SiO2 Wafer Research Articles

Negative charge injection to a wafer in a pulsed two-frequency capacitively coupled plasma for oxide etching; diagnostics by emission-selected computerized tomography

In order to develop charging-free plasma processing, we investigated the function of negative charge injection to a SiO2 wafer, during etching in a pulsed two-frequency capacitively coupled plasma under various external conditions in CF4/Ar at low pressures, by using emission-selected computerized tomography. The formation of a negatively-charged layer by an excess negative charge in the interface close to the wafer and the degree of acceleration of negative charges were experimentally estimated through the spatiotemporal characteristics of the net excitation rate of the short-lived Ar(2p1) used as a probe. A bias pulse operation with a single positive component at the wafer during the off-phase of very high frequency (100 MHz) plasma production resulted in the most efficient formation of the negatively-charged layer close to the wafer. The influence of the external plasma conditions on the negatively-charged layer is observed in detail.

Mechanochemical Synthesis of Nano-Sized CeO<sub>2</sub> and its Application for CMP Slurry

Nano-crystalline CeO2 was synthesized by the mechanical milling and subsequent heat-treatment from the mixture of Ce(OH)4 as precursor, and NaCl as diluent. The diluent provided diffusion barrier during milling and heat-treatment, which was easily dissolved out by deionized water. The size of crystallite and the strain variance of CeO2 were depended on the temperature and heat-treatment time: increased with the temperature (400~700oC) and time (1~24 hours) increasing, and saturated near at 20nm in size owing to the densification of diluent. The synthesized nano-crystalline CeO2 powder was applied as an abrasive in CMP (Chemical Mechanical Planarization) slurry. When blanket-type SiO2 and Si3N4 wafers were polished with the slurries, the removal rates (RR) of SiO2 and Si3N4 wafers and selectivities (RRSiO2/RRSi3N4) were influenced by synthetic condition of abrasive, the suspension stability and the pHs of slurries.

Negative charge injection to a positively charged SiO2 hole exposed to plasma etching in a pulsed two-frequency capacitively coupled plasma in CF4/Ar

As microchips become smaller, the threat of damage to the device elements of Si semiconductors by charging during plasma etching will become significant. It will be of first importance to establish a plasma-etching technique that does not involve charging, i.e., “charging-free plasma processing.” Here, we utilize the effect of negative charge acceleration under a double layer in order to neutralize the charge inside a microstructure exposed to plasma etching. We have constructed a dual measurement system consisting of an emission in an interface and a contact hole charging on a SiO2 wafer during etching in two-frequency capacitively coupled plasma (2f-CCP) in CF4/Ar and pure Ar. A reduction in charging voltage is measured in the pulsed operation both of the plasma power source and of the wafer bias in the 2f-CCP in electronegative gases, CF4/Ar.

A liftoff technique for molecular nanopatterning.

For quantum-dot cellular automata molecular electronic devices, one of the fundamental tasks is to arrange the molecules on a surface in a controlled manner. In this report, we discuss a molecular lift off technique to form nanopatterns toward the development of molecular circuits. In our molecular lift off technique, we use electron beam lithography to form nano-trenches on a polymethylmethacrylate (PMMA) film on a SiO2 wafer. This wafer is soaked in a Creutz-Taube ion [(NH3)5Ru(pyrazine)Ru(NH3)5](o-toluenesulfonate)5 (CT5) aqueous solution. After residual PMMA removal, atomic force microscopy is used to investigate the resulting surface. Thirty-five nanometer CT5 lines are demonstrated on a SiO2 surface. Compared with other molecular nanopatterning techniques, ours is both economical and capable of high-resolution.

