1908 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 57, NO. 4, AUGUST 2010 TCAD Simulations on CMOS Propagation Induced Pulse Broadening Effect: Dependence Analysis on the Threshold Voltage J. M. Mogollón, F. R. Palomo, M. A. Aguirre, J. Nápoles, H. Guzmán-Miranda, and E. García-Sánchez Abstract—Propagation induced pulse broadening (PIPB) effect is becoming a major concern for electronic designers since new technologies are fast enough to propagate and capture Single Event Transients (SET). In this paper, we explore the influence of the MOSFET threshold voltage ( ) on PIPB effect by TCAD simulating the propagation of an SET after an ion strike, showing up this dependence by the modification of some CMOS technology parameters affecting . For this work, the test vehicle used to measure PIPB effect is a self-feedback chain of CMOS inverters. The conclusions outlined can be useful when designing with Multi- nano-metric CMOS technologies. Our results suggest that the ratio could be a figure of merit for SET propagation broadening. Index Terms—CMOS, pulse broadening, single event transient, TCAD Simulation, threshold voltage. I. INTRODUCTION S SINGLE EVENT transient (SET) propagation in an in- tegrated circuit has been already studied from different points of view. In [1] an analysis of a chain of inverters con- sidering different gate output load is done. Another approach considering fluctuations of the power supply voltage is made in [2], among many others. As technology shrinks, logic gate speed increases and SET can propagate and even get broader easily through circuitry if transient pulse width is broader than a critical minimum which depends on the technology [3]. As a consequence, the initially very fast transients are broad- ened enough through the propagation gates to become pulses that have more probability of being stored by edge triggered registers or other digital blocks giving place to data corruption. These transients can also affect analog circuits such as opera- tional amplifiers, voltage regulators [4], etc. In this work we have performed several different Sentaurus TCAD mixed-mode simulations (SPICE-2D) to show the prop- agation induced pulse broadening (PIPB) effect dependence on the voltage [5]. We have studied this dependence on the voltage by TCAD simulations of different implanted channel doping profiles since it is well known that ion implantation is used mainly to set this threshold value [6]. In this way, we can Manuscript received September 02, 2009; revised November 13, 2009; ac- cepted February 12, 2010. Date of current version August 18, 2010. The authors are with the Department of Electronics Engineering, School of Engineering, University of Sevilla, Seville, Spain (e-mail: jmmogollon@gte. esi.us.es). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TNS.2010.2043685 increase or decrease in a realistic manner and observe the correlation between pulse distortion and shifts. All simulations are carried out using the test vehicles in Figs. 2 and 3. We focus on nodes A, B, C since these nodes are balanced with respect to each other, and PIPB effect is not attributable to unbalance within them. Today Multi- nano-metric CMOS technologies offer the possibility to design choosing the threshold for each transistor in the design. With this work we try to compare the response to SET broadening of a simple circuit made up with 2D transistor models for different values of after the strike of a heavy ion. This paper is structured as follows. Section II is a brief revi- sion of the theoretical background of the paper. In Section III the circuit simulated is described. Section IV is devoted to a light introduction to the ion implantation process exploited in this work to adjust the voltage. In Section V we performed several simulations varying the doping profile parameters given in Section IV. Finally, in Section VI, the main conclusions of this work are outlined. II. THEORETICAL BACKGROUND The expected behavior for a transient pulse traveling through two inverters is shown in Fig. 1. This behavior can be figured out from the inverter Vo-Vi DC characteristic curve. In the example depicted, the low-to-high (tLH) delay is shorter than the high-to-low ( tHL) delay due to an inverter switching point voltage ( ) over . As can be seen, after the first inverter the transient pulse width is broadened. However, when passing through the second inverter the effect is reverted and the initial transient pulse width is recovered. This is the expected behavior in balanced circuits where all the inverters are identical and hence, all of them share the same . SPICE transient simulation of the circuit in Fig. 1 (replacing 2D models for SPICE models from the foundry) agrees with the theoretical prediction showing neither broadening nor nar- rowing of the transient pulse (see Section V). However, many experiments carried out by Cavrois et al. [7], [8], have shown that PIPB effect occurs in chains of SOI and bulk CMOS in- verters. To reproduce these phenomena, HSPICE models deliv- ered by the foundries in their process design kits (PDK) are not valid if used without including external parasitic elements [9]. The connection between the and the device physics can be done through the equation relating and [10] (1) 0018-9499/$26.00 © 2010 IEEE