C.F. Wheatley

A conceptual model of a single-event gate-rupture in power MOSFETs

Proposes a physical model of hole-collection following a heavy-ion strike to explain the development of oxide fields sufficient to cause single-event gate rupture (SEGR) in power MOSFETs. It is found that the size of the maximum field and the time at which it is attained are strongly affected by the hole mobility. Oxide fields larger than the intrinsic breakdown strength of the oxide can arise from the holes collecting at the interface and their image charge in the gate electrode. These high fields persist for times of the order of picoseconds. It is not known how long these fields must persist to initiate SEGR. >

SEGR and SEB in n-channel power MOSFETs

For particular bias conditions, it is shown that a device can fail due to either single-event gate rupture (SEGR) or to single-event burnout (SEB). The likelihood of triggering SEGR is shown to be dependent on the ion impact position. Hardening techniques are suggested.

Development of cosmic ray hardened power MOSFET's

Developmental power DMOS (double-diffused metal-oxide-semiconductor) FETs were thoroughly characterized in a simulated cosmic-ray environment using heavy ions at the Brookhaven National Laboratorys tandem Van de Graaff accelerator facility. The primary failure mode encountered on FETs in this environment was susceptibility to single-event burnout. Burnout of the power DMOS FET was catastrophic. Another failure mode was single-event gate rupture. Although gate rupture is not as severe as burnout, its long-term effects are not known. Single-event gate rupture causes performance degradation due to increased gate leakage current. An increase in current can pose serious problems for applications that cannot compensate for the added performance degradation. Long-term reliability of the gate oxide may be affected, resulting in premature device failure. Numerous processing lots were fabricated to verify experimentally that each failure mode could be successfully minimized. Test results have shown that an n-channel, 150-V DMOS FET survived exposures to ions with linear energy transfers up to 80 MeV-cm/sup 2//mg. Hardening approaches are discussed, including their advantages and disadvantages in relation to the FETs performance. >

Influence of ion beam energy on SEGR failure thresholds of vertical power MOSFETs

For the first time, experimental observations and numerical simulations show that the impact energy of the test ion influences the single-event gate rupture (SEGR) failure thresholds of vertical power MOSFETs. Current testing methodology may produce false hardness assurance.

A study of ion energy and its effects upon an SEGR-hardened stripe-cell MOSFET technology [space-based systems]

Experimental observations of an improved single-event gate rupture (SEGR) hardened stripe-cell MOSFET demonstrated that ion beam energy, penetration depth, and strike angle (tilt angle) have a significant influence upon the measured SEGR failure threshold voltage.

SEGR response of a radiation-hardened power MOSFET technology

SEGR response curves are presented for eighteen different device types of radiation-hardened power MOSFETs. Comparisons are made to demonstrate the technologys insensitivity to die size, rated blocking voltage, channel conductivity, and temperature. From this data, SEGR cross-sectional area curves are inferred.

Measurement of a cross-section for single-event gate rupture in power MOSFETs

The heavy-ion fluence required to induce Single-Event Gate Rupture (SEGR) in power MOSFETs is measured as a function of the drain bias, V/sub DS/, and as a function of the gate bias, V/sub GS/. These experiments reveal the abrupt nature of the SEGR-voltage threshold. In addition, the concepts of cross-section, threshold, and saturation in the SEGR phenomenon are introduced. This experimental technique provides a convenient method to quantify heavy-ion effects in power MOSFETs.

An improved stripe-cell SEGR hardened power MOSFET technology

A new single-event gate rupture radiation-hardened power MOSFET is reported. It is based upon a well-established radiation-hardened technology described in 1996. The hexagonal cells used in prior work are replaced with a stripe-cell structure producing demonstrated performance improvements.

The effects of ionizing radiation on power-MOSFET termination structures

The effects of ionizing radiation on power-MOSFET termination structures were examined through two-dimensional simulation. A wide range of sensitivity to surface-charge density was found for various devices employing floating field rings and/or equipotential field plates. Termination structures that were both insensitive to surface charge and possessed a high breakdown voltage were identified. The results are compared with measurements made on selected structures. Insights into the design of optimum termination structures are obtained. >

Experimental evidence of the temperature and angular dependence in SEGR [power MOSFET]

The temperature and angular dependence of Single-Event Gate Rupture (SEGR) experiments, conducted on power DMOS transistors, show that a normal incident angle favors SEGR and elevated temperature is insignificant. Both the oxide and substrate response play a major role in determining the SEGR sensitivity.