Improved effective mobility extraction in MOSFETs (original) (raw)
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Solid-State Electronics, 1996
We present a method for the determination of the electron mobility in the channel of a MOSFET in the moderate-and strong-inversion regions. The procedure is based on combining measured and computed current-voltage curves. Computed curves have been generated using a quantum-mechanical and a modified classical model. Results are shown to be in good agreement when the classical charge-sheet model was modified by including an inversion-layer depth, defined as the mean transverse position for the electrons in the channel. This method also allows for small geometry and series-resistance effects to be incorporated in a relatively simple way. Experimental mobility data were obtained in the 13-300 K temperature range for a wide range of transverse electric fields. The contribution of Coulomb scattering to the mobility has also been analysed experimentally by comparing the results to theoretical mobility curves calculated for the case of zero-charge centres.
A reliable metric for mobility extraction of short-channel MOSFETs
When comparing the extracted carrier mobility of long-and short-channel transistors, special consideration must be given to the metallurgical gate length (L met ), neglecting the impact of source and drain junction profiles. L met can be identified with nanometer precision by using RF split-C-V measurements, and physical and electrical analysis can demonstrate the accuracy of the method. Another important parameter, the external transistor resistance (R sd ), can be identified with linear current measurements of short-channel devices. However, it is important to quantify the mobility dependence from the gate length in order to obtain an accurate result. A method to estimate the electrical field (E eff ) of short-channel devices is proposed. The extracted short-channel mobility shows a universal behavior identical to the classical long-channel one.
IEEE Transactions on Electron Devices, 1997
A new experimental method for determining the dependence of the electron mobility on the longitudinal-electric field has been developed. The development, validation, and explanation of this new method has been carefully carried out. We have applied this procedure to standard submicron MOSFET's and after having obtained the mobility dependence on both the transverse-and longitudinal-electric fields, we reproduced the experimental output curves. The saturation velocity has also been calculated using the mobility curves obtained by this new method. A saturation-velocity value higher than other previously reported experimental ones was observed. This saturation-velocity value is similar to those calculated with Monte Carlo MOSFET simulators.
A method to extract mobility degradation and total series resistance of fully-depleted SOI MOSFETs
IEEE Transactions on Electron Devices, 2002
Free-carrier mobility degradation in the channel and drain/source series resistance are two important parameters limiting the performance of MOS devices. In this paper, we present a method to extract these parameters from the drain current versus gate voltage characteristics of fully-depleted (FD) SOI MOSFETs operating in the saturation region. This method is developed based on an integration function which reduces errors associated with the extraction procedure and on the d.c. characteristics of MOS devices having several different channel lengths. Simulation results and measured data of FD SOI MOSFETs are used to test and verify the method developed.
Microelectronics Reliability, 2009
A new procedure is presented to separate the effects of source-and-drain series resistance and mobility degradation factor in the extraction of MOSFET model parameters. It requires only a single test device and it is based on fitting the I D (V GS , V DS ) equation to the measured characteristics. Two types of bidimensional fitting are explored: direct fitting to the drain current and indirect fitting to the measured source-to-drain resistance. The indirect fitting is shown to be advantageous in terms of fewer number of iterations needed and wider extent of initial guess values range.
MOSFET I–V characteristics at small and large drain biases in the linear region
Solid-State Electronics, 2007
A new conventional mobility formula is advised to overcome the enigmas of the known formula. It is made possible to extract all device parameters including the series resistance for each device, and the formula is helpful in deriving an I-V formula over the entire linear region of MOSFETs. The proposed mobility formula is akin to the known one and can overcome the two problems inherent to the traditional mobility model of: (1) inability of explicitly assessing the series resistance, and (2) difficulty with analytical integration over the surface potential along the channel. The series resistance is extracted independently for each device, and its channel length dependence can now be discussed. A new formula is derived for the linear region where the role of important parameters is easy to interpret. It is discussed that the parameter n may differ with devices. When optimized, an average fitting error as small as %0.4% is achieved over the entire linear region.
Subthreshold Mobility Extraction for SOI-MESFETs
Journal of Computational Electronics, 2004
Mobility calculation is a difficult task due to the stochastic nature of the particles in a device. This is especially true for a device operated in the sub-threshold region because the transport is a combination of diffusion and drift albeit diffusion dominated. As a result, one can calculate the mobility based on the drift and the diffusion techniques for a device operated in the subthreshold regime. We have developed a transport model, based on the solution of the Boltzmann Transport Equation, for modeling n-channel silicon-on-insulator (SOI) MOSFETs and MESFETs using the Ensemble Monte Carlo technique. All relevant scattering mechanisms for the silicon material system have been included in the model. The model is used to calculate both the diffusion coefficient and the drift based mobility and the results are compared with available experimental values. The mobility of the equivalent SOI MESFET device is a factor of 3-5 times higher than that of the MOSFET in the sub-threshold regime.
Improved method for determining inversion layer mobility of electrons in trench MOSFETs
IEE Proceedings - Circuits, Devices and Systems, 2004
Trench sidewall effective electron mobility (m eff ) values were determined by using the split capacitance-voltage (CV) method for a large range of the transversal effective field (E eff ) from 0.1 up to 1.4 MV/cm. The influences of crystal orientation, doping concentration and, for the first time, temperature were investigated. Results show that the split CV method is an accurate method for determining m eff (E eff ) data in trench MOSFETs; the {100} m eff data approaches published data on planar MOSFETs for high E eff ; and mobility behaviour can be explained with generally accepted scattering models for the entire range of E eff . The results are important for the optimisation of trench power devices.
Semiconductor Science and Technology, 2009
A new procedure is presented to separate and extract source-and-drain series resistance and mobility degradation factor parameters in MOSFET compact models. It also allows us to extract the device's channel conductance. The procedure is not based on fitting, but on directly calculating the three parameters by solving a system of three simultaneous equations. The equations represent the measured source-to-drain output resistance, obtained from the output characteristics, and its first and second integrals with respect to gate voltage. This method may be applied to a single device, measured in strong inversion as a function of gate voltage, at a small drain bias.