Borosilicate Films Research Articles

Radiation response of cubic mesoporous silicate and borosilicate thin films

Abstract The radiation response has been studied of cubic mesoporous silicate and borosilicate thin films having different boron contents prepared using the block copolymer template Brij 58 and the dip coating technique. The degree of pore ordering of the films was analysed using low-angle X-ray diffraction and film thickness measured by X-ray reflectivity. For films calcined at 350 °C, the incorporation of boron resulted in a reproducible oscillatory variation in the d-spacing and intensity of the primary reflection as a function of boron content. A clear peak was observed in the d-spacing at 5–10 mol% boron incorporation. For borosilicate films of a given composition an overall suppression of d-spacing was observed as a function of aging time relative to films that did not contain boron. This was ascribed to a slow condensation process. The films were irradiated in pile with neutrons and with iodine ions at energies of 180 keV and 70 MeV. Neutron irradiation of the silicate thin films for periods up to 30 days and aged for 400 days resulted in little reduction in either d-spacing or intensity of the primary low-angle X-ray reflection indicating that the films retained their mesopore ordering. In contrast borosilicate films for which the B (n, α) reaction was expected to result in enhanced displacement damage showed much larger variations in X-ray parameters. For these films short irradiation times resulted in a reduction of the d-spacing and intensity of the primary reflections considerably beyond that observed through aging. It is concluded that prolonged neutron irradiation and internal α irradiation have only a small, although measurable, impact on mesoporous borosilicate thin films increasing the degree of condensation and increasing unit cell contraction. When these borosilicate films were irradiated with iodine ions, more profound changes occurred. The pore ordering of the films was significantly degraded when low energy ions were used. In some cases the degree of damage was such that no low-angle reflection could be observed. This degradation of pore ordering was confirmed in scanning electron microscopy images of the irradiated films.

Study of thermal effects on the structure of thin-film borosilicate coatings by ellipsometry, and X-ray diffraction

The paper presents the results of studying structural changes in the state of a synthetic borosilicate shell during heat treatment. Analysis of the structural-phase change in a thin-film borosilicate coating, subjected to heat treatment in the temperature range from 100 to 500°C, is carried out using an ARLX’TRA (Switzerland) X-ray diffractometer. A change in the ellipsometric parameters of the material is observed in the temperature range 100–500°C, which is accompanied by a continuous increase in the thickness of the thin film coatings (from 34 nm at 100°C to 38 nm at 300°C and to 49 nm at 500°C) and the refractive index of light. These changes are thought to be caused by structural-phase transitions and crystallization of the borosilicate film.

Thermo‐Oxidative Stability of Polymer‐Derived Si‐B‐C Ceramics

Si‐B‐C ceramics with different elemental compositions and microstructures were prepared by the pyrolysis of an o‐carborane‐containing poly(silylene‐arylacetylene) (CB‐PSA) thermoset at 1000°C, 1200°C, 1300°C, and 1450°C. The thermo‐oxidative stability of the ceramics was investigated by tracing the weight loss of ceramics during the isothermal oxidation at 800°C, 1000°C, and 1200°C under dry oxygen. The chemical bonding states of the ceramics before oxidation and the elemental compositions of the ceramics after oxidation were analyzed by X‐ray photoelectron spectroscopy (XPS). The surface morphologies of the ceramics after oxidation were recorded using scanning electron microscopy (SEM). The results show that the Si‐B‐C ceramic prepared at 1450°C produces an integral borosilicate film on the surface of the ceramics when oxidized at both 1000°C and 1200°C and exhibits better oxidation resistance than the other Si‐B‐C ceramics prepared at 1000°C, 1200°C, and 1300°C. Oxidation temperatures, elemental compositions, and crystallites of the Si‐B‐C ceramics are found to influence the formation of the borosilicate films which plays an important role in the thermo‐oxidative stability of the ceramics.

High-temperature oxidation of ZrB2–SiC and ZrB2–SiC–ZrSi2 ceramics up to 1700°C in air

The high-temperature oxidation of ZrB2–SiC and ZrB2–SiC–ZrSi2 ceramics up to 1700°C in air has shown their high corrosion resistance. A five-stage nonisothermal oxidation mechanism is established for the samples when heated at a rate of 20°C/min: 1) oxygen adsorption–desorption; 2) formation of ZrO2 and B2O3 oxides; 3) formation of α-SiO2 cristobalite and ZrSiO4 zircon; 4) formation of amorphous SiO2; and 5) formation of upper protective borosilicate film with ZrSiO4 inclusions at less than 40 wt.% SiC. It is shown that small ZrSi2 admixtures (<6–8 wt.%) substantially slow down the oxidation of the ceramics in initial heating stages due to diffusion-hindered formation of ZrO2 and B2O3. The 67.3 wt.% ZrB2–26 wt.% SiC–6.7 wt.% ZrSi2 ceramics are characterized by the highest corrosion resistance since their upper scale layer represents borosilicate glass stabilized with ZrO2 (tetragonal) inclusions.

