The Behaviour of Au-Au Wire Bonds in Extreme Environments

2010 ◽  
Vol 2010 (HITEC) ◽  
pp. 000114-000121 ◽  
Author(s):  
D. Shepherd ◽  
P.S. Grant ◽  
C. Johnston ◽  
S. Riches
Keyword(s):  
Yield Strength ◽  
Focused Ion Beam ◽  
High Reliability ◽  
Ion Beam ◽  
Extreme Environments ◽  
Stable Solution ◽  
Thermal Ageing ◽  
Grain Structure ◽  
Microstructural Stability ◽  
Wire Bonds

Microelectronics are being required to show high reliability within aero-engines, oil-gas wells and other extreme applications where devices can experience over 250°C, 1000bar, corrosive environments and significant vibration. Currently operation may be only possible for a small number of hours, which necessitates expensive shut-down and replacement. Wire bond interconnects continue to be critical to overall reliability though previous studies have shown that traditional Au-Al bonds fail in such environments due to microstructural instability. Au-Au bonds offer a potentially stable solution that is increasingly desirable as microelectronics are required to endure ever harsher conditions. Au ball bonds on two representative substrates with Au surfaces and ceramic bases have been exposed to 250 and 300°C in N2 for up to 2000 hours. Substrate 1 was a high temperature co-fired ceramic (HTCC) with a Au coating above Ni-Co and W layers, and Substrate 2 was a Au thick film on alumina. Wire pull and ball shear tests for both sample types significantly exceeded industry specifications, though a decrease in yield strength was observed. Key samples were cross-sectioned and grain structure was revealed by ion channelling contrast within a focused ion beam (FIB) system. The yield strength decrease was attributed to the Hall-Petch effect through elimination of twin grains formed during bonding deformation. Electron probe microanalysis (EPMA) of underlying Ni showed little interdiffusion into the Au. Hence the mechanical robustness and microstructural stability of Au-Au wire bonds in extreme environments has been demonstrated and understanding of thermal ageing mechanisms has been improved.

A New Technique For Visualizing The Displacement Field Of Indentations: The Case Of A Soft Film On A Hard Substrate

1997 ◽  
Vol 505 ◽  
Author(s):  
Joost J. Vlassak ◽  
T. Y. Tsui ◽  
W. D. Nix
Keyword(s):  
Titanium Nitride ◽  
Displacement Field ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Grain Structure ◽  
New Technique ◽  
Hard Substrate ◽  
Film Material ◽  
Pile Up ◽  
A New Technique

ABSTRACTWe have developed a new technique for visualizing displacement fields of indentations in thin films. In this technique, the indented film consists of alternating layers of two different materials. One of the materials serves as a marker for visualizing the plastic flow induced by the indentation. Focused Ion Beam (FIB) milling is used to cross-section the indentation, revealing the deformed layers. This technique can be used to study how the presence of the substrate affects the plastic displacement field around the indentation. The technique is applied to a multilayered film of aluminum and titanium nitride on a silicon substrate. The titanium nitride layers are much thinner than the aluminum layers and serve the function of marker. Pile-up of the film material around the indenter and the effect of the hard substrate are easily revealed and a mechanism for pile-up is suggested. The technique also shows that the grain structure in the deformed zone around the indentation is altered profoundly.

Characterization of Plated Cu Thin Film Microstructures

1999 ◽  
Vol 564 ◽  
Author(s):  
L. M. Gignac ◽  
K. P. Rodbel ◽  
C. Cabral ◽  
P. C. Andricacos ◽  
P. M. Rice ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Grain Structure ◽  
Grain Structures ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Gaussian Fit ◽  
Cu Thin Film ◽  
Log Normal ◽  
Electron Imaging

AbstractElectroplated Cu was found to have a fine as-plated microstructure, 0.05 ± 0.03 μm, with multiple grains through the film thickness and evidence of twins and dislocations within grains. Over time at room temperature, the grains grew to greater than 1 μm in size. Studied as a function of annealing temperature, the recrystallized grains were shown to be 1.6 ± 1.0 μm in size, columnar and highly twinned. The grain growth was directly related to the time dependent decrease in sheet resistance. The initial grain structure was characterized using scanning transmission electron microscopy (STEM) from a cross-section sample prepared by a novel focused ion beam (FIB) and lift-out technique. The recrystallized grain structures were imaged using FIB secondary electron imaging. From these micrographs, the grain boundary structures were traced, and an image analysis program was used to measure the grain areas. A Gaussian fit of the log-normal distribution of grain areas was used to calculate the mean area and standard deviation. These values were converted to grain size diameters by assuming a circular grain geometry.

