In this chapter, a brief overview of latchup is provided. Latchup cause, effect and prevention allthingsvlsi. 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. The technology impact is examined from three complementary points of view. The two transistors are protected by resistors but if examined more closely, theres an scr device that could possibly be triggered.
Download citation latchup in cmos latchup is a failure mode in cmos circuits that results in either soft. Ece 4420 latchup page 2 preventing latchup in a pwell technology 1. As a result, this is fully consistent with the device simulation in time domain shown in figs. 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. Explanation of the phenomena figure 1 shows the cross section of a twotransistor cmos integrated circuit where the nmos is on the left hand side and the pmos on the right hand side. Magnetooptical observation of the latchup effect in cmos ics induced by uniform and local irradiation.
A new compact model for external latchup sciencedirect. Each contains a substrate diode injector and a pnpn device detector. Chapter 5 tlu in cmos ics in the electrical fast transient test pages 95112. Well you can think latch up as a short circuit between the supply and ground. We will provide a first quick look on what latchup is. The lowpower advantage of cmos technology made it the best choice for implementing.
The following diagram is a drawing of a typical cmos circuit. Msan107 understanding and eliminating latchup in cmos. An artificial intelligence approach to vlsi routing by r. Transientinduced latchup in cmos integrated circuits. In some cases latchup can be a temporary condition that can be resolved by power cycle, but unfortunate. Chapter 6 methodology on extracting compact layout rules for latchup prevention pages 1150.
Dependence of device structures on latchup immunity in a high. As with any cmos technology, isocmos contains certain parasitic bipolar structures associated with its output devices and input protection circuitry. The book all semiconductor device engineers must read to gain a practical feel for latchup induced failure to produce lowercost and higherdensity chips. The trigger current i trig more than doubled from 14 to 32 ma, while the current gain of the npn. Troutman wrote the first textbook on cmos latchup, cmos latchup.
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. These parasitic transistors are interconnected in such a way as to form fourlayer devices. The book all semiconductor device engineers must read to gain a practical feel for latchupinduced failure to produce lowercost and higherdensity chips. 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. Despite all of its advantages, using a lowdoped substrate comes with. While the designer of cmos integration technologies relies on the fact that the devices to be integrated onto the same substrate are electrically isolated from each other, yet this hardly is the case. Edmonds jet propulsion laboratory california institute of technology pasadena, california abstract proton latchup was investigated for several cmos integrated circuits, including a modern microprocessor. 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. Latchup failure in cmos technology an analysis of latchup failure, an effect of parasitic bipolar transistors, in cmos technology.
Latchup in a cmos integrated circuit, causes unintended currents will possibly resulting with the destruction of the entire circuit, thus, it must be prevented. A cmos circuit is created to allow a path always to exist from the. With the development of the cmos memory technology numerous publications presented select cmos memory circuit and architecturedesigns, but these. This chapter introduces latchup benchmark test structures and test procedures to quantify. Comparison of latchup immunity for silicided sourcedrain at. Understanding latchup in advanced cmos logic latchup has long been a bane to cmos ic applications. Principles and applications, edition 2 ebook written by anil k. 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. This requires more current before latchup can occur. As with any cmos technology, iso cmos contains certain parasitic bipolar structures associated with its output devices and input protection circuitry. Simply defined, latchup is a functional chip failure associated with excessive current going through the chip, caused by weak circuit design. A ptype substrate and twintub cmos technology are assumed. A new application of garnet films with high faraday rotationthe first direct observation of latchup effect in serially produced complementary metaloxide.
However, in device simulation, vdd is not pulleddown to its latchup holding voltage iv due to the native limitation of the. The significance of this work is associated with the growing problem of cmos latchup events due to cable discharge in systems, boards and chips in advanced cmos technologies. Lecture 190 cmos technology, compatible devices 102801 page 19010. As such, scr devices are present at both the inputs and outputs of iso cmos circuits. Latchup is a cmos integrated circuit failure mechanism characterized by. Here is a typical bulk cmos device a simple inverter now, here is the same figure showing the parasitic bjts that cause latchup. 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. Everyday low prices and free delivery on eligible orders. The two transistors are protected by resistors but if examined more closely, theres. In case of any spike in the power supply, one of the parasitic bjt gets on d. With each new cmos technology the latchup sensitivity and effects of prevention strategies change.
