semi合集-English.pdf - 第124页
SEMI E16-90 © SEMI 1990, 2004 3 Interval Rate Example t1 Initial System Response Less than 10 seconds t2 Leak Prior to Onset of Permeation w1 10 seconds to 1 minute t3 Increasing Perm eation 1 minute to 30 minutes t4 Tot…
SEMI E16-90 © SEMI 1990, 2004 2
the actual leak rate is to be reported, the sensitivity shall
be five times smaller than the leak to be measured. If
the sensitivity is not five times smaller, the actual leak
rate may be reported if the sensitivity of the detector is
also reported.
4.1.2 Helium must have access to all primary seals.
4.1.3 Connections between the MFC and the leak
detector must be leak-tight.
4.1.4 The ambient temperature of the MFC should be
25 ± 5C unless otherwise specified. If another test
temperature is used, it must be recorded during the test.
4.2 Test Procedures There are two basic setups
which may be used to measure the leak rate from the
external environment to the internal gas passages of the
MFC or from the internal passages to the external
environment. Results for either test method may be
reported. The method used must be reported as well. A
third test, the through-the-valve setup, is intended to
measure the quality of the valve seat shutoff.
4.2.1 Internally-Pressurized Leak Test The purpose
of this test set-up is to simulate operation of the MFC
under conditions where the internal pressure is above
ambient. The recommended internal pressure is 300
kPa absolute (30 psig) of helium (see Figure 1).
Regulator
Pressure Gauge
Helium
Temp
MFC
Leak Tight Enclosure
Pressure
Leak Rate
Mass Spec.
Gauges and
Vacuum Pumps
Leak Detector
Figure 1
Internally-Pressurized Leak Test
4.2.2 Externally-Pressurized Leak Test The purpose
of this test is to simulate operation of the MFC under
conditions where the internal pressure is at vacuum.
The external pressure should be equal to atmospheric
pressure. The internal pressure should be less than 100
kPa (see Figure 2).
Regulator
Pressure Gauge
Helium
Temp
MFC
Leak Tight Enclosure
Pressure
Leak Rate
Mass Spec.
Gauges and
Vacuum Pumps
Leak Detector
Figure 2
Externally-Pressurized Leak Test
4.2.3 Control Valve Seat Leak Test The purpose of
this test is to determine the leakage through the control
valve under simulated operation in the closed control
mode. The MFC should be electrically energized for
normal operation and placed in the closed position as
specified for the operation of the MFC. The input
pressure to the MFC should be 100 kPa ± 20%. The
outlet should be connected directly to the helium leak
detector, and pressure should be as low as possible
using good leak detector practice (see Figure 3).
Regulator
Pressure Gauge
MFC
Pressure
Leak Rate
Mass Spec.
Gauges and
Vacuum Pumps
Leak Detector
Helium
Figure 3
Control Valve Seat Leak Test
4.2.3.1 In the case of MFCs which are not designed for
positive shutoff at the control valve, alternative
methods may be employed if documented and reported.
4.3 Reporting Results The example shown in Figure
4 is a plot of leak detector output value vs. time for a
representative elastomer-sealed MFC. This curve is the
sum of mechanical and permeation leak components.
NOTE 2: All times are from application of helium, starting
with a leak detection system pumped down to base reading.
SEMI E16-90 © SEMI 1990, 2004 3
Interval Rate Example
t1 Initial System Response Less than 10 seconds
t2 Leak Prior to Onset of
Permeation
w1 10 seconds to 1 minute
t3 Increasing Permeation 1 minute to 30 minutes
t4 Total Saturation w2 Beyond 30 minutes
Figure 4
Leak Detector Output Value vs. Time
4.3.1 The actual shape of these curves and time
intervals is dependent on the design of the MFC under
test, the elastomer used, if any, and the characteristics
of the leak detection system. These time intervals must
be determined using sound engineering judgment
following qualification testing of the specific MFC
model and test set-up. Once determined, it is
recommended that receiving inspection consist of
measuring for leak rate value w1 at the end of interval
t2.
4.3.2 Following qualification testing, report typical
values for t1 through t4 and w1 and w2. w1 is primarily
the mechanical portion of the leak, and w2 is
mechanical plus permeation. In the case where w2 is
significantly greater than w1, w2 is primarily
permeation. In the case of a gross mechanical leak, w1
could greatly exceed, and thereby mask, w2.