The Challenges of FIB Chip Repair and Debug Assistance in the 0.25μm Copper Interconnect Millennium

1998 ◽  
Author(s):  
S.B. Herschbein ◽  
L.S. Fischer ◽  
T.L. Kane ◽  
M.P. Tenney ◽  
A.D. Shore
Keyword(s):  
High Performance ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Grain Structure ◽  
Long Term Storage ◽  
Wagon Wheel ◽  
Sram Cell ◽  
Oxide Deposition ◽  
Reliable Isolation

Abstract Copper will probably replace aluminum alloys as the interconnect metallurgy of choice for high performance semiconductor devices. This transition will challenge the suitability of established practices in focused ion beam (FIB) chip repair. A fundamental rethink in methodology, techniques, and process gases will be required to deal with the new metal films. This paper discusses the results of recent experiments in the areas of FIB exposure, cuts and connections to buried copper lines. While copper tends to mill faster than aluminum, etch rate variations due to grain structure tend to make reliable isolation cuts more difficult. The films also have been shown to suffer regrowth and surface reactions during long term storage following FIB exposure. Attempts at halogen gas assisted etch (GAE) mills result in undesirable removal characteristics, and in the case of bromine, the spontaneous destruction of all exposed copper in the immediate area. Resistance measurements and reliability of deposited tungsten connections to copper lines are also presented. In addition, the latest techniques developed for aluminum wiring isolation and device characterization are shown. These include 'cleanup' methods for achieving good circuit isolation without the extensive use of local oxide deposition, and the latest multilevel version of the FIB ‘wagon wheel’ for SRAM cell characterization. Also included is preliminary data from a custom built FIB chamber four manipulator prober module.

Analysis of Geometrical and Microstructural Effects on Void Formation in Metallization: Observation and Modelling

1996 ◽  
Vol 428 ◽  
Author(s):  
W. C. Shih ◽  
A. Ghiti ◽  
K. S. Low ◽  
A. L. Greer ◽  
A. G. O'Neill ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Void Formation ◽  
Grain Structure ◽  
Flux Divergence ◽  
Damage Development ◽  
Temperature Variations ◽  
Atomic Flux ◽  
Grain Structures ◽  
Microstructural Effects

AbstractThis paper reports the analysis of geometrical and microstructural effects on void formation in interconnects. Ion-beam machining is used to define segments for study at the cathode end of test lines. Scanning electron microscopy is used to observe damage development, focused ion beam microscopy to observe the corresponding grain structure. Finite-element calculations of self-consistent current density and temperature distributions in the conductor are used to predict damage locations both for a continuum material and for simulated grain structures. Cross-section changes in the line give temperature variations leading to divergences in atomic flux. Regions of high flux divergence are favoured for electromigration damage, but the precise sites of damage are determined by the grain structure, as shown both in the experiment and in the modelling.

Grain growth study of Al(Cu) lines by focused ion beam microscopy and Transmission Electron Microscopy

1995 ◽  
Vol 53 ◽  
pp. 296-297
Author(s):  
M.H. Sohn ◽  
D.A. Smith ◽  
K.P. Rodbell ◽  
Roy Izai
Keyword(s):  
Integrated Circuits ◽  
Grain Boundary ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Pure Aluminum ◽  
Point Of View ◽  
Grain Structure ◽  
Critical Ratio ◽  
Boundary Properties ◽  
Bamboo Structure

Interconnects for integrated circuits now have widths which are of the same order as the grain size. Consequently, their reliability is sensitive to the specific grain boundary properties and configurations rather than being averaged over many grains as in earlier technology when the line width was much greater than the grain diameter. From the point of view of electromigration resistance a bamboo grain structure is desirable. However, the conditions for forming a bamboo structure are not established. Walton et al. developed a model which predicts that the grain structure of aluminum lines becomes a bamboo structure, which is stagnant, upon annealing after particular time at specific temperature when the width to height ratio of the line is lower than a critical ratio (2.1-3.0). The precise value of the critical ratio depends on the ratio of the surface and grain boundary energies. Based on the modeling, we expect that the grain structure of pure aluminum stagnates after annealing at 500 °C for 2.3 hrs.

Enhancing Point Defect Isolation by Using Ionizing Radiation

2019 ◽  
Author(s):  
Douglas J. Martin ◽  
Matthew J. Gadlage ◽  
Wai-Yat Leung ◽  
Jeffrey L. Titus
Keyword(s):  
Ionizing Radiation ◽  
Integrated Circuit ◽  
Focused Ion Beam ◽  
High Reliability ◽  
Ion Beam ◽  
Photon Emission ◽  
Fault Isolation ◽  
Oxide Semiconductor ◽  
Carrier Injection ◽  
Failure Site

