Ker and hsu introduce the phenomenon and basic physical mechanism of latchup, explaining the critical issues that have resurfaced for cmos. Device crosssection of a cmos device showing the parasitic bipolar transistors. The structure formed by these resembles a silicon controlled transistor scr. Pdf the physics of cmos latchup latchup under high power microwave radiation is discussed. Speaking about cmos transistors, latch up is the phenomenon of low impedance path in cmos between power rail and ground rail due to interaction between parasitic pnp and npn transistors. Latchup is defined as the generation of a lowimpedance path in cmos chips between the power supply v dd and the ground gnd due to the interaction of parasitic pnp and npn bipolar junction transistors bjts these bjts form a silicon controlled rectifier scr with positive feedback and virtually short circuit v dd to the ground, thus causing excessive current flows and even. This concern is becoming more widespread with the ascendency of cmos as the dominant. The following diagram is a drawing of a typical cmos circuit. Q1 and q2 are parasitic transistor elements residing inside it. Abnormal applications and misuse of cmos ics may still pose problems that the cmos vendor has little control over. Q1 is double emitter pnp transistor whose base is formed by n well substrate of pmos, two emitters are formed by source and drain terminal of pmos and collector is formed by substratep type of nmos.
Proton latchup was investigated for several cmos integrated circuits, including a modern microprocessor. Cmos 2 composition the main principle behind cmos circuits that allows them to implement logic gates is the use of ptype and ntype metaloxidesemiconductor fieldeffect transistors to create paths to the output from either the voltage source or. The book all semiconductor device engineers must read to gain a practical feel for latchupinduced failure to produce lowercost and higherdensity chips. However, when properly applied, cmos devices are quite insensitive to actual conditions that exist in most systems. Latchup is the condition in which the paracitic components give rise to the establishment of low resistance conducting paths between vdd and ground. A t rac ed byh m nv g s o f cmos devices, designers using them for the. To understand latch up we need to understand the various parasitic components in a cmos. Transientinduced latchup in cmos integrated circuits. As a result, the majority of single event upset seu and latchup sel test data has. Latchup refers to short circuit formed between power rails in an ic leading to high current and damage to the ic.
The proton latchup cross sections of these devices differed by more than two orders. Dependence of device structures on latchup immunity in a high. Additionally, the thyristor might be triggered by a high supply voltage far higher than the value given in data sheets. Pdf latch up effect under electromagnetic pulse researchgate. A latchup is a type of short circuit which can occur in an integrated circuit ic. Cmos latch up modeling and prevention download ebook pdf. Mar 30, 2019 hello everyone, this videos explains the latchup phenomenon in cmos circuits. Evidence of the latchup domino effect is seen in that. Latchup is defined as the generation of a lowimpedance path in cmos chips between the power supply v dd and the ground gnd due to the interaction of parasitic pnp and npn bipolar junction. Interest in latchup is being renewed with the evolution of complimentary metaloxide semiconductor cmos technology, metaloxidesemiconductor fieldeffect.
Latchup is the condition in which the paracitic components give rise to the establishment of low resistance conducting paths between vdd and. Latchup is a condition where a low impedance path is created between a supply pin and ground. The most likely place for latchup to occur is in pad drivers, where large voltage transients and large currents are present. In the past, the bias voltage vdd applied to cmos logic devices in satellite payloads has typically been held at about 5v. Holding voltages observed after triggering each test structure into latchup with the frontside spa laser at 85 c for 1. Methodology on extracting compact layout rules for latchup prevention 321 fig. Edn power management can cause latchup in cmos chips.
This network forms the pnpn scr power device which. Latchup cause, effect and prevention allthingsvlsi. Sini mukundan march 21, 2018 march 21, 2018 2 comments on cmos latchup latchup is a condition where a low impedance path is created between a supply pin and ground. Once thepart latches, the currents go way up, but it is too late. Early cmos processes suffered a reliability concern that became known as latchup. Shown alongside is a cmos transistor consisting of an nmos and a pmos device.
