bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Dependence of Defect Evolution and Distribution in Thermally Cycled Cu-TSVs
Authors: Marro James Brandon , Okoro Chukwudi A , Obeng Yaw S. , Richardson Kathleen A , Chamma Karima 
Published: February 2020

Through-silicon vias (TSV) are copper (Cu) interconnects used in three dimensional integrated circuits (3D-IC) and other packaging to allow inter-chip communication. A thermo-mechanical reliability concern for Cu-TSVs, are the formation of voids, which are indicative of the stresses undergone by the structures. Voids can degrade signal propagation by acting as scattering centers and if large enough, can prevent the passage of current [1]. Simulations of fabrication conditions such as back-end-of-the-line (BEOL) addition, have been conducted by isothermal heating or minimal cycling [2-4]; however, few studies have focused on in-use conditions where chips undergo many cycles at lower temperatures, simulating environmental changes and joule heating from use. This study replicates these in-use conditions to evaluate defect evolution and distribution in thermally cycled Cu-TSVs. Silicon (Si) chips containing blind Cu-TSVs were cycled 2000 times from room temperature to maximum cycling temperatures of 100 °C, 150 °C, or 200 °C. Residual voiding from fabrication was considered by examining two sample types (shown in Fig. 1), specimens that contained Cu-TSVs with seams and large bottom voids and those that exhibited only microvoids. The S11 parameter was measured at 500 cycle increments and determined signal loss trended with maximum cycling temperature and initial void area, but not with number of cycles. To further investigate void development, the TSVs were cross-sectioned for internal evaluation using a combination of grinding, polishing, and ion beam milling. Voids were then studied using focus ion beam (FIB) and scanning electron microscope (SEM) images to record void dimensions and locations within the Cu of the TSVs. Void area was observed to increase with increasing maximum cycling temperature from 100 °C to 200 °C, however, this increase is a result of void nucleation as opposed to pre-existing void growth. While rapid cycling (~5 min/cycle) under in-use conditions for these Cu-TSVs did not allow diffusion and growth of voids, maximum cycling temperatures provided sufficient driving force for stresses to form new voids in the Cu.
Fig. 1: SEM micrographs of the TSV cross-sections for the two as-received sample types: (a) containing seams and large bottom voids and (b) solely containing microvoids.
References:
1. J. Kim, J. Cho, J. S. Pak, J. Kim, J. Yook, and J. C. Kim, Electrical Performance of Electronic Packaging and Systems (EPEPS), 2011 IEEE 20th Conference on 243-246 (2011).
2. H. Shin, B. Kim, J. Kim, S. Hwang, A. Budiman, H. Son, K. Byun, N. Tamura, M. Kunz, D. Kim and Y. Joo, Journal of Electronic Materials, 41 [4] 712-719 (2012).
3. L. W. Kong, J. R. Lloyd, K. B. Yeap, E. Zschech, A. Rudack, M. Liehr and A. Diebold, Journal of Applied Physics, 110 [5] 053502 (2011).
4. L. Kong, A. C. Rudack, P. Krueger, E. Zschech, S. Arkalgud and A. C. Diebold, Microelectronic Engineering, 92 [0] 24-28 (2012).
Current Status of Slurries and Cleans for CMP of III-V Device Fabrications – a Critical Review
Authors: Banerjee Gautam 
Published: February 2020

With the growth of cloud computing market, the need for logic and memory chips for data centers have been steadily growing which require low power and high performance. Another area of growing semiconductor application is mobile products which require increasingly higher performance without sacrificing power. The above two requirements can only be achieved by scaling supply voltage(Vdd).
III-V materials enable Vdd scaling to address power without sacrificing performance due to the very high electron injection velocity at virtual source compared to Si. For example,
Vinj

(InGaAs) > 2
Vinj

(Si) at less than half VDD.

