Analysis of Al-over-Cu Bond Pad Hillock and Pit Hole Defects

2005 ◽  
Author(s):  
Daniel Cavasin ◽  
Abdullah Yassine
Keyword(s):  
Focused Ion Beam ◽  
Galvanic Corrosion ◽  
Process Analysis ◽  
Ion Beam ◽  
Metal Corrosion ◽  
Process Characterization ◽  
Nucleation Sites ◽  
Hole Defects ◽  
Bond Pads ◽  
Sawing Process

Abstract Bond pad metal corrosion was observed during assembly process characterization of a 0.13um Cu microprocessor device. The bond pad consisted of 12kÅ of Al-0.5%Cu atop 9kÅ of Cu, separated by a thin Ta diffusion barrier. The corrosion was first noted after the wafer dicing process. Analysis of the pad surface revealed pitting-type corrosion, consistent with published reports of classic galvanic cell reactions between Al2Cu (theta phase) particles and the surrounding Al pad metal. Analysis of the bond pads on samelot wafers which had not been diced showed higher-thanexpected incidence of hillock and pit hole defects on the Al surface. Statistically designed experiments were formulated to investigate the possibility that the observed pre-saw pad metal defects act as nucleation sites for galvanic corrosion during the sawing process. Analyses of the experimental samples were conducted using optical and scanning electron microscopy, along with focused ion beam deprocessing and energy dispersive X-ray. This paper explores the relationship between the presence of these pre-existing defects and the propensity for the bond pads to corrode during the dicing process, and reviews the conditions under which pit hole defects are formed during the final stages of the Cu-metallized wafer fabrication process. Indications are that strict control of wafer fab backend processes can reduce or eliminate the incidence of such defects, resulting in elimination of bond pad corrosion in the wafer dicing process.

BiCMOS Die Sort Yield Improvement from Isolation of a Localized Defect Mechanism and Precision TEM Cross Section

1997 ◽  
Author(s):  
J. Douglass ◽  
T. D. Myers ◽  
F. Tsai ◽  
R. Ketcheson ◽  
J. Errett
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Focused Ion Beam ◽  
Yield Loss ◽  
Process Analysis ◽  
Ion Beam ◽  
Yield Improvement ◽  
Transmission Electron ◽  
Defect Mechanism ◽  
Water Residue

Abstract This paper describes how the authors used a combination of focused ion beam (FIB) microprobing, transmission electron microscopy (TEM), and data and process analysis to determine that localized water residue was causing a 6% yield loss at die sort.

Failure Analysis and Elimination of Galvanic Corrosion on Bondpads During Wafer Sawing

2000 ◽  
Author(s):  
Y. N. Hua ◽  
E. C. Low ◽  
L. H. An ◽  
Shailesh Redkar
Keyword(s):  
Failure Analysis ◽  
Feed Rate ◽  
Galvanic Corrosion ◽  
Experimental Results ◽  
Metal Corrosion ◽  
Wafer Fabrication ◽  
Al Alloy ◽  
Assembly Process ◽  
Water Problem ◽  
Sawing Process

Abstract In our previous paper [1], discolored bondpads due to galvanic corrosion were studied. The results showed that the galvanic corrosion occurred in 0.8 ìm wafer fabrication (fab) process with cold Al alloy (Al-Si, 0.8 wt%-Cu, 0.5 wt%) metallization. Galvanic corrosion is also known as a two-metal corrosion and it could be due to either wafer fab process or assembly process. Our initial suspicion was that it was due to a DI water problem during wafer sawing at assembly process. After that, we did further failure analysis and investigation work on galvanic corrosion of bondpads and further found that galvanic corrosion might be due to longer rinsing time of DI water during wafer sawing. The rinsing time of DI water is related to the cutting time of wafer sawing. Therefore, some experiments of wafer sawing process were done by using different sizes of wafer (1/8 of wafer, a quadrant of wafer and whole of wafer) and different sawing speed (feed-rate). The results showed that if the cutting time was longer than 25 minutes, galvanic corrosion occurred on bondpads. However, if the cutting time was shorter than 25 minutes, galvanic corrosion was eliminated. Based on the experimental results, it is concluded that in order to prevent galvanic corrosion of bondpads, it is necessary to select higher feed-rate during wafer sawing process at assembly houses. In this paper, we will report the details of failure analysis and simulation experimental results, including the solution to eliminate galvanic corrosion of bondpads during wafer sawing at assembly houses.

