External electro-optic probing of millimeter-wave integrated circuits

An external, noncontact electrooptic measurement system, designed to operate at the wafer level with conventional wafer probing equipment and without any special circuit preparation, has been developed. Measurements have demonstrated the system´s ability to probe continuous and pulsed signals on microwave integrated circuits on arbitrary substrates with excellent spatial resolution. In addition, it has been shown that the electrooptic probe tip can measure voltage values on an integrated circuit chip, even in areas where physical contact made by a test instrument would be inappropriate. Experimental measurements on a variety of digital and analog circuits, including a GaAs selectively doped heterostructure transistor prescaler, an NMOS silicon multiplexer, and a GaAs power amplifier MMIC (monolithic microwave integrated circuit) are reported.<>