Hard functional and logic failures which are insensitive to temperature, voltage, or frequency have become increasingly difficult to debug in advanced technology nodes, especially when Photon Emission (PEM) analysis could not provide any leads and Dynamic Laser Stimulation (DLS) could not be used due to the nature of the failure (no pass/fail margin). Laser Voltage Imaging (LVI), which is an extension of the Laser Voltage Probing (LVP) technique, provides a visual map of active components that are toggling at a certain frequency. This technique is widely employed in scan chain debug due to its simplicity, efficiency, and accuracy. However, most of LVI applications in literature reviews only involve scan chain fault isolation. This paper will present alternative applications for LVI, apart from scan chain debug. One specific application is the debug of a broken signal path by sending a periodic signal as a stimulus to a GPIO pad and tracing the LVI signal through the path by frequency mapping. In this paper, the concept and methodology behind this fault isolation approach will be discussed in full detail. Furthermore, three case studies of different types of hard failures with different applications of LVI will also be presented: an IO functional failure, an ATPG (Automatic test pattern generation) SAF (Stuck At Fault) failure and a BSDL(Boundary scan description language) input interconnect failure, to illustrate how LVI could be deployed in fault isolation for those functional and logic hard failures.

Photon Emission Microscopy (PEM) analysis is one of the most common used FA techniques to identify the root cause of failures within ATPG scan logic due to its ease of setup and less invasive nature. While conducting photon emissions, the device is made to operate in the fail mode by running a production test vector to look for anomalous emissions or hot spots that could narrow down the area of interest (AOI) for subsequent Physical Failure Analysis (PFA). However, if there is no clue from emission analysis in the case of a hard failure with no sensitivity to voltage, frequency, or temperature, FA debug will be challenging. This paper shows how PEM analysis success may be further improved through logic state circuit study using a DFT ATPG diagnostic platform. Logic state truth table and its relative test pattern will be built based on the diagnostic data using in-house scripts, and the test program can then be changed to the required condition of the circuitry. With the altered logic state, new emission data can be collected, which could potentially reveal new clues to the investigation.

The aim of this study is to determine how feedstock shape affects deposition efficiency and coating formation in cold spraying. Spherical and irregular-shaped Cu powders were sprayed on Al substrates at gas temperatures ranging from 100 to 650 °C. Rebound particles were collected and examined and various coating qualities were assessed, including deposition efficiency, hardness, stack morphology, and adhesion strength. In order to explain certain discrepancies between predicted and measured data, as-sprayed and heat-treated coatings were compared and powder hardness was analyzed in detail. Contrary to simple theoretical hydrodynamic simulations, the critical threshold velocity for irregular particles was higher than that of the spherical ones. The results and practical implications of the study are discussed in the paper.

This work investigates the effect of feedstock size on the hardness and wear resistance of metal-matrix composite coatings produced by cold spraying. Feedstocks consisting of Al and Al 2 O 3 powders were prepared for the study. The feedstocks, which differ in regard to Al 2 O 3 particle size (100, 50, 10 µm) and composition (25-50 vol%), were accelerated by compressed air through a Delaval-type nozzle positioned 10 mm from the target substrate. The morphology of the coating resembled that of an Al matrix with embedded Al 2 O 3 particles. Optical microscopy showed that large Al 2 O 3 particles (> 50 µm) fractured into small pieces and embedded in the matrix. It is likely that some of the fragmented particles bounced off, rather than adhering. These collisions (tamping effect) increase coating hardness and density. In the case of the feedstock with 10 µm Al 2 O 3 , particle sizes were unchanged during spraying and the benefits of work hardening were not achieved.

This study investigates the effects of various reinforcement materials and solid lubricants on cold spray aluminum composite coatings. The wear resistance and friction coefficient of the coatings were very different with and without a reinforcement and solid lubricant. It was found that Al 2 O 3 greatly improves wear properties, Mo results in better dispersion hardening, and MoS 2 reduces the friction coefficient.

It is well known that the inlet temperature of the spray gas influences the impact velocity of particles which, in turn, affects the mechanical and chemical properties of the final coating. From cold spray of high- and-low-melting-point feedstock such as Cu-Sn, it was found that those effects can vary with changes in particle shape and size. Copper powder feedstocks with different shapes, such as and dendritic (under 25 μm), were selected for analysis. For spherical (under 10 μm) powders of Cu 6 Sn 5 , an intermetallic compound (IMC) of Cu-Sn was formed in the as-coated state at and above gas inlet temperatures of 100 °C. for A gas inlet temperature of at least 300 °C was needed for the dendritic Cu powders. As temperatures increase, another IMC, Cu3Sn, was also formed. The onset temperature for the formation of the additional IMC was 450 °C for both shapes. Below 300 °C, both Cu and Sn were in solid state and thermodynamic driving forces were drawn from impact energy. Therefore, the spherical particles had more stored energy (strains) than the dendritic particles to initiate IMC formation.

