semi合集-English.pdf - 第465页

SEMI E66-1103 © SEMI 1997, 2003 14 A2-1.4 The degrees of freedom (dof) is n 1 + n 2 - 2. For example, if n 1 = n 2 = 8, then dof = 14. A2-2 Interpretation A2-2.1 If |t| > t .975 , then the two mean s are significantly…

100%1 / 7923
SEMI E66-1103 © SEMI 1997, 2003 13
APPENDIX 2
t-TESTING; COMPARISON OF BACKGROUND MEAN AND DEVICE
MEAN
NOTE: This appendix was approved as an official part of SEMI E66 by full letter ballot procedure.
A2-1
A2-1.1 The background and DUT are expected to have low particle counts. Therefore, a statistical method is needed
to determine if there is a difference between background and DUT particle counts. The t-test is a method of
determining the actual statistical difference between the mean background particle count and the mean device
particle count. It can be used to characterize the particle contribution by the MFC Record results in Table A2-1.
Table A2-1 Test Worksheet
# Observation log Observation Remarks
Spool Cleanup 1 ... Nx All computations are in the logs of
original observations.
Stable Level X1 ... X25 Compute X
1, S1, UCL, LCL.
SPC X26 ... X334 Use all 8 values to recompute new
values (X
1,S1
).
Connect Device
Device Cleanup X34 ... X35 + n
Stable Level X34 + n + 1 ... X34 + n + 25 Compute X
2, S2, UCL, LCL
.
SPC X34 + n + 26 ... X34 + n + 34 Use all 8 values to recompute new
values (X
2, S2
).
NOTE: Use t-test to compare X’s. (See Appendix 2.)
A2-1.2 Calculate pooled standard deviation using the following equation:
S
pooled
=
(n
1
− 1)S
1
2
+ (n
2
− 1)S
2
2
n
1
+ n
2
− 2
where :
S
1
= background standard deviation
S
2
= device standard deviation
n
1
= background sample size
n
2
= device sample size
A2-1.3 Calculate the value of T (the t-test’s namesake) as follows:
t =
X
1
− X
2
S
pooled
1
n
1
+
1
n
2
where :
1 = background mean
2 = device mean
SEMI E66-1103 © SEMI 1997, 2003 14
A2-1.4 The degrees of freedom (dof) is n
1
+ n
2
- 2. For example, if n
1
= n
2
= 8, then dof = 14.
A2-2 Interpretation
A2-2.1 If |t| > t
.975
, then the two means are significantly different at the 95% level. If |t| > t
.995
, then the two means
are significantly different at the 99% level (e.g., by “95% confidence,” it is meant that the difference/no-difference
decision based on the t-test will be correct 95% of the time).
t
.975
= 2.145 (2-sided)
t
.995
= 2.977 (2-sided)
NOTE:
• All readings are log particle counts, not particle counts.
• Since logs are used, zeros have to be replaced by positive values (e.g., 1/2).
• To determine t value for a particular confidence level and (dof), refer to any statistical reference book.
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 mentioned herein. These standards are subject to change without notice.
The user’s attention is called to the possibility that compliance with this standard may require use of copyrighted
material or of an invention covered by patent rights. By publication of this standard, SEMI takes no position
respecting the validity of any patent rights or copyrights asserted in connection with any item mentioned in this
standard. Users of this standard are expressly advised that determination of any such patent rights or copyrights, and
the risk of infringment of such rights, are entirely their own responsibility.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o
the contents in whole or in part is forbidden without express written
consent of SEMI.
SEMI E67-0304 © SEMI 1997, 2004 1
SEMI E67-0304
TEST METHOD FOR DETERMINING RELIABILITY OF MASS FLOW
CONTROLLER
This test method was technically approved by the Global Gases Committee and is the direct responsibility of
the North American Gases Committee. Current edition approved by the North American Regional Standards
Committee on December 4, 2004. Initially available at www.semi.org February 2004; to be published March
2004. Originally published September 1997.
1 Purpose
1.1 This document describes a method to help
determine the ability of an MFC to meet the
manufacturer’s published specifications over its life
time. The results of the test will also be useful in the
comparison of MFCs.
2 Scope
2.1 This procedure applies to MFCs used in
semiconductor gas systems.
NOTICE: 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 and health practices and determine
the applicability of regulatory or other limitations prior
to use.
3 Limitations
3.1 This procedure is to be used only in conjunction
with another existing parametric test for mass flow
controllers to obtain the reliability data for that
particular parametric test.
3.2 New MFCs shall be used for reliability testing. An
MFC that has been put through this test method may be
tested for reliability again.
3.3 In addition to this procedure, the parametric test
may also cycle the valve. These cycles should be
ignored for determining the cumulative cycles that are
described in the data table.
3.4 This test will not address root cause analysis of
failures.
3.5 Read points have been selected for this test
procedure so that the test will take approximately six
months to complete. The read point schedule given is
only a suggested schedule and if the user feels that a
different read point schedule would better suit his
needs, this test method can still be used to obtain
reliability data.
4 Referenced Standards
4.1 SEMI Standards
SEMI E17 — Guideline for Mass Flow Controller
Transient Characteristics Tests
SEMI E66 — Test Method for Determining Particle
Contribution by Mass Flow Controllers
SEMI E69 — Test Method for Determining
Reproducibility and Zero Drift for Thermal Mass Flow
Controllers
SEMI F1 — Specification for Leak Integrity of High-
Purity Gas Piping Systems and Components
4.2 SEMASPECs
1
NOTE 1: The SEMASPECs noted here will be superceded by
the comparable SEMI documents when available.
90120391B-STD — SEMATECH Test Method for the
Determination of the Helium Leak Rate for Gas
Distribution System Components
92071220B-STD — SEMATECH Guide to Provisional
Test Methods for Mass Flow Controllers
4.3 Other Document
Nelson, Wayne, Applied Life Data Analysis, New
York, NY Wiley, 1982 (see Annex)
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
5 Terminology
5.1 Acronyms and Abbreviations
5.1.1 MFC — Mass flow controller
5.1.2 UHP — Ultra-high purity
5.2 Definitions
5.2.1 cycle — a repeating sequence of setpoints applied
to the MFC.
5.2.2 hard failure — a catastrophic mechanical failure
or electrical failure that results in an inoperable MFC,
1 SEMATECH, 2706 Montopolis Drive, Austin, TX 78741, USA
website: www.sematech.org.