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SEMI E10-0304 E © SEMI 1986, 2004 2 4.1.5 downti me event — a detectable occ urrence significant t o the equipmen t that causes the equipm ent to go from an uptime state to either a scheduled or an unscheduled downtim e …

SEMI E10-0304

SPECIFICATION FOR DEFINITION AND MEASUREMENT OF

EQUIPMENT RELIABILITY, AVAILABILITY, AND MAINTAINABILITY

(RAM)

This specification was technically approved by the Global Metrics Committee and is the direct responsibility

of the North American Metrics Committee. Current edition approved by the North American Regional

Standards Committee on October 15, 2003. Initially available at www.semi.org February 2004; to be

published March 2004. Originally published in 1986; previously published July 2001.

This standard was editorially modified in February 2004 to include changes omitted from the previous

edition. Changes were made to Table 1, Table R1-3, and Section R1-7.

1 Purpose

1.1 This document establishes a common basis for

communication between users and suppliers of

semiconductor manufacturing equipment by providing

standards for measuring RAM performance of that

equipment in a manufacturing environment.

2 Scope

2.1 The document defines six basic equipment states

into which all equipment conditions and periods of time

must fall. The equipment states are determined by

functional issues, independent of who performs the

function. The measurement of equipment reliability in

this specification concentrates on the relationship of

equipment failures to equipment usage, rather than the

relationship of failures to total elapsed time.

2.2 Section 5 (Equipment States) defines how

equipment time is categorized. Section 6 (RAM

Measurement) defines formulas for measurement of

equipment performance. Section 7 (Uncertainty

Measurement) gives additional methods for evaluating

the statistical significance of calculated performance

metrics.

2.3 Effective application of this specification requires

that equipment performance (RAM) be tracked with

regard to time and/or equipment cycles. Automated

tracking of equipment states is not within the scope of

this specification, but is covered by SEMI E58. Clear

and effective communication among users and suppliers

promotes continuous improvement in equipment

performance.

2.4 The RAM indices in this specification may be

applied directly to non-cluster tools at the whole

equipment and sub-system levels. The RAM indices

may be applied at the sub-system level (e.g., process

module) for multi-path cluster tools.

NOTICE: This standard does not purport to address

safety issues, if any, associated with its use. It is the

responsibility of the users of this standard to establish

appropriate safety and health practices and determine

the applicability of regulatory or other limitations prior

to use.

3 Referenced Standards

3.1 SEMI Standards

SEMI E58 — Automated Reliability, Availability, and

Maintainability Standard (ARAMS)

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

4 Terminology

4.1 Definitions

4.1.1 availability — the probability that the equipment

will be in a condition to perform its intended function

when required.

4.1.2 cluster tool — a manufacturing system made up

of integrated processing modules mechanically linked

together (the modules may or may not come from the

same supplier).

4.1.2.1 single path cluster tool — a cluster tool with

only one process flow path (as used).

4.1.2.2 multi-path cluster tool — a cluster tool with

more than one independent process flow path (e.g.,

multiple load ports/load-locks, multiple process

chambers of the same type) and used as such.

4.1.3 cycle — one complete operational sequence

(including unit load and unload) of processing,

manufacturing, or testing steps for an equipment system

or subsystem. In single unit processing systems, the

number of cycles equals the number of units processed.

In batch systems, the number of cycles equals the

number of batches processed.

4.1.4 downtime (DT) — the time when the equipment is

not in a condition, or is not available, to perform its

intended function. It does not include any portion of

non-scheduled time.

SEMI E10-0304

4.1.5 downtime event — a detectable occurrence

significant to the equipment that causes the equipment

to go from an uptime state to either a scheduled or an

unscheduled downtime state.

4.1.6 failure — any unscheduled downtime event that

changes the equipment to a condition where it cannot

perform its intended function. Any part failure,

software or process recipe problem, facility or utility

supply malfunction, or human error could cause the

failure.

NOTE 1: It is important to categorize and qualify failures in

ways that facilitate the resolution of problems and improve

overall equipment performance. Use of this specification

requires agreement between supplier and user on categorizing

failures.

4.1.7 equipment-related failure — any unplanned

event that changes the equipment to a condition where

it cannot perform its intended function solely caused by

the equipment.

4.1.8 host — the intelligent system that communicates

with the equipment, acts as a supervisory agent, and

represents the factory and the user to the equipment.

4.1.9 intended function — a manufacturing function

that the equipment was built to perform. This includes

transport functions for transport equipment and

measurement functions for metrology equipment, as

well as process functions such as physical vapor

deposition and wire bonding. Complex equipment may

have more than one intended function.

4.1.10 maintainability — the probability that the

equipment will be retained in, or restored to, a

condition where it can perform its intended function

within a specified period of time.

4.1.11 maintenance — the act of sustaining equipment

in or restoring it to a condition to perform its intended

function. In this document, maintenance refers to

function, not organization; it includes adjustments,

change of consumables,

software upgrades, repair,

preventive maintenance, etc., no matter who performs

the task.

4.1.12 manufacturing time — the sum of productive

time and standby time.

4.1.13 non-scheduled time — the time when the

equipment is not scheduled to be utilized in production.

