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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...
This paper few case studies of Auger elemental analysis in failure analysis of wafer fabrication, using a state-of-the-art scanning Auger nanoprobe, will be presented. Material identification in particle defects is quite challenging especially in advanced microelectronic technologies, 90nm and beyond, where, due to decreasing device size, the tight pitch and high aspect ratio of features introduces...
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,...
To identify nitride from oxide layer on the trench, it is necessary to perform BOE chemical staining. However, chemical staining using BOE will damage the oxide layer, causing inaccurate readings in the oxide gauging measurement in the trench. Moreover, damage on the oxide layer caused heavy charging at the side of the trench and the surface of oxide layer. In this paper, we proposed to coat a Cr...
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 3 form Al-F complex compound, such as [AlF6]3-. [AlF6]3- formed may become an anode and further chemical...
Energy-dispersive X-ray microanalysis technique has been commonly used in failure analysis. It is vital for an analyst to understand the electron penetration depth in a certain material so as to be able to select an appropriate accelerating beam voltage. In this paper, we will use the Monte Carlo electron flight simulation method to obtain the electron penetration data at the different beam acceleration...
In this paper, an ET high via resistance case was investigated. TEM/EDX technique was used for identification of the root cause. Failure mechanism of Al fluoride defects is discussed. Some preventive actions/solutions were implemented to improve the process margin and eliminate the problem.
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...
Airborne boron and phosphorus contaminations on wafer surface has been analysed by TOF-SIMS. A known boron and phosphorus concentration BPSG sample was used as reference for the calibration of the TOF-SIMS. The detection limit reaches 1E8 at/cm2 for boron and 1E10 at/cm2 for phosphorus. This method is easy to applied and no sample preparation required. So TOF- SIMS is a very good monitoring technique...
In this paper, Al fluoride defects on microchip Al bondpads were studied, which were confirmed to be due to a 12 hours delay prior to NE111 clean process. Failure analysis results and mechanism were discussed. Moreover, a preventive solution of introducing a time link between passivation etch and NE111 clean process was recommended and implemented.
In this paper, an FIB method using progressive multi-cut technique is proposed and it has been applied in failure analysis of wafer fabrication. The application results showed that this method would greatly improve FIB cut success rate, especially for invisible defects. A case study on Vbd ramp up failure after QBD short loop will be presented.
This paper presents the effects of Auger electron spectroscopy on semiconductor device's threshold voltage performance. Bond pads connected to gate of transistors were exposed to different beam energy of 0, 3, 5, 10, 15 and 20 keV for an average of 2.5 minutes. Vt measurements were collected once at pre-exposure and thrice at post-exposure. The evaluation results show that the transistor Vt was impacted...
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