Background Statement for SEMI Draft Document 3846A
Revision to SEMI E10-0304E, SPECIFICATION FOR DEFINITION AND MEASUREMENT OF EQUIPMENT RELIABILITY, AVAILABILITY, AND MAINTAINABILITY (RAM), with title change to: SPECIFICATION FOR DEFINITION AND MEASUREMENT OF EQUIPMENT RELIABILITY, AVAILABILITY, AND MAINTAINABILITY (RAM) AND UTILIZATION
NOTICE: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this Document.
NOTICE: Recipients of this Document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, ‘patented technology’ is defined as technology for which a patent has been issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided.
Background
The E10-0304E Standard is past the mandatory five-year review period and in need of a thorough review by the user community. At the same time, the E10 Revision Task Force has undergone their own review of the Document in order to clarify and expand the content based on user input and experiences. It is our belief that we have not changed the overall intent of SEMI E10 and have only made changes and additions to further its aim of defining the method to consistently measure equipment RAM and utilization. The major revisions include:
· multi-path cluster tool (MPCT) RAM metrics moved to the main body as official metrics
· clarification and addition of new definitions
· several new metrics added and some previous metrics updated or retired
· metrics have been standardized for all equipment types, including MPCTs
This is a revised version of Document 3846 from that balloted in Cycle 4, 2011, which was failed by the NA Metrics Technical Committee at the NA SEMICON West 2011 Meetings and returned to the E10 Revision Task Force. This version directly addresses the concerns of a single reject voter. The first concern was distinguishing the productive time for one intended process set (IPS) from another. The logic for determining E10 states for IPSs has been altered for the tracking system to designate the Nonscheduled state for any IPS not in active use. This change required several supporting statements and Notes throughout the Document regarding the Nonscheduled state. The second concern was for the missing handling of division-by-zero errors, for which § 8.1.3 has been added explaining the general handling of such cases.
Unrelated to the single reject vote, this version also includes a number of very useful clarifications. For example, the Document consolidates on the term ‘bound’ rather than ‘limit’ when describing the endpoints of confidence intervals, especially in § 9. Also, a top-to-bottom editorial pass has been made to bring the Document into compliance with the latest SEMI Standards Style Manual.
Due to the extensive nature of the editing, no mark-up version of the changes is provided so the main body and Related Information 1 of the draft should be reviewed in their entirety. No other significant changes were made to Appendices 1 and 2, but these should also be reviewed in their entirety.
The breakout of Total Time into the six SEMI E10 major states of Productive Time, Standby Time, Engineering Time, Scheduled Downtime, Unscheduled Downtime and Nonscheduled Time has not been fundamentally changed.
As part of this revision, we have promoted the MPCT RAM metrics section from Related Information 1 in E10-0304E to the main body of the revised Document, which will formalize this material and make it an official part of the E10 Standard. In addition, state priority reporting was added to the MPCT RAM metrics.
A large number of defined terms and acronyms were either substantially revised or added; in many cases the added definitions are from other SEMI Standards. These are: component part, consumable material, consumable part, continuous downtime event, downtime event, engineering time, equipment, equipment module, equipment-related failure, equipment system, failure, host, intended function, intended process set (IPS), key group (K), mainframe equipment module, MPCT, noncluster tool, nonconsumable part, nonprocessing equipment module, nonscheduled time, nonsupplier, observation period, processing equipment, process path, productive time, module, recipe, scheduled downtime, single-path cluster tool (SPCT), standby time, state, supplier, training (off-line), and unscheduled downtime.
Of these definition changes, the reviewer should especially focus on changes to differentiate consumable materials and consumable parts and the clause added to the failure definition to clarify that subsequent problems occurring during a continuous unscheduled downtime are not counted as additional failures. In addition, the term ‘Intended Process Flow’ was changed to ‘Intended Process Set (IPS)’ and added as a definition. This is more equipment-centric terminology and reduces confusion with other definitions for ‘process flow’.
For consistency and ease of application, metrics have been standardized so one comprehensive set of metrics can be used for each IPS and the following equipment types: noncluster tool, SPCT, MPCT, and individual equipment modules that are part of an SPCT or MPCT. The reviewer should especially focus on this major change from the prior limited set of unique metrics for IPSs and MPCTs. To assist the reviewer in understanding these changes, please review the table below:
Metric / Status in Letter Ballot / Motivation /MTBFp / No change
MFDp / New / Mean failure duration for failures during productive time is a companion metric to MTBFp that supports calculation of ‘inherent availability’ for a renewal cycle of strictly productive time and related time for failures.
