semi合集-English.pdf - 第3929页
SEMI F35-0304 © SEMI 1998, 2004 3 8.1.1 The operation and calibration of the specific equipment used in performing this test. 8.1.2 The proper procedures in handli n g UHP gas es as agreed up on by supplier and user. 8.1…
SEMI F35-0304 © SEMI 1998, 2004 2
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
5 Terminology
5.1 Abbreviations and Acronyms
5.1.1 ppbv — parts per billion by volume.
5.2 Defintions
5.2.1 atmospheric impurities — the common
impurities to UHP gases that are found in atmospheric
air.
NOTE 1: Impurities such as N
2
, O
2
, H
2
O, CO
2
.
5.2.2 contaminant signature — typical baseline
performance of a specific sample point within a large
distribution system with respect to its O
2
impurity
concentration. This is considered to be a normal and
acceptable impurity level.
5.2.3 critical sample point — gas sample point which
is monitored continuously because it is deemed in a
critical location in the distribution system, or that which
is most sensitive to causing product/process quality
problems from the ingress of atmospheric air
impurities.
5.2.4 investigative sample point — gas sample point
which is selected for spot checking analysis as part of
an investigation to locate an atmospheric air leak
source.
5.2.5 low detectable limit — defined as the smallest
level of O
2
measurement which can be quantified after
performing a blank test on zero gas. For our purposes,
this is determined to be 2 times the total peak-to-peak
noise over 8 hours while the O
2
analyzer is sampling on
zero gas.
5.2.6 point of use — the connection point where the
gas distribution system connects to the process tool
which uses the UHP gas.
5.2.7 sensitivity — Defined as the smallest detectable
step change in O
2
that the analyzer is capable of
sensing.
5.2.8 ultra-high purity (UHP) gas distribution system
— semiconductor fab gas delivery system which
typically contains impurities from atmospheric air of <
0.2 ppb at the input source, and atmospheric impurities
at the point-of-use of typically < 1 ppb.
5.2.9 weekly zero drift — total analyzer drift while
measuring zero gas over a 1-week time period. Includes
all components of analyzer drift.
5.2.10 zero gas — test gas which is known to contain
less than 0.1 ppb of O
2
as an impurity.
6 Summary of Method
6.1 The user must identify critical sampling locations
in the UHP gas distribution system. These points are
either specific process tool points-of-use or key lateral
branch lines, which must avoid atmospheric
contamination, or representative of a critical purity zone
containing process tools that are particularly sensitive
to atmospheric contaminants.
6.2 Connect O
2
analysis equipment to these critical
sample points for continuous monitoring.
6.3 Qualify the performance of the O
2
analysis
equipment before collecting data.
6.4 Begin continuous monitoring of critical sample
points. Identify typical or baseline “contaminant
signature” performance of the UHP gas distribution
system.
6.5 Use continuous trend data to identify problematic
events (contaminant spikes) and/or significant changes
from the “contaminant signature” performance level.
6.6 Use additional investigative sample point
measurements (spot checks) along with observable
correlations to gas distribution system usage to locate
and correct atmospheric leak sources.
7 Interferences
7.1 While sampling from any point in the gas
distribution system, it is critical that the sample be
delivered to the O
2
analytical equipment without
introducing additional atmospheric O
2
. This could
create significant errors in the analysis. Observing a
higher O
2
reading after reducing the sample flow to the
analyzer may be an indication that there is a leak
between the sample point and the O
2
analysis
equipment.
7.2 An O
2
analyzer may become inaccurate due to
improper calibration or simply due to long-term
analyzer drift. This will cause inaccurate O
2
readings
which do not represent the true performance of the
UHP gas distribution system. The O
2
analyzer must be
operated per the manufacturer’s recommendation for
calibration technique, calibration frequency, and other
routine maintenance.
7.3 Some O
2
analytical methods have cross-sensitivity
to other gaseous components which may be found in
UHP gases (i.e., H
2
, CO, CH
4
, and other hydrocarbons).
8 Requirements
8.1 Personnel Qualification — Personnel performing
these tests in accordance with this test method shall
have suitable training and experience. Such personnel
shall, as a minimum, be knowledgeable of:
SEMI F35-0304 © SEMI 1998, 2004 3
8.1.1 The operation and calibration of the specific
equipment used in performing this test.
8.1.2 The proper procedures in handling UHP gases as
agreed upon by supplier and user.
8.1.3 The proper safety procedure in handling
combustible or toxic gases as agreed upon by supplier
and user.
8.1.4 The behavior of atmospheric leak sources relative
to position, pressure/flow, and gas usage.
9 Apparatus
9.1 An analyzer must be selected which is capable of
continuous ultra-low trace O
2
measurements, with the
ability to report measurements with at least once per
minute frequency.
9.2 The ultra-low trace O
2
analyzer shall meet or
exceed the following specifications. These
specifications are appropriately defined in Section 5:
Sensitivity < 0.1 ppb
Low Detectable Limit < 0.3 ppb
Weekly Zero Drift < 0.5 ppb
Response Time < 10 minutes for 90% of a
0–1 ppb O
2
step change
NOTE 2: The O
2
analysis must be conducted using an
analytical method which meets or exceeds the specifications
required by this test method. If not, the user will not be able to
confidently distinguish true gas distribution system impurity
trends from false analyzer trends.