An600 understanding latchup in advanced cmos logic on. As a starting point, this discussion will be followed by. Nanometer cmos ics download ebook pdf, epub, tuebl, mobi. Cmos device can directly cause latchup through base collector leakage or breakdown mechanisms. Subscribe this channel for more videos on physical design fundamentals. A listing of on semiconductors productpatent coverage may be accessed at.
More specifically it is the inadvertent creation of a lowimpedance path between the power supply rails of a mosfet circuit. May 04, 20 here is a typical bulk cmos device a simple inverter now, here is the same figure showing the parasitic bjts that cause latchup. Co py latchup is a state where a semiconductor device undergoes a highcurrent state as a result of interaction between a pnp and an npn bipolar transistor. Dependence of device structures on latchup immunity in a highvoltage 40v cmos process with drainextended mosfets shengfu hsu, member,ieee, and mingdou ker, seniormember,ieee abstractthe dependence of device structures on latchup immunity. More specifically it is the inadvertent creation of a lowimpedance path between the power supply rails of a mosfet circuit, triggering a parasitic structure which disrupts proper functioning of the part, possibly even leading to its destruction due to overcurrent. Developing a transient induced latchup standard for testing. In this chapter, a brief overview of latchup is provided. Unfortunately, the twin well cmos structure always contains a pair of parasitic bipolar transistors figs. Dependence of device structures on latchup immunity in a highvoltage 40v cmos process with drainextended mosfets shengfu hsu, member,ieee, and mingdou ker, seniormember,ieee abstractthe dependence of device structures on latchup immunity in a 0. Vendors of cmos ics have always been aware of the latchup phenomenon and have considerably improved their designs and processes to reduce the danger of latchup occurring under normal usage. Ece 4420 latchup page 2 preventing latchup in a pwell technology 1. Cmos 2 composition the main principle behind cmos circuits that allows them to implement logic gates is the use of ptype and ntype metaloxidesemiconductor fieldeffect transistors to create paths to the. This requires more current before latchup can occur.
A modeling approach that takes differences in charge collection processes for longand shortrange particles into account was effective in. It resulted in circuits either malfunctioning or consuming excessive power, and could be either inherent in the design or triggered by voltage spikes on io pads that could forward bias pn junctions they were connected to. Interest in latchup is being renewed with the evolution of complimentary metaloxide semiconductor cmos technology, metaloxidesemiconductor fieldeffect transistor mosfet scaling, and highlevel systemon. Heavy ion single event latchup sel test results for the. Developing a transient induced latchup standard for. Interest in latchup is being renewed with the evolution of complimentary metaloxide semiconductor cmos technology, metaloxidesemiconductor fieldeffect transistor mosfet scaling, and highlevel systemonchip soc integration. Latchup has been, and continues to be, a potentially serious cmos reliability concern. Simply defined, latchup is a functional chip failure associated with excessive current going through the chip, caused by weak circuit design. The book all semiconductor device engineers must read to gain a practical feel for latchup induced failure to produce lowercost and higherdensity chips. Msan107 understanding and eliminating latchup in cmos.
Npn and pnp bipolar transistors which most frequently participate in latchup. This site is like a library, use search box in the widget to get ebook that you want. Complementary metaloxidesemiconductor cmos, also known as complementarysymmetry metaloxidesemiconductor cosmos, is a type of metaloxidesemiconductor fieldeffect. Basten b a waferfab an, b consumer systems nijmegen.
Dependence of device structures on latchup immunity in a. In some cases latchup can be a temporary condition that can be resolved by power cycle, but unfortunate. Latchup test considerations for analogtodigital converters. However, the key factor in latchup sensitivity is the external resistance across the baseemitter junctions of the two parasitic transistors, not the transistor gain 11. Cmos process flow cmos semiconductor device fabrication. The cmos structure contains parasitic bipolar transistors that have the potential to destroy the cmos circuitry. One aspect of high power supply voltages that is not often recognized. When a transitory voltagecurrent overshootundershoot at a. We will provide a first quick look on what latchup is. Latchup in integrated circuits from energetic protons. Cmos devices as well as those considering cmos designs for the. The proton latchup cross sections of these devices differed by more than two orders of magnitude. As a result, the majority of single event upset seu and latchup sel test data has been obtained at this voltage. New latchup mechanism in complementary bipolar power ics.
