SEMI E16-90 (Reapproved 0699) GUIDELINE FOR DETERMINING.pdf

SEMI E16-90 (Reapproved 0699
GUIDELINE FOR DETERMINNG AND DESCRBING MASS FLOW
CONTROLLER LEAK RATES
This Guideline was technically approved by the Global Facilities Committee and is the direct responsibilit
of the North American Facilities Commillee. Current edition approved by the North American Regional
Standards Committcc on Dcccmbcr 18, 1998. Initially availablc on SEMI Onlinc Fcbruary 1999 to be
published Junc 1999. Originally published in 1990; prcviously published in 199
Editorial changes were madc to Scctions 4.2.2, 4.3.1, and 4.3.2
atm-cc/s (H
atmospheric cubic centimeters per
1 Purpose
1. 1 The purpose of this guideline is to establish a NOTE 1: The Pascal(Ipa=1 N/m, is defined as the pressure
worldwide means
g
unit of the international unit system Sl. Therefore, the SI unit
measuring leak rates of mass flow controllers. The leak above are prefered. Amm-cc/s is acceptable, as it is widely
rstem Is
maintaining product quality and performance. This
guideline is intended to prevent confusion and 3. 2. 1 The mass spectrometer helium leak detector"is
misunderstanding between manufacturers and users. In
lly used for leak
d med
particular, it distinguishes between mechanical and level vacuum apparatus. Units of sccs, Torr-l/s. and m
diffusion leak rates
bar-l/s, have been used in the past but are not
encouraged. Reference materials include MIL STD
2 Scope
202E.C-1
2. 1 This guideline contains definitions of terms and 3.3 Measured Leak Rale The leak rate of a given
orocedures for determining the Leak Rates of mass flow system measured under specified conditions and
controllers as used in the semiconductor industry
employing a specified test gas(helium). For the
urposes of comparison with rates determined by other
3 Definitions
methods of testing. measured leak rates must be
converted to equivalent standard leak rates
3. 1 Leak-a path or paths in a sealed system which
will pass helium when a partial pressure differential 3.4 ens nvy (Minimim Detectable Leak Rate)
exists. A partial pressure differential can exist for The smallest standard leak rate that an instrument,
helium even though a total gas pressure differential may method or system is capable of measuring under
not exist. There are two major leak mechanisms, a specified conditions
mechanical passage or a material through which gas can 3.5 For the purposes of this document, the Measured
diffuse or permeate. In a real system, a leak may have Leak Rate shall be corrected to Standard Leak Rate b
both mechanisms operating in parallel
multiplying by the ratio of 101.32 kpa to the absolute
3.1.1 A mechanical leak may be a physical crack, pit, value of the pressurizing helium unless otherwise called
ratch or other imperfection in a sealing surface,
for by the MFC specifications
contamination or debris on the seals. A diffusion or
Measure Leak Rate x 10132 kp
permeation leak is caused by the movement of helium
Standard Leak Rate
through gaskets, O-rings, polymers, or other materials
He Actual Pressure
through which helium can diffuse
3.2 Standard Leak Rate- The qu antity of helium at
4 Testing
25C and 101.3 kpa (760 Torr )flowing through a leak 4.1 General Requirements
when the high pressure side is a