Studies of Galvanic Corrosion (Al-Ti Cell) on Microchip Al Bondpads and Elimination Solutions

2007 ◽  
Author(s):  
Hua Younan ◽  
Mo Zhiqiang ◽  
Zhao Siping ◽  
Gong Hao
Keyword(s):  
Theoretical Model ◽  
Failure Mechanism ◽  
Galvanic Corrosion ◽  
Metal Corrosion ◽  
Al Metallization

Abstract Galvanic corrosion (two metal corrosion) on microchip Al bondpads may result in discolored or non-stick bondpad problem. In this paper, a galvanic corrosion case at bondpad edge will be presented. Besides galvanic corrosion (Al-Cu cell), a concept of galvanic corrosion (Al-Ti cell) is proposed, which is used to explain galvanic corrosion at bondpad edge with layers of TiN/Ti/Al metallization structure. A theoretical model of galvanic corrosion (Al-Ti cell) is proposed to explain chemically & physically failure mechanism of galvanic corrosion at bondpad edge. According to the theoretical model proposed in this paper, galvanic corrosion on microchip Al bondpads could be identified into two corrosion models: galvanic corrosion (Al-Cu cell) occurred mostly at the bondpad center and galvanic corrosion (Al-Ti cell) occurred specially at bondpad edge with TiN/Ti/Al metallization structure. In this paper, a theoretical model of galvanic corrosion (Ai-Ti cell) will be detail discussed so as to fully understand failure mechanism of galvanic corrosion the bondpad edge. Moreover possible solutions to eliminate galvanic corrosion (Al-Ti cell) are also discussed.

Unique Autoclave Stress Induced Failure Mechanism

2005 ◽  
Author(s):  
John Butchko ◽  
Bruce T. Gillette
Keyword(s):  
Corrosion Rate ◽  
Grain Boundary ◽  
Failure Analysis ◽  
Failure Mechanism ◽  
Metal Corrosion ◽  
Corrosion Mechanism ◽  
Reliability Testing ◽  
Process Change ◽  
Transistor Reliability ◽  
Pass Through

Abstract Autoclave Stress failures were encountered at the 96 hour read during transistor reliability testing. A unique metal corrosion mechanism was found during the failure analysis, which was creating a contamination path to the drain source junction, resulting in high Idss and Igss leakage. The Al(Si) top metal was oxidizing along the grain boundaries at a faster rate than at the surface. There was subsurface blistering of the Al(Si), along with the grain boundary corrosion. This blistering was creating a contamination path from the package to the Si surface. Several variations in the metal stack were evaluated to better understand the cause of the failures and to provide a process solution. The prevention of intergranular metal corrosion and subsurface blistering during autoclave testing required a materials change from Al(Si) to Al(Si)(Cu). This change resulted in a reduced corrosion rate and consequently prevented Si contamination due to blistering. The process change resulted in a successful pass through the autoclave testing.

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.

Simulation and Test of through Silicon Vias Impacted by Large Current Pulse

2015 ◽  
Vol 645-646 ◽  
pp. 190-194
Author(s):  
Xu Ran Ding ◽  
Ya Bin Wang ◽  
Wen Zhong Lou ◽  
Fang Yi Liu
Keyword(s):  
Theoretical Model ◽  
Failure Mechanism ◽  
Current Pulse ◽  
Comsol Multiphysics ◽  
Testing System ◽  
Through Silicon Vias ◽  
Large Current ◽  
Weak Points ◽  
Silicon Vias

The failure mechanism of through silicon vias impacted by large current pulse is reported. A theoretical model has been built to describe how TSVs fails when impacted by large current pulse. The theoretical model is then solved by applying COMSOL Multiphysics and the weak points of the TSV have been pointed out. By applying the large current pulse generating and testing system, an experiment has been done to verify the theoretical model. The results show that although the TSVs may be broken down when impacted by large current pulse, it can still be function by using several TSVs in parallel.

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.

Pre-Annealing of TiN Barriers in Al Metallization of Silicon

1984 ◽  
Vol 37 ◽  
Author(s):  
W. Sinke ◽  
P. K. Stout ◽  
F. W. Saris
Keyword(s):  
High Temperature ◽  
Failure Mechanism ◽  
Compound Formation ◽  
Barrier Failure ◽  
Barrier Performance ◽  
Higher Temperature ◽  
Al Metallization

AbstractWe have studied the influence of a high-temperature pre-anneal on the barrier performance of TiN in Al metallization of Si. The results show that barrier failure is shifted towards a higher temperature by 20°C-40°C when the barrier is pre-annealed at 600°C-800°C. In addition, we studied the failure mechanism and found that the barrier breaks down by compound formation.

scholarly journals Weld Strength of Laser Welded SS316 and SS321

2020 ◽  
Vol 9 (7) ◽  
pp. 1319-1322
Keyword(s):  
Stainless Steel ◽  
Galvanic Corrosion ◽  
Weight Ratio ◽  
Dissimilar Materials ◽  
High Strength ◽  
Optical Microscope ◽  
Metal Corrosion ◽  
Weld Strength ◽  
Potential Candidate ◽  
Dissimilar Welds

