82 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 49, NO. 1, JANUARY 2002 A Method to Extract Mobility Degradation and Total Series Resistance of Fully-Depleted SOI MOSFETs Francisco J. García Sánchez, Senior Member, IEEE, Adelmo Ortiz-Conde, Senior Member, IEEE, Antonio Cerdeira, Senior Member, IEEE, Magali Estrada, Senior Member, IEEE, Denis Flandre, Member, IEEE, and Juin J. Liou, Senior Member, IEEE Abstract—Free-carrier mobility degradation in the channel and drain/source series resistance are two important parameters lim- iting 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. Index Terms—Mobility degradation, parameter extraction, se- ries resistance, SOI MOSFETs, threshold voltage, velocity satura- tion. I. INTRODUCTION A CCURATE parameter extraction becomes increasingly important and critical for device modeling, particularly for modern MOS devices with feature size approaching 0.1 m. Considerable research work [1]–[15] has been dedicated to this subject in the past ten years. Two of the most important param- eters for MOS device characterization and circuit simulation are the free-carrier mobility degradation in the channel and drain/source series resistance [4]–[8]. Mobility degradation will give rise to an effect similar to that of the drain/source series resistance on the current–voltage ( – ) characteristics [2], and Katto has suggested [3] that such an effect can be modeled as a series resistance. McAndrew and Layman [4] used nonlinear optimization to extract these two parameters, but their approach is not physics based and the extracted values may not have any physical meaning. Methods based on evaluating derivatives of the drain current have also been Manuscript received April 27, 2001; revised September 17, 2001. This work was supported by Universidad Simón Bolívar, by CONICIT (Venezuela) Grant S1–98000567, and by CONACYT (Mexico) Project N134400-A. The review of this paper was arranged by Editor C. McAndrew. F. J. García Sánchez and A. Ortiz-Conde are with Laboratorio de Electrónica del Estado Sólido (LEES), Universidad Simón Bolívar, Apartado Postal 89000, Caracas 1080A, Venezuela (e-mail: fgarcia@ieee.org). A. Cerdeira and M. Estrada are with Sección de Electrónica del Estado Sólido (SEES), Departamento de Ingeniería Eléctrica, CINVESTAV-IPN, 07300 México D.F., México (e-mail: cerdeira@mail.cinvestav.mx) D. Flandre is with Laboratoire de Microélectronique, Université, Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium. (e-mail: Flandre@dice.ucl. ac.be) J. J. Liou is with the School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, FL 32816-2450 USA and also with the Deptartment of Electronics Science and Technology, Huazhong University of Science and Technology, Wuhan, China(e-mail: jli@ece.engr.ucf.edu) Publisher Item Identifier S 0018-9383(02)00236-8. proposed [5]–[7], but using the derivatives has the disadvantage of enhancing the effect of noise on parameter extraction. Lim and coworkers [8] have proposed to measure the devices by adding an external resistance, which requires additional circuit components and complicates the extraction procedure. In this paper, we will first show that, from the saturation drain current ( ) versus gate voltage ( ) characteristics, the mo- bility degradation effect can be modeled as an effective resis- tance in series with the drain/source resistance. Second, we will develop a method to extract the total effective resistance and the transconductance parameter from the – characteristics. This method is based on a mathematical concept developed pre- viously [13]–[18], which uses integrations, instead of differen- tiation, to minimize the effect of experimental noise and error associated with the parameter extraction procedure. Finally, we will apply the method to fully-depleted (FD) SOI MOSFETs having several different channel lengths to extract the total series resistance and the mobility degradation. SOISPICE [19] simu- lation, ATLAS [20] device simulation, and measured data will be presented to support and validate the extraction method. II. DEVELOPMENT OF PARAMETER EXTRACTION METHOD Consider an n-channel FD SOI MOSFET operating in the sat- uration region and under strong inversion. The gate and drain terminals are connected together to ensure saturation operation. The saturation drain current may be expressed as [12], [13], [21], [22] (1) where is the threshold voltage (2) is the intrinsic gate-source voltage, is the extrinsic gate- source voltage, is the source series resistance (3) is the transconductance parameter with a unit of A V . In (2), is the mobility degradation parameter (4) is the low-field transconductance parameter, is the parameter that accounts for the charge coupling effects between front and 0018–9383/02$17.00 © 2002 IEEE