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SEMI F64-0701 © SEMI 2001 2 5.2.10 P 1 — inlet pressure 5.2.11 P 2 — outlet pressure 5.2.12 PC A — pressure coeff icie nt of a c tu al flow per pressure ch a nge at a set point. 5.2.13 PC O — pressure coeff icie nt of i …
SEMI F64-0701 © SEMI 20011
SEMI F64-0701
TEST METHOD FOR DETERMINING PRESSURE EFFECTS ON
INDICATED AND ACTUAL FLOW FOR MASS FLOW CONTROLLERS
This specification was technically approved by the Global Facilities Committee and is the direct
responsibility of the North American Facilities Committee. Current edition approved by the North American
Facilities Committee on April 30, 2001. Initially available at www.semi.org May 2001; to be published July
2001.
1 Purpose
1.1 The purpose of this document is to define a
method for characterizing a MFC being considered for
installation into a gas distribution system. This method
will quantify the effect of transient and steady state
inlet and outlet pressure conditions on the performance
of the MFC.
1.2 This document provides a com mon basis for
communication between manufacturers and users
regarding testing and describing MFC pressure effects.
2 Scope
2.1 This test method measures the upstream (inlet) and
downstream (outlet) transient pressure influences on
indicated and actual flow.
2.2 This test method yields the res ults of actual output
flow versus MFC set-point and indicated flow as
influenced by steady state inlet pressure.
2.3 This test method applies to MF Cs with maximum
flow ranges of up to 1000 sccm.
NOTE 1: Due to the higher sensitivity of lower flow rate
MFC’s when pressure transients occur, the flow range for this
document is limited to 1000 sccm.
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 health practices and determine the
applicability or regulatory limitations prior to use.
3 Limitations
3.1 This test method is limited to a nalyzing the effect
of pressure on performance characteristics of MFCs and
is not a verification of the state of calibration, linearity,
or accuracy.
3.2 This test method does not address pressures in
excess of the DUT’s maximum working pressure as
specified by the manufacturer.
3.3 This test method is limited to r easonable pressure
transients; i.e., fluctuations that are otherwise tolerated
by common semiconductor process equipment.
3.4 This test method does not address operational
influences outside of the manufacturer’s published
limitations.
3.5 This test method does not addr ess the effects of
interruptions of the gas supply.
4 Referenced Standards
4.1 None.
5 Terminology
5.1 Definitions
5.1.1 actual flow — flow as indicate d by flow
standard (see Figures 1 and 2).
5.1.2 indicated flow — flow as indic ated by the device
under test (DUT).
5.1.3 ramp — constant rate of change in pressure
(dp/dt = k).
5.1.4 stability — the ability of a con dition to exhibit
only natural, random variation in absence of unnatural,
assignable cause variation.
5.1.5 step change — an exponential step in pressure
with a time constant of one second or less.
5.2 Abbreviations and Acronyms
5.2.1
δ
M — deviation of mass of material relative to
steady-state mass delivery.
5.2.2
∆
P — change in pressure with respect to time
5.2.3
∆
Q — steady state deviation of actual flow
during inlet pressure ramp from that while inlet
pressure is constant.
5.2.4
δ
Q
-
— maximum negative dev iation of actual
flow from nominal.
5.2.5
δ
Q
+
— maximum positive dev iation of actual
flow from nominal.
5.2.6
τ
— pneumatic time constant
5.2.7 DUT — device under test
5.2.8 MFC — mass flow controller
5.2.9 MV — metering valve
SEMI F64-0701 © SEMI 2001 2
5.2.10 P
1
— inlet pressure
5.2.11 P
2
— outlet pressure
5.2.12 PC
A
— pressure coefficient of actual flow per
pressure change at a set point.
5.2.13 PC
O
— pressure coefficient of indicated flow
per pressure change at zero flow.
5.2.14 PC
S
— pressure coefficient of span flow per
pressure change.
5.2.15 Psia — pounds per square inch absolute
5.2.16 Psig — pounds per square inch gauge
5.2.17 Q
A
— actual flow
5.2.18 Q
FS
— rated full scale flow
5.2.19 Q
I
— indicated flow
5.2.20 Q
N
— nominal actual flow dur ing steady state
conditions.
5.2.21 Q
R
— steady state actual flow while inlet
pressure is being ramped.
5.2.22 Q
SP
— set-point flow
5.2.23 T — time
5.2.24 t
f
— time when Q
A
is within 0 .5% of reading of
Q
N.
5.2.25 t
o
— time when pressure transi ent is initiated.
5.2.26 t
s
— settling time to Q
N
5.2.27 v — voltage
5.2.28 V
eq
— equivalent internal cont rol volume of the
DUT.
5.2.29 V
ip
— valve, pump isolation
6 Summary of Test Method
6.1 Inlet Pressure Step and Ramp Change — The
effects of fast-step and slow-ramp changes to the
pressure on actual flow out of the MFC is observed.
See Figures 6 and 7.
6.2 Inlet Pressure Effect Steady St ate — The effects of
a pressure increase/decrease on actual flow is observed
once the increase/decrease has reached steady state.
See Figure 8.
6.3 Outlet Pressure Step Change — The effects of an
outlet pressure change on actual flow is observed. See
Figure 9.
6.4 Crosstalk Pressure Effect – Th e effects of pressure
changes due to switching multiple flow devices on the
same gas line. See Figure 11.
7 Interferences
7.1 The accuracy rating of the mea suring equipment
shall be superior to that of the DUT. Preferably the
measuring equipment will have an accuracy that is four
times better than the DUT. Calibration equipment must
have a valid calibration certificate.
