semi合集-English.pdf - 第948页
SEMI E124-1103 © SEMI 2003 3 efficiency (measures the efficiency of production with respect to factory dynam ics). See Equation 8. 5.1.21 quality efficiency (time divided by time) — the theoretical production time for ef…
SEMI E124-1103 © SEMI 2003 2
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
5 Terminology
NOTE 1: All of the metrics defined below should be
calculated with respect to the period being measured.
5.1 Definitions
5.1.1 actual throughput rate — the finished units out
divided by the total time (shows how fast finished
wafers flow out of the factory). See Equation 19.
5.1.2 availability efficiency (time divided by time) —
the fraction of total time that the equipment is in a
condition to perform its intended function (SEMI E79).
5.1.3 average cycle time — the (unweighted) average
of cycle time over all of the units of production in
finished units out.
5.1.4 average work in process (WIP) — the average
cycle time multiplied by the actual throughput rate
(shows how many eventually finished units of
production fill the “pipeline” on average). See
Equation 15.
NOTE 2: This metric is not an average of the WIP over time,
since that would include units that are later scrapped before
finishing.
5.1.5 balance efficiency — the critical WIP divided by
the process capacity (measures how well the equipment
sets are balanced). See Equation 5.
5.1.6 best-case cycle time — the larger of the
theoretical cycle time and the quotient of the average
WIP divided by the bottleneck throughput rate (shows
the best cycle time that the factory can do given the
WIP loading). See Equation 18.
5.1.7 best-case throughput rate — the smaller of the
bottleneck throughput rate and the quotient of the
average WIP divided by the theoretical cycle time
(shows the best throughput rate that the factory can do
given the WIP loading). See Equation 20.
5.1.8 bottleneck throughput rate (R
max
) — the upper
bound on the factory throughput rate imposed by the
current bottleneck equipment set. If a process change
for a product causes this metric to change, it should be
considered a different product for the purposes of
performing these computations. See Equation 17.
NOTE 3: This metric is similar to (but not the same as) the
theoretical unit throughput by recipe metric (see Section
5.1.32) from SEMI E79.
NOTE 4: This metric is not an average over the bottleneck
throughput rates of each product.
5.1.9 critical WIP (W
0
) — the theoretical cycle time
multiplied by the bottleneck throughput rate (gives the
WIP level that theoretically allows the factory to have
the highest throughput rate with the shortest cycle
time). See Equation 10.
5.1.10 cycle time — the amount of time a unit of
production spends as WIP in the factory.
5.1.11 finished units out — the number of units of
production that finish processing and testing during the
period being measured.
5.1.12 good unit equivalents (GUE) out — the
(possibly non-integer) number of units of production
required to contain all of the good product that exits the
factory during the period being measured. See
Equation 12.
5.1.13 line yield — the fraction of units leaving the
factory that have finished processing (measures relative
material losses such as scrapped units). See Equation 6.
5.1.14 normalized production efficiency — the
production efficiency to the power of the normalizing
exponent (measures the normalized efficiency of the
process with respect to factory dynamics). See
Equation 4.
5.1.15 normalizing exponent — power that normalizes
the production efficiency so that a value of ½ for
normalized production efficiency indicates that the
factory is performing at the level of the threshold case
(which divides a well run factory from one badly
operated). See Equation 9. See Sections R1-1.7 and
R1-1.8 in Related Information 1 for a discussion of the
meaning of the threshold case and a derivation of
mathematical expression for the normalizing exponent.
5.1.16 operational efficiency (time divided by time) —
the fraction of equipment uptime that the equipment is
processing actual units (SEMI E79).
5.1.17 overall equipment efficiency (OEE) (time
divided by time) — a metric of equipment performance,
expressing the theoretical production time for the
effective unit output divided by the total time (SEMI
E79).
5.1.18 overall factory efficiency (OFE) — the volume
efficiency multiplied by the yield efficiency (shows how
well a factory is operating compared to how well it
could be operating for the given product mix). See
Equation 1.
5.1.19 process capacity — the maximum number of
units of production that can be processed
simultaneously throughout the factory (including units
being transported by material handling vehicles). See
Equation 11.
5.1.20 production efficiency — the throughput-rate
and cycle-time efficiency multiplied by the WIP
SEMI E124-1103 © SEMI 2003 3
efficiency (measures the efficiency of production with
respect to factory dynamics). See Equation 8.
