In electronic packaging, it is very important to understand and control the interfacial microstructure formed due to the reaction between the metallization scheme and solders. Often, the interfacial reaction is exploited/controlled to obtain an optimum properties of the joints. The strength and interfacial properties of the solder joints are determined by the interfacial microstructure. The evolution of interfacial microstructure in solder joints is governed by the diffusion path during processing and in service. Even though the semiconductor industry uses a wide variety of complex metallization schemes, recently the Pd-Ni metallization scheme on Cu has gained a lot of interest. Furthermore, the design of new metallization scheme(s) to control the interfacial microstructure and to improve the quality of solder joints is the cornerstone of advanced electronic packaging. We have carried out a systematic study of diffusion and interfacial reaction, both in the liquid and solid states, between Pb-Sn eutectic solder and the Pd-Ni metallization scheme on Cu.

For over two decades considerable effort has been directed towards the development of Al-Li base alloys with the objective of replacing conventional high aluminum alloys, due to the fact that lithium additions cause substantial reduction in density accompanied by significant increase in the elastic modulus, implying, therefore, in appreciable improvement in the specific properties of the resulting alloys. These properties depend on the miscrostucture evolution during heat treatment or welding cycle. The microstructure of the commercial Al-Li systems is complex due to the addition of alloying elements, which increases the number of the allowed stable and metastable phases. During the thermo-mechanical processing of the 2091 alloy, the probable metastable are δ’, GPB zones and S’, the stable phases are S, T2 and the high temperature R (1-3). Further, the Zr precipitates the Al3Zr. The present study deals with the microstructure evolution of welded joints of the 2091 alloy studied by transmission electron microscopy, TEM.

A Ti50Ni48Fe2 alloy, which is famous as a typical shape memory alloy, exhibits the cubic (parent phase) to trigonal (R-phase) martensitic transformation upon cooling. It is well known that this structural transformation is accompanied by some precursor phenomena, such as appearance of weak diffuse scattering in electron diffraction patterns of the parent phase. Since the diffuse scattering is visible at around 1/31/3 0 and its equivalent positions in diffraction patterns, as similar to the superlattice reflections in the R-phase, it is believed to be closely related with the formation of the R-phase. However, neither structural nor morphological aspect of this pre-martensitic state is clear, since a precise analysis of the weak diffuse scattering is quite difficult along with a conventional electron microscopy, because of the presence of strong background arising from inelastic scattering. The purpose of the present work is to precisely observe the weak diffuse scattering and to reveal the structural and morphological features of the pre-martensitic state by electron microscopy with the aid of a recently developed omega-type magnet.

Power electronic circuits are used in electric vehicle or hybrid electric vehicle to drive the main electric motor. All the transistors and diodes in a sealed power electronic package will experience repeated high current cycling during their service life. The aluminum bonding wires which connect these devices to the rest of the circuit will experience repeated thermal strain cycling. When design a power electronic package, the thermal fatigue durability of these bonding wires would be a concern. A power electronic module with pure aluminum bonding wires of 0.5mm in diameter from a vendor was power cycled with the following schedule. Each transistor in the circuit was on for 10 seconds with the current at 400 Amperes followed by the transistor being off for 30 seconds. The wires from the diodes to the copper trace lines are about twice as long as those from the transistors to the copper trace lines.

Among those intermetallic phases in Zn-Fe system formed in the hot-dip galvanized coating and/or galvanneal coating, the microstructure of Γ phase was the least mentioned. The Γ phase form in the coating layer is usually too thin to observe by a microscope. However, it has been reported that the performance of coating is closely related to the microstructure of Γ phase. Tokunaga et al. has reported that the cracks were generated from the Γ layer or Γ+δ layer. Y.Lin et al. demonstrates that coherent interface forms between Γ and steel interface on annealed electrogalvanized steel sheets indicating that failure would not occur at this interface.

Samples used in this study were lab-made hot-dip galvanized steel sheets. To investigate the microstructure of coating, especially the Γ phase layer, specimens were heated to create the designed layer interface. It was found that the heat-treated conditions ranged from 700°C to 750°C for one hour was appropriate to observe the nucleation and growth of Γ phase layer.

