bluuebunny/crossref_metadata_2025_split huggingface dataset:
Doping Mechanism in Transparent Conductive ZnO Films Grown by Atomic Layer Deposition
Authors: Lee Do-Joong , Kwon Jang-Yeon , Kim Soo-Hyun , Kim Hyun-Mi , Xu Jimmy , Kim Ki-Bum 
Published: February 2020

Transparent conducting oxides (TCOs) have been one of the essential elements of various optoelectronic devices, photovoltaics, and photoelectrochemical energy-harvesting cells which require an electrically conducting layer (s ~103-104 S/cm) with high optical transparency (>80%). The TCOs are typically doped with foreign elements, as in the cases of Sn-doped In2O3 (ITO) and Al-doped ZnO (AZO), and become degenerate semiconductors with an extremely high electron concentration of 1020-1021 cm-3. While TCOs have been deposited by various methods including sputtering, pulsed laser deposition, chemical vapor deposition, and spray pyrolysis, recent emergence of nanostructured solar cells and organic light emitting diodes has accelerated necessity of ultrathin TCO coating onto complex or large surface area substrates at a low deposition temperature which are quite challengeable for the conventional deposition methods. In order to meet those emerging requirements, atomic layer deposition (ALD) has gathered great interest. Since ALD uses an alternative supply of source gases, conformal coating of desired films can be readily elucidated onto high-aspect-ratio structures and film thickness can be exactly controlled by repeating discrete ALD cycles. Therefore, there have been increasing demands of integrating ALD-grown TCOs into the emerging applications addressed above.
In this presentation, we report structural and electrical properties of ‘atomic-layer-doped’ ZnO films.[1,2] Firstly, Al-doped ZnO films were deposited by ALD via alternate stacking of a ZnO matrix and AlOx dopant layers. Scanning TEM-HAADF analysis revealed that the ALD-AZO films have a unique layer-by-layer structure as those were grown. Upon correlation of the structural and electrical properties, effects of the layer-by-layer doping manner were interpreted in order to investigate a carrier generation mechanism of the ALD-AZO films. In the latter part, efforts of optimizing electrical properties of ALD-ZnO films will be given by controlling surface coverage of dopant ions incorporated in each atomic-doping layer. These efforts include two approaches; i) control of the amount of Al ions deposited during 1 ALD cycle of AlOx via process-parameter adjustment, and ii) introduction of other dopant oxides (group III: In, B, transition metals: Hf, Zr, Ti) which have different surface coverage. Among the tested dopants, it is remarkable that Ti exhibited the highest electrical conductivity (950 S/cm) and doping efficiency (51%). This finding is extraordinary compared to the conventional homogeneous compounds where Al has long been considered as one of the best dopants for the ZnO.
[1] D.-J. Lee, K.-B. Kim et al., Adv. Funct. Mater. 21, 448 (2011).
[2] D.-J. Lee, K.-B. Kim et al., J. Electrochem. Soc. 158, D277 (2011).
Invited; Stress and Doping Impact on Intrinsic Point Defect Behavior in Growing Single Crystal Silicon
Authors: Sueoka Koji , Kamiyama Eiji , Vanhellemont Jan 
Published: February 2020

