Fault isolation uses terahertz time-domain reflectometry technique

The most advanced conventional time-domain reflectometry (TDR) techniques using electrical pulses can isolate electrical-circuit faults (open or short) with 50 GHz bandwidth and 250 μm resolution, though resolutions achieved are often significantly poorer. However, a new technique developed by Intel (Chandler, AZ) researchers and TeraView (Cambridge, England) is the first to combine electro-optics and terahertz pulses in a nondestructive electro-optical terahertz pulse-reflectometry (EOTPR) technique that operates at up to 2 THz with resolution of 10 μm for improved fault isolation and failure analysis process-flow studies.

The method uses 100 fs laser pulses to generate high-speed electrical pulses that propagate into a device under test (DUT). The femtosecond laser output is split into the excitation beam and a probe beam that acquires the reflected signal from the DUT. The excitation beam enters the electro-optic sampling head and generates the electrical pulse that enters the DUT, which is then reflected back through the electro-optic sampling head and the electro-optic crystal for detection. The device can measure faults at package distances of up to 150 mm with a signal-to-noise ratio of 64 dB without averaging. The system has many potential applications, including the inspection of advanced packaging for the semiconductor industry, where it can play a significant role in fault isolation and quality assurance. Contact Yongming Cai at [email protected].