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SEMI E140-0305 © SEMI 2005 3 5.2.7 cost of yield loss (CYL) — a unit lost at the end of a gi ven step repr esents the loss of th e c ost of the starting unit and the manufacturing to that p oint. In addition, units leavi…
SEMI E140-0305 © SEMI 2005 2
3.3 A COO calculation may have more detail than presented explicitly in this guide. The structure of the guide,
however, allows for these situations.
4 Referenced Standards
4.1 SEMI Standards
SEMI E10 — Specification for Definition and Measurement of Equipment Reliability, Availability, and
Maintainability (RAM)
SEMI E35 — Guide to Calculate Cost Of Ownership (COO) Metrics for Semiconductor Manufacturing Equipment
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 Abbreviations and Acronyms
5.1.1 COO — Cost of ownership
5.1.2 CYL — Cost of yield loss
5.1.3 DLY — Defect limited yield
5.1.4 ER — Equipment required (integer number)
5.1.5 EY — Equipment yield
5.1.6 PLY — Parametric limited yield
5.1.7 PRY— Product yield
5.1.8 PU — Production utilization (total)
5.1.9 TP — Throughput
5.2 Definitions
5.2.1 baseline cost of ownership — a constrained version of cost of ownership (COO) that only includes equipment
yield [i.e., defect limited yield and parametric limited yield are not included].
5.2.2 comprehensive cost of ownership — cost of ownership (COO) calculated with no constraints.
5.2.3 constrained cost of ownership — cost of ownership (COO) version with a set of defined restrictions to
facilitate comparisons or to remove ambiguity.
5.2.4 consumable — part of the piece of equipment that is worn out by the process operation of the piece of
equipment and requires replacement after less than one year of operation.
5.2.5 cost footprint — the area (A) of the smallest horizontal rectangle that contains all of the shadow footprint and
half of the easement space around the piece of equipment. This is calculated as:
DeDsDeWeWsWtA
2/12/1 (1)
DsDeWsWe
4/1
where:
De = Depth of the piece of equipment
Ds = Combined depth of the piece of equipment and easement space
We = Width of the piece of equipment
Ws = Combined width of the piece of equipment and easement space
5.2.6 cost of ownership (COO) — full cost of embedding, operating, and decommissioning in a factory environment
equipment needed to accommodate the required volume of production units.
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5.2.7 cost of yield loss (CYL) — a unit lost at the end of a given step represents the loss of the cost of the starting
unit and the manufacturing to that point. In addition, units leaving a step may be lost at some later step. Calculating
CYL therefore requires knowing the accumulated cost of manufacturing before the unit is lost. Therefore, CYL
should be tracked as a separate cost for factory optimization.
5.2.8 default or default value — a value to be used if actual data are not available. Also called example value.
Where possible, actual data should be used in COO calculations.
5.2.9 defect limited yield (DLY) — the fraction of units that are not lost from defects added by the equipment. For
wafer processing, defect yield is usually derived from a model.
5.2.10 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.
5.2.11 equipment required (ER) — the integer number of pieces of equipment required to obtain the production
throughput required for the step.
5.2.12 equipment throughput — see throughput.
5.2.13 equipment yield (EY) — the percentage of units received by the piece of 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.
5.2.14 fixed costs — costs incurred once and usually associated with the acquisition and incorporation of a piece of
equipment into the factory.
5.2.15 lifetime — the time over which the fixed and recurring costs are spread on an annualized basis.
5.2.15.1 production lifetime — the number of years a piece of equipment is used for manufacturing.
5.2.15.2 tax lifetime — the number of years as defined in compliance with local tax or accounting depreciation
practices.
5.2.16 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.
5.2.17 monitor unit — test or filler unit (e.g., wafer or device) consumed in the support of the piece of equipment.
Also called test unit.
5.2.18 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).
5.2.18.1 Discussion — As defined, OU has components attributable to both the unit manufacturer and to the
equipment supplier.
5.2.19 parametric limited yield (PLY) — the fraction of units that are not lost from device parameters being outside
the required range.
5.2.20 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.
5.2.21 recurring cost — cost that is incurred on an ongoing basis based on time and/or usage.
5.2.22 repair part — component to service the piece of equipment purchased at the time of repair.
5.2.23 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.
5.2.24 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
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(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).
5.2.25 spare part — prepurchased inventory of a part maintained to service the piece of equipment.
5.2.26 supplier — provider of equipment or services to the unit manufacturer. Also called equipment vendor or
equipment manufacturer.
5.2.27 test unit — see monitor unit.
5.2.28 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 nonproduct units is accounted for directly.
5.2.29 unit — any wafer, die, packaged device, or piece part thereof (includes product and nonproduct units).
5.2.30 volume requirement — the number of units required to be processed by the equipment in a specific time
period, normally units per week.
5.2.31 yield — see product yield.
6 Description of COO Model
6.1 COO Model Calculation — The formula for calculating COO is given in Equation 2.
COO = (F$ + R$ + Y$) / (L × TP × PRY × OU) (2)
where
F$ = annualized fixed costs, $
R$ = annualized recurring costs, $
Y$ = annualized yield costs (CYL), $
L = lifetime of piece of equipment, yrs
TP = throughput, units/yr
PRY = product yield, dimensionless
OU = operational uptime, dimensionless
6.1.1 F$ is calculated by summing the fixed cost categories F
ij
in Table 1 in SEMI E35.
6.1.2 R$ is calculated by summing the recurring cost categories R
ij
in Table 2 in SEMI E35.
6.1.3 Y$ is calculated by summing the recurring scrap cost categories in Table 3 in SEMI E35.
6.1.4 The parameters L and TP are input directly into the model.
6.1.5 The model calculates PRY from user inputs on numbers of wafers lost due to EY, DLY, and PLY.
6.1.6 The model calculates OU from inputs for scheduled and unscheduled maintenance (including assists), standby
time, qualification time, engineering time, and the scheduled production hours.
6.1.6.1 While the cost terms used specific currency units of dollars as an example, any currency may be used as
long as it is applied consistently throughout the model.