Abstract-A systematic design of practicable media suitable for re-writeable, ultra-high density (> 1Tbit/sq.in.), high data rate (> 1Mbit/s/tip) scanning probe phase-change memories is presented. The basic design requirements were met by a Si/TiN/GST/DLC structure, with properly tailored electrical and thermal conductivities. Various alternatives for providing re-writeability were investigated. In the first case amorphous marks were written into a crystalline starting phase and subsequently erased by re-crystallization, as in other already-established phasechange memory technologies. Results imply that this approach is also appropriate for probe-based memories. However, experimentally the successful writing of amorphous bits using scanning electrical probes has not been widely reported. In light of this a second approach has been studied, that of writing crystalline bits in an amorphous starting matrix, with subsequent erasure by re-amorphization. With conventional phase-change materials, such as continuous films of Ge 2 Sb 2 Te 5 , this approach invariably leads to the formation of a crystalline 'halo' surrounding the erased (re-amorphized) region, with severe adverse consequences on the achievable density. Suppression of the 'halo' was achieved using patterned media or slow-growth phase-change media, with the latter seemingly more viable.
In this paper, the correlation between dislocation density and transistor leakage current is demonstrated. The stress evolution and the generation of defects are studied as a function of the process step, and experimental evidence is given of the role of structure geometry in determining the stress level and hence defect formation. Finally, the role of high-dose implantations and the related silicon amorphization and recrystallization is investigated.
Secondary ion mass spectrometry characterization of source/drain junctions for strained silicon channel metal-oxide-semiconductor field-effect transistors
This paper presents a systematic investigation of thermal stability of high-k materials deposited on RCA cleaned wafers by ALCVD™ in an ASM Pulsar™ 2000 reactor. Physical-chemical evolution of Al2O3, HfO2 and Al/Hf composite materials (nanolaminate and aluminates) was studied considering two types of thermal treatments: quenched vacuum anneals from 300°C to 900°C and furnace atmospheric processes in N2 or O2 at 850°C and 900°C. Material crystallization and changes in film structure were studied by means of TEM, XRD, XRR, XRF, RBS and TOF-SIMS. Non-contact electrical measurements were used to detect modification in EOT and fixed charge. Al2O3 was found still amorphous at 900°C. Not so for HfO2 that crystallized in monoclinic phase at a temperature between 300–400°C. Crystallization temperature and possible phase separation of Al/Hf composite materials were found to be a function of Al2O3 content and film type. In most of these samples, however, a chemical evolution was detected in addition to the above reported crystallization phenomena. All the achieved results demonstrate that depending on thermal treatment conditions, ALCVD™ high-k stability does not only concern phase transition effects but also a transformation of the “SiO2/high-k” system into “doped-SiO2/silicate” stack.
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