The use of Atomic Force Microscopy (AFM) electrical measurement modes is a critical tool for the study of semiconductor devices and process development. A relatively new electrical mode, scanning microwave impedance microscopy (sMIM), measures a material’s change in permittivity and conductivity at the scale of an AFM probe tip [1]. sMIM provides the real and imaginary impedance (Re(Z) and Im(Z)) of the probe-sample interface. By measuring the reflected microwave signal as a sample of interest is imaged with an AFM, we can in parallel capture the variations in permittivity and conductivity and, for doped semiconductors, variations in the depletion-layer geometry. An existing technique for characterizing doped semiconductors, scanning capacitance microscopy, modulates the tip-sample bias and detects the tip-sample capacitance with a lock-in amplifier. A previous study compares sMIM to SCM and highlights the additional capabilities of sMIM [2], including examples of nano-scale capacitance-voltage curves. In this paper we focus on the detailed mechanisms and capabilities of the nano-scale C-V curves and the ability to extract semiconductor properties from them. This study includes analytical and finite element modeling of tip bias dependent depletion-layer geometry and impedance. These are compared to experimental results on reference samples for both doped Si and GaN doped staircases to validate the systematic response of the sMIM-C (capacitive) channel to the doping concentration.

Mechanical stress is a critical parameter in the design and manufacture of devices in very large scale integrated (VLSI) circuits. Whether intentionally introduced or parasitic, mechanical stress in nanoscale silicon technologies can alter carrier mobility as by as much as 25%, which can significantly affect device performance. Currently stress metrology for in-line production is conducted only at a wafer monitor level. For design purposes, the stress state in active device regions is usually inferred from electrical data. In this paper an instrument which we have developed is described for measuring mechanical stress in nanoscale silicon devices with high spatial resolution using scanning surface photovoltage microscopy (SSPVM). Other existing techniques are generally not suitable for making such measurements on production silicon nano-device structures in situ.

Carrier mobility enhancement through local strain in silicon is a means of improving transistor performance. Among the scanning probe microscopy based techniques, tip-enhanced Raman spectroscopy (TERS) has shown some promising results in measuring strain. However, TERS is known to depend critically on the quality of the plasmonic tip, which is difficult to control. In this study, a test structure is used to demonstrate the capability of photo-induced force microscopy with infrared excitation (IR PiFM) in direct measurement of strain with approximately 10 nm spatial resolution. For SiGe pitch less than about 800 nm, the region between the SiGe lines should maintain residual strain. For a region with SiGe pitch of 1000 nm, it is verified that the strain between the SiGe lines is fully relaxed. PiFM promises to be a powerful tool for studying nanoscale strain in diverse material.

Atomic force microscopy infrared (AFM-IR) technology combines the best of both worlds of AFM and IR spectro-microscopy offering high spatial resolution chemical characterization. Recent developments in the AFM-IR technique, such as tapping AFM-IR pushes the spatial resolution limit below 10 nm, making it ideal for chemically characterizing directed self assembly (DSA) components and defects for failure analysis. This paper demonstrates the chemical characterization of DSA nanopatterns using tapping AFM-IR technology with spatial resolution beyond 10 nm. Tapping AFM-IR experiments is performed on different block copolymers routinely used to fabricate directed self-assemblies on Si wafers. Along with chemical mapping, mechanical properties, such as relative stiffness and damping yielding complete chemical and mechanical property information in nanoscale to achieve material contrast, can be simultaneously probed.

Nanoscale microscopy is an important technique in analyzing current semiconductor processes and devices. Many of the current microscopy techniques can render high resolution images of morphology and, in some cases, elemental information. However, techniques are still needed to give definitive nanoscale mapping of compound materials utilized in semiconductor processes such as Si3N4, SiO2, SiGe, and low-k materials. Photo-induced force microscopy (PiFM) combines IR spectroscopy with atomic force microscopy (AFM) to provide concurrent information on topography and chemical mapping. PiFM measures the attractive dipole-dipole photo-response between the tip and the sample and does not rely on repulsive force arising from absorption-based sample expansion. As such, PiFM works well with many of the inorganic semiconductor compounds (with low thermal expansion coefficients) as well as organic materials (with high thermal expansion coefficients) [1]. In this study, various examples of nanoscale chemical mapping of semiconductor samples (surfaces processed via directed self-assembly (DSA), strain in SiGe/SiO2 structure, photoresist, etc.) will be presented, all demonstrating ~ 10 nm spatial resolution

An effective method is presented to locate certain failure sites on exposed junction of insulated-gate bipolar transistor (IGBT) devices. High emitter to collector leakage current, hereafter called ICESR, is an IGBT failure mode. The leakage current is typically related to the exposed P+/N+ junction on the die sidewall. Solder die attach residue bridging or silicon damage at this exposed P+/N+ junction are common causes of ICESR leakage. The die attach residue can be dislodged during decapsulation resulting in loss of failure information. A failure analysis flow will be described to precisely locate the ICESR leakage site without disturbing any possible die attach residue.

