Abstract The failure analysis using transmission electron microscopy (TEM) has been actively preceded in semiconductor industry. But due to the overlap issue and structural complexity of devices, it has become harder and harder to perform failure analysis using normal projected bright field (BF) and high angle annular dark field (HAADF) TEM images. To overcome these problems, 3-dimensional (3D) tomography technique has been suggested. In this work, we clarify the root cause of dark voltage contrast (DVC) failure at the bottom electrode contact region in PCRAM by using 3D tomography analysis. The 3D tomography samples were prepared in lamella shape by using focused ion beam (FIB). The electron energy loss spectroscopy (EELS) and 3D tomography analysis in scanning transmission electron microscope (STEM) HAADF mode were carried out. Through 3D tomography image reconstruction by AMIRA program, we observed ‘open contact fail’ between the BEC (Bottom Electrode Contact)-1 and the BEC (Bottom Electrode Contact)-2 at DVC region that could not be shown in 2D image.

Abstract Focused ion beam (FIB) microscopy is an essential technique for the site-specific sample preparation of atom probe tomography (APT). The site specific APT and automated APT sample preparation by FIB have allowed increased APT sample volume. In the workflow of APT sampling, it is very critical to control depth of the sample where exact region of interest (ROI) for accurate APT analysis. Very precise depth control is required at low kV cleaning process in order to remove the damaged layer by previous high kV FIB process steps. We found low kV cleaning process with 5 kV and followed by 2kV beam conditions delivers better control to reached exact ROI on Z direction. This understanding is key to make APT sample with fully automated fashion.

Abstract The development of a characterization workflow for reliable pore characterization of porous metals especially for microelectronics applications is very important. This will help to provide design guidelines for the production and for the improved reliability of the devices. In this paper, we set up a workflow to accurately evaluate the porosity, of four different porous copper materials. The porous thin films are fabricated by using stencil printing. Within the workflow we use for the measurement non-destructive micro-X-ray computed tomography (ƒÝ-XCT) and destructive high-resolution scanning electron focused ion beam nano-tomography (nano-FIB tomography). The latter will be also used to calibrate the threshold for the ƒÝ-XCT image data, since a direct evaluation of the porosity from the non-destructively obtained ƒÝ-XCT image data due to resolution and contrast is not possible. Therefore, we develop an indirect histogram based evaluation method to get the porosity of the porous copper thin films. We validate and discuss the obtained results with respect to further studies.

Abstract Technology evolution in the data storage industry is driven by the continuous scaling down of devices and by an increasing complexity of the critical elements in the devices. Focused ion beam - scanning electron microscope (SEM) tomography can enable characterization of a device over its entire volume, while maintaining the resolution of the SEM. This study introduces the quantitative 3D tomography technique developed in the data storage industry to specifically address the industrial process development needs. In the detail section, the methodology of 3D reconstruction is introduced, key parameters are reviewed, and the steps for a successful 3D tomographic reconstruction are described. The study presents typical applications of 3D analysis for device design and process development to illustrate the benefits and unique learning opportunities. By reconstructing all slice-view 2D images quantitatively, 3D device structures and related 3D metrology data can be obtained.

Abstract Cross sections of large Through Silicon Vias (TSV) and solder bumps are often prepared using the Focused Ion Beam (FIB). The high current Xe plasma ion source allows fast and precise target preparation of TSV with small diameter. Solder bumps can be accessed due to the high milling rate too. However, the high current milling by plasma FIB causes the worsening of the milled surface quality. An optimized FIB scanning strategy accompanied with the novel rocking stage for the sample tilting during the milling has been developed for the plasma FIB. Whole milling process is observed by the Scanning Electron Microscopy (SEM). Time to prepare a cross section is accelerated and the excellent quality is suitable for subsequent failure analysis. Also important is proper sample cleaving before FIB milling. Using an accurate method to cleave the sample prior to FIB preparation further reduces the overall sample preparation time. The high quality cross sections prepared using this new method are ready not only for SEM but also for EDX and EBSD analysis, either 2D or 3D, when combined with FIB slicing. Broadening the analysis to these techniques increases the obtainable information, allowing the arrangement of materials and their crystalline structure to be studied in a detail.

