摘要:

The vacuum ultraviolet (VUV) to near infrared emissions(112⩽λ⩽880 nm)from molecular gases (H2andO2) and molecular gas–noble gas mixtures (H2–ArandO2–Ar) have been investigated with two separate spectrophotometric instruments. We report the influence of plasma parameters such as gas composition, pressure, and microwave power upon the plasma emission. In the case of mixtures with noble gases, we selected a range of plasma parameters so as to obtain very intense VUV emissions, which can be useful for the photochemical treatment of polymer surfaces. Some kinetics mechanisms involved are discussed.

ISSN:0734-2101    

DOI:10.1116/1.581014

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We present a study of a helicon plasma withSF6gas, operating at 13.56 MHz and powers between 0 and 2000 W, pressure between 0.3 and 7.5 mTorr, and flow rates between 4 and 40 sccm. All the measurements of plasma and gas parameters were made in the downstream diffusion chamber, below the helicon source. Two main regimes have been observed: at low power (typically<200 W), the plasma is not luminous in the source and ionization takes place in the diffusion chamber where there is an electric field. At high power, the plasma is strongly dissociated and the ionization occurs in the source for pressure above 0.9 mTorr and in the diffusion chamber when the pressure is below. The fluorine atom concentration increases with power until a saturation level[F]satis reached. The gas flow rate determines the power required to reach the saturation whereas[F]satis proportional to the pressure. The power required for the dissociation can be an important part of the power injected into the reactor leaving less power for ionization. This leads to a decrease of the plasma density when the flow rate increases at constant pressure.

ISSN:0734-2101    

DOI:10.1116/1.581015

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Polymerization reactions in radio frequency fluorocarbon plasmas ofCF4,C2F6,andC4F8have been studied by electron attachment mass spectrometry (EAMS). In these plasmas polymerization occurs readily and molecules containing up to ten carbon atoms (the mass limit of the mass spectrometer) have been found. The densities of large polymers increase with increasing size of the parent gas. In a fluorine-rich environment like aCF4plasma the detected polymers are mainly fully saturated withF (CnF2n+2).As the amount of fluorine in the parent gas decreases, also the degree of saturation of the polymers decreases, which is clearly seen inC2F6andC4F8plasmas. The unsaturated polymers are more reactive, so they can stick more easily to surfaces and possibly create thick polymer films, which are often observed after discharge operation. The polymerization rate depends on the chemical activity of the plasma, which can be easily enhanced by increasing the radio frequency power. The positive ions, extracted from the plasma, are generally somewhat smaller than the neutral polymers and their fluorine content is lower. This is probably due to dissociation of neutrals during their ionization by plasma electrons and to ion collisions in the sheath region. Finally, we have shown that EAMS has considerable advantages in the study of electronegative plasmas and polymerization processes in comparison with traditional mass spectrometry. Unlike the traditional mass spectrometry, employing ionization by high energy electrons, EAMS much better preserves the structure of high polymers, allowing us to detect them as large negative ions.

ISSN:0734-2101    

DOI:10.1116/1.581016

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We report on the etching characteristics of GaAs and AlGaAs by gas source molecular beam epitaxy (GSMBE) using a new precursor bisdimethylaminochloroarsine (BDMAAsCl). The etching rate of GaAs is linearly dependent on the BDMAAsCl flow rate. The activation energy of GaAs etching was 0.25 eV. However,Al0.28Ga0.72Asetching shows the negative activation energy of−0.29 eVat the substrate temperature below 500 °C. The etchings of GaAs and AlGaAs are probably attributed to the formation of GaCl andAlCl2orAlCl3,respectively. Furthermore, we demonstrated that the BDMAAsCl etching remarkably reduced the interfacial impurity (carbon, oxygen, silicon) density of GSMBE-grown GaAs epilayers/epireadysubstrates by one order of magnitude compared with trisdimethylaminoarsine cleaning only.

ISSN:0734-2101    

DOI:10.1116/1.581017

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

As semiconductor wafer size increases (from the current 200 to 300 mm), scaling up a process chamber to meet the same or even more stringent requirements becomes difficult due to complexity of the nonequilibrium plasmas. Designing 300 mm etching reactors can be costly and time consuming for developers without an understanding of fundamental physical and chemical processes. To expedite development and reduce cost, plasma modeling and plasma diagnostics are used to gain insight and assist the 300 mm etching reactor development. In this article, it is demonstrated that plasma modeling and Langmuir probe measurement can be used to study various plasma properties including the effects of inductively coupled power, chamber pressure, aspect ratio, and coil configuration, for a planar inductively-coupled plasma. The results from these studies are used to optimize an inductively-coupled plasma R&D chamber capable of etching 300 mm wafers.

