Observation of single-ion induced charge collection in diode by a heavy ion microbeam system

摘要

In order to study the phenomena of single event upset (SEU), investigations of properties of single event transient current (SETC) in micro-scale semiconductor devices are in progress at the JAERI Takasaki heavy ion microbeam single-ion hit system. Irradiation damage effects are noticeable problems in SETC measurement, especially when a device is irradiated continuously by high-energy heavy ions in an area of 1 μm level. On the other hand, confined irradiation damages in such narrow localized area can be a useful landmark to indicate how large area or region of the device to be concerned with charge collection events. This information is very important for designing micro-scale devices with high SEU tolerance. When a micro-scale test device of silicon carbide (SiC) pn diode was irradiated by single 12 MeV nickel ions with a beam spot size of 1 μm in FWHM, successive irradiation damage effects were observed in the form of attenuation of the current pulse heights and the amount of total charge collected. The lateral extent of charge collection induced by every ion injection was evaluated by analyzing these data. The extent of charge collection in depth direction will be also discussed in conjunction with the thickness of the sensitive layer and the range of the projectiles.