Analyzer, the cable assembly to be

tested (DUT), the appropriate adapter (if any) to

connect the DUT to the network analyzer, and the

appropriate adapter (if any) to connect a coaxial short

circuit termination to the output of the DUT. A

schematic of the Test Setup is shown in Figure 1. Care

should be taken to ensure that the cable assemblies to

be tested do not exceed the vendor specified bending

radius, which is typically 5 times the outer diameter of

the cable.

8.2 Prior to making any measurements, the Network

Analyzer shall be turned on and allowed to warm up

before the testing is to take place. This time allows for

electronics to come to a stable operating condition for

the measurements.

SEMI E114-0302

9 Test Procedure for Determining Electrical

Length

9.1 Two test procedures can be used to determine the

electrical length of a cable assembly. One method

measures it directly at the operating frequency and the

other measures the half-wave resonant frequency to

determine the electrical length. Each method has

advantages, depending on the length of the cable

assembly. Prior to choosing a method, the equivalent

free-space length of the DUT shall be estimated in units

of distance (i.e., meters). This length can be estimated

by dividing the physical length of the DUT by the

velocity of propagation for the particular type of cable.

For example, a DUT made from RG-217 cable with a

physical length of 20 meters and a velocity of

propagation of 0.66 would have an equivalent free-

space length of 30.303 meters (20/0.66 = 30.303). A

flow chart showing the steps for choosing which test

method to use is shown in Figure 2.

9.2 The equivalent free-space length of the DUT shall

be compared with the wavelength of the nominal

operating frequency. Test Method 1 (Section 9.3) shall

be used if the equivalent free-space length is less than a

quarter wavelength of the nominal operating frequency.

Test Method 2 shall be used if it is equal to or greater

than a quarter wavelength of the nominal operating

frequency. For example, if the estimated free-space

length is 3 meters and the nominal operating frequency

is 13.56 MHz (quarter wavelength = 0.25 × c/13.56 ×

= 5.527 meters), then Test Method 1 is

recommended. If the estimated free-space length is 25

meters, then Test Method 2 is recommended.

9.3 Test Method 1 for Determining Electrical Length

9.3.1 This test method measures the phase angle of the

reflection coefficient at the nominal operating

frequency of the DUT when the DUT is terminated by a

short circuit.

9.3.2 Calibrate the Network Analyzer at the desired

operating frequency (e.g., 13.56 MHz). If adapters are

to be used to connect the DUT to the Network Analyzer

and/or to the short circuit termination, then the

calibration shall be made with the adapters in place.

The Network Analyzer shall be calibrated for

measuring the reflection coefficient at test Port 1 (see

Figure 1) using the calibration kit provided with the

Network Analyzer. This measurement is equivalent to

measuring the S11 S-parameter. The calibration shall

be performed at fixed frequency (continuous-wave

operation) using the lowest bandwidth possible

(typically 10 Hz).

9.3.3 After calibration, the cable assembly to be tested

(DUT) shall be attached to Port 1 on the Network

Analyzer. The other end of the DUT shall be

terminated with a short circuit. After all connections

have been visually inspected to ensure proper contact

and the Network Analyzer measurement has stabilized,

the value of the reflection coefficient phase angle shall

be recorded.

9.3.4 If the indicated phase angle of the reflection

coefficient is positive, then the electrical length of the

DUT is equal to one half of the value of the difference

between 180 and the measured phase angle. For

example, if the measure reflection coefficient phase

angle is 120 degrees, then the electrical length is 30

degrees ((180-120)/2).

9.3.5 If the indicated phase angle of the reflection

coefficient is negative, then the electrical length of the

DUT is greater than a quarter wavelength. For this

case, the electrical length is equal to one half of the

absolute value of the measured value of the reflection

coefficient phase angle plus 90. For example, if the

measure reflection coefficient phase angle is -10

degrees, then the electrical length is 95 degrees (90 +

10/2).

9.4 Test Method 2 for Determining Electrical Length

9.4.1 This test method determines the electrical length

of the cable assembly DUT by measuring the half wave

resonant frequency when the DUT is terminated by a

short circuit. For this measurement, the frequency of

the network analyzer is swept. The frequency range of

the sweep is determined from the estimated free-space

length of the DUT.

9.4.2 Estimate the half wave resonant frequency of the

DUT. This frequency is equal to one half of the ratio of

the speed of light divided by the estimated free space

length determined in Section 9.2. For example, if the

estimated free space length of the DUT is 25 meters,

then the estimated half wave resonant frequency is

5.996 MHz (0.5 × c/25).

9.4.3 Calibrate the Network Analyzer. If adapters are

to be used to connect the DUT to the Network Analyzer

and/or to the short circuit termination, then the

calibration shall be made with the adapters in place.

The center frequency of the frequency sweep shall be at

the estimated half wave resonant frequency calculated

in Section 9.4.2, and the frequency span of the sweep

shall be no greater than 10% of the estimated

frequency. For example, if the estimated half wave

resonant frequency is 6.0 MHz, then the frequency span

shall be no greater than 0.6 MHz. The Network

Analyzer shall be calibrated for measuring the

reflection coefficient at test Port 1 (see Figure 1) using

the calibration kit provided with the Network Analyzer.

This measurement is equivalent to measuring the S11

S-parameter. The calibration shall be performed using

the lowest bandwidth possible (typically 10 Hz).