Acceptor-related low-energy photoluminescence from boron-doped Si nanocrystals

Boron (B) doped Si nanocrystals (Si-ncs) dispersed in hydrofluoric (HF) acid solution are prepared by dissolving borosilicate films containing B-doped Si-ncs in HF solution. We find that the etching rate of B-doped Si-ncs is much smaller than that of undoped Si-ncs. The difference of the etching rate allows us to extract only doped Si-ncs in the mixture of doped and undoped Si-ncs and observe the photoluminescence (PL) due to the transition from the conduction band to the acceptor state. The PL was very broad with the maximum around 1.15 eV. From the analysis of the PL data obtained for the samples prepared under different conditions and different etching time, preferential doping sites of B atoms are estimated. The data suggests that B-doped Si-ncs consists of intrinsic cores and heavily B-doped shells.

Fabrication and properties of ZrB 2–SiC–BN machinable ceramics

ZrB 2–SiC–BN ceramics were fabricated by hot-pressing under argon at 1800 °C and 23 MPa pressure. The microstructure, mechanical and oxidation resistance properties of the composite were investigated. The flexural strength and fracture toughness of ZrB 2–SiC–BN (40 vol%ZrB 2–25 vol%SiC–35 vol%BN) composite were 378 MPa and 4.1 MPa m 1/2, respectively. The former increased by 34% and the latter decreased by 15% compared to those of the conventional ZrB 2–SiC (80 vol%ZrB 2–20 vol%SiC). Noticeably, the hardness decreased tremendously by about 67% and the machinability improved noticeably compared to the relative property of the ZrB 2–SiC ceramic. The anisothermal and isothermal oxidation behaviors of ZrB 2–SiC–BN composites from 1100 to 1500 °C in air atmosphere showed that the weight gain of the 80 vol%ZrB 2–20 vol%SiC and 43.1 vol%ZrB 2–26.9 vol%SiC–30 vol%BN composites after oxidation at 1500 °C for 5 h were 0.0714 and 0.0268 g/cm 2, respectively, which indicates that the addition of the BN enhances oxidation resistance of ZrB 2–SiC composite. The improved oxidation resistance is attributed to the formation of ample liquid borosilicate film below 1300 °C and a compact film of zirconium silicate above 1300 °C. The formed borosilicate and zirconium silicate on the surface of ZrB 2–SiC–BN ceramics act as an effective barriers for further diffusion of oxygen into the fresh interface of ZrB 2–SiC–BN.

Investigation of the physicochemical properties, structure, and composition of nanosized borosilicate films prepared by the sol-gel method

This paper reports on the results of investigations into the specific features of the deposition of hybrid organic-inorganic borosilicate films prepared by the sol-gel method for the use in the planar technology of microelectronics. In order to modify the properties of the borosilicate films, a number of water-soluble hydroxyl-containing oligomers (with different molecular topologies and different molecular weights from 300 to 5100 g/mol) are introduced into the sol-gel system. The effect of these polyols on the sol viscosity, the thickness, and the surface morphology of the synthesized films is revealed by viscometry, ellipsometry, optical microscopy, atomic-force microscopy, and thermal analysis. These films are designed for the use as sources for boron diffusion into silicon in order to fabricate heavily doped diffusion layers with a dopant concentration of (5–7) × 1020 cm−3. The depth of occurrence of diffusion layers is approximately equal to 4 μm.

Anodic bonding of silicon to silicon wafers coated with aluminium, silicon oxide, polysilicon or silicon nitride

Silicon to silicon wafer bonding by use of sputter deposited borosilicate film is a promising mounting method for micromechanical components. This method has been developed to bond 3 inch borosilicate sputter coated silicon wafers to silicon wafers coated either with aluminium, silicon dioxide, polysilicon or silicon nitride. The bondings were performed at temperatures ranging from 300 to 400 °C which enables application of this technique on metallised devices. The bond strengths of the different samples bonded with these methods are all in the region 5–25 MPa. Some samples were exposed to water for 300 h to test the media compatibility, and some samples were thermal shock tested by repeatedly exposing to liquid nitrogen. No significant difference in bond strength has yet been verified statistically for the different sample configurations. We have also observed good correlation between destructive bond strength testing and non-destructive infrared microscope inspection.

