Spin-on Glass Films Research Articles

Characterization of high mobility inverted coplanar Zinc Nitride Thin-film Transistors

In this work, high mobility TFTs based on zinc nitride (Zn3N2) sputtered at room temperature using spin-on glass (SOG) as gate dielectric are presented. The inverted coplanar structure is used for the Zn3N2 TFTs. The devices exhibit an on/off-current ratio of 106 and a subthreshold slope of 0.88 V/decade. The extracted field-effect mobility was 15.8 cm2/Vs which is among the highest reported for Zn3N2 TFTs. In addition, n-type MOS capacitors were fabricated and characterized by capacitance – voltage and capacitance – frequency measurements to evaluate the dielectric characteristics of the SOG film.

Inkjet printable and low annealing temperature gate-dielectric based on polymethylsilsesquioxane for flexible n-channel OFETs

We report on inkjet printable gate-dielectric based on a spin-on-glass (SOG) material for applications in n-type organic field-effect transistors (OFETs). The SOG material is polymethylsilsesquioxane in alcohol mixture. After annealed at 135 °C in air, the SOG films are well crosslinked and have a good resistance against alcohol, which allows for the inkjet printing of Ag gate electrodes on top of the SOG dielectric. The crosslinked SOG films are very dense, and can withstand high electric field. This is very beneficial to the operation of transistors. In addition, the SOG films have very low hydroxyl content after annealing. This property is very important for n-type transistors. After ink formulation, this SOG dielectric has an excellent inkjet-ability with good uniformity and reproducibility. By using Polyera's P(NDI2OD-T2) as the semiconductor and SOG as the dielectric, bottom-contact top-gated n-type transistors were successfully fabricated on PET substrates with electron mobility above 0.1 cm2/V and high on/off ratio well above 105. These remarkable results demonstrate that this newly formulated SOG dielectric is a promising candidate for the future development of flexible electronic devices.

Self‐Align Fabrication of Narrow‐Gapped Dual AFM Tip Using Si Trench Refilling with SOG and Magnetostrictive Film Stacked Dual Cantilever Formation

SUMMARYThis paper reports on a novel self‐align fabrication process of narrow‐gapped dual AFM (atomic force microscope) tip. The dual AFM tip was fabricated on (100) orientated Si substrate by using narrow trench etching, trench refilling with SOG (spin‐on‐glass), CMP (chemical–mechanical polishing), and Si crystalline anisotropic etching. Through the process, a sharp dual AFM tip with a gap of 500 nm, which was defined only by the etched trench width, was successfully fabricated. Although another fabrication process using an acrylic‐nitrile‐styrene‐epoxy resin refilling was also attempted, a dual tip was not obtained due to the poor adhesion of the resin in the silicon etching process. In addition, a dual AFM cantilever (magnetostrictive film/Si 2.0 μm) was formed by MEMS fabrication. The fabricated FePd 0.4 μm/Si 2.0 μm and Ni 1.3 μm/Si 2.0 μm cantilever were individually deflected to 1.4 μm at 300 Gauss and 0.4 μm at 240 Gauss due to effects of magnetic flux and negative magnetostriction, respectively.

Chemical bond structure and MOSFET device damages of electron beam cured siloxane spin-on-dielectric films

This paper presents the properties of electron beam cured SOG (spin-on-glass) films in terms of the chemical bond structure and accompanying device damages. It is observed that e-beam cured SOG films do not show the Si-CH bonds in the FT-IR spectra but still have the carbons in the film which are thermally stable. As for the device damage, the experimental result shows that the threshold voltage of nMOSFET decreases by positive charging of gate oxide after e-beam curing process and it shows antenna ratio independence. Also, the variation of threshold voltage is largely affected by the cathode voltage, which determines the electron energy and interlayer dielectric thickness.

Raman spectra of heterogeneous nanostructures based on organosilicon films

We studied the effect of ion bombardment on the structure of SOG (spin-on-glass) films. We used IR and Raman spectroscopy and plan-view transmission electron microscopy to study the characteristic features of the structural transformation in organosilicon films when bombarded by nitrogen ions. We show that they are heterogeneous and we establish the presence of inclusions of nanocrystalline graphite.

