Alternative Lapping Method to Reduce Edge Rounding Effect

Author(s):  
Hock Guan Ong ◽  
Chee Lip Gan

Abstract Polishing is a simple and direct method to prepare samples for failure analysis and characterization. However, polishing commonly gives rise to the issue of rounding at the sample's corners and edges. This is believed to have arisen from the uneven distribution of polishing slurry between the edges and sample surface during polishing. Thus, we propose a new lapping method to reduce the rounding effect. From our experiments, negligible rounding effect was observed on a 9 mm by 7 mm die after a depth of ~ 2 μm of material was removed using our proposed alternative lapping method.

Author(s):  
P. Tangyunyong ◽  
A.Y. Liang ◽  
A.W. Righter ◽  
D.L. Barton ◽  
J.M. Soden

Abstract Fluorescent microthermal imaging (FMI) involves coating a sample surface with a thin fluorescent film that, upon exposure to UV light source, emits temperature-dependent fluorescence [1-7]. The principle behind FMI was thoroughly reviewed at the ISTFA in 1994 [8, 9]. In two recent publications [10,11], we identified several factors in film preparation and data processing that dramatically improved the thermal resolution and sensitivity of FMI. These factors include signal averaging, the use of base mixture films, film stabilization and film curing. These findings significantly enhance the capability of FMI as a failure analysis tool. In this paper, we show several examples that use FMI to quickly localize heat-generating defects ("hot spots"). When used with other failure analysis techniques such as focused ion beam (FIB) cross sectioning and scanning electron microscope (SEM) imaging, we demonstrate that FMI is a powerful tool to efficiently identify the root cause of failures in complex ICs. In addition to defect localization, we use a failing IC to determine the sensitivity of FMI (i.e., the lowest power that can be detected) in an ideal situation where the defects are very localized and near the surface.


Author(s):  
Joseph Myers ◽  
Marsha Abramo ◽  
Michael Anderson ◽  
Michael W. Phaneuf

Abstract As semiconductor device features continue to decrease in size from merely sub micron to below 100 nanometers it becomes necessary to mill smaller and higher aspect ratio FIB vias with reduced ion beam current. This significantly reduces the number of secondary electrons and ions available for endpoint detection and imaging. In addition FIB gas assisted etching introduces a gas delivery nozzle composed of conductive material. This component is grounded to prevent charge build up during ion beam imaging or milling. The proximity of the nozzle to the sample surface creates a shielding effect which reduces the secondary electron detection level as well [1]. The ability to enhance secondary electron imaging for end point detection is required for successful FIB circuit edit and failure analysis applications on advanced technologies. This paper reviews the results obtained using FIB Assist, an image and signal enhancement product for the FEI / Micrion platform, for critical FIB endpoint determination. Examples of FIB fabricated probe points with 30 x 30 nm FIB vias and circuit edit applications endpointing on metal 1 with high aspect ratio holes are presented.


1993 ◽  
Vol 8 (2) ◽  
pp. 122-126 ◽  
Author(s):  
Paul Predecki

A direct method is described for determining depth profiles (z-profiles) of diffraction data from experimentally determined τ-profiles, where z is the depth beneath the sample surface and τ is the 1/e penetration depth of the X-ray beam. With certain assumptions, the relation between these two profile functions can be expressed in the form of a Laplace transform. The criteria for fitting experimental τ-data to functions which can be utilized by the method are described. The method was applied to two τ-data sets taken from the literature: (1) of residual strain in an A1 thin film and (2) of residual stress in a surface ground A12O3/5vol% TiC composite. For each data set, it was found that the z-profiles obtained were of two types: oscillatory and nonoscillatory. The nonoscillatory profiles appeared to be qualitatively consistent for a given data set. The oscillatory profiles were considered to be not physically realistic. For the data sets considered, the nonoscillatory z-profiles were found to lie consistently above the corresponding τ-profiles, and to approach the τ-profiles at large z, as expected from the relation between the two.


Author(s):  
Coswin Lin ◽  
Chia-Hsing Chao

Abstract Scanning capacitance microscopy (SCM) is a powerful technique that may readily be applied to semiconductor failure analysis yielding information on problems stemming from doping issues. This paper details the study of a current leakage failure and outlines the use of the SCM technique for shallow trench isolation applications. A two-step sample preparation technique involving firstly, Chemical Mechanical Polishing (CMP) followed by a wet etch, could improve the sample surface planarization allowing SCM inspection of the STI region.


Author(s):  
Tsu Hau Ng ◽  
S. James ◽  
M.K. Dawood ◽  
P.S. Limin ◽  
H. Tan ◽  
...  

