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SEMI S2-0703a E © SEMI 1991, 2004 81 R14-6.2.18 safety PLC — a programmable logi c controller and associated I/O, certifie d as having the necessary safety integrity to ex ecute the safety-related function. R14-6.2.19 sa…

SEMI S2-0703a

R14-6.1.2 CAT. 4 — Category 4 (according to ISO

13859-1)

R14-6.1.3 CPU — Central Processing Unit

R14-6.1.4 EMO — Emergency Off

R14-6.1.5 EUC — Equipment Under Control

R14-6.1.6 FD — Field Device

R14-6.1.7 FECS — Fail-to-Safe Equipment Control

System

R14-6.1.8 GUI — Graphical User Interface

R14-6.1.9 I/O — Input/Output

R14-6.1.10 IFD — Intelligent Field Device

R14-6.1.11 ISFD — Intelligent Safety Field Device

R14-6.1.12 PLC — Programmable Logic Controller

R14-6.1.13 SIL — Safety Integrity Level (according to

IEC 61508)

R14-6.1.14 SRM — Safety Relay Module

R14-6.2 Definitions

R14-6.2.1 certified — Evaluated and approved for use

in a particular intended function in conformance with a

recognized standard by an accredited testing laboratory

(ATL).

NOTE 1: See SEMI S2 for definition of ATL.

R14-6.2.2 combined I/O — I/O systems of an FECS in

which non-safety-related and safety-related signal

modules are combined. (see Figure R14-2).

R14-6.2.3 common cause failure — failure, which is

the result of one or more events, causing coincident

failures of two or more separate channels in a multiple

channel system, leading to system failure.

R14-6.2.4 distributed I/O — input/output modules for

sensors and actuators interfacing to a network.

R14-6.2.5 electrical/electronic/programmable

electronic (adj.) — based on electrical OR electronic

OR programmable electronic technology.

NOTE 6: The term above is intended to cover any and all

devices or systems operating on electrical principles.

R14-6.2.6 Fail-to-safe equipment control system — A

programmable system of control circuits designed and

implemented for safety-related functions in accordance

with internationally recognized standards such as ISO

13849-1 (EN 954-1) or IEC 61508. These systems (e.g.

safety PLC, safety-related I/O modules) diagnose

internal and external faults and react upon detected

faults in a controlled manner in order to bring the

equipment to a safe state.

R14-6.2.7 field device — sensors and actuators such as

valves (electrical or pneumatic), temperature sensors,

proximity switches, pumps, motors etc.

R14-6.2.8 functional safety — The overall safety

design related to the EUC and the EUC control system.

Effective functional safety includes the correct

functioning of the electrical, electronic, or

programmable-electronic safety-related systems; or on

other-technology safety-related systems and may

include risk reduction measures.

R14-6.2.9 industrial controller — general term for

controller-technology, which includes PLC and PC-

based technology.

R14-6.2.10 intelligent field device — sensors and

actuators that use local intelligence to perform

functions such as communication, diagnosis and

interfacing to a network.

R14-6.2.11 network — general term for bus

technology, which includes field bus technology used in

control applications.

R14-6.2.12 programmable logic controller —

microprocessor based controller for sequential control;

the control logic of which can be changed through a

programming device connected to the controller, e.g.

programming panel, host computer, handheld terminal,

either directly or remotely through a network.

R14-6.2.13 random hardware failure — failure,

occurring at a random time, which results from one or

more of the possible degradation mechanisms in the

hardware.

R14-6.2.14 safety function — function to be

implemented by an electrical or electronic or

programmable electronic safety-related system, other

technology safety-related system or external risk

reduction facilities, which is intended to achieve or

maintain a safe state for the EUC, in respect of a

specific hazardous event.

R14-6.2.15 safety integrity — probability of a safety-

related system satisfactorily performing the required

safety functions under all the stated conditions within a

stated period of time.

R14-6.2.16 safety integrity level (SIL) — discrete level

(one out of a possible four) for specifying the safety

integrity requirements of the safety functions to be

allocated to the electrical or electronic or programmable

electronic safety-related systems, where safety integrity

level 4 has the highest level of safety integrity and

safety integrity level 1 has the lowest.

R14-6.2.17

safety network — a network certified for

safety applications (this can also be a subpart of a

standard network).

SEMI S2-0703a

R14-6.2.18 safety PLC — a programmable logic

controller and associated I/O, certified as having the

necessary safety integrity to execute the safety-related

function.

R14-6.2.19 safety relay (SR) —- A positive or force-

guided relay, that is used in safety relay modules

(SRMs) to achieve a fail-to-safe circuit.

R14-6.2.20 safety relay module (SRM) — redundant

self monitoring electro-mechanical/ solid state device

certified for use in safety applications

R14-6.2.21 safety-related I/O modules —I/O modules

capable of diagnosing internal and external faults and

configured to be redundant. (e.g., a second shutdown

path is included for output-circuits).

R14-6.2.22 safety-related programmable system —

systems designed and implemented for safety functions

in accordance with ISO 13849 or IEC 61508. These

system types (e.g. safety PLC, safety-related I/O

modules) can diagnose internal and external faults and

can react upon detected faults in a controlled manner.

R14-6.2.23 safety requirements specification —

specification containing all the requirements of the

safety functions that have to be performed by the

safety-related systems.

R14-6.2.24 solid state electronics — designation used

to describe devices and circuits fabricated from solid

materials such as semiconductors, ferrites, or thin films

as distinct from devices and circuits making use of

electromechanical technology, e.g. solid state relay,

micro controller.