For the further development of 450 mm-diameter defect-free Si crystals, one has to take into account the impact of thermal stress on intrinsic point defect properties and behavior during single crystal growth from a melt. In this study, we evaluate the impact of thermal stress between -30 MPa (tensile) and 30 MPa (compressive), which probably covers the actual values in mass production for 450 mm-diameter crystals, on the so-called Voronkov criterion of dominant point defects.The dependence of the formation and migration enthalpies of vacancy V and self-interstitial I on the stress is evaluated by density functional theory (DFT). The obtained results are used to more accurately describe the impact of thermal stress on the critical (v/G)0. The impact of compressive thermal stress on (v/G)0 is predicted to shift the growing Si crystal more vacancy-rich, as recently confirmed experimentally by Nakamura et al (ECS Solid State Letters, 3 (2014) N5-N7). Furthermore, the dependence on the thermal stress of the process window for defect-free Si growth is clarified, which is important for the development of the pulling process of future large-diameter defect-free Si crystals.
Also the mechanisms behind the experimentally observed impact of the type and concentration of substitutional dopants on intrinsic point defect behavior and formation of grown-in defects (voids and interstitial clusters) in a Si single crystal growing from a melt, are clarified. DFT calculations with 216-atom supercells are carried out to obtain the formation energies of V and I at all sites within a sphere around the dopant atom with 6 A radius for V and 5 A radius for I. P-type (B and Ga), neutral (C, Ge, and Sn) and n-type (P, As, Sb, and Bi) dopants are considered. The formation energies of V and I around dopant atoms change depending on the types and sizes of dopants. On the basis of the calculated results, an appropriate model of intrinsic point defect behavior in heavily doped Si is proposed. (1) The incorporated total V and I concentrations at the melting point depend on the types and concentrations of dopants. (2) Most of the total V and I concentrations contribute to Frenkel pair recombination during Si crystal growth at temperatures much higher than those to form grown-in intrinsic point defect clusters. The Voronkov model, while taking into account the present improvements, clearly explains all reported experimental results on grown-in defects for heavily doped Si.
The proposed improved Voronkov model uniformly explains point defect behavior for all dopant types and concentrations, taking into account also thermal stress levels.
Deep-Level Defects in High-Dose Proton Implanted and High-Temperature Annealed Silicon
Authors: Jelinek Moriz , Laven Johannes , Rommel Mathias , Schustereder Werner , Schulze Hans-Joachim , Frey Lothar , Job Reinhart 
Published: February 2020

Proton-implantations are valued for their ability to modify the properties of semiconductor grade silicon over a wide spatial range spanning four orders of magnitude between a depth of about 100 nm and 1 mm at comparatively low thermal budgets. At moderate proton doses up to about 1×1013 cm-2 and low annealing temperatures at about 300 °C, proton implantations are used to tailor the carrier life-times in bipolar power semiconductor devices. A large number of deep-level defects are known to form in this parameter regime. At higher doses and higher temperatures proton implantations may be used for modifying the doping profile of the silicon substrate by the creation of hydrogen-related thermal donors. While a large number of studies have investigated deep-level defects induced in the parameter regime typical to life-time tailoring, only few are concerned with the deep-level defects remaining in the samples.
In this report we give a brief review of the principal mechanisms of deep-level defect formation after proton irradiation and subsequent annealing of float zone-grown crystalline silicon. Various reaction paths commonly related to vacancy-complexes, interstitial oxygen and hydrogen are discussed. In the experimental part of the study, new DLTS measurements of proton-irradiated pn-diode structures are presented. The study focusses on the regime of elevated doses and annealing temperatures, typically used for proton-implantation doping. The results suggest that for the increased doses used, some of the detected defects show a thermal stability differing from that reported in literature. At least for some of these defects, this may be due to their higher initial concentration. In addition, other defects may appear at higher temperatures as decay products of other, thermally more stable, defects induced by the high-dose implantations.
For the first time, we also report on two defect levels at 300 meV and 418 meV below the conduction band with a metastable behavior. The observed levels and their behavior show a high similarity to a negative-U defect known from samples implanted at 88 K without any further thermal budget above room temperature. To our knowledge, these levels have not been detected in a sample annealed above room temperature before.
The figure depicts possible reaction paths of vacancies in crystalline silicon under the presence of extrinsic hydrogen and oxygen. Many of these defects lead to localized levels in the silicon bandgap and can therefore impact the electrical properties of a device. The actual appearance of a defect is however determined by the activation energy for its formation together with the applied process temperatures. If known from literature, the activation energy for each reaction path is indicated.
Invited; Light Induced Degradation in Compensated B-Doped Czochralski Silicon
Authors: Yang Deren 
Published: February 2020

