Si CH3 Bonds Research Articles

Investigating the Effect of Plasma Parameters on the Dielectric Constant of Sicoh Thin Films Grown by PECVD Using Dimethyldimethoxysilane

The demand for high-performance, low-power, and high-density semiconductor devices has led to the reduction in size of semiconductor chips, resulting in resistance-capacitance (RC) delay. To mitigate the RC delay, low dielectric constant (low-k) insulators have been developed, with the focus on developing new materials with lower dielectric constant. In this report, we present our investigation into the effect of electron density and temperature on the reduction of dielectric constant in SiCOH thin films, utilizing dimethyldimethoxysilane (DMDMS) as a variable with respect to pressure. Our results reveal that both electron density and temperature decline with increasing pressure due to localized electron kinetics and increased inelastic collisions between electrons and neutral species in the chamber, respectively. Our findings also show that the dielectric constant and refractive index of SiCOH thin films decrease at low electron density and temperature. Quadrupole mass spectroscopy reveals that CH3 radicals dissociate less at higher pressures, while Fourier transform infrared spectroscopy confirms an increase in Si-CH3 bonds in SiCOH thin films with increasing pressure. Our findings provide insights into the relationship between electron density and temperature and the dielectric constant of SiCOH thin films, which can contribute to the development of low-k insulators for high-performance semiconductor devices for applications such as big data, mobility, and the Internet of Things (IoT).

Influence of plasma parameters on low-k SiCOH film grown by plasma-enhanced chemical vapor deposition using dimethyldimethoxysilane

Here, we report the influence of the electron density and the electron temperature on the reduction of dielectric constant in the SiCOH thin film using dimethyldimethoxysilane (DMDMS) as a function of pressure. The measured electron density and electron temperature decreased as increasing the pressure. The decrease in the measured electron density with increasing pressure can be attributed to local electron kinetics. Moreover, the decreasing electron temperature is caused by increased inelastic collisions between electrons and neutral species in the chamber. It is identified that CH3 radicals are less dissociated from DMDMS molecular at higher pressure by a quadrupole mass spectroscopy. As increasing pressure, the increase of the Si–CH3 bonds in SiCOH thin films is confirmed by Fourier transform infrared spectroscopy. As a result, the dielectric constant and refractive index of the SiCOH films are reduced at low electron density and electron temperature.

Are Si–C bonds formed in the environment and/or in technical microbiological systems?

Organosiloxanes are industrially produced worldwide in millions of tons per annum and are widely used by industry, professionals, and consumers. Some of these compounds are PBT (persistent, biaccumulative and toxic) or vPvB (very persistent and very bioaccumulative). If organosiloxanes react at all in the environment, Si–O bonds are hydrolyzed or Si–C bonds are oxidatively cleaved, to result finally in silica and carbon dioxide. In strong contrast and very unexpectedly, recently formation of new Si–CH3 bonds from siloxanes and methane by the action of microorganisms under mild ambient conditions was proposed (in landfills or digesters) and even reported (in a biotrickling filter, 30 °C). This is very surprising in view of the harsh conditions required in industrial Si–CH3 synthesis. Here, we scrutinized the pertinent papers, with the result that evidence put forward for Si–C bond formation from siloxanes and methane in technical microbiological systems is invalid, suggesting such reactions will not occur in the environment where they are even less favored by conditions. The claim of such reactions followed from erroneous calculations and misinterpretation of experimental results. We propose an alternative explanation of the experimental observations, i.e., the putative observation of such reactions was presumably due to confusion of two compounds, hexamethyldisiloxane and dimethylsilanediol, that elute at similar retention times from standard GC columns.

