Fibxtem— Focussed Ion Beam Milling for TEM Sample Preparation

1991 ◽  
Vol 254 ◽  
Author(s):  
David P. Basile ◽  
Ron Boylan ◽  
Brian Baker ◽  
Kathy Hayes ◽  
David Soza

AbstractIn the semiconductor industry, shrinking geometries and increasing process complexity have greatly increased the demand for TEM analysis of specific submicron regions. Until recently, samples of this nature have been difficult if not impossible to prepare. We have combined cross-sectional TEM sample preparation (XTEM) and the precise material sputtering of focussed ion beam milling (FIB) to thin samples to electron transparency. We call this sample preparation technique FIBXTEM.Three advantages of this technique are: 1) The area of interest can be analyzed in the scanning electron microscope before final thinning; 2) Any specific defect area becomes a candidate for TEM analysis, including failed sub-micron structures; and 3) Samples are generally artifact-free and of uniform thickness.Key elements of the FIBXTEM technique include precision planar polishing, unique holders for mounting and transferring samples between systems, and the FIB-induced deposition of a sacrificial protective layer over the area of interest during ion thinning.This technique extends the use of TEM analysis into new areas of semiconductor process development and failure analysis. Recent applications for materials problem solving and failure analysis are discussed.

Author(s):  
Raghaw S. Rai ◽  
Swaminathan Subramanian ◽  
Stewart Rose ◽  
James Conner ◽  
Phil Schani ◽  
...  

Abstract Conventional focussed ion beam (FIB) based specific area transmission electron microscopy (TEM) sample preparation techniques usually requires complex grinding and gluing steps before final FIB thinning of the sample to electron transparency (<0.25 μm). A novel technique known as lift-out, plucking or pullout method that eliminates all the pre-FIB sample preparation has been developed for specific area TEM sample preparation by several authors. The advantages of the lift-out procedure include reduced sample preparation time and possibility of specific area TEM sample preparation of most components of integrated circuit with almost no geometric or dimensional limitations. In this paper, details of liftout method, developed during the present work, for site specific x-sectional and a new site specific planar sample preparation are described. Various methodologies are discussed to maximize the success rate by optimizing the factors that affect the technique. In failure analysis, the geometric and dimensional flexibility offered by the lift-out technique can be used to prepare specific area TEM sample of back thinned die, small particles and packaged parts. Such novel applications of lift-out technique in failure analysis are discussed with the examples of TEM results obtained from GaAs and Si based devices. Importantly, it was possible to obtain high resolution lattice images from the lift-out samples transferred on holey carbon supported 3mm copper grids.


2001 ◽  
Vol 7 (S2) ◽  
pp. 948-949
Author(s):  
R. S. Rai ◽  
S. Bagchi ◽  
L. Duncan ◽  
L. Prabhu ◽  
J. Beck ◽  
...  

In recent years, the availability of focused ion beam (FIB) milling systems has given a much-needed boost for transmission electron microscopy (TEM) as a technique for site-specific analysis. Much progress has been made in the area of site-specific cross-sectional and planar TEM sample preparation techniques. However, a continuing need exists to reduce the sample preparation time, in order to improve TEM cycle time for better support of process development, yield improvement and production in a high-volume industrial environment. Thus, a faster TEM sample preparation technique is always desirable to meet this demand. A new approach to TEM sample preparation is described in this paper.Following the new approach developed in the present work, one can prepare on a single TEM grid at least two different cross-sectional samples of site-specific device structures or up to four different cross-sectional samples of blanket films. Two different samples, each containing an area of interest near the center, are cleaved or cut to a width of about 1.25 mm; these samples may be from two separate locations of a wafer, or from two different wafers where TEM analyses are required.


1998 ◽  
Author(s):  
S. Subramanian ◽  
P. Schani ◽  
E. Widener ◽  
P. Liston ◽  
J. Moss ◽  
...  

Abstract A selected area planar TEM (SAPTEM) sample preparation technique for failure analysis of integrated circuits using a transmission electron microscope has been developed. The technique employs a combination of mechanical grinding, selective wet/dry chemical etching (if required) and a two step focused ion beam IIFIB) milling. The mechanical grinding steps include: (a) a backside grind to achieve a die thickness less than 30 µm, (b) the support half ring glue, and (c) a cross-section grind from one side to reach less than 35 pm to the failing site. A selective wet or dry chemical etch is applied before, between,, or after FIB thinning depending on the nature of problem and device components. The FIB milling steps involve: (is) a high ion current cross-sectional cut to reach as close as 5-8 µm to the area of interest (b) a final planar thinning with the ion beam parallel to the surface of the die. The plan view procedure offers unique geometric advantage over the cross-section method for failure analysis of problems that are limited to silicon or certain layers of the device. Iln the cross-sectional approach, a thin section (thickness less than 250 µm) of a device is available for failure analysis, whereas in the planar procedure a 20 µm2 area of any layer (thickness less than 250 µm) of the device is available. The above advantage has been successfully exploited to identify and solve the following prablems in fast static random access memories (FSRAM): (i) random gateoxide rupture that resulted in single bit failures, (ii) random dislocations from the buried contact trenching that caused single bit failures and general silicon defectivity (e.g. implant damage and spacer edge defects), and (iii) interracial reactions.


