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SEMI E46-0301 © SEMI 1995 , 2001 5 the weighing bottle (holding the Si-chips) and its lid are separately put inside the min ienvironment . T hen th e minienvi ronment is clo sed and k ept closed for a defined period of t…
SEMI E46-0301 © SEMI 1995, 2001 4
2 pipettes (glass), 100 mL
1 micro dropper with changeable tips of 2 µL (may
be PP)
1 micro spatula (metal)
1 micro balance, measuring range 10
-6
g to 1 g at
least
10.3.2.1 Preparation of the reference measurement
with HPB:
10.3.2.1.1 Before the HPB is weighed, the PFA-bottle
and the weighing boat have to be cleaned. For this the
weighing boat and 10 mL benzene are given into the
bottle. The bottle is closed and shaken well for approx.
1 minute. The benzene is discarded. This procedure is
repeated four times. After the last cleaning the empty
open bottle and the weighing boat, placed on a
decontaminated aluminum foil (see Section 10.2.1). are
allowed to dry at room temperature in a fume cupboard
for ten minutes. Then the bottle is closed. The weighing
boat is placed onto the micro balance by thermally
decontaminated cross tweezers. Approx. 5 mg of HPB
are weighed into the weighing boat by use of a
thermally decontaminated micro spatula. The weight is
recorded exactly for the later calculation. The weighing
boat is placed into the PFA bottle by the cross tweezers.
10.3.2.1.2 The volume of the benzene is measured
using a 100 mL-pipette. Before use, the pipette has to
be washed 5 times using 10 mL benzene each time. The
100 mL benzene are filled into the PFA flask, which is
closed immediately.
10.3.2.1.3 First the bottle, now containing HPB and
benzene, is shaken well for three minutes. Often this is
not sufficient for a complete dissolution of the HPB
(visible inspection). To assure complete dissolution, the
PFA flask is placed into an ultrasonic bath for 5
minutes (not longer, because solution may get hot).
Two minutes before the end of that time the preparation
of the silicon chip is started. The piece of silicon is
heated to red heat for one minute, placed on the
thermally decontaminated aluminum foil and given 5
minutes to cool. When the treatment in the ultrasonic
bath is finished, the PFA flask is shaken for three
minutes again, then given 2 minutes for just standing.
10.3.2.1.4 The bottle is opened. By the micro dropper
2 µL are taken from near the surface (tip not more than
1 mm under surface of liquid). The 2 µL are spread
onto the silicon chip in such a way that the liquid on the
chip covers the smallest possible area. Care is to be
taken to prevent large spreading or even dropping off
the liquid (e.g., the Si chip has to be positioned flat).
The liquid is given 5 minutes to evaporate (room
temperature, no extensive blowing of air). Then the
measurement of the HPB reference can be started.
10.3.2.1.5 Before each following HPB measurement
the flask again has to be shaken 3 minutes, 5 minutes
ultrasonic bath, shaking 3 minutes, allow two minutes
of resting. The solution of the HPB in benzene must not
be kept longer than 10 days.
10.3.2.1.6 The reproducibility of the integral value
(see calculation) achieved by this procedure is better
than 4%. Sample measurements shall be performed
only, if the reference measurement has provided a
reproducibility equal to or better than 10%.
NOTE 1: Hexaphenylbenzene has been chosen as a reference
compound because its signal is well-defined and its mobility
value is well separated from the peaks of nearly all other
relevant organic contaminants. It provides positive ions only.
A different reference, Dioctylphthalate, is needed for negative
ions.
10.3.2.1.7 DOP-reference samples: All the same as
HPB, except replacing the benzene by ethanol. The
DOP is weighed using a micro dropper (not spatula).
10.3.2.1.8 The mobility spectrum of dioctylphthalate
is also well separated but there are several peaks due to
thermal decomposition (phthalic anhydride etc.). This
compound is a frequently used plasticizer and therefore
one of the most critical polymer additives.
10.3.3 Measurement of the Headspace Samples —
Positive and negative ions are detected successively in
two separate runs. At least two independent
measurements are carried out for each polarity. Every
measurement to be saved consists of 2000 single scans
and is then repeated. Hence, an automated measurement
is required.
10.3.3.1 The silicon chip is placed in the furnace of
the IMS using thermally decontaminated cross
tweezers. The measurement of the drift time spectrum
(positive or negative polarity) has to be started
immediately after loading the desorption furnace with
the sample (time delay between sample introduction
and starting of the measurement: 15 s).
10.3.4 Termination of the Measurement — The
measurement is terminated when the signal intensity
has decreased to about 10% above the noise of the
blank measurement spectrum. If this point is not
reached after two hours, the measurement should be
terminated; in this case, the investigated sample does
not show suitable material properties.
