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.

Silicon nitride films have been deposited using inductively-coupled plasma high-density plasma chemical vapor deposition (HDP CVD), plasma-enhanced chemical vapor deposition (PECVD), and low pressure chemical vapor deposition (LPCVD) methods. Characterization and comparison of the three films were performed using Fourier-transform infrared spectroscopy, secondary-ion mass spectroscopy, Rutherford backscattering spectrometry, and hydrogen forward-scattering spectrometry, in addition to wet-etch rate and stress measurement studies. It was found that silicon nitride films deposited using HDP CVD method have several advantages over the silicon nitride films that were deposited using the LPCVD and PECVD methods. The HDP CVD silicon nitride film can be deposited at much lower temperatures (⩽400 °C) than LPCVD silicon nitride, and has substantially less hydrogen (5.5 at. %) than the PECVD film. In addition, the PECVD film contains some oxygen in the film. The wet-etch rate of HDP CVD silicon nitride film is comparable to that of LPCVD film and is significantly less than that of PECVD film in both hot phosphoric acid and buffered HF solutions. The stress of the HDP CVD film is similarly compressive to the PECVD silicon nitride, and not as highly tensile as that of LPCVD silicon nitride.

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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Multiple factors need to be considered when selecting an interlevel dielectric material for GaAs semiconductor device fabrication including what the electrical, mechanical, chemical, thermal, and cost requirements are and whether the material and the process are compatible with GaAs processing. In this study, we evaluated several interlevel dielectric materials for GaAs heterojunction bipolar transistor ͑HBT͒ technology. This technology requires the material to have good gapfill and planarizing characteristics, as the various device and interconnect structures can have significant topography. Additionally, the process typically can only have a maximum temperature of Ͻ300°C, as device degradation can occur at higher temperatures. The dielectric materials evaluated are plasma-enhanced chemical vapor deposition ͑PECVD͒, silicon nitride ͑Si 3 N 4 ͒, polyimide, and photodefinable polybenzoxazole ͑PBO͒. The PECVD Si 3 N 4 is mostly conformal when deposited. However, it has a high dielectric constant, cannot be used as gapfill material, and does not planarize the underlying topography, which makes multilevel metallization challenging. Polyimide and PBO, both of which need to be thermally cured, have a lower dielectric constant than PECVD Si 3 N 4 . However, the polyimide in this study has to be dry-etched, unlike the photosensitive PBO. Furthermore, the PBO has better gapfill and planarization capabilities than polyimide.Dielectrics are widely used for various applications in semiconductor device fabrication in the processing of both silicon and compound semiconductors, such as GaAs. They include applications, such as surface passivation, premetal dielectric, capacitor dielectric, interlevel dielectric, antireflective coating, final passivation, redistribution layer, and as a stress buffer layer and an encapsulant in packaging. [1][2][3][4][5][6][7][8][9][10][11][12] There are several types of dielectrics that are typically used for interlevel dielectrics. The most widely used are spin-on and plasma-enhanced chemical vapor deposition ͑PECVD͒ dielectrics. The spin-on dielectrics include both organic and inorganic films, such as benzocyclobutene ͑BCB͒, spin-on glass, polyimide, polybenzoxazole ͑PBO͒, and many others. 1,6,7,13-15 The most commonly used PECVD films include undoped and doped silicon dioxide ͑SiO 2 ͒, silicon oxynitride ͑SiON͒, and silicon nitride ͑Si 3 N 4 ͒. 11,12,[16][17][18][19][20][21][22][23] In GaAs technology, there are many factors that need to be taken into consideration when selecting an interlevel dielectric material, and depending on the material selected, the process flow is different. One of the most important considerations is the temperature and thermal budget constraint of the technology for which the interlevel material is to be used. For instance, while the maximum processing temperature for the backend-of-line for Si technology typically is 400°C, the maximum temperature for most GaAs technologies is 300°C or less. At temperatures higher than 300°C, significant GaAs device degradation occ...