Double modulated thermoreflectance microscopy of semiconductor devices

Abstract

Photothermal microscopy based on combined optical and electrical excitation has been applied to insulating lines and conducting channels on SIMOX mesas prepared by focused ion beam implantation. The double excitation technique permits imaging of electrical properties of the implanted structures yielding complementary information achievable by a single excitation defect tracing. In addition, the contrast of the images of implanted structures can be increased considerably. The best contrast for the observation of insulating lines adjacent to a conducting channel has been achieved by recording the modulated reflectance signal at the fourth harmonic of the modulation frequency used for electrical and optical excitation. The contrast enhancement is found to be mainly due to thermal origins caused by the photoinduced currents, which can act as an additional heat source.