Dry etching of TiN in N2/Cl2/Ar adaptively coupled plasma

We investigated the N₂ additive effect on the etch rates of TiN and SiO₂ and etch profile of TiN in N₂/Cl₂/Ar adaptively coupled plasma (ACP). The mixing ratio of Cl₂ and Ar was fixed at 75 and 25 sccm, respectively. The N₂ flow rate was increased from 0 to 9 sccm under the constant pressure of 10 mTorr. As N₂ flow rate was increased in N₂/Cl₂/Ar plasma, the etch rate of TiN was linearly increased, but that of SiO₂ was increased non-monotonically. The etch profile and the compositional changes of TiN was investigated with field emission-scanning electron microscope (FE-SEM), FE-Auger electron spectroscopy (FE-AES) and x-ray photoelectron spectroscopy (XPS). When 9 sccm N₂ was added into Cl₂/Ar, a steep etch profile and clean surface of TiN was obtained. In addition, the signals of TiN and Ti were disappeared in FE-AES and XPS when N₂ additive flow into Cl₂/Ar was above 6 sccm. From the experimental data, the increase in TiN etch rate was mainly caused by the increase of desorption and evacuation rate of etch by products because of the increased effective pumping speed. The etch mechanism of TiN in N₂/Cl₂/Ar ACP plasma can be concluded as the ion enhanced chemical etch.     

Dry etching of TiN in N2/Cl2/Ar adaptively coupled plasma

We investigated the N₂ additive effect on the etch rates of TiN and SiO₂ and etch profile of TiN in N₂/Cl₂/Ar adaptively coupled plasma (ACP). The mixing ratio of Cl₂ and Ar was fixed at 75 and 25 sccm, respectively. The N₂ flow rate was increased from 0 to 9 sccm under the constant pressure of 10 mTorr. As N₂ flow rate was increased in N₂/Cl₂/Ar plasma, the etch rate of TiN was linearly increased, but that of SiO₂ was increased non-monotonically. The etch profile and the compositional changes of TiN was investigated with field emission-scanning electron microscope (FE-SEM), FE-Auger electron spectroscopy (FE-AES) and x-ray photoelectron spectroscopy (XPS). When 9 sccm N₂ was added into Cl₂/Ar, a steep etch profile and clean surface of TiN was obtained. In addition, the signals of TiN and Ti were disappeared in FE-AES and XPS when N₂ additive flow into Cl₂/Ar was above 6 sccm. From the experimental data, the increase in TiN etch rate was mainly caused by the increase of desorption and evacuation rate of etch by products because of the increased effective pumping speed. The etch mechanism of TiN in N₂/Cl₂/Ar ACP plasma can be concluded as the ion enhanced chemical etch.     

Planar plasma etching of chromium

We have investigated the plasma etching characteristics of chromium thin films in an rf planar (parallel plate) reactor. The experimental work was performed using a commercial reactor operating at 13.56 MHz with power variable up to 500 W. The etch rate of the Cr films deposited on glass substrates by e-beam evaporation was measured as a function of the concentration of O₂ in a CCl₄/O₂ gas mixture, the total flow rate of input gases and the rf power density. Using a total gas flow of 15 sccm and an input power density of 0.4 W cm^?2, the maximum etch rate was obtained in CCl₄ plasma containing 40% O₂. It was found that doubling the number of the substrates in the reactor decreased the etch rate by 20%. Also, the etch rate at the back of the reactor was twice that at the front. Methods to alliviate non-uniformity and loading effects are discussed and the mechanism of plasma etching of Cr is examined through the effect of various processing parameters on the etching characteristics.     

