Improvement of the Long-Term Reliability of Interconnection by Controlling the Crystallinity of Grain Boundaries

2015 ◽  
Author(s):  
Takahiro Nakanishi ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Ion Beam ◽  
Diffusion Constant ◽  
Diffraction Method ◽  
Electron Back Scatter Diffraction ◽  
Test Method ◽  
Electroplated Copper

Electroplated copper thin films have started to be employed as the interconnection material in TSV structures of 3D semiconductor modules because of its low electric resistivity and high thermal conductivity. However, electrical and mechanical properties of electroplated copper thin-films have been found to vary drastically depending on their microtexture. In particular, the crystallographic quality (crystallinity) of grain boundaries in the electroplated copper thin-films plays an important role on the variations of these properties and the long-term reliability of the interconnections. This is because grain boundaries are the area where the atomic alignment of mateerials is disordered and thus, various defects such as vacancies, dislocations, impurities, and strain easily concentrate around them. This disorder of the atomic alignment causes the increase in the electrical resistivity, diffusion constant along the grain boundaries, and the brittleness of the material. Therefore, it is very important to evaluate the characteristics of a grain boundary quantitatively in order to control and assure the properties of the electroplated copper thin films. In this study, a novel tensile test method that can measure the strength of a grain boundary has been developed by using a focused ion beam system. In order to investigate the effect of the crystallinity of grain boundaries on their strength, an electron back-scatter diffraction method (EBSD) was employed for the quantitative characterization of grain boundaries. It was confirmed that the strength of grain boundaries with low crystallinity was much lower than that with high crystallinity.

Improvement of Thermal Conductivity of Electroplated Copper Thin-Film Interconnections by Controlling Their Micro Texture

2014 ◽  
Author(s):  
Pornvitoo Rittinon ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Grain Boundaries ◽  
Diffraction Method ◽  
Electron Back Scatter Diffraction ◽  
High Resistivity ◽  
Copper Thin Film ◽  
Electroplated Copper ◽  
The Relationship

Copper thin films are indispensable for the interconnections in the advanced electronic products, such as TSV (Trough Silicon Via), fine bumps, and thin-film interconnections in various devices and interposers. However, it has been reported that both electrical and mechanical properties of the films vary drastically comparing with those of conventional bulk copper. The main reason for the variation can be attributed to the fluctuation of the crystallinity of grain boundaries in the films. Porous or sparse grain boundaries show very high resistivity and brittle fracture characteristic in the films. Thus, the thermal conductivity of the electroplated copper thin films should be varied drastically depending on their micro texture based on the Wiedemann-Franz’s law. Since the copper interconnections are used not only for the electrical conduction but also for the thermal conduction, it is very important to quantitatively evaluate the crystallinity of the polycrystalline thin-film materials and clarify the relationship between the crystallinity and thermal properties of the films. The crystallinity of the interconnections were quantitatively evaluated using an electron back-scatter diffraction method. It was found that the porous grain boundaries which contain a significant amount of vacancies increase the local electrical resistance in the interconnections, and thus, cause the local high Joule heating. Such porous grain boundaries can be eliminated by control the crystallinity of the seed layer material on which the electroplated copper thin film is electroplated.

Improvement of the Long-Term Reliability of TSV Interconnections Used in Three-Dimensional Stacked Modules

2014 ◽  
Author(s):  
Hideo Miura ◽  
Ken Suzuki
Keyword(s):  
Grain Boundaries ◽  
Three Dimensional ◽  
Diffusion Constant ◽  
Diffraction Method ◽  
Electron Back Scatter Diffraction ◽  
View Point ◽  
Polycrystalline Thin Film ◽  
Strong Function

The long-term reliability of inerconnectons of three-dimensional integrated modules was investigated from the view point of crystallographic quality of the interconnection. The dgradation process of the interconnections was dominated mainly by the diffusion of copper atoms along grain boundaries in a polycrystalline thin-film and the diffusion constant was found to vary drastically depending on the crystallinity of the copper interconnections. The crystallinity of the interconnections changed seriously as a strong function of the mismatch in the lattice constant between copper and the seed layer material used for electroplating of the copper interconnections. The crystallinity of the electroplated interconnections was evaluated quantitatively by using an electron back-scatter diffraction method. Both the quality of grains and grain boundaries in the copper interconnections varied drastically as a function of electroplating conditions and their thermal hystory after the electroplating. The most important factors for the long-term reliability was the initial quality of the interconnection just after the electroplating.

