Optical and Electrical Propterties of High-k Dielectric Materials
Date Issued
2006
Date
2006
Author(s)
Chen, Tze-Chiang
DOI
en-US
Abstract
In this thesis, the metal-insulator-silicon diode using a high dielectric constant material (HfO2 or Hf-silicate) is studied for optical and electrical properties. First, the external quantum efficiency for light emission at room temperature from the MIS LED was observed to be 2.0×10-6, as compared to 0.5×10-6 for the metal-oxide-silicon (MOS) LED. The large hole concentration at the Si/HfO2 interface created by the high dielectric constant of HfO2 may be responsible for the enhancement. Moreover, the Al/HfO2/Silicon LED with a high interface trap density has a continuous spectrum below the Si gap beside the electron-hole plasma emission, probably due to the radiative recombination between the electrons and holes via the interface states.
It is very important to realize the thermal stability of high-k material. The thermal stability of strained Si0.8Ge0.2 and Si devices with HfO2 gate dielectrics is also studied. The thickness of the interfacial layer increases with increasing annealing temperature due to trace oxygen in the chamber or oxygen in HfO2 dielectric. The capacitance equivalent thickness increases with increasing post-deposition annealing temperature because of the increase of the interfacial layer. The interfacial trap density for the SiGe and Si devices with the PDA temperature of 600℃ are estimated to be 7.5 × 1012 cm-2eV-1 and 1.8 × 1011 cm-2eV-1, respectively.
In order to obtain appropriate interface properties, incorporation deuterium and hydrogen treatment during post-metallization annealing is employed to improve both the electrical and optical reliability of Pt/HfO2 gate stack. For comparison, deuterium-treated technology provides slightly better reliability improvement on both the electrical and optical reliability of Pt/HfO2 gate stack devices.
A novel method of FTIR measurement is created for high–k thin film. The peaks of Fourier transform infrared spectra at 960, 900 and 820 cm-1 originate from Hf-O-Si chemical bonds revealing that an Hf-silicate interfacial layer began to form at the HfO2/SiO2 interface after post-deposition-annealing process at 600 oC for 1 min. Moreover, the intensity of the peak at 750 cm-1 can indicate the degree of crystallization of HfO2. The formed Hf-silicate layer between HfO2 and SiO2 is also confirmed by X-ray photoelectron spectroscopy.
Finally, a metal/HfAlO/Si light emitting diode with Ge nanocrystals embedded in HfAlO has the visible light emission (610 nm) and the infrared emission (760 nm). The lattice structure and Ge content are measured by the transmission electron microscopy and Raman spectroscopy. The photoluminescence of Ge nanocrystals embedded in HfAlO has a peak at 700 nm, while the peak at 725 nm is observed for Ge nanocrystals embedded in HfO2. The difference may be due to the larger band gap of HfAlO as compared to HfO2.
Subjects
矽發光
可見光
傅立葉轉換器
high-k dieletric material
Si LED
visible light
FTIR
Type
thesis
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