semi合集-English.pdf - 第236页

SEMI E35-0305 © SEMI 1995, 2005 5 5.2.35 process step — the sm allest unit of processing act ivity tha t can be defi ned in a pr ocess flow (SEMI E81). 5.2.36 product yield (PRY) — the fraction of units that pass through…

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SEMI E35-0305 © SEMI 1995, 2005 4
5.2.17 distribution — a characterization of the probability of realization for a measurable event over the range of
values that the measurements may assume.
5.2.18 easement space — the floor space that must remain clear to the rear and sides of the piece of equipment (but
not in front of the load face plane). This includes safety aisles, ergonomic maintenance access space, component
removal space, and room for doors to swing out.
5.2.19 equipment required (ER) — the integer number of pieces of equipment required to obtain the throughput for
the step.
5.2.20 equipment throughput — see throughput.
5.2.21 equipment yield (EY) — the fraction of units received by the equipment that can be passed to the next step
based on any criteria such as damaged units, or units determined to be defective by inspection or test. Inclusion of
equipment yield results in a decreasing population of units flowing through the factory. At later steps, equipment
will process fewer units than the full factory unit starts. For test equipment, validly rejected units are scrap, but not
a component of equipment yield.
5.2.22 fixed costs — costs incurred once and usually associated with the acquisition and incorporation of a piece of
equipment into the factory.
5.2.23 good unit equivalents (GUE) — the calculated number of equivalent units required to produce the same
number of units output if product yield was 100%.
5.2.24 joint probability — a probability density or cumulative distribution function comprised of two or more
random variables.
5.2.25 lifetime — the time over which the fixed and recurring costs are spread on an annualized basis.
5.2.25.1 production lifetime — the number of years a piece of equipment is used for manufacturing.
5.2.25.2 tax lifetime — the number of years as defined in compliance with local tax or accounting depreciation
practices.
5.2.26 lower specification limit (LSL) — value of a characteristic, below which a product is said to be
nonconforming.
5.2.27 material — bulk gas, specialty gas, or general or specialty chemical used in the process. Includes monitor
units consumed in the support of the piece of equipment.
5.2.28 measurand — particular attribute of a phenomenon, body, or substance subject to measurement [VIM].
5.2.29 measurement variability — differences associated with making multiple measurements on a given
measurand under specific conditions.
NOTE 4: Common (general) estimators of measurement variability are the variance, standard deviation, and variance
components. Specific estimators include repeatability and reproducibility.
5.2.30 monitor unit — test or filler unit (e.g., wafer or device) consumed in the support of the piece of equipment.
Also called test unit.
5.2.31 operational uptime (OU) — the percentage of time the piece of equipment is in a condition to perform its
intended function during the period of operations time. This calculation is intended to reflect overall operational
performance for a piece of equipment (SEMI E10).
5.2.31.1 Discussion — As defined, OU has components attributable to both the unit manufacturer and the
equipment supplier.
5.2.32 parametric limited yield (PLY) — the fraction of units that are not lost from device parameters being outside
the required range.
5.2.33 precision-to-tolerance (P/T) ratio — ratio of the precision of a measurement system (MS) to the tolerance
(i.e., absolute magnitude of the full range of the product specification) (SEMI E89).
5.2.34 probability density function (PDF) — a mathematical formula that specifies the relationship between values
that a random variable may assume and their likelihood of occurrence. It is the first derivative of the CDF.
SEMI E35-0305 © SEMI 1995, 2005 5
5.2.35 process step — the smallest unit of processing activity that can be defined in a process flow (SEMI E81).
5.2.36 product yield (PRY) — the fraction of units that pass through the factory and result in good product. Product
yield for units is the composite of all sources of yield loss.
5.2.37 random variable — a measurable event occurring such that any value from its distribution is equally likely
to take place.
5.2.38 recurring cost — cost that is incurred on an ongoing basis, based on time and/or usage.
5.2.39 repair part — component to service the piece of equipment purchased at the time of repair.
5.2.40 rework — the percentage of units being reprocessed by the piece of equipment because of a fault or defect.