Multiple techniques including electrical resistance measurement plus calculation, cross-sectional view of passive voltage contrast (XPVC) sequential searching, planar and cross-section STEM are successfully used to isolate a nanoscale defect, single metallic stringer in a snakecomb test structure. The defect could not be found by traditional failure analysis methods or procedures. The unique approach presented here, expands failure analysis capabilities to the detection of nanometer-scale defects and the identification of their root causes. With continuous shrinking feature sizes, the need of such techniques becomes more vital to failure analysis and root cause identification, and therefore yield enhancement in fabrication.

The usefulness of scattering-type near-field optical microscopy for mapping the material and doping in microelectronic devices at nanoscale resolution is demonstrated. Both amplitude and phase of infrared (λ = 10.7 μm) laser light scattered by a metallised, vibrating AFM tip scanned a few nanometers above the sample are detected and transformed into images showing contrast of materials, as well as of doping concentration. Cross-sections through layers as thin as 20 nm have been clearly imaged.

As electronic devices shrink further in the nanometer regime, electrical characterization using nanoprobing has become increasingly important. Focused ion beam (FIB) is one useful technique that can be used to create markings for ease of defective site identification during nanoprobing. This paper investigates the impact of FIB exposure on the electrical parameters of the pull-up (PU), pull-down (PD) and pass-gate (PG) transistors of 6-Transistor Static Random Access Memory (6T SRAM) cells.

Nanoscale devices such as carbon nanotubes, fluorescent nanoparticles, and molecular conductors serve as a benchmark for the tools and techniques that will be required in the future to analyze processing defects and determine the cause of electronic device failures. In this paper, the authors compare and contrast the nanoscale capabilities of several imaging techniques, including STEM-in-SEM, forward scattered electron imaging, photoelectron emission microscopy, and atomic force microscopy. Along with the results of the various characterization techniques, the paper also includes a survey of the more common nanoscale devices, showing that many require more than one imaging method to make a complete and accurate assessment.

We use ultra-resolving terahertz (THz) near-field microscopy based on THz scattering at atomic force microscope tips to analyze 65-nm technology node transistors. Nanoscale resolution is achieved by THz field confinement at the very tip apex to within 30 nm. Images of semiconductor transistors provide evidence of 40 nm (λ/3000) spatial resolution at 2.54 THz (wavelength λ = 118µm) and demonstrate the simultaneous THz recognition of materials and mobile carriers in a single nanodevice. The mobile carrier contrast can be clearly related to near-field excitation of THz-plasmons in the semiconductor regions. The extraordinary high sensitivity of our microscope provides THz near-field contrasts from less then 100 mobile electrons in the probed volume.

This paper presents two case studies, based on 32nm Silicon-On-Insulator (SOI) and 28nm bulk Si technology, on finding the root cause of nanometer scale short failures using Passive Voltage Contrast (PVC), Active Voltage Contrast (AVC) and Transmission Electron Microscopy (TEM). PVC/AVC is used as precision localization technique that is critical for a successful FA-TEM analysis. Combining planar TEM sample preparation and high sensitivity Energy Dispersive Spectroscopy (EDS) mapping, a small residual filament, which is not visible even at high resolution TEM, is found to short two metal lines. The effective usage of voltage contrast and TEM provides the need of high throughput, high precision, and high resolution in the advanced FA lab that serves leading-edge semiconductor manufacturing.

Microscopic imaging and characterization of semiconductor devices and material properties often begin with a sample preparation step. A variety of sample preparation methods such as mechanical lapping and broad ion beam (BIB) milling have been widely used in physical failure analysis (FPA) workflows, allowing internal defects to be analyzed with high-resolution scanning electron microscopy (SEM). However, these traditional methods become less effective for more complicated semiconductor devices, because the cross-sectioning accuracy and reliability do not satisfy the need to inspect nanometer scale structures. Recent trends on multi-chip stacking and heterogenous integration exacerbate the ineffectiveness. Additionally, the surface prepared by these methods are not sufficient for high-resolution imaging, often resulting in distorted sample information. In this work, we report a novel correlative workflow to improve the cross-sectioning accuracy and generate distortion-free surface for SEM analysis. Several semiconductor samples were imaged with 3D X-ray microscopy (XRM) in a non-destructive manner, yielding volumetric data for users to visualize and navigate at submicron accuracy in three dimensions. With the XRM data to serve as 3D maps of true package structures, the possibility to miss or destroy the fault regions is largely eliminated in PFA workflows. In addition to the correlative workflow, we will also demonstrate a proprietary micromachining process which is capable of preparing deformation-free surfaces for SEM analysis.

