This document reviews SCR-based ESD protection designs for RF integrated circuits (ICs) operating at frequencies of 30 GHz and 60 GHz. It discusses the importance of ESD protection in CMOS technology, detailing the advantages of using SCR devices to minimize performance degradation while maintaining robustness against electrostatic discharge. The paper presents design guidelines and specific configurations for effectively implementing these protection mechanisms in RF applications.

1. Invention Journal of Research Technology in Engineering & Management (IJRTEM)
ISSN: 2455-3689
www.ijrtem.com Volume 1 Issue 5 ǁ July. 2016 ǁ PP 08-10
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SCR-Based ESD Protection Designs for RF ICs
Chun-Yu Lin
Department of Electrical Engineering, National Taiwan Normal University, Taipei, Taiwan
Abstract: CMOS technology has been used to implement the radio-frequency integrated circuits (RF ICs). However, it was known that
advanced CMOS technologies seriously degrade the electrostatic discharge (ESD) robustness of ICs. Therefore, on-chip ESD
protection devices must be added into the chip, including RF ICs. To minimize the impacts from ESD protection devices on RF
performances, the ESD protection at RF pads must be carefully designed. A review on ESD protection designs with silicon-controlled
rectifier (SCR) devices in RF ICs is presented in this article.
Keywords: CMOS, ESD, RF, SCR.
I. Introduction
All integrated circuits (ICs), including radio-frequency (RF) ICs, must meet the reliability specifications during mass production.
Electrostatic discharge (ESD), which is one of the most important reliability issues during mass production, must be taken into
consideration [1]. All integrated circuits used in the wireless communication products need to be equipped with ESD protection designs.
However, ESD protections cause RF performance degradation with several undesired effects. Parasitic capacitance is one of the most
important design considerations for RF ICs. A typical specification for a giga-Hertz RF circuit on human-body-model (HBM) ESD
robustness and the maximum parasitic capacitance of ESD protection device are 2kV and 200fF, respectively [2], [3]. As the operating
frequencies of RF circuits increase, the parasitic capacitance is more strictly limited.
The ESD protection devices used in commercial CMOS processes include the diode, MOS, BJT, field-oxide device, and
silicon-controlled rectifier (SCR). Among the ESD protection devices, the SCR device has been reported to be useful for RF ESD
protection design due to its higher ESD robustness within a smaller layout area and lower parasitic capacitance [4]. In this paper, the
SCR-based ESD protection designs for 30GHz and 60GHz applications are reviewed.
II. SCR Device
The device structure of the SCR device used in RF input (RFIN) pad is illustrated in Fig. 1(a). The SCR path between RFIN and VSS
consists of P+, N-well, P-well, and N+. The equivalent circuit of the SCR consists of a PNP BJT (QPNP) and a NPN BJT (QNPN), as shown
in Fig. 1(b). As ESD zapping from RFIN to VSS, the positive-feedback regenerative mechanism of QPNP and QNPN results in the SCR
device highly conductive to make SCR very robust against ESD stresses. However, SCR has some drawbacks, such as higher trigger
voltage and slower turn-on speed. To reduce the trigger voltage of an SCR device, the trigger signal can be sent into the base terminal
of QNPN to enhance the turn-on speed [5].
(a) (b)
Fig. 1. (a) Device cross-sectional view, and (b) equivalent circuit, of SCR device used in RF input pad.
III. SCR-Based ESD Protection Design for 30GHz Applications
An inductor-assisted SCR (LASCR) has been presented for 30GHz applications. Fig. 2 shows the design of LASCR, which consists of
an SCR, an inductor (L), and a diode string (Dtrig) [6]. The diode string is used to enhance the turn-on efficiency of SCR [7]. As ESD
zapping from RFIN to VSS, the inductor and diode string will discharge the initial ESD current, and then the SCR will be triggered on to
discharge the primary ESD current. Under normal RF operating condition, the inductor will resonate with the parasitic capacitance of

2. SCR-Based ESD Protection Designs…
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SCR, and the signal loss of LASCR can be very small. Fig. 3 shows the simulated signal loss (S21) of LASCR. At 30GHz, the LASCR
has only 0.4dB loss.
Fig. 2. SCR-based ESD protection design for 30GHz applications.
Fig. 3. Simulation results of SCR-based ESD protection design for 30GHz applications.
IV. SCR-Based ESD Protection Design for 60GHz Applications
An inductor-triggered SCR (LTSCR) has been presented for 60GHz applications. Fig. 4 shows the design of LTSCR, which consists of
an SCR device, an inductor (Ltrig), a MOS transistor (Mtrig), and an RC-inverter ESD detection circuit [8]. In this ESD protection scheme,
the dimensions of the inductor, PMOS transistor, SCR device, and diode can be designed to minimize the RF performance degradation.
The inductor is also used to provide the trigger path between the RFIN pad and the base of QNPN under ESD stress conditions. The PMOS
transistor at the trigger path, which is controlled bythe RC-inverter ESD detection circuit, is also turned on under ESD stress conditions.
The Mtrig is turned off to block the steady leakage current path from the RFIN pad to the base of QNPN under normal RF circuit operating
conditions. The simulated signal loss of this circuit is shown in Fig. 5. At 60 GHz, the LTSCR has only 0.9dB loss.
Fig. 4. SCR-based ESD protection design for 60GHz applications.

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Fig. 5. Simulation results of SCR-based ESD protection design for 60GHz applications.
V. Conclusion
A comprehensive review in the field of ESD protection designs with SCR-based devices for RF ICs is presented. These designs provide
the design guideline for on-chip ESD protection for RF circuits. The on-chip ESD protection designs for RF circuits will continuously
be an important design task, as the operating frequencies of RF circuits increase.
Acknowledgements
This work was supported by Ministry of Science and Technology, Taiwan (grant 105-2622-E-003-001-CC2).
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