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SEMI E79-0304 © SEMI 1999, 2004 5 5.2.2.3 Theoret ical Product ion Time (for Actual Unit s or for Effective Units) — Production tim e (for actual units or fo r effective uni ts) during a period of observation t h at is e…

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SEMI E79-0304 © SEMI 1999, 2004 4
NOTE 3: One application of PEE is to measure the
productivity of non-constraint tools that are expected to have
periods of idle time due to lack of available work.
4.2.9 reference overall equipment efficiency (R-OEE)
(time divided by time) — a measure of equipment
productivity relative to a benchmark theoretical
production time.
4.2.10 reference theoretical production time per unit
(RTHT) (time per unit) — the theoretical time required
to process a given recipe on benchmark equipment (i.e.,
the fastest equipment model of similar type), for a
benchmark product and process design. RTHT
shall be
defined to be less than or equal to the corresponding
theoretical time per unit (THT) used in calculating
OEE.
4.2.11 value-added in-process overall equipment
efficiency (VA-OEE) (time divided by time) — a
measure of equipment productivity assuming all time
except the value-added portion of processing cycles is
wasted equipment time.
4.2.12 value-added in-process theoretical production
time per unit (VTHT) (time per unit) — theoretical
production time per unit that credits only the objective
processing steps that add value to products. VTHT
shall
be defined to be less than or equal to engineering
theoretical production time per unit (ETHT) used in
calculating engineering OEE (E-OEE).
5 Equipment Productivity Measurement
5.1 The OEE calculation has been stated in terms that
are consistent with SEMI E10. Reference may be made
to Figure 1.
5.1.1 Figure 2 indicates how total time may be divided
into portions representing theoretical production time
for effective units and various sources of productivity
loss. The domain for productivity improvement of all
losses except operational efficiency is shared between
the equipment supplier and equipment user.
Productivity improvement of operational efficiency is
the exclusive domain of the equipment user.
5.1.2 The formulas introduced in this section require as
inputs the following fundamental quantities: total time,
equipment uptime, production time, and theoretical
production time. Sample calculations for each of the
formulas are provided in Appendix 1.
5.1.3 For efficiency measurement of individual
processing modules or of fixed-sequence cluster tools,
the fundamental quantities may be tallied in a
straightforward manner, and consequently the formulas
of this section may be applied in a straightforward
fashion.
5.1.4 For efficiency measurement of flexible-sequence
cluster tools, determination of the fundamental
quantities requires more involved calculations.
Formulas are provided in Section 6 for computing the
fundamental quantities for flexible-sequence cluster
tools. These fundamental quantities then may be used
as inputs to the formulas of this section to compute the
efficiency of a flexible-sequence cluster tool.
5.1.5 Additional supplemental efficiency metrics that
will enable users to assess more specific aspects of
equipment productivity are:
• Reference OEE,
• Engineering OEE,
• Value-Added In-Process OEE,
• Demand Equipment Efficiency,
• Production Equipment Efficiency, and
• Intrinsic Equipment Efficiency.
Definitions and formulas for these metrics are presented
in Appendix 2.
5.2 Overall Equipment Efficiency (OEE) — The
fraction of total time that equipment is producing
effective units at theoretically efficient rates.
Overall Equipment Efficiency (OEE)
= (Theoretical Production Time for Effective Units)
/(Total Time)
= (Availability Efficiency) × (Performance Efficiency)
× (Quality Efficiency)
5.2.1 Availability Efficiency — The fraction of total
time that the equipment is in a condition to perform its
intended function.
Availability Efficiency =
(Equipment Uptime)/(Total Time)
5.2.2 Performance Efficiency — The fraction of
equipment uptime that the equipment is processing
actual units at theoretically efficient rates.
Performance Efficiency =
(Operational Efficiency) × (Rate Efficiency)
5.2.2.1 Operational Efficiency — The fraction of
equipment uptime that the equipment is processing
actual units.
Operational Efficiency =
(Production Time)/(Equipment Uptime)
5.2.2.2 Rate Efficiency — The fraction of production
time that equipment is processing actual units at
theoretically efficient rates.
Rate Efficiency =
= (Theoretical Production Time for Actual Units)
/(Production Time)
SEMI E79-0304 © SEMI 1999, 2004 5
5.2.2.3 Theoretical Production Time (for Actual Units
or for Effective Units) — Production time (for actual
units or for effective units) during a period of
observation that is earned at strictly theoretically
efficient rates and assumes no efficiency losses.
