Browsing by Author "Hsieh, Shang-Hsun"

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A Model for Neutral Defect Limited Electron Mobility in Strained-Silicon Inversion Layers
(2017-03-01)
Hsieh, Shang-Hsun
;
Chen, Ming-Jer
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
On the strained silicon metal-oxide-semiconductor field-effect transistors (MOSFETs), we show how to derive a formalism dealing with the scattering of a 2-D electron by a neutral defect. The corresponding neutral defect limited inversion-layer electron mobility, mu(n), is calculated in the momentum relaxation time approximation. The calculated results lead to a new analytical model: mu(n) = cN(n)(-1) where N-n is the neutral defect density per unit area and c is the coefficient independent of the inversion-layer density, the strain, and the temperature. The validity and applicability of the model are confirmed by citing three independent experiments on strained silicon MOSFETs undergoing different implantation sources and different annealing budgets. Importantly, this paper clarifies for the first time that strain will not change neutral defect limited mobility unless changing the neutral defect density. This reasonably explains the two experimental observations during implantation and annealing: 1) the implantation-induced strain relaxation in strained sample does not occur and 2) the neutral defect density is much higher in strained sample than in unstrained sample.
A New Microscopic Formalism for the Electron Scattering by Remote "Paired" Dipoles in HKMG MOSFETs
(2016)
Hsieh, Shang-Hsun
;
Hung, Jo-Chun
;
Chen, Ming-Jer
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We devise a new microscopic formalism for the remote dipole scattering (RDS) limited relaxation time in the inversion layers of HKMG MOSFETs. This formalism can apply to two different dipole configurations: (i) a "one dipole" configuration and (ii) a "paired dipoles" configuration. We find that when fitting the inversion-layer effective electron mobility measured from the industry-level hafnium-based metal gate MOSFETs, the former configuration yields a large value of the HK/IL interface dipole density of around 1015 cm(-2), accompanied by a large threshold voltage shift Delta V-th_dipole of 12 V. These values are comparable with those of the existing Monte Carlo simulation. More importantly, in case of the latter configuration (paired dipoles) plus the experimentally determined fixed charges, the corresponding values can be significantly reduced to 10(14) cm(-2) and 2 V, which are quite close to the experimental estimations in the literature.
Criteria for Plasmon-Enhanced Electron Drag in Si Metal-Oxide-Semiconductor Devices
(2015-03-01)
Chen, Ming-Jer
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Hsieh, Shang-Hsun
;
Liao, Yu-Chiao
;
Chen, Chuan-Li
;
Tsai, Ming-Fu
Plasmons in the highly doped source and drain regions of silicon field-effect transistors can strongly drag channel electrons via long-range collective Coulomb interactions and cause deteriorations in overall device performances. To examine such interactions, two different methods have been published: 1) sophisticated device simulations and 2) carefully calibrated experiments. To provide a more transparent understanding, we propose a third method in terms of two criteria: 1) one for the occurrence of the plasmon resonance and 2) the other for the strength of the plasmons. The former is determined based on our published dragged mobility data due to the interface plasmons and the bulk plasmons in gate. The latter makes use of our more recently experimentally extracted potential fluctuations due to plasmons in crystalline silicon. The effects of the temperature on the criteria are considered. It is a straightforward task to confirm that for a channel density larger than approximately 5 x 10(12) cm(-2), the source and drain plasmons act as key limiters in silicon device scaling. Therefore, the underlying device physics, modeling, simulations, experimental analyses, and data interpretation may be inaccurate if the limiting factors are not incorporated.
Plasmon-enhanced phonon and ionized impurity scattering in doped silicon
(2015-07-28)
Chen, Ming-Jer
;
Hsieh, Shang-Hsun
;
Chen, Chuan-Li
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Historically, two microscopic electron scattering calculation methods have been used to fit macroscopic electron mobility data in n-type silicon. The first method was performed using a static system that included long-range electron-plasmon scattering; however, the well-known Born approximation fails in this case when dealing with electron-impurity scattering. In the second method, sophisticated numerical simulations were developed around plasmon-excited potential fluctuations and successfully reproduced the mobility data at room temperature. In this paper, we propose a third method as an alternative to the first method. First, using a fluctuating system, which was characterized on the basis of our recently experimentally extracted plasmon-excited potential fluctuations, the microscopic calculations reveal enhanced short-range scattering of electrons by phonons and ionized impurities due to increased electron temperature and increased screening length, respectively. The increased hot electron population makes the Born approximation hold, which eases the overall calculation task substantially. Then, we return to the static system while incorporating plasmon-enhanced impurity scattering. The resulting macroscopic electron mobility shows fairly good agreement with data over wide ranges of temperatures (200-400 K) and doping concentrations (10(15) -10(20) cm(-3)). Application of the proposed method to strained silicon is also demonstrated. (C) 2015 AIP Publishing LLC.