Densification of spin-on-glass (SOG) film by RF plasma treatment

We propose a spin-on glass (SOG) film densification technique based on the plasma-treatment technology. We demonstrated the densification of the SOG film at the temperature of lower than 53 degree C without compulsory cooling. We investigate the plasma-densification condition and found that the optimum RF power needed to densify the SOG film. This technique is applicable for production processes in wide range of electronic devices.

Effect of Plasma Treatment on Stress Reduction Induced by Shallow Trench Isolation Filled with Spin-on-Glass Dielectric

We used Raman spectroscopy to evaluate the stress induced by shallow trench isolation (STI) filled with spin-on-glass (SOG) dielectric material. We investigated the novel processes, such as the nitrogen into the liner oxide, and the plasma treatment before and/or after cure annealing to suppress the strain introduced by the STI with SOG. We clarified that a nitrogen incorporated liner oxide suppressed the stress in the active area caused by the SOG film shrinkage, and the plasma treatments were also effective at suppressing the stress induction in the active area.

Enhancement of the electrical characteristics of MOS capacitors by reducing the organic content of H2O-diluted Spin-On-Glass based oxides

Abstract In this work, the physical, chemical and electrical properties of Metal-Oxide-Semiconductor (MOS) capacitors with Spin-On-Glass (SOG)-based thin films as gate dielectric have been investigated. Experiments of SOG diluted with two different solvents (2-propanol and deionized water) were done in order to reduce the viscosity of the SOG solution so that thinner films (down to ∼20 nm) could be obtained and their general characteristics compared. Thin films of SOG were deposited on silicon by the sol–gel technique and they were thermally annealed using conventional oxidation furnace and Rapid Thermal Processing (RTP) systems within N 2 ambient after deposition. SOG dilution using non-organic solvents like deionized water and further annealing (at relatively high temperatures ≥450 °C) are important processes intended to reduce the organic content of the films. Fourier-Transform Infrared (FTIR) Spectroscopy results have shown that water-diluted SOG films have a significant reduction in their organic content after increasing annealing temperature and/or dilution percentage when compared to those of undiluted SOG films. Both current–voltage ( I – V ) and capacitance–voltage ( C – V ) measurements show better electrical characteristics for SOG-films diluted in deionized water compared to those diluted in 2-propanol (which is an organic solvent). The electrical characteristics of H 2 O-diluted SOG thin films are very similar to those obtained from high quality thermal oxides so that their application as gate dielectrics in MOS devices is promising. Finally, it has been demonstrated that by reducing the organic content of SOG-based thin films, it is possible to obtain MOS devices with better electrical properties.

Spin-On Glass as low temperature gate insulator

ABSTRACTIn this work, we report the characterization of Spin-On Glass (SOG) as low temperature gate insulator. Our SOG film was deposited at temperature of 200°C, which is compatible to use on flexible substrates. The optical and electrical characterization showed that the refractive index and dielectric constant are very close to those of thermally grown SiO2. Also, analysis of surface roughness by AFM is presented. We demonstrated the use of SOG as gate insulator, fabricating and characterizing inverted staggered a-SiGe:H TFTs. The observed results are promising and suggest that SOG films deposited at 200°C in the Laboratory of Microelectronics of INAOE could be an alternative to improve electrical characteristics of TFTs on low temperature flexible substrates.

Suppression Mechanism of Volume Shrinkage for SOG Film by Plasma Treatment

We investigated the suppression mechanism of volume shrinkage for a spin on glass (SOG) film by plasma treatment using hard X-ray photoelectron spectroscopy, X-ray reflectometry (XRR), and UV-Raman spectroscopy. The suppression of the SOG film shrinkage was attributed to the control of N out-diffusion from the SOG film and O in-diffusion into the SOG film, which was due to the plasma treatment prior to the conventional cure annealing process. It was also confirmed from the XRR measurements that the SOG film was densified by the plasma treatment. Moreover, UV-Raman measurements were performed to evaluate the Si stress at the SiO2/Si interface that was induced during the gap filling process. The stress was controlled by the appropriate plasma treatment. Thus, we concluded that the plasma treatment was effective for the suppressions of SOG film shrinkage and stress induction and for the SOG film densification.

