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SEMI E35-0305 © SEMI 1995, 2005 11 Category (k) Cost Element (m) Description Method Labor Engineering Costs of the engineering labor required to support the equ ipment set needed to me et the wafer s t art requirements o…

SEMI E35-0305 © SEMI 1995, 2005 10

Table 2 Elements of Recurring Costs by Category

Category (k) Cost Element (m) Description Method

Consumable Consumable Parts Cost of all parts of the piece of

equipment that are worn out by

the process operation of the piece

of equipment and require

replacement after less than 1 year

of operation.

Expressed in terms of cost per piece of equipment

per year.

Consumable

Monitor Units Costs of all test and filler units

consumed in the support of the

piece of equipment.

Multiply the number of monitor units consumed per

piece of equipment by the cost of each type of

monitor unit.

Consumable

Utilities Costs of all utilities (e.g.,

electricity, city water, ultrapure

water, process cooling water,

natural gas) used by the piece of

equipment.

Multiply the annual amount of each utility used per

piece of equipment by the unit cost of each type of

utility.

Consumable

Supplies Cost of all supplies used by, or in

support of, the piece of equipment

(e.g., bulk gases, specialty gases,

specialty chemicals).

Multiply the annual amount of each supply used per

piece of equipment by the unit cost of each type of

supply.

Consumable

Waste Disposal Costs of removing and treating

spent chemical or effluent.

Multiply the annual amount of each spent chemical

or effluent produced per piece of equipment by the

unit cost of disposal of each type of spent chemical

or effluent. Equipment user may need to deduct the

salvage value, if any, from the costs.

Maintenance

Labor Costs of equipment user’s internal

repair and maintenance labor to

maintain the piece of equipment.

Calculate the number of maintenance labor hours

required for scheduled and unscheduled downtime

based on using SEMI E10 metric inputs. Multiply

the actual burdened costs for labor-hours of effort

multiplied by the number of hours for each

equipment purchaser’s personnel type. Equipment

user may need to adjust actual hours required due to

warranty and service contract coverage. Note that

operation labor hours are not included in this

category.

Maintenance

Spare Parts Costs of spare parts inventory for

equipment user.

Expressed in terms of cost per piece of equipment

per year. Note that depending on accounting rules,

an initial set of spare parts may be included as part

of the equipment acquisition cost, a fixed cost.

Maintenance

Repair Parts Costs of repair parts charged to

the equipment user.

Expressed in terms of cost per piece of equipment

per year. Equipment user should not double count

the cost of a part as both a spare part and a repair

part.

Maintenance

Service Contract Costs of service contract charged

to the equipment user.

Expressed in terms of cost per piece of equipment

per year.

Labor

Operation Costs of the operator labor

required to support the equipment

set needed to meet the wafer start

requirements of the equipment

user.

Calculate the number of operator labor hours

required based on equipment and manufacturing

specifications. Multiply the actual burdened costs

for labor-hours of effort by the total number of

hours for equipment purchaser’s operators.

Labor

Supervision Costs of the supervision labor

required to support the equipment

set needed to meet the wafer start

requirements of the equipment

user.

Calculate the number of supervision labor hours

required based on equipment and manufacturing

specifications. Multiply the actual burdened costs

for labor-hours of effort by the total number of

hours for equipment purchaser’s supervisors.

SEMI E35-0305 © SEMI 1995, 2005 11

Category (k) Cost Element (m) Description Method

Labor

Engineering Costs of the engineering labor

required to support the equipment

set needed to meet the wafer start

requirements of the equipment

user.

Calculate the number of engineering labor hours

required based on equipment and manufacturing

specifications. Multiply the actual burdened costs

for labor-hours of effort by the total number of

hours for equipment purchaser’s engineers.

Labor

Support Services Costs of the support service labor

required to support operations and

engineering.

Calculate the number of support service labor hours

required. Multiply the actual burdened costs for

labor-hours of effort by the total number of hours

for equipment purchaser’s support service

personnel.

The cost of monitor units includes both their initial acquisition cost and any initial preparation or reprocessing costs, if applicable. Preparation

and reprocessing costs may be calculated by summing the COOs from separate COO analyses of each of the preparation and reprocessing steps

performed.

Table 3 Elements of Recurring Scrap Cost

Category Cost Element Description Method

Scrap Equipment Yield

(EY) Loss

Costs of units lost, broken, or

irreversibly misprocessed by the

piece of equipment.