4.1.14 operations time (oper-time) — total time minus

non-scheduled time.

4.1.15 operator — any person who communicates

locally with the equipment through the equipment’s

control panel.

4.1.16 product — units produced during productive

time (see unit).

4.1.17 ramp-down — the portion of a maintenance

procedure required to prepare the equipment for hands-

on work. It includes purging, cool-down, warm-up,

software backup, storing dynamic values (e.g.,

parameters, recipes), etc. Ramp-down is only included

in scheduled and unscheduled downtime.

4.1.18 ramp-up — the portion of a maintenance

procedure required, after the hands-on work is

completed, to return the equipment to a condition where

it can perform its intended function. It includes pump

down, warm-up, stabilization periods, initialization

routines, software load, restoring dynamic values (e.g.,

parameters, recipes), control system reboot, etc. It does

not include equipment or process test time. Ramp-up is

only included in scheduled and unscheduled downtime.

4.1.19 reliability — the probability that the equipment

will perform its intended function, within stated

conditions, for a specified period of time

4.1.20 shutdown — the time required to put the

equipment in a safe condition when entering a non-

scheduled state. It includes any procedures necessary

to reach a safe condition. Shutdown is only included in

non-scheduled time.

4.1.21 specification (equipment operation) — the

documented set of intended functions within stated

conditions for equipment operation as agreed upon

between user and supplier.

4.1.22 start-up — the time required for equipment to

achieve a condition where it can perform its intended

function, when leaving a non-scheduled state. It

includes pump down, warm-up, cool-down,

stabilization periods, initialization routines, software

load, restoring dynamic values (e.g., parameters,

recipes), control system reboot, etc. Start-up is only

included in non-scheduled time.

4.1.23 support tool — a tool that, although not part of a

piece of equipment, is required by and becomes integral

with it during the course of normal operation (e.g.,

cassettes, wafer carriers, probe cards, computerized

controllers/monitors).

4.1.24 total time — all time (at the rate of 24 hrs/day, 7

days/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.

4.1.25 training (off-line) — the instruction of personnel

in the operation and/or maintenance of equipment done

outside of operations time. Off-line training is only

included in non-scheduled time.

SEMI E10-0304

4.1.26 training (on-the-job) — the instruction of

personnel in the operation and/or maintenance of

equipment done during the course of normal work

functions. On-the-job training typically does not

interrupt operation or maintenance activities and can

therefore be included in any equipment state (except

standby and non-scheduled) without special

categorization.

4.1.27 unit — any wafer, substrate, die, packaged die,

or piece part thereof.

4.1.28 uptime — the time 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.

4.1.29 user — any entity interacting with the

equipment, either locally as an operator or remotely via

the host. From the equipment’s view point, both the

operator and the host

represent the user.

4.1.30 utilization — the percent of time the equipment

is performing its intended function during a specified

time period.

4.1.31 verification run — a single cycle of the equip-

ment (using units or no units) used to establish that it is

performing its intended function within specifications.

5 Equipment States

5.1 To clearly measure equipment performance

(RAM), this document defines six basic equipment

states into which all equipment conditions and periods

of time must fall.

5.2 The equipment states are determined by function,

not by organization. Any given maintenance

procedure, for example, is classified the same way no

matter who performs it, an operator, a production

technician, a maintenance technician, or a process

engineer.

5.3 Figure 1 is a stack chart of the six basic equipment

states. These basic equipment states can be divided into

as many sub-states as are required to achieve the

equipment tracking resolution that a manufacturing

operation desires. SEMI E10 makes no attempt to list

all possible sub-states, but does give some examples for

guidance.

5.4 Key blocks of time associated with the basic states

and example substates are given in Figure 2. These

blocks of time are used in the RAM equations given

later in this document. The blocks of time associated

with the basic states and example substates are

described in the following sections.

SCHEDULED

DOWNTIME

STANDBY

TIME

ENGINEERING

TIME

UNSCHEDULED

DOWNTIME

NON-SCHEDULED

TIME

PRODUCTIVE

TIME

Equipment

Uptime

Operations

Time

Total Time

Manufacturing

Time

Equipment

Downtime

Figure 1

Equipment States Stack Chart

5.5 PRODUCTIVE STATE — The time (productive

time) when the equipment is performing its intended

function. The productive state includes:

• Regular production (including loading and

unloading of units),

• Work for third parties,

• Rework, and

• Engineering runs done in conjunction with

production units (e.g., split lots and new

applications).

5.6 STANDBY STATE — The time (standby time),

other than non-scheduled time, when the equipment is

in a condition to perform its intended function,

chemicals and facilities are available, but it is not

operated. The standby state includes:

• No operator available (including breaks, lunches,

and meetings),

• No units available (including no units due to lack

of available support equipment, such as metrology

tools),

• No support tools (e.g., cassettes, wafer carriers,

probe cards), and

• No input from external automation systems (i.e.,

host).

5.7 ENGINEERING STATE — The time (engineering

time) when the equipment is in a condition to perform

its intended function (no equipment or process

problems exist), but is operated to conduct engineering

experiments. The engineering state includes: