Mathematical analysis and numerical simulation of electromigration by jon arthur wilkening b. The test structures typically consist of simple via chains, where the resistance is monitored as a function of the stress time for a sample of test devices 117. However, cu could not be patterned by conventional halogen plasma etching process because of the low vapor pressure of its compound. There will be changes in the interconnect temperature due to power dissipation of neighbouring interconnects or transistors on the chip, self heating of interconnect due to current flow, poor thermal. Pdf electromigration and its impact on physical design in future.
Pdf introduction to electromigrationaware physical design. The ions will drift in the direction of the electron flow. Implications of the theoretical analysis and the simulation results for modern interconnect design are. The most familiar are void failures along the length of the line called internal. University of arizona 1996 a dissertation submitted in partial satisfaction of the.
Cresta current estimation for cmos circuits, in proceedings of the. Electromigration testing of tialsi metallization for integrated circuits jose. Cu gapfill, cu grain growth, electromigration scaling, new materials in linerseed proposed solutions. This thickness comprises only a few layers of atoms and is approaching fundamental limits which is around 1 to 1. Noblelike metal in liner, selective metal cap, cualloy seed critical metrics. Early in cmos development, latchup was recognized as a problem to be solved. At current densities above these values, the electron wind will rearrange the metal ions, causing the metal to thin in some places and.
If the current density is high enough, there can be a momentum transfer from moving electrons to the metal ions that make up the lattice of the interconnect material. The chapters in design of high performance microprocessor circuits were written by some of the world s leading technologists, designers, and researchers. Cmos transistors with channel lengths of 100 nm or less 7. This paper presents fast and automated electromigration em reliability modeling by using automated modeling generation amg algorithm. Integrationreliability issues for culowk beol interconnects. In service, an interconnect line carries an intense electric current. While scaling enables increased clock speeds for central processing units cpus and chip densities for random access memories ram, it also opens up opportunities for photonic device fabrication. This book covers the design of next generation microprocessors in deep submicron cmos technologies. C ild k ox o wl x ox what metrics does resistance impact.
This paper summarizes the electromigration properties of thick copper lines embedded in bcb in bicmos technologies. For the first time, we demonstrate a positive application of electromigration, as an electrically programmable device in advanced cmos technology. The effect is important in applications where high direct current densities are used, such as in microelectronics and related structures. Pdf electromigration em is one of the key concerns going forward for. Temperaturedependent electromigration reliability springerlink. Pdf electromigration is increasingly relevant to the physical design of electronic circuits. The process, known as electromigration, has been the most menacing and persistent threat to interconnect reliability. Electromigration in thin films has been identified as one of the primary failure. He is the author of numerous technical papers and tutorials and holds five patents. Static electromigration analysis for signal interconnects. The length of the cu wire to be tested must be sufficiently long typically 200. Aluminium is by far the cheapest but it is worst in terms of electromigration.
We present a comprehensive physical model for the whole life cycles of electromigration induced voids. The electromigration lifetime test uses highcurrent densities and high temperatures to accelerate the fails. Upon programming, efuses show a large increase in resistance that enable easy sensing. Predicting electromigration mortality under temperature and. When interfacing the bpr with ru m0a lines through a ru via contact, excellent resistance values and electromigration behavior have been.
The conduction electrons impact metal atoms, and motivate the atoms to diffuse in the direction of electron flow. Electromigration occurs when and an electric field voltage difference is present. A statistical approach to electromigration design for high. Electromigration is thus controlled by specifying the minimum width w to keep j below a max. Failure occurs at the top or bottom of a wplug via. Electromigration is generally considered to be the result of momentum transfer from the electrons, which move in the applied electric field, to the ions which make up the lattice of the interconnect material. The vacancies can grow and eventually break circuit connections resulting in opencircuit, while the. Special emphasis is put on explaining the void morphology and its impact on interconnect resistance. Electrolytic electromigration requires moisture on the surface and a high electric. Nov 30, 2018 complementary metaloxidesemiconductor cmos based integrated circuits use metal interconnect wires, which are made of aluminium and, more recently, copper, to provide electrical connections. It is desirable to designin reliability of vlsi circuits by a judicious choice of. As the structure size in electronics such as integrated circuits decreases, the practical significance of this effect increases.
Electromigration failures may result whenacurrent flows through an onchip wire over a long period of time, causinga. Wplug via electromigration in cmos process journal of. It is shown that activation energy in the cubcb architecture is quite low, and copper migration might preferentially occur at cubarrier. Eguchi, temperature measurement of ai metallization and the study of blacks model in high current density, in proceedings of the ieee international reliability physics symposium, pp. Scanning electron micrograph picture of a multilevel cmos integrated circuit with the intermatallic dielectric etched away. The nmos and pmos circuits form parasitic pnpn structures that can be. Reliability wearout mechanisms in advanced cmos technologies. A chiplevel electromigration reliability diagnosis. In this model, the expected lifetime of the overall system of interconnects is determined from the failure probability of the individual wire segments. Multisite onchip current sensor for electromigration monitoring. The effect of polyimide passivation on the electromigration of cu. Test done at 220c and a current density of 10 6 acm 2. There are several other factors, such as, topology, passivation layers.
