This standard was technically approved by the global Environmental, Health & Safety Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on November 29, 2005. It was available at www.semi.org in February 2006 and on CD-ROM in March 2006. Originally published in 1991.

NOTICE: This document, as balloted, is intended to replace S3-91 in its entirety.

NOTICE: Paragraphs entitled NOTE are not an official part of this document and are not intended to modify or supercede it.

NOTICE: Conformance to provisions containing the word "should" is necessary to declare conformance to this document. Conformance to those provisions containing "may", "suggested", "preferred", or "recommended", or to NOTES or Related Information is not necessary to declare conformance.

The purpose of this Safety Guideline is to provide minimum general safety considerations for the design and documentation of heating systems used for changing or maintaining the temperatures of process liquids used in semiconductor and flat panel display manufacturing. This Safety Guideline provides several means (See Table 1.) of achieving a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14) for process liquid heating systems (PLHS). The choice of which means is used is not, however, a criterion for determining conformance with this document. For several common PLHS configurations, this Safety Guideline provides a prescriptive list of safety features to be incorporated in the PLHS. Design and performance criteria for those safety features are also provided. A PLHS that conforms to both the prescriptive list of safety features and the design and performance criteria for those safety features is presumed to achieve a risk level of no greater than Low (as defined by SEMI S10 and SEMI S14) and, thereby, conforms to this Safety Guideline. Conformance with this Safety Guideline may also be achieved by designing a PLHS and incorporating safety features that are selected, designed, and perform such that the risk of the equipment is no greater than Low, as assessed using SEMI S10 and SEMI S14 and considering the hazards discussed within this document. The second way of demonstrating conformance with this Safety Guideline is intended to provide a way to demonstrate conformance by PLHS configurations that are not among those for which prescriptive lists of safety features are provided and by PLHS configurations for which prescriptive lists are provided but for which alternative means of achieving a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14) are used.

Cross references within this document are presented as paragraph, figure, or table numbers, usually within parentheses. When this document is viewed with Adobe® Acrobat® or Acrobat Reader, clicking on the number should cause the view of the document to move to that paragraph, figure, or table.

The scope of this document is limited to heating systems designed to change or maintain the temperature of process liquids.Equipment, such as ovens and heated substrate supports (e.g., hotplates) intended to change or maintain the temperature of substrates are not "PLHS", even if heat is transferred to a process liquid. Deionized (DI) Water Heaters - deionized (DI) water heaters are included within the scope of this document when the heated DI water is used as a "process liquid" as defined in § 5. Heat Transfer Fluids (HTFs) - Where fluids are used to transfer heat between heating systems and process liquids, they are included within the scope of this document. For the purpose of this document, HTFs are limited to liquids. Although the scope of SEMI S3 is PLHS, this guideline may be used to evaluate subsystems to determine if integrating them into a PLHS will cause the PLHS not to conform to this guideline.

Referenced SEMI Standards
None.

Revision History
SEMI S3-0306 (complete rewrite)
SEMI S3-91 (first published)