Thickness Of ZrO Research Articles

Characterization of high-K dielectric ZrO2 films annealed by rapid thermal processing

In this investigation, two kinds of ZrO2 samples were prepared. The ZrO2 films of about 150 Å by PVD were used for physical characterization and the ultrathin ZrO2 films of about 40 Å by RTCVD were used for electrical characterization of MOS capacitors. The samples were annealed in a rapid thermal processing (RTP) system at temperatures of 400–1050 °C in various gas ambients, including O2, N2, forming gas (H2/Ar), wet H2 (15% H2O in H2), and wet O2 (15% H2O in O2). Spectroscopic ellipsometry (SE) with a two layer BEMA optical model was used to characterize the ZrO2 thickness and evaluate the microstructure. A wet etch rate test of ZrO2 films in 1:100 HF solution using SE indicated two distinct etch rates, with a slower initial rate followed by a faster rate. The measured etch rates are dependent of temperature, indicating 4.85 and 38.9 Å/min at 25 and 45 °C, respectively. The RTP annealing temperature and gas ambients have a significant effect on the ZrO2 film etch rate. Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy depth profile were used to characterize the films. Three ZrO2 samples were measured by both cross section transmission electron microscopy and SE, indicating that the thickness difference between two techniques is only 1 Å. A mercury probe was used to characterize the electrical properties of the physical vapor deposition dielectric films. The electrical characterization of ultrathin ZrO2 films show that the gas ambients in postdeposition anneal affect the equivalent oxide thickness (EOT) and leakage current significantly. The lowest EOT achieved in this study is 10.9 Å for the sample spike annealed in N2. The RTP effect on electrical properties of ultrathin ZrO2 was also discussed.

C-V characteristics of metal ferroelectrics insulator semiconductor (MFIS) using a Au/Cr/PZT/ZrO2/Si structure

MFIS structure using Au/Cr/ZrO2/PZT/Si was fabricated and the C-V characteristics of it were investigated. It was found that the memory window has a maximum when the thickness of the ZrO2 thin film increased. The memory window reached 2.5V for the sweep voltage from -5V to +5V while the thickness of ZrO2 and PZT thin film were 30nm and 250nm respectively. When the thickness of PZT thin film increased, the memory window increased. The reasons of above phenomena were discussed.

Surface oxidation of zirconium above room temperature

Abstract In order to investigate the initial oxidation mechanism of Zr, the temperature dependence of surface oxidation of Zr has been examined by in situ AES surface analysis and subsequent depth profiling with Ar ion sputtering for the first time. Below 600 K surface oxidation proceeds through three stages, that is, oxygen solution in α-Zr(O) up to around 30 at%, precipitation and development of ZrO2 on the surface, and growth of the ZrO2 thickness. Depth profiling of the oxidized specimen shows that the oxidized surface is completely covered by a ZrO2 layer followed by a mixed layer of ZrO2 and α-Zr(O) and a single phase of α-Zr(O) beneath the mixed layer. Above 700 K no precipitation or layer formation of the oxide is observed, and the oxygen concentration, which is determined by the balance between the oxygen uptake rate on the top surface from the gas phase and the diffusion flux into the bulk, is changed depending on the pressure of exposed oxygen. Supposing that growth of the oxide layer obeys the parabolic rate law, oxygen diffusion coefficients in the ZrO2 and the α-Zr(O) are estimated. The determined values are consistent with the extrapolated values from high temperature literature data, which confirms the oxidation kinetics described here.