Light induced degradation (LID) in B-doped Czochralski Si solar cells is a universal phenomenon, which reduces the conversion efficiency by 2-5% relatively. It is believed that Boron-Oxygen complexes are formed during light illumination, which are the effective recombination centers. Studies in the exclusively B-doped Si, B/Ga co-doped Si and p-type B/P compensated Si show that the saturated concentration (Nt*) of B-O defect is proportional to the B concentration (NB
) (or the net hole concentration p0
) and the generation rate constant (Rgen
) proportional to p0
2
. Interestingly, the LID has also been found in n-type B/P compensated Si, which was supposed to be unlikely to happen. Hence, it brings out a fundamental question of whether the p- and n-type B-doped Si have the same formation mechanism of LID.
In this presentation, we will report our recent work about LID in B-doped compensated Cz silicon. It is believed that the BO defect density in compensated silicon depends on the B concentration and the net doping concentration. Moreover, High B concentration in the compensated silicon results in very serious cell efficiency loss. Furthermore, The electrical parameters of the reference and compensated cells can get fully recovered by illumination at high temperatures.
Moreover, the LID in n-type B-doped Cz silicon with thermal donors (TDs) compensation is also reported. The advantage of TDs compensation is able to obtain a variation of carrier density but with a constant NB
. We find that the formation of B-O complex also occurs under the light illumination and can be annealed out quickly in the dark at 200 oC. The Nt* exhibits a nonlinear dependence on the majority carrier concentrations n0
, and the Rgen
is independent on the n0
. The formation activation energy is determined to be 0.4 eV, identical to the value in p-type Si. Based on the results, we believe that the nature of LID in p- and n-type silicon should be the same.
Nuclear Forensics Using Plasma Source Ion Beams
Authors: Boswell Rod , Smith Noel , Charles Christine , Martin Noel , Tesch Paul 
Published: February 2020

Secondary Ion Mass Spectroscopy uses beam of primary ions (typically O-) focused onto a target. Sputtered secondary ions are measured by mass spectrometer which can detect elements and their isotopes in the low parts per billion (10-9 or ng/g) range. Particles as small as a few 100 nanometres can be analysed.
Time of Flight (TOF)SIMS measures the time of arrival of the secondary ions at the detector, which depends on their mass yielding an extremely good high mass resolution.
It can detect: cocaine in urine, benzodiazepines (eg. valium) in hair and gunshot residues in fingerprints even after strenuous washing!
Additionally, TOF-SIMS can simultaneously detect cocaine in the presence of other drugs (i.e. flurazepam (a benzodiazepine hypnotic) and chlorpromazine (used for psychosis and heroin withdrawal) in urine.
It is possible to relate the TOF-SIMS fingerprints to the evidence found at the crime scene, which can be considered as examination of forensic evidence transfer.
Elemental composition of anthrax spores using TOF-SIMS has been carried out by Weber et. al. at LLNL. This is of use in assessing the origin of bio-weapons.
Oregon Physics has developed the HyperionTM system of high brightness plasma ion sources which are now being used on Focused Ion Beams and TOF-SIMS around the world. These plasma sources are ten times brighter than present sources and reduce the time necessary for analysis from days to hours. They are also more reliable and can be focused down to smaller spots.
Plasma Solutions for Life Sciences and Medical Device Manufacturing
Authors: Foote David 
Published: February 2020

The medical device industry is highly regulated which demands reliable and reproducible components and manufacturing processing to satisfy said regulators. Regulated devices range from a simple bandage to the most complex implantable heart defibrillator. Developing these devices requires rigorous testing and validation of the materials and processes used to manufacture them. Challenges abound due to issues with bio-compatibility, material mismatch, implant duration, ability to withstand sterilization, wettability, lubricity, and so on. Plasma processes address many of these challenges while enabling more reliable and robust devices. Plasma has been shown to enhance surface wettability, remove surface contamination, improve bondability and maintain the bulk properties of the material treated.
Medical diagnostics are highly dependent on reliable chemical analytic techniques where fluids are contacted with reagents in polymer containers such as microtiter plates or plated used in gene sequencing systems or chemiluminescence detection tools. The reliability of such techniques are dependent upon the repeatable wetting of the containers by the fluids and/or reagents. Plasma processing is an excellent choice for increasing the surface energy of polymers enabling more wettable surfaces.
Because plasma treatment will enhance the surface energy of samples treated it is chosen prior to adhesive bonding, lubricious coating application, polymer coating application, device printing, etc. Plasma is also useful for depositing polymer films via plasma assisted polymerization. Plasma polymer films can be used to enhance adhesion of subsequent bonding steps and in certain cases forms an excellent tack reduction film when deposited on rubber compounds. Plasma is also utilized to remove surface contaminants that can interfere with subsequent bonding steps.
Specific application examples will be presented showing the many uses and benefits of plasma processing for medical devices.
Through Silicon via Filling by Electroplating Using Reduced Graphene Oxide (rGO) as a Conducting Layer
Authors: Chang Shih-Cheng , Dow Wei-Ping 
Published: February 2020

