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In this paper we present an extended analysis of thsse impact of SiGe p-epi source/drain engineering on sub-20 nm gate length p-FinFETs performance for the N7 technology node. Different Ge concentrations and profiles (graded versus non-graded) are evaluated making use of properly calibrated drift-diffusion TCAD simulations. Calibration of simulations is based on advanced metrology and on Monte-Carlo simulations such that the resulting simulated ID-VG (in LIN and SAT regimes) matches the one measured on device. The calibrated TCAD simulator is then used to understand the limited performances of the device and to propose new source/drain epi architectures with graded and increased Ge content. A new p-FinFET design is fabricated and tested, confirming a boost in ON-current and a reduction of the parasitic resistance. Prospective TCAD work is also presented suggesting possible future improvements on p-epi source/drain and on local interconnect contacts. [ABSTRACT FROM AUTHOR]

In this paper, we illustrate how high-resolution 2-D carrier profiles from scanning spreading resistance microscopy (SSRM) can be used to predict and understand device performance of dynamic random access memory peripheral transistors with high-k metal gate and ultrashallow junctions. In an earlier study on high-speed complementary metal–oxide–semiconductor logic, the 2-D carrier profiles from SSRM were used as the active 2-D dopant profile input to the device simulator as they are virtually identical. The extensive mobile carrier diffusion caused by the lower concentrations, however, implies a strong difference between the mobile carrier distribution and the dopant distribution such that the same approach is no longer valid. Ideally one would have to generate, based on the carrier profiles, the active dopant distribution through the inverse solution of the Poisson equation (in two dimensions) which is, however, numerically nontrivial and often leads to nonunique results. Therefore, an alternative approach is proposed here, whereby we fine-tune the process simulations such that the resulting simulated carrier profiles match the 2-D SSRM profiles. Upon reaching satisfactory agreement, the simulated profiles can be used as input for a device simulator and be used to predict sensitive device parameters such as drain-induced barrier lowering and threshold voltage rolloff. [ABSTRACT FROM AUTHOR]

Metrology for structural and electrical analyses at device level has been identified as one of the major challenges to be resolved for the sub-14 nm technology nodes. In these advanced nodes, new high mobility semiconductors, such as III–V compounds, are grown in narrow trenches on a Si substrate. Probing the nature of the defects, the defect density, and the role of processing steps on the surface of such structures are prime metrology requirements. In order to enable defect analysis on a (III–V) surface, a proper sample preparation for oxide removal is of primary importance. In this work, the effectiveness of different chemical cleanings and thermal annealing procedures is investigated on both blanket InP and oxide embedded InP trenches by means of scanning probe microscopy techniques. It is found that the most effective approach is a combination of an HCl-based chemical cleaning combined with a low-temperature thermal annealing leading to an oxide free surface with atomically flat areas. Scanning tunneling microscopy (STM) has been the preferred method for such investigations on blanket films due to its intrinsic sub-nm spatial resolution. However, its application on oxide embedded structures is non-trivial. To perform STM on the trenches of interest (generally <20 nm wide), we propose a combination of non-contact atomic force microscopy and STM using the same conductive atomic force microscopy tip Our results prove that with these procedures, it is possible to perform STM in narrow InP trenches showing stacking faults and surface reconstruction. Significant differences in terms of roughness and terrace formation are also observed between the blanket and the oxide embedded InP. [ABSTRACT FROM AUTHOR]