Abstract This paper describes the application of 3D FIB-SEM tomography as a method for quantifying process variations across the die and across the wafer, as well as layout investigations. In this study, the analysis of results acquired by 3D FIB-SEM tomography were applied to a 64L 3D-NAND device where process induced variation in the high aspect ratio vertical memory channels is measured and to a double stack 3D-NAND architecture, which is comprised of two 32-layer stacks where eccentricity of the pillars was evaluated for layers in both upper and lower stacks. In addition, a partial layout of a 14nm logic device is investigated by this method, demonstrating the capabilities for structural verification, and structural overlay of elements from a 7nm logic device were also evaluated. The results demonstrate the value of 3D FIB-SEM tomography for physical confirmation of the structural layout, which can be applied towards device debug and reverse engineering.

Abstract An advanced technique for site-specific Atom Probe Tomography (APT) is presented. An APT sample is prepared from a targeted semiconductor device (commercially available product based on 14nm finFET technology). Using orthogonal views of the sample in STEM while FIB milling, a viable APT sample is created with the tip of the sample positioned over the lightly-doped drain (LDD) region of a pre-defined PFET. The resulting APT sample has optimal geometry and minimal amorphization damage.

Abstract We have exploited an innovative X-ray tomography system, which is hosted in a Scanning Electron Microscope (SEM). The resolution reached by this equipment is closed to 160nm in 2 dimensions. We imaged Through Silicon Vias (TSV) which have undergone a manufacturing defect and characterized voids within these interconnections.

Abstract Continuing advances in Atom Probe Tomography and Focused Ion Beam Scanning Electron Microscope technologies along with the development of new specimen preparation approaches have resulted in reliable methods for acquiring 3D subnanometer compositional data from device structures. The routine procedure is demonstrated here by the analysis of the silicon-germanium source-drain region of a field effect transistor from a de-packaged off-the-shelf 28 nm design rule graphics chip. The center of the silicon-germanium sourcedrain region was found to have approximately 180 ppm of boron and the silicide contact was found to contain both titanium and platinum.

Abstract Prior to x-ray tomography, cylindrically-shaped samples are obtained using an innovative milling strategy on a Plasma-FIB. The method presented consists of tuning the ion dose as a function of pixel coordinates along with optimization of the scan geometries, drastically reducing the preparation time and significantly improving the overall workflow efficiency.

Abstract 3D tomography of TSVs was performed by combining Xe plasma FIB milling and lift-out techniques. This approach allows analyzing the structure of TSVs in detail using a method faster than the usual 3D tomography by Ga FIB and more precise than X-ray tomography. Both well-filled TSVs and TSVs with voids were analyzed and the results were compared. The analysis procedure was optimized in order to reduce the analysis time and to increase the throughput. The lift-out of the analyzed block of material was performed to obtain 90° angle between TSV and the ion beam axes, which is critical to reduce the curtaining effect and which allowed to increase FIB beam current significantly, reducing the analysis time.

Abstract Focused Ion Beam sample preparation for electron microscopy often requires large volumes of material to be removed. Prior efforts to increase the rate of bulk material removal were mainly focused on increasing the primary ion beam current. Enhanced sputtering yield at glancing ion beam incidence is known, but has not found widespread use in practical applications. In this study, etching at glancing ion beam incidence was explored for its advantages in increasing the rate of bulk material removal. Anomalous enhancement of material removal was observed with single raster etching in along-the-slope direction with toward-FIB raster propagation at glancing ion beam incidence. Material removal was inhibited with raster propagation away from FIB. The effects of glancing angle and ion dose on depth of cut and volume of removed material were also recorded. We demonstrated that the combination of single-raster etching in along-the-slope direction by raster propagating toward-FIB at glancing incidence and a “staircase” type of etching strategy holds promise for reducing the process time for bulk material removal in FIB sample preparation applications.

Abstract There are many opportunities in semiconductor processing where atom probe tomography (APT) analysis of a finished product is desirable; competitive analysis and failure analysis are two good examples, and only recently have APT results been obtained from fully processed "off-the-shelf" transistor structures that are part of a finished product. This paper explores the feasibility of APT analysis for fully packaged integrated-circuit microelectronic devices by detailing the various options available in specimen preparation and the resulting analyses. The goal of this work is to take an off-the-shelf microelectronics product and perform APT analysis on various device-level components. This work demonstrates that a wealth of high quality information may be obtained from site-specific APT analysis of post-production microelectronic devices. The yield of useful results from such analyses has not yet been determined, but the small number of specimens analyses (four) yielded quality results in the first attempt.