Graphene materials, including single layer and multi layer graphene platelet, have recently drawn extensive attention due to their outstanding electrical and thermal properties. Reduction of grapheme oxide (GO) is a method for preparing the graphene film. Since GO has a large amount of oxygen functional groups, it can be well dispersed in several solvents and enable it to be coated on a substrate by using a chemical grafting method[1].
Three-dimensional (3D) chip stacking is a major focus in recent research and development of microelectronics, MEMS, and MOEMS technology. Through silicon vias (TSVs) play a key role in the 3D IC chip stacking connections. A main advantage of TSV is to make the shortest chip-to-chip vertical interconnection, which allows for size reduction of the chip and reducing signal transmission delay[2]. Electrodeposition plays an important role for TSV metallization, especially copper electrodeposition, which is a critical technology and generally used in the 3D chip packaging.
For TSV technology, the thermo-mechanical fatigue may lead to failure in the TSV interconnects[3] because the coefficient of thermal expansion (CTE) of copper is much higher than that of silicon. The package materials with different CTEs will induce large stresses at interfaces. In order to overcome this problem, copper should be substituted by tungsten. However, tungsten cannot be directly plated from an aqueous electrolyte, it can be co-deposited with iron group metals. Alternatively, since the CTE of graphene is much closer to silicon than copper, we choose graphene sheets to substitute copper seed layer.
Traditional process for TSV fabrication is a dry process that includes the following step: (1) formation of vias by reactive ion etching; (2) formation of a SiO2isolation layer; (3) deposition of a TiN barrier layer and a copper seed layer; (4) electrodeposition of copper inside the via. In our research, we reduce the procedure of TSV fabrication using a wet process to substitute barrier and seed layer with graphene, and electrodeposition with Ni-W alloy to make a copper-free TSV. In other words, a copper-free TSV with simplified process steps is fabricated, leading to a low fabrication cost. Moreover, a low-stress TSV filled with low CTE materials (Ni-W and rGO) is also fabricated to improve the thermo-mechanical fatigue of TSV, leading to better package reliability.

References

1. P. Songfeng, and C. Hui-Ming, “The Reduction of Graphene oxide ”, Carbon., 2012, 50, 3210-3228.
2. K. Kondo, T. Yonezawa, D. Mikami, T. Okubo, Y. Taguchi, K. Takahashi, and D. P. Barke, “High Aspect Ratio Copper Via Filling for Three-Dimensional Chip Stacking”, J. Electrochem. Soc., 2005, 152, 658-662.
3. S. H. Choa, C. G. Song, and H. S. Lee, “Investigation of Durability of TSV Interconnect by Numerical Thermal Fatigue Analysis”, Int. J. Pricis. Eng. Man., 2011, 12, 589-596.
.
Numerical Analysis of the Correlation between the Cu+ Ion Concentration and the Current Density
Authors: Hayashi Taro , Kondo Kazuo , Yokoi Masayuki , Saito Takeyasu , Okamoto Naoki 
Published: February 2020

