Microelectronic Materials Research Articles

High Glass Transition and Optical Transparency of Novel Organosoluble Polyamides Containing 4‐tert‐‐Butyltoluene Moiety

AbstractA series of novel polyamides 3a–3d containing 4‐tert‐butyltoluene moiety, were prepared using the phosphorylation polycondensation technique. FT‐IR and 1H NMR techniques were used to investigate the chemical structures of 3a–3d. The results confirmed that they agreed with the proposed structures for 3a–3d completely. The 3a–3d had inherent viscosities ranging from 0.71 to 1.67 dL·g−1. All the polyamides showed excellent solubility, with the dissolvability at a concentration of 10 wt% in most amide polar solvents. Flexible and tough polyamide films could be prepared by casting from DMAc (N,N‐dimethylacetamide) solvent. Their films were nearly colorless and exhibited high optical transparency, with the UV cutoff wavelength in the range of 346–363 nm and transmittance higher than 80% at 450 nm. They also exhibited high glass transition temperatures in the range of 310–343°C and the onset decomposition temperatures in the range of 435–462°C in nitrogen atmosphere. Meanwhile, these polyamide films possess good mechanical properties with tensile strengths of 76.4–86.1 MPa and elongations at break of 11.2%–27.3%. Due to those properties, these polyamides could be considered as photoelectric and microelectronic materials.

Photoluminescence in Non-Stoichiometric Silicon Nitride Films Obtained by Reactive Sputtering

The quest to improve silicon properties for optoelectronic applications is a challenge for many researchers. The answer appears to rely on microelectronic compatible materials enhanced with embedded nanostructures. We used reactive sputtering to produce films with non-stoichiometric silicon nitride. The excess of silicon in those samples is then aggregated by subsequent thermal annealing. By carefully choosing deposition parameters and annealing temperatures, an improved photoluminescence response was obtained. The temperature effect on the photoluminescence from the samples was investigated between 10 and 300 K. We observed a moderate signal improvement at lower temperatures, with no significant spectral response change. The composition of the samples was obtained by Rutherford Backscattering Spectrometry and the sample thickness was measured by spectral ellipsometry. We observed a large increase in photoluminescence response for samples with increased oxygen concentrations.

Atom probe tomography: from physical metallurgy towards microelectronics

Abstract Atom probe tomography (APT) is the only approach able to map out the 3D distribution of chemical species in a material at the atomic-scale. It has been applied to a number of issues in physical metallurgy including precipitation, segregation of impurities to lattice defects, ordering, magnetic multilayers. The implementation of ultrafast laser pulses instead of high-voltage pulses to field evaporate surface atoms has been a major breakthrough as this opened APT to semi-conductors or oxides that are key materials in microelectronics. This article reviews some of the more recent salient findings in physical metallurgy and microelectronics materials using APT. Special attention is paid to the role played by APT in the elucidation of irradiation-induced segregation effects. The following section deals with the segregation of dopants to crystal defects in silicon, a phenomenon that has a considerable influence on properties and performance of latest generation nano-transistors and devices.

Highly Soluble and Transparent of Novel Polyimides Containing Trifluoromethyl and Cyclohexane Units

Two novel polyimides(PIs) were polymerized from 1,4-bis((4-amino-2-(trifluoromethyl)phenoxy)methyl)cyclohexane, with aromatic tetracarboxylic dianhydrides using the typical one-step method. The inherent viscosity of the PIs were around 0.90dL/g, and they exhibited an excellent solubility and optical property. They were readily soluble not only in some strong polar solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), but also in some low-boiling-point solvents such as chloroform (CDCl3), and tetrahydrofuran (THF). The PIs film showed high optical transparency and colorless with cut-off wavelength in 332nm and 338nm. Meanwhile, the temperature of 10% weight loss in air and nitrogen were higher than 441°C and 449°C respectively, and their glass-transition temperature (Tg) were higher than 348 °C. Furthermore, they possessed good mechanical properties with tensile strengths of 69–71MPa, elongations at break of 11.6–15.4% and low moisture absorption (<2%).Due to their properties, the polyimides could be considered as photoelectric and micro-electronic materials.

Effect of alkaline slurry on the electric character of the pattern Cu wafer

For process integration considerations, we will investigate the impact of chemical mechanical polishing (CMP) on the electrical characteristics of the pattern Cu wafer. In this paper, we investigate the impacts of the CMP process with two kinds of slurry, one of which is acid slurry of SVTC and the other is FA/O alkaline slurry purchased from Tianjin Jingling Microelectronic Material Limited. Three aspects were investigated: resistance, capacitance and leakage current. The result shows that after polishing by the slurry of FA/O, the resistance is lower than the SVTC. After polishing by the acid slurry and FA/O alkaline slurry, the difference in capacitance is not very large. The values are 0.1 nF and 0.12 nF, respectively. The leakage current of the film polished by the slurry of FA/O is 0.01 nA, which is lower than the slurry of SVTC. The results show that the slurry of FA/O produced less dishing and oxide loss than the slurry of SVTC.