Etch Characteristics of Low-K Materials Using CF3I/C4F8/Ar/O2 Inductively Coupled Plasmas

In this study, pulsed CF3I/C4F8/Ar/O2 inductively coupled plasmas have been studied for low-k etching, and the effects of CF3I addition to C4F8/Ar/O2 on the plasma characteristics and etch characteristics of low-k materials were investigated. The increased ratio of CF3I/(CF3I+C4F8) in the gas mixture increased CF3 radicals while decreasing CF2 radicals in the plasma, and which are related to the etching and polymerization, respectively. Therefore, the etch rates of SiCOH increased with increasing the CF3I ratio. However, the etch selectivity over an amorphous carbon layer and photoresist was the highest at the ratio of 0.5 because the CF2/F flux ratio from the plasma and the C/F ratio on the polymer layer were the highest at the CF3I ratio of 0.5. The SiCOH damage was decreased with increasing CF3I ratio and the SiCOH damage appeared to be very low, particularly when the CF3I ratio was ≥0.5 by showing low Si–CH3 bond loss, low F penetration, and a low surface roughness. Therefore, it is believed that, as opposed to the C4F8/Ar/O2 gas mixture only, mixing 50% CF3I into the C4F8/Ar/O2 gas mixtures resulted in not only a high etch selectivity over mask materials, but also a potentially reduced etch damage.

Synthesis of SiC films by Atmospheric Pressure Chemical Vapor Deposition using Dimethylisopropylsilane Polymeric Precursor

Abstract: Silicon carbide (SiC) thin films were deposited on Quartz, SiC, and GaAs substrates under a hydrogen (H2) ambient at 850°C using dimethylisopropylsilane [CH(CH3)2SiH(CH3)2] as a single molecular polymeric precursor by the atmospheric pressure chemical vapor deposition (APCVD) technique. Effects on the SiC films from variation of precursor to H2 flow ratio in the reactive chamber as well as those which resulted when vacuum or positive pressures are utilized during temperature ramping have been investigated. Detailed analysis of Fourier Transform Infrared Spectroscopy (FTIR) results indicate the formation of SiC at 850°C in accordance with residual Si-CH2, Si-CH3 and Si-O bonds. Confirmed by either X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) or Energy Dispersive Spectroscopy (EDS), results show that the produced SiC films are dense, rough surfaced, void-free, and consist of a crystalline core showing the presence of beta-SiC and small amounts of alphaSiC. Pre-experimental thermodynamic modeling provided the valuable insight that an increase of the precursor to direct H2 flow ratio would provide a decrease of unreacted carbon in the SiC matrix yielding higher quality SiC films. These simulations also have shown reasonable agreement with our experimental observations. Keywords: SiC thin Film, Polymeric Precursor, Chemical Vapor Deposition, Thermodynamic Modelling

In-Situ Imaging of a Light-Induced Modification Process in Organo-Silica Films via Time-Domain Brillouin Scattering.

We applied time-domain Brillouin scattering (TDBS) for the characterization of porogen-based organosilicate glass (OGS) films deposited by spin-on-glass technology and cured under different conditions. Although the chemical composition and porosity measured by Fourier-transform infrared (FTIR) spectroscopy and ellipsometric porosimetry (EP) did not show significant differences between the films, remarkable differences between them were revealed by the temporal evolution of the Brillouin frequency (BF) shift of the probe light in the TDBS. The observed modification of the BF was a signature of the light-induced modification of the films in the process of the TDBS experiments. It correlated to the different amount of carbon residue in the samples, the use of ultraviolet (UV) femtosecond probe laser pulses in our optical setup, and their intensity. In fact, probe radiation with an optical wavelength of 356 nm appeared to be effective in removing carbon residue through single-photon absorption processes, while its two-photon absorption might have led to the breaking of Si-CH3 bonds in the OSG matrix. The quantum chemical calculations confirmed the latter possibility. This discovery demonstrates the possibility of local modifications of OSG films with a nanometric resolution via nonlinear optical processes, which could be important, among other applications, for the creation of active surface sites in the area-selective deposition of atomic layers.

Hydrophobic Lightweight Cement with Thermal Shock Resistance and Thermal Insulating Properties for Energy-Storage Geothermal Well Systems.