The development at Intel on InGaAs and at IMEC on Ge based FinFET structures have made it possible to conceive the integration scheme such as depicted in http://www.compoundsemiconductor.net/csc/features-details/19732136/Uniting-III-Vs-and-germanium-for-CMO.html .
In order to enable such CMOS fabrication, development of CMP slurry, post CMP clean and modification of the presently available process tools need to be done. While new slurries and cleans will be needed to planarize III-V film layer(s) without compromising the film composition (and functionality), modification of the process tool will be needed to address potential release of toxic waste water into the the waste stream after planarization.
At this time, published results show some academic works in addressing various issues related to CMP of III-V materials but there are not many reports in the public domain from the industry to address the need which is essential to successfully integrate CMP as an enabling step in the manufacturing of III-V CMOS devices.
In this paper, the status of development of CMP processes, slurries and post CMP cleans will be reviewed and the critical needs to enable for the future III-V device integration will be analyzed.
(Invited) Study of Carrier Localization, Carrier Transportation and Carrier Recombination Processes in Blue-Emitting InGaN/GaN MQWs
Authors: Li Cheng , Stokes E. B. , Armour Eric A 
Published: February 2020

InGaN/GaN MQWs grown on c-plane sapphire substrate show high internal quantum efficiency, regardless of their high threading dislocation density (108 cm-2~ 1010 cm-2) that is introduced by lattice mismatch. This high-IQE phenomenon is attributed to bandgap energy fluctuation and carrier localization in the QW layer [1].
In the present work, temperature-dependent PL, confocal microscopy, and nanometer-scale time-resolved photoluminescence (TRPL) spectroscopy were employed to analyze the carrier localization, carrier transportation and carrier recombination processes in blue-emitting InGaN/GaN MQWs.
The temperature-dependent PL spectra were taken from 10 K to 300 K. The decreased spectrum-integrated PL intensity with increasing temperature was observed, which was fitted with second-order Arrhenius equation, as shown in Fig. 1. The fitting indicated two non-radiative channels: the one with high activation energy (dominated at high temperature) corresponded to thermal activation of carriers out of the strongly localized states, while the one with low activation energy (dominated at low temperature) corresponded to thermal activation of carriers out of the weakly localized states. The S-shaped shift of PL peak energy and the inverse S-shaped shift of PL FWHM were also observed, as shown in Fig. 2 and Fig. 3, which were explained with carrier localization and carrier dynamics.
The confocal microscope image collecting near bandedge emission showed inhomogeneous PL intensity distribution, as shown in Fig. 4. Previous analysis [2] has shown that the bright region had smaller bandgap energy than dark region did. Nanometer-scale TRPL spectra were taken at different places in the confocal microscope image. As shown in Fig. 5, TRPL spectra taken at the center of bright region and the center of dark region show single exponential decay, which are characterized by a single lifetime and corresponds to carrier localization in strongly localized state and weakly localized state, respectively. Comparing with bright region, dark region has shorter lifetime, indicating a higher probability of nonradiative recombination and carrier transportation from dark region to bright region. TRPL spectrum taken at the boundary of bright region, however, shows double exponential decay, as shown in Fig. 5, which is characterized by two lifetimes. The short lifetime corresponds to carrier transportation from weakly localized state to strongly localized states, while the long lifetime corresponds to carrier recombination at local strongly localized state.
References:
1. R. A. Oliver, et al., Journal of Physics D-Applied Physics, 43, 35 (2010)
2. C. Li, et al., ECS Journal of Solid State Science and Technology, 2, 11 (2013)
Photo-Electroless-Etching of Wide Band Gap Material for Flexible Solid-State Devices
Authors: Slimane Ahmed B , Ng Tien K , Ooi Boon S 
Published: February 2020

