Microstructure and Reliability of Sputter Deposited Cr-Crcu-Cu thin Films for Flip-Chip Applications

1996 ◽  
Vol 445 ◽  
Author(s):  
Na Zhang ◽  
Mark Mcnicholas ◽  
Neil Colvin
Keyword(s):  
Cross Sections ◽  
Thermal Cycle ◽  
Flip Chip ◽  
Grain Structure ◽  
Transmission Electron ◽  
Alloy Solder ◽  
Solder Balls ◽  
Columnar Grain ◽  
Sputter Deposited ◽  
Bond Pads

AbstractThe Cr‐CrCu‐Cu metal scheme, as a terminal multistructure metallization for flip chip applications, has been investigated utilizing PVD sputter deposition varying the conditions of deposition power and temperature, and film thickness. A modified Controlled Collapse Chip Connection (C4) process was utilized in order to evaluate the aforementioned deposition of the Cr‐CrCu‐Cu multilayers and the effect of film microstructure on the parameters of shear strength and thermal cycle reliability. Thermal cycle reliability results proved to be a function of both the CrCu alloy and the Cu overlayer thickness. Transmission electron microscopy (TEM) cross‐sections of the Cr‐CrCu‐Cu multilayers suggests that the columnar grain structure of the CrCu layer may provide a sacrificial thermal diffusion barrier between the PbSn alloy solder balls and the Al bond pads during the thermal‐cycle tests.

Image processing to delineate defect structures in HREM images of vapor-deposited thin films

1989 ◽  
Vol 47 ◽  
pp. 128-129
Author(s):  
R.M. Fisher ◽  
J.Z. Duan ◽  
Crispin J. Hetherington ◽  
Norman Fowler
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Cross Sections ◽  
Failure Modes ◽  
Grain Structure ◽  
Intrinsic Stress ◽  
Plan View ◽  
Transmission Electron ◽  
Columnar Grain ◽  
Chromium Films

The resistance of deposited thin films to cracking or delamination from substrates during production or service, crucial to the long term reliability of IC devices, is under study as part of a broad program on interfacial bonding and adhesion. Chromium films, of particular interest because of their widespread use in microelectronics, are especially prone to mechanical failure due to the high residual stresses that are generally present and their low fracture toughness. Transmission and scanning electron microscopy are being used to define the columnar grain structure and failure modes and x-ray diffraction is being employed to determine the nature of through-thickness stress gradients that occur in such films.The intrinsic stress, as distinguished from the extrinsic stress caused by differential contraction between film and substrate during cooling from the deposition temperature, results from the presence of vacancies and diffuse “voids” trapped between the columns during deposition. Transmission electron microscopy of plan-view and cross-sections is being used in efforts to observe and define the structure of the inter-columnar regions.

High quality a-Si/Nb and a-SiN/NbN artificial multilayers for Josephson applications

1994 ◽  
Vol 9 (7) ◽  
pp. 1678-1682 ◽  
Author(s):  
J. Chen ◽  
E.D. Rippert ◽  
S.N. Song ◽  
M.P. Ulmer ◽  
J.B. Ketterson
Keyword(s):  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Layer Growth ◽  
Interface Condition ◽  
Grain Structure ◽  
Transmission Electron Microscopy Study ◽  
High Quality ◽  
Columnar Growth ◽  
Transmission Electron ◽  
Columnar Grain

A high resolution transmission electron microscopy study of multilayer films prepared by magnetron sputtering shows that the morphology of the growing interface in a-Si/Nb and a-SiN/NbN multilayers is remarkably uniform and smooth; this is in contrast to the polycrystalline AlN/NbN multilayers grown under similar conditions, which exhibit columnar grain structure with rough interfaces. For proper sputtering parameters, the amorphous layers seem to periodically restore a relatively smooth initial interface condition for the successive Nb (or NbN) layer growth, consequently interrupting the tendency toward increased roughness due to mechanisms such as columnar growth. Artificial multilayers having very flat interfaces could stimulate applications based on multilayer Josephson junctions.

Nucleation and Growth of the First Phase in Sputter-Deposited Nb/Al Multilayer Thin Films

1995 ◽  
Vol 398 ◽  
Author(s):  
K. Barmak ◽  
S. Vivekanand ◽  
F. Ma ◽  
C. Michaelsen
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Nucleation And Growth ◽  
Grain Structure ◽  
Multilayer Thin Films ◽  
Product Phase ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Sputter Deposited

ABSTRACTThe formation of the first phase in the reaction of sputter-deposited Nb/Al multilayer thin films has been studied by power-compensated and heat-flux differential scanning calorimetry, x-ray diffraction and transmission electron microscopy. The modulation periods of the films are in the range of 10-500 nm. Both types of calorimetrie measurements, performed at a constant heating rate, show the presence of two peaks (A and B) for the formation of the single product phase, NbAl3. Isothermal calorimetrie scans show that peak A is associated with a nucleation and growth type transformation. The formation of NbAl3 is thus interpreted as a two-stage process of nucleation and lateral growth to coalescence (peak A) followed by normal growth until the consumption of one or both reactants (peak B). Transmission electron microscopy investigations of samples annealed into the first stage of NbAl3 formation show the presence of this phase at the Nb/Al interface and its preferential growth along the grain boundaries of the Al layer. The latter highlights the role of reactant phase grain structure in product phase formation.

