摘要:

Dissociations in plasma enhanced chemical vapor deposition forSiO2deposition using tetraethoxysilane (TEOS) were investigated by means of mass spectrometry. First, we showed basic dissociation patterns of TEOS as a function of electron energy. It was shown that TEOS dissociates by electron impact at electron energies below 8 eV, removing the ethyl group(C2H5).Next, we presented dissociation patterns in TEOS/He plasma. Finally, dissociation inTEOS/O2plasma was studied. It was shown that high molecular intermediate products containing carbon and hydrogen, such asSi(OC2H5)2H,Si(OC2H5)2OCH3,andSi(OC2H5)3OCH2,are present only in the TEOS/He plasma but not in theTEOS/O2plasma. It was also shown that eliminated hydrocarbon gases such asC2H2,C2H4,C2H5,andOC2H5are converted intoH2OandCO2.Fourier-transformed infrared and x-ray photoelectron spectroscopy studies revealed that the degree of impurity concentration in the film decreased with increasingO2concentration. Characteristics of metal–insulator–semiconductor devices reflected the degree of impurity concentration in the oxide films. It was found that oxygen gas plays an indispensable role for preparing high qualitySiO2films by oxidizing the intermediate dissociation products and eliminating hydrocarbon gases.

ISSN:0734-2101    

DOI:10.1116/1.581514

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A preliminary study on the 1–4.5 kW power industrial scale 27.12 MHz rf lambda-resonator oxygen asher is presented. Contact probes of several types, including single Langmuir and flat wall probes, thermocouples, and optical emission spectroscopy, are mainly used to diagnose plasma in the inductive source area, downstream chamber and in the vicinity of wafers. Electron density in a 200 mm wafer asher at 2 kW rf power varies from2×1011in the plasma source to5×107 cm−3in a downstream chamber 5–10 mm from a wafer. The ion density exceeds the electron density 10–60 times. The plasma space potential varies in a range of 14–22 V, while the floating potential of the bulk plasma and wall surface varies from +9 to −17 V. The minimum surface floating potential of −17 V exists at the maximum of the rf voltage standing wave distributed along the full lambda inductor. The wafer surface floating potential is in the range of 3–5 V depending on the reactor configuration and is constant within ±1 V on the 200 mm wafer. Positive ion current density on the wafer and downstream chamber surface is less than 1 μA/cm−2. The typical resist ashing nonuniformity is ⩽2%–5% (range, not sigma) for both 200 and 300 mm ashers at about a 6–8 μ/min ashing rate.

ISSN:0734-2101    

DOI:10.1116/1.581515

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Diamond was successfully synthesized using a low pressure, radio frequency (rf), inductively coupled plasma. A source mixture of methanol(CH3OH),hydrogen(H2),and water vapor(H2O)was introduced into a reaction chamber through a quartz tube of 12 mm inner diameter. A seven-turn rf coil was mounted on the quartz tube to produce high-density plasma. The Si substrate was located in a downstream region. Diamond formation was carried out with varying mixture ratio of source gases at total pressures of 70–140 mTorr. Diamond crystals exhibiting a well-defined1332 cm−1diamond Raman peak can be formed usingCH3OH/H2/H2Omixtures at total pressures below 140 mTorr.

ISSN:0734-2101    

DOI:10.1116/1.581516

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The deposition ofSiO2films from novel alkoxysilane/O2rf plasmas has been investigated using tetraethoxysilane and the novel alkoxysilanes, triethoxysilane, tetramethoxysilane, and trimethoxysilane. We have demonstrated that high qualitySiO2films can be deposited from each of these alkoxysilanes under similar conditions. For all precursors, film deposition rates decrease with the addition ofO2.Using 20:80 alkoxysilane/O2plasmas, film deposition rate decreases with increasing substrate temperature and plasma power, while theSiO2film quality increases, as determined by Fourier transform infrared spectroscopy, ellipsometry, and wet etch rates. Substrate temperature appears to be the most influential deposition parameter, significantly affecting both composition and properties of the depositedSiO2films. Measured apparent activation energies forSiO2deposition from alkoxysilane/O2plasmas are negative for all precursors. This suggests an adsorption/desorption-limited deposition mechanism controls film formation in all systems. Additional data forSiO2films deposited from the halogenated alkoxysilanes triethoxyfluorosilane and triethoxychlorosilane are also presented.

ISSN:0734-2101    

DOI:10.1116/1.581517

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Capacitively coupled radio frequency plasmas offer some advantages over other techniques such as microwave induced plasmas with regard to the large area homogeneous deposition of thin films. Diamond films were synthesized from methane and hydrogen gas mixtures in a capacitively coupled radio frequency plasma using a standard 13.56 MHz source in a popular parallel plate electrode geometry with the addition of dc power. The rf+dc plasma is stable and homogeneous and suitable for prolonged operation. The diamond films deposited by this method were characterized by x-ray diffraction, scanning electron microscopy and Raman spectra measurements. Preliminary experiments with electrodes having a diameter of 60 mm were done to investigate the possibility of scaling up of this technology for large-area diamond deposition.