A wellsource structure that provides a design goal for enhancing latchup immunity in vlsi full cmos ram without additional fabrication steps and performance degradations is described. Failure analysis and solutions to overcome latchup failure. Download ebook fs250 parts manual fs250 parts manual this is likewise one of the factors by obtaining the soft documents of this fs250 parts manual by online. Latchup in integrated circuits from energetic protons a. Dependence of device structures on latchup immunity in a.
The problem and its cure the springer international series in engineering and computer science 1986 by troutman, r. The cmos latch schematic is drawn and the triggering methods are discussed. Transientinduced latchup in cmos integrated circuits ming. Problem cure by troutman rr abebooks register free to download files file name. Request pdf latchup complementary metaloxide semiconductor cmos latchup is a fundamental. Latchup has been, and continues to be, a potentially serious cmos reliability. The cmos structure is analyzed and the pnp and npn latching transistors are identified. 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. 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.
It happens because of the formation of two parasitic bjts one pnp and another npn in cmos. In this book the author attempts to provide a comprehensive approach to the problem of latchup in cmos integrated circuits. As a starting point, this discussion will be followed by. Latch up in cmos what is latch up in cmos design and ways to prevent it. Cmos technology was initially proposed in 1962, however, this was not applied until the 1980s decade for his low velocity and larger area consumption. Magnetooptical observation of the latchup effect in cmos ics. The applications engineer and systems designer, however, are not so much concerned with the theory and modeling of latchup as they are. Latchup is a cmos integrated circuit ic failure mechanism characterized by excessive current flow between a power supply and its ground rail 1. Thus, although the latchup effect is no longer a problem with modern cmos. A latchup is a type of short circuit which can occur in an integrated circuit ic. The respective influence of the lightly doped and epitaxial wafers is detailed. Lecture 190 cmos technology, compatible devices 102801 page 19014.
Latchup in cmos technology the problem and its cure r. Latchup has been, and continues to be, a potentially serious cmos reliability concern. Magnetooptical observation of the latchup effect in cmos. Cmos technologies have largely converged on pbulk substrates. An932 seu and latch up tolerant advanced cmos technology. In cmos technology, these are typically parasitic devices. We conclude that i coll crit is correlated with the internal latchup trigger current. This paper shows a numerical simulation approach which can determine the. Fabrication process steps changing the substrate characteristics are addressed for cmos and bipolar technologies.
Modeling and understanding of external latchup in cmos. Guard ring structures are often applied to the io cell to prevent the latchup in the bulk cmos ics. A good understanding of semiconductor device physics is essential to take full advantage of the discussions in the book. Keep the sourcedrain of the mos device not in the well as far away from the well as possible. Duality an important characteristic of a cmos circuit is the duality that exists between its pmos transistors and nmos transistors. 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. Latchup in integrated circuits from energetic protons. 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. The devices showed no signs of heavy ion induced latchup for let values up to 120 mevmgcm2.
As such, scr devices are present at both the inputs and outputs of isocmos circuits. He begins by demonstrating the need for understanding parasitic latchup behavior and a historical overview of it. Notice the two transistors, npn and pnp and their connection to vdd and gnd supply rails. Cmos available for download and read online in other formats. By valerian lalucaa, vincent goiffon, pierre magnan, guy rolland and sophie petit. The problem and the cure comparison of latchnp in pand nwell. 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. Chapter 7 special layout issues for latchup prevention pages 151168. 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. Comparison of latchup immunity for silicided sourcedrain.
Download for offline reading, highlight, bookmark or take notes while you read satellite technology. In this paper, hv latchup characteristics under jedec latchup current test are investigated. Jun 18, 2012 the cmos structure is analyzed and the pnp and npn latching transistors are identified. Complementary metaloxide semiconductor cmos latchup is a fundamental issue inherent in cmos technology. You might not require more get older to spend to go to the books start as competently as search for them.