Thermal stability of stacked high-κ dielectrics, especially ZrO2, HfO2 and ZrSiO4 /SiO2 layered structures, on silicon has been investigated in terms of ultrahigh vacuum (UHV), 1 Torr N2 and helium (He) gas annealing with controlled oxygen partial pressure (PO2) at 920. Comparison of 2 nm and 20 nm ZrO2 films under UHV annealing revealed that the trigger of silicidation is the contact of ZrO2, SiO and Si accompanying disappearance of interfacial SiO2 layer due to SiO desorption. In the contact position, a small amount of SiO gas can easily change ZrO2 to ZrSi2. This reaction model is also applicable to the silicidation of HfO2 and ZrSiO4, at not only stacked high-κ film/Si substrate interface, but also at gate poly-Si/high-κ film interface. Moreover, comparison of UHV, N2 and He annealing with controlled PO2 revealed that the optimal PO2 ranges in He at which the thermal stability of layered structure can be achieved are wider than those in UHV and N2. This result suggests that He gas physically may obstruct SiO creation due to the quenching of atomic vibration at degradation-prone sites in the SiO2 /Si interface, thus reducing probability of bond breaking process, which is the first step of silicidation.

This paper describes the optical characteristics and static fatigue reliability of a zirconia alignment sleeve, which is a component part of an optical connector with zirconia ferrules. This combination of sleeve and ferrules hardly generates any wear debris during connector insertion and removal cycles. This has reduced the cleaning frequency of the ferrule endface during cycles and greatly improved the return loss stability of the optical connectors. The zirconia alignment sleeve enables stable return loss characteristics to be achieved over a wide temperature range as it has the same thermal expansion coefficient as the zirconia ferrule. Furthermore, the gauge retention force for the zirconia alignment sleeve is defined with a view to its practical use. This force must be between 2.0 and 3.9 N to allow stable optical connections to be made under various mechanical and environmental conditions. We also clarify the conditions for a proof test by which to prevent the occurrence of static fatigue fractures in the sleeve, and we confirm the validity of the test. The static fatigue parameters for zirconia ceramics and derived from the static fatigue theory for brittle materials and fracture testing. We use these static fatigue parameters to predict the lifetime of a zirconia sleeve under working stress. An appropriate stress level for the proof test which eliminates weak sleeves, is about 3 times greater than working stress. The strength of the sleeve as demonstrated in the proof test is confirmed by accelerative stress aging. The performance of this sleeve is superior to that of a conventional copper alloy sleeve and the proof test confirms its reliability; under 0.1 FIT for 20 years of use.