Thermal microscopy of active semiconductor devices.

摘要

Thermal effects in semiconductor electronic and optoelectronic devices are literally a hot topic. Exacerbated by the increasingly fine scale of modern micro-structures, problems can range from shifts in device characteristics, long term reliability issues, up to catastrophic device failure. Quite simply, without consideration of thermal management, most modern semiconductor devices will fail. Thermal measurement techniques are equally important to provide feedback to the design engineers. Many methods can be employed, but high-resolution thermal measurements on the submicron scale of modern devices is non-trivial. After reviewing different techniques, the non-contact thermoreflectance technique is used for investigating thermal phenomena in active semiconductor devices. With the use of visible illumination the spatial resolution is improved over typical infrared techniques. Work progressed from laser point measurements to line scans, to direct thermoreflectance imaging acquired with a high resolution PIN array camera with custom-designed 256-channel lock-in amplifier system. Key results include measurements of cooling distribution in SiGe, SiGeC and InP-based heterostructure thermionic micro-coolers, thermal runaway in electroabsorption modulators, heating distribution in distributed feedback lasers, and the heat transfer across a single nano-wire. In addition, using a below bandgap energy laser, thermoreflectance has been demonstrated through several hundred microns thick substrate, allowing for thermal measurements of devices from the backside. This thesis describes the design of the thermoreflectance imaging system, the physics behind the effect and results obtained on various micro-scale devices.