Backside Defect Research Articles

Backside Defect Evaluation in Carbon Steel Plate Using a Hybridized Magnetic Flux Leakage and Eddy Current Technique

Backside Defect Evaluation in Carbon Steel Plate Using a Hybridized Magnetic Flux Leakage and Eddy Current Technique

Rectangular wave eddy current testing using for imaging of backside defects of steel plates

Accurate, easy, and fast inspection of defects on the backside of thick steel plates is essential for the maintenance of infrastructures. Low frequency eddy current testing (LF-ECT) is a promising method to detect defects of the backside of steel plates, with a thickness of approximately 10 mm. However, it is possible that the signal from the backside defect is smaller than that from the surface magnetic noise, causing difficulty identifying the backside defect. In this study, we propose a method to reduce the surface noise by employing a square wave inverter to generate a harmonic signal (rectangular wave ECT, or RECT), and the result demonstrates that the surface noise is successfully reduced using the harmonic signal.

Flat/film infinity coils and backside defect searching

Flat/film infinity coils and backside defect searching

A Study on Backside Defect Searching by Low Frequency Excitation of the ∞ Coil

A Study on Backside Defect Searching by Low Frequency Excitation of the ∞ Coil

Focus Spot Reduction by Brush Scrubber Cleaning

of preventive backside cleaning steps. These cleaning steps can be introduced after processes that generated high backside defect counts or right before a lithographic wafer exposure. In this study that was performed at imec’s 300mm cleanroom facility, the study objective was to evaluate the focus spot reduction performance of a stand-alone scrubber in a case study featuring known focus spot generating equipment sets. . In the first part of the study, monitoring of various production tools in terms of backside cross-contamination was done. A set of equipment’s that generated high backside defect counts was selected for generating adequate backside contaminated test material for the cleaning evaluation. This backside contaminated test material was used in our cleaning experiments and evaluation of focus spot reduction by performing leveling tests on an immersion scanner that was able to measure out of plane deviations.

Improvement of Back-Side Cosmetic Defects And Wafer Strength

The continued challenge to keep up with Moore's law with aggressive device scaling, and shrinking wiring dimensions established perpetual need for novel materials and dictates ever tighter semiconductor process fidelity. Despite large progress with reducing defect densities on the device side of Si wafers, considerably less attention is being paid to the wafer back-side. Back-side wafer defects have been shown to reduce yield by leading to die breakage during packaging processes. Scratches and voids formed on the back-side of the wafer during various manufacturing processes have been shown to create weak spots on the wafer, which can act as initiation points for die crack formation and propagation. In this paper, we present the technical details of a back-side wet etch clean process which helps reducing back-side defect densities significantly. The process is set up on a single wafer wet etch tool at IBM's East Fishkill 300 mm wafer fabrication facility. The process removes the outer back-side layer of the silicon wafer which has become defective and damaged as a result of previous processing steps. This new defect removal process increases die strength, which is measured as wafer mechanical strength, and removes surface defects from the back-side of the wafer. Our results show that removal of 15–30 microns from the wafer back-side reduces the amount of cosmetic defects on the back-side of the wafer by 90%, while increasing die strength by 60%. The effects of the back-side wet etch clean process on the wafer optical appearance and mechanical properties were characterized, and supporting data such as atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), defect inspection, thermal interface material adhesion test, and die strength is included. Results from package level modules indicate an increase in reliability compared to the uncleaned Si back-side. It can be concluded that wet Si removal process described in this paper is a viable method to reduce the back-side defect density with an associated increase in final module product yield.

Experimental and analytical study for detectability of the back-side flaws of flat ferromagnetic plates by RFECT

In the present study, two types of ferrite core probes were prepared with different pick-up coil positions for remote field eddy current testing. One probe has a pick-up coil on the beam of the U-type ferrite core, and the other probe has a pick-up coil on the pole of the U-type ferrite core. The two types of probes were examined for their capability to create an effective remote field to detect a back-side defect. The results showed that the pick-up coil at the pole of the U-type ferrite core can detect an effective remote field phenomenon. In addition a time harmonic analysis was carried out, and the flow of the magnetic flux of the direct field was used to analyze the difference in the results with the two probes. The detectability for back-side flaws was confirmed with the proposed probes. Compared to a previous study, the signal measured from back-side flaws with the type II probe was large. However, the signal-to-noise (SN) ratio for the detection of back-side flaws did not improve because of the different background signal before and after the back-side flaw.

Backside Defect Localizations and Revelations Techniques on Gallium Arsenide (GaAs) Devices

Backside Defect Localizations and Revelations Techniques on Gallium Arsenide (GaAs) Devices

FLIP-chip and “backside” techniques

Abstract State-of-the-art techniques for failure localization and design modification through bulk silicon are essential for multi-level metallization and new, flip chip packaging methods. The tutorial reviews the transmission of light through silicon, sample preparation, and backside defect localization techniques that are both currently available and under development. The techniques covered include emission microscopy, scanning laser microscope based techniques (electrooptic techniques, LIVA and its derivatives), and other non-IR based tools (FIB, e-beam techniques, etc.).