Infrared quantum dots for liquid-phase thermometry in silicon

The need for new technologies such as forced-liquid convection and evaporative cooling to cool microelectronics has renewed interest in nonintrusive liquid-phase thermometry techniques with micron-scale resolution. A number of such techniques exploit changes in the emission characteristics of photoluminescent species, but require optical access to both excite and image the emissions. Silicon, the leading material for microelectronics, is opaque at visible wavelengths. It is, however, partially transparent in the near-infrared (IR). Quantum dots (QD), or colloidal semiconductor nanocrystals, of lead sulfide (PbS) emit in the near-IR. Although the emissions from PbS IRQD vary with temperature, the poor photostability of these IRQD in a colloidal suspension due to surface oxidation made them impractical for liquid-phase thermometry. Recently, new methods have made it possible to overcoat a layer of cadmium sulfide (CdS) on PbS ‘cores’. Experiments to evaluate the temperature sensitivity of CdS-coated PbS IRQD emitting around 1.35 µm suggest that the emissions from these core–shell structures, when suspended in toluene and illuminated by 488 nm, change 0.5% per °C at temperatures of 20–60 °C. The uncertainty in the liquid-phase temperatures using these tracers was estimated to be less than 0.3 °C. Moreover, the IRQD had a consistent temperature response for more than 100 days after suspension.

The Study of Humidity Effect on Self-Heated Surface Micromachined Polysilicon Resistor

Polysilicon is a very attractive material in microelectronics for thermal sensors. In this paper, the effect of humidity on thermal resistance of surface micromachined polysilicon is invested. It is found that the thermal conductivity variation of air due to humidity changes the suspended polysilicon resistor evidently. This property could be used as the working principle of relative humidity sensor.

Influence of the substrate platform on the opto-electronic properties of multi-layer organic light-emitting field-effect transistors

In this paper, we present a study of the effects of the influence of the substrate platform on the properties of a three-layer vertical hetero-junction made of thin films of α, ω-diperfluorohexyl-4T (DHF4T), a blend of tris(8-hydroxyquinoline)aluminium (Alq3) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) and α, ω-dihexyl-quaterthiophene (DH4T). The hetero-junction represents the active component of an organic light-emitting transistor (OLET). The substrate platforms investigated in this study are glass/indium-tin-oxide/poly(methyl-methacrylate) (PMMA) and Si++/silicon oxide (SiO2)/PMMA. The first platform is almost completely transparent to light and therefore is very promising for use in OLET applications. The second one has been chosen for comparison as it employs standard microelectronic materials, i.e. Si++/SiO2. We show how different gate materials and structure can affect the relevant field-effect electrical characteristics, such as the charge mobility and threshold voltage. By means of an atomic force microscopy analysis, a systematic study has been made in order to correlate the morphology of the active layers with the electrical properties of the devices.

(Invited) Advances in Si and Ge Millisecond Processing: From SOI to Superconductivity and Carrier-Mediated Ferromagnetism

This paper reviews the advances that millisecond thermal processing using flash lamps and lasers brings to the processing of the most advanced semiconductor materials, namely silicon and germanium, thus enabling the fabrication of novel microelectronic structures and materials. It will be demonstrated how such developments can translate into important practical applications leading to a wide range of technological benefits. Opportunities in ultra-shallow junction formation for silicon-on-insulator, superconducting Ge and Si, and diluted ferromagnetic Ge, along with the technical reasons for using annealing times in the ms range are discussed in the context of state-of-the-art materials processing. Whereas these examples are based on solid phase processing, the more sophisticated approach regards on working with the liquid phase at the surface of solid substrates. As a recent example the controlled surface melting of a Ge enriched silicon substrate is reported.

