Semiconductor Manufacturing Metrology & Inspection – 101

A Brief Basic Tutorial

Why It’s Important

This overview is for readers who may be new to metrology and inspection or for those who would like a refresher. Metrology and inspection is an increasingly significant part of semiconductor manufacturing, comprising up to 40% of the manufacturing process.

Metrology and inspection are processes of measurement and observation that use defined specifications, the confirmation of these specifications during production, and application the results of these measurements to make necessary adjustments to the production process and to the quality assurance of individual items produced.

The Process

Metrology and inspection, defect review, analysis, and classification combine to monitor and control the quality of stages in the production flow. Metrology processes determine if physical and electrical specifications are met at each step of production.

Measurements and inspections occur at key points in each of the three main phases of semiconductor manufacturing:

1. Wafer Manufacturing: cutting and thinning of wafers from silicon ingots
2. Wafer Fabrication: forming circuits on the wafer
3. Assembly & Packaging: cutting, wiring and encapsulating the die

Defects are classified and filtered to identify those that are significant.  Significant defects are addressed by changes to the production process and/or by scrapping of defective items.  Defects are identified as early as possible to avoid time consuming and otherwise costly propagation of defects further into the production sequence.

Metrology and inspection tools include optical and electronic beam techniques. Optical devices include brightfield and darkfield.  E-beam devices comprise about one fourth share of the techniques, and that share has been steady over several decades. Each technique has its relative advantages.  

The Future

Defect inspection and review techniques are approaching their fundamental limits. Incremental improvements to existing tools will not be sufficient.

More advanced techniques with promise are:  ellipsometry, scatterometry, interferometry, near-field (sub-wavelength), higher speed transmission electron microscopy, scanning probe microscopy, neuromorphic processing and artificial intelligence systems.