Plasmons-Enhanced Minority-Carrier Injection as a Measure of Potential Fluctuations in Heavily Doped Silicon
(2014-07-01)
Chen, Ming-Jer
;
Chen, Chuan-Li
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Hsieh, Shang-Hsun
;
Chang, Li-Ming
;
電子工程學系及電子研究所
Well-known apparent electrical silicon bandgap narrowing in a heavily doped region of a bipolar transistor is observed by means of an enhanced minority-carrier injection experiment. In the region of interest, plasmons-induced potential fluctuations are existent in nature and hence constitute the origin of apparent bandgap narrowing. In this letter, we extract the underlying potential fluctuations directly from the enhanced minority-carrier injection experiment published in the literature. The core of the extraction lies in a combination of the two existing theoretical frameworks. First, the Gaussian distribution can serve as a good approximation of potential fluctuations. Second, no change can be made in the real bandgap between fluctuating conduction-and valence-band edges. Extracted potential fluctuations come from plasmons, as verified by our published temperature dependences of plasmons limited mobility in the inversion layer of MOSFETs as well as theoretical calculation results on bulk silicon. More importantly, this letter can deliver potential applications in the modeling and simulation area of nanoscale FETs (MOSFETs, FinFETs, and so forth) and bulk semiconductors.
Temperature-Oriented Mobility Measurement and Simulation to Assess Surface Roughness in Ultrathin-Gate-Oxide (similar to 1 nm) nMOSFETs and Its TEM Evidence
(2012-04-01)
Chen, Ming-Jer
;
Chang, Li-Ming
;
Kuang, Shin-Jiun
;
Lee, Chih-Wei
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Hsieh, Shang-Hsun
On a 1.27-nm gate-oxide nMOSFET, we make a comprehensive study of SiO2/Si interface roughness by combining temperature-dependent electron mobility measurement, sophisticated mobility simulation, and high-resolution transmission electron microscopy (TEM) measurement. Mobility measurement and simulation adequately extract the correlation length lambda and roughness rms height Delta of the sample, taking into account the Coulomb-drag-limited mobilities in the literature. The TEM measurement yields the apparent correlation length lambda(m) and roughness rms height Delta(m). It is found that the following hold: 1) lambda approximate to lambda(m) for both the Gaussian and exponential models, validating the temperature-oriented extraction process; 2) the extracted Delta (similar to 1.3 angstrom for the Gaussian model and 1.0 angstrom for the exponential one) is close to that (similar to 1.2 angstrom) of Delta(m), all far less than the conventional values (similar to 3 angstrom) in thick-gate-oxide case; and 3) the TEM 2-D projection correction coefficient Delta(m)/Delta is approximately 1.0, which cannot be elucidated with the current thick-gate-oxide-based knowledge.
Two Competing Limiters in MOSFETs Scaling: Neutral Defects and S/D Plasmons
(2016)
Hsieh, Shang-Hsun
;
Hung, Jo-Chun
;
Weng, Heng-Jui
;
Tsai, Ming-Fu
;
Chiang, Chih-Chi
On the industrial HKMG silicon MOSFETs with different channel lengths L down to 14 nm, we present high-resolution TEM cross-section images to highlight interstitial defects in the channel near the source and drain. To examine such neutral defects, we devise a new 2D microscopic scattering model and use it to extract the apparent neutral defects density from the measured inversion-layer effective mobility. We find that for L > 25 nm, the extracted defect densities are independent of temperature, as expected. However, for L < 25 nm, the plasmons in the highly doped source and drain regions prevail over neutral defects. Further measured degradation in the virtual source velocity at saturation matches that of full Coulomb Monte Carlo simulation, for the first time experimentally confirming S/D plasmons as the dominant mechanism for L < 25 nm.