Multiple-Post In-Situ Lift-Out Grids Preparation Using a Dicing Saw

2011 ◽  
Author(s):  
Jian-Shing Luo ◽  
Hsiu-Ting Lee ◽  
San-Lin Liew ◽  
Ching-Shan Sung ◽  
Yi-Jing Wu
Keyword(s):  
Sample Preparation ◽  
Focused Ion Beam ◽  
Flat Surface ◽  
Ion Beam ◽  
Ex Situ ◽  
Real Case ◽  
Case Application ◽  
Bond Pads ◽  
Preparation Techniques

Abstract The use of in-situ lift-out combined with focused ion beam milling has become a favorable choice as it offers several indispensable advantages compared to the conventional mechanical and ex-situ lift-out sample preparation techniques. This paper discusses the procedures of the multiple-post in-situ lift-out grids preparation using a dicing saw. In addition, a real case is described to show that the multiple-post in-situ lift-out grids have been successfully applied to failure analysis. The multiple-post in-situ lift-out grids provide more positions and flatter surfaces for TEM sample mounting. The flat surface greatly increases the mounting efficiency and success rate. For the real case application, a thick Al fluoride oxide layer and Al corrosion were found above the Al bond pads, which had NOSP problem, and their neighbor area, respectively.

Influence of Alkaline Cleaning on Reliability of Stacked Copper Micro-Via

2020 ◽  
Author(s):  
Yeonseop Yu ◽  
Job Ha ◽  
HyoungRok Lee ◽  
Joohyung Lee ◽  
Kang-Young Cho ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Galvanic Corrosion ◽  
Ion Beam ◽  
Energy Dispersive Spectrometer ◽  
Organic Contamination ◽  
Galvanic Couple ◽  
Transmission Electron ◽  
Cleaning Methods ◽  
Alkaline Cleaning ◽  
Structural Imperfections

Abstract Fan Out - Panel Level Packaging (FO-PLP) has redistribution layers (RDLs) which connect IC to a substrate. And each layer in the RDLs is connected through copper micro-vias. Viarelated defects including via separation are very critical because they can escape from electrical test and be found in the field. So many cleaning methods have been developed to keep the target pad surface free of oxides or organic contamination before forming vias. In this paper, we present a via separation case caused by alkaline cleaning introduced before seed metal deposition for electroplating of copper. We investigated the cause by analyzing the microstructure and chemical composition using a focused ion beam (FIB) and a transmission electron microscope (TEM) equipped with an energy dispersive spectrometer (EDS). Via separation, interestingly occurred at the interface between the seed Ti and the seed Cu not the interface between the seed Ti and the target pad..Cu surface which is known to be weak. We suggest a mechanism that structural imperfections at the outer rim of via bottom and galvanic couple of titanium and copper are involved in the separation of vias. Since two dissimilar metals of Ti and Cu are in direct contact, galvanic corrosion can occur in the presence of alkaline solution and discontinuities in the seed Ti layer. We found that galvanic corrosion in the studied system can be further complicated by the existence of copper oxide and titanium oxide as well as Cu and Ti.

A 3D FIB Investigation of Dynamic Recrystallization in a Cu-Sn Bronze

2012 ◽  
Vol 715-716 ◽  
pp. 498-501 ◽  
Author(s):  
Ali Gholinia ◽  
Ian Brough ◽  
John F. Humphreys ◽  
Pete S. Bate
Keyword(s):  
Dynamic Recrystallization ◽  
Focused Ion Beam ◽  
Electron Backscatter Diffraction ◽  
Ion Beam ◽  
Bronze Alloy ◽  
Ebsd Data ◽  
Nucleation Sites ◽  
Electron Backscatter ◽  
Backscatter Diffraction ◽  
Relationship Of

A combination of electron backscatter diffraction (EBSD) and focused ion beam (FIB) techniques were used to obtain 3D EBSD data in an investigation of dynamic recrystallization in a Cu-2%Sn bronze alloy. The results of this investigation show the origin of the nucleation sites for dynamic recrystallization and also elucidates the orientation relationship of the recrystallized grains to the deformed, prior grains and between the dynamically recrystallized grains.

Systematic Characterization of DRIE-Based Fabrication Process of Silicon Microneedles

2007 ◽  
Vol 1052 ◽  
Author(s):  
Jochen Held ◽  
Joao Gaspar ◽  
Patrick Ruther ◽  
Matthias Hagner ◽  
Andreas Cismak ◽  
...  
Keyword(s):  
Cross Sections ◽  
Focused Ion Beam ◽  
Process Analysis ◽  
Ion Beam ◽  
Scanning Electron Micrographs ◽  
Systematic Analysis ◽  
Deep Reactive Ion Etching ◽  
Etching Parameters ◽  
Anisotropic Etch