This study assessed the possibility of using polymethylhydrosiloxane (PMHS)-treated fly ash cenospheres (FCS) for formulating a thermally insulating and thermal shock (TS)-resistant cementitious blend with calcium aluminate cement. To prevent FCS degradation in an alkaline cement environment at high temperatures, the cenospheres were pre-treated with sodium metasilicate to form silanol and aluminol groups on their surface. These groups participated in a dehydrogenation reaction with the functional ≡Si–H groups within PMHS with the formation of siloxane oxygen-linked M-FCS (M: Al or Si). At high hydrothermal temperatures of 175 and 250 °C, some Si–O–Si and SiCH3 bonds ruptured, causing depolymerization of the polymer at the FCS surface and hydroxylation of the raptured sites with the formation of silanol groups. Repolymerization through self-condensation between the silanol groups followed, resulting in the transformation of siloxane to low crosslinked silicon-like polymer as a repolymerization-induced product (RIP) without carbon. The RIP provided adequate protection of FCS from pozzolanic reactions (PR), which was confirmed by the decline in zeolites as the products of PR of FCS. Cements with PMHS-treated FCS withstood both hydrothermal and thermal temperature of 250 °C in TS tests, and they also showed improved compressive strength, toughness, and water repellency as well as decreased thermal conductivity. The lubricating properties of PMHS increased the fluidity of lightweight slurries.

Pore structure and thermal oxidation curing behavior of porous polymer derived ceramics with superhigh porosity fabricated by freeze casting

Porous ceramics with porosity up to 92.5 % have been successfully fabricated by freeze casting of polycarbosilane (PCS) solution. The effect of PCS concentration and thermal oxidation curing on the pore structure and compressive properties was investigated. Curing mechanism and thermodynamics were illuminated through analyzing the molecular structure, curing activation energy, and curing degree. Porous ceramics, mainly composed of SiC and a small amount of SiO2, have dendritic pore structure which well replicates the solidification morphology of camphene solvent. Results of FT-IR and Gaussian computation of PCS electron density show that Si–H and Si–CH3 bonds play a dominant role in thermal oxidation curing reaction. Both curing degree and ceramic yield increase with the increase in curing temperature and time. The curing degree of Si–H bond is close to 52 % and the corresponding ceramic yield is about 83 % when the porous PCS was cured at 200 °C for 90 min. Both polymer concentration and curing time have influences on the compressive strength of porous ceramics.

Improved charging phenomenon with a modified barrier structure for flexible displays fabricated on polyimide substrates

In a previous study, the authors investigated that abnormal Vth behaviour could occur due to polyimide charging when a voltage was applied to the gate in thin film transistors fabricated on polyimide substrates. The authors propose a barrier structure that could prevent this charging effect when fabricating flexible thin film transistors on polyimide substrates. The barrier layer was changed to an SiOCH/SiO2 double layer to reduce the influence of fluorine ions generated in PI by negative bias temperature stress. To confirm the effect of the SiOCH layer, Al/PI/SiO2/Al, Al/PI/SiOCH/SiO2/Al metal-insulator-metal capacitors were fabricated and electrical properties were measured. When bias stress was applied, changes in current and capacitance were observed only in the device with a single SiO2 barrier layer. In addition, it was confirmed through secondary ion mass spectrometry measurements that the Si–CH3 bonds in the SiOCH layer were replaced with Si–F bonds by the fluorine ions originating from PI. It was also verified that the abnormal behaviour of Vth did not occur after negative bias temperature stress of the thin film transistor fabricated using an SiOCH/SiO2 double layer.

Charging Compensation Layer on Polyimide for Enhanced Device Stability in Flexible Technology

In this paper, we propose a structure that prevents the charging effects that occur in devices fabricated on polyimide (PI) substrates. In general, when fabricating a device on a PI substrate, an inorganic barrier layer is first deposited to prevent penetration of oxygen and moisture. In this study, we confirmed that fluorine ions were induced from PI by bias stress and proposed a SiOCH/SiO2 double layer as a barrier to prevent charging. Then, Al/PI/SiO2/Al and Al/ PI/SiOCH/SiO2/Al metal–insulator–metal capacitors were manufactured. The capacitor characteristics before and after application of bias stress were verified through current–voltage (I–V) and capacitance–voltage (C–V), which are electrical characterization methods, and secondary ion mass spectrometry (SIMS), which is a physical analysis method. As the voltage increased, the capacitance and current of the Al/PI/SiO2/Al capacitor varied, but those of the Al/PI/SiOCH/SiO2/Al device did not change. Finally, SIMS analysis confirmed that the PI-derived fluorine ions replaced the Si–CH3 bonds within the SiOCH film with Si–F bonds, thereby preventing capacitance and current fluctuations.

