scholarly journals Practical Methodologies in Restoring Initial Failure Mode and Backside Focused Ion Beam Cross-Section for Defect Visualization

Author(s):  
Alvina Jean Tampos ◽  
Karl Villareal

Abstract Complementary Metal-Oxide Semiconductor (CMOS) Image Sensors are gaining popularity most especially in Automotive Safety and Advanced Driver-Assistance Systems (ADAS) applications. Customer application modules involve oftentimes a third party supplier. When failures involve interaction between an image sensor die and the customer's module, the Failure Analyst has to know the exact failure mechanism to pinpoint whether root cause is in the die fabrication (fab) or packaging assembly (third party supplier). Challenges can befall the analyst: failure modes can recover which renders the unit functional and laboratories most often do not have complete sophisticated analytical laboratory equipment for electrical testing, fault isolation and sample preparation. In this paper, a case study of a CMOS Image Sensor is presented wherein the failure mode recovered which was restored and how the structural limitations were overcome for fault isolation on both front- and back-side. A modified process flow was performed to visualize the defect through backside Focused Ion Beam (FIB) cross-section.

Author(s):  
E. Hendarto ◽  
S.L. Toh ◽  
J. Sudijono ◽  
P.K. Tan ◽  
H. Tan ◽  
...  

Abstract The scanning electron microscope (SEM) based nanoprobing technique has established itself as an indispensable failure analysis (FA) technique as technology nodes continue to shrink according to Moore's Law. Although it has its share of disadvantages, SEM-based nanoprobing is often preferred because of its advantages over other FA techniques such as focused ion beam in fault isolation. This paper presents the effectiveness of the nanoprobing technique in isolating nanoscale defects in three different cases in sub-100 nm devices: soft-fail defect caused by asymmetrical nickel silicide (NiSi) formation, hard-fail defect caused by abnormal NiSi formation leading to contact-poly short, and isolation of resistive contact in a large electrical test structure. Results suggest that the SEM based nanoprobing technique is particularly useful in identifying causes of soft-fails and plays a very important role in investigating the cause of hard-fails and improving device yield.


Author(s):  
Huixian Wu ◽  
James Cargo ◽  
Huixian Wu ◽  
Marvin White

Abstract The integration of copper interconnects and low-K dielectrics will present novel failure modes and reliability issues to failure analysts. This paper discusses failure modes related to Cu/low-K technology. Here, physical failure analysis (FA) techniques including deprocessing and cross-section analysis have been developed. The deprocessing techniques include wet chemical etching, reactive ion etching, chemical mechanical polishing and a combination of these techniques. Case studies on different failure modes related to Cu/low k technology are discussed: copper voiding, copper extrusion; electromigration stress failure; dielectric cracks; delamination-interface adhesion; and FA on circuit-under-pad. For the cross-section analysis of copper/low-K samples, focused ion beam techniques have been developed. Scanning electron microscopy, EDX, and TEM analytical analysis have been used for failure analysis for Cu/low-K technology. Various failure modes and reliability issues have also been addressed.


Author(s):  
Douglas J. Martin ◽  
Matthew J. Gadlage ◽  
Wai-Yat Leung ◽  
Jeffrey L. Titus

Abstract An application-specific integrated circuit (ASIC) for a high reliability application is found to have a missing sidewall spacer in a single transistor. Manufacturer burn-in and standard component electrical tests do not capture this defect. The defect manifests after exposure to ionizing radiation. Photon emission microscopy (PEM), laser voltage imaging (LVI), and laserassisted device alteration (LADA) are used to isolate the failure site. At the failure site a focused ion beam (FIB) cross section indicates that a doubly doped drain (DDD) (N+) is likely present where a lightly doped drain (LDD) is designated. This defect leads to a failure mode that is consistent with hot-carrier injection in complementary metal-oxide semiconductor (CMOS) transistors. This paper presents the testability from a fault isolation aspect, shmoo plot characterization, and backside optical techniques to identify its spatial location. A discussion of the results includes why ionizing radiation allowed the defect’s capture and potential implications of using ionizing radiation as a viable failure analysis technique.