AbstractThis paper reports on the systematic characterization of a deep reactive ion etching based process for the fabrication of silicon microneedles. The possibility of using such microneedles as protruding microelectrodes enabling to electroporate adherently growing cells and to record intracellular potentials motivated the systematic analysis of the influence of etching parameters on the needle shape. The microneedles are fabricated using dry etching of silicon performed in three steps. A first isotropic step defines the tip of the needle. Next, an anisotropic etch increases the height of the needle. Finally, an isotropic etch step thins the microneedles and sharpens their tip. In total, 13 process parameters characterizing this etching sequence are varied systematically. Microneedles with diameters in the sub-micron range and heights below 10 µm are obtained. The resulting geometry of the fabricated microneedles is extracted from scanning electron micrographs of focused ion beam cross sections. The process analysis is based on design-of-experiment methods to find the dominant etch parameters. The dependence of the needle profiles on process settings are presented and interpolation procedures of the geometry with processing conditions are proposed and discussed.

scholarly journals Failure Analysis of Wire Bonding on Strain Gauge Contact Pads Using FIB, SEM, and Elemental Mapping

2021 ◽  
Vol 6 (1) ◽  
pp. 53
Author(s):  
Muhammad Talal Asghar ◽  
Thomas Frank ◽  
Frank Schwierz
Keyword(s):  
High Temperature ◽  
Strain Gauge ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Wire Bonding ◽  
Elemental Mapping ◽  
Sintering Process ◽  
Height Difference ◽  
Root Cause ◽  
Bond Pads

Stacks consisting of titanium, platinum, and gold layers constitute a popular metallization system for the bond pads of semiconductor chips. Wire bonding on such layer stacks at different temperatures has extensively been investigated in the past. However, reliable information on the bondability of this metallization system after a high-temperature sintering process is still missing. When performing wire bonding after pressure sintering (at, e.g., 875 °C), bonding failures may occur that must be identified and analyzed. In the present study, a focused ion beam (FIB), scanning electron microscopy (SEM), and elemental mapping are utilized to characterize the root cause of failure. As a probable root cause, the infusion of metallization layers is found which causes an agglomerate formation at the interface of approximately 2 μm height difference on strain gauge contact pads and possibly an inhomogeneous mixing of layers as a consequence of the high-temperature sintering process. Potential treatment to tackle this agglomeration with the removal of the above-mentioned height difference during the process of contact pad structuring and alternative electrical interconnect methodologies are hereby suggested in this paper.

Position Controlled GaN Nano-Structures Fabricated by Low Energy Focused Ion Beam System.

2003 ◽  
Vol 792 ◽  
Author(s):  
Takahiro Nagata ◽  
Parhat Ahmet ◽  
Takashi Koida ◽  
Shigefusa F. Chichibu ◽  
Toyohiro Chikyow
Keyword(s):  
Nitrogen Source ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Surface Treatments ◽  
Low Energy ◽  
Atomic Nitrogen ◽  
Sem Observation ◽  
Nano Structures ◽  
Beam System ◽  
Nucleation Sites

ABSTRACTWe have demonstrated position controlled GaN nano structures with a combination of surface treatments and nucleation sites control assisted by low energy focused ion beam. Ga ions in the range of 100 eV - 10 keV were irradiated onto the surface of the As-terminated Si (100) to create the nucleation sites. The deposited Ga atoms migrated on the surface and were trapped at the nucleation sites to form Ga droplets. Subsequently an excited atomic nitrogen source was supplied to the surface. By SEM observation, the GaN microcrystals of diameter about 800 nm were found to be allocated every 2 μm periodically on the substrates, and cathodoluminescence peaks from GaN nano structures were observed.

The Microstructure Evolution of Corrosion Phenomenon on Aluminum Bond Pads

2005 ◽  
Author(s):  
Jian-Shing Luo ◽  
Hui-Min Lo ◽  
Jeremy D. Russell
Keyword(s):  
Electron Microscopy ◽  
Microstructure Evolution ◽  
Photoelectron Spectroscopy ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
X Ray ◽  
Nano Crystalline ◽  
Transmission Electron ◽  
Layer Structures ◽  
Bond Pads

Abstract X-ray photoelectron spectroscopy (XPS) is a very popular tool for identification of the chemical state of fluorine contamination on aluminum (Al) bond pads. To date, as far as the authors are aware the detailed microstructures of fluorine corrosion on bond pads have not been reported. This paper reports the microstructure evolution of fluorine corrosion on bond pads in a plastic box under specific environment conditions by using transmission electron microscopy (TEM), optical microscopy, focused ion beam and scanning electron microscopy (SEM). The elemental distributions and chemical bonding were performed by using Gatan Image Filter/TEM, energy dispersive X-ray/Scanning TEM (STEM), Auger electron spectroscopy and XPS, respectively. On Al pads with 35 atomic %, fluorine residual, corrosion was observed after around 10 days of storage and became more severe with time. The corrosion layers consist of nano-crystalline and amorphous for both single and double-layer structures.

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