Selective Growth of Aligned Carbon Nanotubes on a Silver-Patterned Substrate by the Silver Mirror Reaction

It was found that carbon nanotubes prepared by the pyrolysis of iron(II) phthalocyanine (FePc) can selectively grow on a SiO2 surface when the SiO2 wafer is patterned by silver. A combination of the micro-contact printing (μCP) technique and chemical reaction (classical silver tollens reaction, also called silver mirror reaction) has been applied to generate a silver pattern with micro/nanoscale resolution on a quartz glass substrate (silver selectively deposits on hydrophilic regions), and an aligned carbon nanotubes (CNTs) pattern with the same resolution can be fabricated by the pyrolysis of FePc on the basis of the selective growth. This new method represents a great advantage of controlled fabrication of a micro/nanoscale aligned CNT pattern on a conducting surface (silver) by combination of soft-lithography and chemical approach for various device applications, requiring high-resolution pattern and conducting surface.

Phosphanstabilisierte Silber(I)–Carboxylate: Synthese und Verwendung in der Silber-CVD

The synthesis of the silver(I)–carboxylate complexes [(R′ 3P) n AgO 2CR] ( n=1, R′= n Bu: 3a, R=CF 3; 3b, R=C 2F 5; R′=C 6H 4CH 2NMe 2-2: 3c, R=CF 3; 3d, R=C 2F 5; n=2, R′= n Bu: 4a, R=CF 3; 4b: R=C 2F 5) succeeds, when [AgO 2CR] ( 1a, R=CF 3; 1b, R=C 2F 5) is reacted with n equivalents of PR′ 3 ( 2a, R′= n Bu; 2b, R′=C 6H 4CH 2NMe 2-2) ( n=1, 2); the yield amounts to 83–98%. Complexes 3 and 4 can be used for the deposition of silver on titaniumnitride-coated SiO 2-wafers by the chemical vapour deposition (CVD) process, which could be shown by applying 4a as suitable precursor. REM studies show that closed silver layers were formed with a silver particle size between 50 and 100 nm.

Intermittent chemical vapor deposition of thick electrically conductive diamond-like amorphous carbon films using i-C4H10/N2 supermagnetron plasma

Electrically conductive diamond-like amorphous carbon (DAC) films with nitrogen (DAC:N) were deposited on Si and SiO2 wafers using the i-C4H10/N2 supermagnetron plasma chemical vapor deposition (CVD) method. Resistivity and hardness decreased with increase of upper electrode rf power (UPRF) under constant lower electrode rf power (LORF). Film thickness increased linearly to over 0.3 μm with deposition time via intermittent deposition. The film exhibited good adhesion to the substrate. Low-resistance thick films were deposited using alternating multilayer CVD at UPRF/LORFs of 1 kW/1 kW and 300 W/300 W. In the deposited alternating multiple layers, resistivity significantly decreased with the increase of H layer (1 kW/1 kW) thickness, and film thickness significantly increased with the increase of L layer (300 W/300 W) thickness. By the deposition of H/L multiple layers, a film of 2.1 μm thickness and 0.14 Ω cm resistivity was obtained.

Cr/Sc Multilayer Mirror for Soft X-ray

We have fabricated Cr/Sc multilayer mirrors for the two wavelengths of 3.37 (C VI 1s-2p emission) and 4.47 (C Kα) nm in the soft X-ray region. The deposition was performed by using an uhv r.f. sputtering system on flat SiO2 wafers. The multilayers were characterized by the grazing incidence X-ray reflectivity method with Cu-Kα radiation and the fitting calculation. An analysis by this method and section-TEM confirmed the regular periodicity of the multilayer. The reflectivity for soft X-rays was measured by synchrotron radiation at UVSOR facility. The reflectivity of the Cr/Sc multilayer for a wavelength of 3.37 nm was 10.4 % at an incident angle of 60 o. This multilayer had 21.7 % reflectance for 3.16-nm X-ray at 62.5 o. Also the reflectivity of another Cr/Sc multilayer with a carbon layer for C-Kα radiation was 2.45 % at the angle of 30 o.

