Silicon-controlled Rectifier Structure Research Articles

Design of a LVTSCR triggered SCR device for low voltage ESD protection

In this paper, a novel silicon-controlled rectifier (SCR) electrostatic discharge (ESD) protection device, called low voltage triggered SCR (LVTSCR) triggered SCR (LVTSCRTSCR), is proposed for 3.3 V I/O protection applications in 0.18 μm CMOS technology. One side of the device is the traditional LVTSCR structure, and other side is the traditional SCR structure. The two structures are connected by a floating P+ diffusion layer. The working principle of LVTSCRTSCR was verified by the TCAD simulation results and TLP test results. The test results show that the triggering voltage of LVTSCRTSCR is determined by the traditional LVTSCR, with a value of 9.850 V. The holding voltage of the device can be effectively improved by increasing the size of the floating diffusion layer D4. When D4 = 6 μm, the holding voltage can be 4.491 V, suitable for 3.3 V I/O.

Compact and Fast Response Dual-Directional SCR for Nanoscale ESD Protection Engineering

Direct bidirectional current discharge paths between input/output (I/O) and ground (GND) are imperative to achieve robust charged device model (CDM) protection for very stringent design window in advanced low-voltage (LV) processes. In this brief, a compact and fast response dual-directional silicon-controlled rectifier (CFR-DDSCR) has been proposed. Using P-electrostatic discharge (ESD) implantation layer to implement each diode-triggered silicon-controlled rectifier (SCR) within only one n-well, the inherent defect of the prior art (i.e., the cumbersome p-well/n-well triggering diode) is eliminated, ensuring the low resistance of auxiliary triggering path and the compactness of silicon footprint. Moreover, by shielding all internal shallow trench isolation (STIs) with floating high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> metal gates (HKMGs), an all-gate-bounded SCR structure is realized, and all triggering diodes evolve into gated diodes with compact current paths, thus improving the CDM protection capability greatly. Experimental results indicate that the CFR-DDSCR, with a design window suitable for 1.2 V-CMOS technologies, acquires a higher effective CDM robustness (73% improved), a faster turn-on speed (64% improved), and a more compact layout (31% shrunk) compared with its conventional counterpart, which is promising for the advanced LV CDM protection.

Silicon-controlled Rectifier-based Electrostatic Discharge Protection Circuit with Additional NPN Parasitic Bipolar Junction Transistor for 5-V Application

This paper proposes a novel protection circuit based on a silicon-controlled rectifier (SCR) to prevent electrostatic discharge (ESD) at low voltages. The proposed device consists of an additional NPN parasitic bipolar transistor operated via application of an N+ diffusion region and a well breakdown voltage, to reduce the high trigger voltage caused by the well breakdown voltage of the existing SCR structure. Furthermore, the proposed device exhibits an improved trigger voltage, holding voltage, and dynamic resistance component when compared with existing parasitic PNP bipolar transistors. The proposed ESD protection circuit was manufactured using a 0.18 μm bipolar-CMOS-DMOS; it exhibited a significant improvement in electrical characteristics such as trigger voltage (8.1 V) and holding voltage (3.55 V), according to the results of transmission line pulse measurement. Hence, it is deemed to be suitable for 5-V-class applications.

A High Failure-Current Gate-Controlled Dual-Direction SCR for High-Voltage ESD Protection in 0.18-μm BCD Technology

To make a dual-direction silicon-controlled rectifier (SCR) that is highly robust in a high-voltage environment, a gate-controlled dual-direction SCR (GC-DDSCR) device is proposed. After analyzing the working principle of the device through the equivalent circuit and 2-D device simulation, the electro-static discharge (ESD) characteristics of the device are verified through the transmission line pulse (TLP) test. The failure current of the GC-DDSCR structure is greatly improved to 14.19 A compared with only 3.53 A of the same size traditional dual-direction SCR (TDDSCR) structure. The trigger voltage and the holding voltage of the GC-DDSCR are 24.23 and 20.15 V, respectively. In addition, this article explains the principle of GC-DDSCR devices with high protection capability. That is, because the device has a polysilicon gate electrode shorted to the anode (cathode), the electric field effect generated by the gate promotes carrier movement in the SCR path. Thus, the electric field force promotes the opening of the SCR path of the device and the direction of the electric field force is always consistent with the current direction. The overall failure capability of the device is effectively improved.