反应RF磁控溅射法制备非晶氧化硅薄膜及其特性研究

在氧气和氩气的混合气体中,在没有额外加热的条件下用反应射（RF）溅射硅靶制备了非晶氧化硅（a-SiO2)薄膜,并测试分析了薄膜的结构和电特性与O2／Ar流量比的关系。当固定氩气流量,改变氧气流量时,薄膜沉积速率先急剧减少,再增大,然后又减少。当O2／Ar≥0．075时,得到满足化学配比的氧化硅薄膜。并且,随着O2／Ar流量比的增大,薄膜的电阻,电场击穿强度都有所增大,而在HF缓冲溶液（BHF）中的腐蚀速率下降,所有的样品中无明显的H－OH水分子的红外吸收峰。比较发现反应射频（RF）磁控溅射法制备的a-SiO2薄膜具有良好的致密性和绝缘性。     

Antireflective hydrophobic si subwavelength structures using thermally dewetted Ni/SiO2 nanomask patterns

We report the disordered silicon (Si) subwavelength structures (SWSs), which are fabricated with the use of inductively coupled plasma (ICP) etching in SiCl4 gas using nickel/silicon dioxide (Ni/SiO2) nanopattens as the etch mask, on Si substrates by varying the etching parameters for broadband antireflective and self-cleaning surfaces. For the fabricated Si SWSs, the antireflection characteristics are experimentally investigated and a theoretical analysis is made based on the rigorous coupled-wave analysis method. The desirable dot-like Ni nanoparticles on SiO2/Si substrates are formed by the thermal dewetting process of Ni films at 900 degrees C. The truncated cone shaped Si SWS with a high average height of 790 +/- 23 nm, which is fabricated by ICP etching with 5 sccm SiCl4 at 50 W RF power with additional 200 W ICP power under 10 mTorr process pressure, exhibits a low average reflectance of approximately 5% over a wide wavelength range of 450-1050 nm. The water contact angle of 110 degrees is obtained, indicating a hydrophobic surface. The calculated reflectance results are also reasonably consistent with the experimental data.     

Ellipsometric and Rutherford Back scattering Spectrometry studies of SiO(X)N(Y) films elaborated by plasma-enhanced chemical vapour deposition technique

Silicon oxynitride (SiO(X)N(Y)) thin films were deposited by plasma-enhanced chemical vapour deposition technique (PECVD) from silane (SiH4), nitrous oxide (N2O), ammonia (NH3) and nitrogen (N2) mixture. Spectroscopic ellipsometry (SE), in the range of wavelengths 450-900 nm, was used to define the film thickness and therefore the deposition rate, as well as the refractive index as a function of the N2O gaseous flow. While considering the (Si3N4, SiO2, H2 or void) heterogeneous mixture, Maxwell Garnett (MG) theory allows to fit the SE measurements and to define the volume fraction of the different phases. Finally, Rutherford Backscattering Spectrometry (RBS) results showed that x = O/Si ratio increases gradually with increasing the N2O flow, allowing the correlation of the SiO(X)N(Y) films main parameters.     

Sub 50 nm nano-patterns with carbon based spin-on organic hardmask

Carbon based spin-on organic hardmask (C-SOH) was used as an imprint resin to fabricate sub 50 nm sized patterns. Imprinting of C-SOH was done with a polyurethaneacrylate (PUA) stamp. Patternability and etch resistance of the C-SOH resin was compared to poly(methyl methacrylate) (PMMA). C-SOH can be patterned at the nanosize using imprint lithography and exhibits superior etch resistance, especially for F-based plasmas. Due to the poor etch resistance of imprint resin such as PMMA, it is seldom used as an etch mask to form nano-structures by etching the Si3N4 layer. However, such a nano-structure was able to be formed by etching the Si3N4 layer using C-SOH as an etch mask.     

SiC材料的低速率浅刻蚀工艺研究

对比研究了SiC材料在CF4+O2混合气体中的ICP刻蚀和RIE刻蚀,获得了刻蚀速率、刻蚀表面粗糙度随刻蚀功率、偏置功率、工作真空、氧含量等工艺条件的变化规律,研究结果表明,通过牺牲一定的刻蚀速率可以获得原子量级的刻蚀表面粗糙度,能够满足SiC微波功率器件研制的要求.     