NOTE 3: This test must be performed with elastomers that
are devoid of helium. Such elastomers have either not been
previously exposed to helium or have been degassed
following exposure. Once this test has been performed, the
elastomers must be purged of helium by the passage of time
and/or baking.
4.3.3 In good leak testing practice, the background
level should be verified before the application of helium
to ensure that the elastomers are in a helium degassed
state and that the leak detecting system is in proper
operation.
NOTICE: SEMI makes no warranties or
representations as to the suitability of the standards set
forth herein for any particular application. The
determination of the suitability of the standard is solely
the responsibility of the user. Users are cautioned to
refer to manufacturer's instructions, product labels,
product data sheets, and other relevant literature,
respecting any materials or equipment mentioned
herein. These standards are subject to change without
notice.
By publication of this standard, Semiconductor
Equipment and Materials International (SEMI) takes no
position respecting the validity of any patent rights or
copyrights asserted in connection with any items
mentioned in this standard. Users of this standard are
expressly advised that determination of any such patent
rights or copyrights, and the risk of infringement of
such rights are entirely their own responsibility.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction of
the contents in whole or in part is forbidden without express written
consent of SEMI.
SEMI E17-0600 © SEMI 1991, 20001
SEMI E17-0600
GUIDELINE FOR MASS FLOW CONTROLLER TRANSIENT
CHARACTERISTICS TESTS
This guideline 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 Regional
Standards Committee on April 10, 2000. Initially available at www.semi.org April 2000; to be published
June 2000. Originally published in 1991.
1 Scope
1.1 This guideline is intended to establish a common
basis for communication between users and suppliers of
semiconductor equipment. It provides terminology and
methodology aimed at eliminating confusion regarding
what previously has been referred to as MFC “response
time.” The conditions and procedures are given for
determining and expressing the transient characteristics
of a mass flow controller (MFC) to a step change in set
point. This guideline applies to mass flow controllers
for gases used in semiconductor fabrication equipment.
1.2 This guideline does not purport to address safety
issues, if any, associated with its use. It is the
responsibility of the users of this guideline to establish
appropriate safety and health practices and determine
the applicability of regulatory limitations prior to use.
2 Definitions (Figures 1 and 2)
2.1 Actual Flow — For the purpose of this standard,
the output value of the master reference standard.
2.2 Dead Time — The interval of time between the set
point step change and the start of the resulting
observable response.
2.3 Final Steady State Value — The average value of
the actual flow, after the effects of the input transient
have expired to a value equal to or below the intrinsic
drift and noise.
2.4 Settling Time — The time between the set point
step change and when the actual flow remains within
the specified band.
2.5 Step Response Time — The time between the
setpoint step change and when the actual flow first
enters the specified band.
2.6 Transient Overshoot — The maximum change in
actual flow minus the steady state change in actual
flow, expressed as a percentage of the set point step
change.
2.7 Transient Undershoot — The maximum amount
that the actual flow passes the final steady state value,
in the opposite direction of overshoot, expressed as a
percentage of the set point step change.
2.8 Set Point — The electrical input signal to the MFC
which sets the desired value of the controlled flow.
2.9 Specified Band — The region between ± 2% of the
final steady state value or ± 0.5% of full scale,
whichever is greater.
3 Test Setup
3.1 The purpose of the flow system is to furnish the
mass flow controller under test with a constant pressure
supply of suitable gas. It must also provide a means of
determining the gas flow rate through the mass flow
controller that responds to changes in gas flow
significantly faster than the device under test. The
recommended flow system for testing the speed of
response of MFCs is shown in Figure 3a.
3.2 The flow system shall have straight tubing or pipe
connecting the MFC to the master reference standard.
The inside diameter of the interconnecting tubing or
pipe shall be of sufficient size to preclude any pressure
drop that would affect the performance of the MFC.
3.3 The pneumatic time constant, Tau, should be
minimized. (See Section 3.7.)
Tau = (V*DPm) / (Qm*Pa)
Where:
V = Internal volume of the flow system between the
MFC under test and the master reference standard,
including tubing, fittings and the side of the master
reference standard that is connected to the MFC
under test.
Qm = Maximum volumetric flow expected during the test.
DPm = Pressure drop of the master reference standard at
flow Qm.
Pa = The absolute pressure present at the outlet of the
master reference standard at final steady state value.
3.4 The source of the test gas shall be capable of
delivering an essentially constant upstream pressure to
the mass flow controller under test during the transient
characterization. A maximum variation of ± 2% from