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SEMI S2-0703a E © SEMI 1991, 2004 67 NOTE 1: During design of shielding, th e properties of the radiation should be considered as well as the prop erties of the shielding materials. Brem sstrahlung production should be m…

SEMI S2-0703a

RELATED INFORMATION 7

DOCUMENTATION OF IONIZING RADIATION (SECTION 24 AND

APPENDIX 4) INCLUDING RATIONALE FOR CHANGES

NOTICE: This related information is not an official part of SEMI S2 and was derived from practical application by

task force members. This related information was approved for publication by vote of the responsible committee on

October 21, 1999.

R7-1 International Background Information

R7-1.1 The International Atomic Energy Agency

(IAEA)

Mailing address:

P.O. Box 100

Wagramerstrasse 5

A-1400, Vienna, Austria

Telephone: (+43-1) 2060-0; Facsimile: (+43-1) 20607:

E-mail: Official.Mail@iaea.org

R7-1.2 Basic approaches to radiation protection are

consistent all over the world. The International

Commission on Radiation Protection (ICRP)

recommends that any exposure above the natural

background radiation should be kept as low as

reasonably achievable, but below the individual dose

limits. The total individual dose limit for radiation

workers over 5 years is 100 mSv, and for members of

the general public, is 1 mSv per year. These dose limits

have been established based on a prudent approach by

assuming that there is no threshold dose below which

there would be no effect. This hypothesis proposes that

any additional dose will cause a proportional increase in

the chance of a health effect. This relationship has not

yet been established in the low dose range where the

dose limits have been set.

R7-1.3 The ICRP and the IAEA recommend the

individual dose must be kept as low as reasonably

achievable and consideration must be given to the

presence of other sources that may cause simultaneous

radiation exposure to the same group of the public.

Also, allowance for future sources or practices must be

kept in mind so that the total dose received by an

individual member of the public does not exceed the

dose limit.

R7-2 How Does This Apply to the

Semiconductor Industry?

R7-2.1 A person who can potentially be exposed to

ionizing radiation during the normal course of business

in excess of the annual limit for the general public

should be considered a radiation worker. A radiation

worker is trained to recognize and protect him or

herself from the hazards of ionizing radiation. They

may require exposure monitoring to determine

compliance with local radiation regulations. Radiation

workers are covered by a radiation safety program. A

radiation safety program is an administrative control.

Engineering controls minimize the need for spending

resources in a large scale radiation program.

R7-2.2 The exposure limit for the radiation worker is

20 millisievert (2000 millirem) per year. Based on a 40

hour/week, 50 week/working year basis, the allowable

ionizing radiation emissions are 10 microsieverts/hr

(1.0 millirem/hr). This exposure rate should be

evaluated as an emission rate from any accessible

surface of the equipment (the closest approach to the

surface that the radiation is penetrating).

R7-2.3 Maintenance technicians for radiation machines

should be participants in the radiation safety program as

radiation workers. The equipment should be designed to

allow maintenance technicians access to areas that do

not exceed 10 microsieverts/hr.

R7-2.4 Service technicians for radiation machines

should be participants in their employer’s radiation

safety program as radiation workers. The equipment

should be designed to allow service technicians access

to areas that exceed the 10 microsievert per hour level

when operating, but not while the radiation is present.

R7-2.5 The person operating radiation producing

equipment (Operator) should not be considered a

radiation worker. The emission limit for the operator

accessible areas is recommended to be 20% of the

occupational limit. The maximum allowable ionizing

radiation emissions for operator accessible areas is

recommended to be 2 microsieverts/hr (0.2

millirem/hr). This exposure rate should be evaluated as

an emission rate from any surface foreseeably

accessible by an operator of the equipment, and should

be measured as an instantaneous rate.

R7-3 Definitions

R7-3.1 accessible — a significant part of the whole

body, head, or eyes.

R7-3.2 bremsstrahlung — is radiation produced by

slowing of charged particles. The term means “braking

radiation.”

SEMI S2-0703a

NOTE 1: During design of shielding, the properties of the

radiation should be considered as well as the properties of the

shielding materials. Bremsstrahlung production should be

minimized. Some shielding materials are considered

hazardous materials. These hazardous properties should be

considered and identified.

R7-3.3 radiation machine — means any device

capable of producing ionizing radiation except those

devices with radioactive material as the only source of

radiation.

R7-3.4 radiation producing machine — is a radiation

machine that produces ionizing radiation as a by-

product of the process it uses, e.g., ion implanter or

scanning electron microscope.

R7-3.5 radiation worker — “worker” means an

individual engaged in radiation related work under a

license or certificate of registration issued by the

Agency and controlled by a licensee or registrant, but

does not include the licensee or registrant.

R7-3.6 radioactive material – means any material

(solid, liquid, or gas) that emits ionizing radiation

spontaneously.

R7-3.7 X-ray machine — is a radiation machine that

generates X-rays as a primary function of the

equipment. This category of radiation machine has a

specific limit due to the existence of performance

standards against which the equipment is evaluated.