Influence of effective pumping speed on oxygen atom density in a plasma post-glow reactor

The density of neutral oxygen atoms in a post-glow reactor was measured with a fibre-optics catalytic probe. The source of O atoms was a microwave discharge generated in Ar-O₂ gas with different flow rates up to 3000 sccm/min. The O density was measured at different power of the microwave generator between 40 and 160 W and different effective pumping speed between 7 and 28 m³/h. It was found to depend on the ratio between O₂ and Ar flow rates. At a constant O₂ flow of 200 sccm/min there was a broad maximum of O density between the Ar flow of 200 and 1000 sccm/min, independent of the effective pumping speed. At a constant O₂ and Ar flow rates of 200 and 1000 sccm/min, respectively, the O density was found to increase both with increasing power and increasing effective pumping speed. The results were explained with collision phenomena in ionized gases and heterogeneous recombination of O atoms on surfaces.     

Etch characteristics of CoFeB magnetic thin films using high density plasma of a H2O/CH4/Ar gas mixture

Etch characteristics of CoFeB magnetic thin films patterned with TiN hard masks were investigated using inductively coupled plasma reactive ion etching in H₂O/Ar and H₂O/CH₄ gas mixes. As the H₂O concentration in the H₂O/Ar gas increased, the etch rates of CoFeB and TiN films decreased simultaneously, while the etch selectivity increased and etch profiles improved slightly without any redeposition. The addition of CH₄ to the H₂O gas resulted in an increase in etch selectivity and a higher degree of anisotropy in the etch profile. X-ray photoelectron spectroscopy was performed to understand the etch mechanism in H₂O/CH₄ plasma. A good pattern transfer of CoFeB films masked with TiN films was successfully achieved using the H₂O/CH₄ gas mix.     

Structural changes of hot-wire CVD silicon carbide thin films induced by gas flow rates

Silicon carbide (SiC) thin films were prepared by hot-wire chemical vapor deposition in a CH₄ gas flow rate of 1 sccm, and the influence of the gas flow rates of SiH₄ and H₂ gases on the film structure and properties were investigated. In the case of a H₂ gas flow rate below 100 sccm, the SiC:H films obtained in SiH₄ gas flow rates of 3 and 4 sccm were amorphous. On the other hand, when the H₂ gas flow rate was above 150 sccm, SiH₄ gas flow rates of 4 and 3 sccm resulted in a Si-crystallite-embedded amorphous SiC:H film and a nanocrystalline cubic SiC film, respectively. It was found that gas flow rates were important parameters for controlling film structure.     

GaAs背面通孔刻蚀技术研究

比较研究了GaAs背面通孔腐蚀中的湿法腐蚀和ICP干法刻蚀技术,并利用感应离子耦合(ICP)干法刻蚀技术,采用CCl2F2／Ar混合气体,对GaAs衬底上的通孔工艺进行了研究。通过优化气压、射频功率、CCl2F2／Ar混合气体组分配比,在CCl2F2流量为200sccm,Ar流量为10sccm,源功率Pa=400W,偏压功率Pb=14W,自偏压Vb=120V,真空度P=43Pa时,得到了表面平滑的通孔形貌和最大的通孔刻蚀速率(4．3μm／min)。     

Dry etching properties of TiO2 thin films in O2/CF4/Ar plasma

In this work, the etching properties of titanium dioxide (TiO₂) thin film in additions of O₂ at CF₄/Ar plasma were investigated. The maximum etch rate of 179.4 nm/min and selectivity of TiO₂ of 0.6 were obtained at an O₂/CF₄/Ar (=3:16:4 sccm) gas mixing ratio. In addition, the etch rate and selectivity were measured as a function of the etching parameters, such as the RF power, DC-bias voltage, and process pressure. The efficient destruction of the oxide bonds by ion bombardment, which was produced from the chemical reaction of the etched TiO₂ thin film, was investigated by X-ray photoelectron spectroscopy. To determine the re-deposition of sputter products and reorganization of such residues on the surface, the surface roughness of TiO₂ thin film were examined using atomic force microscopy.     

