From the Desk of Lewis Bass

Welcome back to “Ask Lewis Bass,” where we tackle real-world compliance questions from safety engineers, product designers, and equipment builders wrestling with tricky regulatory gaps.

This week’s submission comes from someone we’ll call Process Engineer Paul, who is deep in a SEMI S2 project and bumped into a snag with the SEMI S8 ergonomics section: specifically around the height and location of his machine’s emergency off control.

Question:

Hi Lewis Bass,

We’re finalizing the design on a new piece of semiconductor equipment and working through our internal SEMI S2 compliance checklist. When we got to the ergonomics section, otherwise known as the SEMI S8, we flagged a non-compliance issue for our emergency off button.

Our concern is this: we don’t want the SEMI S8 EMO button location or height requirement to force us into a design that interferes with how operators interact with the machine or how the tool integrates into the line.

Are there any acceptable alternatives we can pursue if our design cannot accommodate this positioning as required in SEMI S8 to be compliant to this standard?

– Process Engineer Paul

Lewis Bass:

Hi Paul,

SEMI standards, including the ergonomics guidance in SEMI S8 treat critical controls like the emergency off (EMO) button as safety-critical ergonomic elements. The idea isn’t arbitrary: if someone needs to shut the machine down because of an impending hazard, that control should be:

• Visible and unmistakable (typically a red, mushroom-head button on yellow background), and

• Accessible without awkward reach or excessive movement.

Now, regarding your question about acceptable alternatives for achieving SEMI S8 compliance outside of strictly following the guidelines (and the exact measurements): this is where engineering judgment and creative compliance strategy come in.

There are legitimate reasons a machine’s layout might not comfortably allow a control positioned exactly per the “textbook” height/axis. For example, tools integrated into tight process lines and operator stations offset due to line footprints, can sometimes make adhering to SEMI S8 EMO button placement very difficult if not impossible. In those situations, engineers performing this evaluation sometimes justify this inability to conform by:

a. Re-framing the Control as “Operator Reach-Critical”
If the design intent is that personnel are never positioned where they need to reach the EMO, you can pair the button with alternative accessible locations e.g., near the operator interface panel and at maintenance access points and argue that both satisfy the intent of the SEMI ergonomics rule.

b. Make a Risk-Based Justification
Rather than saying “we can’t meet the height,” the design team should demonstrate why the button location minimizes ergonomic and safety risk while maintaining rapid accessibility. That often means documenting:

• Workstation layouts

• Human reach envelopes

• Measurement data showing that the chosen location is within comfortable reach for 95%+ of operators

This encourages approval from you client’s EH&S department instead of a hard rejection.

Paul, I hope this gives you a path forward that satisfies both your design intent and the safety expectations behind SEMI’s ergonomics guidance, including that often-debated SEMI S8 EMO button placement. Get ahead of this while your CAD files are still editable; it’s easier than arguing with an inspector after the first prototype ships!

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