Ligated aluminum cluster anions, LAln- (n = 1-14, L = N[Si(Me)3]2).

A wide range of low oxidation state aluminum-containing cluster anions, LAln- (n = 1-14, L = N[Si(Me)3]2), were produced via reactions between aluminum cluster anions and hexamethyldisilazane (HMDS). These clusters were identified by mass spectrometry, with a few of them (n = 4, 6, and 7) further characterized by a synergy of anion photoelectron spectroscopy and density functional theory (DFT) based calculations. As compared to a previously reported method which reacts anionic aluminum hydrides with ligands, the direct reactions between aluminum cluster anions and ligands promise a more general synthetic scheme for preparing low oxidation state, ligated aluminum clusters over a large size range. Computations revealed structures in which a methyl-group of the ligand migrated onto the surface of the metal cluster, thereby resulting in "two metal-atom" insertion between Si-CH3 bond.

Confined water radiolysis in aluminosilicate nanotubes: the importance of charge separation effects.

Imogolite nanotubes are potentially promising co-photocatalysts because they are predicted to have curvature-induced, efficient electron-hole pair separation. This prediction has however not yet been experimentally proven. Here, we investigated the behavior upon irradiation of these inorganic nanotubes as a function of their water content to understand the fate of the generated electrons and holes. Two types of aluminosilicate nanotubes were studied: one was hydrophilic on its external and internal surfaces (IMO-OH) and the other had a hydrophobic internal cavity due to Si-CH3 bonds (IMO-CH3), with the external surface remaining hydrophilic. Picosecond pulse radiolysis experiments demonstrated that the electrons are efficiently driven outward. For imogolite samples with very few external water molecules (around 1% of the total mass), quasi-free electrons were formed. They were able to attach to a water molecule, generating a water radical anion, which ultimately led to dihydrogen. When more external water molecules were present, solvated electrons, precursors of dihydrogen, were formed. In contrast, holes moved towards the internal surface of the tubes. They mainly led to the formation of dihydrogen and of methane in irradiated IMO-CH3. The attachment of the quasi-free electron to water was a very efficient process and accounted for the high dihydrogen production at low relative humidity values. When the water content increased, electron solvation dominated over attachment to water molecules. Electron solvation led to dihydrogen production, albeit to a lesser extent than quasi-free electrons. Our experiments demonstrated the spontaneous curvature-induced charge separation in these inorganic nanotubes, making them very interesting potential co-photocatalysts.

Low-k SiCOH Films Deposited with a Single Precursor 1,1,1,3,5,7,7,7 Octamethyl-3,5-Bis(trimethylsiloxy) Tetrasiloxane by Plasma Enhanced Chemical Vapor Deposition.

Low-dielectric-constant SiCOH films were deposited by plasma-enhanced chemical vapor deposition using 1,1,1,3,5,7,7,7-octamethyl-3,5-bis(trimethylsiloxy)tetrasiloxane (OMBTSTS) as a single precursor, and the characteristics were investigated. The relative dielectric constant (k) of the SiCOH films declined gradually from 3.57 to 1.90 with decreasing plasma power. The film with the lowest k, deposited at the lowest power of 10 W, showed the lowest leakage current density, with adequate mechanical strength (hardness: 0.98 GPa and elastic modulus: 8.56 GPa) for application in multilevel semiconductor interconnects. The chemistry of the OMBTSTS films was characterized by Fourier transform infrared spectroscopy to study the relation between the chemical and dielectric properties. The dielectric properties, such as the k value and leakage current density, could be explained by a quantitative relation between the Si-O stretching bond and hydrocarbon-related bonds, such as CH₃ and Si-CH₃ bonds, with lower polarizability in the SiCOH film. The refractive index, which is directly linked to the density of the film, was also investigated by ellipsometry. We consider OMBTSTS a promising candidate as a single precursor for fabricating low-k SiCOH films in the plasma-enhanced chemical vapor deposition system.