Cu-Sn composites coatings by cold spray with wide ranges of particle size and shape (round to flake) were investigated regarding their intermetallic compound (IMC) formation. It was found when certain size and shape combination of Cu-Sn composite raw materials were employed, the embedded Cu-Sn IMCs such as Cu 6 Sn 5 and Cu 3 Sn were observed even in as-sprayed states without additional heat treatments. These results implied that the impact energy of colliding particles of the cold spraying could be enough to activate IMC compounding process. It seems that this can be also true in several composite systems that have relatively low activation energy of IMC compounding. After post annealing, the Cu 6 Sn 5 formed in as-coated state were transformed into the Cu 3 Sn phase and the residue of unreacted Sn particles were fully changed into the Cu 3 Sn phase (Cu 6 Sn 5 →Cu 3 Sn). These conversion processes also depended strongly on the choices of the shape and size combinations of Cu and Sn particles.

Comparative studies on the intermetallic compound (IMC) formations of nano- and micro-size Sn with Ni and Cu in cold gas dynamic sprayed (CGDS, or Cold Spray) coatings were carried out. High purity pure nano (average 150 nm) and micro (under 45 μm) Sn were selected and prepared as raw materials mixture in order to be sprayed onto Ni and Cu plate-shape substrates. Nano particles of Sn were successfully coated under conventional coating parameters when they are mixed with microsize materials. And thermodynamic predictions regards to compound formation similarly worked out for both nano and micro Sn mixture. However, the kinetics of formation reaction were turned out to be different. In all case, nano particle showed more sluggish behavior. After post-annealing, microsize Sn formed larger amount of IMC with Ni than nanosize Sn although, owing to larger interfacial area, more intensive reactivities were expected. Also, there were significant differences in the size and distribution of eutectic pores as well.

Post-annealing of cold spray coatings has great potential for wear applications because it produces intermetallic compounds at low temperature far below equilibrium. This study investigates the effects of spraying pressure on the intermetallics formed and their dispersion characteristics. In the experiments, Al and Al-Ni powders were sprayed on Ni and Al substrates at 0.7, 1.5, and 2.5 MPa and a portion of the coating samples were annealed in argon at 500, 550, and 600 °C. Detailed examinations showed that Al particles are subject to peening effects that can interfere with the formation of intermetallic compounds during annealing, but that the effects can be mitigated by controlling gas pressure. Spraying pressure was also found to have an effect on the formation of eutectic pores in Al-Ni composite coatings, with higher pressures corresponding to fewer pores.

Titania (TiO 2 ) coatings were produced using the high velocity oxy-fuel (HVOF) technique on Ti-6Al-4V substrates. The titania feedstock powder exhibited nanostructured morphology, formed by the agglomeration of individual nanostructured titania particles (spray-drying) smaller than 100 nm. The resulting coatings were dense (porosity <1%) and exhibited rutile and anatase as phases with percentages of ~75% and ~25%, respectively. These coatings were heat-treated in a H 2 /N 2 environment at 700oC for 8 h. During the heat-treatment, nanostructured titania fibers were formed on specific surface regions of the coatings. The nanofibers formed by this “chemical or reaction-based texturing” exhibited diameters of 50-400 nm and lengths in the order to 1-5 µm. It is thought that engineering these surfaces at nano and microscales may lead to interesting applications of titania coatings related to cell attachment/growth (for biomedical applications).

This paper describes gate oxide defect localization and analysis using passive voltage contrast (PVC) and conductive atomic force microscopy (C-AFM) in a real product through two case studies. In this paper, 10% wt KOH was used to etch poly-Si and expose gate oxide. In the case studies, different types of gate oxide defects will cause different leakage paths. According to the I-V curve measured by C-AFM, we can distinguish between short mode and gate oxide related leakage. For gate oxide leakage, KOH wet etching was successfully used to identify the gate oxide pinholes.

