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SEMI F64-0701 © SEMI 2001 1 SEMI F64-0701 TEST METHOD FOR DETERMINING PRESSURE EFFECTS ON INDIC A TED AND ACTU A L FLOW FOR M ASS FLOW CONTROLLER S This spe cification was te chnically approve d by the Global Fa cilities…

SEMI F63-00-0701 © SEMI 20013

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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

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

— maximum negative dev iation of actual

flow from nominal.

5.2.5

— maximum positive dev iation of actual

flow from nominal.

5.2.6

— 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

— inlet pressure

5.2.11 P

— outlet pressure

5.2.12 PC

— pressure coefficient of actual flow per

pressure change at a set point.

5.2.13 PC

— pressure coefficient of indicated flow

per pressure change at zero flow.

5.2.14 PC

— 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

— actual flow

5.2.18 Q

— rated full scale flow

5.2.19 Q

— indicated flow

5.2.20 Q

— nominal actual flow dur ing steady state

conditions.

5.2.21 Q

— steady state actual flow while inlet

pressure is being ramped.

5.2.22 Q

— set-point flow

5.2.23 T — time

5.2.24 t

— time when Q

is within 0 .5% of reading of

5.2.25 t

— time when pressure transi ent is initiated.

5.2.26 t

— settling time to Q

5.2.27 v — voltage

5.2.28 V

— equivalent internal cont rol volume of the

DUT.

5.2.29 V

— 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).