Understanding a few facts will resolve both of these situations. Clear methodologies that grant protection from latchup, with insight into the physics, technology and circuit issues involved, are in increasing demand. Although such techniques can solve the latchup problem, they increase the cost of production. Sini mukundan march 21, 2018 march 21, 2018 2 comments on cmos latchup. In some cases latchup can be a temporary condition that can be. If the gains are such that b1 x b2 1, latchup may occur. Transientinduced latchup in cmos integrated circuits equips the practicing engineer with all the tools needed to address this regularly occurring problem while becoming more proficient at ic layout. Once latchup has begun, the only way to stop it is to reduce the current below a critical level, usually by removing power from the circuit. Crosssectional view of using double guard rings to block the latchup path in an io cell. Latchup is a parasitic effect in cmos technology, this is a pnpn parasitic structure formed by at least two coupled bipolar transistors.
Results the devices were exposed to a fluence of 107 particlescm2 of iodine ions with no single event transients or latchup. Latch up problem in cmos vlsi design vlsi design latchup is defined as the generation of a lowimpedance path in cmos chips between the power supply v dd and the ground gnd due to the interaction of parasitic pnp and npn bipolar junction transistors bjts. Transientinduced latchup in cmos integrated circuits ming. Notice the two transistors, npn and pnp and their connection to vdd and gnd supply rails. Layout example of an inverter output buffer in the io cell with double guard rings to prevent latchup in a 0.
A diagram of a fourregion device in a typical nwell cmos circuit is shown in figure 1. I am currently stock on a concept i should understand but i cannot get my head around it quite yet. Keep the sourcedrain of the mos device not in the well as far away from the well as possible. Basically sp ak ing, y lo r dtv cf b one of the many cmos processes available, can be made to latchup if stressed severely enough. This document describes and discusses the topic of cmos latchup ranging from theory to testing of products. Methodology on extracting compact layout rules for latchup. This concern is becoming more widespread with the ascendency of cmos as the dominant vlsi technology. Allen 2016 latchup triggering latchup of the scr can be triggered by two.
Philips semiconductors, gerstweg 2, 6534ae nijmegen, the netherlands abstract. The nmos and pmos circuits form parasitic pnpn structures that can be. Screenshot of many latchup test structures, labeled a through r, that are biased through the same four pads. Click download or read online button to get nanometer cmos ics book now. Latchup, esd, and other phenomena 5 the parasitic thyristor can be triggered by a rapid rise of the supply voltage. This effect often was observed in earlier generations of cmos circuits. Latchup and its prevention in cmos devices vlsi universe. A cmos device on the edge of latchup hasminiscule collector current to begin with, so the beta is high. Single event upset and latchup consider for cmos devices. However, the key factor in latchup sensitivity is the external resistance across the baseemitter junctions of the two parasitic. The period of time between successive applications of trigger pulses, or. Slya014a latchup, esd, and other phenomena 5 the parasitic thyristor can be triggered by a rapid rise of the supply voltage.
During the period from 1295 to 997, these evaluations resulted. This article will briefly describe the causes, mechanism, and consequences of latchup and discuss available prevention. Layout example of an inverter output buffer in the io cell with double guard rings to prevent. Basten b a waferfab an, b consumer systems nijmegen, email. Lecture 08 latchup and esd 42516 page 086 cmos analog circuit design p. New latchup mechanism in complementary bipolar power. Cmos layout layers mask layers for 1 poly, 2 metal, nwell cmos process background. Holding voltages observed after triggering each test structure into. Speaking about cmos transistors, latch up is the phenomenon of low impedance path between power rail and ground rail due to interaction between parasitic. This concern is becoming more widespread with the ascendency of cmos as the dominant vlsi technology, particularly as parasitic bipolar characteristics continue to improve at ever smaller dimensions on silicon wafers with ever lower defect densities. Speaking about cmos transistors, latch up is the phenomenon of low impedance path in cmos.