Si-C(sp3) bond activation through oxidative addition at a Rh(i) centre.

An easy, direct and room temperature silicon-carbon bond activation is reported. The reaction of [RhCl(coe)2]2 with the silane Si(Me)2(o-C6H4SMe)2 in the presence of an halide extractor provokes a Si-CH3 bond cleavage yielding a cationic silyl-methyl-Rh(iii). In contrast, if the reaction is performed using the Rh(i) bis-alkene dimers, [RhCl(cod)]2 or [RhCl(nbd)]2, the Si-CH3 bond activation does not occur.

Investigations on the blue luminescence enhancement of organically modified SiO2-TiO2-PDMS glass matrix

A novel class of Organically Modified Silicates (ORMOSILs) has been synthesized by non-hydrolytic sol–gel method at low temperature, incorporating the organic polymer, polydimethylsiloxane (PDMS) in tetraethylorthosilicate (TEOS) and titanium (IV) isopropoxide (TIP) based glassy gels. The structural modification of pure SiO2-TiO2 matrix by PDMS and its effects on optical and photoluminescence spectroscopy were investigated in detail. XRD pattern and HR-TEM images confirm the structural modification of the SiO2-TiO2-PDMS glass matrix. The formation of TiO2 nanocrystals of about 5–6 nm in size, embedded in the amorphous SiO2 matrix, has been confirmed from HR-TEM and SAED patterns. The TG–DTA analysis revealed the improved thermal stability of the ORMOSIL and the DSC analysis shows that its glass transition temperature decreases to 55.23 °C. A distinctive enhanced blue emission at 470 nm has been observed in photoluminescence studies of the prepared samples. FT-IR studies confirmed the formation of Ti–O–Ti, Si–O–Ti and Si–CH3 bonds by the PDMS modification of pure SiO2-TiO2 glass. These bonds and TiO2 nanocrystals embedded in the amorphous glass matrix together play an important role in the photoluminescence properties of the ORMOSIL. SiO2-TiO2 matrix has a luminescence quantum efficiency of 22.2% and the PDMS incorporation has increased the quantum efficiency to 55.8%. Thus SiO2-TiO2-PDMS ORMOSIL can be used as an efficient blue emitting host matrix for WLED fabrication.

Physical Characteristics of Soft Tissue Phantom from Silicone Rubber Based Vulcanization System

Phantom from silicone rubber base material has been synthesized without glycerin and with additional glycerin of 10%, 20%, 30% and 40%. The type of Silicone rubber used is Room Temperature Vulcanized (RTV) 52 with a vulcanization system at room temperature. The concentration of catalyst is 5% from silicone rubber. Sample has characterized by using physical testing, Fourier Transform Infra Red (FTIR) and elastic modulus measurements. Physical testing result shows that phantoms have low degradation and can be applicated in a long time. FTIR data shows a phantom structure is poly (dimethylsiloxane) that has Si-CH3 bond at wavenumber 1261 cm-1 and 802 cm-1 and the Si-O-Si siloxane group at wavenumber 1024 cm-1. The elastic modulus values of phantom are 244 kPa for without glycerin, 210 kPa for 10% glycerin and 126 kPa for 20% glycerin. From the data indicated phantoms has range of the liver elastic modulus value at 0.6-4000 kPa. It means that phantom can be used as a substitute for the soft tissue of the human liver.

