Hua Younan

Characterization studies of fluorine-induced corrosion crystal defects on microchip Al bondpads using X-ray photoelectron spectroscopy

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 Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) techniques. In this paper, we further studied F-induced corrosion and defects, and characterized the composition of the “crystal-like” defects using XPS. The experimental results showed that the major component of the “crystal-like” defect was Al fluoride of AlF₃. The percentages of the components of the “crystal-like” defects on the affected bondpad are: Al (22.2%), Al₂O₃ (5.4%), AlF₃(70.0%) and [AlF₆]^3- (2.4%). During high-resolution fitting, the binding energies of Al (72.8eV)Al₂O₃ (74.5eV), AlF₃ (76.3eV) and [AlF₆]^3- (78.7eV) were used.

Studies of TEM/EDX data process and application in identification of Cu oxide compounds

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 for an unknown sample. Generally, it is to use the atomic percentage Wia (excluding Pt from the sample preparation), which can be easily achieved by a certain data processing, to identify the chemical state composition. For example, in this paper, we studied the layers composition on Cu substrate, which was consisting of CuO and CuiO.

Studies on XPS valence state analysis of copper materials

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 Cu+ from Cu as their difference of the 2p3 energy (0.20 eV) is less than the energy resolution of the XPS tool. In this paper, we will study the method to identify and distinguish Cu+ from Cu by using LMM energy peak in XPS spectra.

ATR-FTIR, DUAL BEAM FIB-SEM, TEM and TOF-SIMS studies on high temperature and moisture induced “white haze” following the pattern of electrodes in touch panels

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 touch panels, is first reported. It is suspected that the white haze is a moisture induced reflection alteration phenomenon of the OCA (optically clear adhesive), while the electrodes related pattern is highly dependent on the local variation in hygroscopic swelling.

XPS and TEM studies of oxidation states on Sn solder ball

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 the values from TEM measurements.

Characterization studies of non-stick on pad (NSOP) using AES, XPS and TOF-SIMS

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 analysis results showed that the root causes were attributed to either wafer fabrication or assembly process such as Si underetch, Ni2O3 contamination and tape (with PDMS) residue.