Coating Films of 20B2O3·80SiO2 by the Sol‐Gel Method

Alkali‐free borosilicate films of 20B2O3. 80SiO2 (in mol%) have been prepared by the sol‐gel method. The transparency of these films was found to be very sensitive to the humidity of the atmosphere during the coating process. Transparent films were obtained only in a dry atmosphere. Measurements of IR spectra and load at scratch showed that these films were densified above 600°C.

A New Technique for Low Concentration Diffusion of Boron into Silicon

A new technique is proposed for doped-oxide diffusion of boron into silicon, providing a controlled surface concentration in a wide range from 1015 to 1020 cm-3. The principle is based on our finding that if the source borosilicate film deposited is heat-treated in an NH3 ambient prior to the drive-in step, the transfer of boron into silicon is remarkably suppressed. The concentration of boron diffused in silicon is strongly dependent on the temperature and/or time of the NH3-heat-treatment. It is also found that an undoped SiO2 or Si3N4 film deposited on the source film works as a mask against the NH3 ambient. As a result, a simultaneous local diffusion of boron can be performed from a single film source to plural regions where different boron profiles are desired.

Vickers Microhardness Characterization of Sintered Borosilicate Films

The application of Vickers microhardness to glass surfaces has been reviewed, and despite differences of opinion as to its theoretical significance, it is judged useful for engineering applications. The technique has been applied to the study of sintered films of borosilicate glass on alumina substrates. The range of glaze thickness and load magnitude for which the hardness remains unchanged is defined. The effect of the degree of sintering (i.e., extent of densification), degree of phase separation, and aging of the HF etched surface on the microhardness have been measured. Hardness can also be used to detect surface stress which occurs in the region of glass‐metal interfaces.

Infrared Absorption of Chemical Vapor Deposited Borosilicate Glass Films

Diffusion sources of high‐purity borosilicate films on silicon have been studied by infrared absorption over the full range of glass compositions. The relative strengths of the B‐O and Si‐O bands in the mixed glasses can be used as a monitor of the boron content of the films. The B‐O absorption bands for glasses of high boron content show aging effects in moist air.

Chemical Vapor Deposition of Silicate Glasses for Use with Silicon Devices: I . Deposition Techniques

Compositions synthesized include borosilicates, phosphosilicates, aluminosilicates, aluminoborosilicates, and some zinc glasses. The compositions containing aluminum or zinc were prepared by simultaneous oxidation of the hydrides and trimethyl aluminum or diethyl zinc vapor. The deposition temperatures were in the 300°–500°C range. The effects of system variables on the deposition rate and composition of borosilicate films obtained from silane, diborane, and oxygen were examined in detail. Variables investigated included carrier gas and hydride flow rates, silane/diborane and oxygen/hydride ratios, deposition time and temperature, and reactor geometry.

Chemical Vapor Deposition of Silicate Glasses for Use with Silicon Devices: II . Film Properties

Chemical, dielectric, thermal, and optical properties of glass films synthesized by chemical vapor reactions from the hydrides are discussed. The binary borosilicate glasses deposited at low temperature from silane, diborane, and oxygen require a thermal densification to approach bulk glass properties. The rate of densification in the temperature range of 770°–800°C is very rapid but water vapor has an accelerating influence, allowing densification at reasonable rates at temperatures as low as 450°C. The thermal expansion match with silicon was sufficiently close to allow the crack‐free coating of wafers with 12µ of glass. Borosilicate films of 5µ thickness on silicon withstood severe thermal shock, temperature cycling, moisture penetration, and corrosion resistance tests. Densified borosilicate of typical compositions had a dielectric constant of 3.8–4.1 and a dissipation factor at 103 Hz of 0.10–0.15. The d‐c dielectric field strength sustained by MIS capacitors made from 1µ thick densified films measured before and after a 1‐yr exposure to room air, was . The properties of vapor‐deposited phosphosilicate glasses and of glasses containing the oxides of aluminum and zinc are briefly described.

Infrared Absorption of Borosilicate Films Prepared by SiH4-B2H6-O2 and -NO2 Systems

Infrared Absorption of Borosilicate Films Prepared by SiH4-B2H6-O2 and -NO2 Systems

The oxidation resistance of alloys of zirconium boride with molybdenum disilicide

A study was made of the oxidation of pure zirconium boride and alloys of zirconium boride with molybdenum disilicide-(ZrB1.9)23MoSi1.1 and (ZrB1.7)13MoSi1.2-obtained by sintering a mixture of zirconium boride with 5 and 10% molybdenum disilicide. The rate of oxidation was determined from the time dependences of specimen weight and oxide film thickness. On the basis of the kinetic oxidation curves and microstructural analysis, conclusions are drawn regarding the nature of the resultant oxide films. Alloys of zirconium boride with molybdenum disilicide have high oxidation resistance at up to 1550°C as a result of the formation of a borosilicate film on the surface.