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SEMI C3-0699 © SEMI 19 86, 1999 8 Table 2 Carr ier Gases for GC Instruments Detector Gas Detecti on Level 0 - 10 0 ppt 100 ppt - 100 ppb 100 ppb - 100 ppm 100 ppm - 1% 1 % - 10 % 10 % - 100% TCD /USD Ar N/A N/A 99.99 99%…

100%1 / 7923
SEMI C3-0699 © SEMI 1986, 19997
It is assumed that the results of such a calculation must
not exceed the specification for the product being
analyzed.
6.10 Notes — Any special requirements for any
section within gas method may be included here. Notes
should reflect the minimum requirements to
successfully achieve the desired detection limits with
the equipment specified.
1.1 Impurity analyzed - description of method (e.g., gas
chromatograph with thermal conductivity detector).
1.1.1 Detection Limit - (mole/mole)
1.1.2 Instrument Parameters
1.1.2.1 Column(s):
Adsorbent, mesh size, length in meters, (dimensions if
other than 1/8 in. by 0.085 in.)
1.1.2.2 Carrier Flow: mL/min, gas type
1.1.2.3 Support Gases:
1.1.2.4 Sample Volume: mL
1.1.2.5 Temperatures:
Detector: °C
Columns: °C
Other Equipment: °C
1.1.3 Calibration Standard - amount ppm (or ppb)
impurity, balance if other than helium.
1.1.4 Operating Procedure (Parameters)
1.1.4.1 Order of elution
1.1.4.2 Special instructions
1.1.5 Notes
1.1.6 Figures
Figure 1
Format for Gas Chromatographic Method
7 Special Analyses
7.1 Resistivity Measurement — The American Society
of Testing and Materials (ASTM) is developing a
method to measure resistivity in substrates. This
method may be referenced when it is finalized.
7.2 Metal Analysis of Gaseous Silicon Compounds
7.2.1 Because of the importance of t race elemental
impurities impacting silicon device characteristics,
there is an increasing need for the detection and
quantitative analysis of low-level impurities in the
silicon materials used in device fabrication. Some of
these materials are gaseous silicon-containing
compounds, such as silane and the chlorosilanes. For
elemental analysis by FTIR or PLS, a compound must
first be converted to a solid form such as a single
crystalline rod or disc. For the quantitative
determination of metals and some non-metallic
elements, the gases can be passed through a series of
bubblers containing high-purity DI water or dilute
acids. The aqueous media can be concentrated and
analyzed by suitable techniques such as ICP or AA
spectroscopy. In both cases, the recovery is assumed to
be 100% efficient or, in other words, there is no loss of
any impurity from the silicon source.
7.2.2 FTIR (Fourier Transform Infrared)
Spectroscopy, PLS (Photoluminescence Spectroscopy)
and NAA (Neutron Activation Analysis) are probably
the most useful tools for the detection and analysis of
trace quantities of elemental impurities in solid silicon
materials. NAA requires special silicon material
specimens to be submitted to neutron irradiation in a
nuclear reactor and the analysis facility to be approved
by the Nuclear Regulatory Commission (NRC) and
other government agencies. In contrast, FTIR and PLS
do not require special governmental regulations, and the
instrumentation is available on the open market.
7.2.3 An FTIR spectrometer is an infrared
spectrometer in which a Michelson Interferometer is
used in place of a grating or prism. The simplicity of
the Michelson Interferometer, with only one moving
part, an oscillating mirror, along with a He-Ne laser as a
reference, provides nearly absolute frequency accuracy.
This translates into a high spectral resolution. FTIR has
greater detection efficiency since the energy-wasting
slits required for dispersive spectrometers are not used.
With a microcomputer to control the functions and to
perform data processing, signal averaging is used to
improve the signal-to-noise ratio. All these features lead
to good reproducibility and rapid measurement results
compared with conventional IR techniques.