E-MTBFp / No change
MTBFu / New / Added as alternatives to MTBFp, etc. where engineering time and standby time are considered part of ‘normal’ equipment operation and not exempt from reliability measurement (e.g., equipment undergoing acceptance testing and qualification prior to production release or being used primarily for long-term process development).
MFDu / New
E-MTBFu / New
MCBF / RETIRED / Changed to specific uptime and productive time versions for consistency with MTBF metrics.
E-MCBF / RETIRED
MCBFu / New
E-MCBFu / New
MCBFp / New
E-MCBFp / New
Total Uptime / New / Added for consistency and completeness with utilization metrics and to bridge to uptime definition in SEMI E79.
Operational Uptime / No change
Equipment-Dependent Uptime / UPDATE / Metrics are redefined to more clearly and accurately reflect the original intention. Whereas the original denominator subtracts quantities from operations time to imply a conditional operations time, the new denominator is defined as the sum of explicit quantities with the same objective.
Unscheduled downtime metrics are added for completeness and consistency to demonstrate that the conditional uptime, scheduled downtime, and unscheduled downtime add up to 100% of the conditional operations time.
Supplier-Dependent Uptime / UPDATE
Equipment-Dependent Scheduled Downtime / UPDATE
Supplier-Dependent Scheduled Downtime / UPDATE
Equipment-Dependent Unscheduled Downtime / New
Supplier-Dependent Unscheduled Downtime / New
MTTPM / New / A new metric with a similar concept to MTTR, but to measure equipment system maintainability in terms of just PM time.
MTTR / No change
E-MTTR / No change
MTOL / No change
TFR / New / Two fundamentally new metrics that measure against a 24x7 timeline regardless of equipment system complexity. TFR measures the count of equipment module failure events and Impairment Time measures time when one or more equipment module failures is ongoing. These are simple, pragmatic measurements of maintainability, especially for MPCTs.
Impairment Time / New
Operational Utilization / No change
Total Utilization / No change
A new Related Information 1 section “MTBF, Renewal Processes, and the Exponential Distribution” was added to explain the origins of MTBF and why it is significant in regards to predicting survival times. As this is Related Information, it is not an official part of the Standard.
A completely revised Related Information 2 section (replacing prior Related Information 1) is also planned to give additional examples for calculating the new MPCT metrics, but will be completed for a subsequent revision. Once this technical content is completed in the main body, appropriate examples will be created.
These following sections have not had any significant technical content changes from E10-0304E:
Appendix 1: CONFIDENCE BOUND FACTORS
Appendix 2: RELIABILITY GROWTH OR DEGRADATION MODELS
Note concerning SEMI E58 (Automated Reliability, Availability, and Maintainability Standard (ARAMS): Concepts, Behavior, and Services):
Changes and additions to the substates of SEMI E10 states will result in the revised Document being temporarily out of synch with SEMI E58. The E58 ARAMS TF will need to come out of hiatus at a future date to make these changes or the E10 Revision TF may have to do so. In addition for consistency to E58, the revision now uses E58 state abbreviations (e.g., PRD, SBY) and references to time have been replaced by state or substate where appropriate.
Review and Adjudication Information
Task Force Review / Committee AdjudicationGroup: / E10 Revision Task Force / NA Metrics Technical Committee
Date: / October 24, 25, and 26, 2011 / October 26, 2011
Time & Time zone: / 0800-1200 PDT (Each day) / 1330-1800 PDT
Location: / SEMI Headquarters / SEMI Headquarters
City, State/Country: / San Jose, CA / San Jose, CA
Leader(s): / Michael Werre (Intel)
David Busing (KLA-Tencor) / David Bouldin (Fab Consulting)
Mark Frankfurth (Cymer)
Standards Staff: / Paul Trio (SEMI NA)
408.943. 7041
/ Paul Trio (SEMI NA)
408.943.7041
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Semiconductor Equipment and Materials International
3081 Zanker Road
San Jose, CA 95134-2127
Phone: 408.943.6900 Fax: 408.943.7943
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SEMI Draft Document 3846A
Revision to SEMI E10-0304E, SPECIFICATION FOR DEFINITION AND MEASUREMENT OF EQUIPMENT RELIABILITY, AVAILABILITY, AND MAINTAINABILITY (RAM), with title change to: SPECIFICATION FOR DEFINITION AND MEASUREMENT OF EQUIPMENT RELIABILITY, AVAILABILITY, AND MAINTAINABILITY (RAM) AND UTILIZATION
1 Purpose
1.1 This Document establishes a common basis for communication between users and suppliers of semiconductor manufacturing equipment by providing a standardized methodology for measuring reliability, availability, and maintainability (RAM) and utilization performance of equipment in a manufacturing environment.
