Characterizations of Metal-Oxide-Semiconductor Devices with High-k Gate Dielectrics Formed by Low Temperature Processes
Date Issued
2009
Date
2009
Author(s)
Chang, Chia-Hua
Abstract
The requirements of high-quality low temperature processing dielectrics have substantially increased due to the development of display and flexible electronics in these days. The process temperature is required to be low for the electronic devices with glass and flexible substrates. Besides, the next-generation devices technology leads to great reduction in gate dielectrics thickness to achieve high performance. However, the problem of gate leakage currents also accompanies. Alternative materials for gate dielectrics with high dielectric constant, such as HfO2 and Al2O3, have been widely studied to overcome the problem. In addition, alternative insulators for display devices are also required to be fabricated under low temperature. HfO2 and Al2O3 processed under proper processes could possess superior characteristics. Therefore, the methods for high-k dielectrics preparation are of interest. or the preparation of hafnium oxide stacks, SiO2 were first grown as the interfacial layer by room temperature anodization followed by sputtering of Hf metal on a tilt-substrate. The Hf metal with SiO2 interfacial layer was oxidized in nitric acid to form HfO2/SiO2 stacks. The as-prepared high-k dielectric was then passivated by the proposed post anodization compensation method. The compensation process is carried out by putting the prepared HfO2 or Al2O3 in deionized water, and then a DC superimposed with AC electric field is applied across the sample and a Pt cathode. After compensation, samples are annealed at a proper temperature. The high-k dielectrics after receiving post anodization compensation exhibited improved characteristics in dielectric constant, leakage currents, and stress reliability. We suggest that the post anodization compensation method is potentially useful for high-k dielectrics which are prepared by other processes. inally, a novel structure of Al2O3/HfO2/SiO2 dielectric stack prepared by in-situ oxidation in dc-sputtering technique is proposed for possible flash memory application. The devices exhibit the characteristics of low leakage current of 10-8 A/cm2 at Vg=−2V, high breakdown voltage of −5.4 V and well charge trapping/de-trapping operation. The physical mechanisms of charge trapping and de-trapping in the dielectric stack are also studied. It is proposed that the Al2O3/HfO2/SiO2 dielectric stack prepared by in-situ oxidation is merit for the next generation flash memory application.
Subjects
low temperature dielectrics
anodic oxidation
HfO2
Al2O3
SiO2
dielectric stacks
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-98-D94943022-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):512daec0027855429fe0b1338f089c7d