LONDON – European chip company STMicroelectronics NV has said it has produced the first wafer on which the die were fully tested wirelessly and without the use of contact probes.
The electromagnetic wafer sort (EMWS) technology was applied to a wafer of RFID (Radio Frequency Identification) ICs. It was developed in an R&D project called UTAMCIC (UHF TAG Antenna Magnetically Coupled to Integrated Circuit), led by Alberto Pagani, Giovanni Girlando and Alessandro Finocchiaro from STMicroelectronics, and Professor Giuseppe Palmisano from the University of Catania.
Electrical wafer sort is the last stage of wafer fabrication prior to assembly and test of packaged ICs. Conventional a probe card connected to automatic test equipment (ATE) makes contact with the bond pads on each die in turn and runs a series of tests. Under EMWS each die contains an antenna and the ATE supplies power and communicates with the IC wirelessly.
In some applications this can remove the need for dedicated test pads and reduce die area.
ST said that limitations in the amount of power that can be transmitted wirelessly means that some ICs will still require contact probes but that EMWS was applicable to low-power ICs.
EMWS make use of a focusing technique that can use multiple antenna to concentrate electromagnetic energy from across the wafer to the a small area, such as a single die. The Electromagnetic Concentrator/Expander allows the communication distance between the die and an external system such as the ATE to be increased by at least one order of magnitude.
Contactless testing also reduces the test cycle time because it reduces wafer movement and enables parallelism. Moreover, it increases yield by eliminating the pad damage that occasionally occurs during standard contact testing, ST said.