摘要:

Capacitance diaphragm gages which were previously known as capacitance manometers, have become a ubiquitous part of systems used in the vacuum community because of their ease of use, compatibility with most gases, and potential accuracy and resolution. They are used not only as pressure measuring devices, but also as transfer standards against which other pressure instruments are calibrated. There are a variety of precautions that must be considered when using these instruments. The American Vacuum Society is therefore presenting this Recommended Practice as a guide to their proper calibration and use as transfer standards. The document covers suggested plumbing configurations, laboratory practices, calibration methods, and reports.

ISSN:0734-2101    

DOI:10.1116/1.577209

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

This article describes first applications of a time‐of‐flight secondary ion mass spectroscopy (TOF‐SIMS) scanning microprobe, based on a high mass resolution TOF‐SIMS instrument, combined with two pulsed primary ion sources: (a) 10 keV Ga liquid metal ion source (LMIS), probe size: 0.5–1 μm; (b) 10 keV electron impact (EI) ion source (Ar+,Xe+,O+2), probe size 4–10 μm. The detection limits for elemental and molecular surface species as a function of probe size are discussed. At a lateral resolution of 1 μm secondary ion images with about 1000 counts/pixel can be acquired in about 30 min. The high useful yields achieved by TOF‐SIMS allows the analysis of submonolayers of inorganic as well as organic materials at high lateral resolution. Currently up to 24 secondary ion images for different masses and a complete mass spectrum can be acquired simultaneously. The performance of the instrument is demonstrated by multielemental and molecular imaging of inorganic and organic patterns on Si wafers. Secondary ion images of a polymer with an average molecular weight of 1400 amu prepared on a silver substrate are presented. As an example for the analysis of insulating materials secondary ion images of an electrically isolated surface mounted device solder pad on an electronic board are shown.

ISSN:0734-2101    

DOI:10.1116/1.577145

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We report studies of the kinetics of thermal decomposition of triethylgallium (TEGa), trimethylgallium (TMGa), and trimethylindium (TMIn) adsorbed on GaAs(100) in ultrahigh vacuum. The adsorbed layers were prepared by dosing GaAs(100) at room temperature, to either saturated coverage or coverages below saturation. The relative coverage of carbon was monitored by x‐ray photoelectron spectroscopy (XPS) as the substrate temperature was slowly increased (0.6–3.2 °C/min). Products were detected at faster heating rates (0.7–6 °C/s) with a differentially pumped quadrupole mass spectrometer. The substrate temperature was measured by infrared laser interferometric thermometry. The kinetic analysis also makes use of XPS and mass spectrometric data on laser‐induced, rapid thermal decomposition (heating rates of ∼1011 °C/s ). TEGa dissociatively chemisorbs on GaAs(100) at room temperature. Heating the substrate from room temperature to ∼500 °C results in desorption of a Ga–alkyl at low temperature, ascribed mostly to diethylgallium (DEGa) and possibly some TEGa.At higher temperature, C2H4and C2H5desorb in parallel after most of the Ga–alkyl has desorbed. The hydrocarbon desorption is described well by simple first order kinetics with an activation energy,Eact=32±4 kcal/mol, and a pre‐exponentialAfactor of 2.5×1010±1.5s−1. Ga–alkyl desorption is more complicated; the Arrhenius parameters for assumed first order desorption exhibit strong coverage dependences. A fit to all the data was obtained forA=5×108s−1andEact=18 kcal/mol at saturated coverage, with a large decrease inEact(or increase inA) with decreasing coverage. TMGa decomposes to yield a Ga–alkyl desorption product (either dimethylgallium, TMGa, or a mixture of the two) at low temperature, and CH3at higher temperature. CH3desorption has a first order activation energy of 43±2 kcal/mol for an assumedAfactor of 1×1013s−1. For the Ga–alkyl,A=108s−1andEact=19 kcal/mol, with a coverage dependence similar to DEGa desorption from TEGa decomposition. TMIn undergoes a methyl exchange reaction on GaAs(100). Upon heating above room temperature, a Ga–alkyl desorbs first, followed by desorption of CH3at higher temperature. The Ga–alkyl has with the same cracking pattern as observed for TMGa decomposition. No In–alkyls desorb, and In desorption does not occur until all carbon‐containing species desorb. CH3starts to desorb at lower temperature than for TMGa decomposition. Assuming anAfactor of 1×1013s−1, CH3desorption over the observed wide temperature range indicates a range of activation energies from 33–43 kcal/mol. Ga–alkyl desorption is similar to that observed during TMGa decomposition. At saturated coverage,A=108andEact=17 kcal/mol. However, the coverage dependence is not as strong as for TMGa, so that Ga–alkyl desorption peaks at lower temperature for TMIn. Decomposition mechanisms for these group‐III metal alkyls are discussed, along with implications for growth of III–V compound semiconductor films from these precursors by chemical vapor deposition and molecular beam techniques.