ISSN:0734-2101    

DOI:10.1116/1.580955

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Polyurea thin films were prepared by ionization-assisted codeposition of 1,3-di(4-piperidyl)propane, and 4,4′-diphenylmethane-diisocyanate, and their optical nonlinearity was investigated in connection with the bias voltage applied on the substrate in the course of deposition. The formation of polyurea was confirmed by IR absorption spectra. At the optimum evaporation temperature for each monomer, the birefringence of the film was the largest. The film had high optical transparency in the visible range, and the absorption in the UV range was influenced by the substrate bias voltage. The film showed optical nonlinearity even without the poling process after the deposition. The Maker fringe measurement indicated that the deposited films have a peculiar dipole orientation, unlike the normal poled polymer films. The second harmonic generation characteristic was influenced by the substrate bias and also by the material of the substrate holder. These results revealed the importance of the electric field on the substrate during the deposition in determining the dipole orientation.

ISSN:0734-2101    

DOI:10.1116/1.580956

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We describe an apparatus for ion-molecule-reaction mass spectrometry. It is suitable for on-line gas analysis covering the mass range from 1 to 200 amu with a sensitivity of about 1 ppm. The gas to be analyzed is ionized by reaction with a primary ion beam at low collision energy. A mass-selected ion source allows the fast switching among three primary ions beams (Xe+,Kr+,andCF3I+), covering the recombination energy range from 10.23 to 14.67 eV. Calibration measurements and an example of application to the study of heterogeneous catalysis are presented.

ISSN:0734-2101    

DOI:10.1116/1.580957

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and high-resolution electron energy loss spectroscopy (HREELS) were used to study the adsorption and decomposition (for temperatures between 160 and 1100 K) of biacetyl(CH3COCOCH3)on Si(100). We conclude from peak positions in theC(1s)andO(1s)XPS spectra that biacetyl initially adsorbs by binding through the carbonyl π-bonds either forming a di-σ bonded form of biacetyl or completely cleaving the carbonyl double bond. In TPD, biacetyl molecularly desorbs at 185 K for the multilayer and between 263 and 285 K for the monolayer indicated in TPD. TPD also indicates ketene, methane, and hydrogen desorption at 330, 823, and 870 K, respectively. On the surface, there is evidence in XPS that all C=O containing fragments completely dissociate or desorb by 700 K. Above 700 K, hydrogen begins transferring to the surface as shown by the appearance of a peak in HREELS at2103 cm−1(νSi–H).Surface hydrogen recombines with methyl groups and other surface hydrogen producing methane (823 K) and molecular hydrogen (870 K). SiO desorbs at 1010 K and is reflected in XPS by total loss of theO(1s)signal. Finally, heating to 1100 K results in SiC formation.

ISSN:0734-2101    

DOI:10.1116/1.580958

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Through the use of silicon micromachining, we have developed a microhotplate structure capable of reaching temperatures in excess of 500 °C, onto which thin films have been selectively grown via metalorganic chemical vapor deposition. The microhotplate structure contains surface electrical contacts which permit conductance measurements to be made on films during and after deposition, and therefore presents some unique opportunities for thein situcharacterization of growing films as well as for novel gas sensing approaches. We have investigated the deposition of conducting oxides such asSnO2and ZnO on these microhotplate platforms for gas sensing applications. The conductance of the deposited films has been measuredin situas a function of time, and used in combination with postdeposition thickness measurements to provide insights into the growth rate of the oxide films. Results indicate that our conductance measurements are sensitive, in certain cases, to changes in the film thickness on the order of an angstrom. Conductance oscillations observed during the growth of ZnO thin films have been attributed to variations in the precursor concentration, and were detected as a gas sensor response by the growing films.

ISSN:0734-2101    

DOI:10.1116/1.580959

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The use of liquid hydrazine(N2H4)as a nitrogen source for nitridation reactions has been restricted because of safety, purity, and difficulties in using a liquid source. Hydrazine cyanurate (HC) is a stable solid complex ofN2H4which can be easily handled and purified before use and which evolves pureN2H4upon heating, thus making it a promising source ofN2H4for nitridation reactions. In this article, a process for the synthesis of HC has been developed which decreases theH2Ocontent of the evolvedN2H4from 10% whenH2Owas used as the solvent in the synthesis of HC to 0.7% by replacingH2Owith dimethylsulfoxide as the solvent in the synthesis of HC. The use of the purified HC is demonstrated as a solid source in the nitridation of (100) GaAs substrates at 200 °C in a low pressure chemical vapor deposition reactor. The nitridated GaAs surfaces were analyzed by x-ray photoelectron spectroscopy and were found to be primarily comprised of GaN, GaAs, andGa2O3.The ratio of the constituent peak heights in the Ga3dpeak of GaN toGa2O3was 2.25 in the grown nitride films. The oxide impurities were most likely due to incomplete removal of the native substrate oxide formed prior to growth and were not a product of the nitridation.

ISSN:0734-2101    

DOI:10.1116/1.580960

出版商:American Vacuum Society    

年代:1998

数据来源: AIP