Sofie Put

Geometry and Strain Dependence of the Proton Radiation Behavior of MuGFET Devices

The proton irradiation effects on n-MuGFET devices with three different geometries (single fin, wide fin and multiple fin) are studied. Also, the effect of tensile strain in the fin on the radiation behavior is investigated. A fundamental difference in the radiation behavior between the non-strained and the strained devices is found. The degradation of the strained devices is most affected by the mobility decrease of the backside transistor. The non-strained devices show a much lesser back gate mobility degradation. For these devices the creation of positive oxide traps is dominant. This shifts the onset of the back channel to lower gate voltages, inducing a transconductance increase at intermediate gate voltages. This effect is less pronounced for single fin MuGFETs. At higher gate voltage, the transconductance decreases for the strained and increases for the non-strained transistors.

Influence of Fin Width on the Total Dose Behavior of p-Channel Bulk MuGFETs

A first assessment of the total dose behavior of bulk p-multiple-gate field-effect transistors (MuGFETs) is reported, and special attention is given to the effect of the fin width on the radiation behavior. It was found that the effect of radiation-induced traps in the shallow trench isolation is larger when the fin width decreases. This is in contrast to the total dose behavior of SOI MuGFETs.

Proton-Induced Mobility Degradation in FinFETs With Stressor Layers and Strained SOI Substrates

Proton irradiation effects on fin-type field effect transistors (FinFETs) are examined from the viewpoint of their electrical-performance parameter of mobility. They are fabricated with various types of combination of strain/stress techniques to control their mobilities. The base stress level is globally modified by means of nonstrained or strained silicon-on-insulator wafers. Some process splits, additionally, receive a local strain tuning with a contact-etch-stop layer (CESL). Both n- and p-type FinFETs are evaluated. A 60-MeV proton irradiation with a fluence of 1012 p/cm2 leads to mobility changes for wide-fin samples: degradation for n-type and enhancement for p-type. These mobility variations can be explained with a change in the number of charged interface traps at the Si and buried-oxide interface. Narrow-fin devices exhibit mobility changes unnoticeable statistically. A comparison with previous studies indicates an elevated source/drain structure plays a role in this mobility preservation. Although the mobility is kept intact in the narrow-fin samples, a close investigation based on a two channel-component model can reveal noticeable mobility variations at a component level. In this study, observed mobility changes are complex depending on the adopted stress techniques as well as process parameters and cannot be explained by the stress levels simply.

Microdose and Breakdown Effects Induced by Heavy Ions on Sub 32-nm Triple-Gate SOI FETs

We studied the permanent effects of heavy-ion strikes on decananometer triple-gate SOI devices. We highlighted the role of the geometry and the three-dimensional architecture in the response to heavy ions. Heavy-ion strikes in state-of-the-art Triple-Gate FETs may have measurable permanent effects, due to microdose in the buried oxide, breakdown of the gate oxide, or interface state generation in the side oxide/body interface. This last effect is particularly interesting since it is related to the verticality of multigate transistors.

Influence of Back-Gate Bias and Process Conditions on the Gamma Degradation of the Transconductance of MuGFETs

The gamma radiation-induced variation of the transconductance in the subthreshold region is studied for different back-gate voltages and for different kinds of SOI MuGFETs: devices with and without Selective Epitaxial Growth (SEG) and 45° rotated transistors. Wide fin devices show a larger degradation when the back-gate is grounded. The back-channel of narrow fin transistors, on the other hand, needs to be inverted before degradation in the transconductance is observed. The radiation behavior of the transconductance is similar for devices with and without SEG. It is shown that the maximum variation in transconductance correlates with the mobility for narrow fin devices. This mobility varies when the transistor is rotated. For wide fin devices this correlation is not so strong.

Effect of Airgap Deep Trench Isolation on the Gamma Radiation Behavior of a 0.13

The effect of an airgap deep trench isolation on the gamma radiation behavior of a 0.13 mum SiGe NPN HBT technology is studied with the help of in-situ measurements. The incorporation of this deep trench isolation in the technology leads to a lower degradation of the transistor during irradiation as well in forward-mode as in reverse-mode operation. A possible explanation is briefly mentioned.

\mu{\hbox {m}}

The effect of airgap deep trench isolation on the radiation behavior of a 0.13 mum NPN SiGe:C HBT is studied and compared with standard components with conventional junction isolation. Proton and gamma irradiations are performed. The only effect discerned on this technology after a proton irradiation of 7 kGy is a decrease in collector current at higher base-emitter voltages. After 100 kGy gamma irradiation, no change in collector current is observed. However, the base current increases severely at lower base-emitter voltages. In forward-mode the base current degradation of devices featuring deep trench isolation is higher compared to conventional devices. In reverse-mode the effect is opposite: degradation is higher for conventional devices. The difference in degradation between the two isolation types is smaller in forward-mode operation.