Microelectronic materials and structures characterization by impedance spectroscopy

The impedance spectroscopy relies on the measurement of a linear electrical response of an investigated material to a low electromagnetic signal in a wide range of frequency. Further analysis of this response is applied to reveal some information about physicochemical properties of the material. Impedance spectroscopy is a useful, non-destructive tool for the analysis of many material properties. It is also commonly applied for the determination of the electrical parameters of complex electronic and microelectronic structures. This kind of knowledge enables better understanding of the mechanisms of operation of the microelectronic devices under investigation. Fundamental issues are discussed, including the proper interpretation of the experimental results and the construction of the equivalent circuits, which shall consist of the elements representing the impact of the particular mechanisms of electrical conductivity and polarization on the electrical parameters eventually observed in macroscale. The considerations are illustrated by results of the author’s research on thin and thick film structures and materials. Some examples of the impedances spectra analysis and the construction of the equivalent models are presented for various structures, including the, metal–SiO 2–GaAs, metal–TiVPd–Si and thick film humidity and gas sensors.

Nonlinear Micro-Processing of Silicon by Ultrafast Fiber Laser at 1552 nm

ABSTRACTProcessing of transparent materials by non-linear absorption mechanisms induced by short pulse lasers has been applied in many fields. Silicon (Si) is widely used materials in microelectronics, MEMS and photonics. It is, however, not transparent for commonly used processing lasers in near infrared to ultraviolet spectral range and has not been a subject for the non-linear processing by lasers so far. In this paper, possibilities and capabilities of non-linear processing of Si by 900 fs, 1552nm laser radiation are described with special emphasis on application to frequency adjustment of a crystal oscillator in a package made from Si.

The Photopolymer Science and Technology Award

The Photopolymer Science and Technology Award No.111100, the Outstanding Achievement Award 2011, was presented to Ralph R. Dammel (AZ Electronic Materials Corporation) for his outstanding achievements in photopolymer science and technology, ′Development of new advanced resist materials for microelectronics′.

구리 CMP 후 버핑 공정을 이용한 연마 입자 제거

Copper (Cu) had been attractive material due to its superior properties comparing to other metals such as aluminum or tungsten and considered as the best metal which can replace them as an interconnect metal in integrated circuits. CMP (Chemical Mechanical Polishing) technology enabled the production of excellent local and global planarization of microelectronic materials, which allow high resolution of photolithography process. Cu CMP is a complex removal process performed by chemical reaction and mechanical abrasion, which can make defects of its own such as a scratch, particle and dishing. The abrasive particles remain on the Cu surface, and become contaminations to make device yield and performance deteriorate. To remove the particle, buffing cleaning method used in post-CMP cleaning and buffing is the one of the most effective physical cleaning process. AE(Acoustic Emission) sensor was used to detect dynamic friction during the buffing process. When polishing is started, the sensor starts to be loaded and produces an electrical charge that is directly proportional to the applied force. Cleaning efficiency of Cu surface were measured by FE-SEM and AFM during the buffing process. The experimental result showed that particles removed with buffing process, it is possible to detect the particle removal efficiency through obtained signal by the AE sensor.

High Strength and Electrical Conductivity of UFG Copper Alloys

Copper based materials are still the most attractive low resistivity materials for microelectronics and electrotechnics applications, though, all variants developed to combine strength and conductivity, such as solid solutions and composites, suffer from decay in electric conductivity while strength is increased . In a addition, linear decay was also conjectured for pure copper when grain size is refined below the UFG and nanostructured domains (except when grain boundaries are pure twins). Copper alloys with low content of silver and chromium were prepared by high pressure torsion (HPT) with various annealing conditions. Vickers hardness and electric resistivity in the temperature range of 4K-340K, were measured as well as microstructural characterizations were performed using quantitative X-ray diffraction. Depending on the annealing conditions the alloys exhibit from 25% to 75% of IACS electric conductivity at room temperature and hardness in the range of 200 Hv. Origins of both high strength and high electric conductivity were investigated from microstructures analysis, using transmission electron microscopy and mechanical testing.

Dose Enhancement and Reduction in SiO$_{2}$ and High-$\kappa$ MOS Insulators

The effects of 10-keV X-rays and 400-keV endpoint-energy bremsstrahlung X-rays on MOS capacitors with SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> or HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gate dielectrics and Al and TaSi gate metallization have been studied using the Monte Carlo simulator, MRED. We compare these calculations with previous results in the literature obtained with other Monte Carlo and discrete ordinates codes, and with experiments on devices with SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gate dielectrics, and find generally good agreement. There is a significant dose reduction in thin HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layers exposed to 10-keV X-rays, when the HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is surrounded by lower-Z materials (e.g., Si, Al). This dose reduction does not occur in a medium-energy bremsstrahlung X-ray environment; in that case, the dose in a HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gate dielectric can be ~10 times higher than the dose in a SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dielectric, for the same incident X-ray fluence. These results demonstrate the capability of MRED to assist in the evaluation of dose enhancement and reduction in regions including or nearby high-Z materials in microelectronic materials and devices.

