Die-Level Scanning Capacitance Microscopy Fault Isolation on SOI Fin-FET Devices for Advanced Semiconductor Nodes

Measuring resistances at the nanoscale has attracted recent attention for developing microelectronic components, memory devices, molecular electronics, and two-dimensional materials. Despite the decisive contribution of scanning probe microscopy in imaging resistance and current variations, measurements have remained restricted to qualitative comparisons. Reference resistance calibration samples are key to advancing the research-to-manufacturing process of nanoscale devices and materials through calibrated, reliable, and comparable measurements. No such calibration reference samples have been proposed so far. In this work, we demonstrate the development of a multi-resistance reference sample for calibrating resistance measurements in conductive probe atomic force microscopy (C-AFM) covering the range from 100 Ω to 100 GΩ. We present a comprehensive protocol for in situ calibration of the whole measurement circuit encompassing the tip, the current sensing device, and the system controller. Furthermore, we show that our developed resistance reference enables the calibration of C-AFM with a combined relative uncertainty (given at one standard deviation) lower than 2.5% over an extended range from 10 kΩ to 100 GΩ and lower than 1% for a reduced range from 1 MΩ to 50 GΩ. Our findings break through the long-standing bottleneck in C-AFM measurements, providing a universal means for adopting calibrated resistance measurements at the nanoscale in the industrial and academic research and development sectors.

In this report, we employ phase-contrast tapping mode and conductive probe atomic force microscopy (cp-AFM) as tools to investigate the nanoscale morphology and proton conductance of a 3M perfluoro-imide acid (PFIA) membrane (625 EW) over a large range of relative humidity (3-95% RH). As a point of comparison, we also investigate 3M perfluorosulfonic acid (PFSA) (825 EW) and Nafion 212. With AFM, we assess the membrane's water retention and mechanical stability at low RH and high RH, respectively. Cp-AFM allows us to spatially resolve the hydrophilic and electrochemically active domains under a similar set of conditions and observe directly the ties between membrane morphology and proton conductance. From our data, we are able to correlate the improved water retention indicated by the size of the hydrophilic domains with the proton conductance in the PFIA membrane at elevated temperature and compare the result with that observed for the PFSA and Nafion. At high RH conditions, we see evidence of a nearly continuous hydrophilic phase, which indicates a high degree of swelling.

Investigation of Laser-fired Rear-side Point Contacts of Laser-crystallized Silicon Thin-film Solar Cells by Conductive Probe Atomic Force Microscopy

Microstructural origin of leakage current in GaN/InGaN light-emitting diodes

A scanning capacitance microscope (SCM) combines a differential capacitance measurement with an atomic force microscope (AFM). The AFM controls the position and contact force of a scanning probe tip, and a sensor simultaneously measures the capacitance between that tip and the sample under test. The capacitance sensor can detect very small (≈10 −21 F) changes in capacitance. The sensor is electrically connected to an AFM cantilevered tip that has been coated with metal to make it electrically conductive. As the SCM/AFM tip is scanned across the sample surface, simultaneous images of topography and differential capacitance are obtained. Currently, the most common application of SCM is imaging the carrier concentration variations (also known as dopant profiles) qualitatively within transistors that are part of silicon integrated circuits (ICs). Another application that has encouraged the development of commercial SCMs is the need for quantitative two‐dimensional (2‐D) carrier profiling of silicon transistors. This article reviews the history, operating principles, and applications of SCM. Special emphasis is placed on measuring quantitative 2‐D carrier profiles in silicon using SCM. This article also reviews implementation and applications of the scanning capacitance spectroscopy (SCS) technique, the intermittent contact mode of SCM (or IC‐SCM), and two other techniques that can also be classified as scanning capacitance probes: the scanning Kelvin probe microscope (SKPM), when operated at twice its drive frequency, and the scanning microwave microscope (SMWM).