X-ray diffraction (XRD) techniques can readily be utilized for the characterization of textures in crystalline materials. The advantages of XRD techniques are: 1) the test is nondestructive, 2) samples can easily be prepared, and 3) data can be collected and analyzed quickly.

Three low-C steel tin mill coils were manufactured during a mill trial which was conducted to optimize the processing parameters necessary for the production of material with low cup earing behavior. The processing parameters evaluated included hot mill conditions (roughing, finishing and coiling temperatures), cold rolling conditions (during first and second cold reduction), and continuous annealing conditions (line speed and strip temperature). Samples A, B, and C were secured from the coil center-width position of each coil, respectively, and were analyzed via XRD.

Properties such as normal anisotropy (r bar) and planar anisotropy (Δ r), have been correlated with an X-ray Intensity Ratio (XIR) at the Technical Center of National Steel.

Electron channeling contrast imaging (ECCI), performed using a scanning electron microscope, has been used to observe dislocations in bulk TiAl with a duplex microstructure. The ECCI technique is based on the dependence of the back-scattered electron (BSE) yield (of the incident beam orientation) on the crystal lattice and defect orientation near the specimen surface. This allows nearsurface defects to be imaged in bulk specimens [1, 2]. ECCI was carried out in a Camscan 44FE FEG-SEM operated at 25 kV using a beam divergence of ∽8 mrad and a beam current of ∽ 2nA. Specimens were observed at a working distance of approximately 11 mm. To record the BSE signal, the microscope was fitted with an annular (four quadrant) silicon diode detector array attached to the final lens pole-piece, resulting in a solid angle collection of approximately ∽0.6 π str. Images were recorded as 32 frame averages using ∽1.1 frames/sec.

Transmission electron microscopy in its modern high-resolution analytical form has great potential for elucidating mechanisms of environmental cracking in structural alloys and other materials. Apart from a few pioneering efforts, the difficulties of preparing suitable samples with the original corrosion structures preserved in narrow crack tips have limited contributions of TEM in this area. Recent work involving cross-sectional crack preparation has focused on intergranular stress-corrosion cracking of Fe- and Ni-base stainless alloys in high-temperature water. This presentation will illustrate preparation methods that have proven successful, and describe limitations of the analysis.

The method for preparing cross-section samples suitable for high-resolution TEM characterization is based on earlier work by Lewis et al. It involves preparing a thin section containing cracks filled with epoxy, dimple grinding selected locations near the crack tip, and ion milling. Figure 1 schematically illustrates this method. The first step is to preserve the crack opening characteristics present under loading and protect the crack surfaces during thinning.

The combination of focused ion beam (FIB) sputtering with transmission electron microscopy (TEM) offers new opportunities for the nanoscale characterization of materials. The FIB may be used to prepare membranes for TEM imaging which are: (i) Site selective, i.e. the membranes may be placed with sub-micron precision in all three dimensions, (ii) Largely free of differential sputtering artifacts, such that membranes may be prepared which are of constant thickness from structures with very dissimilar materials, and (iii) Of precisely known geometry.

The challenges associated with FIB specimen preparation will also be discussed and are summarized in Figure 1: (a) Surface amorphization damage, (b) Residual differential sputtering effects, (c) Redeposition of sputtered material and (d) Membrane bowing due to internal or beaminduced stresses. It will be demonstrated that each of these effects can be sufficiently controlled to allow high quality diffraction contrast imaging in a wide range of materials.

The use of focused ion beams (FIB) to prepare site specific specimens for transmission electron microscopy (TEM) and scanning electron microscopy (SEM) has been well documented. The 5 to 7 nm resolution on the latest FIB instruments has enhanced the ability to locate and expose features of interest. The use of the lift-out technique of FIB specimen preparation removes the need for prior thinning of the sample for TEM analysis and permits the study of materials that were difficult or impossible to do previously. Use of high current (10 nA) FIB instruments makes specimen preparation possible in less than one hour; automatic operation of FIB instruments will further reduce this time. After milling in the FIB, specimens are micromanipulated in air onto a 3 mm diameter TEM sample grid coated with carbon. The ability to analyze lift-out specimens using other analytical techniques that can take advantage of this site specific capability was previously suggested.