Theoretical Production Time for Actual Units =
∑
i
(Actual Units of Recipe i × THT
i
)
Theoretical Production Time for Effective Units =
∑
i
(Effective Units of Recipe i × THT
i
)
where
THT
i
= theoretical production time per unit of recipe
i
NOTE 4: Theoretical Production Time (for actual units or for
effective units) may be calculated in terms of theoretical unit
throughput by recipe.
Theoretical Production Time for Actual Units =
∑
i
(Actual Units of Recipe i/UPH
i
)
Theoretical Production Time for Effective Units =
∑
i
(Effective Units of Recipe i/UPH
i
)
where
UPH
i
= theoretical unit throughput by recipe
of recipe i
5.2.3 Quality Efficiency — The theoretical production
time for Effective Units divided by the theoretical
production time for Actual Units.
Quality Efficiency =
(Theoretical Production Time for Effective Units)
/(Theoretical Production Time for Actual Units)
Total Time
Operations Time
Engineering Time
Uptime
Manufacturing Time
•Process experiments
•Equipment experiments
Productive Time Standby Time
•Regular production
•Work for 3rd party
•Engineering runs
•Rework
•Scrap
•No operator
•No product
•No support tool
•Associated cluster
module down
Operational
Efficiency
Quality Efficiency
Non-Scheduled Time
•Unworked shifts, days
•Installation, modification
rebuild or upgrade
•Off-line training
•Shutdown/startup
Downtime
Unscheduled Downtime Scheduled Downtime
•Maintenance delay
•Repair time
•Change of consumables
•Out of spec input
•Facilities related
•Maintenance delay
•Production tests
•Preventive maintenance
•Change of consumables
•Setup
•Facilities related
Availability
Efficiency
Rate Efficiency
Not specified in
SEMI E10 but occurs
during Productive Time
Figure 1
The Relationship Between SEMI E10 and OEE
SEMI E79-0304 © SEMI 1999, 2004 6
A
vailability Efficiency
L
osses
(Supplier and User Domain)
N
on-Scheduled Time
Scheduled Downtime
Unscheduled Downtime
Engineering
Standby
Production
Time
E
10 States
Theoretical
Production
Time for
Actual Units
Operational
E
fficiency Losses
(User Domain)
R
ate Efficiency
Losses
(Supplier and User Domain)
P
erformance
E
fficiency
L
osses
(Supplier and
User Domain)
A
ssignable Quality
E
fficiency Losses
(Supplier and User Domain)
Theoretical
Production Time
for Effective Units
E
79 Productivity Losses and
Improvement Domains
Figure 2
Stack Chart of Productivity Losses and Improvement Domains
6 Flexible-Sequence Cluster Tools
6.1 This section provides definitions and formulas
applicable to flexible-sequence cluster tools for
computing the following fundamental quantities:
theoretical production time, production time, equipment
uptime and total time. These quantities serve as inputs
to the formulas of Section 5 for efficiency
measurement.
6.1.1 Flexible-sequence cluster tool productivity is
measured at the individual processing module level of
detail according to a virtual machine model described in
this section. Productivity performance for the entire
flexible-sequence cluster tool is then calculated as the
aggregate productivity performance of its individual
processing modules.
NOTE 5: Evaluation of flexible-sequence cluster tool
productivity does not necessarily apply to the evaluation of
flexible-sequence cluster tool RAM.
6.2 Virtual Machine Model
6.2.1 A virtual machine is an individual processing
module in combination with the transport mechanisms
that serve that processing module. When a transport
mechanism is engaged in a material handling operation
that does not involve a particular processing module, it
is not considered to be operating as part of the virtual
machine defined for that processing module.
6.2.2 Theoretical production time per unit for a recipe
is the sum of theoretical times for all required
operational elements:
• Wafer loading,
• Elements occurring within a process module, and
• Wafer unloading.
6.2.2.1 Where appropriate, a combined loading and
unloading time may be replaced with a single
theoretical value for a wafer exchange.
6.3 Fundamental Quantities for Virtual Machines and
Flexible-Sequence Cluster Tools — This section defines
fundamental quantities that are evaluated for individual
virtual machines and flexible-sequence cluster tools as
inputs to the formulas presented in Section 5. In each
case, the fundamental quantity is determined for each
individual virtual machine within a flexible-sequence
cluster tool. The equivalent fundamental quantity for
the flexible-sequence cluster tool is the sum of the
quantities for the individual virtual machine.
NOTE 6: It is recognized that application-specific
interactions between virtual machines within flexible-
sequence cluster tools may impose varying amounts of
standby time on the individual virtual machines. This
approach treats these interactions as standby losses for the
flexible-sequence cluster tool and does not make any