Reduction effect of line edge roughness on time-dependent dielectric breakdown lifetime of Cu/low-k interconnects by using CF3I etching

The authors investigated the etching of grooves in low-k in Cu technology. Correlation between the line edge roughness (LER) and the time-dependent dielectric breakdown (TDDB) reliability for 100nm pitch Cu interconnects was investigated. They controlled LER by using various gases to etch multilayer photoresist. CF3I gas was found to reduce LER better than conventional gases such as CF4 and CHF3 because CF3I has higher etching selectivity of photoresist against spin-on glass film. The LER did not affect measures of electrical performance such as wiring resistance, capacitance, and leakage current, but did affect TDDB lifetime because, according to their simulation, the electric field was strongly enhanced at curvatures in the interconnects. The maximum electric field (Emax) was also determined to evaluate the effect of LER on TDDB lifetime. All their results show that CF3I etching is promising for creating reliable Cu interconnects with smaller pitches.

A shear horizontal surface acoustic wave sensor for the detection of antigen–antibody reactions for medical diagnosis

Abstract In this paper we describe the development of a shear horizontal surface acoustic wave immunosensor for medical diagnostics. There exists a strong interest in the rapid detection of antigen–antibody reactions at small concentrations in the μ g/ml region in plasma, serum, or whole blood. Sensors whose operating principle is based on shear horizontal acoustic surface waves are well suited for this. We have used a spin-on glass film for the guidance of the surface wave as well as for the protection of the aluminum structures of the surface wave transducers from aggressive analyte liquids. This film has proven to considerably enhance the sensitivity of the device, and to simultaneously provide a durable protection of the transducers. Furthermore, polymers based on polyvinylamines have been used for the first time for immobilization of the capture protein. This technique effectively prevents the undesired binding of foreign substances like cells, non-specific antibodies, or other proteins at the sensor surface.

Small angle X-ray scattering measurements of porous low-k films using synchrotron radiation

Synchrotron radiation has been employed to analyze the difference in three representative kinds of spin on glass (SOG) films systematically based on a small angle X-ray scattering (SAXS) technique. The amount of scattering by pores in a SOG film of organic non-template type was found to be extremely smaller than that in low-k films of a template type. The pore size in the organic non-template type SOG film was estimated to be smaller than that of the template type low-k films. A position annihilation lifetime spectroscopy was also applied to confirm the SAXS results. It was found that the consideration of properties of specific low-k films and a scanning strategy in SAXS measurements were important for evaluating the pores of low-k films.

Force sensing submicrometer thick cantilevers with ultra-thin piezoresistors by rapid thermal diffusion

One of the most important requirements for a cantilever-type sensor to obtain high force sensitivity is small thickness. By using current micromachining technology it is possible to produce cantilevers of submicrometer thickness. Where self-sensing piezoresistive cantilevers with submicrometer thickness are concerned, it is necessary to use a technology which can create ultra-thin (<100 nm) piezoresistors on a cantilever surface. This work demonstrates for the first time the application of a relatively simple, rapid thermal diffusion method by using spin-on glass film to fabricate sub-100 nm piezoresistors on an ultra-thin single-crystal silicon cantilever. Compared to other shallow junction fabrication methods, which involve implantation or deposition of a doped layer, this method is advantageous since no damage is created in the crystal structure and no toxic gas or hazardous material is used during the process. Besides, this technique can be applied by using low-cost rapid annealers, which can be readily found in most laboratories. By using this method, piezoresistive cantilevers with stiffness in the range of 0.001 N m−1 with sub-100 nm thick piezoresistors are fabricated, and a complete characterization of the fabricated cantilevers is performed.

Application of Electron Beam Cured Spin-On Glass to Trilevel Resist System for Deep and Vacuum Ultraviolet Lithography

Spin-on glass (SOG) has been used as the middle layer for a trilevel resist system. A conventional SOG film is porous, which results in the deterioration of the resist pattern due to the diffusion of acid in the resist to SOG and poor etch resistance during under-resist etching. In this paper, in order to solve these drawbacks, electron beam (EB) cure was applied to densify the SOG film. The film density of SOG is increased from 1.87 g/cm3 to 2.07 g/cm3 by EB cure. The Fourier-transform infrared spectroscopy (FT-IR) shows that EB cure cross-links silanol moieties to each other by a dehydration reaction. The positive chemically amplified resist is vertically patterned on the EB cured SOG without footing. The etch rate of EB cured SOG under under-resist etch condition reduced by 36% compared with that of SOG before EB cure.

