Keithley 2871 Probe Card WP free download

File name 2871 Probe Card WP.pdf

WHITE PA P E R Probe card considerations when migrating to new testers Yang Pan Keithley Instruments, Inc. Introduction For on-wafer automatic parametric testers, the probe card is the interface between the test head and the device pads on the wafer, so it is key to achieving a successful electrical measurement. The probe cards specified by each of the two dominant parametric tester companies, Agilent and Keithley Instruments, are incompatible with the other's testers. Therefore, when fabs change to a new tester type, such as from an Agilent 4000 Series tester to a Keithley S600 Series tester, they must also migrate to new probe card types. To ensure good (i.e., correlated) parametric tests, a minimal, repeatable, and reliable pin-to-pad contact resistance is a necessary prerequisite. Test system specifiers must select a suitable probe card to fulfill these requirements. This White Paper addresses two major considerations: 1) how to select and specify a suitable probe card, and 2) how to use the probe card properly. Many measurement results are presented. For the sake of simplicity, we will assume that the new tester will be used to probe the same wafer types with the same tests as the old one was. Probe card selection Obviously, the new card's probe pin count, pad pitch, leakage current, test temperature, and frequency limit specifications should be the same as those of the previous probe card. In addition to these basic aspects, the following list of parameters should be considered. All the listed parameters affect contact resistance, current handling capability, and bond pad scrub characteristics. Card Keithley Instruments, Inc. 28775 Aurora Road Cleveland, Ohio 44139 (440) 248-0400 Fax: (440) 248-6168 www.keithley.com specifiers should specify the same parameters for the new card as the old probe card to ensure proper correlation of old and new tester results. 1. Needle material. The needle metallurgy must be compatible with the device pad metallurgy. Is long needle life more desirable than lower contact resistance? Is probe pad damage an issue with multiple probing touchdowns at a site (i.e., is a softer need