5.1.21 quality efficiency (time divided by time) — the
theoretical production time for effective units divided
by the theoretical production time for actual units
(SEMI E79).
5.1.22 scrapped units out — the number of units of
production (including broken units, external rework,
etc.) that exit the factory without finishing production
during the period being measured.
5.1.23 set of bottleneck equipment (F
e*
) — the
collection of production equipment of the same type
that has the highest average operational efficiency in
the factory during the period being measured. Elements
of this set are indicated by “f”, and the equipment type
is indicated by “e*”.
NOTE 5: This set of bottleneck equipment might not be the
equipment set (often the expensive lithography exposure
equipment) that was planned to be the bottleneck in the
factory, but rather the equipment set with the highest average
operational efficiency (the fraction of time in use when
available) during the period being measured. If another
equipment set experiences significantly lower availability
than expected, it might become the bottleneck. Thus, the sets
of bottleneck equipment may be different between two
adjacent time periods, and the set of bottleneck equipment for
the period combining the two adjacent periods may be
different from the other two sets.
5.1.24 set of equipment of type e (F
e
) — the collection
of production equipment of type e∈E in the factory.
Elements of this set are indicated by “f”.
5.1.25 set of equipment types (E) — the collection of
the different types of production equipment in the
factory, including metrology equipment and material
handling vehicles and conveyors. Elements of this set
(which are the different types of equipment) are
indicated by “e”.
NOTE 6: If units are transported manually between process
steps, then the human transporters (and any carts or
mechanized vehicles that they operate to perform the
movement) should be considered a type of equipment for the
purpose of computing the metrics in this guide. This is not
intended to dehumanize people, but to ensure that the manual
transport time is included in such metrics as theoretical cycle
time.
5.1.26 set of process steps of product type p on
equipment type e (S
pe
) — the collection of the different
process steps (including metrology inspection and
material handling transport) planned for a unit of
production of product type p on equipment of type e in
the factory. Elements of this set are indicated by “s”.
5.1.27 set of product types (P) — the collection of the
different types of products manufactured in the factory.
Elements of this set are indicated by “p”.
5.1.28 test yield — the fraction of units leaving the
factory that have finished processing and have passed
final testing (measures relative losses due to parametric
or functional failure). See Equation 7.
5.1.29 theoretical cycle time (T
min
) — the minimum
time required to process a unit of production through
the factory (including material handling transport time)
if the unit never has to wait for equipment or a vehicle
to become available and if sequence-dependent set-ups
never have to be performed. This is also known as the
raw process time. If a process change for a product
causes this metric to change, it should be considered a
different product for the purposes of performing these
computations. If more than one product (or process
flow) is represented in the output, an average is taken
over each of the products’ theoretical cycle time
weighted by the fraction of that product found in
finished units out. See Equation 16.
NOTE 7: This metric is similar to (but not the same as) the
theoretical production time per unit (THT) metric (see Section
5.1.30) used in SEMI E79 from CSM 21 and 42
1
.
5.1.30 theoretical production time per unit (THT) (time
per unit) — for a given production recipe performed by
a given processing module, the minimum time to
complete processing on one unit of production
assuming no efficiency losses are present. The
determination of theoretical production time per unit is
based on continuous operation of the processing
module, where the module is assumed to operate in an
ideal condition. For equipment cycles that
simultaneously process more than one unit, theoretical
production time per unit is the minimum time to
perform the cycle on an equipment load whose size is
optimized for throughput divided by the number of
units in that optimized load (CSM 21 and 42).
5.1.31 theoretical throughput rate — the smaller of the
bottleneck throughput rate and the quotient of the WIP
capacity divided by the theoretical cycle time (gives an
unreachable upper bound on the factory throughput
rate). See Equation 21.
5.1.32 theoretical unit throughput by recipe (units per
time) — for a given production recipe, the number of
units per period of time that theoretically could be
processed by the equipment. For each recipe,
1 CSM 21: Closed-Loop Measurement of Equipment Efficiency &
Capacity, 1995: and CSM 42: Productivity Metrics for Flexible-
Sequence Cluster Tools, 1998; Engineering Systems Research Center,
University of California, Berkeley
http://esrc.berkeley.edu/csm/csmreports.html.