Room Temperature Synthesis and Characterization of Au Nanoparticles

The new emergent properties of nanoparticles include quantam size effect, nonlinear optical properties and thus the nanomaterials have extensive applications in microelectronic, bacteriostatic and catalytic or magnetic recording materials. Nanoparticles find potential applications in DNA detection and photo detection. Gold nano particles (AuNPs) are useful in nanoscale devices and systems due to its resistance to oxidation. In this paper a cost effective, versatile and simple one step room temperature synthesis of highly stable and freestanding Au quantum dots capped by TTAB (Tetradecyltrimethyl Amonium Bromide) in the range of 10-90 nm is reported. Ultraviolet- visible spectroscopy (UV-VIS), Fourier transformation infrared spectroscopy (FT-IR) was carried out to characterize these samples. Scanning Electron Microscopy (SEM) confirms the AuNPs sizes of about 80 and 88 nm.

Synthesis of volatile inorganic hydrides by electrochemical method

Published data and results of our investigations on the problem of electrochemical synthesis of arsenic, phosphorus, and germanium hydrides are generalized. The results of the developments of the physicochemical bases of arsine synthesis by electrochemical reduction of arsenic acid, phosphine by reduction of white phosphorus in organic solvents, and monogermane by reduction of germanate in basic conditions are reported. The current yield of hydrides is 95, 90, and 40%, respectively. The promising guidelines of the practical use of electrochemical methods of the synthesis of the hydrides in the manufacture of semiconductor materials for microelectronics, optics, and laser engineering are discussed. The development of an arsine generator attracts considerable interest, which can serve as a basis for an aggregative continuous apparatus used in complex flow charts of manufacture of semiconductor materials.

Self‐Organized Polymer Nanocomposite Inverse Opal Films with Combined Optical Properties

Inverse opal films with unique optical properties have potential as photonic crystal materials and have stimulated wide interest in recent years. Herein, iridescent hybrid polystyrene/nanoparticle macroporous films have been prepared by using the breath-figure method. The honeycomb-patterned thin films were prepared by casting gold nanoparticle-doped polystyrene solutions in chloroform at high relative humidity. Highly ordered hexagonal arrays of monodisperse pores with an average diameter of 880 nm are obtained. To account for the observed features, a microscopic phase separation of gold nanoparticles is proposed to occur in the breath-figure formation. That is, individual gold nanoparticles adsorb at the solution/water interface and effectively stabilize condensed water droplets on the solution surface in a hexagonal array. Alternatively, at high nanoparticle concentrations the combination of breath-figure formation and nanoparticle phase separation leads to hierarchical structures with spherical aggregates under a honeycomb monolayer. The films show large features in both the visible and NIR regions that are attributed to a combination of nanoparticle and ordered-array absorptions. Organic ligand-stabilized CdSe/CdS quantum dots or Fe(3)O(4) nanoparticles may be loaded into the honeycomb structure to further modify the films. These results demonstrate new methods for the fabrication and functionalization of inverse opal films with potential applications in photonic and microelectronic materials.

CMOS Development and Optimization, Scaling Issue and Replacement with High-K Material for Future Microelectronics

development and optimization of Silicon technology has been guided by CM OS scaling theory (1) and predications made by Semiconductor Industry (SIA) in the International Technology Roadmap for Semiconductor (ITRS). With the trend of scaling down of Complementary M etal Oxide Semiconductor (CMOS) transistor as Moore's Law (2) requires replacement of conventional silicon dioxide layer with the higher permittivity material for gate dielectric. As the silicon industry moves to 32nm technology node and beyond complaints like leakage and power dissipation dominates. M anaging such issues are crucial factors for reliable high speed operation and chip design. Although scaling will continue for couple of decades but device geometries reaches to atomic size and limitation of quantum mechanical physical boundaries. To address these problems there is need of innovation in material science & engineering, device structure, and new nano devices based on different principle of physics. Here we have elaborated about scaling issues and alternate high-k dielectric for M etal Oxide Semiconductor Field Effect Transistor (M OSFET). Introducing a high-k material may replace today's silicon dioxide technology and can also provide extendibility over several generations. C-V analyses have been studied for various M OS capacitor with conventional SiO2 and also with high-k material like Gd 2O 3, ZrO2, HfO2, and TiO2.

Organometallic functional materials based on siloxane block copolymers

Efficient synthetic approaches to designing nanoscale hybrid organo-inorganic composites containing metal (Zn, Cd, Cu, Zr) sulfides or oxides have been developed. These approaches were used to design the materials with specific electrophysical properties and controllable phase structure. The composites can be used as electroinsulating functional materials (adhesives, varnishes, coatings, and sealants) in microelectronics.