We report on photo electroless chemical (PEC) etching of III-Nitride material for thin layer lift-off for flexible solid-state light emitting devices. We investigate three different structures: 30 µm unintentionally doped GaN on sapphire, 30 µm n-type GaN on sapphire, and 200 nm InGaN on 4 µm unintentionally doped GaN on sapphire with different indium composition. Initially the three structures were etched as-grown for the same duration and the same conditions in a HF/CH3OH/H2O2 solution under UV illumination. Scanning electron microscopy (SEM) measurements performed on the etched samples reveals porous structure and high density nanowire on the surface, as well as the formation of V-shaped pits. The etch rate in each structure were compared. Optical study were performed using photoluminescence (PL) and Raman spectroscopies to analyze PL peak shift and phonon frequency shift compared to the as-grown, which we attributed to the compressive strain relaxation and localized impurity formed in the crystalline structure after PEC etching. We also fabricated microcolumns of diameters ranging from 5 to 100-µm via inductively coupled plasma (ICP) etching process in the InGaN on GaN samples. Dry etching of micropillars exposes unintentionally doped GaN to the wet etching. We study the selectivity of GaN over InGaN in the PEC etching process. SEM images reveal lateral etching and porous GaN layer formation under the InGaN after wet etching. We compare etching process in the InGaN structure with and without microcolumns. PEC etching is sensitive to band bending in the surface of the semiconductor and electrolyte, when InGaN surface is in contact with HF solution, oxidation and reduction reaction happens at slow rate and leads to the porous structure in the surface. However, when the GaN under the InGaN is exposed, the etching in this layer is preferred due to the low resistivity and the confinement of the photogenerated minority in the upward band bending depleted region near the contact surface between GaN and electrolyte.
Undercut InGaN microdisks were lifted off for optical study via flexible polydimethylsiloxane (PDMS) material. Microdisks were then transferred on to a Si wafer for PL measurements. We also performed Raman study on the microdisks and observed a shift in the phonon frequency attributed to the relaxation of the compressive strain with respect to the as-grown. InGaN microdisks with higher indium composition were transferred on a blue LED for optical pumping. Optical measurements on transferred microdisks revealed typical prominent visible peaks. These observations confirm the promising application of this technique to selectively etch III-V semiconductor. The lift-off process is a compelling technique for next generation transferred substrate devices and III-Nitride micro phosphor fabrication.
(Invited) Carbon Nanotube Based Photonics
Authors: Noury Adrien , Le Roux Xavier , Gaufrès Etienne , Vivien Laurent , Izard Nicolas 
Published: February 2020

The use of optics in microelectronic circuits to overcome the limitation of metallic interconnects is more and more considered as a viable solution. Numerous photonic building blocks, compatible with CMOS technology, have been developed. However, integration of all these building blocks on the same chip is a bottleneck, due to the various materials used (Ge, Si, III-V). This drawback could be significantly overcome by considering carbon nanotubes, which have the ability to emit, modulate and detect light in the wavelength range of silicon transparency. That makes them a promising candidate and in consequence an alternative material for active device in silicon photonics technology.
Few years ago, we have developed an efficient method to extract semiconducting nanotube (s-SWNT), using a polyfluorene agent in toluene followed by ultracentrifugation steps [1]. We demonstrated that this method allows obtaining metallic-free s-SWNT samples, as confirmed by photoluminescence, absorption and Raman spectroscopy, and the realisation of high Ion/Ioff FET devices.
This achievements leads to the first experimental demonstration of a strong optical gain of 160 cm-1 at a wavelength of 1.3 µm in (8,7) s-SWNT at room temperature [2]. A special emphasis will be put on the s-SWNT extraction, as optical gain could not be achieved in a raw or lowly extracted sample.
Carbon nanotube properties were then relied on the existing silicon photonic platform, and we envision the use of carbon nanotubes as active optoelectronic devices in silicon. A complete study of the coupling between carbon nanotubes and silicon waveguides was performed [3]. In particular, temperature independent emission up to 100°C from carbon nanotubes in silicon was demonstrated, which opens bright perspectives for future high performance integrated circuits
(Figure : Integration scheme of carbon nanotube with silicon waveguide, showing carbon nanotube emission throught the waveguide)
[1] N. Izard, S. Kazaoui, K. Hata, T. Okazaki, T. Saito, S. Iijima and N. Minami, Appl. Phys. Lett., 92, 243112 (2008)
[2] E. Gaufrès, N. Izard, X. Le Roux, D. Marris-Morini, S. Kazaoui, E. Cassan and L. Vivien, Appl. Phys. Lett., 96, 231105 (2010)
[3] E. Gaufrès, N. Izard, A. Noury, X. Le Roux, G. Rasigade, A. Beck and L. Vivien, ACS Nano, 6, 3813 (2012)
Consolidated Vacuum Sublimation Module: a Purification Apparatus and Process for Solid-Phase Materials
Authors: May Michael , Paul Elizabeth , Katovic Vladimir 
Published: February 2020