Calculate the EY Loss as the fraction of units lost,

broken, or irreversibly misprocessed by the piece of

equipment to the total number of units through the

piece of equipment (i.e., 1-EY). Multiply EY Loss

by the total number of units started through the

piece of equipment and by the actual total costs

invested in a unit at that step in the process (e.g.,

sum of initial unit starting material cost and COOs

for all prior process steps).

Scrap Defect Limited

Yield (DLY) Loss

Costs of units lost due to

electrical or inspection rejects

due to defects caused by the

piece of equipment.

Calculate the DLY Loss as the fraction of units lost

due to electrical or inspection rejects due to defects

caused by the piece of equipment (i.e., 1-DY). For

wafers, DY may be calculated using a modified

Seed’s formula:

DY =  (10)

1 + (AA



where AA is the active area of the device, D is the

defect density, and P is the probability that a defect

caused by the piece of equipment will be fatal.

Multiply DLY Loss by the total number of units

started through the piece of equipment and by the

actual total costs invested in a unit at that step in the

process where it is lost (e.g., sum of initial unit

starting material cost and COOs for all prior process

steps to the end of the process where it is tested).

Scrap Parametric Limited

Yield (PLY) Loss

Costs of units lost due to

electrical or inspection rejects

due to unit operating parameters

being outside the required range

caused by the piece of

equipment.

Calculate the PLY Loss as the fraction of units lost

(i.e., 1-PY). Multiply PLY Loss by total number of

units started through the piece of equipment and by

actual total costs invested in a unit at that step in the

process where it is lost (e.g., sum of initial unit

starting material cost and COOs for all prior process

steps to the end of the process where it is tested).

The cost of cleanroom space per unit area of effective usable production space includes both the fixed and recurring operations costs as

determined by a separate COO analysis outside the scope of this document.

APPENDIX 1

METHODOLOGY FOR DETERMINING ALPHA AND BETA ERRORS

NOTICE: The material in this appendix is an official part of SEMI E35 and was approved by full letter ballot

procedures on December 10, 2004.

A1-1 Purpose

A1-1.1 In silicon manufacturing product disposition is typically contingent on metrology equipment output. For

example, a unit may be shipped, scrapped, or reworked based on information from one or more measured output

characteristics.

A1-1.2 This appendix provides a standard methodology to include the cost due to misclassification of product

because of measurement variability and bias during testing of the product for conformance to a specification.

A1-1.3 This appendix is also intended to be useful for pre-purchase evaluation of pieces of measurement equipment

with different P/T ratios. It is also intended to be useful when comparing the operation of a single measurement

instrument in different throughput modes where P/T ratio changes with the throughput mode utilized or other

equipment setup factors. This appendix can help users select the optimum cost solution based on their specific

process capability and requirements.

A1-2 Scope

A1-2.1 This appendix covers a methodology to determine the alpha and beta probabilities associated with

misclassification of product due to variability and bias of measurement equipment. Alpha probability (α) is

associated with failing units that conform to specifications. Beta probability (β) is associated with passing units that

do not conform to specifications.

A1-2.2 This appendix can be applied to make relative misclassification cost comparisons as part of a COO analysis

between two or more measurement gauges operating under conditions specified by the user. These conditions may

include any aspects of the measurement system affecting the measurement results directly or indirectly (e.g.,

ambient conditions, throughput, recipe). This appendix can also be used to compare the relative costs of a single

instrument under different operating conditions.

A1-2.2.1 A measurement gauge is defined by a specific realization of systems and subsystems required to make

measurements. Gauges that differ in at least one system or subsystem may be considered different for the purpose

of comparison.

A1-2.3 This appendix can be applied to any piece of metrology equipment or to the metrology portion of any piece

of equipment that includes metrology.

A1-2.4 This appendix covers the case in which the piece of metrology equipment is used to make binary decisions

about the item being measured, that is, only two outcomes are possible (e.g., pass/fail, go/no-go, ship/scrap).

Models for decisions with more than two outcomes, such as the binning of data, are beyond the scope of this

Appendix.

A1-2.5 To apply the formulae in this appendix, the user must estimate either the probability density function (PDF)

or cumulative distribution function (CDF) of the process characteristic or characteristics of interest. The

distributions can be based on a theoretical model or on empirical information obtained from manufacturing data.

A1-2.6 To apply the formulae in this appendix, the user must be able to estimate all biases and variances associated

with the piece of equipment being compared under the specified operating conditions and with respect to the process

characteristic(s) of interest. These values can be obtained from a measurement system capability analysis (see SEMI

E89).

A1-2.7 This appendix does not consider costs associated with other components of uncertainty outside of

measurement variability and bias.