Crystallinity Dependence of Grain and Grain Boundary Strength of a Bicrystal Structure of Copper

2020 ◽  
Author(s):  
Ken Suzuki ◽  
Yiqing Fan ◽  
Yifan Luo
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Defect Density ◽  
Volume Ratio ◽  
Md Simulations ◽  
Atomic Diffusion ◽  
Strength And Deformation ◽  
Electroplated Copper ◽  
Boundary Strength

Abstract Electroplated copper thin films often contain porous grain boundaries and the volume ratio of porous grain boundaries in the copper thin films is much larger than that in bulk copper. Thus, the lifetime of the interconnection components fabricated by electroplating is strongly dominated by the strength of grain boundaries because final fracture caused by the acceleration of atomic diffusion during electromigration (EM) occurs at grain boundaries in polycrystalline interconnections. It is important, therefore, to quantitatively evaluate the grain boundary strength of electroplated copper films for estimating the lifetime of the interconnection in order to assure the product reliability. In this study, relationship between the strength and crystallinity of electroplated copper thin films was investigated experimentally and theoretically. In order to investigate the relationship between the strength and grain boundary quality, molecular dynamics (MD) simulations were applied to analyze the deformation behavior of a bicrystal sample and its strength. The variation of the strength and deformation property were attributed to the higher defect density around grain boundaries.

Crystallinity-Induced Variation of the Yield Strength of Electroplated Copper Thin Films

2017 ◽  
Author(s):  
Yifan Luo ◽  
Kunio Tei ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Thin Films ◽  
Yield Strength ◽  
Tensile Test ◽  
Crystalline Silicon ◽  
Ion Beam ◽  
Side Surface ◽  
Test System ◽  
Electron Back Scatter Diffraction ◽  
Electroplated Copper ◽  
Focus Ion Beam

The quality of grains and grain boundaries of polycrystalline copper thin films was analyzed by using image quality (IQ) value obtained from the observed Kikuchi pattern by applying electron back-scatter diffraction (EBSD) analysis. It is considered that the IQ value strongly correlates with the order of atomic configuration in the observed area, in other words, density of various defects, and thus, the area with high IQ value was defined as the area with high crystallinity. The yield strength of a grain was measured by using micro tensile test system in a scanning electron microscope. A bicrystal structure which had two grains with different IQ values was cut from a copper thin film by using focus ion beam (FIB) and the sample was fixed to a single-crystalline silicon beam and a micro probe, respectively, by tungsten deposition. Finally it was thinned to 1μm and stretched to fracture at room temperature. In this micro tensile test, however, the tungsten deposition on the side surface of the test samples caused serious error on the measured strength. Therefore, in this study, the experimental method was improved by the development of an effective method for elimination the excess tungsten deposition. During the tensile test, a mass of plastic deformation and necking phenomenon were obviously observed. Ductile fracture always occurred in the grain with higher Schmidt factor. It was found that the yield strength of a copper grain decreased monotonically with the increase in the IQ value when the IQ value at the grain boundary was larger than 3500.