A consolidated Vacuum Sublimation Module [cVSM] provides engineering improvements over conventional sublimation apparatus. As implied, the cVSM is structurally modular and it comprises: valve stem unit, valve/Collector/jacket unit, lower glass body, FKM seals, threaded PTFE bushing, and an internal glass cartridge [see US patent 7794694]. In association with the cVSM, a batch sublimation process was developed to purify solid-phase materials such as ferrocene, perylene, oxalic acid, and pentachlorobenzene.
To effect sublimation, the lower glass body is controllably heated to establish a vertical temperature gradient. The temperature gradient along the [evacuated] lower body surface was measured versus input electric power. At steady state, an input of ~37 watts generated +530K at z=0 and +314K near z=95 mm. When operated with natural cooling, the starting material recovery was typically ≥95 mass%. Design features of said Module include: concentric multi-tubular geometry, elongated tapered Collector, positively compressed seals, natural Collector cooling, minimal power consumption, transparency, and glovebox compatibility. The [static vacuum] leakage of an empty cVSM measured <20 ppmv of air per hour. Lastly, the prototype Module has been moderately scaled-up and demonstrated.
Al-Zn Alloy Formation from Non-Aqueous Solution By Electrochemical Technique
Authors: Sano Katsuhito , Tasugi Naoya , Watanabe Nobuaki , Koiwa Ichiro 
Published: February 2020

Introduction

At present, the hot dipping of Zn-Al, uses to suppress the corrosion of the steel. In addition, Al-Zn alloy become a high strength material such as duralumin by making the alloying with Mg and Cu.
An aluminum, that is less noble than hydrogen is, not able to be electrodeposited from aqueous solution.1)Therefore, the electrodepositions using ionic liquids or non-aqueous have been studied. However solution such as toluene, which has a risk of causing a spontaneous combustion because of it’s high flammable. An ionic liquids are salts whose melting point less than 100 ℃. Since the solution has very high electrical conductivity, high stability and, low volatility, it is suitable for plating solvent.
In this study, we report on the results of the plating of the Al-Zn alloy films from the plating bath with AlCl3, ZnCl2 and dimethyl sulfone (DMSO2).

Experiment

The plating solution was composed of AlCl3, ZnCl2 and DMSO2. The total metal chloride ratio, (AlCl3 + ZnCl2) / (DMSO2 + AlCl3 + ZnCl2), is constant at 33.3 mol%. The ratio of ZnCl2 to AlCl3 is controlled from 0.005 to 1.0 mol%. A current density is 600A/m2. The acid activating (RT, 1min) after alkaline degreasing (60 ℃, 5min) is performed as pretreatment process. The plating was performed at 150 ℃ for 30 minutes. As analysis method of sample, we used X-ray diffraction (XRD), energy dispersive x-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS).

Results and Discussion

Effect of bath composition
As a result of changing the bath composition, metallic gloss plating film was deposited up to 0.05 molar percent metal salt concentration of Zn. The gray film was obtained in 1.0 molar percent.
Results of by EDS
The composition of the deposited Al-Zn alloy plating films was estimated by using EDS. The content of Zn is increased with increasing the concentration of the metal salt Zn.
Result by X-ray diffraction (XRD)
Figure 1 shows an XRD pattern of the sample. The peak of the Al can observed without the sample of 0.1 molar percent of Zn salt.
Figure 2 shows an enlarged view of Al (200) peak area. With increasing of the Zn metal salt concentration, the diffraction peak is shifted to a lower angle side, and the half width is increased. An atomic radius of Zn and Al are 125 and 135 pm, respectively. The diffraction peak will be shifted to high angle in accordance with Vegard’s low, when Zn is replaced by Al site. The increase of half width shows deterioration of crystallinity.

Acknowledgements

This work was partially aided by MEXT-supported Program for the Strategic Research Foundation at Private Universities.

References

T. Hirato, J. Fransaer, and J. P. Celis,

J. Electrochem.Soc., 148, C280 (2001).
Synthesis of Ellipsoid TiO2 Nanoparticles and Their Application to Photoelectrodes of Dye-Sensitized Solar Cells
Authors: Shimoyama Yuki , Furue Miwako , Kikuchi Takahiro , Tomita Koji , Kunugi Yoshihito 
Published: February 2020