10 Safety Precautions
10.1 This test method is not a replacement for safety
regulations. It is the responsibility of the user to ensure
that the UHP gas distribution systems under analysis
comply with applicable safety regulations, as agreed to
between gas supplier and user.
10.2 It is also the responsibility of the user to comply
with applicable safety regulations governing the
operation of the required O
2
analytical equipment, as
specified by the analyzer manufacturer.
11 Identify Sample Point Locations
11.1 Identify the critical sample point locations in the
UHP gas distribution system which allow for a
continuous gauging of overall system integrity. These
shall include, at a minimum:
11.1.1 An exit purity O
2
measurement of the UHP gas
at the furthest point of the gas distribution system
within the fab.
11.1.2 Sample point locations representing sub-
sections of the UHP gas distribution system, which are
deemed critical for the avoidance of atmospheric
impurities.
11.1.3 Point-of-use process tool locations which are
deemed critical for the avoidance of atmospheric
impurities.
11.2 A source purity O
2
measurement of the UHP gas
entering the gas distribution system is suggested to be
used as a reference comparison against other points
within the fab.
11.3 Additional investigative (spot check) O
2
measurements may be required at sample point
locations which aid in deducing the location of
suspected atmospheric leak sources. This will vary from
situation to situation. (See Section 16.)
11.4 The exact sample tap location must be
representative of the measurement point of interest.
Avoid measurement of dead-leg locations.
12 Preparation of Sample Point Locations
12.1 Thoroughly pre-purge the sample point prior to
connecting the O
2
analyzer.
12.2 Thoroughly cycle-purge any regulators or other
components in the sample system. Cycle the pressure at
least 20 times with a high/low pressure ratio of at least
5 times.
12.3 Connect the O
2
analyzer to the sample point using
appropriate UHP gas lines and fittings. Avoid using
long lengths of bellows-type tubing because of long
purge-down requirements. Avoid using Teflon or
plastic tubing of any kind. Teflon and most other
plastics are extremely permeable to O
2
and will cause
atmospheric O
2
leakage. Only a few feet of plastic
tubing can introduce ppm levels of O
2
.
12.4 Establish flow from the sample point to the O
2
analyzer per the manufacturer’s recommendations.
13 Calibration and Qualification
13.1 Follow the manufacturer’s recommendations for
initial start-up and calibration of the O
2
analyzer.
13.2 After initial start-up and calibration, adhere to the
manufacturer’s recommendations for routine calibration
and maintenance needed to achieve the required
performance specification as described in Section 9.2.
SEMI F35-0304 © SEMI 1998, 2004 4
13.3 There will be two modes of O
2
measurement:
13.3.1 Critical Sample Point O
2
Measurement
13.3.1.1 Applicable to O
2
measurements performed
continuously on the critical sample point locations
identified earlier.
13.3.1.2 Prior to continuous data collection use of the
analyzer, validate it by demonstrating the capability
required in the specification for Weekly Zero Drift.
Chart the zero baseline drift and peak-to-peak noise
while on zero gas for 1 week.
13.3.1.3 Re-validate the O
2
analyzer performance by
running a 24-hour blank test on zero gas monthly.
13.3.2 Investigative Sample Point O
2
Measurement
13.3.2.1 Applicable to spot check O
2
measurements
performed in the investigation of locating atmospheric
leak sources.
13.3.2.2 The O
2
analyzer must be operated for a time
period sufficient to establish the “contaminant
signature” at the point of interest.
13.3.2.3 Validate the O
2
analyzer with a blank test
prior to each use. Chart zero baseline drift over a period
of time which is twice as long as the expected time
required to make the O
2
measurement. If a
measurement can typically be made successfully in less
than one hour, then verify the zero drift and peak-
topeak noise with a two-hour blank test.
14 Data Collection Procedure
14.1 Collect all O
2
measurement data at a minimum of
1 point/minute using a chart recorder or data acquisition
device.
14.2 Graph data points with sufficient resolution to
observe trends over a one-week period. The graph must
also be able to resolve O
2
spikes which may last only
10–15 minutes.
15 Interpretation of Results
15.1 Generate graphs of the baseline “contaminant
signature” for each critical sample point location.
Compare the baseline “contaminant signature” with the
O
2
analyzer’s blank run on zero gas to validate that the
analyzer is producing useful data. The base-line
“contaminant signature” should exhibit equal or greater
O
2
variation than the blank run on zero gas.
15.2 Problem Identification
15.2.1 Observe data from critical sample point
locations and look for deviations (abnormal trends or
events) from the baseline “contaminant signature”.
15.2.2 Determine if deviations (observed trends or
events) are sufficient to impede mandatory atmospheric
impurity specifications or influence critical
product/process quality.
15.2.2.1 If yes, proceed into Section 16.
15.2.2.2 If no, continue observing O
2
data from critical
sample point locations.