Nanocrystalline diamond coating on carbon fibers produced at different temperatures: Morphological, structural and electrochemical study

In this paper, the morphological, structural and electrochemical properties of nanocrystalline diamond (NCD) films grown on carbon fibers (CF) were investigated. The CF substrates were produced at three different heat treatment temperatures (HTT):1000, 1500 and 2000 °C. The HTT variation promoted different organization indexes on the CF structures. Consequently, the NCD coating formation was strongly affected by the substrate HTT. The changes in the properties of the diamond films were discussed as a function of the film morphology evolution using CH₄ flow rate of 0.25, 0.5 and 1.0 sccm in the feed gas. The X-ray diffraction measurements for the CF and NCD/CF composites were determinant to characterize the crystallinity of the NCD films as a function of the CF HTT and of the CH₄ addition. Based on the diffractograms, the Scherrer's equation was applied to the (111) NCD peak, resulting in grain size values varying from 11.0 to 5.0 nm depending on the CH₄ flow rate and on the CF HTT. The scanning electron microscopy images confirmed the deposition of a continuous NCD coating with high nucleation rate covering the whole CF, while their quality was analyzed by Raman spectroscopy measurements. The NCD grain agglomerates increased as a function of the increase in the CH₄ flow rate from 0.25 to 1.0 sccm, showing similar film morphology to that of the unfaceted diamond balls obtained by chemical vapor deposition. This behavior confirmed the expected tendency by decreasing the diamond quality with the CH₄ addition, especially for the films grown on CF treated at 1500 and 2000 °C. This performance was also corroborated by the cyclic voltammetry measurements concerning the electrode potential window and their responses in a redox couple.     

The effect of tetrafluoromethane plasma post-treatment on the electrical property of tungsten oxide nanowires

The effects of tetrafluoromethane (CF4) plasma on the surface morphology, chemical compositions, and electrical property of tungsten oxide (W18O49) nanowires are investigated. The nanostructured tungsten oxide nanowires with average length of 250-350 nm were self-catalytically grown on Si substrate. By post-treatment with CF4 plasma for 10 min, the W18O49 nanowires on the substrate showed the highest current response. Longer CF4 plasma post-treatment time demonstrated higher etching effect which demolished the nanowires and resulted in lower conductivity of the samples. The disintegration of the W18O49 nanowires layer after CF4 plasma treatment, revealed physically by the decrease of the average thickness and chemically by the decrease of XRD peak ratio (I 23.0/I 26.0), was closely related to the overall electrical performance. The etching effect was further reveled by Raman spectra showing the evolution of O-W-O and W=O characteristics with the increased post-treatment time. Moreover, the improvement of the electrical property of W18O49 nanowires was elucidated by the exposure rate to explain the mechanism of plasma post treatment in three stages: passivation, degradation and ablation. The maximum exposure rate, corresponding to the maximum conductivity, was achieved by 10 min of CF4 plasma treatment. The time-differentiated exposure analyses confirmed the evolution of resistance of W18O49 nanowires on Si with different post-treatment time which supported the results of surface characterizations.     

Field emission study of carbon nanotubes forest and array grown on Si using Fe as catalyst deposited by electro-chemical method

Vertically aligned carbon nanotubes are synthesized by Low Pressure Chemical Vapor Deposition (LPCVD) on Si substrate coated with Fe as a catalyst at a pressure of 20 Torr and at a growth temperature of 600 degrees C. The catalyst film is prepared by electro-chemical method which is very unique and a low cost method. Three precursor gases Acetylene (C2H2), Ammonia (NH3) and Hydrogen (H2) at the flow rate of 20 sccm, 100 sccm and 100 sccm respectively are allowed to flow through the Low Pressure Chemical Vapor Deposition reactor for 10 minutes. Scanning Electron Microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. Raman analysis shows G-band at 1574 cm(-1) and D-band at 1370 cm(-1). The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission measurement reveals good field emission properties of as-grown vertically aligned carbon nanotubes with turn-on field of 1.91 V/microm at the current density 10 mA/cm2. The field enhancement factor is calculated to be 7.82 x 10(3) for as-grown carbon nanotubes.     

