What is semiconductor test equipment (IC tester)?

Semiconductor test equipment (IC tester), or automated test equipment (ATE), is a system for giving electrical signals to a semiconductor device to compare output signals against expected values for the purpose of testing if the device works as specified in its design specifications.
Testers are roughly categorized into logic testers, memory testers, and analog testers. Normally, IC testing is conducted at two levels: the wafer test (also called die sort or probe test) that tests wafers, and the package test (also called final test) after packaging. Wafer testing uses a prober and a probe card, while package testing uses a handler and a test socket, together with a tester.