SEMI E124-1103 © SEMI 2003 4
theoretical unit throughput is equal to the reciprocal of
theoretical production time per unit (SEMI E79).
5.1.33 throughput rate — the number of units of
production that pass through a process per period of
time.
5.1.34 throughput-rate and cycle-time efficiency — the
best-case cycle time divided by the average cycle time
(shows the relative performance of the factory with
respect to throughput rate and cycle time). See
Equation 13. See Section R1-1.6 in Related
Information 1 for a discussion of this metric.
5.1.35 total time — all time (at the rate of 24 hours per
day, seven days per week) during the period being
measured. In order to have a valid representation of
total time, all six basic equipment states must be
accounted for and tracked accurately (SEMI E10).
NOTE 8: For factory-level productivity metrics, total time
should be larger than the average cycle time (and is
recommended to be twice as large as the average cycle time
and larger than the cycle time of any individual unit in
finished units out).
5.1.36 unit (of production) — the basic entity in the
factory (such as a wafer in a fab, a glass pane in a flat
panel factory, or a die in a post-wafer back-end chip
production facility) which acts as a product substrate
(and moves through the factory with no assembly or
disassembly processes). Only product units are
included (as opposed to test wafers or other non-
product devices).
NOTE 9: This definition is more restrictive than that given in
SEMI E10 in order to be sufficiently specific.
NOTE 10: Production lot sizes can (and typically do) include
multiple units of production, and units can (and typically do)
contain multiple product devices (usually of the same type but
possibly of different types). The user may chose to have the
production lot be the unit of production, but that is not
recommended because:
• the choice of lot size (and its inherent waiting time while
its individual units are serially processed) would no
longer be a relevant factor in evaluating how well the
factory is running,
• lots can vary in size (even in the same factory),
• the meaning of unit would be inconsitent with other
SEMI standards, and
• scrapped units out would not be properly accounted for.
5.1.37 uptime (equipment uptime) — the hours when
the equipment is in a condition to perform its intended
function. It includes productive, standby, and
engineering time, and does not include any portion of
non-scheduled time (SEMI E10).
5.1.38 volume efficiency — the normalized production
efficiency times the balance efficiency (measures the
total efficiency of the process with respect to factory
dynamics). See Equation 2.
5.1.39 WIP capacity (W
max
) — the maximum number
of units of production the factory can contain (including
on shelves, in stockers, on material handling transport
vehicles, on equipment load ports, in internal carrier
buffers, and in process chambers, but not including
space required for non-product units such as test
wafers, dummy wafers, and monitor wafers).
NOTE 11: This is not a practical WIP level, because it
represents total gridlock of the factory.
5.1.40 WIP efficiency — the quotient of the smaller of
the critical WIP and the average WIP divided by the
larger of the two (measures the efficiency of WIP levels
with respect to factory dynamics). See Equation 14.
5.1.41 WIP turnover — the finished units out divided
by the average WIP (shows how often the inventory of
work in process was replaced during the period being
measured). See Equation 22.
5.1.42 work in process (WIP) — the number of units of
production that have been released into the factory but
have not yet been scrapped, sent out for external
rework, or finished processing through all of their
production steps.
5.1.43 yield efficiency — the line yield times the test
yield (shows overall material efficiency). See Equation
3.
NOTE 12: This metric is similar to (but not the same as) the
quality efficiency metric (see Section 5.1.21) from SEMI E79.
6 Calculated Metrics
6.1 Figure 1 shows how the terms defined in Section 5
feed into each other. Arrows go from subordinate terms
to the term in which they are cited as a part of the
primary definition. Shown in the top row (in red
rounded rectangles) are the basic building-block metrics
for which no equations are needed in this guide; the
remaining metrics have their equation numbers given.
At the very bottom is the overall factory efficiency
metric into which almost everything feeds, although
many of its subordinate terms are useful in their own
right (if data availability or reliability is a problem).
Along the left side (in green rounded rectangles) are the
quality metrics that show the efficiency of the process
with respect to use of materials. The remainder of the
metrics (in blue rectangles) are production metrics that
show the efficiency of the process with respect to
factory dynamics (without the effects of yield and scrap
losses). Related Information 1 gives an exposition of
the underlying science behind these production metrics.