A Novel Dual-Directional SCR Structure With High Holding Voltage for 12-V Applications in 0.13-μm BCD Process

This article proposes a dual-directional silicon-controlled rectifier (SCR) with a novel structure and high holding voltage to improve the electrostatic discharge (ESD) design area efficiency in high-voltage environments. In terms of structure, by decreasing the emitter injection efficiency of the p-n-p parasitic bipolar transistor formed at the bottom of the gate region, the SCR positive feedback gain is reduced, which endows the proposed device with improved snapback characteristics compared with the conventional low-voltage triggering SCR (LVTSCR) and low-trigger dual directional SCR (LTDDSCR). This article conducted 2-D and mixed-mode simulations to compare and analyze the operating principles of the proposed and traditional devices. Additionally, experimental devices were fabricated under the same conditions using the 0.13- $\mu \text{m}$ process to verify their electrical properties and latch-up immunity by measuring the transmission line pulse (TLP) and transient latch-up (TLU). This article also conducted a detailed analysis on the optimization of electrical properties for the ESD design window of the proposed device according to the design variables and application of segment topology, and also analyzed the temperature reliability using a hot chuck control system. The measurement results reveal that the proposed device is highly suitable for the 12-V-class ESD design window, has improved reliability, and can provide excellent area efficiency in related applications.

A New SCR Structure With High Holding Voltage and Low ON-Resistance for 5-V Applications

This article proposes a new silicon-controlled rectifier (SCR)-based electrostatic discharge (ESD) protection device suitable for 5-V applications. The proposed ESD protection device has an additional n-p-n parasitic bipolar transistor that provides an extremely short ESD discharge path. Compared with the conventional Low-Voltage-Trigger SCR (LVTSCR) and Low-Ron SCR (LRSCR), it has excellent ON-resistance and improved reverse characteristics. Furthermore, it has structurally enhanced trigger voltage and holding voltage characteristics. A conventional LVTSCR, LRSCR, and the proposed ESD protection device were fabricated with the same width using a 0.18- $\mu \text{m}$ bipolar CMOS DMOS (BCD) process to verify the improvement in electrical characteristics and current driving capability of the new device. Transmission line pulsing (TLP) and a hot chuck control system were used to measure and compare the latch-up, electrical characteristics, and temperature reliability of the three devices. The measurements demonstrate that the proposed ESD protection device provides improved reliability and higher area efficiency for 5 V or similar applications.

Self-triggered stacked silicon-controlled rectifier structure (STSSCR) for on-chip electrostatic discharge (ESD) protection

In order to improve the holding voltage and keep the trigger voltage of the silicon controlled rectifier (SCR) devices, a new self-triggered stacked SCR structure (STSSCR) is proposed for on–chip electrostatic discharge (ESD) protection. The STSSCR structure consists of a modified lateral SCR (MLSCR) and multiple double trigger SCRs (DTSCRs). The trigger voltage of the structure is decided by the trigger voltage of the MLSCR. And the holding voltage is decided by the holding voltage of the SCRs and the number of the DTSCR in the STSSCR structure. The simulation and experimental results show that STSSCR has a stable trigger voltage, a small trigger current and an adjustable high holding voltage.

Cathode Side Engineering to Raise Holding Voltage of SCR in a 0.5-㎛ 24 V CDMOS Process

A set of novel silicon controlled rectifier (SCR) devices’ characteristics have been analyzed and verified under the electrostatic discharge (ESD) stress. A ring-shaped diffusion was added to their anode or cathode in order to improve the holding voltage (Vh) of SCR structure by creating new current discharging path and decreasing the emitter injection efficiency (γ) of parasitic Bipolar Junction Transistor (BJT). ESD current density distribution imitated by 2- dimensional (2D) TCAD simulation demonstrated that an additional current path exists in the proposed SCR. All the related devices were investigated and characterized based on transmission line pulse (TLP) test system in a standard 0.5-μm 24 V CDMOS process. The proposed SCR devices with ring-shaped anode (RASCR) and ring-shaped cathode (RCSCR) own higher Vh than that of Simple SCR (S_SCR). Especially, the Vh of RCSCR has been raised above 33 V. What’s more, their holding current is kept over 800 mA, which makes it possible to design power clamp with SCR structure for on chip ESD protection and keep the protected chip away from latch-up risk.

