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SEMI S2-0703a E © SEMI 1991, 2004 65 RELATED INFORMATION 6 CONTINUOUS HAZARDOUS GAS DETECTION NOTICE : This rel ated information i s not an of ficial part of SEMI S2 and was de rived from practical application by task fo…

SEMI S2-0703a

DESIGN EXAMPLE (continued; refer to Figure R5-1 for illustration of example)

Disclaimer: the calculations below are not a complete seismic analysis. A complete analysis might also include such

things as: stress distribution through a multiple-fastener connection; prying action; bearing stress; simultaneous

combined stresses on the fasteners; and a review of weld geometry. A complete seismic analysis should be done by

a qualified engineer.

R5-4 Calculation of Lateral Force

R5-4.1 Lateral force on each leg is equal to F

/# of legs = F

R5-4.2 The lateral force acts as shear on the floor anchor fasteners and shear or tensile loading on the equipment

anchor fasteners depending upon orientation. The actual reactions of the fasteners should be calculated by a

qualified engineer.

R5-5 Calculation of Overturning Force

R5-5.1 Sum the moments of the reactions on the system about line through the legs A and B:

(CW =+) M

= 0 = F

(h) – 0.85W

) –2R(L

)= 0

(h) – 0.85W

)

R = _________________

= 0.94W

(0.94h – 0.85L

)

R = _________________

If 0.94h

 0.85L

, then there is a tension reaction, R, at the two anchors, to resist overturning of system.

Example:

L1 = 50 inch

L2 = 20 inch

h= 36

W = 5000 lbs

Lateral force

= Fp/4 = 0.94(5000)/4 = 1175

(0.94h – 0.85L

)

Overturning force

= R =_________________

= 5000 (0.94(36) – 0.85(20))

_____________________

2(50)

R = 842 lbs

SEMI S2-0703a

RELATED INFORMATION 6

CONTINUOUS HAZARDOUS GAS DETECTION

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.

R6-1 Scope — This related information provides a list

of gases for which continuous monitoring is

recommended, and another list of gases for which

continuous monitoring may be recommended

depending on variables listed below. The list is not

intended to be exhaustive (gases that do not appear on

the list may need to be continuously monitored).

R6-2 Intent — The purpose of this Related Information

is to provide equipment manufacturers with an

indication as to what gases are currently continuously

monitored by device manufacturers, as guidance for

when it may be appropriate to provide an interface (see

also Section 23).

R6-3 The following variables should be taken into

consideration when determining the necessity for

continuous monitoring:

 Chemical toxicity,

 Warning property/OEL ratio,

 Delivery pressure,

 LEL,

 Flow rate of potential leak,

 Engineering controls in place, and

 Concentration.

Monitoring Recommended Monitoring May Be

Recommended

ammonia

arsine

boron trifluoride

bromine

carbon dioxide

carbon monoxide

carbon tetrabromide

chlorine

diborane

dichlorosilane

disilane

fluorine

germane

germanium tetrafluoride

flammable mixtures

containing hydrogen

hydrogen bromide

hydrogen chloride

hydrogen fluoride

hydrogen selenide

hydrogen sulfide

Methane

methyl chloride

methyl fluoride

nitric oxide

nitrogen dioxide

nitrous oxide

nitrogen trifluoride

ozone

phosphine

silane

silicon tetrachloride

silicon tetrafluoride

sulfur dioxide

trichlorosilane

tungsten hexafluoride

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.”