Author(s):  
Lorenzo Motta ◽  
Paolo Veneto ◽  
Mark Antolik ◽  
Donato Di Donato

Abstract Focused ion beam (FIB) circuit edit (CE) is an integral part of IC debug, fault-isolation, and low yield analysis. Regarding FIB microsurgery, complexity is growing with the shrinking of dimensions of lower level metallization while the redistribution layer (RDL) structures can increase in all three dimensions. This requires continuous development of CE processes to address these opposite dimension trends and material variations. There are two venues to address CE, accessing from the front side (FS) or from the back side (BS) of an IC. This paper describes the FS techniques and methodologies developed to edit the RDL technology. The goal of this work is to demonstrate on a Cu GND/power plane the performance of the halogen-based contamination process. Results shows that the benefit of reduced time to remove thick Cu metallization is surely advantageous for CE throughput as well as for improving edit success rates.


2018 ◽  
Author(s):  
Sang Hoon Lee ◽  
Jeff Blackwood ◽  
Stacey Stone ◽  
Michael Schmidt ◽  
Mark Williamson ◽  
...  

Abstract The cross-sectional and planar analysis of current generation 3D device structures can be analyzed using a single Focused Ion Beam (FIB) mill. This is achieved using a diagonal milling technique that exposes a multilayer planar surface as well as the cross-section. this provides image data allowing for an efficient method to monitor the fabrication process and find device design errors. This process saves tremendous sample-to-data time, decreasing it from days to hours while still providing precise defect and structure data.


Author(s):  
H. J. Bender ◽  
R. A. Donaton

Abstract The characteristics of an organic low-k dielectric during investigation by focused ion beam (FIB) are discussed for the different FIB application modes: cross-section imaging, specimen preparation for transmission electron microscopy, and via milling for device modification. It is shown that the material is more stable under the ion beam than under the electron beam in the scanning electron microscope (SEM) or in the transmission electron microscope (TEM). The milling of the material by H2O vapor assistance is strongly enhanced. Also by applying XeF2 etching an enhanced milling rate can be obtained so that both the polymer layer and the intermediate oxides can be etched in a single step.


Author(s):  
J. Douglass ◽  
T. D. Myers ◽  
F. Tsai ◽  
R. Ketcheson ◽  
J. Errett

Abstract This paper describes how the authors used a combination of focused ion beam (FIB) microprobing, transmission electron microscopy (TEM), and data and process analysis to determine that localized water residue was causing a 6% yield loss at die sort.


Author(s):  
Chuan Zhang ◽  
Jane Y. Li ◽  
John Aguada ◽  
Howard Marks

Abstract This paper introduces a novel sample preparation method using plasma focused ion-beam (pFIB) milling at low grazing angle. Efficient and high precision preparation of site-specific cross-sectional samples with minimal alternation of device parameters can be achieved with this method. It offers the capability of acquiring a range of electrical characteristic signals from specific sites on the cross-section of devices, including imaging of junctions, Fins in the FinFETs and electrical probing of interconnect metal traces.


Author(s):  
Dirk Doyle ◽  
Lawrence Benedict ◽  
Fritz Christian Awitan

Abstract Novel techniques to expose substrate-level defects are presented in this paper. New techniques such as inter-layer dielectric (ILD) thinning, high keV imaging, and XeF2 poly etch overflow are introduced. We describe these techniques as applied to two different defects types at FEOL. In the first case, by using ILD thinning and high keV imaging, coupled with focused ion beam (FIB) cross section and scanning transmission electron microscopy (STEM,) we were able to judge where to sample for TEM from a top down perspective while simultaneously providing the top down images giving both perspectives on the same sample. In the second case we show retention of the poly Si short after removal of CoSi2 formation on poly. Removal of the CoSi2 exposes the poly Si such that we can utilize XeF2 to remove poly without damaging gate oxide to reveal pinhole defects in the gate oxide. Overall, using these techniques have led to 1) increased chances of successfully finding the defects, 2) better characterization of the defects by having a planar view perspective and 3) reduced time in localizing defects compared to performing cross section alone.


Author(s):  
X. Yang ◽  
X. Song

Abstract Novel Focused Ion Beam (FIB) voltage-contrast technique combined with TEM has been used in this study to identify a certain subtle defect mechanism that caused reliability stress failures of a new product. The suspected defect was first isolated to a unique via along the row through electrical testing and layout analysis. Static voltage contrast of FIB cross-section was used to confirm the suspected open defect at the via. Precision Transmission Electron Microscope (TEM) was then used to reveal the detail of the defect. Based on the result, proper process changes were implemented. The failure mode was successfully eliminated and the reliability of the product was greatly improved.


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