XPS surface analysis of monocrystalline silicon solar cells for manufacturing control

X-ray photoelectron spectroscopy (XPS) has been applied to surfaces of silicon wafers in the different stages of the assembly line for large-scale monocrystalline silicon solar cell manufacturing (ISOFOTON, Malaga, Spain). XPS results have shown that a considerable amount of carbon is present on the pyramidal-textured monocrystalline silicon surface. This amount decreases slightly but is still present after the process of phosphor diffusion ( p − n junction), as well as after subsequent calcination in humid air for SiO2 film formation (passivation). This amount of carbon may be buried during the process of CVD coating an anti-reflection TiO2 film. After calcination of the film in order to obtain the TiO2 rutile phase, an even higher amount of carbon is detected on the TiO2 anti-reflection coating surface. This in- dicates that not all organics from the tetra-isopropile ortho- titanate (TPT) precursor were released from the film. Fur- thermore, in this case phosphor is found in excess on the SiO2 wafer surface (dead layer) and also on the rutile TiO2 surface, indicating that an extra phosphor diffusion from the bulk silicon through the TiO2 film has taken place during cal- cination. These results demonstrate how thermal treatments applied in the solar cell manufacturing assembly line can influence and may change the intended compositional distri- bution. These treatments may also introduce defects that act as recombination centres for charge carriers in the solar cell device.

Supermagnetron plasma chemical vapor deposition and qualitative analysis of electrically conductive diamond-like amorphous carbon films

Using the i-C4H10/N2 supermagnetron plasma chemical vapor deposition method, electrically conductive diamond-like amorphous carbon (DAC) films with nitrogen (DAC:N) were formed on Si and SiO2 wafers. Resistivity and hardness were measured as a function of N2 concentration, rf power, total gas pressure, and wafer stage temperature. With an increase in the N2 concentration (up to 70%), rf power, and wafer stage temperature, DAC:N film resistivity decreased. Fourier transform infrared spectroscopy measurements revealed that an increase in electrical conductivity was attributed to the creation of C–N, C≡N, and N–H bonds in DAC:N films. By preheating the wafers using H2-plasma cleaning, the resistivity of the DAC:N film decreased with an increase in H2-plasma rf power. Using a preheated wafer, the lowest resistivity of 0.034 Ω cm was obtained at an N2 concentration of 65% and upper- and lower-electrode rf powers of 1 kW/1 kW.

Effect of surface roughness and subsurface damage on grazing-incidence x-ray scattering and specular reflectance

Grazing-incidence specular reflectance and near-specular scattering were measured at Al-K(alpha) (1.486-keV, 8.34-?) radiation on uncoated dielectric substrates whose surface topography had been measured with a scanning probe microscope and a mechanical profiler. Grazing-incidence specular reflectance was also measured on selected substrates at the Cu-K(alpha) (8.047-keV, 1.54-?) wavelength. Substrates included superpolished and conventionally polished fused silica; SiO(2) wafers; superpolished and precision-ground Zerodur; conventionally polished, float-polished, and precision-ground BK-7 glass; and superpolished and precision-ground silicon carbide. Roughnesses derived from x-ray specular reflectance and scattering measurements were in good agreement with topographic roughness values measured with a scanning probe microscope (atomic force microscope) and a mechanical profiler that included similar ranges of surface spatial wavelengths. The specular reflectance was also found to be sensitive to the density of polished surface layers and subsurface damage down to the penetration depth of the x rays. Density gradients and subsurface damage were found in the superpolished fused-silica and precision-ground Zerodur samples. These results suggest that one can nondestructively evaluate subsurface damage in transparent materials using grazing-incidence x-ray specular reflectance in the 1.5-8-keV range.

