Comparison of total dose effects on SiGe heterojunction bipolar transistors induced by different swift heavy ion irradiation

Abstract

The degradations in NPN silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) were fully studied in this work, by means of 25-MeV Si, 10-MeV Cl, 20-MeV Br, and 10-MeV Br ion irradiation, respectively. Electrical parameters such as the base current (I B ), current gain (β ), neutral base recombination (NBR), and Early voltage (V A ) were investigated and used to evaluate the tolerance to heavy ion irradiation. Experimental results demonstrate that device degradations are indeed radiation-source-dependent, and the larger the ion nuclear energy loss is, the more the displacement damages are, and thereby the more serious the performance degradation is. The maximum degradation was observed in the transistors irradiated by 10-MeV Br. For 20-MeV and 10-MeV Br ion irradiation, an unexpected degradation in I C was observed and Early voltage decreased with increasing ion fluence, and NBR appeared to slow down at high ion fluence. The degradations in SiGe HBTs were mainly attributed to the displacement damages created by heavy ion irradiation in the transistors. The underlying physical mechanisms are analyzed and investigated in detail.

Improved high-frequency equivalent circuit model based on distributed effects for SiGe HBTs with CBE layout

“…Owing to its special base structure, SiGe HBTs show a built-in multi-Mrad total dose hardness with no intentional hardening. [8][9][10] However, single-event effects (SEE) re-main a serious problem, with recent results demonstrating a low linear energy-transfer threshold and high saturated crosssections. [11][12][13][14] A reduction in the sensitive area enclosed by deep trench isolation is considered an effective method of improving the net upset cross section.…”

“…[11,12] Furthermore, when the transistors are exposed to the space-energetic particle environment, the distributed effect is more significant because the irradiation damages are generally not uniformly distributed throughout the whole transistor structure. [8] Therefore, it is necessary to investigate the small-signal equivalent circuit based on the distributed effects for SiGe HBTs with a CBE layout.…”

Extraction of temperature dependences of small-signal model parameters in SiGe HBT HICUM model

“…Because of its excellent performance and compatibility with conventional Si CMOS processing, SiGe HBT technology has recently received a great deal of attention in radio frequency (RF), microwave and extreme environment applications. [1,2] Since the existence of bandgap-engineering in the base region, the narrowed-bandgap induced by the Ge profile retards the classical problems associated with cooling conventional transistors, such as base freezeout, carrier diffusivity and mobility degradation. [3][4][5] As a consequence, nearly all the transistor metrics improve with temperature decreasing, which enables SiGe HBT to operate well in a low temperature range.…”