Yield Excursion is a sudden, unexpected drop in manufacturing yield below historical baselines, indicating a process problem requiring immediate investigation.

What Is a Yield Excursion?

• Definition: Yield drops >3σ below historical mean
• Duration: May affect single lots or persist for days/weeks
• Root Causes: Equipment drift, contamination, material variation
• Response: Stop production, quarantine affected lots, investigate

Why Yield Excursion Response Matters

Every hour of delayed response multiplies affected wafers. Fast detection and root cause analysis minimize financial impact ($100K+ per hour in modern fabs).

<svg viewBox="0 0 376 283" xmlns="http://www.w3.org/2000/svg" style="max-width:100%;height:auto" role="img"><rect x="0" y="0" width="376" height="283" rx="12" fill="#0d1117"/><g font-family="ui-monospace,SFMono-Regular,Menlo,Consolas,&quot;Liberation Mono&quot;,monospace" font-size="14"><text xml:space="preserve" x="20" y="31.7"><tspan fill="#c9d1d9">Yield Excursion Timeline:</tspan></text><text xml:space="preserve" x="20" y="50.7"><tspan fill="#c9d1d9">         Excursion occurs</tspan></text><text xml:space="preserve" x="20" y="69.7"><tspan fill="#c9d1d9">              </tspan><tspan fill="#6e7681">↓</tspan></text><text xml:space="preserve" x="20" y="88.7"><tspan fill="#c9d1d9">Yield </tspan><tspan fill="#6e7681">───────</tspan><tspan fill="#c9d1d9">╲</tspan></text><text xml:space="preserve" x="20" y="107.7"><tspan fill="#c9d1d9">100%          ╲</tspan></text><text xml:space="preserve" x="20" y="126.7"><tspan fill="#c9d1d9"> 90%           ╲</tspan><tspan fill="#6e7681">────────────</tspan></text><text xml:space="preserve" x="20" y="145.7"><tspan fill="#c9d1d9"> 80%                        Recovery</tspan></text><text xml:space="preserve" x="20" y="164.7"><tspan fill="#c9d1d9">              </tspan><tspan fill="#6e7681">↑</tspan><tspan fill="#c9d1d9">        </tspan><tspan fill="#6e7681">↑</tspan><tspan fill="#c9d1d9">        </tspan><tspan fill="#6e7681">↑</tspan></text><text xml:space="preserve" x="20" y="183.7"><tspan fill="#c9d1d9">           Detect   Root     Fix</tspan></text><text xml:space="preserve" x="20" y="202.7"><tspan fill="#c9d1d9">           (hours)  Cause  Implement</tspan></text><text xml:space="preserve" x="20" y="221.7"><tspan fill="#c9d1d9">                   (days)</tspan></text><text xml:space="preserve" x="20" y="240.7"><tspan fill="#c9d1d9">           </tspan></text><text xml:space="preserve" x="20" y="259.7"><tspan fill="#c9d1d9">Fast detection saves thousands of wafers</tspan></text></g></svg>

Excursion Investigation Steps: 1. Split data by equipment, chamber, recipe 2. Check inline metrology trends 3. Review PM logs and part changes 4. Compare defect signatures to known patterns 5. Run DOE to confirm hypothesis