Control Plan

Control plan is a comprehensive document that specifies all quality controls, inspection methods, and reaction plans for every process step in semiconductor manufacturing — serving as the master recipe for how product quality is monitored, maintained, and protected from wafer start through final test and shipment.

What Is a Control Plan?

• Definition: A living document that lists every process parameter to be controlled, the control method, measurement technique, sampling frequency, specification limits, and reaction plan for out-of-specification conditions.
• Standard: Required by IATF 16949 (automotive), AS9100 (aerospace), and widely used in semiconductor manufacturing as a quality management best practice.
• Scope: Covers the entire manufacturing flow — incoming material inspection, each fab process step, assembly, packaging, final test, and outgoing quality.

Why Control Plans Matter

• Consistency: Ensures every shift, every operator, and every tool applies the same quality controls — preventing variation in how quality is monitored.
• Reaction Speed: Pre-defined reaction plans enable immediate, consistent response to out-of-control conditions — no waiting for engineering decisions.
• Customer Requirement: Major semiconductor customers (automotive OEMs, Apple, Qualcomm) require documented control plans as a qualification prerequisite.
• Audit Trail: Provides objective evidence for quality auditors that all critical parameters are controlled throughout manufacturing.

Control Plan Elements

• Process Step: Each manufacturing operation (CVD, etch, litho, CMP, implant, test, etc.).
• Product/Process Characteristic: The specific parameter being controlled (film thickness, CD, overlay, particle count, etc.).
• Specification/Tolerance: The acceptable range for each characteristic — with LSL (Lower Spec Limit) and USL (Upper Spec Limit).
• Measurement Method: The tool and technique used to measure each characteristic — ellipsometry, SEM, scatterometry, electrical test, etc.
• Sampling Plan: How many wafers/sites measured and how often — every wafer, lot sampling, or periodic monitoring.
• Control Method: SPC charts, automated FDC monitoring, 100% inspection, or periodic audit.
• Reaction Plan: Specific steps to take when a parameter goes out of control — stop production, quarantine, reinspect, containment, engineering review.

Control Plan Phases

Control plans are the operational backbone of semiconductor quality management — translating process knowledge and customer requirements into specific, actionable controls that protect product quality at every step from wafer start to customer delivery.