Dye-sensitized solar cells (DSSCs) have attracted extensive attention due to their potential low cost and high energy conversion efficiency, rendering them one of the most promising systems for solar-to-energy conversion. At the heart of these solar cells is a mesoporous TiO2 electrode, which not only provides a high surface area for accommodating the light-absorbing sensitizer but also serves as the stable conductor for photogenerated electrons. Although the solar-to-energy conversion efficiencies were found to be increased resulting from the increased light scattering, such kinds of photoanodes still suffered from low electron transport capability because of their particle stacking nature that forms large quantities of grain boundaries. In this work, we try to synthesis ellipsoid TiO2nanoparticles which can provide a fast way for electron transport and offer reduced trapping of photoinjected electrons during the path to back contact.
Ellipsoid TiO2 nanoparticles were synthesized by hydrothermal method. The morphology of the TiO2 nanoparticle was characterized with a scanning electron microscope. TiO2 paste was prepared as follows, ellipsoid TiO2 nanoparticles (1.850g), acetylacetone (0.20ml), Triton-X (30%, 1.0 ml) and polyethyleneglycol (0.185g) were mixed into acidic water (pH=0.7). The resulting TiO2 paste was printed by doctor blade method on fluorine-doped SnO2-coated (FTO) glass electrodes and sintered at 450 °C for 30 min. DSSCs were prepared by a conventional procedure.
According to SEM images of the ellipsoid TiO2 nanoparticles, particle length and width were 240 and 40 nm, respectively. The ellipsoid TiO2 powders were characterized by XRD, and determined their crystal structure is anatase. We have successfully fabricated ellipsoid TiO2 based DSSCs, and their conversion efficiency was 6.8% under AM 1.5 simulated full sunlight (100 mW cm−
2) illumination.
Pdm/Rgo with Enhanced Catalytic Activity for Electrooxidation of Formic Acid
Authors: Hu Chenyao 
Published: February 2020

With the ever-increasing environmental problems and the up-coming depletion of fossil fuels, the direct formic acid fuel cells (DFAFCs) have aroused wide research interests in recent years[1-2]. There are several advantages of formic acid such as higher theoretical open circuit potential, lower crossover through the membrane, nontoxicity and uninflammability at room temperature, thus the DFAFCs are thought to be the one of the most promising power sources for portable electronic devices [3]. However, for commercial application, one of the essential issues is the design of effective and low cost anode catalysts for DFAFCs. Pd-based catalyst seems to be the best candidate for its lower cost and excellent catalytic activity toward formic acid electro-oxidation compared to Pt-based catalysts [4-5]. However, the stability of Pd is not satisfactory and its activity needs further improvement for commercialization.
In this work, PdM (M = Ni, Co, Ce, Cr, Ir) catalysts dispersed on reduced graphite oxide (RGO) were prepared by a simple hydrogen reduction procedure. The electrochemical measurements reveal that the PdIr catalysts have the best catalytic activity and stability for formic acid electrooxidation.
Reference
[1] Yoon, B. et al., J. Am. Chem. Soc., 127(49), 17174 (2005)
[2] Maiyalagan, T. et al., J. Power Sources, 211, 147 (2012)
[3] Huang, H.et al., J. Mater. Chem., 22(42), 22533 (2012)
[4] Morgan, R. D. et al., J. Phys. Chem. C, 115(39), 19413 (2011)
[5] Zhao, H. et al., Chem. Comm. 47, 2014 (2011)
Development in Phosphor Glass Ceramics Composites
Authors: Chung Yuan-Run , Wu Fan-Bean , Chang Chih-Kun , Liao Jin-Hong 
Published: February 2020

Glass ceramics containing phosphor, GCP, has become an advanced material in high power LED lighting application recently due to its superior optical and thermal performance and elongated lifetime. Glass systems which have lower characteristic temperatures , glass transition temperature(Tg) and glass softening point(Td)…, as well as excellent mechanical strength and chemical stability, are proposed in microelectronics technology, infrared laser technology and sealing of materials. Borosilicate glass systems exhibit lower characteristic temperatures and quality optical properties. By controlling functional elements, further enhancement in thermal, mechanical, and optical properties can deduced. In this study, the YAG phosphor powders embed into designed glasses under controlled atmosphere to from glass ceramics phosphor composites. The thermal, optical properties and structure of borosilicate glass host are discussed. Heat treatment which affects the YAG phosphor incorporation into the glass is also considered. The glass transition temperatures(Tg) and softening points(Td) are 447~483oC, and 476~524oC respectively. A high refractive index of 1.85~1.94 can be reached. The results show that the developed borosilicate glass hosts are suitable for GCP matrix to contain phosphor powders. The YAG phosphor powders are well contained and dispersed in the glasses.
Key words: LED, Glass ceramics phosphor composites(GCPC), Low characteristic temperature, Heat treatment