Abstract Conductive-Atomic Force Microscopy (C-AFM) is a popular failure analysis method used for localization of failures in Static Random Access Memory (SRAM) devices [1-4]. The SRAM structure has a highly repetitive pattern where any abnormality in a failed cell compared to neighboring cells could be easily identified from its current image [5-7]. Unlike topographical imaging, the C-AFM requires the probe tip to be coated with a conductive layer in order to pick up the electrical signals from the device under test. The coating needs to be sufficiently thick as it would wear off after a certain amount of physical scanning. This additional coating on the AFM tip is essential but poses a limit to the tip radius curvature. The commercially available tip radius is approximately 35nm (DDESP-10 from Bruker) and the dimension is too large for imaging of 20nm technology device. However, the limitation could be alleviated by subjecting the sample surface to treatment prior to C-AFM imaging. The aim of this surface treatment is to ensure C-AFM tip maintains sufficient scanning contact with the tiny conductive (tungsten) structure of the sample in order to achieve distinct current image. The surface treatment is done by creating a receding Inter-Layer Dielectric (ILD) from its neighboring tungsten contact. The creation of the receding depth could be achieved by either wet etching or dry etching (Reactive Ion Etching, RIE). In this work, the surface treatments by these two methods have been investigated and the recipe is optimized to obtain a clear current image. The optimized recipe is then applied on actual failure analysis where three cases are studied.


Author(s):  
Gert Ehrlich

The field ion microscope, devised by Erwin Muller in the 1950's, was the first instrument to depict the structure of surfaces in atomic detail. An FIM image of a (111) plane of tungsten (Fig.l) is typical of what can be done by this microscope: for this small plane, every atom, at a separation of 4.48Å from its neighbors in the plane, is revealed. The image of the plane is highly enlarged, as it is projected on a phosphor screen with a radius of curvature more than a million times that of the sample. Müller achieved the resolution necessary to reveal individual atoms by imaging with ions, accommodated to the object at a low temperature. The ions are created at the sample surface by ionization of an inert image gas (usually helium), present at a low pressure (< 1 mTorr). at fields on the order of 4V/Å.


Author(s):  
John R. Devaney

Occasionally in history, an event may occur which has a profound influence on a technology. Such an event occurred when the scanning electron microscope became commercially available to industry in the mid 60's. Semiconductors were being increasingly used in high-reliability space and military applications both because of their small volume but, also, because of their inherent reliability. However, they did fail, both early in life and sometimes in middle or old age. Why they failed and how to prevent failure or prolong “useful life” was a worry which resulted in a blossoming of sophisticated failure analysis laboratories across the country. By 1966, the ability to build small structure integrated circuits was forging well ahead of techniques available to dissect and analyze these same failures. The arrival of the scanning electron microscope gave these analysts a new insight into failure mechanisms.


Author(s):  
A. K. Rai ◽  
P. P. Pronko

Several techniques have been reported in the past to prepare cross(x)-sectional TEM specimen. These methods are applicable when the sample surface is uniform. Examples of samples having uniform surfaces are ion implanted samples, thin films deposited on substrates and epilayers grown on substrates. Once device structures are fabricated on the surfaces of appropriate materials these surfaces will no longer remain uniform. For samples with uniform surfaces it does not matter which part of the surface region remains in the thin sections of the x-sectional TEM specimen since it is similar everywhere. However, in order to study a specific region of a device employing x-sectional TEM, one has to make sure that the desired region is thinned. In the present work a simple way to obtain thin sections of desired device region is described.


Author(s):  
Songquan Sun ◽  
Richard D. Leapman

Analyses of ultrathin cryosections are generally performed after freeze-drying because the presence of water renders the specimens highly susceptible to radiation damage. The water content of a subcellular compartment is an important quantity that must be known, for example, to convert the dry weight concentrations of ions to the physiologically more relevant molar concentrations. Water content can be determined indirectly from dark-field mass measurements provided that there is no differential shrinkage between compartments and that there exists a suitable internal standard. The potential advantage of a more direct method for measuring water has led us to explore the use of electron energy loss spectroscopy (EELS) for characterizing biological specimens in their frozen hydrated state.We have obtained preliminary EELS measurements from pure amorphous ice and from cryosectioned frozen protein solutions. The specimens were cryotransfered into a VG-HB501 field-emission STEM equipped with a 666 Gatan parallel-detection spectrometer and analyzed at approximately −160 C.


Author(s):  
Evelyn R. Ackerman ◽  
Gary D. Burnett

Advancements in state of the art high density Head/Disk retrieval systems has increased the demand for sophisticated failure analysis methods. From 1968 to 1974 the emphasis was on the number of tracks per inch. (TPI) ranging from 100 to 400 as summarized in Table 1. This emphasis shifted with the increase in densities to include the number of bits per inch (BPI). A bit is formed by magnetizing the Fe203 particles of the media in one direction and allowing magnetic heads to recognize specific data patterns. From 1977 to 1986 the tracks per inch increased from 470 to 1400 corresponding to an increase from 6300 to 10,800 bits per inch respectively. Due to the reduction in the bit and track sizes, build and operating environments of systems have become critical factors in media reliability.Using the Ferrofluid pattern developing technique, the scanning electron microscope can be a valuable diagnostic tool in the examination of failure sites on disks.


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