10.4 Headspace Sampling in Minienvironments —
The crucible tongs are preconditioned as described in
Section 10.2, and the preconditioned aluminum foil is
placed beside the minienvironment that is to be
examined. After opening the minienvironment, the lid
of the weighing bottle is picked up with the crucible
tongs and carefully placed on the aluminum foil. Both
SEMI E46-0301 © SEMI 1995, 20015
the weighing bottle (holding the Si-chips) and its lid are
separately put inside the minienvironment. Then the
minienvironment is closed and kept closed for a defined
period of time. For this test method, one week (168 h)
is defined. After expiry of the storage time, the
weighing bottle is closed with its lid and removed from
the minienvironment.
10.4.1 The same procedure applies to standard wafer
boxes or to SMIF and similar boxes.
10.5 Headspace Sampling of Polymer Material at
Different Temperatures — The prepared polymer
material inside the wrapped weighing bottle (see
Section 10.2.5) is stored:
• either under clean laboratory conditions at room
temperature for a defined period of time
• or in a suitable oven at a temperature of 70°C or
120°C for exactly 1 hour followed by a cooling
period of 1 hour.
10.5.1 The wrapped weighing bottle is handled with a
pair of crucible tongs only.
10.6 Testing Requirements (check for device overload
during measurement)
10.6.1 Positive Ions: Water Cluster Signal Intensity —
The water cluster signal intensity must not decrease by
more than 10% of the blank spectra intensity during
measurement time; otherwise, the ion molecule reactor
has been overloaded. If this is the case, the polymer
sample is not likely to be suitable for use in
semiconductor processing because of unacceptable
properties.
10.6.2 Negative Ions: Oxygen Cluster Signal Intensity
— The same procedure as that in Section 10.6.1 must
be performed for negative ions; in this case, the oxygen
cluster signal intensity must not decrease by more than
20%.
11 Calculation
11.1 Description of Mobility Spectra Evaluation —
The signal intensities of the detected sample
contaminants are integrated over a specific interval for
both polarities. The background signal intensity is
integrated, outside the specific measurement interval,
with preference to spectral region prior to the peaks of
the reactant ions. The total background intensity
(integration of the relevant background signal) is
subtracted from the integrated contamination intensity
(background correction). The mean value of the
contamination signal from the blank measurement
(Section 10.3.1) spectra is subtracted accordingly. This
leads to individual contamination values from each
sample spectrum.
11.2 Calculation of reduced mobility:
K=E
-1
1
d
/t
d
and
K
0
= K (p/p
0
) (T
0
/T)
K : ion mobility (cm
2
/Vs)
K
0
: reduced ion mobility (cm
2
/Vs)
p: pressure
p
0
: standard pressure
T : temperature
T
0
: standard temperature (273.15K)
l
d
: drift length (cm)
t
d
: drift time (s)
E : electric field strength (V/cm)
K : Kelvin
11.2.1
Table 1 shows the specified integration range;
all reduced mobility values are given in units of cm
2
/Vs.
11.2.2 The resulting integrals for each spectrum are
summed up for the whole desorption time. This value is
compared to the appropriate value of the reference
sample (HPB or DOP).
11.2.3
This procedure ensures the comparison of the
evaluated sample contamination values between
different laboratories and measurement equipments.
12 Related Documents
12.1 K. Budde, “Application of Ion Mobility
Spectrometry to Semiconductor Technology,”
Proceedings of the Satellite Symposium to ESSDERC
89 (Berlin) of the Electrochemical Society (the
Electrochemical Society Pennington, 1990) PV 90-11,
p.215.
12.2
K. Budde, W. J. Holzapfel, “Measurement of
Organic Contamination from Silicon Surfaces,”
Proceedings, 38th Meeting, Institute of Environmental
Sciences, 3.-8.5.1992, Nashville, TN, p.483.
12.3
K. Budde, W. J. Holzapfel, “Detection of Volatile
Organic Surface Contaminations Arising from Wafer
Boxes and Cleaning Processes,” Proceedings of the
First International Symposium on Semiconductor
Wafer Bonding, (the Electrochemical Society
Pennington, 1992) PV 92-7, p. 271.
12.4
Proposal: SEMATECH Test Method for
Determining Outgassing Products from Semiconductor
Product Carriers.
12.5
S.N. Ketkar, S.M. Penn, and W.L. Fite,
“Influence of Coexisting Analytes in Atmospheric
Pressure Ionization Mass Spectrometry,” Anal. Chem.
63, (1991) 924.
SEMI E46-0301 © SEMI 1995, 2001 6
12.6 R.E. Clement, K.W.M. Siu, and H.H. Hill Jr.,
“Instrumentation for Trace Organic Monitoring,” Lewin
Publishers, Boca Raton 1991.
Table 1 Integration Range for the Evaluation of Ion
Mobility Spectra
Polarity of
Target Ions Sample Background
Signal Range
(sample)
positive HPB 42.10–5.81 0.86–0.77
negative DOP 37.30–7.35 1.99–1.63
positive Sample 42.10–5.81 2.24–0.84
negative Sample 37.30–7.35 2.30–0.91
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.
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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
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of such rights, are entirely their own responsibility.
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