7.2.3.1 As FTIR is a transmission met hod, it requires a
single crystalline silicon specimen with flat, parallel,
mirror-polished surfaces. For oxygen in silicon, the
absorption peak at 9 microns is used for quantitative
analyses. For carbon in silicon, the absorption band at
16 microns is used. Both measurements may be
performed at room temperature. (The carbon
determination has strong interference from the silicon
phonon band, but can be resolved with high purity,
carbon-free standards.) For the determination of
shallow donors and acceptors, FTIR measurements
must be made at liquid helium temperatures, but the
through-put is low. Although the operation of today's
FTIR instrument is relatively simple, the interpretation
of the results through software and associated
problems/solutions is not. Quantitative analysis is based
upon the measured percent transmission at the
characteristic wavelength and compared to standards.
Detection limits at about 10-12°K are in the 10
11
to 10
13
atoms/cc for shallow donors and acceptors, 3.1 × 10
14
atoms/cc for oxygen, and 2 × 10
15
atoms/cc for carbon.
SEMI C3-0699 © SEMI 1986, 1999 8
Table 2 Carrier Gases for GC Instruments
Detector Gas Detection Level
0 - 100 ppt 100 ppt - 100
ppb
100 ppb - 100
ppm
100 ppm - 1% 1% - 10% 10% - 100%
TCD/USD Ar N/A N/A 99.9999% 99.999% 99.998% 99.995%
H
2
N/A N/A 99.9995% 99.999% 99.99% 99.99%
He N/A N/A 99.9995% 99.9995% 99.999% 99.99%
N
2
N/A N/A 99.9995% 99.9995% 99.998%
< 0.5 ppm O
2
99.998%
HID/DID He N/A 99.9999% 99.9999% N/A N/A N/A
He* N/A 99.995% 99.995% N/A N/A N/A
FID He N/A N/A 99.9995% 99.999% 99.998% 99.99%
N
2
N/A N/A 99.999%
< 0.05 ppm
THC
99.999%
< 0.05 ppm
THC
99.998%
< 0.5 ppm THC
99.998%
H
2
** N/A N/A 99.9995%
< 0.2 ppm THC
99.999%
< 0.5 ppm THC
99.99%
< 0.5 ppm THC
99.99%
Air** N/A N/A HC Free
< 0.1 ppm THC
Zero Air
< 1 ppm THC
Zero Air
< 1 ppm THC
Blended Air
FPD He N/A 99.9995% 99.999% N/A N/A N/A
N
2
N/A 99.999%
< 0.05 THC
99.998%
< 0.5 ppm THC
N/A N/A N/A
H
2
** N/A 99.995%
< 0.2 ppm THC
99.999%
< 0.5 ppm THC
N/A N/A N/A
Air** N/A HC Free
< 0.1 ppm THC
Zero Air
< 1 ppm THC
N/A N/A N/A
RGD Ar 99.999%
< 1 ppm H
2
/CO
99.999%
< 1 ppm H
2
/CO
99.999%
< 1 ppm H
2
/CO
99.999%
< 1 ppm H
2
/CO
N/A N/A
N
2
99.999%
< 1 ppm H
2
/CO
99.999%
< 1 ppm H
2
/CO
99.999%
< 1 ppm H
2
/CO
99.999%
< 1 ppm H
2
/CO
N/A N/A
Air Zero Air
< 1 ppm H
2
/CO
Zero Air
< 1 ppm H
2
/CO
Zero Air
< 1 ppm H
2
/CO
Zero Air
< 1 ppm H
2
/CO
N/A N/A
ECD N
2
99.9995% 99.998%
< 0.5 ppm O
2
99.998%
< 0.5 ppm O
2
N/A N/A N/A
CH
4
/Ar EC Grade
< 1 ppb Total
Halocarbons
EC Grade
< 1 ppb Total
Halocarbons
EC Grade
< 1 ppb Total
Halocarbons
N/A N/A N/A
PID He N/A 99.9995% 99.995% N/A N/A N/A
N
2
N/A 99.9995% 99.998% N/A N/A N/A
MS/MSD H
2
99.9995%
< 0.2 ppm THC
99.999%
< 0.5 ppm THC
99.999%
< 0.5 ppm THC
99.99%
< 0.5 ppm THC
99.99%
< 0.5 ppm THC
99.99%
< 0.5 ppm THC
Ar 99.999% 99.998% 99.998% 99.998% 99.998% 99.998%
He 99.9995% 99.999% 99.999% 99.995% 99.995% 99.995%
N
2
99.9995% 99.998% 99.998% 99.998% 99.998% 99.998%
*purge gas
**combustion gases
SEMI C3-0699 © SEMI 1986, 19999