Refraction properties of PECVD of silicon nitride film

Using a neural network, the refractive index of a film deposited in a plasma enhanced chemical vapor deposition is characterized. The deposition process was characterized by a 2^6-1 fractional factorial experiment. Experimental variables and ranges include 20-40 W radio frequency (RF) power, 80-160 Pa pressure, 180-260 sccm SiH₄ flow rate, 1-1.4 sccm NH₃ flow rate, 0-1000 sccm N₂ flow rate, and 200-300°C substrate temperature. To examine the effect of the interaction between variables on the refractive index, a predictive neural network model was constructed. Prediction accuracy was optimized as a function of training factors. Model predictions were certified experimentally. Many complex interactions between the variables not reported previously were revealed. The power effect was transparent only in such plasma conditions as high SiH₄ or NH₃ flow rate. The temperature effect was conspicuous under high pressure. Deposition mechanisms were qualitatively estimated in conjunction with the reported linear dependency of refractive index on SiH/NH ratio.     

Broadband NIR emission in sol-gel Er(3+)-activated SiO2-Ta2O5 glass ceramic planar and channel waveguides for optical application

An Er(3+)-doped SiO2:Ta2O5 optical channel waveguide and nanocomposite were prepared by the sol-gel route at a Si:Ta 50:50 molar ratio. Channels with an excellent surface profile were easily and quickly fabricated by focusing a femtosecond laser onto the surface of multilayered films deposited on SiO2/Si substrates. In parallel, the same sol used to prepare the film was annealed at 900, 1000, and 1100 degrees C for 2 h, to get the nanocomposite materials. A broadband NIR emission around 1538 nm, assigned to the 4I13/2 --> 4I15/2 transition of the Er3+ ions was observed in the nanocomposites of amorphous SiO2 containing dispersed Ta2O5 nanocrystals. The 4I13/2 lifetime and emission bandwidth depend on the annealing temperature. In conclusion, Er(3+)-doped SiO2:Ta2O5 channel waveguides and nanocomposites are promising materials for photonic applications.     

Inductively coupled plasma reactive ion etching of ZnO films in HBr/Ar plasma

The etching characteristics of ZnO thin films were examined in an HBr/Ar gas mix using an inductively coupled plasma reactive ion etching system. The etch rate and etch profile were systematically investigated as a function of gas concentration. In addition, the effects of etch parameters such as coil rf power, dc-bias voltage, and gas pressure were studied. As the HBr concentration increased, the etch rate of the ZnO films gradually decreased while the etch profile was improved. Surface analyses including X-ray photoelectron spectroscopy and atomic force microscopy were employed to elucidate the etch mechanism of ZnO in an HBr/Ar chemistry.     

The etching characteristics of Al2O3 thin films in an inductively coupled plasma

In this study, the etching characteristics of ALD deposited Al₂O₃ thin film in a BCl₃/N₂ plasma were investigated. The experiments were performed by comparing the etch rates and the selectivity of Al₂O₃ over SiO₂ as functions of the input plasma parameters, such as the gas mixing ratio, the DC-bias voltage, the RF power, and the process pressure. The maximum etch rate was obtained at 155.8 nm/min under a 15 mTorr process pressure, 700 W of RF power, and a BCl₃ (6 sccm)/N₂ (14 sccm) plasma. The highest etch selectivity was 1.9. We used X-ray photoelectron spectroscopy (XPS) to investigate the chemical reactions on the etched surface. Auger electron spectroscopy (AES) was used for the elemental analysis of the etched surfaces.