7.2 Take care when using test instruments with a
specified accuracy expressed in percent of full scale as
the accuracy is limited at lower percentages.
7.3 Installation effects on the flow should be
minimized.
7.4 Verify electrical signals directly at the DUT
connector to ensure that the signals at the DUT and
standard agree with the signals at the data recording
equipment.
7.5 All electrical measurements sh ould be read on
devices with at least 4.5 digits of resolution. These
devices must have valid calibration certifications.
7.6 The results of this test method depend on the
accuracy and repeatability of the pressure measurement
devices used in the test system. Take care to stay
within the specified pressure ranges of these devices
and verify their accuracy prior to and following MFC
evaluation activities.
7.7 The cleanliness level of the tes t gas should be
compatible with the DUT. The minimum requirement
placed on the test gas is that it be free of contamination
that could influence the operational characteristics of
the test article and instruments.
7.8 The test gas source and deliver y system must be
capable of satisfying the test volume flow rate at a
constant pressure ± 0.7 kPa (± 0.1 psi).
7.9 The ambient temperature shou ld be held to 22°C
±2°C for the duration of each analysis.
8 Significance and Use
8.1 The significance of the stabilit y calculations in this
method is to allow the MFC user to assess the transient
pressure effects on the DUT. In application, this
method will provide a consideration affecting gas
system designs and MFC selection.
9 Apparatus
9.1 Equipment Required for Methods A–1 and A–2
9.1.1 Inlet test gas filter
9.1.2 Shutoff valve (qty 2).
9.1.3 Pressure transducers, available range 0–446 kPa
(0–50 psig), with measurement accuracy of ± 0.2% and
time constant less than 20 msec (qty 2).
SEMI F64-0701 © SEMI 20013
9.1.4 Dome-loaded pressure control, or other device
capable of producing specified pressure transients.
9.1.5 Flow standard, with time constant less than 20
msec and with full scale that is 200% of the DUT’s full
scale, accurate to 1% of full scale, linear to 0.5% of full
scale, and capable of resolving to 0.2% of full scale.
9.1.6 Data acquisition system measu res the electrical
signals from the device under test. The data acquisition
system may also read the signals from the flow
standard, record test data and control the test sequence.
9.2 Equipment Required for Method B
9.2.1 Inlet test gas filter.
9.2.2 Shutoff valve (qty 2).
9.2.3 Pressure transducer, available range 0–791 kPa
(0–100 psig), with measurement accuracy of ± 0.1%
and time constant less than 20 msec.
9.2.4 Two-stage pressure regulator, capable of 0–690
kPa (100 psia) control.
9.2.5 Flow standard, with full scale that is at least
120% of the DUT’s full scale, accurate to 1% of full
scale, linear to 0.5% of full scale, and capable of
resolving to 0.2% of full scale.
9.2.6 Data acquisition system measu res the electrical
signals from the device under test. The data acquisition
system may also read the signals from the flow
standard, record test data and control the test sequence.
9.3 Equipment Required for Method C
9.3.1 Inlet test gas filter.
9.3.2 Manual metering valve.
9.3.3 Pressure transducer, available range 0–446 kPa
(0–50 psig), with measurement accuracy of ± 0.2% and
time constant less than 20 msec.
9.3.4 Pressure transducer, 0–101.325 kPa ± 1% and
with time constant less than 20 msec (qty 1).
9.3.5 Shutoff valves (qty 2).
9.3.6 Isolation valve (qty 1).
9.3.7 Vacuum pump, with pumping speed of at least
30 lpm, with throttling and isolation valve.
9.3.8 Flow standard, with time constant less than 20
msec and with full scale that is 200% of DUT full scale
accurate to 1% of full scale, linear to 0.5% of full scale,
and capable of resolving to 0.2% of full scale.
9.3.9 Data acquisition system measu res the electrical
signals from the device under test. The data acquisition
system may also read the signals from the flow
standard, record test data and control the test sequence.
9.4 Equipment Required for method D
9.4.1 Pressure transducer, available range 0–446 kPa
(0–50 psig), with measurement accuracy of ± 0.2% and
time constant less than 20 msec. (2)
9.4.2 Flow standard, with time constant less than 20
msec and with full scale that is 200% of DUT full scale
accurate to 1% of full scale, linear to 0.5% of full scale,
and capable of resolving to 0.2% of full scale.
9.4.3 Isolation valve (qty 1).
9.4.4 Data acquisition system measu res the electrical
signals from the device under test. The data acquisition
system may also read the signals from the flow
standard, record test data and control the test sequence.
9.4.5 MFC with time constant less th an 20 msec and a
full scale flow rate that is 10 times the full scale flow
rate of the DUT.
10 Materials
10.1 Clean, dry nitrogen, with a dew point less than or
equal to -40°C, at a delivery pressure of 791 kPa (100
psig).
11 Safety Precautions
11.1 This test method may involve hazardous
materials, operations, and equipment. This test method
does not purport to address the safety considerations
associated with its use. It is the responsibility of the
user to establish appropriate safety and health practices
and to determine the applicability of regulatory
limitations before using this method.
12 Test Specimen
12.1 Allow all components in the te st apparatus to
warm up following the manufacturer’s specification.
12.2 Take necessary steps when switching gases to
ensure that only the desired gas is in the DUT and flow
standard at the time the test is performed.
13 Preparation of Apparatus
13.1 Setup and Schematic — See Figures 1, 2, and 10.
13.2 Plumbing Design Requirements for Methods A
and C
13.3 The test system must be highly conductive and
must have no changes in direction closer than 20 tubing
diameters upstream of the DUT.