Articles you may be interested inPerimeter and area current components in HfO2 and HfO2−x metal-insulator-metal capacitors J. Vac. Sci. Technol. B 31, 01A117 (2013); 10.1116/1.4774104 Properties of stacked SrTiO3/Al2O3 metal-insulator-metal capacitors J. Vac. Sci. Technol. B 31, 01A102 (2013); 10.1116/1.4766183 Metal-insulator-metal capacitors using atomic-layer-deposited Al 2 O 3 ∕ Hf O 2 ∕ Al 2 O 3 sandwiched dielectrics for wireless communications Physical and electrical characterization of HfO 2 metal-insulator-metal capacitors for Si analog circuit applicationsCharacterization was performed on the application of atomic layer deposition (ALD) of hafnium dioxide (HfO 2 ) and aluminum oxide (Al 2 O 3 ), and plasma-enhanced chemical vapor deposition (PECVD) of silicon nitride (Si 3 N 4 ) as metal-insulator-metal (MIM) capacitor dielectric for GaAs heterojunction bipolar transistor (HBT) technology. The results show that the MIM capacitor with 62 nm of ALD HfO 2 resulted in the highest capacitance density (2.67 fF/lm 2 ), followed by capacitor with 59 nm of ALD Al 2 O 3 (1.55 fF/lm 2 ) and 63 nm of PECVD Si 3 N 4 (0.92 fF/lm 2 ). The breakdown voltage of the PECVD Si 3 N 4 was measured to be 73 V, as compared to 34 V for ALD HfO 2 and 41 V for Al 2 O 3 . The capacitor with Si 3 N 4 dielectric was observed to have lower leakage current than both with Al 2 O 3 and HfO 2 . As the temperature was increased from 25 to 150 C, the breakdown voltage decreased and the leakage current increased for all three films, while the capacitance increased for the Al 2 O 3 and HfO 2 . Additionally, the capacitance of the ALD Al 2 O 3 and HfO 2 films was observed to change, when the applied voltage was varied from À5 to þ5 V, while no significant change was observed on the capacitance of the PECVD Si 3 N 4 . Furhermore, no significant change in capacitance was seen for these silicon nitride, aluminum oxide, and hafnium dioxide films, as the frequency was increased from 1 kHz to 1 MHz. These results show that the ALD films of Al 2 O 3 and HfO 2 have good electrical characteristics and can be used to fabricate high density capacitor. As a result, these ALD Al 2 O 3 and HfO 2 films, in addition to PECVD Si 3 N 4 , are suitable as MIM capacitor dielectric for GaAs HBT technology, depending on the specific electrical characteristics requirements and application of the GaAs devices.

Photosensitive polybenzoxazole (PBO) film has been used in GaAs heterojunction bipolar transistor (HBT) technology for stress buffer and mechanical protection layer applications. However, this film needs to be cured at high temperatures for a long period of time in order to obtain its desired excellent material characteristics. High-temperature curing can result in degradation to the electrical characteristics and performance of the underlying GaAs devices due to limited thermal budget. In this paper, we have characterized the effects of curing the PBO film on GaAs HBT wafers using a conventional convection furnace and using a variable frequency microwave (VFM) furnace. The results show that a VFM cure can achieve similar excellent physical, mechanical, thermal, and chemical material characteristics at a lower curing temperature and in a much shorter time, as compared to convection furnace curing, therefore resulting in minimal GaAs device degradation. Based on these results, an optimum curing condition using the VFM method can be obtained that satisfies both stress buffer layer material and device requirements for GaAs HBT technology.

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The rheological behavior of multilayer polyjeric structures has been investigated Measurements of the bulk viscoelastic properties via small‐amplitude oscilatory rheometry indicated that the shear viscosity is independent of both the numbe of layers (83 vs. 165) and the composition (30/70, 50/50, and 70/30 PC/PMMA by weight) within the limits of the data obtained. It is also apparent tha tthe shear viscosity is influenced strongly by the skin layer material. In additon, a model has been developed tha tcan be used to proedict the shear viscosity and shear stress ofa multilayer structure experiencing shear flow. The model predicts tha thte shear viscosity of a multilayer structure should be independent of the number of layers and strongly dependent on the material in the skin layer. These predictions are in agreement with experimental data.

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