Si/Ge optical phonons and Strain-induced effect on MOS capacitor
Date Issued
2008
Date
2008
Author(s)
Fu, Yen-Chun
Abstract
In the thesis, we investigate the change of the physical and electrical properties based on Stained-Si. The thesis classifies two major sections：The first section is that we consider the variation of vibration phonon frequency between atoms in Strained-Si observed from micro-Raman spectroscopy. The other is that the flat-band voltage variation of MOS capacitors in Strained-Si. We consider the research purpose that the current property changed obviously with the stress directions on different channel under the strain technology. Because it is not effective and rapid to measure the stress degree of the Strained-Si under slight scale, we observe the change of vibration phonon frequency to predict the stress degree and then we also apply uniaxial and biaxial strain to MOS capacitors in different orientation Strained-Si to observe the shrinking of Silicon conduction band and valence band. The methods are potential to inspect stress degree quickly.he first, we focus on the change of vibration phonon frequency in Silicon observed from micro-Raman spectroscopy and employ the current model, Keating model, to explain the phonon vibration frequency peak at different Brillouin zone(Γ、X、L points).We also rely on the model to obtain the related parameters (Grunesien parameters) of the observed peak and infer the vibration constant from the parameters for Strained-Si. In order to calculate the effect of the vibration phonon frequency of the strained-Si, we start to observe the Raman shift in the experiment and we solve the ignvalue of the vibration equation to verify the biaxial and uniaxial strain. There are different constant ratio coefficient b between Raman-Shift and strain. We can received the stress degree from the constant ratio for different orientation substrate. The stress-strain transforms and the vibration constant is calculated by general tensor analysis and coordinate transform for different orientation substrate. At the same time, we assume the stress-free boundary condition for uniaxial strain. At last, we use ANSYS to simulate the stress degree and compare the error with the coefficient b. The second, we focus on the flat-band voltage variation of MOS capacitors in Strained-Si. We observe the change of the flat-band voltage to infer the different shrinking of the conduction band and valence band under strain. In the experiments, we exploit the strain mechanism to exert uniaxial or biaxial tensile strain. Under the deformation, we measure MOS capacitors in Strained-Si fabricated on the three directions (Silicon (110)). We also observe the the shrinking of the conduction band and valence band with different strain on different substrate. For the change of the flat-band voltage, we adjust the uniaxial and biaxial strain and focus on the shrinking to discuss with the physical phenomenon and confirm the deformation potential theory.
Subjects
Strained-Si、micro-Raman spectroscopy、phonon frequency、MOS capacitors、deformation potential theory
Type
thesis
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