ISSN:0734-2101    

DOI:10.1116/1.581518

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Transparent barrier coatings on polymers are receiving much attention in industry, for pharmaceutical, food and beverage packaging applications. Plasma-enhanced chemical vapor deposition (PECVD) is among several competing techniques which can produce thin layers of inorganic glassy barrier materials. In this article we describe the performance of silicon compounds(SiO2andSi3N4)on 13 μm polyethylene terephthalate (PET) substrates, the barrier coatings being deposited in a dual-frequency (microwave/radio frequency) pilot-scale PECVD reactor for continuously moving flexible webs up to 30 cm in width. The volatile silicon compound used forSiO2deposition is HMDSO(C6H18Si2O),whileSiH4serves to depositSi3N4.Coating thicknesses,d,in the range8 nm⩽d⩽200 nm,are measured using a variety of techniques, namely stylus profilometry, continuous wavelength optical interferometry, x-ray fluorescence, variable angle spectroscopic ellipsometry, and transmission electron microscopy, while film compositions are determined by x-ray photoelectron spectroscopy. Oxygen transmission (OTR) and water vapor transmission (WVTR) measurements are carried out with MOCON “Oxtran” and “Permatran-W” instruments, respectively. As also reported by other workers, we typically find OTR values of about0.5 scc/m2 dayand WVTR about0.3 g/m2 day,for barrier thicknesses exceeding a “critical” value(dc,about 15 nm), but the minimum permeation values depend upon the concentration of defect sites in the coating (mostly related to substrate microroughness). In order to confirm this correlation, we have developed a technique combining reactive ion etching through the PET, followed by optical and transmission electron microscopies, to characterize the types and number densities of coating defects. On the basis of these, we find good agreement between measured and calculated values of OTR.

ISSN:0734-2101    

DOI:10.1116/1.581519

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

In situattenuated total reflection Fourier transform infrared spectroscopy was used to study the H bonding on the surfaces ofa-Si:Handnc-Si:Hduring plasma enhanced chemical vapor deposition fromSiH4/H2/Arcontaining discharges. Well-resolvedSiHx(1⩽x⩽3)absorption lines that correspond to the vibrational frequencies commonly associated with surface silicon hydrides were detected. During deposition ofa-Si:Hfilms usingSiH4withoutH2dilution, the surface coverage was primarily di- and trihydrides, and there are very few dangling bonds on the surface. In contrast, during deposition ofnc-Si:HusingSiH4diluted withH2,the amount of di- and trihydrides on the surface is drastically reduced and monohydrides dominate the surface. Furthermore, the vibrational frequencies of the monohydrides onnc-Si:Hfilm surfaces match well with the resonant frequencies of monohydrides on H terminated Si (111) and Si (100) surfaces. The decrease of higher hydrides on the surface uponH2dilution is attributed to increased dissociation rate of tri- and dihydrides on the surface through reaction with dangling bonds created by increased rate of H abstraction from the surface. Results presented are consistent withSiH3being at least one of the precursors ofa-Si:Hdeposition.

ISSN:0734-2101    

DOI:10.1116/1.581520

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Chlorinated silicon dioxide films have been prepared at low temperatures (200 °C) and high deposition rates (900–1700 Å/min) by remote plasma enhanced chemical vapor deposition using mixtures ofSiCl4,O2,Ar, andH2under various hydrogen flow rate conditions. It was found that films deposited without hydrogen grow with the highest deposition rate, however they exhibit poor properties such as high etch rate, low density, and low refractive index. These oxides are also chemically unstable and easily hydrolyzable upon exposure to ambient moisture. It is assumed that the low chlorine content (detected by Rutherford backscattering) in these samples is due to the hydration of the weak Si–Cl bonds existing in the as-deposited films, which generates desorption of HCl and forms the Si–OH bonds observed in the corresponding infrared spectra. The addition of hydrogen to the process reduces the deposition rate but improves the properties and stability of the films by reducing the amount of chlorine incorporated during growth. At hydrogen flow rates moderately higher than theSiCl4flow, dense and stable chlorinated oxides with properties close to stoichiometricSiO2are obtained. The composition results indicate that in order to obtain these types of oxides the chlorine concentration should be limited to a value around 2.6 at. %.

ISSN:0734-2101    

DOI:10.1116/1.581524

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Microcrystalline silicon (μc-Si:H) of truly intrinsic character can be deposited by plasma-enhanced chemical vapor deposition when dichlorosilane(SiH2Cl2)is added to theSiH4–H2source gas. A dark conductivity of5×10−8 S/cm,activation energy of 0.62 eV, and photoconductivity of1×10−5 S/cmare obtained. The optical band gap for this material is approximately 1.1 eV. No special gas purification or microdoping is required.SiH2Cl2added in small amounts has the additional effects of enhancing the crystallinity, and of reducing the oxygen incorporation by over a factor of 2. Sub-band gap absorption spectroscopy indicates a low defect density. Very high frequency deposition yields material with lower defect density and higher photoconductivity than material deposited using dc plasma excitation. Transition from amorphous to microcrystalline growth occurs during the first 100–150 nm of film growth. The oxygen content increases as the crystallinity increases. A firstp-i-nsolar cell with a 1.8 μm thick μc-Si:H(:Cl)ilayer exhibitsVoc=0.35 V,Isc=4.14 mA/cm2,and FF=55%, demonstrating device-quality material.

ISSN:0734-2101    

DOI:10.1116/1.581525

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Low energy ion pretreatment of silicon dioxide(SiO2)surfaces results in a reduced incubation time(tinc)for polycrystalline silicon (poly-Si) deposition by rapid thermal chemical vapor deposition. By pretreatingSiO2surfaces with inert(He+,Ar+)and chemically active species(H+,N+),it was determined that ion pretreatments reducetincand increase the poly-Si nuclei density by creating nucleation sites via a physical damage mechanism, rather than a chemical process.

ISSN:0734-2101    

DOI:10.1116/1.581526

出版商:American Vacuum Society    

年代:1998

数据来源: AIP