Arrhenius plot of timetofailure of cu thin films j 8 macm2. We analyze the failure mechanism of wplug via electromigration made in a 0. Reference 6 is invaluable for its visual documentation of how electromigration progresses and ends with an open failure. Modeling of electromigration in throughsiliconvia based 3d ic. Download free pdf interaction between electrostatic discharge and electromigration on copper interconnects for advanced cmos technologies 2005 ieee.
An introduction to electromigrationaware physical design. Physical, electrical, and reliability considerations for. All levels of system abstraction are covered, but the emphasis rests squarely on circuit design. Cmos complementary metal oxide semiconductor cots commercialofftheshelf dac digitaltoanalog converter dahc drain avalanche hot carrier dfr designforreliability dnl differential nonlinearity em electromigration eos electrical overstress etm effective temperature models. Electromigration what ic designers need to know industry. The authors are the first to analyze and propose a solution for. This book describes new and effective methodologies for modeling, analyzing and mitigating cellinternal signal electromigration in nanocmos, with significant circuit lifetime improvements and no impact on performance, area and power.
Introduction technology scaling has resulted in a monotonic increase in the current density, causing electromigration em in interconnects to be a major concern 1. The paper also addresses alternative noncmosdevices i. Schematic illustration of electromigration with resultant hillock and void formation. The temperature effect on electromigration reliability. The electron wind leadsto a net flux of metal atoms, creating. Wever correlation between the direction of the current flow and the material transport. Unlike previous electromigration reliability tools, item can estimate the interconnect temperature rise due to joule heating and heat conduction from the substrate using a newly developed lumped thermal model.
Unlike previous electromigration reliability tools, item can estimate the interconnect temperature rise due to joule heating and heat conduction from the substrate using a. Reliability of electronics at cryogenic temperatures an. Electromigration failures may result whenacurrent flows through an onchip wire over a long period of time, causinga physical migration of atoms in the wire, particularly near vias in copper interconnects14and in a statistical manner 15. Electromigration inside logic cells modeling, analyzing and. It is shown that activation energy in the cubcb architecture is quite low, and copper migration might preferentially occur at cubarrier andor cubcb interfaces. Jones silicon technology solutions sts, technology solutions organization, freescale semiconductor, 3501 ed bluestein blvd, md. May 26, 20 electromigration mechanisms are accelerated by current density as well as temperature. Electromigration, blech length, steady state, stress 1. Jun 15, 2020 leuven belgium, 15 june, 2020 this week, at the 2020 symposia on vlsi technology and circuits, imec, a worldleading research and innovation hub in nanoelectronics and digital technologies, presents a tungsten w buried power rail bpr integration scheme in a finfet cmos test vehicle, which does not adversely impact the cmos device characteristics. If the current density is high enough, the heat dissipated within the material will repeatedly break atoms from the structure and move them. In contrast, devices for applications of radio frequency cmos. Electromigration is the movement of atoms based on the flow of current through a material. In either approach, the electromigration computation requires knowledge of. Alternatively, it may be that electromigration in field failures is hard to recognize and even harder to prove.
Rauch, iii, phd, is currently a senior technical staff member at the ibm srdc in new york, where he specializes in hot carrier and nbti reliability of stateoftheart cmos devices. A resistance change methodology for the study of electromigration in alsi interconnects jose maiz, inigo segura. Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. This may be derived from an external source, such as leakage from a direct current power supply, but is also frequently caused by the electrical potential of pitting corrosion on reinforcing steel. Abstractelectromigration em has been considered to be the major reliability issue for current and future vlsi technologies. Download free pdf interaction between electrostatic discharge and electromigration on copper interconnects for advanced cmos technologies 2005 ieee international reliability physics symposium, 2005. Part 1 introduction fault models stuckline single and multiple bridging stuckopen test pattern generation combinational circuit test generation sequential circuit test generation ece 261 krish chakrabarty 3 outline testing logic veri. As electromigration problem and its relationship to current density. As em considerations become more critical, there is a need for circuit analysis and. Iyer, fellow, ieee abstract for the first time we describe a positive application of electromigration, as an electrically programmable fuse device efuse.
