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.

Low pressure chemical vapor deposition ͑LPCVD͒ of silicon nitride from bis͑tertiary-butylamino͒silane ͑BTBAS͒ and ammonia precursors has been demonstrated at 550-600°C in a 200 mm vertical batch furnace system. Deposition rates of 4-30 Å/min are achieved with a film thickness variation below 2% 1-sigma. Silicon nitride depositions using BTBAS and NH 3 were found to retain a significant mass-transfer limiting component at temperatures Ͻ600°C. Substantial carbon and hydrogen incorporation are detected in low-temperature BTBAS silicon nitride, relative to dichlorosilane based silicon nitride deposited at higher temperature. These impurities result in the formation of a SiNCH solid solution with carbon substitution of nitrogen and disproportionate occupation of silicon and nitrogen sites by interstitial hydrogen. Optical and physical properties of silicon nitride are significantly altered by the addition of carbon and hydrogen impurities. Etch resistance of BTBAS-derived silicon nitride was found to diminish at elevated hydrogen levels. However, increasing etch resistance is observed in silicon nitride films with higher carbon levels. The data from this study indicate that carbon and hydrogen impurity concentrations may be tuned to produce silicon nitride with specific material properties.

Through an electron beam evaporation process, silver nanoparticles (Ag-nps) were introduced into dielectric thin-films. Silver incorporation into the oxide films resulted in a distribution of insulating Ag-nps at a density of ~10^12 particles/cm^2. For these samples, an enhancement of about two fold in dielectric constant was observed in both Al2O3 and HfO2. We attribute the dielectric constant enhancement to the polarizability of metallic nanoparticles. The dipole moment of the Ag-nps increased the stack dielectric constant in a frequency dependent manner. Because of the inherent relaxation frequency of the Ag-np dipoles and space-charge polarization, the dielectric constant was more strongly enhanced at lower frequencies (down to 100 Hz) relative to higher frequencies (up to 1 MHz). Gate leakage currents remained comparable between the control and nanocomposite samples. The Ag-nps also produced a memory effect. Potential applications of these Ag-np based films in CMOS devices are discussed.

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