Microstructural Fractal Dimension of AISI 316L Steel

1994 ◽  
Vol 367 ◽  
Author(s):  
M. Hinojosa ◽  
R. Rodréguez ◽  
U. Ortiz
Keyword(s):  
Fractal Dimension ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Tensile Strain ◽  
Optical Microscope ◽  
Standard Test ◽  
Test Method ◽  
Aisi 316L ◽  
316L Steel ◽  
Deformation Processes

AbstractFractal dimension of the microstructure of AISI 316L steel (17 Cr, 12.7 Ni, 2.1 Mo, 1. 5 Mn, 0.01 C) with different degrees of strain were obtained from Richardson plots of grain boundary perimeter against magnification. Grain boundaries were revealed using conventional metallographic techniques and measurements were taken with the aid of an automatic image analizer (Quantimet 520) attached to an optical microscope. The magnifications used were 50, 100, 200, 400, and 1000X. The samples were obtained from a 4” diameter tubing, machined according to ASTM A370 standard test method and deformed to 5, 10, 15, and 20 % tensile strain. The results show that the fractal dimension of the grain boundaries changes as deformation is imparted to the material.These results suggest that fractal dimension may be used to describe microstructural evolution of metals during deformation processes.

Mechanical Properties of Electroplated Copper Thin Films

1999 ◽  
Vol 594 ◽  
Author(s):  
R. Spolenak ◽  
C. A. Volkert ◽  
K. Takahashi ◽  
S. Fiorillo ◽  
J. Miner ◽  
...  
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Grain Size ◽  
Film Thickness ◽  
Yield Stress ◽  
Laser Scanning ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Cu Films ◽  
Electroplated Copper

AbstractIt is well known that the mechanical properties of thin films depend critically on film thickness However, the contributions from film thickness and grain size are difficult to separate, because they typically scale with each other. In one study by Venkatraman and Bravman, Al films, which were thinned using anodic oxidation to reduce film thickness without changing grain size, showed a clear increase in yield stress with decreasing film thickness.We have performed a similar study on both electroplated and sputtered Cu films by using chemical-mechanical polishing (CMP) to reduce the film thickness without changing the grain size. Stress-temperature curves were measured for both the electroplated and sputtered Cu films with thicknesses between 0.1 and 1.8 microns using a laser scanning wafer curvature technique. The yield stress at room temperature was found to increase with decreasing film thickness for both sets of samples. The sputtered films, however, showed higher yield stresses in comparison to the electroplated films. Most of these differences can be attributed to the different microstructures of the films, which were determined by focused ion beam (FIB) microscopy and x-ray diffraction.

Microtexture Dependence of Mechanical and Electrical Properties of Gold Thin Films Used for Micro Bumps of 3D Stacking Structures

2020 ◽  
Author(s):  
Genta Nakauchi ◽  
Shota Akasaki ◽  
Hideo Miura
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Electrical Properties ◽  
Grain Boundaries ◽  
Indentation Test ◽  
Electron Back Scatter Diffraction ◽  
Effective Lifetime ◽  
Mechanical And Electrical Properties ◽  
Gold Thin Films ◽  
3D Stacking

Abstract The variation of their crystallinity, in other words, the order of atom arrangement of grain boundaries in electroplated gold thin films was investigated by changing their manufacturing conditions. Then, the effect of the crystallinity on both their mechanical and electrical properties was measured by using nano-indentation test and electromigration test. The crystallinity of the gold thin films was varied by changing the under-layer material used for electroplating. Also, the micro texture of gold thin films was evaluated by EBSD (Electron Back-Scatter Diffraction) and XRD (X-Ray Diffraction). It was clarified that the crystallinity of the electroplated gold thin films changed drastically depending on the crystallinity of the under-layer materials and electroplating conditions such as current density and temperature. This variation of the crystallinity should have caused wide variation of mechanical properties of the films. In addition, their mechanical properties such as Young’s modulus and hardness showed wide variation by about 3 times comparing with those of bulk gold. Similarly, the EM resistance of the electroplated gold bumps varied drastically depending on the ratio of porous grain boundaries and their crystallinity. Both the ratio and crystallinity also varied depending on the crystallinity of the under layer and electroplating conditions. The effective lifetime of the gold bumps was successfully predicted by considering both the crystallinity and residual stress of fine gold bumps. The lifetime varied more than 10 times as a strong function of the crystallinity of grain boundaries in the fine bumps. Therefore, it is very important to control the crystallinity of the under-layer for electroplating in order to control the distribution of the mechanical properties and reliability of the electroplated gold thin films.

