A scalable SCR compact model for ESD circuit simulation

Abstract

A scalable, compact model for SCR-based ESD-protection devices, which can simulate transient voltage overshoots observed on the timescale of charged device model (CDM) events, is presented. This model captures the effect that layout spacings have on SCR characteristics such as holding voltage and trigger current. Bias and time dependencies of SCR on-resistance are captured with a resistance model that accounts for self-heating and velocity saturation. [Keywords: Electrostatic discharge (ESD), silicon controller rectifier (SCR), compact modeling.]

A physics-based compact model for SCR devices used in ESD protection circuits

“…1) have the highest current densities and therefore the highest Joule heating. The increased differential resistance of SCRs at high currents is captured by modeling the emitter resistors as explicit functions of temperature; self-heating of and thermal diffusion away from these regions is modeled using a first order RC thermal equivalent circuit [2] [7]. The model equations are summarized in Table 1.…”

“…The parameters that have a non drawn dimensions are the transit current gains β N0 and β P0 , and the Each transit time is modeled as a relevant drawn dimension, with an [2]. This model is justified by ob diffusion contribute to charge flow transit times that are linearly and q path length, respectively.…”

“…This model is justified by ob diffusion contribute to charge flow transit times that are linearly and q path length, respectively. It is well k β is not a linear function of base w modeled using a simplified versio presented in [2].…”

“…Recent works have presented CDM-relevant compact models for SCR-based CMOS protection devices [2]- [6]; however, [2]- [4] are the most applicable to modern CMOS SCRs, as [5]- [6] focus on low voltage triggered SCRs, which turn on more slowly than more recent SCR designs. This paper Figure 1: Representative cross-section of an SCR in a low voltage CMOS process, including the P+ guard ring.…”

“…presents a physics-based model that addresses shortcomings in the previous works. The model parameters are scalable with respect to the layout spacings, a feature shared by the most advanced previous models [2] [4]. An SCR may be described as consisting of cross-coupled bipolar transistors; here, it will be shown that the collector current of one transistor induces an electric field in the base of the other, which affects the current gain of the second transistor.…”