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SEMI E69-0298 © SEMI 1998, 2003 6 Figure 3 Mass Flow Controller Test Fixture 11 Calibration Standardization 11.1 All measurem ent devices must have valid calibration certificates. 12 Conditioning 12.1 Place the MFC to be…

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SEMI E69-0298 © SEMI 1998, 2003 5
7 Interferences
7.1 The accuracy rating of the measuring equipment
must include superior measurement capability
compared with that of the DUT. In no instance should
the accuracy rating of the measuring equipment be less
than twice that of the DUT (e.g., if the accuracy of the
DUT is ± 1 sccm, then the accuracy of the measuring
device must be better than, or equal to, ± 1/2 sccm).
The traceability of all the pertinent measuring
instruments and devices should be realistically
established and quantified.
7.1.1 In addition, take care when using test instruments
with a specified accuracy expressed in percent of full
scale. For example, if an instrument with a specified
accuracy of ± 0.1% of full scale is used to measure the
output of the DUT, but this output signal falls only
within the lower third of the scale of the instrument, the
effective accuracy over the range of the instrument
being used may be ± 0.3%, which is unsuitable for
many applications.
7.1.2 Use special precautions to ensure that minimum
effects result from pneumatic noise in flow lines.
Monitor pressure both upstream and downstream of the
MFC to ensure that pneumatic noise is minimized.
7.1.3 The DUT should be installed so that the inlet
flow can be fully developed, pulsation-free, for the
specific conditions. This can be achieved by plumbing a
straight length of tubing 40–50 diameters long upstream
and another straight length 5 diameters long
downstream of the DUT. (For additional information
about inlet effects, refer to ASME MFC-1M.)
7.1.4 At regular calibration intervals, verify electrical
signals directly at the MFC connector to ensure that
there are no unacceptable line losses in the cables.
8 Apparatus
8.1 back pressure regulator
8.2 digital voltmeter
8.3 flow standard
8.4 heat exchanger
8.5 power supply
8.6 pressure transducer
8.7 setpoint generator
8.8 temperature probe
9 Precautions
9.1 Technical Precautions
9.1.1 Many analog-to-digital converter cards do not
differentiate between measurements of less than zero
and zero. It may be necessary to use a digital voltmeter
to record measurements below zero volts. Some MFCs
do not differentiate between measurements of less than
zero and zero. This may bias the results.
9.1.2 The manufacturer’s specifications and
instructions for installation and operation must be
applied during all testing.
9.1.3 All electrical measurements should be read on
devices with at least 4.5 digits of resolution. These
devices must have valid calibration certifications.
9.1.4 The mounting position of the device must be in
accordance with the manufacturer’s specifications. No
external mechanical constraints beyond the
manufacturer’s recommended mounting position shall
be permitted.
10 Preparation of Apparatus
10.1 Figure 3 is a representation of a recommended
generic testing apparatus. The flow standard is shown
downstream of the device under test (DUT). It may be
placed upstream of the DUT if the flow standard cannot
be exposed to a low pressure environment. In this case,
the user should be aware of possible back pressure
effects on the flow standard.
SEMI E69-0298 © SEMI 1998, 2003 6
Figure 3
Mass Flow Controller Test Fixture
11 Calibration Standardization
11.1 All measurement devices must have valid
calibration certificates.
12 Conditioning
12.1 Place the MFC to be tested in the testing
environment. Apply power to the MFC for the 24 hours
prior to initiating warm-up as defined by the
manufacturer. The valve should be in its “off” position
(closed for an NC valve, open for an NO valve).
12.2 Following the conditioning period, install and
warm up the device according to manufacturer’s
specifications.
12.3 Purge the MFC with nitrogen or argon following
the warm up period.
12.4 Allow the test gas to flow through the DUT for a
minimum of 10 minutes at 100% of flow.
12.5 Apply a 100% full-scale setpoint to the DUT and
wait for the flow to stabilize for 10 seconds. Apply the
lower setpoint limit to the DUT and wait for the flow to
stabilize for 10 seconds. Repeat this cycle two more
times. This process exercises the device before
initiating the test.
12.6 Test Conditions
12.6.1 The reference operating conditions shall be as
follows if the downstream pressure is atmospheric:
Ambient temperature 23 ± 2°C
Gas temperature Same as actual ambient
Ambient pressure 101.3 kPa (+ 4.7 or − 15.3 kPa)
Gas pressure P
1
, Inlet 274 ± 34 kPa
Gas pressure P
3
, Outlet 101.3 kPa (+ 4.7 kPa or − 15.3 kPa)
Relative humidity 40% ± 10%, noncondensing
Magnetic field ≤ 50 µT
Electromagnetic field < 100 µV/m
Vibration < 0.5 m/s
Shock ≤ 3 g
12.6.2 The reference operating conditions shall be as
follows if the downstream pressure is at vacuum:
Ambient temperature 23 ± 2°C
Gas temperature Same as actual ambient
Ambient pressure 101.3 kPa (+ 4.7 or − 15.3 kPa)
Gas pressure P
1
, Inlet 172 ± 34 kPa
Gas pressure P
3
, Outlet < 0.13 kPa
Relative humidity 40% ± 10%, noncondensing
Magnetic field ≤ 50 µT
Electromagnetic field < 100 µV/m
Vibration < 0.5 m/s
Shock ≤ 3 g
12.7 Power Supply Conditions
12.7.1 The reference power supply conditions used
shall be the reference values specified by the
manufacturer. For those instances when a range of
values is specified rather than a reference value, the
midpoint of the range shall be taken to be the reference
value.
SEMI E69-0298 © SEMI 1998, 2003 7
12.7.2 The reference power supply must be sufficiently
rated for the DUT. In addition, the following supply
conditions and tolerances shall apply:
DC supply reference voltage ± 0.1% of operating voltage
Noise and ripple of DC supply ≤ 0.1% rms
13 Procedure
13.1 Zero Offset
13.1.1 Close the gas shut-off valve upstream of the
device under test and apply a 100% setpoint to the DUT
to equilibrate the pressure across the MFC. Wait for the
flow to stabilize at a value near zero, then close the
downstream shut-off valve. Deactivate the MFC’s
control valve (open for (NO) valves, closed for (NC)
valves), and disable the MFC to auto zero if an auto-
zero disable option is available. After the electrical
output signal has stabilized for at least three minutes,
record the MFC zero offset on Table 1. (Consult the
manufacturer’s specifications for the stabilization time
and report this time on Table 2.)
Table 1 Data Tabulation
Week #___________
D
ate_____________
_
Technician________________________
M
FC______________
_
Input % Set Point (sccm) Indicated Flow (sccm) Actual Flow (sccm)
0 0 0 0 0 0
50
100
50
10
5 Wait 10 minutes Record no data
10
50
100
50
10
5 Wait 10 minutes Record no data
10
50
100
50
10
5 Wait 10 minutes Record no data
10