Sol-gel thin films of BaFe12O19 from chemically modified alkoxide precursors

Homogeneous BaFe12O19 (BaM) thin films have been prepared by the dip-coating technique on microscope slides and SiO2 wafers using barium and iron alkoxides as precursors, and diethanolamine as a modifier. In order to optimise the coating conditions, the influence of the alkoxide, water and modifier on the sol viscosity, thickness and appearance of the Fe2O3 films has been investigated. For comparison of the crystallisation and magnetic properties, powders of the same composition as the films have been also prepared by the sol-gel method. The BaM phase appears after annealing at 650°C for 6 hours. The BaM film and powder, heated at 850°C for 6 hours, give coercive force of about 3000 and 5500 Oe, respectively.

Study of particulate formation and its control by a radio frequency power modulation in the reactive ion etching process of SiO2 with CF4/H2 plasma

Particulate formation in the reactive ion etching process of SiO2 with a CF4/H2 plasma was studied with the laser light scattering (LLS) method. The LLS onset time decreases drastically as the hydrogen percentage increases which indicates that the particulate formation was stimulated by the increase of the unsaturated fluorocarbon species as a result of the hydrogen addition. The onset time was also dependent on the substrate material. The measured onset time with a Si wafer was shorter than that with a SiO2 wafer. The onset time decreases very rapidly with the increase of the radio frequency (rf) power. A decrease of the LLS peak intensity was observed with the square wave modulation process of rf power. The change of the etch rate and the LLS peak intensity according to the change of the duty ratio shows that the optimal process condition, which satisfies high selectivity, high etch rate, and low particulate growth level, can be obtained with the rf modulation method. In the rf modulation process, both an increase in the off period and a decrease in the on period resulted in a decrease of the LLS signal in the particulate trap. It was observed that a change in the off period has a more pronounced effect on the change of the LLS signal intensity.

Optical emission diagnostics for contact etching in Applied Materials Centura HDP 5300 etcher

This article reports the use of an optical emission diagnostic as an in situ monitor of the photoresist etch rate during contact etch in a commercial, hot wall high density plasma reactor. The chamber was conditioned by prior photoresist etch and postetch oxygen clean to achieve reproducible conditions. The etch rate of photoresist and thermal oxide was measured, along with the optical emission observed for Si, SiO2 and photoresist wafers. With the rf bias power fixed at 600 W (125 mm wafers), the chamber roof temperature (240–260 °C) and source power (2350–2800 W) were varied in an experimental array to produce a range of photoresist etch rates (700–2800 Å/min). C2 and SiF optical emissions were measured for blanket Si, SiO2 and photoresist wafers. A procedure which ratioed the C2 to SiF emissions of a blanket photoresist wafer and normalized this ratio to the C2 to SiF emission ratio of a Si wafer, measured under the same conditions, was used. A strong correlation observed between the amount of C2 optical emission, and the removal rate of photoresist in the etching plasma was observed. This correlation provides a real time diagnostic that can be used for monitoring and controlling the contact etching process conditions.

1.5 μm photoluminescence of Er3+ in YF3, LuF3, and LaF3 thin films

We have studied the photoluminescence at 1.5 μm of the 4I13/2→4I15/2 transition of the Er3+ ion, incorporated as ErF3 into polycrystalline YF3, LuF3, and LaF3 films, deposited onto SiO2 or Si wafers. We conclude that LaF3 is an exceptionally suitable host for Er3+, since it permits high Er3+ concentrations, long lifetimes of the excited level, and a strong Stark splitting. This results in a spectral shape suitable for broadband optical amplifiers with a usable optical bandwidth exceeding 8000 GHz (Δλ≂60 nm).

Preparation and characterization of negative photosensitive polysiloxaneimide

AbstractA photosensitive polysiloxaneimide precursor was synthesized from oxydianiline, bis(p‐aminophenoxy)dimethylsilane, and a diacid chloride. This diacid chloride was prepared by the reaction of thionyl chloride with a diacid, which resulted from the reaction of pyromellitic dianhydride with hydroxyethylacrylate in N‐methylpyrrolidone (NMP). The adhesion properties between polyimide and substrates such as SiO2 wafer were improved with introduction of siloxane moiety into the polyimide chain. The dielectric constant decreased with increasing siloxane moiety content. The photocrosslinking reaction results show that an 88–90% gel fraction was reached under the irradiation of a high‐pressure mercury lamp. © 1995 John Wiley & Sons, Inc.

