Multilayer reactive electron-beam evaporation of thin aluminum oxide layers with embedded silver nanoparticles ͑Ag-nps͒ has been used to create a dielectric thin film with an enhanced permittivity. The results show a frequency dependent increase of the dielectric constant . Overall stack of the control sample was found to be 7.7-7.4 in the 1 kHz-1 MHz range. This is in comparison with = 16.7-13.0 over the same frequency range in the sample with Ag-nps. ideally suited for use with n-and p-type Si over a range of doping levels. The drawback is that the intermediate dielectric constant of Al 2 O 3 limits the capacitance density compared with other high-dielectrics. It is worth noting at this point that the permittivity of metal nanoparticles has been theorized to be superior to that predicted by the classical electrostatic model. 4 This is explained considering the dipole behavior of nonspherical nanoparticles dispersed in a medium. Each nanoparticle dipole is recognized as behaving like a basic harmonic oscillator or dipole with a relaxation frequency. 5 The deposition of semiconductor device grade films of Al 2 O 3 and HfO 2 on Si is well established. 6,7 However, prior work on using noble metal nanoparticles to increase dielectric constants has focused primarily on polymer and glass dielectrics and processes that are not readily compatible with current integrated circuit fabrication. [8][9][10] Conversely, studies utilizing techniques similar to that used here have not focused explicitly on permittivity enhancement or dielectric properties. 11 The primary differences between the work presented here and earlier works on permittivity enhancement with nanoparticles are the manner in which the silver nanoparticles ͑Ag-nps͒ are deposited, the dielectric medium into which they dispersed, and the deposition and characterization of the film on Si substrates.A control set without Ag-nps and an experimental set with Ag-nps were fabricated. In each set, samples were prepared on both p-and p + -Si ͑100͒ with resistivities of 1-10 and 0.0030-0.00 70 ⍀ cm, respectively. The Si substrates were first cleaned with a modified Shiraki process to remove the native oxide and provide a clean, hydrogen passivated surface. 12,13 After drying under nitrogen, they were immediately transferred to a Kurt J. Lesker AXXIS e-beam evaporation system. From a base pressure of 5 ϫ 10 −7 torr, the substrates were heated to 50°C and oxygen was introduced at 5 SCCM ͑SCCM denotes cubic centimeter per minute at STP͒ and 5 ϫ 10 −5 torr. For control samples without silver, 8.73± 0.08 nm of Al 2 O 3 was then evaporated at 0.5 Å / s. For samples with incorporated Ag-nps, Al 2 O 3 , approximately 3 nm in thickness, was deposited and the chamber was again pumped down to 5 ϫ 10 −7 torr. An ultrathin layer of Ag-nps, about half a nanometer in nominal thickness, was deposited under high vacuum. Oxygen was reintroduced, and approximately 3 nm of Al 2 O 3 was again evaporated. This process was repeated until the film consisted of three layers of Al 2 O 3 with tw...
Hafnium dioxide films have been deposited using reactive electron beam evaporation in oxygen on hydrogenated Si(100) surfaces. The capacitance–voltage curves of as-deposited metal(Ti)–insulator–semiconductor structures exhibited large hysteresis and frequency dispersion. With post-deposition annealing in hydrogen at 300 °C, the frequency dispersion decreased to less than 1%/decade, while the hysteresis was reduced to 20 mV at flatband. An equivalent oxide thickness of 0.5 nm was achieved for HfO2 thickness of 3.0 nm. We attribute this result to a combination of pristine hydrogen saturated silicon surfaces, room temperature dielectric deposition, and low temperature hydrogen annealing.
Plasma enhanced deposition of amorphous aluminum nitride (AlN) using trimethylaluminum, hydrogen, and nitrogen was performed in a capacitively coupled plasma system. Temperature was varied from 350 to 550 °C, and pressure dependence of the film structure was investigated. Films were characterized by Fourier transform infrared, Rutherford backscattering (RBS), ellipsometry, and x-ray diffraction (XRD). The films are amorphous in nature, as indicated by XRD. Variations in the refractive index were observed in ellipsometric measurements, which is explained by the incorporation of carbon in the films, and confirmed by RBS. Capacitance–voltage, conductance–voltage (G–V), and current–voltage measurements were performed to reveal bulk and interface electrical properties. The electrical properties showed marked dependence on processing conditions of the AlN films. Clear peaks as observed in the G–V characteristics indicated that the losses are predominantly due to interface states. The interface state density ranged between 1010 and 1011 eV−1 cm−2. Annealing in hydrogen resulted in lowering of interface state density values.
Articles you may be interested inEffect of ion bombardment and annealing on the electrical properties of hydrogenated amorphous silicon metal-semiconductor-metal structures Structural and mechanical characterization of fluorinated amorphous-carbon films deposited by plasma decomposition of CF 4 -CH 4 gas mixtures Electrical and optical properties of amorphous fluorocarbon films prepared by plasma polymerization of perfluoro-1,3-dimethylcyclohexane J.We have studied the capacitance-voltage (C -V), conductance-voltage (G -V), and currentvoltage characteristics of fluorinated amorphous carbon (a-C:F x ) films using metal/a-C:F x /Si and metal/a-C:F x /metal structures, respectively. Samples annealed in a vacuum were also studied. The C -V curves of the as-deposited sample are stretched about the voltage axis. Interface state density of 4.1ϫ10 11 cm Ϫ2 eV Ϫ1 at the midgap was calculated. Annealing the sample deposited on Si in a vacuum caused more frequency dispersion in the C -V and G -V curves, probably due to the diffusion of carbon into silicon. The bulk density of states for samples deposited on metal, measured by space-charge-limited current technique, decreased from 4ϫ10 18 eV Ϫ1 cm Ϫ3 for the as-deposited sample, to 7ϫ10 17 eV Ϫ1 cm Ϫ3 for the annealed sample.
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