Failure Analysis of Flip-Chip Bumps After Thermal Stressing

2000 ◽  
Author(s):  
Tejpal K. Hooghan ◽  
Kultaransingh Hooghan ◽  
Sho Nakahara ◽  
Robert K. Wolf ◽  
Robert W. Privette ◽  
...  
Keyword(s):  
Cross Sections ◽  
Flip Chip ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Diagnostic Technique ◽  
Acoustic Microscopy ◽  
Under Bump Metallization ◽  
Thermal Tests ◽  
Transmission Electron ◽  
Electrical Bias

Abstract This paper describes a new diagnostic technique for analyzing microstructural changes occurring to flip chip joints after accelerated thermal tests. Flip chip reliability was assessed at high temperatures, with and without the application of electrical bias. A combination of standard metallurgical polishing techniques and the use of a focused ion beam (FIB) lift out technique was employed to make site-specific samples for transmission electron microscopy (TEM) cross-sections. We studied evaporated 95Pb/5Sn bumps, on sputtered Cr/CrCu/Cu/Au as the under bump metallization (UBM). Thermally stressed samples were tested for electrical continuity and evaluated using 50 MHz C-mode scanning acoustic microscopy (C-SAM). Failed samples were crosssectioned and large voids at the UBM were observed optically. TEM specimens taken from the predefined UBM region of degraded flip chip devices provided critical microstructural information, which led to a better understanding of a cause of degradation occurring in the flip chip joints.

Mechanisms of Initialization of Doped Sb-Te Phase-Change Media

2003 ◽  
Vol 803 ◽  
Author(s):  
Samantha J. Towlson ◽  
Clifford A. Elwell ◽  
Clare E. Davies ◽  
A. Lindsay Greer
Keyword(s):  
High Strain ◽  
Optical Recording ◽  
Grain Structure ◽  
Beam Power ◽  
Low Velocity ◽  
X Ray ◽  
Inhomogeneous Strain ◽  
Peak Broadening ◽  
Transmission Electron ◽  
Columnar Grain

ABSTRACTLaser initialization of the chalcogenide optical-recording medium Ag-In-Sb-Te is investigated using transmission electron microscopy of the resulting microstructure. Initialization beam power and velocity are varied. The average inhomogeneous strain of the chalcogenide is estimated from X-ray peak broadening. At high power and low velocity a clearly defined columnar grain structure with low strain is produced, typical of directional solidification. At low power and high velocity the initialized structure has a high density of defects and high strain; this is attributed to crystallization from the amorphous rather than the liquid state. The beam power and linear velocity of laser initialization may therefore be used to control the microstructure.

Effect of Magnetic CoZrNb Seed Layers on Pd/Co Multilayers

1995 ◽  
Vol 382 ◽  
Author(s):  
Jonathan C. Morris ◽  
Wenhong Liu ◽  
Bruce M. Lairson
Keyword(s):  
Multilayer Film ◽  
Hysteresis Loops ◽  
Grain Structure ◽  
Recording Media ◽  
Magnetic Recording Media ◽  
Cross Sectional ◽  
Rocking Curve ◽  
Transmission Electron ◽  
Columnar Grain ◽  
Seed Layers

ABSTRACTPd/Co multilayers are candidates as perpendicular magnetic recording media. A softmagnetic underlayer can both improve crystallographic orientation and reduce the magnetostatic energy of recorded domains. Pd/Co multilayers have been deposited onto silicon nitride by DC magnetron sputtering with and without CoZrNb (CZN) seed layers. Cross-sectional transmission electron microscopy shows that the CZN layer imposes a columnar grain structure on the multilayer film through epitaxy. Seeded multilayers have columnar 200Å grains that begin at the CZN interface and extend through the film thickness. In contrast, the grains in unseeded multilayers are not columnar. X-ray rocking curves on the (111) Pd/Co peak show that the CZN seed layer improves the (111) crystallographic texture of the multilayer film. We observe a correspondence between FWHM rocking curve widths in the CZN and the subsequently deposited multilayer. The CZN seeding produces changes in perpendicular hysteresis loops, which are attributed to an exchange interaction and a change in the multilayer amicrostructure due to seeding.

