Latchup in cmos technology the problem and its cure pdf

Click download or read online button to get cmos latch up modeling and prevention book now. We will provide a first quick look on what latchup is. Cmos technology was initially proposed in 1962, however, this was not applied until the 1980s decade for his low velocity and larger area consumption. As a result, this is fully consistent with the device simulation in time domain shown in figs.

Keep the sourcedrain of the mos device not in the well as far away from the well as possible. In some cases latchup can be a temporary condition that can be resolved by power cycle, but unfortunate. Magnetooptical observation of the latchup effect in cmos. Vlsi, computer architecture and digital signal processing engineering and computer science kluwer international series in engineering and computer science. Request pdf latchup complementary metaloxide semiconductor cmos latchup is a fundamental. In this book the author attempts to provide a comprehensive approach to the problem of latchup in cmos integrated circuits. The book provides engineers involved in the design of cmos technologies with a good understanding of the device physics of latchup and the techniques available to avoid it. Download for offline reading, highlight, bookmark or take notes while you read satellite technology.

Transientinduced latchup in cmos integrated circuits. Well you can think latch up as a short circuit between the supply and ground. One of the most critical problems in cmos fabrication is the technique used to create a pattern. What is needed is a more general, more systematic treatment of the latchup problem. Notice the two transistors, npn and pnp and their connection to vdd and gnd supply rails.

These parasitic transistors are interconnected in such a way as to form fourlayer devices. Simple circuit techniques and attention to system design details will ensure that the cmos full potential can be realized in all operating environments. Latchup protection for mosfet drivers microchip technology. With each new cmos technology the latchup sensitivity and effects of prevention strategies change. May, 2002 a new application of garnet films with high faraday rotationthe first direct observation of latchup effect in serially produced complementary metaloxidesemiconductor integrated circuits cmos icsis reported. An artificial intelligence approach to vlsi routing by r. It usually consists of a ring structure of pn junctions around a power transistor. Latchup in cmos technology the problem and its cure. Everyday low prices and free delivery on eligible orders. Latchup cause, effect and prevention allthingsvlsi. In this book the author attempts to provide a comprehensive approach to the problem of latchup in cmos integrated.

The nmos and pmos circuits form parasitic pnpn structures that can be. 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. This concern is becoming more widespread with the ascendency of cmos as the dominant vlsi. Latchup in cmos technology the problem and its cure r. Latchup was not considered a reliability issue for commercial semiconductor. Pdf impact of ionic implantation energy in latchup by.

Transientinduced latchup in cmos integrated circuits ming. The structure formed by these resembles a silicon controlled transistor scr. The cmos latch schematic is drawn and the triggering. Seu and latchup tolerant advanced cmos technology abstract selected microcircuits constructed in national semiconductors facttm technology were tested for heavy ion induced single event upset seu and 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. In this chapter, a brief overview of latchup is provided. Cmos technology introduction classification of silicon technology silicon ic technologies bipolar bipolar cmos mos junction isolated dielectric isolated oxide isolated cmos pmos aluminum gate nmos aluminum gate silicon gate aluminum gate silicon gate silicongermanium silicon 03121101 ece 4420 cmos technology 121103 page 2. Simply defined, latchup is a functional chip failure associated with excessive current going through the chip, caused by weak circuit design. Clear methodologies that grant protection from latchup, with insight into the physics, technology and circuit issues involved, are in increasing demand. Cmos technology is also used for several analog circuits such as image sensors, data converters, and highly integrated transceivers for many types of communication. As with any cmos technology, iso cmos contains certain parasitic bipolar structures associated with its output devices and input protection circuitry.

Guard ring structures are often applied to the io cell to prevent the latchup in the bulk cmos ics. Latchup refers to short circuit formed between power rails in an ic leading to high current and damage to the ic. An excellent treatise on the subject of latchup in general can be found in the. Here is a typical bulk cmos device a simple inverter now, here is the same figure showing the parasitic bjts that cause latchup. Cmos technologies have largely converged on pbulk substrates. Feedback supported isolation structure for blocking of. In case of any spike in the power supply, one of the parasitic bjt gets on d. In the 1970s early work on cmos latchup was underway for space applications. Latchup has been, and continues to be, a potentially serious cmos reliability concern. Magnetooptical observation of the latchup effect in cmos ics. Research and development into the causes led to several papers in the 1980s discussing causes and methods to lessen the influence of latchup. A new compact model for external latchup sciencedirect. Latchup semiconductors electronic materials general.

Many modern ics incorporate structures to reduce latchup affects. Cmos latchup guard rings latchup latchup causes latchup effects latchup prevention post. Latch up in cmos what is latch up in cmos design and ways to prevent it. Keith sabine, product manager at eda firm pulsic, discusses circuit latchup and its prevention. Figure 3 scr currentvoltage characteristic looking at fig. Latchup is a parasitic and intrinsic effect on cmos technology. Latchupaware placement and parasiticbounded routing of custom analog cells. Latchup in integrated circuits from energetic protons. Thus, although the latchup effect is no longer a problem with modern cmos. In order to prevent signal corruption and latchup in power integrated circuits ics,, junction isolation ji is the most commonly used technique. Cmos technology is used in microprocessors, microcontrollers, static ram, and other digital logic circuits.