Table 3 Detectors for Gas Chromatography
Detector Type Temp
Limit
Analytes
Analyzed*
Carrier Gases Selectivity Detectability Linear
Range
Thermal Conductivity
(TCD)
U 400 CF
4
, PH
3
, SF
6
,
Fixed Gases
He, H
2
, Ar, N
2
N/A
4 × 10
-10
g/mL
>10
5
Ultrasonic (USD) U CO
2
, O
2
, N
2
,
CO
He, H
2
, Ar, O
2
, N
2
,
Air
N/A
1 × 10
-9
g/mL
10
6
Helium Ionization
(HID)
U 325 H
2
, O
2
, Ar,
N
2
, CO
He N/A
4 × 10
-14
g/mL
10
4
Discharge Ionization
(DID)
U same as HID He N/A
1 × 10
-12
g/mL
10
4
Flame Ionization
(FID)
S 420 C
1
-C
5
, C
x
F
y
,
C
x
Cl
y
F
z
, CO,
CO
2
H
2
/Air**, He, N
2
,
H
2
Hydrocarbons
2 × 10
-12
g/sec
>10
7
Flame Photometric
(FPD)
S 420 H
2
S
H
2
/Air**, He, N
2
,
H
2
S/C 10
3
-10
6
:1
P/C > 10
5
:1
S<1 × 10
-11
g/mL
P<1 × 10
-12
g/mL
S ≥ 10
3
P ≥ 10
4
Reduction Gas
(RGD)
S 300 CO, H
2
N
2
, Ar, He, Air H
2
, CO
H
2
0.5 – 2 ppb
CO 0.5 - 4 ppb
10
3
-10
4
Electron Capture
(ECD) (Ni
63)
S 420 N
2
, P5 halogens
5 × 10
-15
g
10
4
(linearized)
Photoionization (PID) S 350
PH
3
, H
2
S,
AsH
3
Ar, H
2
, N
2
By ionization
energy
2 × 10
-13
g/sec
>10
7
Thermionic (TID) S 420 H
2
, 8% H
2
/He
N/P 1:5
N/C 5 × 10
4
:1
P/C 10
5
:1
N 1 × 10
-13
g/sec
P 5 × 10
-14
g/sec
10
5
Mass Spectroscopy
(MS)
S 320 He, H
2
variable with
mass range
EI: 10-100 pg
NICI: variable as low as
25 fg
10
5
-10
6
Mass Density (MSD) S
Atomospheric
Pressure Mass
Spectroscopy
(APIMS)
*this does not represent detector capability; rather those analytes analyzed by current SEMI procedures
**used as combustion gases
7.2.4 Photoluminescence Spectroscopy (PLS) of
single crystalline silicon specimens at liquid helium
temperatures exhibits sharp emission lines. Electron
hole pairs called excitons are formed by incident
radiation (514.5 nm line from argon laser). The decay
of these “exciton or multi-exciton” states yields the
lines characteristic of the impurity atoms. For elemental
detection, the observed emission lines must be assigned
as being extrinsic (due to impurities) or intrinsic (due to
silicon). The luminescence process itself appears too
complex to attain precision or accuracy from basic
calculations. The PLS emissions are analyzed as a
function of wavelength, suggested to be 1077 to 1139
nm, for the elemental determination of shallow donors
and acceptors in silicon. Quantitative measurements of
impurities are based on the extrinsic-to-intrinsic
intensity ratio and compared to standards. The PLS
emissions are analyzed using a monochromator and
detected by a photomultiplier. Sensitivity in the range
of 5 × 10
10
to 5 × 10
11
atoms/cc has been claimed for B,
Al, P, and As.
7.2.4.1 In order to obtain reliable mea surements, the
silicon specimens must be in single crystalline form
with a mirrored surface. Epitaxial wafers with layers of
thickness greater than 10 microns are suitable, since the
sample's depth appears to be less than 5 microns.
However, it is still in the development stage, and very
few laboratories have such capability. A number of
questions remain unanswered, including the following:
1. What is the effect of compensating impurities?