Proc. of the 2nd International Conference on Modeling and Simulation of Microsystems (MSM99)

San Juan, Puerto Rico, U.S.A., April 19-21, 1999, pp. 423-426.

Copyright Notice

© 1999 Computational Publications. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from Computational Publications.

This paper presents a compact length-dependent saturation current (I_dsat) model for deep-submicron MOSFET’s based on accurate modeling of the threshold voltage (V_th). A predictive bias-dependent Vth model that relates to process conditions has been developed [1], [2]. An extension of the V_th model [1] is used in this work, which consists of only five important process-dependent parameters and two auxiliary DIBL parameters, namely, N_s, l, a, b, k and i, j, respectively. Each parameter has its own physical representation that characterizes the individual short-channel effects. The first parameter N_s represents an effective vertical channel nonuniform doping profile, whereas the parameters k and b characterize the reverse short channel effect (V_th roll-up). The normal short channel effect (V_th roll-off) is modeled by l and a. The auxiliary parameters i and j are introduced in this work to fine tune the DIBL dependence, which model the asymmetric nature of the source and drain depletion region at high V_ds condition. The V_th model requires a five-steps parameter extraction based on only five sets of measurement data: V_th(V_bs) at long channel, V_th(L_g, low V_ds, high V_bs), V_th(L_g, low V_ds, low V_bs),  V_th(L_g, high V_ds, low V_bs),  and V_th(L_g, high V_ds, high V_bs). With additional long-channel V_th(V_bs) data for different wafers, the V_th model can correlate to process variables such as V_th adjust implant dose and punchthrough implant energy.
Once a good V_th model is available, developing an I_dsat model is mainly a matter of mobility and series resistance modeling. The I_dsat model in [3] is employed, combined with our V_th model to predict experimental data from the same wafer. The I_dsat model considers all the important short-channel effects, which include mobility degradation, velocity saturation, as well as source/drain series resistance. The low-field mobility (m₀) and series resistance (R_s) are extracted by fitting to one set of I_dsat versus L_g data at V_ds=V_gs=V_dd. Once these two parameters are determined, a complete compact I_dsat model with drawn gate length (L_g), bias voltages (V_gs, V_ds, V_bs) and process variables (implant dose F and energy E) as input parameters is available.

The excellent prediction of the I_dsat model (lines) to the experimental data (symbols) has been demonstrated in Figs.1-4. The extracted empirical correlation between the channel doping parameter (N_s) and the implant dose and energy (shown in the insets of Figs. 3 and 4) applies equally well to the saturation current. This work demonstrates an efficient and accurate approach to modeling deep-submicron MOSFET’s, which is very useful for reducing experimental wafer spilt-lot and for process control and optimization.
 

• [1]  X. Zhou, K. Y. Lim, and D. Lim “A General Approach to Compact Threshold Voltage Formulation Based on 2-D Numerical Simulation and Experimental Correlation for Deep-Submicron ULSI Technology Development,” submitted to IEEE Trans. Electron Devices.
• [2]  K. Y. Lim, X. Zhou, D. Lim, Y. Zu, H. M. Ho, K. Loiko, C. K. Lau, M. S. Tse, and S. C. Choo, “A Predictive Semi-Analytical Threshold Voltage Model for Deep-Submicron MOSFET’s,” Proc. 1998 Hong Kong Electron Devices Meeting, Aug. 1998, pp. 114–117.
• [3]  Z.-H. Liu, C. Hu, J.-H. Huang, T.-Y. Chan, M.-C. Jeng, P. K. Ko, and Y. C. Cheng, “Threshold Voltage Model for Deep-Submicrometer MOSFET’s,” IEEE Trans. Electron Devices, vol. 40, no. 1, pp. 86–94, 1993.
• [4]  K. Chen, H. C. Wann, J. Duster, D. Pramanik, S. Naraini, P. K. Ko and C. Hu, “An accurate semi-empirical saturation drain current model for LDD N-MOSFET,” IEEE Electron Device Lett., vol. 17, no. 3, pp. 145–147, 1996.
• [5]  VLSI Electronics: Microstructure Science—Advanced MOS Device Physics, edited by N. G. Einspruch, Academic Press, New York, vol. 18, p. 18, 1988.

1. [12] X. Zhou, K. Y. Lim, and D. Lim, "A new 'Critical-Current at Linear-Threshold' method for direct extraction of deep-submicron MOSFET effective channel length," IEEE Trans. Electron Devices, Vol. 46, No. 7, pp. 1492-1494, July 1999.
2. [5] X. Zhou and K. Y. Lim, "A compact MOSFET Ids model for channel-length modulation including velocity overshoot," Proc. 1999 International Semiconductor Device Research Symposium (ISDRS-99), Charlottesville, VA, Dec. 1999, pp. 423-426.
3. [11] X. Zhou, K. Y. Lim, and D. Lim, "A general approach to compact threshold voltage formulation based on 2-D numerical simulation and experimental correlation for deep-submicron ULSI technology development," IEEE Trans. Electron Devices, Vol. 47, No. 1, pp. 214-221, Jan. 2000.
4. [3] X. Zhou and K. Y. Lim, "A novel approach to compact I-V modeling for deep-submicron MOSFET's technology development with process correlation," Proc. 3rd International Conference on Modeling and Simulation of Microsystems (MSM2000), San Diego, CA, Mar. 2000, pp. 333-336.
5. [13] K. Y. Lim, X. Zhou, and Y. Wang, "Modeling of threshold voltage with reverse short channel effect," Proc. 3rd International Conference on Modeling and Simulation of Microsystems (MSM2000), San Diego, CA, Mar. 2000, pp. 317-320.
6. [11] K. Y. Lim and X. Zhou, "A physically-based semi-empirical series resistance model for deep-submicron MOSFET I-V modeling," IEEE Trans. Electron Devices, Vol. 47, No. 6, pp. 1300-1302, June 2000.
7. [11] K. Y. Lim and X. Zhou, "A physically-based semi-empirical effective mobility model for MOSFET compact I-V modeling," Solid-State Electron., Vol. 45, No. 1, pp. 193-197, Jan. 2001.
8. [19] X. Zhou, S. B. Chiah, K. Y. Lim, Y. Wang, X. Yu, S. Chwa, A. See, and L. Chan, "Technology-dependent modeling of deep-submicron MOSFET's and ULSI circuits," (Invited Paper), Proc. 6th International Conference on Solid-State and Integrated-Circuit Technology (ICSICT-2001), Shanghai, Oct. 2001, Vol. 2, pp. 855-860.
9. [13] K. Y. Lim, X. Zhou, and Y. Wang, "Physics-Based Threshold Voltage Modeling with Reverse Short Channel Effect," J. Modeling Simulation Microsystems (JMSM), Vol. 2, No. 1, pp. 51-55, 2001.