Systematic experimental studies on phosphorus diffusion from phosphosilicate glass into the p-type bulk Si (100) substrate with different capping barrier layer thicknesses have been conducted. In both 2- and 5-nm phosphosilicate glass conditions, a thicker SiO2 cap showed a lower sheet resistance and a higher retained phosphorus dose in the Si substrate after 1050 °C 4 s rapid thermal annealing as drive-in annealing. However, the sheet resistance of 2-nm phosphosilicate glass with a 10-nm SiO2 cap was lower than that of 5-nm phosphosilicate glass with a 3-nm SiO2 cap due to a higher retained phosphorus dose in the Si substrate. For a higher retained phosphorus dose in the Si substrate using fixed total thickness, 2-nm phosphosilicate glass with 6-nm SiO2 cap is better than 5-nm phosphosilicate glass with 3-nm SiO2 cap since prevention of phosphorus out-diffusion during the drive-in annealing is more important than the total phosphorus dose in phosphosilicate glass. Next, SiO2 cap thickness on 2-nm phosphosilicate glass was split to understand the role of the SiO2 capping layer in detail for scaled devices. 3-nm SiO2 cap could not prevent out-diffusion during the drive-in annealing, and it showed much higher sheet resistance and lower retained phosphorus dose in the Si substrate. The highest retained phosphorus dose in the Si substrate was observed for 6-nm SiO2 cap and resulted in 1.8 × 1014 atoms/cm2 retained phosphorus dose with 96% activation level after 1050 °C 4 s rapid thermal annealing. Thicker SiO2 caps than 6 nm were not beneficial since 10-nm SiO2 cap showed a higher sheet resistance value as well as lower phosphorus activation level (82%) compared to 6-nm SiO2 cap even though both the process conditions showed same phosphorus profiles after the drive-in annealing. That sheet resistance increase with 10-nm SiO2 cap could be caused by heterogeneous surface formation on the Si substrate with a prolonged SiO2 atomic layer deposition process. [ABSTRACT FROM AUTHOR]

The cover art of this issue of "Physica Status Solidi C" is presented.

Lists the reviewers who contributed to IEEE Transactions on Electron Devices in 2011. [ABSTRACT FROM AUTHOR]

Within this paper, the authors propose a refined high vacuum scanning spreading resistance microscopy (HV-SSRM) electromechanical nanocontact model based on experimental results as well as molecular dynamics (MD) simulation results. The formation under the tip of a nanometer-sized pocket of β-tin, a metastable metalliclike phase of silicon (also named Si-II), acting as a virtual probe is demonstrated. This gives a reasonable explanation for the superior SSRM spatial resolution as well as for the electrical properties at the Schottky-like SSRM contact. Moreover, the impact of the doping concentration on the plastic deformation of silicon for different species using micro-Raman combined with indentation experiments is studied. In order to elucidate the superior results of SSRM measurements when performed under high vacuum conditions, the impact of humidity on the mechanical deformation and Si-II formation is also analyzed using MD and SSRM experimental results. [ABSTRACT FROM AUTHOR]

In order to reach the ITRS goals for future complementary metal-oxide semiconductor technologies, there is a growing need for the accurate extraction of ultrashallow electrically active dopant (carrier) profiles. In this work, it will be illustrated that this need can be met by the micro four-point probe (M4PP) tool. M4PP sheet resistance measurements taken along beveled Si and Ge blanket shallow structures will be investigated. From the differential sheet resistance changes, the underlying carrier profile can be reconstructed without the need to rely on a complicated contact modeling, i.e., M4PP carrier profiling is an absolute carrier depth profiling technique. On Si, it is found that the more sensitive a structure is to carrier spilling along the bevel, the better the M4PP system performs relative to conventional spreading resistance probe (SRP) due to its much lower probe pressure in combination with its sensitivity to what happens around the probes (and not underneath them). Also for Ge, the same issues change significantly the apparent carrier spilling behavior and improve the final accuracy obtained relative to SRP. [ABSTRACT FROM AUTHOR]

In this work, the authors investigate the present capabilities of scanning spreading resistance microscopy (SSRM) to map the carrier distribution in fin field-effect-transistor- (FinFET) based structures. Whereas for a planar metal-oxide-semiconductor transistor the distance to the back-contact is noncritical, this no longer holds true for a FinFET-based device as the limited cross-section of the fin may induce an important series resistance. The authors examine theoretically and experimentally the influence of the back-contact distance and the fin dimensions on the dominance of the spreading resistance. Based on the study, the authors propose a maximum distance for the back-contact that is needed to obtain a reliable two-dimensional map of the spreading resistance of fins with uniform doping concentration and fins with junction using SSRM. As the back-contacts are FIB deposited, the authors also study the influence of the Ga+ beam energy on the back-contact resistance, which adds critically to the bulk resistance of the fin, giving rise to a higher total resistance. Finally, the authors compare the fin dimensions obtained with SSRM and transmission electron microscopy micrograph. [ABSTRACT FROM AUTHOR]

