L. Cattani

Reliability physics of compound semiconductor transistors for microwave applications

Abstract This paper reviews the reliability problems of compound semiconductor transistors for microwave applications. These devices suffer from specific failure mechanisms, which are related to their limited maturity, with the exception of the GaAs MESFETs, which exhibit a stable technology and an assessed reliability. The metallizations employed in high electron mobility transistors (HEMTs) already benefit from this assessment. However, HEMT are affected by concerns related to hot carriers and impact ionization. The trapping of carriers and the generation of defects in the different layers are responsible for the observed instabilities. The stability of the base dopant is the main reliability concern for heterojunction bipolar transistors (HBTs). Beryllium outdiffuses from the base into the emitter and causes device degradation. Carbon has a lower diffusivity, but is affected by the presence of hydrogen, which prompts gain variations. Finally the hot carriers reliability concern in SiGe HBTs is briefly reviewed.

Lifetime extrapolation for IGBT modules under realistic operation conditions

Abstract In this paper a systematic approach is presented for extrapolating the lifetime due to bond wire lift-off in IGBT modules submitted to cyclic loading. Application profiles of the device are considered, as they are usually encountered in real current converters for railway traction systems. The proposed lifetime prediction scheme is based on the principle of the linear accumulation of the fatigue damage and takes into account the redundancy of the bond wires.

Cathodoluminescence evidence of stress-induced outdiffusion of beryllium in AlGaAs/GaAs heterojunction bipolar transistors

Cathodoluminescence (CL) spectroscopy has been used for the first time in order to detect the base-dopant outdiffusion induced by current stress in AlGaAs/GaAs Be-doped heterojunction bipolar transistors (HBTs). The results show that diffusion of base dopant along the growth direction of the HBT structure occurs during the stress and this conclusion is confirmed by SIMS analysis. Integrated CL intensity variations induced by the stress suggest that the mechanism of recombination-enhanced impurity diffusion is responsible for diffusion of Be.

Reliability investigation of InGaP/GaAs HBTs under current and temperature stress

Abstract The reliability of InGaP/GaAs N–p–n heterojunction bipolar transistors (HBTs) with different base metal contact systems (Au/Zn/Au, Ti/Au, Ti/Pt/Au and the novel Ti/ZrB2/Au) under current and temperature stress is studied in this paper. We further report results of current stress on three p-GaAs doping impurities namely Zn, Be and C. The effect of O+/H+ and O+/He+ ions, used in the fabrication of planar self-aligned HBTs, is also investigated in the stability of device dc current gain. The instability phenomena typical of each factors and their effects on the HBT characteristics are reported.

Study of degradation mechanisms in compound semiconductor based devices by SEM-cathodoluminescence

Abstract This papers reports on the microcharacterization of devices for optoelectronic and high-speed electronic applications by spectrally resolved cathodoluminescence. The advantages offered by the high lateral resolution, monochromatic imaging and depth resolved spectral analysis of the technique are presented. In particular, Inp based semiconducting optical amplifiers and GaAs based pump lasers for optical fiber communications are characterized from the point of view of compositional inhomogeneities and defect generation in the active regions. GaAs based heterojunction bipolar transistors and high electron mobility transitors are studied to respectively reveal Be outdiffusion from the base and break down walkout after bias aging. GaAs based solar cells are also investigated to show the correlation between dislocations and impurity gettering. Finally the limits of the technique are briefly discussed.

Reliability of compound semiconductor devices

This paper reviews the reliability problems of compound semiconductor devices. These devices suffer from specific failure mechanisms, which are related to their limited maturity. Only the GaAs MESFETs exhibit a stable technology and an assessed reliability. The metallizations employed in HEMTs already benefit from this assessment. However, HEMTs are affected by problems related to hot carriers and impact ionization, due to the high electric fields in the channel. The trapping of carriers and the generation of defects in the different layers are responsible for the observed instabilities. The stability of the base dopant is the main reliability concern for HBTs. The Be outdiffuses from the base to the emitter and causes degradation in the device performances. The C exhibits a lower diffusivity, but it is affected by the presence of H, which causes gain variations.

Failure mechanisms in compound semiconductor electron devices

Publisher Summary This chapter reviews the failure mechanisms that affect advanced compound semiconductor-electron devices such as high electron mobility transistors (HEMTs) and heterostructure bipolar transistors (HBTs). In the chapter, some considerations are presented for indium phosphide (InP)-based devices and for silicon-germanium (SiGe) HBTs. Both linear and power amplification requires that devices be biased in the saturation region and satisfactory output power to be delivered to the load—the FET bias point and its radio frequency (RF) sweep must be pushed to drain-source voltage values as high as applicable. The main factor that limits the device safe operating area in the high drain-source voltage, low drain current corner of the output plane is typically the onset of hot-electron and impact ionization effects and the attendant-degradation mechanisms. The study of metal-related reliability in HEMTs has benefited from the long-standing tradition of gallium arsenide (GaAs) MESFETs; therefore, relatively few specific papers have been published, and most problems have been tackled and solved. Three main reliability concerns are treated in the chapter: metal-related issues, hot-electron and high-field conditions, and hydrogen poisoning.

Teaching Reliability in Microelectronics

In this paper three different experiences of teaching quality and reliability in electronics are presented.

Pulsed current stress of Berillium doped AlGaAs/GaAs HBTs

The major concern for reliability of Berillium doped HBTs is the diffusion of the base dopant towards the emitter. This degradation can be enhanced by the device self-heating and/or by REID mechanism. In order to separate the thermal and REID components to the Berillium outdiffusion we performed a pulsed current stress on AlGaAs/GaAs HBTs. In this paper we report on results obtained with different values of the duty cycles for this current.

Cathodoluminescence investigation of stress-induced beryllium outdiffusion in AlGaAs/GaAs HBTs

In this study cathodoluminescence spectroscopy has been used for the first time in order to detect the base dopant outdiffusion induced by current stress in AlGaAs/GaAs Be-doped HBTs. The results provide evidence for base dopant diffusion along the growth direction of the HBT structure and suggest that the REID mechanism may be responsible. Therefore, cathodoluminescence can be used as a nondestructive technique to study beryllium outdiffusion.