Failure analysis

Notes

Sequence discipline is everything, because the destructive steps that reveal the defect also destroy the evidence for every earlier technique.

Overview

Failure analysis (FA) is the step-by-step investigation of a chip or package that has failed, to find exactly where and why it failed so that the cause can be removed. Failed parts come from qualification tests, production test and customer returns. The work moves from harmless external checks to destructive ones, because each step that opens up the part destroys evidence that earlier steps could have used.

How it works

It starts without damage. Engineers confirm the failure electrically, inspect the part, use X-ray imaging to look inside the package, and use scanning acoustic microscopy to find cracks, voids and layers that have come apart.

Next comes fault isolation: finding where on the die the defect lies. Laboratories use optical fault isolation systems, lock-in thermography, which locates faint heat sources, and electron-beam probing, followed where needed by nanoprobing of individual transistors.

Then comes physical analysis. The package is opened to expose the die, which may be examined layer by layer; a focused ion beam cuts precise cross-sections or thin samples through the suspect spot for imaging in scanning and transmission electron microscopes, with X-ray spectroscopy to identify materials. The report names the failure mechanism and, with the wider team, the root cause and corrective action.

Examples

• A customer-returned part analysed to find whether it failed from damage in use or from a manufacturing defect.
• X-ray and scanning acoustic microscopy checking a package for cracks, voids or delamination.
• Lock-in thermography locating a hot spot in a failing part before physical analysis.
• A thin sample prepared with a focused ion beam for imaging in a transmission electron microscope.
• Nanoprobing individual transistors on the die to find the one that fails.

Why it matters

FA is how a company learns from failures instead of repeating them, and for automotive and industrial customers it is a contractual obligation. Failure analysis engineers and technicians do the work, while reliability engineers, product engineers and quality teams act on the findings.

In the chip lifecycle, FA supports bring-up debug, qualification, yield ramp and field returns, and so continues for as long as a product ships.

It matters most to:

Related terms

• EFA
• PFA
• RCA
• Decapsulation

Where it appears on the Hub

Used on 191 pages of the Hub. In each group, the pages that mention it most come first.