When comparing the extracted carrier mobility of long- and short-channel transistors, special consideration must be given to the metallurgical gate length (Lmet), neglecting the impact of source and drain junction profiles. Lmet can be identified with nanometer precision by using RF split-C–V measurements, and physical and electrical analysis can demonstrate the accuracy of the method. Another important parameter, the external transistor resistance (Red), can be identified with linear current measurements of short-channel devices. However, it is important to quantify the mobility dependence from the gate length in order to obtain an accurate result. A method to estimate the electrical field (Eeff) of short-channel devices is proposed. The extracted short-channel mobility shows a universal behavior identical to the classical long-channel one. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate the consequences of extension junction formation by low-temperature solid-phase-epitaxial-regrowth in nMOS transistors. Atomistic simulations, experimental device results, sheet resistance, and scanning spreading resistance microscopy data indicate that the high concentration of silicon interstitials associated with the end-of-range defect band promote the local formation of boron-interstitial clusters, and thus deactivate boron in the pocket and channel. These inactive clusters will dissolve after the high concentration silicon interstitial region of the end-of-range defect band has been annihilated. This nMOS requirement is in direct opposition to the pMOS case where avoidance of defect band dissolution is desired, to prevent deactivation of the high concentration boron extension profile. [ABSTRACT FROM AUTHOR]

A new atomic force microscopy (AFM)-based technique named fast Fourier transform scanning spreading-resistance microscopy (FFT-SSRM) has been developed. FFT-SSRM offers the ability to isolate the local spreading resistance (Sr) from the parasitic series resistance (probe, bulk, and back contact). The parasitic series resistance limits the use of classical SSRM in confined volumes and on very highly doped materials, two increasingly important situations in nanoelectronic components. This is realized via a force modulation at controlled frequency (affecting the SR component) and the extraction of the resistance amplitude at the modulation frequency, performing an FFT-based lock-in deconvolution. A systematic evaluation of the FFT-SSRM performances (i.e., resolution, dynamic range, sensitivity, and repeatability) is presented. The impact of various parameters (i.e., modulation frequency and amplitude or cutoff frequency of the current amplifier) on the performances of FFT-SSRM has been evaluated. We demonstrate the possibility to overcome sensitivity losses due to tip saturation in highly doped material and the utility of the technique in two different structures, presenting isolated and confined volumes. [ABSTRACT FROM AUTHOR]

Photoreflectance (PR) provides an optical means for rapid and precise measurement of near-surface electric fields in semiconductor materials. This article details the use of PR to characterize dopant activation in ultrashallow junction (USJ) structures formed using millisecond annealing processes. USJ structures were formed in silicon using 500 eV B implantation with a dose of 1015/cm2, followed by flash anneals at 1250–1350 °C. Reference metrology was performed using secondary ion mass spectrometry and various sheet resistance (Rs) methods. Methods to calibrate PR signals to active carrier concentration in USJ structures, including halo-doped samples, are described. PR is shown to be highly sensitive to active dopant concentrations in USJ structures formed by millisecond annealing. [ABSTRACT FROM AUTHOR]

With emerging three-dimensional device architectures for advanced silicon devices such as fin field-effect-transistors (FinFETs), new metrology challenges are faced to characterize dopants. The ratio of dopant concentration in the top surface and sidewalls of FinFETs may differ significantly, thereby influencing the performance of these devices. In this work, a methodology involving secondary ion mass spectrometry (SIMS) is presented to study the dose conformality in fins. However, SIMS is limited to probe the quantitative chemical dopant concentration (i.e., top/sidewall of fins). The fraction of the active dopant concentration determining the performance of FinFETs would still be unknown. Additionally, the concept based on SIMS is unable to provide information on the lateral junction depth. Thus, to obtain the unknown active dopant concentration and their spatial distribution, the authors extend their study by measuring the cross section of the fins with scanning spreading resistance microscopy and extracting the quantitative active carrier concentration in the fins. [ABSTRACT FROM AUTHOR]