Published 01-Oct-2003

Abstract
For years, it has been common to run a test at wafer and then exactly the same test again at package. This article shows how one company took a detailed look at the wafer/package test mix and adjusted it to reduce cost while retaining quality:

FOR MODERN TECHNOLOGIES, it is common to conduct tests at various conditions to ensure adequate defect detection and to satisfy quality requirements. Several studies demonstrate that stimulating and detecting some defects requires environmental variation. The variable is typically voltage, temperature, or frequency. Li and McCluskey reported examples of voltage-sensitive defects, which require very-low-voltage tests to detect.

The voltage dependency of at-speed performance is well-known. At the same time, every design must operate over the specified voltage or temperature range. Because changing temperature in the middle of a test suite is impractical, at least two flows are necessary — unless you can effectively vary a parameter other than temperature...