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SEMI E45-1101 © SEMI 1995 , 2001 5 8.9.1 Minienvironment Exposur e — Th e following exposure time f or sa mpling s pecific minienvironm ents shall be used: Minienvi ronm ents used to st ore wafers : 168 h Minienvironm e …

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SEMI E45-1101 © SEMI 1995, 2001 4
with an elemental standard is carried out (blank — 0.5
µg/L – 1 µg/L).
8.6.3 A detection limit for sodium and copper better
than 5 × 10
9
atoms/cm
2
(approximately 0.1 µg/L for
GFAAS analysis) is recommended.
8.6.4 The detection limit is defined by 3 • σ • R (σ =
standard deviation, R = reciprocal slope of the
calibration curve).
8.6.5 The surface concentration is calculated as
follows:
C
s
= C
1
×
V × NA × 10
-9
/(W × A)
with:
C
s
(atoms/cm
2
): surface concentration
C
1
(µg/L): analyzed concentration
V(mL): volume of diluted sample
NA = 6.023 × 10
23
mol
–1
: Avogadro number
A (cm
2
): wafer surface area
W (g/mol): atomic weight of element (22.99 for
sodium, 86.54 for copper)
8.7 Sodium and Copper Analysis by ICP-MS
8.7.1 Calibration Standards — 1 µg/L for both sodium
and copper.
8.7.2 A detection limit for sodium and copper better
than 5 × 10
9
atoms/cm
2
(e.g., for 200–300 mm wafers)
is recommended.
8.7.3 The detection limit is defined by 3 • σ • R (σ =
standard deviation, R = reciprocal slope of the
calibration curve).
8.7.4 The surface concentration is calculated as
follows:
C
s
= C
1
×
V × NA × 10
-9
/(W×A)
with:
C
s
(atoms/cm
2
): surface concentration
C
1
(µg/L): analyzed concentration
V(ml): volume of diluted sample
NA = 6.023 × 10
23
/mol : Avogadro number
A (cm
2
): wafer surface area
W (g/mol): atomic weight of element (22.99 for
Na, 86.54 for copper)
8.8 Calcium and Iron Analysis by TXRF
8.8.1 Calibration Standards — The ISO 9001 quality
system shall be applied to the calibration. The
instrument is calibrated by analyzing the calibration
wafer. The calibration wafer is prepared by dropping a
solution of metal standard (e.g., Ni or Co) on a clean
wafer surface. The volume of the droplet is the same as
used for VPD preparation (up to 100 µL), and the
resulting surface concentration must be in the lower
10
11
atoms/cm
2
range. The droplet is then evaporated on
the wafer surface at room temperature under nitrogen
purge until the liquid matrix is removed. Its residue is
analyzed by TXRF. The detection limit is defined by 3 •
σ • R (σ = standard deviation, R = reciprocal slope of
the calibration curve). Note that the droplet area must
be smaller than the spot area of the detector.
8.8.2 Reproducibility shall be first established
following the procedure below.
8.8.3 Define a grid of 3 × 3 measurement points with
an inter distance of 3 mm. The reside position, found by
optical inspection, shall be located at the center of the
matrix.
8.8.4 Determine the intensity by short analyses of each
of the nine measurement locations. The analysis area is
at maximum intensity for the standard element of the
calibration wafer.
8.8.4.1 Calibration shall be checked weekly and after
each equipment service (e.g., after an exchange of
filament, anode, or repair of anode) with the same
calibration wafer.
8.8.4.2 The surface concentration is calculated as
follows:
C
s
= RSF
m
× (C
0
/I
0
) × I
with:
C
s
(atoms/cm
2
): surface concentration of analyzed
metal M
I (counts/s): analyzed intensity of metal M
C
0
(atoms
/
cm
2
): surface concentration of standard
metal S (Ni or Co) on calibration wafer
I
0
(counts/s): analyzed intensity of standard metal
S on calibration wafer
RSF
m
: relative sensitivity factor of investigated
metal M to standard metal S
8.8.4.3 The constants RSF
m
are implemented in the
software of the TXRF equipment.
8.9 Sampling Procedure — If the average elemental
concentration for the sampling wafers is higher than the
average elemental concentration plus three standard
deviations for the analyzed reference wafers, then the
sampled minienvironment is considered to cause
significant contamination.
SEMI E45-1101 © SEMI 1995, 20015
8.9.1 Minienvironment Exposure — The following
exposure time for sampling specific minienvironments
shall be used:
Minienvironments used to store wafers: 168 h
Minienvironments as an interface to process tools:
24 h
8.9.2 Minienvironments for Storing Wafers — Fill the
minienvironment with six wafers. Measure wafers by
VPD/GFAAS or VPD/ICP-MS in front, back, and
center slots. Use the adjacent wafers for VPD/TXRF.
8.9.3 Minienvironments for Introducing Wafers to
Process Tools — Introduce six wafers into the
minienvironment. Measure three wafers with
VPD/GFAAS or VPD/ICP-MS, one in the center
position and two at the edge positions opposite to each
other. Use the adjacent wafers for VPD/TXRF. In the
case of single wafer minienvironments, wafers are
processed sequentially. To ensure that no cross
contamination is introduced from conditions prevailing
in storing, transportation, or any of the handling
processes, precautions must be adhered to at all times.
9 Results
9.1 The investigated minienvironment must be
described in detail (e.g., construction, materials, history,
process, cleaning procedures, storage conditions). All
surface concentrations must be fully reported.
9.2 The number of tested sampling and reference
wafers, average elemental concentration, and standard
deviation of the reference wafers, slot positions,
position in the minienvironment, and number of
repeated experiments (if applicable) must be
documented.
9.3 All equipment, tools, and chemicals used must be
specified within the report.