Diffusional Hillock Formation in Al Thin Films Controlled by Creep

1999 ◽  
Vol 594 ◽  
Author(s):  
Deok-kee Kim ◽  
William D. Nix ◽  
Eduard Arzt ◽  
Michael D. Deal ◽  
James D. Plummer
Keyword(s):  
Power Law ◽  
Original Film ◽  
Stress Measurement ◽  
Grain Structure ◽  
Surrounding Area ◽  
Hillock Formation ◽  
Columnar Grain ◽  
Sputter Deposited ◽  
Power Law Creep ◽  
Microstructural Studies

AbstractThermal hillocks in sputter-deposited Al films have been studied as a part of a broad study of stress-induced diffusional processes in Al. Trace amounts of the impurities Ti, W, and O were incorporated into the films during deposition, causing them to be much stronger than most sputter deposited Al films. Stress measurement during thermal cycling, using the wafer curvature method, showed that these Al films are very strong; this finding was corroborated by hardness measurements. Microstructural studies using TEM and FIB showed that the hillocks start to form at the Al/SiO2 interface and grow under the original Al film, with its columnar grain structure. In some cases, the film fails as hillocks grow completely through the original film. The Al film on top of the hillocks appears to inhibit hillock growth by creating a back pressure associated with power law creep of the film. We modeled this form of hillock formation by modifying the boundary conditions in Chaudhari's hillock model [1]. Our model describes hillock formation by diffusion of Al atoms from the surrounding area into isolated hillocks, assuming that the original Al film on top of hillocks deforms following power law creep. Our model can be applied to many different situations by using different creep laws for the top Al film.

scholarly journals In Situ Study of Dislocation Behavior in Columnar Al Thin Film on Si Substrate During Thermal Cycling

1999 ◽  
Vol 594 ◽  
Author(s):  
Charles W. Allen ◽  
Herbert Schroeder ◽  
Jon M. Hiller
Keyword(s):  
Thin Film ◽  
Thermal Cycling ◽  
Grain Structure ◽  
Dislocation Model ◽  
Si Substrate ◽  
Transmission Electron ◽  
Dislocation Behavior ◽  
Columnar Grain ◽  
Al Thin Film

AbstractIn situ transmission electron microscopy (150 kV) has been employed to study the evolution of dislocation microstructures during relatively rapid thermal cycling of a 200 nm Al thin film on Si substrate. After a few thermal cycles between 150 and 500°C, nearly stable Al columnar grain structure is established with average grain less than a μm. On rapid cooling (3–30+ °C/s) from 500°C, dislocations first appear at a nominal temperature of 360–380°C, quickly multiplying and forming planar glide plane arrays on further cooling. From a large number of such experiments we have attempted to deduce the dislocation evolution during thermal cycling in these polycrystalline Al films and to account qualitatively for the results on a simple dislocation model.

Transmission Electron Microscopy of Mocvd Titanium Nitride Films

1994 ◽  
Vol 337 ◽  
Author(s):  
Toshio Itoh ◽  
Toyohiko J. Konno ◽  
Robert Sinclair ◽  
Ivo J.M.M. Raaijmakers ◽  
Bruce E. Roberts
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Layer Structure ◽  
The Other ◽  
Grain Structure ◽  
Tin Films ◽  
Si Substrates ◽  
Deposition Parameters ◽  
Transmission Electron ◽  
Columnar Grain

ABSTRACTThe effect of substrate temperature and process pressure on microstructure of MOCVD-TiN films deposited on oxidized Si substrates are studied by transmission electron microscopy (TEM). It is found that microstructure of MOCVD-TiN films distinctly changes with these deposition parameters and that the resistivity of the films is uniquely related to the microstructure. Films with the lowest resistivity (< 500 μohm-cm) show a uniform semi-columnar grain structure. Films with the highest resistivity (> 10,000 μohm-cm) show a uniform equi-axed micrograin structure. The other films exhibit a bi-layer structure: one layer of semi-columnar grains and the other of equiaxed micrograins. The thickness ratio of these layers changes with the deposition conditions and the resistivity is a unique function of the thickness of the semi-columnar grain layer.

Under Bump Metallization Development For High Sn Solders

1997 ◽  
Vol 505 ◽  
Author(s):  
T. M. Korhonen ◽  
S. J. Hong ◽  
P. Su ◽  
C. Zhou ◽  
M. A. Korhonen ◽  
...  
Keyword(s):  
Flip Chip ◽  
Silicon Wafers ◽  
Under Bump Metallization ◽  
Shear Tests ◽  
Adhesion Layer ◽  
Solder Balls ◽  
Sputter Deposited ◽  
Pure Cu ◽  
Solder Interface ◽  
Intermetallic Layers

ABSTRACTSeveral under bump metallisation (UBM) schemes using Ni or CuNi alloys as the solderable layer were investigated. Cr or Ti was used as the adhesion layer. The UBM pads of different compositions were sputter deposited on silicon wafers and patterned using standard photolithographic processes. Eutectic Sn-Pb solder balls were reflowed on top of the pads. The resulting interfacial microstructures were examined by SEMIEDX analysis of cross-sectioned samples. The integrity of the UBMIsolder interface was characterized by micromechanical shear testing of flip chip test samples. Growth of intermetallic layers was found to be significantly slower in Ni and CuNi schemes compared to pure Cu. The joints on Ni and CuNi had also a better adhesion at the UBM/solder interface, and in the shear tests the fracture occurred through the solder

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