Optical waveguide fabrication by combination of spin-on-glass and plasma-enhanced chemical vapor deposition for optoelectronic integration

Low-loss optical waveguides for optoelectronic integration were realized by the combination of spin-on- glass (SOG) and plasma-enhanced chemical vapor deposi- tion (PECVD). Undercladdings of 20-mm thickness together with cores of 6-mm height and 8-mm width were formed on Si substrates by PECVD and reactive ion etching. Overclad- dings were formed by a combination of SOG and PECVD SiO2 films. This method successfully filled narrow gaps be- tween cores of optical circuits. The refractive index of over- claddings was adjusted by SOG curing and fluorine incorpo- ration in PECVD SiO2 films. A buried-type optical waveguide formed by the combination of SOG and PECVD showed single-mode propagation. Propagation losses and polariza- tion dependent losses at the 1.3-mm wavelength were mea- sured to be 0.3 dB/cm and below 0.15 dB, respectively. © 2003 Society of Photo-Optical Instrumentation Engineers.

Spin-on-glass (SOG) for the trilayer imaging process

Maleic acid catalyzed hydrolysis and condensation of tetramethoxysilane was carried out in 1-propoxy-2-propanol to prepare a spin-on-glass (SOG) material for the trilayer imaging process. The material was found to be stable enough for industry use. Minor amounts of methylsilsesquioxane and photoacid generators were introduced into the material. Thin resist (top layer) patterns were imaged on the SOG film (intermediate layer), which was coated on a hard-baked i-line resist (bottom layer). The SOG film showed sufficient adhesion to the resist patterns, and superior resist profiles were imaged on the film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 636–640, 2003

Novel approach to form and pattern sol–gel polymethylsilsesquioxane-based spin-on glass thin and thick films

In this paper, the applications of sol–gel materials and process to semiconductor industry are introduced. Based on the sol–gel technique, the spin-on glass (SOG) fabrication techniques to realize thin and thick films are presented hereby. The thin films were patterned by liquid embossing techniques. For thick films, the film thickness can reach more than 200 μm. The whole process is a novel fabrication technique for thick SOG films, which can be performed at very low temperature without using molds. It is excluded from the original thermal deposition techniques required very high temperature or vacuum facilities. Furthermore, the requirement of the sol–gel process for equipments is simple and much less expensive. The desired microstructure can be obtained directly by organic solvent development after deep X-ray lithography (DXRL). Finally, the film structures were investigated by X-ray photoelectron spectroscopy (XPS), which shows that the films have the same characteristics of the thermal silicon dioxide after DXRL.

Direct Etching of Spin-on-Glass Films Exposed Using Synchrotron Radiation

In the direct etching of spin-on-glass (SOG) films exposed using synchrotron radiation (SR) in the soft X-ray region at room temperature, etching depth increased with the SR dose. The etching rate of SOG films with organic content was much higher than that of SOG films without organic content. X-ray photoelectron spectroscopy (XPS) observation showed that the etching mechanism of SOG films without organic content was mainly SiO desorption and that of SOG films with organic content was mainly SiO and oxygen desorption. A 2 µm line and space etching pattern was transferred to SOG films with good fidelity by SR exposure.

Thermo-Optic Switch using Fluorinated Silicon Oxide and Organic Spin-on-Glass Films

A thermo-optic switch in a thin-film optical waveguide was investigated. Fluorinated silicon oxide (SiOF) and organic spin-on-glass (SOG) films were used as core-layer and clad-layer, respectively, in the waveguide structure. The SiOF films were formed at 23#x00B0;C by a liquid-phase deposition (LPD) technique using a supersaturated hydrofluosilicic acid (H2SiF6) aqueous solution. Thermal coefficients of the refractive indices for LPD-SiOF and organic SOG films formed on silicon (Si) substrates were #x2212;4.0 #x00D7; 10#x2212;6/#x00B0;C, #x2212;60 #x00D7; 10#x2212;6/#x00B0;C at the wavelength of 632.8 nm, respectively. A high extinction ratio of 15 dB was obtained for this switch at the applied voltage of 12.8 V.