Challenges related to radiation hardening CMOS technologies with shallow-trench isolation are explored. Results show that trench hardening can be more difficult than simply replacing the trench isolation oxide with a hardened field oxide.

Large-scale three-dimensional (3-D) device simulations, focused ion microscopy, and broadbeam heavy-ion experiments are used to determine and compare the SEU-sensitive volumes of bulk-Si and SOI CMOS SRAMs. Single-event upset maps and cross-section curves calculated directly from 3-D simulations show excellent agreement with broadbeam cross section curves and microbeam charge collection and upset images for 16 K bulk-Si SRAMs. Charge-collection and single-event upset (SEU) experiments on 64 K and 1 M SOI SRAMs indicate that drain strikes can cause single-event upsets in SOI ICs. 3-D simulations do not predict this result, which appears to be due to anomalous charge collection from the substrate through the buried oxide. This substrate charge-collection mechanism can considerably increase the SEU-sensitive volume of SOI SRAMs, and must be included in single-event models if they are to provide accurate predictions of SOI device response in radiation environments.

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Floating-gate silicon-oxygen-nitrogen-oxygen-silicon (SONOS) transistors can be used to train neural networks to ideal accuracies that match those of floating-point digital weights on the MNIST handwritten digit data set when using multiple devices to represent a weight or within 1% of ideal accuracy when using a single device. This is enabled by operating devices in the subthreshold regime, where they exhibit symmetric write nonlinearities. A neural training accelerator core based on SONOS with a single device per weight would increase energy efficiency by 120×, operate 2.1× faster, and require 5× lower area than an optimized SRAM-based ASIC.

We wish to report in this paper a study of the effective mass (m * ) in thin-oxide Si-metal-oxidesemiconductor field-effect-transistors, using the temperature dependence of the Shubnikov-de Haas (SdH) effect and following the methodology developed by J.L. Smith and P.J. Stiles, Phys. Rev. Lett. 29, 102 (1972). We find that in the thin oxide limit, when the oxide thickness dox is smaller than the average two-dimensional electron-electron separation r, m * is still enhanced and the enhancement can be described by m * /mB = 0.815 + 0.23(r/dox), where mB = 0.195me is the bulk electron mass, me the free electron mass. At ns = 6 × 10 11 /cm 2 , for example, m * ≃ 0.25me, an enhancement doubles that previously reported by Smith and Stiles. Our result shows that the interaction between electrons in the semiconductor and the neutralizing positive charges on the metallic gate electrode is important for mass enhancement. We also studied the magnetic-field orientation dependence of the SdH effect and deduced a value of 3.0 ± 0.5 for the effective g factor in our thin oxide samples.