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In this paper, we studied the Al bondpad qualification methodologies and application in backend process optimization and improvement so as to provide good quality bondpads and wafers in wafer fabrication. The three Al bondpad qualification methodologies including OSAT, SLAT and Wafer Die Sawing Test were introduced and discussed.
TEMJEDX analysis techniques are widely used in failure analysis. Based on TEM results, one can know the structures of the sample e.g. in anomalous or crystalline, as well as the thickness of the thin film layer. Typically, TEM/EDX results can only provide the elemental information of the sample. In this paper, we discussed a standardless EDX analysis method to identify the chemical state composition...
XPS analysis technique can be used for valence state analysis. However, due to the limitation of the energy resolution of XPS, it can be difficult to differentiate the valence state of some elements. In this study, the Scanning XPS Microscope PHI Quantera II was used to analyze and identify Cu2O from Cu. Although the equipment possesses good energy resolution (0.48 eV), it is still difficult to distinguish...
In the wafer fabrication (fab) and assembly process, process underetch residue and material contamination on bondpads may cause NSOP (non-stick on pad) problem. In this paper, the root cause of 3 NSOP cases were discussed and identified by using Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) techniques. Our failure...
White haze or the so called mura effect has been recognized as a common defect in touch panels. Nevertheless, the underlying mechanism has not been fully understood and clearly investigated. In this study, a comprehensive characterization study using the ATR-FTIR, DUAL BEAM FIB-SEM, TEM and TOF-SIMS on the high temperature and moisture induced white haze, which follows the pattern of electrodes in...
In wafer fabrication, Fluorine (F) contamination may cause F-induced corrosion and defects on microchip Al bondpad, resulting in bondpad discoloration or non-stick on pad (NSOP). In the previous paper [1], the authors studied the F-induced corrosion and defects, characterized the composition of the “flower-like” defects and determined the binding energy of Al fluoride [AlF6]3- using X-ray Photoelectron...
A Sn oxide layer on the surface of Sn solder balls plays an important role in the semiconductor packaging industry. This paper shows a comprehensive analysis of the Sn oxide layer by XPS depth profiles. The distribution of Sn with different oxidation states can be derived from curves fitting Sn3d5/2 peaks. Moreover, the oxide layer thicknesses obtained from XPS demonstrate a linear correlation with...
In this study, failure analysis was conducted to investigate the root cause of Ti/Ni/Ag film peeling from Si wafer surface. The adhesion strength of Ti/Ni/Ag film on Si was quantitatively measured by 4 Point Bending method (4PB), where a novel delamination initiation method was introduced to significantly reduce the energy barrier for the delamination initiation. The possible contamination elements...
Energy-dispersive X-ray microanalysis technique has been widely used in failure analysis of wafer fabrication. However, we still face some common problems. In this study, we introduce standardless element coefficients to improve accuracy of quantitative results, propose an estimating method to select beam acceleration voltage & demonstrate application cases and discuss identification methods of...
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, the dependence of crystallographic orientation in Aluminum thin films grown on different barrier-metal substrate schemes (Ta or Ta/TaN) will be presented. The orientation of Al grains will be shown to have a bearing on the material characteristics, which are important in IC fabrication from the perspective of both the device functionality and reliability. X-ray powder diffraction studies...
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