The equipment must be below this limit to be sold in

some parts of the world.

R7-3.8 X-rays — are produced with electricity and

therefore can be turned off. X-rays seem to be the most

prevalent radiation type in semiconductor

manufacturing equipment. They are produced when

charged particles are slowed or stopped. This slowing

results in “bremsstrahlung.” The majority of the

equipment does not intentionally produce X-rays. This

energy is a by-product of the process.

R7-4 Radioactive Materials

R7-4.1 Gamma radiation is a by-product of atomic

transformations (decay) and is a release of energy from

the nucleus. This radiation energy must be shielded

since there is no off switch.

R7-4.2 Radioactive Materials are controlled by

licensing. There are quantities of certain radioactive

materials that are exempt from regulation. These

sources should be identified.

R7-4.3 External radiation hazards from radioactive

materials include gamma rays. These are controlled and

evaluated much like the X-rays.

R7-4.4 Internal radiation hazards from radioactive

materials include Alpha and Beta particles. Radioactive

materials ingested or inhaled can be metabolized or

damage surrounding tissue. Allowable levels of

airborne radioactivity and radionuclide intakes are

specified in regulations. The objective is still to

maintain all exposure to ionizing radiation (internal and

external) as low as reasonably achievable, but always

less than the allowable regulatory limits.

SEMI S2-0703a

RELATED INFORMATION 8

DOCUMENTATION OF NON-IONIZING RADIATION (SECTION 25 AND

APPENDIX 5) INCLUDING RATIONALE FOR CHANGES

NOTICE: This related information is not an official part of SEMI S2 and was derived from practical application by

task force members. This related information was approved for publication by vote of the responsible committee on

October 21, 1999.

R8-1 The user of this table is responsible for obtaining

the current revision of the standards cited for

Occupational Exposure Limits (OEL).

R8-2 The emission values in Appendix 5 that are not to

be exceeded were chosen based on a review of all

known international standards as well as a

consideration for best available control technology (i.e.,

lowest values currently achievable for each radiation

type). Where a general public limit existed, 20% of this

value was selected. Where there was no public limit,

the value selected is generally 20% of the OEL value

(instantaneous field strength measurement peak). The

latter case would have the occupational and general

public levels the same. Where there was an

occupational exposure limit specified in a standard, the

maintenance emission limit was set at 20% of this level.

R8-3 Most health standards differentiate between

“occupational” and “general public” exposure criteria.

IEEE C95.1 differentiates between “controlled access”

and “uncontrolled access” exposures. According to

C95.1 “controlled access” environments are those

where “locations where there is exposure that may be

incurred by persons who are aware of the potential for

exposure as a concomitant of employment, by other

cognizant persons, or as the incidental result of

transient passage through areas where analysis shows

the exposure levels may be above those shown in Table

2 but do not exceed those of Table 1, and where the

induced currents may exceed the values in Table 2, Part

B, but do not exceed the values of Table 1, Part B.”

According to C95.1, “uncontrolled access”

environments are “locations where there is the exposure

of individuals who have no knowledge or control of

their exposure. The exposure may occur in living

quarters or workplaces where there are no expectations

that the exposure levels may exceed those shown in

Table 2 and where induced currents do not exceed those

in Table 2, Part B.” Task force members advise that

C95.1 “controlled access” and other “occupational

exposure” standards should be applied to personnel

performing maintenance and service of equipment and

that “uncontrolled access” or other “general public”

standards should be applied to equipment operators

during routine work and to other locations. These IEEE

definitions are particularly relevant to broadcast

facilities as well as normal industrial environments such

as fabs. Task force members recommend that

uncontrolled access limits be applied to fetal exposure.

R8-4 As with the rationale in the Ionizing section, the

operator is considered a member of the general public

or to be in an uncontrolled area. Maintenance or service

technicians should be trained to know how to control

the hazardous energy and protect themselves from the

hazard and its adverse effects.

R8-5 References

1. 1996 TLVs and BEIs Threshold Limit Values for

Chemical Substances and Physical Agents Biological

Exposure Indices, ACGIH, Cincinnati, OH

2. Guidelines on Limits of Exposure to Broad-Band

Incoherent Optical Radiation (0.38 to 3 M), Health

Physics Vol. 73, No. 3 (September), pp.539-554, 1997

3. ICNIRP 1994 “Guidelines on Limits of Exposure

to Static Magnetic Fields”, Health Physics Vol 66 (1)

(January), pp. 100-106, 1994

4. IEEE Standard for Safety Levels with Respect to

Human Exposure to Radio Frequency Electromagnetic

Fields, 3 kHz to 300 GHz, C95.1-1991, Piscataway,

New Jersey

5. Interim Guidelines on the Limits of Exposure to

50/60 Hz Electric and Magnetic Fields, IRPA/ICNIRP

Guidelines, Health Physics Vol. 58, No. 1(January), pp.

113-122, 1990