Zhao Siping

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Studies on Failure Mechanism of Al Fluoride Oxide-AlxOyFz on Microchip Al Bondpads

IEEE International Conference on Semiconductor Electronics (2006)

Hua Younan Zhao Siping Rao Ramesh Kun Li

Al fluoride oxide on microchip Al bondpads may cause non-stick on pad (NSOP) problem during bonding process. In this study, a failure mechanism to form Al fluoride oxide-AlxOyFz has been proposed. Based on the failure mechanism, F contamination on Al bondpads, it will chemically react with Al and form Al-F complex compound, such as [AlF6]3. [AlF6]3- formed may become an anode and further chemical reaction from O2 and moisture (H2O) will occur at the cathode and form the new product, OH-ions, which will undergo chemical reaction with Al to form Al(OH)3, and then become Al2O3. Finally, Al-F complex compound may further chemically react with Al2O3 to form Al fluoride oxide-AlxOyFz.

Failure mechanism

10.1109/smelec.2006.380686

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Plane-view Transmission Electron Microscopy for Advanced Integrated Circuit

IEEE International Conference on Semiconductor Electronics (2006)

Pan Liu K. Li E.R. Eddie Zhao Siping

In this paper, the authors try to introduce three techniques for plane-view TEM sample preparation. First, traditional plane-view TEM sample preparation will be introduced. The second technique is FIB- based lift-out method, which places the sample on the carbon film. This technique is used to cut isolated defects, such as SRAM single bit failure, but this technique introduces artifacts from FIB ion damage and carbon film. The last technique is a combination of tripod polishing, FIB milling and ion milling. Specific cases will be given to illustrate the application of these techniques.

Tripod (photography)

Ion milling machine

Sample Preparation

Sample (material)

10.1109/smelec.2006.380709

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Failure Analysis of Pitting Problem on Microchip Al Bondpads in Wafer Fabrication

IEEE International Conference on Semiconductor Electronics (2006)

Tai Eve Hua Younan Rao Ramesh Zhao Siping

A bond pad failure mechanism of galvanic corrosion was studied. Analysis results showed that over-etch process, EKC and DI water over cleaning revealed more pitting with Cu seed due to galvanic corrosion. To control and eliminate galvanic corrosion, the etch recipe was optimized and etch time was reduced about 15% to prevent damaging the native oxide. EKC cleaning time was remaining unchanged in order to maintain bond pad F level at minimum level. In this study, the PRS process was also optimized and CF4 gas ratio was reduced about 45%. Moreover, O2 process was added after PRS process so as to increase the native oxide layer on Al bondpads to prevent galvanic corrosion.

Galvanic cell

Galvanic corrosion

Pitting Corrosion

Wafer Bonding

10.1109/smelec.2006.380763

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Citations (7)

Failure Analysis of NSOP Problem Due to Al Fluoride Oxide on Microchip Al Bondpads

IEEE International Conference on Semiconductor Electronics (2006)

Zhao Siping Hua Younan Rao Ramesh Kun Li

A NSOP due to Al fluoride oxide case was investigated. The NSOP problem on microchip Al bondpads was reported. SEM, EDX, TEM and Auger FA techniques were used to identify the root cause. Optical inspection did not show any abnormality, however, high magnification SEM inspection found the "white dot"-like defects. TEM and Auger analysis results showed that a thicker oxide layer on bondpads, which was about 200-300 A. After studies on failure mechanism, it was concluded that the thicker layer detected by TEM was not Al oxide layer (Al2O3), but it was Al fluoride oxide- AlxOyFz. which was due to F contamination during polyimide ashing process. In this paper we will further discuss the failure mechanism proposed and explain the formation of the Al fluoride oxide-AlxOyFz.. In this paper, the possible root cause and eliminating solution are also studied. After changing a new dedicated ashing process machine, the F contamination was eliminated.

Ashing

10.1109/smelec.2006.380783

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Citations (4)

Studies on A New Sela-FIB Sample Preparation Method and Its Application in Failure Analysis of Wafer Fabrication for 110nm Technology Node and Beyond

IEEE International Conference on Semiconductor Electronics (2006)

Zhao Siping Hua Younan E.R. Eddie Khoo Ley Hong

In this paper, a novel sample preparation method for obtaining high-resolution SEM profile is proposed. Both Sela fine cleave and FIB slice techniques have been used for SEM sample preparation. Using this new method, high-resolution 90 degrees SEM micrographs are provided. It has been applied in failure analysis to check Via gouging information without any charging problem, which helps us to reduce TEM analysis samples.

Sample Preparation

Sample (material)

Wafer fabrication

10.1109/smelec.2006.380784

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Citations (1)