There is a trend in electron microscopy towards centralization of the more sophisticated EM systems. The rationale is that the techniques associated with such instrumentation are more efficiently practiced and developed by dedicated specialists in a regional or national centre surrounded by an extensive infrastructure. A similar argument can be used for the preparation of TEM specimens, especially as the demand grows for more precise location of the thin area to be examined. A new trio of techniques - tripod polishing, ultramicrotomy, and focused ion beam (FIB) thinning - can locate the thin area to within a micron or less. In the first two, a linear feature first located via light or scanning electron microscopy can be cross-sectioned by controlled material removal via mechanical polishing or diamond knife sectioning, respectively. With FIB, feature location and material removal are carried out in-situ, first imaging with a low intensity beam, then milling trenches on either side of the feature with a high intensity beam that is decreased as the feature is approached.

The focused ion beam (FIB) miller has been widely accepted as a powerful tool in the semiconductor industry. However, it is now finding applications in more general materials science applications. The high resolution, energetic gallium ion beam can rapidly and precisely section materials to reveal their internal structure; one particularly valuable application being the preparation of thin foils for TEM examination, especially from heterogenous materials.

To date, TEM sample preparation using FIBs has concentrated on semiconductor cross-sections [1], powders [2], and surface treated materials, e.g. galvanized steels [3]. However, thin foils of grossly heterogeneous materials, such as metal-matrix composites, are also difficult to prepare using conventional methods and are therefore well suited to sectioning using the FIB. In this study, thin foils were prepared from two composite materials: a 7075 aluminium alloy containing a 20% volume fraction of SiC particles and a FeAl alloy containing a 60% volume fraction of WC particles.

As features on an IC chip become smaller than the resolution power of an optical microscope and of the size of the grinding particles, the trend for preparing cross-sectional transmission electron microscopy (TEM) samples at specific locations (bits) is moving towards using a focused ion beam (FIB) machine. Details on how to use a FIB machine to prepare cross-sectional TEM samples have been outlined in many references.The general procedure is to first mark the specific location (bit) in the FIB machine and then grind the sample down to about 20 microns, 10 microns on each side of the feature of interest. After grinding, the sample is mounted on a pre-cut TEM grid and thinned with the FIB to about 0.1 micron in the region containing the feature of interest. There are several disadvantages to this method. First, the sample goes into the FIB machine at least twice—once for FIB marks on the location and once again for the final thinning.

Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) has become less useful for semiconductor samples as feature dimensions decrease. It has become increasingly difficult to get sufficient signal from small features because of the large interaction volume of the primary beam. As the interaction volume is dependent on the accelerating energy of the primary electron beam, decreasing the accelerating voltage will decrease the interaction volume. This increases the percentage of signal from the feature of interest, but also lowers the number of peaks available for interpretation, reducing the sensitivity of the analysis. Several elements commonly used in the fabrication of semiconductors have overlapping peaks at lower energies, and the ability to distinguish between them is lost at low accelerating energies. It is possible to modify samples using Focused Ion Beam (FIB) to improve EDS resolution without decreasing the accelerating voltage.

The samples were prepared in an FIE 800 FIB and imaged in an Hitachi S-4700 SEM.

1. Introduction

The FIB (focused ion beam) is now widely accepted as the most site-specific TEM preparation tool and as such proves to be highly valuable when analysing ULSI devices. However, using high-energy Gallium ions for milling induces amorphization of the crystal surfaces. A method able to quantify this surface alteration on silicon using a combination of CBED (convergent beam electron diffraction) and EELS (electron energy loss spectroscopy) is presented. CBED is a powerful tool that also can generate an accurate measure of crystal thickness. EELS can yield the total sample thickness, so from the difference the combined amorphous layers can be assessed. Two sets of application results are presented: the first one is obtained on a FIB thinned sample using an ion energy of 50 keV and the second set of results confirms the validity of the proposed method on a mechanically polished specimen with no subsequent ion milling.