Latchupaware placement and parasiticbounded routing of. This is just one of the solutions for you to be successful. Edmonds jet propulsion laboratory california institute of technology pasadena, california abstract proton latchup was investigated for several cmos integrated circuits, including a modern microprocessor. Series kluwer international series in engineering and computer science. Cmos technology introduction classification of silicon technology silicon ic technologies bipolar bipolarcmos mos junction isolated dielectric isolated oxide isolated cmos pmos aluminum gate nmos aluminum gate silicon gate aluminum gate silicon gate silicongermanium silicon 03121101 ece 4420 cmos technology 121103 page 2. The cmos structure is analyzed and the pnp and npn latching transistors are identified. When a cmos circuits is triggered in latchup a circuit malfunctioning or circuit destroying can occur. In some cases latchup can be a temporary condition that can be resolved by power cycle, but unfortunately it can also cause a fatal chip failure. 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. Ece 4420 latchup page 2 preventing latchup in a pwell technology 1. While this article specifically addresses problems with cmos switches, it is generally applicable to all cmos devices, including digital isolators. Designers can also look forward to the day, in the not too distant future, when even these few simple precautions will no longer be.

In the early 1980s, cmos latchup and electrostatic discharge esd phenomenon of significant interest. 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. Cmos latch up modeling and prevention download ebook pdf. The effects of varying both the shallow trench isolations sti dimension and geometrical spacings on latchup behavior for 0. The book all semiconductor device engineers must read to gain a practical feel for latchup induced failure to produce lowercost and higherdensity chips. 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. Because of the wide variety of cmos technologies and the long term interest in latchup, some overall guiding principles are needed. He begins by demonstrating the need for understanding parasitic latchup behavior and a historical overview of it. A new latchup prevention design by adding the additional internal double guard rings between inputoutput cells and internal circuits is first reported in the literature, and its effectiveness has. It happens because of the formation of two parasitic bjts one pnp and another npn in cmos. Despite all of its advantages, using a lowdoped substrate comes with.

A problem which is inherent in the pwell and nwell processes is due to relatively large number of junctions which are formed in these structures, the consequent presence of parasitic diodes and transistors. Products built in these technologies must adhere to stringent guidelines for latchup hardness, and for this reason characterisation of new technologies is needed through the use of test structures. As a starting point, this discussion will be followed by. In cmos processes, these transistors can create problems when the combination of nwellpwell and substrate results in the formation of parasitic npnp struct. In cmos technology, these are typically parasitic devices. The following diagram is a drawing of a typical cmos circuit. This book provides a firm foundation in existing smart cmos image sensor technology and applications, preparing you for the next phase of smart cmos image sensors. A new application of garnet films with high faraday rotationthe first direct observation of latchup effect in serially produced complementary metaloxide. The devices showed no signs of heavy ion induced latchup for let values up to 120 mevmgcm2. Electroluminescence measurements with temporal and spatial resolution for cmos latchup investigations j. An932 seu and latch up tolerant advanced cmos technology.

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. Methodology on extracting compact layout rules for latchup. As such, scr devices are present at both the inputs and outputs of iso cmos circuits. Latchup in integrated circuits from energetic protons a. Magnetooptical observation of the latchup effect in cmos ics induced by uniform and local irradiation. Jun 18, 2012 the cmos structure is analyzed and the pnp and npn latching transistors are identified. All cmos ics have latchup paths, but there are several design techniques that reduce susceptibility to latchup. The cmos latch schematic is drawn and the triggering methods are discussed. The lowpower advantage of cmos technology made it the best choice for implementing. Failure analysis and solutions to overcome latchup failure. Caswell, an improved input protection circuit for cmos sos array, ieee transactions on electron devices, vol. By developing an understanding of the aspects of circuit and system. An approach to determine the maximum circuit delay using.

Msan107 understanding and eliminating latchup in cmos. In cmos technology, there are a number of intrinsic bipolar junction transistors. This requires more current before latchup can occur. Microelectronic engineering 12 1990 157162 157 elsevier science publishers b. 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. Electroluminescence measurements with temporal and spatial. At same time, cmos requires more complicated fabrication process than nmos technology and special careful in the latchup prevention, a destructive, parasitic, and intrinsic effect to cmos. Latchup has been, and continues to be, a potentially serious cmos reliability. Latchup can occur at io cells or at internal circuits of a cmos ic because the parasitic latchup pnpn paths exist in both io cells and internal circuits of a cmos ic. While switching inductive loads the drain of the transistor can become negatively biased injecting substantial amounts of minority charge. In bulk cmos technology, latchup immunity can be improved by some advanced cmos processes, 68. 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. 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. A good understanding of semiconductor device physics is essential to take full advantage of the discussions in the book.

Principles and applications, edition 2 ebook written by anil k. Frank wanlass patented cmos in 1967 us patent 3,356,858. Download citation latchup in cmos latchup is a failure mode in cmos circuits. A latchup is a type of short circuit which can occur in an integrated circuit ic. This paper shows a numerical simulation approach which can determine the relative. Early cmos processes suffered a reliability concern that became known as latchup. Analog dialogue 3505 2001 article, winning the battle against latchup in cmos switches. However, in device simulation, vdd is not pulleddown to its latchup holding voltage iv due to the native limitation of the. The two transistors are protected by resistors but if examined more closely, theres an scr device that could possibly be triggered. 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. In order to prevent latchup issue in bulk cmos ics, the guard ring structures and substratewell pickups are often added to the io cells and internal circuits, respectively 24.

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