Nowadays, due to economic considerations, stainless steel is frequently used in dissimilar welds configurations– alloyed steel, carbon steel, copper, titanium. Current research in laser welding aims at joining a large category of structurally dissimilar materials, like copper, stainless steel or aluminum components. The weld quality of 10mm thick stainless steel grades of 316 and 321 laser welded in butt configuration is studied. SS321 is well known for its corrosion resistance property especially dissimilar metal corrosion ie., galvanic corrosion. SS316 provides high strength to weight ratio even at high temperature which makes its as a potential candidate for aerospace application. The joint quality is characterized in terms of hardness, microstructure and inspected using NDT. Scanning Electron Microscope and Optical Microscope were used to study the microstructure of welded specimen. The microhardness test is conducted on the weld joints to quantify the effect of weld parameters in mechanical strength of the joints. Radiography test was conducted to identify the defects in the specimen.

Failure Mechanism Studies and Elimination of Galvanic Corrosion (Al-Cu Cell) on Microchip Aluminum Bondpads in Copper Process

2015 ◽  
Author(s):  
Hua Younan ◽  
Chen Yixin ◽  
Fu Chao ◽  
Li Xiaomin
Keyword(s):  
Failure Mechanism ◽  
Galvanic Corrosion ◽  
Metal Layer ◽  
Al Alloy ◽  
Weak Point ◽  
Root Cause ◽  
Weak Points ◽  
Barrier Metal ◽  
Root Cause Identification

Abstract In the authors' previous papers, the failure mechanism and elimination solutions of galvanic corrosion (Al-Cu cell) on microchip Al bondpads in the Al process (0.18un and above) have been studied [1-2]. In this paper, the authors will further study the failure mechanism and root cause of galvanic corrosion (Al-Cu cell) on microchip Al bondpads in the Cu process (0.13um and below) with Ta barrier metal. Based on our results, the root cause of galvanic corrosion (Al-Cu cell) in the Al process is only one way and Al-Cu cell is from Al alloy (Al + 0.5%Cu) on Al bondpads. However, in the Cu process it may be from two ways and Al-Cu cell can be from both Al alloy (Al + 0.5%Cu) on Al bondpads and the Cu metal layer below the barrier metal Ta when Ta has weak points or pinhole. As such, the pinhole defects on Al bondpad caused by galvanic corrosion (Al-Cu cell) in the Cu process might be more serious than that in the Al process. In this paper, TEM is used for root cause identification. Based on the TEM results, galvanic corrosion was due to the weak point/pinhole at the Ta barrier metal layer and Al-Cu diffusion.

Studies of Silicon Dust Corrosion on Microchip Al Bondpads and Elimination of Silicon Dust During Wafer Sawing Process

2006 ◽  
Author(s):  
Hua Younan ◽  
Zhao Siping ◽  
Mo Zhiqiang ◽  
Cho Jie Ying
Keyword(s):  
Theoretical Model ◽  
Galvanic Corrosion ◽  
Complex Compounds ◽  
Assembly Process ◽  
Corrosion Problem ◽  
Sawing Process

Abstract After wafer-die sawing process, sometimes silicon (Si) dust on microchip Al bondpads is difficult to be cleaned away by DI water, especially at pinhole/corrosive areas caused by galvanic corrosion, thus resulting in non-stick on pads (NSOP) problem in assembly process. To eliminate NSOP problem due to Si dust contamination, in this paper, we will study the mechanism of Si dust contamination and propose a concept of Si dust corrosion. A theoretical model will be introduced so as to explain Si dust contamination and corrosion problem during wafer die sawing process. Based on the mechanism proposed, Si dust contamination and corrosion is related to galvanic corrosion as OH- ions generated from galvanic corrosion will not only react with Al to cause Al corrosion, but also react with Si dust to cause Si dust corrosion. During Si dust corrosion, poly-H2SiO3 and Si-Al-O complex compounds will be formed on Al bondpads, especially at the pinholes/corrosive areas. Poly-H2SiO3 and Si-Al-O complex compounds are “gel-like” material and stick onto the surface of bondpads. It is insoluble in water and difficult to be cleaned away by DI water during or after wafer die sawing process and will cause bondpad discoloration or/and NSOP problem. Some eliminating methods of Si dust contamination and corrosion on Al bondpads during wafer die sawing process are also discussed.

scholarly journals A Theoretical Model for Metal Corrosion Degradation

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
David V. Svintradze ◽  
Ramana M. Pidaparti
Keyword(s):  
State Physics ◽  
Stainless Steel ◽  
Theoretical Model ◽  
Solid State ◽  
Corrosion Rate ◽  
Governing Equation ◽  
Pitting Corrosion ◽  
Metal Corrosion ◽  
Solid State Physics ◽  
Steel Alloys

Many aluminum and stainless steel alloys contain thin oxide layers on the metal surface which greatly reduce the corrosion rate. Pitting corrosion, a result of localized breakdown of such films, results in accelerated dissolution of the underlying metal through pits. Many researchers have studied pitting corrosion for several decades and the exact governing equation for corrosion pit degradation has not been obtained. In this study, the governing equation for corrosion degradation due to pitting corrosion behavior was derived from solid-state physics and some solutions and simulations are presented and discussed.

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