Effect of Crystallographic Quality of Grain Boundaries on Both Mechanical and Electrical Properties of Electroplated Copper Thin Film Interconnections

2011 ◽  
Author(s):  
Naokazu Murata ◽  
Naoki Saito ◽  
Kinji Tamakawa ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Thin Film ◽  
Brittle Fracture ◽  
Grain Boundaries ◽  
Fracture Mode ◽  
Electron Back Scatter Diffraction ◽  
Fracture Rate ◽  
Copper Films ◽  
Average Grain Size ◽  
Electroplated Copper

Both mechanical and electronic properties of electroplated copper films used for interconnections were investigated experimentally considering the change of their micro texture caused by heat treatment. The fracture strain of the film annealed at 400°C increased from about 3% to 15% and their yield stress decreased from about 270 MPa to 90 MPa. In addition, it was found that two different fatigue fracture modes appeared in the film. One was a typical ductile fracture mode and the other was brittle one. When the brittle fracture occurred, a crack propagated along weak or porous grain boundaries which were formed during electroplating. The brittle fracture mode disappeared after the annealing at 300°C. These results clearly indicated that the mechanical properties of electroplated copper thin films vary drastically depending on their micro texture. The electrical reliability of the electroplated copper yjin film interconnections was also investigated. The interconnections used for electromigration tests were made using by a damascene process. An abrupt fracture mode due to local fusion appeared in the as-electroplated interconnections. Since the fracture rate increased almost linearly with the square of the applied current density, this fracture mode was dominated by local Joule heating. It seemed that the local current concentration occurred around the porous grain boundaries. The life of the interconnections was improved drastically after the annealing at 400°C. This was because of the increase of the average grain size and the improvement of the quality of grain boundaries in the annealed interconnections. However, the stress-induced migration occurred in the interconnections annealed at 400°C. This was because of the high tensile residual stress caused by the constraint of the densification of the films during annealing by the surrounding oxide film. Therefore, it is very important to control the crystallographic quality of electroplated copper films for improving the reliability of thin film interconnections. The quality of the grain boundaries can be evaluated by applying an EBSD (Electron Back Scatter Diffraction) analysis. New two experimentally determined parameters are proposed for evaluating the quality of grain boundaries quantitatively. It was confirmed that the crystallographic quality of grain boundaries can be evaluated quantitatively by using the two parameters, and it is possible to estimate both the strength and reliability of the interconnections.

scholarly journals Ion Beam Enhanced Grain Growth in Thin Films

1986 ◽  
Vol 74 ◽  
Author(s):  
Harry A. Atwater ◽  
Carl V. Tiiompson ◽  
Henry I. Smith
Keyword(s):  
Thin Films ◽  
Growth Rate ◽  
Grain Boundary ◽  
Grain Growth ◽  
Thermal Equilibrium ◽  
Ion Beam ◽  
Defect Concentration ◽  
Growth Enhancement ◽  
Frenkel Defect ◽  
Good Agreement

AbstractIon beam enhanced grain growth has been investigated in thin films of Ge. Grain boundary mobilities are greatly enhanced over their thermal equilibrium values and exhibit a very weak temperature dependence. We propose that defects which are generated by the ion beam at or near the grain boundary are responsible for the boundary mobility enhancement. Films of Ge deposited under different conditions, either unsupported or on thermally oxidized Si, exhibit similar normal grain growth enhancement when implanted with 50 keV Ge+. Beam-enhanced grain growth in Ge was also demonstrated using Xe+, Kr+, and Ar+ ions. The variation in growth enhancement with projectile ion mass is in good agreement with the enhanced Frenkel defect population calculated using a modified Kinchin-Pease formula and Monte Carlo simulation of ion transport in thin films. Calculations based on experiments suggest that there is approximately one atomic jump across the grain boundary per defect generated. Also, the grain growth rate for a given beam-generated defect concentration near the boundary is approximately equal to the expected growth rate for the same defect concentration if thermally generated.

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