In this chapter, we discuss recent developments in the characterization of polarization doped wide bandgap semiconductor (WBS) heterojunctions with an emphasis on characterization by scanning probe microscopy (SPM). Wide bandgap semiconductors, such as SiC and GaN, have a wide variety of applications in electronic and optoelectronic devices [1–6]. The operation of devices made from these materials is dominated by the polarization properties of III-N and SiC semiconductor crystals. For example, polarization doped 2 dimensional electron gas (2DEG) channels in undoped GaN/AlGaN and SiC polytypic heterojunctions have been fabricated with current densites in excess of 1A/mm. Other effects, such as surface charge instability stemming from polarization, offer interesting potentials and challenges.While some of these effects may be studied using more conventional techniques such as currentvoltage (IV) and capacitance-voltage (CV) techniques (described in sections 2 and 3), others require probes capable of investigation on the nanometer scale. Transmission electron microscopy (TEM) can be used to investigate such polarizationinduced phenomena with atomic resolution, but involves destructive and laborious sample preparation. SPM techniques offer powerful, non-destructive tools to effectively and conveniently probe electronic materials and devices. Since the discovery of scanning tunneling microscopy (STM) in 1981 by Binnig and Rohrer [7], the field of SPM has advanced to encompass a large number of variations including, (i) STM, (ii) Atomic force microscopy (AFM), (iii) Electrostatic force microscopy (EFM), (iv) Scanning capacitance microscopy (SCM), (v) Scanning conduction microscopy (SCM), (vi) Magnetic force microscopy (MFM), (vii) Piezoelectric force microscopy (PFM), and (vii) Near field scanning optical microscopy (NSOM). Of the above modes, the first five modes have been extensively used for semiconductor characterization [8–15]. For WBS characterization, especially III-N, AFM, EFM and SCM modes are the most important due to the strong polarization of III-N and SiC. In the latter half of this chapter, we focus on the characterization of III-N by EFM operated in

A new method for simultaneous measurement of topographic images and current-voltage (I-V) characteristics, based on atomic force microscopy (AFM), has been demonstrated with nano-scale resolution. Point-contact current-imaging atomic force microscopy (PCI-AFM) was developed to solve the incompatibility of electrically stable contact with nano-scale resolution in conductive probe AFM. We herein describe the detail of the PCI-AFM apparatus. Furthermore, the apparatus has been evaluated by the measurement of I-V characteristics of single-walled carbon nanotubes and deoxyribonucleic acid indicating high performance of PCI-AFM.

This review addresses the problem of reaction-diffusion effects and spatiotemporal oscillations in fiber-like and wire-like systems under the electron beam in SEM and in the presence of electric field in some special AFM techniques, such as current sensing atomic force microscopy (CS-AFM)/conductive atomic force microscopy (C-AFM), electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM) also known as surface potential microscopy. Some similar reaction-diffusion effects also can be observed in scanning capacitance microscopy (SCM), scanning gate microscopy (SGM), scanning voltage microscopy (SVM) and piezoresponse force microscopy (PFM). At the end of this paper the authors provide analysis of their own results and approaches. In particular, the possibility of achieving the ion transfer controlled growth of cells along the ion concentration gradients in reaction-diffusion fibers and actuators is indicated. This fundamental idea is discussed within the framework of the implantable fiber “bioiontronics” and “neuroiontronics” controlled by acoustic and electrical signals that regulate the reaction-diffusion or chemical oscillation activity of such fiber structures as reaction-diffusion actuators and sensors. The literature review includes more than 130 references.

The surface and interfaces of Si substrates covered with an alkylsilane self-assembled monolayer (SAM) were locally modified using the probe tip of an atomic force microscope (AFM) as a minute electrode. The samples were prepared by coating oxide-covered p- and n-type Si substrates with an octadecylsilyl (ODS) SAM. The chemical and electrical properties of the modified regions were characterized by lateral force microscopy (LFM), Kelvin-probe force microscopy (KFM), and scanning capacitance microscopy (SCM). At a sample bias range higher than 6 V, the ODS-SAM was degraded and the probe-modified regions became more frictional, while there were no LFM contrasts on regions probe-scanned at a lower sample bias voltage. Nevertheless, the regions showed clear KFM and SCM contrasts. Such contrasts could not be ascribed to chemical changes in the ODS-SAM, but to charge trapping and deposition in the ODS-SAM and SiO2 layer. In addition, the charge trapping behavior was found to be different depending on carrier type of the Si substrates through the SCM characterization of the modified regions. The complementary use of KFM and SCM was crucial for the electrical characterization of organic-monolayer-covered semiconductor substrates.

In this work we employ electrical scanning probe techniques to evaluate on a nanoscale the influence of semiconductor surface morphology on the electrical properties of dielectrics. Gate leakage, reliability and oxide thickness uniformity are assessed by conductive atomic force microscopy (C-AFM). Interface traps are analyzed by scanning capacitance microscopy (SCM). A correlation between nanoscale and macroscale trends is established following reverse processing of the devices. The impact of surface morphology on localized dielectric properties is evaluated by studying MOSFETs having the same silicon channel strain but different dielectric/substrate interface roughness. The correlation between surface morphology, leakage and SCM signal suggests that for dielectrics on high mobility substrates prone to surface roughening, the morphology as well as the dielectric itself play a role in the final dielectric quality. Optimized epitaxial growth will therefore enable improved device performance, reliability and variability. The results have implications for all technologies which employ relaxed SiGe templates.

