C-Axis Perpendicularly Oriented Barium Ferrite Thin Film Media On Silicon Substrate

ABSTRACTBarium ferrite thin films with excellent perpendicular c-axis orientation were successfully fabricated on Si substrate without any buffer layer. To compensate for possible barium deficiency due to the inter-diffusion between films and substrate, a barium-rich target was used. For a 900 Å-thick film, the perpendicular remanent squareness is about 0.9, while the in-plane remanent squareness is about 0.3. The saturation magnetization (Ms) is about 220 emu/cc, while the coercivity is around 3500 Oe. X-ray diffraction (XRD) results show the (001) perpendicular c-axis texture in the films. It was also found that the rapid thermal annealing conditions greatly affect the magnetic properties of barium ferrite films. With a certain flow rate of oxygen gas in the rapid thermal annealer (RTA), barium ferrite films generally crystallize with good perpendicular c-axis texture. Without oxygen gas, the hexagonal barium ferrite phase fails to develop; instead spinel Fe 30 4 phase forms. The reason for the collapsing of hexagonal barium ferrite texture is thought to be an oxygen deficiency in the barium ferrite films due to the reduction of oxygen in the films during the high temperature annealing.

C-Axis Perpendicularly Oriented Barium Ferrite Thin Film Media on Silicon Substrate

ABSTRACTBarium ferrite thin films with excellent perpendicular c-axis orientation were successfully fabricated on Si substrate without any buffer layer. To compensate for possible barium deficiency due to the inter-diffusion between films and substrate, a barium-rich target was used. For a 900 Å-thick film, the perpendicular remanent squareness is about 0.9, while the in-plane remanent squareness is about 0.3. The saturation magnetization (Ms) is about 220 emu/cc, while the coercivity is around 3500 Oe. X-ray diffraction (XRD) results show the (001) perpendicular c-axis texture in the films. It was also found that the rapid thermal annealing conditions greatly affect the magnetic properties of barium ferrite films. With a certain flow rate of oxygen gas in the rapid thermal annealer (RTA), barium ferrite films generally crystallize with good perpendicular c-axis texture. Without oxygen gas, the hexagonal barium ferrite phase fails to develop; instead spinel Fe3O4 phase forms. The reason for the collapsing of hexagonal barium ferrite texture is thought to be an oxygen deficiency in the barium ferrite films due to the reduction of oxygen in the films during the high temperature annealing.

Dry Etching Damage Effect on Ohmic Characteristics of GaN

ABSTRACTWe report on the dry etching damage effects on the Ohmic contact characteristics of Sidoped n-type GaN. The 2-µm thick n-type GaN samples whose carrier concentrations are ∼7 × 1017/cm3 are grown on c-plane sapphire substrates by metalorganic chemical vapor deposition(MOCVD). The samples are processed to measure the transmission line method(TLM). We evaporated Ti/Al/Ni/Au=150/2700/400/4000 Å on the samples using an ebeam evaporator under 5 × 10−7 torr and annealed at 700 °C for lminute using a rapid thermal annealer(RTA). AES and XPS data show that the surface stoichiometry of the sample etched with H2 gas is gallium- richer than that of the one etched with Cl2 gas. According to the previous report[l], N-vacancy acts as shallow donor in GaN. However, specific contact resistivity of the sample etched with H2 gas is 3.03 × 10−6 Ω cm 2, which is much higher than that of the sample etched with C12 gas, 7.9 × 10 −7 Ω cm2. The difference of the N- vacancy formed during the etching process cannot completely explain the result. We suggest that formation of GaxOy during etching process, and the weakening of the bonding by ion bombardments might be responsible for the difference in the ohmic characteristics.

Rapid Thermal Annealing of Titanium in an Ammonia Ambient: Kinetics and Film Properties

The reaction between titanium and ammonia to form titanium nitride in a rapid thermal annealer has been studied as a function of process temperature and substrate conditions. The films produced have been characterized by Rutherford Backscattering, Sputtered Neutral Mass Spectroscopy and four point probe electrical resistivity measurements. On oxide substrates, below 720°C only dissolution of nitrogen within the titanium is observed leading to an increase in the specific resistance of the film. Above 720°C, stoichiometric titanium nitride begins forming leading to a drop in the specific resistance of the film. Only in the vicinity of 800°C is all the titanium consumed to form TiN. However, temperatures beyond 700°C cause dissolution of oxygen within the titanium. On silicon substrates, the competing reactions of nitridation and silicidation at the two interfaces govern the extent of nitridation.