Abstract Silicon photonics is a disruptive technology that aims for monolithic integration of photonic devices onto the complementary metal-oxide-semiconductor (CMOS) technology platform to enable low-cost high-volume manufacturing. Since the technology is still in the research and development phase, failure analysis plays an important role in determining the root cause of failures seen in test vehicle silicon photonics modules. The fragile nature of the test vehicle modules warrants the development of new sample preparation methods to facilitate subsequent non-destructive and destructive analysis methods. This work provides an example of a single step sample preparation technique that will reduce the turnaround time while simultaneously increasing the scope of analysis techniques.

Abstract In semiconductor manufacturing technology, copper has been widely used for BEOL process due to better conductivity than aluminum. TEM (Transmission Electron Microscopy) characterization has been played in key role to understand the process of semiconductor manufacturing. Gallium base Focused Ion Beam (FIB) is widely used on TEM sample preparation. The experiment to understand the impact of gallium which is from sample preparation process on Cu layer was performed. In-situ TEM studies have shown real time material characteristic of Cu at various temperature [1]. We observed the gallium aggregation phenomenon on Cu layer at round the temperature of 400°C. This thermal aggregation of gallium on Cu layer has been confirmed by EDS analysis in the study. Detectable amount of gallium was found in whole area in the sample before heating the sample at in-situ TEM work. This paper also introduces alternative solutions to resolve this gallium aggregation in copper layer including the sample preparation technique using Xe Plasma Focused Ion Beam (PFIB) [2]. This Xe PFIB showed the substantial improvement of specimen quality for the in-situ TEM experiment of sample preparation.

Abstract A technique for preparation of a pillar shaped sample and its multi-directional observation of the sample using a focused ion beam (FIB) / scanning transmission electron microscopy (STEM) system has been developed. The system employs an FIB/STEM compatible sample rotation holder with a specially designed rotation mechanism, which allows the sample to be rotated 360 degrees [1-3]. This technique was used for the three dimensional (3D) elemental mapping of a contact plug of a Si device in 90 nm technology. A specimen containing a contact plug was shaped to a pillar sample with a cross section of 200 nm x 200 nm and a 5 um length. Elemental analysis was performed with a 200 kV HD-2300 STEM equipped with the EDAX genesis Energy dispersive X-ray spectroscopy (EDX) system. Spectrum imaging combined with multivariate statistical analysis (MSA) [4, 5] was used to enhance the weak X-ray signals of the doped area, which contain a low concentration of As-K. The distributions of elements, especially the dopant As, were successfully enhanced by MSA. The elemental maps were reconstructed from the maps.

Abstract In this paper, a workflow consisting of a pico-second laser tool followed by a broad argon beam tool is proposed as a solution for extremely large area preparation with surfaces suitable for SEM and FIB based analysis directly after polishing in the broad argon beam tool. Results are presented discussing the advantages of this workflow in terms of speed, size and quality of the surface for electron microscopy analysis. The use of the broad argon beam tool to complete the process produces near perfect interfaces especially compared to mechanical preparation techniques on the multilayers with vastly different properties found in advanced packages. Additionally, the tool can be used for backside thinning and reducing front side delayering.

Abstract Presentation slides from the ISTFA 2021 tutorial, “[Charged Particle Systems: Fundamentals and Opportunities].”

Abstract Increased insight into the internal structure of microelectronic devices can be achieved through the use of three dimensional (3D) imaging based on image stacks of serial sections obtained with a combined electron and ion beam (CrossBeam) FIB. This study describes how such data can be collected and presented, some of the factors that need to be optimized to get the best images, and the limitations of the method. It can be viewed as a first step in the emerging area of high resolution 3D microscopy, a technique that can lead to more accurate characterization of the shapes of internal structures and their interconnectivity at the nanoscale.

Abstract This paper discusses the development of an extensible programmatic workflow that leverages evolving technologies in 2D/3D imaging, distributed instrument control, image processing, and automated mechanical/chemical deprocessing technology. Initial studies involve automated backside mechanical ultra-thinning of 65nm node IC processor chips in combination with SEM imaging and X-ray tomography. Areas as large as 800μm x 800μm were deprocessed using gas-assisted plasma FIB delayering. Ongoing work involves enhancing the workflow with “intelligent automation” by bridging FIB-SEM instrument control and near real-time data analysis to establish a computationally guided microscopy suite.