Transient Charge Collection Research Articles

Investigation of laser-induced single event effect on SiGe BiCMOS low noise amplifiers

With the further development of the complementary metal-oxide-semiconductor (CMOS) technology and the silicon-germanium (SiGe) epitaxy technology, SiGe bipolar CMOS (BiCMOS) low noise amplifiers (LNAs) are widely used in the first level of radio frequency (RF) transceiver system in space. The core part of SiGe BiCMOS LNA is SiGe heterojunction bipolar transistor (SiGe HBT) which naturally possesses excellent temperature characteristic and favorable build-in total ionizing dose and displacement damage resistance without any radiation hardening. However, the single event effect caused by the transient charge collection is the bottleneck problem, restricting its application in space. In this work, laser microbeam experiments were carried out on a SiGe BiCMOS LNA in which the sensitive region of single event effect was located. The experimental results indicate that the transient charge collection of SiGe HBT is the main reason of the single event effect of SiGe BiCMOS LNA. TCAD simulations show that the ionization track caused by ion incident in CMOS region will cross the deep trench isolation (DTI) structure, generate electron-hole pairs in SiGe HBT region and cause transient charge collection. The circuit simulations by ADS show that the peak value of the transient voltage will drop sharply when the SEE pulse transient voltage crosses the capacitor between the first stage and the second stage, which indicates that the capacitor plays an important role in transmitting the transient pulses caused by single event effect. The experimental and simulation results in this work provide technical support for radiation hardening by design (RHBD) of the single event effect of SiGe BiCMOS LNA.

Analysis of Nanowire Field-Effect Transistors SET Response: Geometrical Considerations

The single-event transient (SET) response of silicon-on-insulator (SOI) tri-gate silicon nanowires is investigated using direct measurements of current transients. The impact of nanowire geometry is discussed using the major SET characteristics: duration, amplitude, and integrated value. The experimental results demonstrate the key influence of the nanowire width on the generated current transients induced by heavy ion irradiations. Both Monte-Carlo calculations of deposited energy and Technology Computer Aided Design (TCAD) simulations give evidence of the SOI tri-gate silicon nanowires ability to mitigate generated current transients. TCAD calculations are used to discuss the impact of the main nanowire geometrical parameters which include the nanowire width, thickness, and gate length, on transient charge collection mechanisms in SOI nanowire field-effect transistors (NWFET). Thin and narrow NWFET designs enhance the control of the surrounding gate over the electrostatic potential into the nanowire. The onset of floating body effects induced by heavy ion strike is reduced which mitigates the SET generation.

Impact of displacement damage on single event transient charge collection in SiGe HBTs

Abstract This paper presents an investigation into the impact of neutron-induced displacement damage on the single event transient (SET) charge collection in silicon–germanium heterojunction bipolar transistors (SiGe HBT) based on pulsed laser micro-beam experiment and technology computer aided design (TCAD) simulation. Experimental results show that the transient charge collection of the collector terminal decreases after neutron irradiation with a fluence of 5 × 1013 n/cm2 . In addition, the decrease of charge collection is more significant outside the collector–substrate (C–S) junction than inside. Combining with the TCAD simulation results, it is confirmed that the minority carrier lifetime which is shortened by neutron-induced defects plays an important role in the decrease of charge collection, and the disparity between the decreases of charge collection outside and inside the C–S junction is related to the dominating collection mechanism and transient duration.

Heavy-Ion and Laser Induced Charge Collection in SiGe Channel <formula formulatype="inline"><tex Notation="TeX">$p{\rm MOSFETs}$</tex></formula>

Heavy-ion and two-photon-absorption (TPA) experiments have been performed on ultra-thin implant-free quantum well SiGe channel pMOSFETs. Both the single-event-transient pulse magnitude and polarity can depend strongly on the location of the strike along the device channel. The polarity inversion occurs primarily because very limited transient charge collection occurs below the quantum well, as confirmed by two-dimensional TCAD simulation.

Proton-Induced Transient Charge Collection in GaAs and InAlSb/InAs-Based FETs

The single-event transient (SET) response of two different n-channel III-V field-effect transistor technologies (GaAs MESFET, InAlSb/InAs HEMT) is measured for the first time for MeV proton irradiation. The characteristics and mechanisms of the proton-induced response of these two technologies are presented and discussed in terms of previous heavy-ion and pulsed-laser measurements. The measurements show that the maximum collected charge, event cross section, pulse amplitude, and full width at half-maximum (FWHM) all increase with increasing proton energy, and decrease as the devices are biased more strongly in depletion. The results are consistent with the presence of charge-enhancement processes that are a consequence of ionization-induced hole accumulation in the substrate/buffer regions of the devices. The InAlSb/InAs HEMT measurements reveal at least an order-of-magnitude lower sensitivity to proton-induced transient generation than the GaAs MESFET in terms of both collected charge and cross section.

Modeling of transient charge collection induced by an angled single ion strike

Single-event phenomena (SEP) are common occurrences in electronic devices used in high-radiation fields such as space environments. SEP are primarily caused by the interaction between ionization tracks generated by a high-energy heavy ion and sensitive regions of a semiconductor device. In order to develop SEP tolerance devices, it is necessary to predict the amount of the collected charge at sensitive regions. In this paper, comparing the experimental results obtained from the waveform of the transient current induced by a heavy ion and from a geometrical model, we have studied the ion-induced transient charge as a function of an angle and the linear energy transfer (LET) of the incident ions.

Numerical simulation of heavy ion charge generation and collection dynamics

Describes a complete simulation approach to investigating the physics of heavy-ion charge generation and collection during a single event transient in a p-n diode. The simulations explore the effects of different ion track models, applied biases, background dopings and LET (linear energy transfer) on the transient responses of a p-n diode. The simulation results show that ion track structure and charge collection via diffusion-dominated processes play important roles in determining device transient responses. The simulations show no evidence of rapid charge collection in excess of that deposited in the device depletion region in typical funneling time frames. Further, the simulations clearly show that the device transient responses are not simple functions of the ion's incident LET. The simulation results imply that future studies should consider the effects of ion track structure and extend transient charge collection times to insure that reported charge collection efficiencies include diffusion-dominated collection processes. >

Transient charge collection from ion tracks in semiconductors

Ion-induced charge-collection transients spanning nine orders of magnitude in time resolution are presented for 1.2 and 0.1 μm gate len>h GaAs MESFETs. Measurements as a function of device bias and temperature reveal the presence of several different contributions to the charge-collection transients, ranging in time scale from picoseconds to milliseconds. The dominant charge-collection contributions at longer (> 1 ns) times are associated with trapped charged effects which modulate the channel regions of these devices. For most devices investigated, such effects account for the major fraction of collected charge, and dominate the transients detected for the 0.1 μm MBE grown devices. The significance of charge trapping effects in the SEU sensitivity of GaAs circuits is suggested and discussed.

Application of LBI techniques to the solution of the transient, multidimensional semiconductor equations

An analysis and computational procedure are developed for the solution of the coupled system of transient, multidimensional equations governing current continuity for electrons and holes, and the electrostatic potential in semiconductors. The analysis is unique in that through it the 3 × 3 coupled system is reduced to 2 × 2 coupled, parabolic system, the continuity equations, and a scalar, elliptic equation, Poisson's equation, which are solved sequentially without introducing stability restrictions or iteration. The coupled continuity equations are integrated through implementation of an LBI algorithm followed by solution for the electrostatic potential using a scalar ADI procedure. The stability and accuracy of the method are explored in one-dimension followed by application to a three-dimensional transient charge collection simulation.