downloadGroupGroupnoun_press release_995423_000000 copyGroupnoun_Feed_96767_000000Group 19noun_pictures_1817522_000000Member company iconResource item iconStore item iconGroup 19Group 19noun_Photo_2085192_000000 Copynoun_presentation_2096081_000000Group 19Group Copy 7noun_webinar_692730_000000Path

Critical Revision to Safety Interlock Design Systems in SEMI S2

By Kevin Nguyen, SEMI HQ

SEMI S2, Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment, provides industry accepted guidelines for semiconductor manufacturing equipment and is intended as a set of performance-based environmental, health, and safety (EHS) considerations for semiconductor manufacturing equipment. By using SEMI S2, users and suppliers can procure and design equipment to minimize hazards related to equipment, facilities, worker environment, and personnel that could result in significant injury or death.

Though no specific reports of equipment failing SEMI S2 assessments or proven unsafe were publicly made, subject matter experts raised the concern that the current definitions and guidelines for safety interlock systems inadequate. Because of this, the SEMI EHS North America Technical Committee formed the SEMI S2 Interlocks Design Task Force (TF) in July 2021.

The TF meets biweekly via teleconferences to clarify definitions such as “fail safe” and “fault tolerant” around interlock systems. Since many parts in SEMI S2 are connected, the TF’s review of the standard led to cumulative revisions beyond the intended scope. The bullet points below map out the TF’s progress as well as other concerns.

  • SEMI S2 Purpose and Scope clarifications
  • Definitions for “acceptable risk”, “accumulation of faults”, “foreseen”, “hazardous chemical”, “hazardous gas”, “human error”, “reasonably foreseeable”, “residual hazard”, “residual risk”, “safe”, “safety interlock”, “unacceptable risk”, and “unsafe”
  • Moved away from “increased hazard” (or similar) to “unacceptable risk”
  • Clarified definitions for “fail safe” and “fault-tolerant”
  • Introduced “accumulation of faults” instead of “single point failure”
  • Introduced and working on consistent use of Hierarchy of Controls in SEMI S2
  • Working on “hazardous chemicals” defining with GHS instead of NFPA 704
  • Working on consistent use of “safety interlock systems”
  • Replace “hazard labels” with “safety labels” (considering – refer to SEMI S1 TF)
  • Future consideration: new interlock devices and technologies

Other concerns:

  • Interpretation difficulties, unclear definitions, and SEMI S2 lack of consistency
  • A SEMI S2 compliant interlock system could not meet safety requirements
  • Situations where reliability is compared to failure mode
  • Increased risk deemed unacceptable by default
  • Unclear interlock requirements during maintenance modes

EHS SEMI Standards Members were supportive of the progress but felt that the current charter and scope of the TF should also be revised. As the scope of the activity expands, the TF intends to perform a major revision of SEMI S2, which will open the entire standard for review.  

According to the SEMI Procedure Manual (Note 13), if a major revision to an existing standard is made, all other line item changes proposed by other task forces will be on hold until a major revision is completed and published, and vice versa. 

Since SEMI S2 covers a wide range of topics, there are variety of task forces dealing with a different subsection in SEMI S2 (e.g., mechanical, pressure guideline, chemical exposure, control of hazardous energy, fire protection). As such, all SEMI S2 TF activities will be on hold or coordinated tightly with the SEMI S2 Interlocks Design TF to avoid conflicting revision. SEMI S2 was completely revised nearly 15 years ago.

Regardless of your region, all members are encouraged to participate in this major effort.  If you would like to participate in the TF, please contact Kevin Nguyen at [email protected].

Get Involved

SEMI Standards development activities take place throughout the year in all major manufacturing regions. To get involved, join the SEMI International Standards Program at: www.semi.org/standardsmembership.

For more information, please visit our main Web site and current events page. If you have any questions regarding SEMI Standards activities, please contact your local SEMI Standards staff.

 

Standards Watch
SEMI
www.semi.org
June 15, 2022