Total photoelectron imaging of submicron stripe patterns using soft x‐ray microbeams formed by Wolter‐type mirrors

Line scans of micro‐ to submicron‐width stripe patterns with soft x‐ray (150 eV) microbeams formed by Wolter‐type mirrors were performed by detecting total photoelectron intensity. The samples were aluminum stripes delineated on a SiO2 wafer with identical width and spacing of either 0.7, 1, or 4 μm. The modulation of an image of the 4‐μm‐linewidth stripe pattern, which was obtained by scanning a 2.1 μm focused beam, was 0.33. The modulations of images for the 1‐μm‐linewidth stripe pattern and for the 0.7‐μm‐linewidth stripe pattern, both of which images were obtained by scanning a 1.8 μm focused beam, were, respectively, 0.12 and 0.08. We achieved the highest lateral resolution in one‐dimensional photoelectron imaging performed by grazing incidence mirrors.

XPS Studies of the Interactions of Biocells with Various Silicon Based Surfaces

AbstractSiliceous materials are the principal components of Earth's crust and also have become key ingredients of modem technology. Recently, we have expanded our chemical characterization of complex silicates (e.g., framework [1] and sheet types [2]) to include studies of their interaction with select biocells [3,4]. It is becoming apparent that the surface chemistry of these silicates, and perhaps that of silica itself, plays a key role in the oft resulting cell pathogenesis, thus enhancing the value of further investigations with X-ray photoelectron spectroscopy. The present research describes the unique growth of Ehrlich (murine or rat tumor) cells on Sio and SiO2 wafers, and also on select seaentine silicates (such as chrysotile asbestos). Tbese growth studies were followed by both cell/silicate separations and unique freeze drying [3,4]. XPS examination at select stages discovered cell induced alterations in the Si, O, Mg and particularly Fe chemistry of the silicon based systems as well as corresponding changes in the cell chemistry. Many of these features were confirmed by atomic absorption spectroscopy.

Sensitivity Enhancement of Polyorganophosphazenes to Radiation with 2,2,4,4,6,6-Hexakis(2-Hydroxyethyl Methacrylate)Cyclotriphosphazene Monomer and its Application for Negative Resists

Abstract This work focuses on the application of a multifunctional phosphazene monomer, 2,2,4,4,6,6-hexakis(2-hydroxyethyl methacrylate)-cyclotriphosphazene (6-Hema) for enhancement of the sensitivity of polyphosphazenes to both 60Co and E-beam radiation. Specifically, elastomeric and glassy phosphazene polymer films treated with 6-Hema were irradiated under vacuum, and the gel content was determined. The Charlesby-Pinner approach was used to compare the radiation sensitivities of these films. This served as the basis for eventually preparing SiO2 wafers with thin films of the glassy polyphosphazenes mixed with or overcoated by the 6-Hema monomer. The SiO2 wafers prepared with the most sensitive polymer/monomer system were patterned with an ERC electron beam accelerator/scanning electron microscope computer-driven instrument. It was determined that these negative resist films were 1-2 orders of magnitude more sensitive to radiation than the polymers without the monomer.

Experiments with back side gas cooling using an electrostatic wafer holder in an electron cyclotron resonance etching tool

Wafer temperature, etch rate, and etch uniformity measurements of SiO2 wafers were made to characterize the use of back side helium cooling with an electrostatic wafer holder in an electron cyclotron resonance etching tool. The etch rate was found to be independent of the wafer temperature in the range between 20 and 110 °C. A 7% increase in etch nonuniformity (3σ) at higher backside pressures was attributed to helium, which leaked around the edge of the wafer, displacing the etchant gas. A back side pressure of 2–3 Torr provides a balance between wafer temperature control and helium leak rates.