Nanolithography and nanoindentation of tantalum-oxide nanowires and nanodots using scanning probe microscopy

In this paper, we present our recent applications of scanning capacitance microscopy (SCM) on specific devices with sampling window as small as 100nm. The dopant related root causes were successfully identified on those devices fabricated with 90nm CMOS technology. The key step in our approach is the development of a sample preparation technique that allows us to precisely x-section through a transistor without being affected by focused ion beam (FIB) artifacts. FIB was used to mark the area of interest with high precision, but it did not expose the devices of interest. Optical microscope and atomic force microscope (AFM) were used to inspect the mechanically polished surface, thus avoiding beam effects from FIB or SEM. In the first application, a doping anomaly was identified in a PFET poly gate, in a single bit failed SRAM cell. In the second application, an asymmetry of a PWell implant profile in a window of 150nm was identified as the cause of leakage in a capacitor array. Our approach may be applied to other scanning probe microscopy (SPM) techniques in the same category, i.e., scanning spreading resistance microscopy (SSRM) or scanning microwave microscopy (SMM).

This paper reviews some recent advances in the application of scanning probe microscopy (SPM) electrical characterization techniques to several critical surface and interface issues in SiC technology. High resolution carrier profiling capabilities in SiC of scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) were employed for several applications. These included two-dimensional (2D) imaging of doped regions in SiC devices (to be used as input for device simulations or as a feedback for device processing) and the quantitative evaluation of the electrically active profiles of P (or N) and Al implanted 4H-SiC after high temperature treatments. Furthermore, the electrical modification of the SiO2/4H-SiC interface in MOS devices subjected to post-oxide-deposition treatments in NO or N2O and POCl3 have been investigated, providing quantitative information on the electrical activation of incorporated N or P in the few-nm-thick SiC interfacial region. The lateral homogeneity of metal/SiC interfaces was probed at nanoscale by conductive atomic force microscopy (CAFM), with a special emphasis given to the case of Schottky contacts on 3C-SiC, where the diode behaviour is strongly affected by the high density of electrically active defects in the substrate. Finally, CAFM has been employed to study the current transport in epitaxial graphene (EG) grown on 4H-SiC (0001), revealing the impact of the substrate morphology (terraces and steps or facets) on the local conductivity.

The low-frequency noise in a nanometer-sized virtual memristor consisting of a contact of a conductive atomic force microscope (CAFM) probe to an yttria stabilized zirconia (YSZ) thin film deposited on a conductive substrate is investigated. YSZ is a promising material for the memristor application since it is featured by high oxygen ion mobility, and the oxygen vacancy concentration in YSZ can be controlled by varying the molar fraction of the stabilizing yttrium oxide. Due to the low diameter of the CAFM probe contact to the YSZ film (∼10 nm), we are able to measure the electric current flowing through an individual filament both in the low resistive state (LRS) and in the high resistive state (HRS) of the memristor. Probability density functions (Pdfs) and spectra of the CAFM probe current in both LRS and HRS are measured. The noise in the HRS is found to be featured by nearly the same Pdf and spectrum as the inner noise of the experimental setup. In the LRS, a flicker noise 1/fγ with γ ≈ 1.3 is observed in the low-frequency band (up to 8 kHz), which is attributed to the motion (drift/diffusion) of oxygen ions via oxygen vacancies in the filament. Activation energies of oxygen ion motion determined from the flicker noise spectra are distributed in the range of [0.52; 0.68] eV at 300 K. Knowing these values is of key importance for understanding the mechanisms of the resistive switching in YSZ based memristors as well as for the numerical simulations of memristor devices.

In order to demonstrate its unique capabilities, a combined microscope comprised of a scanning capacitance microscope and a contact mode atomic force microscope was used to image a buried structure. The atomic force microscopy images surface topography, while the scanning capacitance microscope simultaneously images buried structure. By applying a modulation technique, the voltage derivative of the capacitance (dC/dV) was used as a scanning capacitance microscope signal. The sample used for the demonstration was a silicon wafer with metal lines 4 nm in thickness covered by a 40-nm-thick layer of silicon oxide. The scanning capacitance microscope image was dependent on the bias voltage applied to the probe and the sample. Since the scanning capacitance microscope signal above the metal lines is zero, the bias voltage dependency of the contrast in scanning capacitance microscope images corresponds directly to the scanning capacitance microscope signal versus V at locations where the metal line is not buried. However, the bias dependency of the contrast did not agree with the scanning capacitance microscope signal observed between metal lines. A possible mechanism for the discrepancy between these bias dependencies is discussed based upon charge deposition on the sample surface caused by tip contact and lateral movement of the charges in the adsorbed water on the sample surface.