Abstract An application-specific integrated circuit (ASIC) for a high reliability application is found to have a missing sidewall spacer in a single transistor. Manufacturer burn-in and standard component electrical tests do not capture this defect. The defect manifests after exposure to ionizing radiation. Photon emission microscopy (PEM), laser voltage imaging (LVI), and laserassisted device alteration (LADA) are used to isolate the failure site. At the failure site a focused ion beam (FIB) cross section indicates that a doubly doped drain (DDD) (N+) is likely present where a lightly doped drain (LDD) is designated. This defect leads to a failure mode that is consistent with hot-carrier injection in complementary metal-oxide semiconductor (CMOS) transistors. This paper presents the testability from a fault isolation aspect, shmoo plot characterization, and backside optical techniques to identify its spatial location. A discussion of the results includes why ionizing radiation allowed the defect’s capture and potential implications of using ionizing radiation as a viable failure analysis technique.

scholarly journals Microtexture and Strain in Electroplated Copper Interconnects

2000 ◽  
Vol 612 ◽  
Author(s):  
R. Spolenak ◽  
D. L. Barr ◽  
M. E. Gross ◽  
K. Evans-Lutterodt ◽  
W. L. Brown ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Local Strain ◽  
Spot Size ◽  
Electron Back Scatter Diffraction ◽  
Grain Structure ◽  
X Rays ◽  
Area Detector ◽  
Submicron Scale ◽  
Electroplated Copper

AbstractThe microstructure of narrow metal conductors in the electrical interconnections on IC chips has often been identified as of major importance in the reliability of these devices. The stresses and stress gradients that develop in the conductors as a result of thermal expansion differences in the materials and of electromigration at high current densities are believed to be strongly dependent on the details of the grain structure. The present work discusses new techniques based on microbeam x-ray diffraction (MBXRD) that have enabled measurement not only of the microstructure of totally encapsulated conductors but also of the local stresses in them on a micron and submicron scale. White x-rays from the Advanced Light Source were focused to a micron spot size by Kirkpatrick-Baez mirrors. The sample was stepped under the micro-beam and Laue images obtained at each sample location using a CCD area detector. Microstructure and local strain were deduced from these images. Cu lines with widths ranging from 0.8 [.proportional]m to 5 [.proportional]m and thickness of 1 [.proportional]m were investigated. Comparisons are made between the capabilities of MBXRD and the well established techniques of broad beam XRD, electron back scatter diffraction (EBSD) and focused ion beam imagining (FIB).

scholarly journals The Effect of a Taper Angle on Micro-Compression Testing of Mo-B-C Coatings

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3054
Author(s):  
Lukáš Zábranský ◽  
Katarína Bernátová ◽  
Jiří Dluhoš ◽  
Rostislav Váňa ◽  
Pavel Souček ◽  
...  
Keyword(s):  
Yield Strength ◽  
Young’S Modulus ◽  
Focused Ion Beam ◽  
Young's Modulus ◽  
Ion Beam ◽  
Empirical Models ◽  
Taper Angle ◽  
Correction Model ◽  
Micro Pillars ◽  
Beam Technique

This research was devoted to studying the influence of the taper angle on the micro-compression of micro-pillars fabricated from near-amorphous and nanocrystalline Mo-B-C coatings. A series of micro-pillars with a taper angle between 4–14° was fabricated by focused ion beam technique. The deformation mechanism was found to be dependent on the taper and, also, on the crystallinity of the coating. In order to obtain correct values of yield strength and Young’s modulus, three empirical models of stress correction were experimentally tested, and the results were compared with nanoindentation measurements. It was shown that the average stress correction model provided comparable results with nanoindentation for the yield strength for taper angles up to ~10°. On the other hand, the average radius or area model gave the most precise results for Young’s modulus if the taper angle was <10°.

Characterization of Plated Cu Thin Film Microstructures

1999 ◽  
Vol 562 ◽  
Author(s):  
L. M. Gignac ◽  
K. P. Rodbell ◽  
C. Cabral ◽  
P. C. Andricacos ◽  
P. M. Rice ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Grain Structure ◽  
Grain Structures ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Gaussian Fit ◽  
Cu Thin Film ◽  
Log Normal ◽  
Electron Imaging

ABSTRACTElectroplated Cu was found to have a fine as-plated microstructure, 0.05 ±0.03 μm, with multiple grains through the film thickness and evidence of twins and dislocations within grains. Over time at room temperature, the grains grew to greater than 1 μm in size. Studied as a function of annealing temperature, the recrystallized grains were shown to be 1.6 ± 1.0 μm in size, columnar and highly twinned. The grain growth was directly related to the time dependent decrease in sheet resistance. The initial grain structure was characterized using scanning transmission electron microscopy (STEM) from a cross-section sample prepared by a novel focused ion beam (FIB) and lift-out technique. The recrystallized grain structures were imaged using FIB secondary electron imaging. From these micrographs, the grain boundary structures were traced, and an image analysis program was used to measure the grain areas. A Gaussian fit of the log-normal distribution of grain areas was used to calculate the mean area and standard deviation. These values were converted to grain size diameters by assuming a circular grain geometry.

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