In this study, titanium carbonitride (TiCN) coatings are obtained by atmospheric plasma spray synthesis, or reactive plasma spraying. In order to promote reactions between Ti particles and reactive gases, an extended gas tunnel was mounted at the end of a conventional plasma gun. The oxidation behavior of the TiCN coatings was investigated over a wide temperature range, showing that the coatings suffered severe oxidation at temperatures above 700 °C and were entirely oxidized to the TiO 2 phase at 1100 °C. The principal oxidation mechanism was revealed, indicating that oxygen can penetrate into the TiCN coatings at high temperatures. Changes in microhardness were also investigated as a function of temperature, showing a precipitous drop over the range of 700-1100 °C.

In the present study, Fe-Al 2 O 3 -FeAl 2 O 4 and FeAl coatings were synthesized in situ by reactive plasma spraying of Al-Fe 2 O 3 composite powder under atmosphere and low-pressure conditions. Coating microstructure and phase composition are examined and coating formation mechanisms are discussed. It was found that FeAl 2 O 4 hercynite phase is always synthesized as an intermediate product under low oxygen partial pressure conditions. In the APS process, such a phase can be retained in the final coating by extremely fast cooling. It can also be continuously reduced to FeAl by deoxidation in an oxygen-free H/H 2 atmosphere.

Yttria-stabilized zirconia (YSZ) coatings have been frequently used as a thermal protective layer on the metal or alloy component surfaces. In the present study, ZrO 2 -7%Y 2 O 3 thermal barrier coatings (TBCs) were successfully deposited by DC (direct current) plasma spray process under very low pressure condition (less than 1 mbar) using low-energy plasma guns F4-VB and F100. The experiments were performed to evaluate the thermal shock resistance of the different TBC specimens which were heated to 1373 K at a high-temperature cycling furnace and held for 0.5 h, followed by air cooling under room temperature during 0.2 h. For comparison, the corresponding APS counterparts were also elaborated to carry out the similar experiments. The results indicated that the VLPPS coatings displayed better thermal shock resistance. Moreover, the failure mechanism of the coatings was also elucidated.

In recent years, the production of coatings obtained by LPPS process (Low Pressure Plasma Spraying) was successfully introduced in industrial markets for aerospace, gas turbines, medical and other special applications. The deposition of coatings with superior properties requires an improved understanding of this complex spray process, including the inflight particle temperature and velocity. In this study, DPV- 2000 (Tecnar, St-Bruno, QC, CA) was employed to characterize the LPPS process at different operational pressure ranges from typically 250 mbar to 150 mbar. Measurements of the temperatures and velocities of the in-flight yttria-stabilized zirconia (YSZ) particles were carried out in an argon– hydrogen plasma jet. The YSZ coatings were also deposited in accordance with different operating parameters. The microstructures of the coatings were analyzed by SEM.

With the purpose of elaborating high-quality FeAl coatings, a so-called very low pressure reactive plasma spray technique that combines VLPPS and SHS processes was used in the present study. A dense and homogeneous FeAl coating was thus successfully in situ synthesized by reactive plasma spraying of an Al/Fe 2 O 3 composite powder under 1 mbar. The phase composition and microstructural features of the coating were characterized by XRD and SEM. Results indicated that the B2 ordered FeAl phase was synthesized, and the coating featured a dense and defect-free microstructure. The fracture mechanism of the coating remains mainly a brittle failure but the appearance of some dimples in local zones suggests some unexpected toughness.

Very low pressure plasma spraying has been intensively studied in recent years especially the properties of plasma jet. These properties are affected by plasma generating and working conditions. These operating parameters such as arc power, plasma gas flow rate and chamber pressure have influences on specific enthalpy and temperature of plasma jet. In this work, the measurements under very low pressure were performed using enthalpy probe which was previously modified (increase of the internal diameter and depositing TBC coating (Ni/Al and ZrO 2 + Y 2 O 3 ) on the head). Different parameters, for instance, current intensity, hydrogen gas flow rate and detecting distance were changed in order to point out their effect on the characteristics of plasma jet. The specific enthalpy, temperature and quantity of heat in this situation were obtained.