Electrically programmable fuse efuse using electromigration. Arzt, and nix, 1991 electromigration causes several different kinds of failure in narrow interconnect. In this paper, we present a new electromigration reliability diagnosis tool item for cmos vlsi circuits. The microhotplate can be manufactured by a cmos compatible microelectronics process, e. If an electric field is applied across the concrete, the negative ions will move towards the positive electrode.
The mechanism remains, but its failure modes and visible evidence have changed. The amg converts human based em modeling into an automated modeling and simulation process with the help of ansys parametric design language apdl program. Circuit pitfalls cmos vlsi designcmos vlsi design 4th ed. Electromigration aware physical design of integrated circuits. Consequently chemical mechanical polishing process was introduced for patterning cu lines. Accurate estimates of power dissipation are necessary for several reasons. University of arizona 1996 a dissertation submitted in partial satisfaction of the requirements for the degree of doctor of philosophy in mathematics in the graduate division of the university of california at berkeley committee in charge. Monolithic integration of electronics and subwavelength. Electromigration em refers to the unwanted movement of materials in a semiconductor. Cu has higher mass omore resistant to electromigration. Silicon wafer is the starting point of the cmos fabrication process a doped silicon layer is a patterned n or ptype section of the wafer surface.
Investigations for common twoand threedimensional interconnect structures are presented. For automating the neural model training process, trainingdriven adaptive sampling is applied to integrate data generation, data distributions determination, model structure adaptation. Pdf introduction to electromigrationaware physical design jens. Accelerated electromigration lifetest plots lognormal paper of al si2% alloys for different copper concentrations. The third group of reliability hazards, which is specific to the cmos highvoltage drivers, is related to current and voltage spiking at the highvoltage power supply pin, vpp, and outputs of the driver.
As the structure size in electronics such as integrated circuits ics. In most of these processes, aluminium, tungsten or copper is optionally used as metallization. Electromigration and its impact on physical design in. Fabrication and layout cmos vlsi design slide 39 cmos fabrication cmos transistors are fabricated on silicon wafer lithography process similar to printing press on each step, different materials are deposited or etched easiest to understand by viewing both. Electromigration ta nfo rdu ivesy 10 ee311 interconnect scaling araswat line resistance and capacitance r. Cmos ulsi to substitute al because of its lower resistivity and higher electromigration resistance. Layout construction for addressing electromigration publication number ep3036768b1 ep3036768b1 20170308. Electromigration reliability wearout mechanisms in advanced. Multisite onchip current sensor for electromigration. Fast and automated electromigration analysis for cmos rf.
This may be evidence that designers and reliability engineers have achieved near perfection. Metal interconnect in vlsi circuits is designed to withstand an average current density of aboutlmalm and a peak current density of approximatelylomalm 191. Electromigrationinduced failures in vlsi interconnects ieee xplore. Pdf design of highperformance microprocessor circuits. Electromigration and its impact on physical design in future.
Fast and automated electromigration analysis for cmos rf pa. Proceedings of the 18th international conference on vlsi design held jointly with 4th. A typical implementation is a laserfuse, where laser energy is used. With scaling of technology l increases, x ox, l s w and h decrease as a result r, c ox and c i increase arhw. Electromigration reduction in microhotplates cambridge. This report describes the work accomplished during the period jan.
Electromigration of cusncu micropads in 3d interconnect zhihong huang, ritwik chatterjee, patrick justison, richard hernandez, scott pozder, ankur jain, eddie acosta, donald a. Pdf interaction between electrostatic discharge and. Electromigration reliability wearout mechanisms in. Predicting electromigration mortality under temperature. Pdf this report summarizes work in reliability analysis in vlsi cmos circuits, particularly electromigration in metal lines, power busses and signal. Via yields, cu resistivity, defectivity, electromigration, stressmigration analytical. Device dimensions in 21stcentury complementary metal oxide semiconductor cmos technology are reaching well into the nanometer regime 1.
With continuous scaling of device dimensions, electromigration failures have been observed even in silicided contacts 1 and most effort has been focused on alleviating such failures. Introduction metallization failure electromigration general approach to electromigration reliability thermal considerations for electromigration closi. Cmos demo 2002 conformal doping in finfet 2011 multivt solution in finfet 2012 0. Fuse devices are useful in cmos chips for redundancy implementation in memory arrays, for trimming resistors, capacitors and other discrete components in analog circuits, for permanently holding information such as chipid etc. The thin oxide layer is subject to quantummechanical tunneling, giving rise to a gate leakage current that increases. Research and development into the causes led to several papers in the 1980s discussing causes and methods to lessen the influence of latchup. When a driver is loaded with a capacitor, c, the amplitude of the current spike is isp cv. Electromigration to reduce electromigration can add a small percentage of a heavier metal, like cu to al. Pdf electromigration in interconnect structures of. If the current density is high enough, the heat dissipated within the.
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