Modern semiconductor devices are continuing to be scaled down and the complexity of the processes involved in producing the devices keeps increasing, in conjunction with this, sample preparation and analysis are increasingly important for accurately determining the sources of defects and failure mechanisms in terms of process integration. This paper discusses ways to characterize integration-driven defects using deprocessing techniques and cross-section imaging to obtain 3-D views of such defects. As an example a single-via test structure is evaluated. The article focuses on the techniques used to deprocess the single-via structure using a combination of RIE, FIB, and wet etching to expose the single via while maintaining the integrity of the structure. The resulting 3-D view of the structure and associated defect allowed for improved understanding of the defect and its origin. This understanding enabled process optimization to minimize such defect formation.

As DRAM technology extends into 12-inch diameter wafer processing, plasma-induced wafer charging is a serious problem in DRAM volume manufacture. There are currently no comprehensive reports on the potential impact of plasma damage on high density DRAM reliability. In this paper, the possible effects of floating potential at the source/drain junction of cell transistor during high-field charge injection are reported, and regarded as high-priority issues to further understand charging damage during the metal pad etching. The degradation of block edge dynamic retention time during high temperature stress, not consistent with typical reliability degradation model, is analyzed. Additionally, in order to meet the satisfactory reliability level in volume manufacture of high density DRAM technology, the paper provides the guidelines with respect to plasma damage. Unlike conventional model as gate antenna effect, the cell junction damage by the exposure of dummy BL pad to plasma, was revealed as root cause.

With the advancement in technology and lower operating voltage, new standards have evolved in circuit layout and design. Some of these new standards have increased the difficulties of the physical failure analysis process, especially on the front-end. The phenomenon described in this paper is the unusual voltage contrast (VC) and conductive atomic force microscope (C-AFM) curve on a non-isolated active region. The model and mechanism are demonstrated for front-end failure analysis. Based on this, the solution for analysis is investigated.

Three different oxides of CrO 2 -TiO 2 , Al 2 O 3 and Al 2 O 3 -TiO 2 were plasma-sprayed on Ti substrate to evaluate the crystal structure and the corrosion properties of the coatings. No phase change of the coatings after corrosion test in 0.5 M H 2 SO 4 solution at 25°C was found regardless of the presence of the NiCoCrAlY bond layer. Electrochemical measurements and SEM results revealed that the single coatings without the bond layer were always effective against corrosion resistance due to lower current density within the passive region. Pitting corrosion of the surface was observed for the Al 2 O 3 coating. It can be concluded that the Al 2 O 3 -TiO 2 coating without the bond layer may be the best oxide among the oxides investigated due to low porosity (5.4%), smooth surface roughness (4.5 m), low current density (6.3×10-8 A/cm 2 ) in the passive region, low corrosion potential (Ecorr, -0.55 V) and no pitting corrosion.

Scanning electron beams provide a superior method of failure analysis by observing the voltage contrast (VC) both in frontend and back-end processes. Back-end VC tells us both metal/via open/short issues. Front-end VC tells us not only open/short issue but also additional doping information. A case on the application of passive voltage contrast (PVC) on doping information was studied. This paper explains the mechanism producing passive voltage contrast and describes three methods of sample preparation and provides examples of the results achieved.

The Thermal Barrier Coating (TBC) used to improve the heat barrier and wear resistant property in high temperature of the aircraft engine and the automobile engine, usually has a two layer structure. One is a ceramic top layer for heat insulation and the other is a metal bond layer to facilitate the bond strength between the top ceramic layer and the substrate. But, the coated layers can be peeled off because of the accumulation of the thermal stress by the difference of the thermal expansion coefficient between metal and ceramics in a heat cyclic environment. In this study, the intermediate layer produced by plasma spray process was introduced to reduce the thermal stress. The powders of plasma spray coating were Yttria Stabilized Zirconia (YSZ), Magnesia Stabilized Zirconia (MSZ) and NiCrAIY. The intermediate layer was sprayed with the powders of partially stabilized zirconia with 50wt% NiCrAIY between the ceramics top coat and the bond coat for the purpose of alleviating heat expansion. The high temperature wear and thermal shock test were conducted. The high temperature wear resistance of the YSZ TBC was better than that of the MSZ TBC. The wear resistance decreased with increasing temperature between 400°C to 600°C. The 3 layers TBC with YSZ top coating showed the best thermal shock resistance. This means that the intermediate layer played an important roll to alleviate the difference of the thermal expansion between metallic layer and ceramics layer. SEM and OM were examined. The bond strength, hardness test, and wear test were also studied.