Wafer testing is a critical step in ASIC design and manufacturing process and forms part of the fabrication phase.
What exactly happens in this step and what technology is employed in its execution? This post takes a quick look.
Overview of Wafer Testing
Referred to by different names, such as the Electronic Die Sort (EDS) and Circuit Probe (CP), wafer testing is an electrical test performed before a wafer is sent for die preparation, to test the electrical connectivity of individual ICs (dies) that are present on the wafer.
The test applies special test patterns using anautomated testing equipment (ATE) called wafer prober. The content and sequence of these test patterns are collectively called the test program.
During wafer testing, the wafer to be tested is loaded on the wafer prober, where it is firmly anchored onto a vacuum-sealed wafer chunk for the testing process to begin. The vaccum seal ensures the wafer does not move from its position during testing. A probe card, mounted onto the wafer prober, establishes electrical contact with the wafer and scans it for connectivity anomalies. The wafer prober also comes equipped withan optical system for pattern recognition to ensure the wafer is properly aligned and any potential alignment artifacts are eliminated.
Wafers that pass the wafer test are sent for die preparation and packaging. Those wafers that fail the test are removed from the manufacturing line and tested further to validate they are defective. Once confirmed, these defective wafers are used for providing spare components for the ASIC manufacturing process.
The information regarding wafers that are fit for assembly and which need to be discarded is stored in a wafer map, a file which is electronically sent to the assembly apartment for sorting the processed wafers.
After an ASIC has been fabricated and packaged, it is tested one final time in a step known as IC phase testing. This test helps keep defective packages from being used in devices, saving unnecessary expenses inrecalls and re-assemblies.
At ADSANTEC, we provide ASIC design and development services. Having helped multiple clients design and develop custom ASICs for their specialty products, our project portfolio spans over a decade of experience. Get in touch with us today to learn how we can help you design a better product for your customers.