R14-6.2.25 systematic failure — failure related in a

deterministic way to a certain cause, which can only be

eliminated by a modification of the design or of the

manufacturing process, operational procedures,

documentation or other relevant factors.

R14-7 State-of-the-Art Safety Control System

— Comprised of Solid State Electronics

R14-7.1 Failure to perform normal function (for

example a failure of a computer or its software) may

cause economic loss, but is not necessarily a safety

issue. However, failure of a safety-related component

to perform its safety function could result in a

hazardous condition. A fail-to-safe system should be

designed in a manner to ensure that failures do not

result in a hazardous situation. It is therefore important

to perform a system risk assessment to determine

safety-related functions and the - safety performance

required. The process outlined in following figure

should be followed.

Figure R14-1

Roadmap to Risk Assessment and System Design

R14-7.2 Safety Interlocks — Semiconductor

manufacturing equipment requires the use of fast,

reliable and efficient means of safety interlocking.

Important issues concerning complex machine

architectures include availability and diagnostic

capabilities for quick troubleshooting.

R14-7.2.1 A FECS should, even in the case of failure,

maintain a safe state of the EUC. Therefore, a FECS is

able to detect faults and cause the system to go to a safe

state. A properly designed FECS – using methods such

as self-monitoring for fault detection and subsequent

well defined reaction – can offer high availability and

diagnostics.

R14-7.2.2 Section 11.6 of SEMI S2 (including

exceptions and notes) indicates a preference for

electromechanical devices and components, and gives

guidance on their use. However, non-

electromechanical devices and components are

permitted and they can provide necessary risk reduction

while maintaining safety performance. Section 11.6,

Note 26 of SEMI S2, suggests some tools for

investigation of suitability for use. Additionally, IEC

61508, ANSI/ISA-SP84.01, and ISO 13849-1 (EN 954-

1) provide guidance on the safety system design,

SEMI S2-0703a

assessment and maintenance of suitable control

systems.

R14-7.2.3 The usage conditions and safety

performance should be determined by the finding of a

risk assessment as described in SEMI S10. Risk

assessment results can then be used to define

appropriate SIL levels and Categories.

NOTE 7:Emergency Off — Section 12.2.2 of SEMI S2 states

that the EMO system should consist of electromechanical

components. The exceptions give guidance to the design of

EMO circuits using alternative technologies. Regional,

national or industry standards may have additional

requirements (e.g., USA: ANSI/NFPA 79, Europe: EN

60204-1).

R14-7.2.4 Any deviation from the risk level of

electromechanical devices must be carefully evaluated

(see Section 8 of SEMI S2).

R14-7.2.5 Compliance with Section 12 of SEMI S2,

emergency shutdown will depend on the risk

assessment allowed in Section 8.3.11 of SEMI S2.

R14-7.3 Software and Programming

R14-7.3.1 The application software or function blocks

have to be verified before being used in an FECS. The

automation supplier usually provides a range of

approved software blocks.

R14-7.3.2 Access for programming of safety-related

functions should be restricted within the FECS to

trained people.

R14-7.3.3 To program or modify safety-related

programs or parts of it, specially trained or qualified

personnel are required. Any changes must be

documented and stored within the file history.

R14-8 Philosophy and General Concept

R14-8.1 Introduction — An automated machine

system mainly comprises components such as industrial

controller, drives, I/O etc. The level of safety

performance of equipment can differ depending on the

particular application of FECS. However, irrespective

of the particular application, the FECS always

comprises a series of sensors, logic elements and

actuators for safe shutdown or a motion into a safe and

stable machine state.

R14-8.1.1 The term FECS according to IEC 61508 Part

2, is equivalent to the terms SIS (safety instrumented

system) or SRS (safety related system) in other

application areas. The examples in this Related

Information show some possible architectures of the

logic system. Sensors, final elements and software are

discussed in this Related Information. Application

handbooks from automation suppliers provide users

with valuable information on how to use these

components in order to achieve a fail-to-safe,

equipment control system.

R14-8.1.2 For traditional semiconductor equipment,

non-safety-related and safety-related technology, are

separated. In many cases non-safety-related and safety-

related technology are linked, so that signals

representing diagnostics, enable, and feedback can be

exchanged.

R14-8.1.3 Main Characteristics of Architecture

Concepts

1. Fail-to-safe equipment control system with

conventional hardwired safety technology.

2. Fail-to-safe equipment control system with

separation between fail-to-safe and standard

network technology.

3. Fail-to-safe equipment control systems with

combined network technology for transmission

of fail-to-safe and standard data on a single

medium.

4. Redundancy can be used in all concepts to

increase availability. Different redundancy

concepts are in use (see R14-Section 9).

5. Visualization on the standard control part and

on the fail-to-safe part can be realized with

various interfaces on the standard part and on

the fail-to-safe part.

R14-8.2 Design of Architecture and Components

R14-8.2.1 Possible Application Areas

1. Semiconductor manufacturing industry

2. Guarding of people, machines, environment

and industrial processes

 Emergency stop functions,

 Emergency off functions,

 Emergency shutdown functions,

 Light gates,

 Guard doors,

 Scanners,

 Motion control with safety functions,

 Motor control with safety functions,

 Process valves with safety functions, and

 Process monitoring using safety-related interlocks.

R14-8.2.2 Safety-related Equipment Control System —

The design of FECS should be carried out in

accordance with IEC 61508 and applicable parts of the

other referenced standards. The safety controller is

used to control (open-loop) processes that can