December 14, 2011 -- STMicroelectronics today announced the successful production of the world's first semiconductor wafer whose dice were fully tested without contact probes. ST's advance in testing technology enables a wafer containing chips such as RFID (Radio Frequency Identification) ICs to be tested using electromagnetic waves as the sole link to the array of circuits on the wafer. Higher yields, shorter testing times and lower product cost are among the potential benefits of this approach. In addition, contactless testing allows RF circuits to be tested under conditions that are close to the real application conditions.
The new ElectroMagnetic Wafer Sort (EMWS) technology results from 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.
EMWS is an evolution of Electrical Wafer Sort (EWS), the last stage of wafer fabrication before assembly and test of the final packaged products. At this stage in the manufacturing cycle, the processed wafer contains an array of identical circuits called die. A probe card connected to Automatic Test Equipment (ATE) is moved over each of the die and, in turn, the microscopic probes make contact with test pads on the die. The ATE then performs its tests to confirm that the die is fully functional, allowing any non-functional die to be discarded before the die are assembled and packaged.
EMWS is a recent development in which the individual dice contain a tiny antenna and the ATE supplies power and communicates with the dice via electromagnetic waves. This approach reduces the number of test pads on the die, significantly shrinking the die size.
Probes are still required to supply power to test high-power products but ST's novel technique now enables fully contactless testing of low-power circuits.
"Contactless testing improves test coverage and, because the RF circuits, anti-collision protocol and embedded antenna are tested under the same conditions they will operate under in the customer's application, it will significantly enhance quality and reliability," said Alberto Pagani, Test R&D and Competitive Intelligence, a developer of the new technology.
More about EMWS
ST's contactless EMWS technology is based on a patented technique called "electromagnetic concentration/expansion." This uses a passive structure consisting of two or more antenna connected together to obtain a series resonance that acts as an electromagnetic lens that concentrates electromagnetic energy from a large surface onto a small one, such as a single die or expands the energy from a small area to a larger one. The electromagnetic concentrator/expander, which can be incorporated into a testing system, allows the communication distance (reading range) between the die and an external system such as the ATE to be increased by at least one order of magnitude. Moreover, for ultra-low-power circuits such as RFIDs, the die can be powered directly by the concentrated electromagnetic energy, achieving fully contactless testing.
Go to the STMicroelectronics website to find additional information.