Investigation of the trigger voltage walk-in effect in LDMOS for high-voltage ESD protection

The trigger voltage walk-in effect has been investigated by designing two different laterally diffused metal—oxide—semiconductor (LDMOS) transistors with an embedded silicon controlled rectifier (SCR). By inserting a P+ implant region along the outer and the inner boundary of the N+ region at the drain side of a conventional LDMOS transistor, we fabricate the LDMOS-SCR and the SCR-LDMOS devices with a different triggering order in a 0.5 μm bipolar-CMOS-DMOS process, respectively. First, we perform transmission line pulse (TLP) and DC-voltage degradation tests on the LDMOS-SCR. Results show that the trigger voltage walk-in effect can be attributed to the gate oxide trap generation and charge trapping. Then, we perform TLP tests on the SCR-LDMOS. Results indicate that the trigger voltage walk-in effect is remarkably reduced. In the SCR-LDMOS, the embedded SCR is triggered earlier than the LDMOS, and the ESD current is mainly discharged by the parasitic SCR structure. The electric potential between the drain and the gate decreases significantly after snapback, leading to decreased impact ionization rates and thus reduced trap generation and charge trapping. Finally, the above explanation of the different trigger voltage walk-in behavior in LDMOS-SCR and SCR-LDMOS devices is confirmed by TCAD simulation.

Optimization on MOS-Triggered SCR Structures for On-Chip ESD Protection

MOS-triggered silicon-controlled rectifier (SCR) devices have been reported to achieve efficient on-chip electrostatic discharge (ESD) protection in deep-submicrometer CMOS technology. The channel length of the embedded MOS transistor in the MOS-triggered SCR device dominates the trigger mechanism and current distribution to govern the trigger voltage, holding voltage, on resistance, second breakdown current, and ESD robustness of the MOS-triggered SCR device. The embedded MOS transistor in the MOS-triggered SCR device should be optimized to achieve the most efficient ESD protection in advanced CMOS technology. In addition, the layout style of the embedded MOS transistor can be adjusted to improve the MOS-triggered SCR device for ESD protection.

An Improved Bidirectional SCR Structure for Low-Triggering ESD Protection Applications

An improved dual-polarity silicon-controlled rectifier (SCR) device has been proposed and realized in a 0.6-mum bipolar complementary metal-oxide-semiconductor process. The device can be used to protect electrostatic discharge (ESD) in both the positive and negative directions on pins with a voltage range that goes below ground. Comparing with the conventional bidirectional SCR structures, the new device is more suitable for low-voltage integrated circuit ESD protection applications because it possesses a smaller trigger voltage, a smaller leakage current, and a larger holding voltage.

ESD protection design for I/O cells with embedded SCR structure as power-rail ESD clamp device in nanoscale CMOS technology

This paper presents a new electrostatic discharge (ESD) protection design for input/output (I/O) cells with embedded silicon-controlled rectifier (SCR) structure as power-rail ESD clamp device in a 130-nm CMOS process. Two new embedded SCR structures without latchup danger are proposed to be placed between the input (or output) pMOS and nMOS devices of the I/O cells. Furthermore, the turn-on efficiency of embedded SCR can be significantly increased by substrate-triggered technique. Experimental results have verified that the human-body-model (HBM) ESD level of this new proposed I/O cells can be greater than 5 kV in a 130-nm fully salicided CMOS process. By including the efficient power-rail ESD clamp device into each I/O cell, whole-chip ESD protection scheme can be successfully achieved within a small silicon area of the I/O cell.

A new low-parasitic polysilicon SCR ESD protection structure for RF ICs

Robust low-parasitic electrostatic discharge (ESD) protection is highly desirable for RF ICs. This letter reports design of a new low-parasitic polysilicon silicon controlled rectifier (SCR) ESD protection structure designed and implemented in a commercial 0.35-μm SiGe BiCMOS technology. The concept was verified by simulation and experiment with the results showing that the new structure has much lower parasitic capacitance (C/sub ESD/) and higher F-factor than that of other ESD protection devices. A small polysilicon SCR structure of 750-μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> all-inclusive provides a high human body model ESD protection of 3.2 kV while featuring a high F-factor of /spl sim/42 and a low C/sub ESD/ of /spl sim/92.3 fF. The new polysilicon SCR ESD protection structure seems to be an attractive solution to high-GHz RF ICs.