10 Related Documents
10.1 SEMI Standards
SEMI C30 — Specifications and Guidelines for
Hydrogen Peroxide
NOTE 2: Unless otherwise indicated, all documents cited
shall be the latest published versions.
10.2 Other Documents
A. Shimazaki, H. Hiratsuka, Y. Matsushita, S. Yoshii,
Ext. Abs. 16th Conference on Solid State Devices and
Materials, Kobe, 281 (1984).
M. Hourai, T. Nakidomi, Y. Oka, K. Murakami, S.
Sumita, N. Fujino, T. Shiraiwa, Japan Journal of
Applied Physics 27, 12 (1988) L2361.
A. Huber, H.J. Rath, P. Eichinger, T. Bauer, L. Kotz, R.
Staudigl, Diagnostic Techniques for Semiconductor
Materials and Devices, ed. by T.J. Shaffner, D.K.
Schroder, ECS Proc. Vol. 88-20, 109 (1988).
P. Eichinger, H.J. Rath, H. Schwenke, Semiconductor
Fabrication: Technology and Metrology, ASTM STP
990, ed. by D.C. Gupta, American Society for Testing
and Materials, 305 (1989).
C. Neumann, P. Eichinger, Spectrochim. Acta 46B,
1369 (1991).
A. Shimazaki, Defects in Silicon II, ed. by W.M. Bullis,
U. Gösele, and F. Shimura, ECS Proc. Vol. 91-9, 47
(1991).
W. Hub, V. Penka, Microcontamination Conference
Proceedings, San Jose, Oct. 1991, 266.
N. Streckfuss, L. Frey, G. Zielonka, F. Kroninger, C.
Ryzlewicz, H. Ryssel, Fresenius Journal Analytical
Chemistry 343, 765 (1992).
R.S. Hockett, S. Ikeda, T. Taniguchi, Cleaning
Technology in Semiconductor Device Manufacturing,
ed. by J. Ruzyllo, R.E. Novak, ECS Proc. Vol. 92-12,
324 (1992).
L. Fabry, S. Pahlke, L. Kotz, E. Schemmel, Crystalline
Defects and Contamination: Their Impact and Control
in Device Manufacturing, ed. by B.O. Kolbesen, C.
Claeys, P. Stallhofer, F. Tardif, ECS Proc. Vol. 93-15,
232 (1993).
S. Tan, Nuclear Instruments and Materials in Physics
Research B99, 458 (1995).
NOTICE: SEMI makes no warranties or representa-
tions 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.
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,
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 o
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the contents in whole or in part is forbidden without express written
consent of SEMI.
SEMI E46-0301 © SEMI 1995, 20011
SEMI E46-0301
TEST METHOD FOR THE DETERMINATION OF ORGANIC
CONTAMINATION FROM MINIENVIRONMENTS USING ION MOBILITY
SPECTROMETRY (IMS)
This test method was technically approved by the Global Metrics Committee and is the direct responsibility
of the European Equipment Automation Committee. Current edition approved by the European Regional
Standards Committee on December 20, 2000. Initially available at www.semi.org February 2001; to be
published March 2001. Originally published in 1995.
1 Purpose
1.1 The purpose of this test method is to provide an
analytical procedure—Ion Mobility Spectrometry
(IMS)—for the determination of organic contamination
from minienvironments which has the capability of
testing their construction material.
2 Scope
2.1 Silicon wafers passed through or stored in
minienvironments may be affected by organic
contamination originating from construction materials.
Knowledge of this contamination assists the decision
about the application of minienvironments in
semiconductor manufacturing.
2.2 Ion Mobility Spectrometry was chosen as the
method to determine this contamination because it
provides an easy, widely applicable, fast and sensitive
way to measure organic contamination on surfaces.
2.3 Furthermore, IMS provides the possibility of
checking the contaminating effects of processing,
chemical carryover, and the characterization of future
polymeric materials for use in semiconductor
technology.
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 and health practices and determine
the applicability of regulatory limitations prior to use.
3 Referenced Documents
3.1 SEMI Documents
SEMI E19 — Standard Mechanical Interface (SMIF)
SEMI Minienvironment Terminology Workshop
Proceedings, April 2, 1993
4 Terminology
4.1 Box/Cassette/Minienvironment/Pod
4.2 DOP — Dioctylphthalate
4.3 Headspace — The volume above the sample
containing the gas to be analyzed
4.4 HPB — Hexaphenylbenzene
4.5 IMS — Ion Mobility Spectrometry
4.6 IMS/MS — Ion Mobility Spectrometry/Mass
Spectrometry
4.7 NS — Standardized Ground Jo int
4.8 SMIF (Standard Mechanical Interface) — The
interface plane between a pod and another
minienvironment as per SEMI E19.
4.9 PFA — Polyfluoroalkoxy
4.10 PP — Polypropylene
5 Summary of Method
5.1 This test method defines a fast, sensitive technique
for the determination of organic contamination from
minienvironments. The contamination is measured
directly from the silicon surface. Three important
aspects are covered:
a. Contamination due to the minienvironment alone,
b. Contamination from the use of minienvironments
for wafer processing, and
c. Contamination from future materials to be used in
semiconductor technology.
5.2 Silicon wafers are either placed in the
minienvironment or used for headspace sampling
experiments. The sample is heated and the target
compound is either desorbed or outgassed. These
compounds are swept by the carrier gas into the Ion
Molecule Reactor. Here the molecules are chemically
ionized under atmospheric pressure. The target ions are
separated in a drift cell by electrophoreses in the
gaseous state and detected by an electrometer.
Additionally, a quadrupole mass spectrometer could be
used as a second detector. The result is a quantitative
value for the total amount of organic surface
contamination.