1. Introduction.

With continuing reductions in semiconductor device dimensions high spatial resolution physical and chemical analysis techniques will be more and more required for defect analysis and process development in the microelectronics field. Transmission Electron Microscopy (TEM) analysis is now extensively used thanks to the fast Focused Ion Beam (FIB) specimen preparation technique which has furthered its development. Recently, we have shown the advantages of adding Electron Energy Loss Spectroscopy (EELS) to FIB-TEM analysis for semiconductor process characterization. In this paper we extend the EELS technique using FIB sample preparation to Energy Filtering TEM (EFTEM) observations. The EFTEM analysis allows high-resolution compositional mapping using spectroscopic imaging of core level ionization edges3. We show some applications of FIB-EFTEM to defect analysis and process development.

2. Experimental details.

The FIB system is a MICRION model 9500 EX using a gallium ion beam of 50 keV maximum energy with a 5 nm minimum spot diameter.

Focused ion beam (FIB) thinning of materials to electron transparency is now a routine procedure for preparation of specimens for transmission electron microscopy (TEM) of microelectronic materials and devices. The nano-scale structural damage, including implantation and amorphization due to this ion milling process has been well investigated and documented. In this paper, we discuss the micro-scale structural damage observed in copper/low-k materials and our efforts to minimize the extent of the damage without compromising the overall specimen preparation time.

Figure 1 shows an area-specific cross-sectional specimen prepared from a copper/low-k via-chain test structure using the FIB-milling technique. The procedure involved mechanical thinning of a transverse wafer sliver followed by FIB-milling the area of interest to electron transparency according to conventional steps and conditions' using a liquid Ga+ ion source FIB system. The evidence of structural damage in terms of melting and/or sputtering of the metallization is visible at different areas.

Preparation of precision planar TEM specimen for failure analysis in microelectronics industry has become increasingly difficult as the critical dimensions of integrated circuits (ICs) continue to shrink down to deep sub-micron regime. Accurate defect localization and endpoint control of specimen final thinning are critical steps leading to successful specimens and defect characterization. Conventional dimple and ion-mill method becomes inadequate for this class of specimen preparation due to poor optical imaging resolution, non-planar polishing, lack of flexible ion beam control and in situ process monitoring for endpoint control. These problems are exacerbated by the high density and a wide range of materials found in IC device structures. In this paper we present a novel method employing dual-beam focused ion beam (FIB) which significantly improves upon these difficulties.

The Scanning Transmission Electron Microscope (STEM) can provide images beyond Scanning Electron Microscope (SEM) capability, on samples which do not have to be prepared to the degree required for Transmission Electron Microscopy (TEM). For some applications, such as semiconductor production, speed of analysis is critical. This paper explores Focused Ion Beam (FIB) sample preparation for STEM.

The samples were prepared using an Hitachi FB-2000A FEB tool. Two analysis regions of similar thickness were cut. The rough sample was milled using a 500 pA beam and no polish cut. The smooth sample was prepared by cutting first with a 500 pA beam, and then using additional, smaller diameter beams, concluding with a 30 pA beam. This resulted in a sample surface polished to a degree similar to that used for TEM specimens. The samples were imaged in an Hitachi HD-2000 STEM at 200KeV. Transmission electron images taken at 100 kx are shown in Figure 1 of the rough sample and of the smooth sample.

Focused Ion Beam (FIB) specimen preparation for both scanning and transmission electron microscopy (SEM and TEM respectively) has seen an increase in usage over the past few years. The advantage to the FIB is that site specific cross sections (or plan view sections) may be fabricated quickly and reproducibly from numerous types of materials using a finely focused beam of Ga+ ions [1,2]. It was demonstrated by Prenitzer et al. that TEM specimens may be acquired from individual Zn powder particles by employing the FIB LO specimen preparation technique [3]. In this paper, we use the FIB LO technique to prepare TEM specimens from Mount Saint Helens volcanic ash.

Volcanic ash from Mount Saint Helens was obtained at the Microscopy and Microanalysis 1998 meeting in Atlanta. TEM analysis of the ash was performed using the FIB lift out technique [1]. Ash powders were dusted onto an SEM sample stud that had been coated with silver paint.