Also called redo.
5.2.41 service contract — an agreement for the supplier to provide equipment service or maintenance under
specified terms and conditions beyond that which is supplied with the piece of equipment.
5.2.42 shadow footprint — the area of the floor space directly under every part of the piece of equipment during its
operation. This area includes any temporary projections from the piece of equipment during loading or processing
(e.g., carriers that stick out from the piece of equipment or equipment load ports that protrude only when the piece of
equipment is being loaded).
5.2.43 spare part — prepurchased inventory of a part maintained to service the piece of equipment.
5.2.44 standard deviation,
— the positive square root of the variance.
NOTE 5: The standard deviation of a population may be estimated from experimentally obtained data by the sample standard
deviation (s):
n
i
i
xx
n
s
1
2
)(
1
1
(2)
where:
n = number of data values,
x
i
= value of the i
th
data point, and
x = mean of the data distribution.
5.2.45 step — see process step.
5.2.46 supplier — provider of equipment or services to the unit manufacturer. Also called equipment vendor or
equipment manufacturer.
5.2.47 test unit — see monitor unit.
5.2.48 throughput (TP) — the number of units (e.g., wafers, devices) per hour the piece of equipment delivers to the
factory, including all input, output, and internal overhead operation. TP includes all test or monitor units processed,
since the cost of these non-product units is accounted for directly.
5.2.49 tool — often used synonymously with equipment or system in the silicon wafer processing industry
5.2.50 tooling — fixtures and adaptors required to modify a piece of equipment to the requirements of a specific
unit, test, or operation.
5.2.51 unit — any wafer, die, packaged device, or piece part thereof (includes product and non-product units).
5.2.52 upper specification limit (USL) — value of a characteristic, above which a product is said to be
nonconforming.
5.2.53 variance — a statistical estimator that quantifies spread around the mean of a probability density function.
5.2.54 volume requirement — the number of units required to be processed by the equipment in a specific time
period, normally units per week.
5.2.55 yield — see product yield.
SEMI E35-0305 © SEMI 1995, 2005 6
5.3 Symbols
5.3.1 — alpha probability
5.3.2 — beta probability
6 Cost of Ownership
Input Unit Cost
Input Unit Cost
Equipment
for
Step n+1
Equipment
for
Step n
Recurring Costs
Fixed Costs
Factory Flow
Current Step To Next Step Previous Step
Cost
of
Unit
Cost
of
Unit
$
$
Cost of Ownership = Cost of Equipment Ownership + Cost of Yield Loss
COO = CEO + CYL (3)
Cost of Ownership } $
Cost of Ownership } $
Rework or Redo Test
Rework or Redo Test
Scra
p
Scra
p
Figure 2
Accumulation of Cost during Factory Flow
6.1 Description of COO
6.1.1 COO is a metric for evaluating the incremental cost added to a unit of good product material flowing through
equipment embedded in a factory environment for a specified lifetime, including the CYL. COO is calculated on an
annualized basis. The metric is expressed as cost per good unit for one pass through the equipment. Figure 2
depicts this accumulation of cost which can be factored into two components, CEO and CYL, as shown in Equation
3.
6.1.2 COO is the full cost of embedding, operating, and decommissioning in a factory environment equipment
needed to accommodate the required volume of product material.
6.1.2.1 COO calculated with no constraints is referred to as comprehensive COO.
6.2 Constrained Versions of COO
6.2.1 A constrained version of COO imposes a set of defined restrictions to facilitate comparisons or to remove
ambiguity. An example is a baseline COO that only includes EY (i.e., DLY and PLY are not included.
6.2.2 Constraints should be predefined by all stakeholders in a specific equipment COO model, prior to estimating
COO, to minimize biasing of the COO estimate.
6.3 Lifetimes
6.3.1 The lifetime of a piece of equipment is the time over which the fixed and recurring costs are considered for
evaluating the annualized COO. The number of years that a piece of equipment is planned to be used in
manufacturing is the piece of equipment’s production lifetime.