As a promising thermal spray technology, the very low pressure plasma spray (VLPPS) process has been significantly used to deposit thin, dense and homogenous ceramic coating materials for special application needs in recent years. In this study, a home-made transferred arc nozzle was mounted on a low power F100 plasma torch for enhancing the plasma jet energy under very low pressure conditions. Thin and dense alumina (Al 2 O 3 ) and yttria-stabilized zirconia (YSZ) ceramic coatings with an average thickness of 30-40 µm were successfully elaborated by VLPPS process below 1 mbar. Optical emission spectroscopy (OES) was used to analyze the properties of the plasma jet with or without powder injection. The microstructures of the coatings were observed by means of scanning electron microscopy (SEM). It was found that the YSZ coatings displayed a bimodal microstructure that was composed of splats formed by melted particles and a little amount of vapor condensation from evaporated particles. However, vapor condensation could not be observed in the Al 2 O 3 coatings formed by lamellar splats only. The Vickers microhardnesses of both coatings were also evaluated.

Electrical Test (ET) structures are used to monitor the health and yield of a process line. With the scaling down of semiconductor devices to nanometer ranges, the number of metal lines and vias increase. In order to simulate the electrical performance of devices and to increase the sensitivity for line health check, ET structures are designed to be more complicated with a larger area. Hence, fault isolation and failure analysis become more challenging. In this paper, the combined technique of Scanning Electron Microscope (SEM) Passive Voltage Contrast (PVC), Nanoprobing technique, and Divide and Conquer Method (DCM) are proposed to locate open failure and high resistance failure in an ET via chain.

Cu coatings were obtained by the VLPPS (Very Low Pressure Plasma Spray) process using a torch F4-VB. The tank pressure was varied from 1 mbar to 5 mbar: these specific conditions can allow obtaining a higher vapor condensation fraction in the coating. Different sizes of powders are used to compare the vaporization level. The other possible influencing factors for obtaining compact film-like coating are also considered such as the distance between the torch and substrate, the orientation of the vapors and also the substrate temperatures. Microstructures of coatings are analyzed and combined with the results of plasma diagnostics. Jobin-Yvon spectrometer (type TRIAX190, UK) and Plasus Specline Spectroscopy software are both used for detecting and analyzing plasma spectrum data. The value of plasma electronic excited temperature Te was calculated through choosing Hα and Hβ two atom spectra. The results showed that the plasma belongs to cold plasma in the local thermodynamic equilibrium situation in VLPPS.

The scanning electron microscope (SEM) based nanoprobing technique has established itself as an indispensable failure analysis (FA) technique as technology nodes continue to shrink according to Moore's Law. Although it has its share of disadvantages, SEM-based nanoprobing is often preferred because of its advantages over other FA techniques such as focused ion beam in fault isolation. This paper presents the effectiveness of the nanoprobing technique in isolating nanoscale defects in three different cases in sub-100 nm devices: soft-fail defect caused by asymmetrical nickel silicide (NiSi) formation, hard-fail defect caused by abnormal NiSi formation leading to contact-poly short, and isolation of resistive contact in a large electrical test structure. Results suggest that the SEM based nanoprobing technique is particularly useful in identifying causes of soft-fails and plays a very important role in investigating the cause of hard-fails and improving device yield.

Electrical characterizations were needed to identify the root cause of leakage issues in IC devices. The methodology required was dependent on the failure mode obtained during testing and global or nano-scale isolations had to be implemented accordingly. As such, challenges encountered in sample preparation or due to detection methodology choices for every isolation technique have to be addressed in order to localize the defective sites.

With the scaling down of semiconductor devices to nanometer range, physical failure analysis (PFA) has become more challenging. In this paper, a different method of performing PFA to identify a physical vertical short of intermetal layer in nanoscale devices is discussed. The proposed chemical etch and backside chemical etch PFA techniques have the advantages of sample preparation evenness and efficiency compared to conventional PFA. This technique also offers a better understanding of the failure mechanism and is easier to execute in identifying the vertical short issue.