2 Scope
2.1 The Document defines six mutually exclusive basic states into which all conditions and periods of time for an equipment system must fall. One state called unscheduled downtime defines a ‘failed’ state for an equipment system. The measurement of equipment system reliability in this Document concentrates on the relationship of equipment system failures to equipment system usage.
2.2 All metrics defined herein are applicable to equipment systems that include noncluster tools, single-path cluster tools (SPCTs), equipment modules within a multi-path cluster tool (MPCT), intended process sets (IPSs) of equipment modules, and MPCTs. This Document defines a treatment of RAM measurement for MPCTs by first defining performance of IPSs as a function of equipment module-level performance, then defining MPCT performance as a function of IPS performance. For each metric presented, any special handling required for IPSs and MPCTs is defined.
2.3 This Document defines basic metrics for:
2.3.1 Reliability — including mean time between failures and mean cycles between failures.
2.3.2 Availability — including total uptime, operational uptime, equipment-dependent uptime, and supplier-dependent uptime.
2.3.3 Maintainability — including mean time to repair, mean time to (perform) preventive maintenance, mean time offline, total failure rate, and impairment rate.
2.3.4 Utilization — including total utilization and operational utilization.
2.4 Supporting material included in this Document addresses concepts for measurement of MTBF uncertainty and reliability growth and degradation.
3 Limitations
3.1 Automated tracking of equipment states and performance is not within the scope of this Document, but is addressed by SEMI E58 and SEMI E116.
3.2 The results of the calculations contained in this Document are dependent on the operational conditions (e.g., specifications, processes, recipes, environment, maintenance strategies, human factors) for each user or equipment type.
3.3 This Document does not provide any guidance for assignment of responsibility for equipment system failures to user or supplier, except that certain downtime events and portions of downtime may be distinguished as being related to the equipment or dependent on the supplier. Otherwise, the equipment states are determined by functional issues of the equipment system, independent of who performs the function.
3.4 The metrics defined herein do not address efficiency, productivity, diminished throughput, or capacity of equipment systems. Equipment efficiency and productivity is addressed by SEMI E79.
3.5 This Document is intended to provide a concise treatment of basic reliability concepts of importance to equipment systems, as defined herein, and is not a comprehensive treatment of reliability theory in general.
NOTICE: This SEMI Standards and Safety Guidelines do not purport to address safety issues associated with its use. It is the responsibility of the users of the Documents to establish appropriate safety and health practices, and determine the applicability of regulatory or other limitations prior to use.
4 Referenced Standards
4.1 SEMI Standards
SEMI E35 — Guide to Calculate Cost of Ownership (COO) Metrics for Semiconductor Manufacturing Equipment
SEMI E58 — Automated Reliability, Availability, and Maintainability Standard (ARAMS): Concepts, Behavior, and Services
SEMI E79 — Specification for Definition and Measurement of Equipment Productivity
SEMI E116 — Specification for Equipment Performance Tracking
SEMI E149 — Guide for Equipment Supplier-Provided Documentation for the Acquisition and Use of Manufacturing Equipment
NOTICE: Unless otherwise indicated, all Documents cited shall be the latest published versions.
5 Terminology
5.1 Acronyms
5.1.1 AMSAA — Army Materials Systems Analysis Activity
5.1.2 ARAMS — Automated Reliability, Availability, and Maintainability Standard
5.1.3 COO — cost of ownership
5.1.4 DT — downtime
5.1.5 E-MCBFp — mean cycles between equipment-related failures during productive time
5.1.6 E-MCBFu — mean cycles between equipment-related failures during uptime
5.1.7 E-MTBFp — mean productive time between equipment-related failures
5.1.8 E-MTBFu — mean uptime time between equipment-related failures
5.1.9 E-MTTR — mean time to repair during equipment-related failures