The transmission electron microscope (TEM) is the standard high-resolution technique for imaging microelectronics. But TEM primarily generates contrast related to the physical structure and composition of samples, giving little insight into their electronic properties. Samples must also be electron transparent, typically requiring cross-sectioning of components to nanometers-thin foils prior to imaging, which can compromise their electronic integrity. These cross section samples are also notoriously difficult to electrically connect to without surface leakage dominating transport. As a result, successful in situ electronic testing or bias-manipulation of electronic devices in the TEM is notably rare. Here we image nanoscale, bias-induced electronic changes in an electrically contacted cross section extracted from a GaN high electronmobility transistor (HEMT). The sample is prepared using a Xe + -based plasma focused ion beam (PFIB) to eliminate conducting implantation of the standard FIB ion, Ga + . Scanning TEM electron beam-induced current (STEM EBIC) imaging visualizes bias-induced changes to the device’s electronic structure during normal biasing, stressing, and after failure, all performed in situ .

The role of scanning transmission electron microscopy (STEM) in failure analysis has been growing since the introduction of advanced technology nodes (10-nm and beyond), in which transistors (FinFET and nanosheets) have become much smaller and more complex. Four-dimensional scanning transmission electron microscopy (4D-STEM) is a new electron diffraction technique that expands conventional STEM imaging and EDX mapping to enable phase and orientation mapping of crystalline and amorphous phases in deposited thin films at the nanometer resolution. The enhancement of electron diffraction data by beam precession is then fundamental for higher accuracy and precision, especially in the case of strain measurements. The power of precession-assisted 4D-STEM analysis is demonstrated using the example of Germanium separation from within a Ge-rich GeSbTe layer in a phase memory device and with the example of tensile and compressive strain in a Samsung 5-nm technology node. These advanced electron diffraction measurements are now accessible to a broad range of users in routine analytical procedures due to unprecedented high levels of automation and synchronization in the new analytical STEM instrument, TESCAN TENSOR.

In this paper, we describe the technique of on-axis transmission Kikuchi diffraction (TKD) in a scanning electron microscope and demonstrate its use in characterizing nanoscale crystal structures and defects in semiconductor materials and devices. We explain how we modified hardware and software to achieve an effective spatial resolution of 2 nm during orientation mapping without decreasing acquisition speed, indexing quality, and other performance parameters. The paper includes illustrations comparing sample-detector geometries for conventional EBSD, TKD, and on-axis TKD. It also presents examples of the types of images that can be obtained using on-axis TKD, including raw crystal orientation maps, diffraction patterns, pattern quality maps, time-resolved orientation maps showing microstructure evolution, and a sparse sample map showing the distribution of quantum dots on an electron transparent support film.

This paper explains how embedded assist and timing control techniques are being used to improve soft defect screening in nanoscale static random access memory (SRAM). The electrical stress test method is evaluated on advanced FinFET devices. As test results show, resistive and parametric defects that are difficult if not impossible to detect using conventional techniques become visible with the aid of assist and timing control circuits.

This paper describes optical and electron beam based fault isolation approaches for short and open defects in nanometer-scale through-silicon via (TSV) interconnects. Short defects are localized by photon emission microscopy (PEM) and optical beam-induced current (OBIC) techniques, and open defects are isolated by active voltage contrast imaging in a scanning electron microscope (SEM). The results are confirmed by transmission electron microscopy (TEM) cross-sectioning.

Continuous development in the semiconductor process technology has led to the fabrication of devices with nanometer scale feature resolution. Resonance enhanced atomic force microscopy infrared (AFM-IR) is a novel technique with potential to overcome some limitations of existing tools. This manuscript illustrates chemical characterization of the nanoscale skin and polyester contaminant on silicon wafer using resonance enhanced AFM-IR spectroscopy. Resonance enhanced AFM-IR offers superior sensitivity for nanoscale organic contaminants. To demonstrate this capability, AFM-IR spectra were obtained from contaminants on silicon wafers, and the spectra correlated with a high confidence to a standard transmission FTIR spectral database. In addition, a newly developed high speed spectral acquisition scheme, which augments the reliability of nanoscale defect characterization by reducing the overall data acquisition time and enabling users to perform repeated measurements for statistical analysis, is established.

High resolution scanning probe microscopy techniques combined with infrared (IR) light sources offer unique solutions to combined chemical/mechanical/electrical characterization of defects in nanoscale dimensions. Previously, atomic force microscopy combined with infrared (AFM-IR) technology has demonstrated its capability to characterize nano-patterned metal/low-k dielectrics, nanoscale organic contaminants, and directed self-assembly of block co-polymers used for advanced micro/nanofabrications. In this paper, two complementary nanoscale chemical analysis techniques, photothermal AFM-IR and scattering type scanning near-field optical microscopy, are implemented to isolate and characterize microelectronic device cross-sections. It is observed that both techniques are able to detect patterned features with a half-pitch less than 15 nm.