Characteristics of Metal/PZT/p—Si MIS Capacitors

ABSTRACTLead Zirconate Titanate (PZT) thin films have been sputter deposited on p–Si. The patterned PZT films were annealed in a furnace as well as in a rapid thermal annealer. The high frequency characterization of metal–PZT– p– Si capacitors show good Capacitance–Voltage characteristics. The effective dielectric constant of PZT on Si was found to be very low and depends on the thickness of the PZT film and the annealing conditions. The high frequency C–V shows hysteresis which is due to the injection of charges across the interface.

Rapid densification of borophosphosilicate glass

The effect of densification, using a rapid thermal annealer, on properties of low pressure chemical vapor deposited borophosphosilicate glass films (4 wt.% B, 4 wt.% P) has been investigated. After densification, the wet etch rate of the films decreased by a factor of 12, while the infrared Si–O band peak height increased by 10%. Application of these findings to process monitoring and the impact of densification on subsequent processing have been examined. Results show that a single densification cycle at 950 °C/20 s induces glass flow behavior. Furthermore, for densification cycles from 500 to 1000 °C for 20 s followed by a fusion cycle of 1100 °C/20 s, densification temperature has no effect on the smoothing of glass over step structures. However, for contact sidewalls a densification cycle of at least 700 °C/20 s is required for sufficient tapering of the sharp corner. An optimal densification cycle for device processing was determined to be 800 °C/20 s.

Effect of Ambient Atmosphere on Thin Film Reaction of Si3N4 with Ti

The reaction of sputtered deposited Ti films of 100 nm thick with low pressure chemical vapor deposited Si3N4 films (300 nm thick) was studied in N2 or Ar, in a rapid thermal annealer. Reactions are followed using x-ray diffraction, Auger electron spectroscopy, and transmission electron microscopy. In argon, the Si3N4 and Ti reaction at low temperatures led to the product formation of two layer structure (TiN/Ti5Si3), with some contaminant oxygen and nitrogen released from the reaction uniformly dissolved throughout the remaining unreacted Ti. At higher temperatures, a three layer structure, TiN/TixSiy/TiN, on unreacted Si3N4 was developed. With increasing temperature the value of x and y decreased from 5 to 0 and 3 to 1, respectively. Reactions in N2 ambient, irrespective of temperature, always produced the three layer structure, but the thickness of TixSiy layer was much smaller than that produced in argon ambient for the corresponding temperatures. The reaction mechanism can be explained in terms of relative diffusion coefficients and the stability of the interfaces.

Study of Contact Angles of Metals and Alloys on the Superconducting YBa2Cu3O7-x

Wettability and contactibility of selected metals and alloys on superconducting YBa2Cu3O7-x were studied. Droplets of metals and alloys were formed by melting short segments of wires on pellets of YBa2Cu3O7-x The wires were melted in a rapid thermal annealer with an oxygen atmosphere to lessen the oxygen loss from the YBa2Cu3O7-x surface. The contact angles of the solidified droplets on the pellets were measured from the micrographs taken with a scanning electron microscope. Contact angles less than 90° were obtained with Pb and Ag, while angles greater than 90° were obtained with Bi metal, 40Pb/60Sn, and 99Pb/lSb alloys. Pb alloyed with either Sn or Sb increased the wetting angles. The contact angles provided a direct measurement of wetting characteristics and were used to relate various surface energies and the work of adhesion between tested metallic systems and YBa2Cu3O7-x.

Characterization of PSG Films Reflowed in Steam Using Rapid Thermal Processing

ABSTRACTThis study describes the use of a steam environment to reflow phosphosilicate glass (PSG) samples using a HEATPULSE® rapid thermal annealer. The samples comprised PSG over poly steps and of open contacts in PSG. It was observed that reflow occurs 50°C lower in steam than in dry O2. An acceptable flow cycle for 8 w/o P in PSG glass is 1050°C for 10 seconds in steam, while for 6 w/o P PSG it is 1100°C for 10 seconds. Steam is found to be an effective amibient for densification of the PSG film. The thermal oxide grown in the contact during opening reflow was determined to be near 140 A. The operating regime for a junction depth <0.4 um and a reflow angle < 75° is presented for 8 w/o P.