Atmospheric-pressure silica-like thin film deposition using 200 kHz/13.56 MHz dual frequency excitation

Atmospheric pressure plasma enhanced chemical vapour deposition was used to synthesize silica-like thin films on polyethylene 2, 6 naphthalate substrate with hexamethyldisiloxane as the precursor and Ar/O2/N2 mixture as the working gas. A dual frequency (DF) excitation consisting of 200 kHz and 13.56 MHz frequencies was employed as the plasma source. The results have shown that compared to the single low frequency discharges, the DF excitation helps to improve plasma uniformity with less filaments. This could help to reduce the macro-defects and therefore to improve the permeation performance of the barriers. Besides, due to the increased electron density and gas temperature, the DF excitation demonstrates a more efficient breaking of Si–CH3 bonds and therefore more oxidized structures of the deposited silica-like thin films.

Etch Damage Reduction of Ultra Low-k Dielectric By Using Pulsed Plasmas

To reduce interconnect resistance and capacitance delay, the dielectric material with increased porosity is used in recent interconnection for lower dielectric constant. However, it is difficult to use highly porous low-k materials at the narrowest pitch because it is easily damaged during plasma etching processes. During plasma etching processes, plasma ions, reactive radicals, and VUV photon from the plasma tend to break Si-CH3 bonds in the low-k materials and change the material hydrophilic. This makes the damaged dielectric material to be bonded with moisture and makes dielectric constant to be increased and, eventually, it degrades RC time delay. In this study, as one of the plasma induced damage reduction methods in the etching of porous low-k dielectric, RF pulsed plasma methods have been investigated by using a dual frequency CCP system. RF pulsed plasmas generated lower energy ions compared to continuous wave plasmas and showed reduced damaged layer compared to the conventional continuous wave plasma etching. Porous SiCOH dielectric with a patterned TiN hard mask etched using RF pulsed plasmas and showed more anisotropic etching profile with less sidewall damage, which was estimated by the thickness loss of sidewall low-k material after dipping into a diluted HF solution. The results demonstrated that the RF pulsed plasma etching process of ultra low-k dielectric can improve RC delay related with plasma damage for next interconnect technology.

Impact of VUV photons on SiO2 and organosilicate low-k dielectrics: General behavior, practical applications, and atomic models

This paper presents an in-depth overview of the application and impact of UV/VUV light in advanced interconnect technology. UV light application in BEOL historically was mainly motivated by the need to remove organic porogen and generate porosity in organosilicate (OSG) low-k films. Porosity lowered the film's dielectric constant, k, which enables one to reduce the interconnect wiring capacitance contribution to the RC signal delay in integrated circuits. The UV-based low-k film curing (λ > 200 nm) proved superior to thermal annealing and electron beam curing. UV and VUV light also play a significant role in plasma-induced damage to pSiCOH. VUV light with λ < 190–200 nm is able to break Si-CH3 bonds and to make low-k materials hydrophilic. The following moisture adsorption degrades the low-k properties and reliability. This fact motivated research into the mechanisms of UV/VUV photon interactions in pSiCOH films and in other materials used in BEOL nanofabrication. Today, the mechanisms of UV/VUV photon interactions with pSiCOH and other films used in interconnect fabrication are fairly well understood after nearly two decades of research. This understanding has allowed engineers to both control the damaging effects of photons and utilize the UV light for material engineering and nanofabrication processes. Some UV-based technological solutions, such as low-k curing and UV-induced stress engineering, have already been widely adopted for high volume manufacturing. Nevertheless, the challenges in nanoscaling technology may promote more widespread adoption of photon-assisted processing. We hope that fundamental insights and prospected applications described in this article will help the reader to find the optimal way in this wide and rapidly developing technology area.

Surface course in Rochow reaction: First-principle study

The first-principle method is employed to study the Rochow reaction. The Cu atom stably adsorbs on the Si (1 1 1) surface. The CCl bond of CH3Cl was broken by the SiCu bond only when the two bonds vertically close together. The Cu adatom triggers Rochow reaction, and seriously is an initiator. The main catalysis ability comes from SiCH3 or SiCl bonds. The Rochow reaction contains two stages. The first one is that the Cu adatome triggers reaction. The second one is that the SiCH3 and SiCl bonds catalyze the CCl bond to break and to form new SiCH3 and SiCl bonds.