Author(s):  
Stanley J. Klepeis ◽  
J.P. Benedict ◽  
R.M Anderson

The ability to prepare a cross-section of a specific semiconductor structure for both SEM and TEM analysis is vital in characterizing the smaller, more complex devices that are now being designed and manufactured. In the past, a unique sample was prepared for either SEM or TEM analysis of a structure. In choosing to do SEM, valuable and unique information was lost to TEM analysis. An alternative, the SEM examination of thinned TEM samples, was frequently made difficult by topographical artifacts introduced by mechanical polishing and lengthy ion-milling. Thus, the need to produce a TEM sample from a unique,cross-sectioned SEM sample has produced this sample preparation technique.The technique is divided into an SEM and a TEM sample preparation phase. The first four steps in the SEM phase: bulk reduction, cleaning, gluing and trimming produces a reinforced sample with the area of interest in the center of the sample. This sample is then mounted on a special SEM stud. The stud is inserted into an L-shaped holder and this holder is attached to the Klepeis polisher (see figs. 1 and 2). An SEM cross-section of the sample is then prepared by mechanically polishing the sample to the area of interest using the Klepeis polisher. The polished cross-section is cleaned and the SEM stud with the attached sample, is removed from the L-shaped holder. The stud is then inserted into the ion-miller and the sample is briefly milled (less than 2 minutes) on the polished side. The sample on the stud may then be carbon coated and placed in the SEM for analysis.


Author(s):  
Ching Shan Sung ◽  
Hsiu Ting Lee ◽  
Jian Shing Luo

Abstract Transmission electron microscopy (TEM) plays an important role in the structural analysis and characterization of materials for process evaluation and failure analysis in the integrated circuit (IC) industry as device shrinkage continues. It is well known that a high quality TEM sample is one of the keys which enables to facilitate successful TEM analysis. This paper demonstrates a few examples to show the tricks on positioning, protection deposition, sample dicing, and focused ion beam milling of the TEM sample preparation for advanced DRAMs. The micro-structures of the devices and samples architectures were observed by using cross sectional transmission electron microscopy, scanning electron microscopy, and optical microscopy. Following these tricks can help readers to prepare TEM samples with higher quality and efficiency.


Author(s):  
C.S. Bonifacio ◽  
P. Nowakowski ◽  
R. Li ◽  
M.L. Ray ◽  
P.E. Fischione ◽  
...  

Abstract Fast and accurate examination from the bulk to the specific area of the defect in advanced semiconductor devices is critical in failure analysis. This work presents the use of Ar ion milling methods in combination with Ga focused ion beam (FIB) milling as a cutting-edge sample preparation technique from the bulk to specific areas by FIB lift-out without sample-preparation-induced artifacts. The result is an accurately delayered sample from which electron-transparent TEM specimens of less than 15 nm are obtained.


1997 ◽  
Vol 3 (S2) ◽  
pp. 357-358
Author(s):  
C. Amy Hunt

The demand for TEM analysis in semiconductor failure analysis is rising sharply due to the shrinking size of devices. A well-prepared sample is a necessity for getting meaningful results. In the past decades, a significant amount of effort has been invested in improving sample preparation techniques for TEM specimens, especially precision cross-sectioning techniques. The most common methods of preparation are mechanical dimpling & ion milling, focused ion beam milling (FIBXTEM), and wedge mechanical polishing. Each precision XTEM technique has important advantages and limitations that must be considered for each sample.The concept for both dimpling & ion milling and wedge specimen preparation techniques is similar. Both techniques utilize mechanical polishing to remove the majority of the unwanted material, followed by ion milling to assist in final polishing or cleaning. Dimpling & ion milling produces the highest quality samples and is a relatively easy technique to master.


Author(s):  
L. A. Giannuzzi ◽  
P. R. Howell ◽  
H. W. Pickering ◽  
W. R. Bitler

A primary concern involving transmission electron microscopy (TEM) analysis is whether the electron transparent region under investigation is representative of the bulk material. TEM is frequently employed to examine the microstructure of electrodeposited materials due to their small grain size and high dislocation density. Previous work in this laboratory on palladium electrodeposits has shown that deformation twins and diffusion induced recrystallization may be induced during preparation of thin foils using both twin jet electropolishing and ion beam thinning. Recent developments in TEM sample preparation in the physical sciences include a procedure for the cross-section of heterogeneous layered materials which reduces or eliminates the need for ion milling. In this sample preparation technique, a tripod polisher device is used to mechanically polish the specimen to electron transparency. The purpose of this paper is to report on the influence of the tripod polisher sample preparation technique, on the microstructure of zinc electrodeposits.


1996 ◽  
Vol 4 (1) ◽  
pp. 8-9
Author(s):  
Dave Laken

In the November issue of this publication, we described how focused ion beam (FIB) microsurgery is used to successfully cross-section and prepare material-specific samples for SEM and TEM analysis. Material specific samples have two or more components possessing different characteristics, such as hardness and chemical etch or sputtering rates. Traditional sample preparation techniques (mechanical grinding and polishing, broad ion beam etching, and chemical etching) alter, delaminate, or destroy these samples.FIB handles the preparation of these difficult samples well because of its milling geometry and the high current density of the small beam.


Author(s):  
S. J. Kirch ◽  
Ron Anderson ◽  
Stanley J. Klepeis

The continuing reduction in the sizes of features of interest for integrated circuit failure analysis requires greater precision in transmission electron microscopy (TEM) sample preparation. With minimum feature sizes approaching 0.5 μm, the mere finding of such a feature at a polished edge, let alone preparing a TEM sample containing it becomes a formidable task. The required substantial thinning also increases the risk of loss of what may be a unique sample.We present in this paper a technique that allows localized thinning of cross-sectional TEM samples using a focused ion beam (FIB) machine. Standard preparation techniques are used to make a cross-sectional TEM sample that would otherwise be too thick to be very useful for TEM analysis. This sample is then placed in the FIB machine, which is used as a micromachining tool. No special surface preparation is necessary and the secondary electron signal generated by the ion beam provides an image that can be used to locate the feature of interest.


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