Introduction

3D chip stacking realize high-density packaging and high-speed performance. High-aspect-ratio through-silicon via(TSV) allow short interconnects and reduced signal delays. This TSV interconnection will be applied to wide I/O memories of the next generation smart phone. Cu electrodeposition in high-aspect-ratio via is one of the key technologies for 3D packaging. Voids or seams formed in the via may causes serious problems in reliability. The formation of the Cu+ ion is a crucial intermediate and the Cu+ion intermediate is always produced during the electrodeposition process (eq.1 and 2).
We already reported that 4 μm diameter via of aspect ratio of 7.5 is perfectly filled with the increasing Cu+ ion concentration inside the via[1,2]. Additionally, K. Kondo et al. have reported that a large amount of Cu+ ion within the confined area of the trench of the trench bottom electrodes and experimentally verified the relation between the Cu+ ion and acceleration[3]. In this study, we have calculated the Cu+ion concentration shifting at the trench bottom during electrodeposition by using COMSOL Multiphysics.

Numerical Analysis

The simulation model is shown Fig.1. We have assumed that the electrode surface is only trench bottom. And the reaction equations of Cu2+ ion and Cu+ ion at trench bottom are shown eq.3 and 4. The reaction kinetic parameters, k1, k-1, k2 and k-2 have been reported our previous study[2]. The reaction kinetic parameter from Cu2+ ion to Cu+ ion, k1 as 8.4×10-8 m/s, that from Cu+ ion to metallic Cu, k2 as 5.5×10-5 m/s, that from Cu+ ion to metal Cu2+, k-1 as 7.0×10-6 m/s, that from metallic Cu to Cu+ ion, k-2 as 1.6×10-8 m/s. Additionally, the diffusion equations in the electrolyte are shown eq.5 and 6. In this simulation model, the reverse current has been applied from 1 to 13 s, and the off-time has been applied from 0 to 1 s and 13 to20 s.

Results and discussion

We have calculated the Cu+ ion concentration shifting at the trench bottom with various trench widths. The calculation results are shown in Fig. 2. From Fig. 2, we have understood that the Cu+ ion concentration increase with the reverse current(1s to 13 s) and the off-time(13s to 20 s) with narrowing trench widths.

Figure 3 shows the result of LSV measurements by using trench-shaped through mask electrode that reported in reference 3. Before measurements, the trench bottom electrode has been dissolved for 12 s with 10 mA/cm2 in order to produce Cu+ ion at the trench bottom. From Fig. 3, we have understood the current density increase with narrowing trench widths.

Cu(I)Thiolate formation and acceleration effect will be discussed at the meeting.
[1] T. Hayashi et al., J. Electrochem. Soc., 160(6) D256 (2013).
[2] T. Hayashi et al., ECS 224thMeeting (2013).
[3] K. Kondo
et al., ECS Electrochem Lett., 3(4) D3 (2014).
Barrier Metal Slurry for Low Defect Copper Damascene Chemical Mechanical Polishing
Authors: Kim Hojoong , Seo Kyewon , Moon Jinok , Kim Hyunsoo , Hwang Hasub 
Published: February 2020

In the semiconductor process, chemical mechanical polishing/planarization (CMP) is inevitable in copper (Cu) interconnect forming. Cu damascene scheme is achieved by help of CMP to form highly ordered metal lines.
As the CMP process uses a set of partial polishing steps to complete a damascene structure, slurries of each partial step is designed to have different performances to that of other steps. Among the steps, final partial step, so called, barrier metal (BM) CMP is a critical step because it determines the superior flat finish.
In the BM CMP, a structure consists of heterogeneous materials such as Cu, dielectric oxide, and BM should be polished at once. Thus, abrasive suspended in the BM slurry should be optimized to achieve the superior flat finish.
In the present study, 3 kinds of BM slurry were utilized. Abrasive of those slurries are made of colloidal silica in the size of 30 nm to 60 nm. The abrasive surfaces, however, are differently modified to have suitable performance for various polishing environments. The modification involves shape of abrasive, chemical additive to increase suspension stability, coating with polymers, and operation pH. Their effects on the CMP performance not only for blanket wafers but also for pattern wafers having 2x nm pitch were observed experimentally. The results indicated that not only polishing performance but also defect occurrence, which is important in mass fabrication, should be considered equally. Finally, strategy for reducing defect occurrence while maintaining Cu damascene performance will be discussed.