ISSN:0734-2101    

DOI:10.1116/1.577146

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Products of pulsed laser‐induced decomposition of triethylgallium (TEGa) and trimethylgallium (TMGa) chemisorbed on GaAs(100) were determined and compared to those observed in thermal desorption. The desorbing products, C2H5, C2H4, and Ga(C2H5)x(x=2 and/or 3) for TEGa decomposition, and CH3and Ga(CH3)x(x=2 and/or 3) for TMGa, are the same as those produced in thermal desorption. However, rapid substrate heating with the pulsed excimer laser causes large changes in the relative yields. With laser induced heating, Ga‐alkyl desorption is almost completely suppressed in favor of further decomposition to yield hydrocarbon products and leave Ga on the surface, while in thermal desorption the Ga‐alkyl is a major product. Furthermore, for laser‐induced thermal decomposition of TEGa, C2H5production is enhanced with respect to C2H4. These effects are ascribed to decomposition of chemisorbed GaR2(ads)(R=CH3, or C2H5), leading to formation of adsorbed GaR(ads)and desorption of R(g). This decomposition reaction is entropically favored over desorption of the Ga‐alkyl, but has a higher activation energy. Consequently, decomposition is favored at the rapid heating rates, while desorption of GaRxdominates at slow heating rates. Competition between these desorption and decomposition reactions is likely important in the overall conversion of TEGa and TMGa to expitaxially grown, Ga‐containing III–V compound semiconductor films. Arrhenius parameters are presented for the GaR2decomposition reactions. These data should improve the accuracy of kinetic models for epitaxial film growth by chemical vapor deposition and molecular beam techniques.

ISSN:0734-2101    

DOI:10.1116/1.577147

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Trimethylgallium (TMGa) chemisorption on the gallium‐rich ‘‘(4×6)’’ and (1×6) GaAs(100) surfaces has been studied with temperature programmed desorption (TPD) and static secondary ion mass spectroscopy (SSIMS). Low coverages of TMGa irreversibly dissociate on GaAs(100) and methyl radicals are the main gas‐phase product observed around 700 K during TPD. At higher TMGa coverages some recombinative desorption of molecular TMGa occurs from 250–650 K. On the Ga‐rich surface reconstructions the desorbing methyl radicals are kinetically indistinguishable, strongly suggesting that they evolve from a single type of binding site. We believe this binding site corresponds to surface MMGa, which is formed by stepwise methyl group transfer from chemisorbed TMGa to neighboring surface gallium atoms. The presence of MMGa is supported by SSIMS results at ∼650 K. Temperature‐programmed SSIMS was used to follow the dissociation of adsorbed TMGa from 120 to 700 K.

ISSN:0734-2101    

DOI:10.1116/1.577148

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A reactive ion etching (RIE) with a mixture of fluorocarbon gases is used to etch selectively SiO2patterns on Si wafer. X‐ray photoelectron spectroscopy (XPS) measurements were carried out to determine the walls contamination of the reactor with different cathode coatings like Al, Si, and photoresist. The contamination of different wafers (SiO2, Si with and without resist) following RIE processes was also studied in order to understand the mechanism of the selective etching. Then different cleaning processes, in particularly NF3and O2plasmas followed or not by a hydrophilic treatment, were also qualified by XPS. For every sample, the Al(2p) or Si(2p), C(1s), O(1s), and F(1s) photoelectron lines were monitored and concentrations determined as usual by integration of these lines. F(1s) and C(1s) were decomposed into several components corresponding to different chemical bonds. The results show that the contamination of the reactor walls by fluoropolymers is due to the presence of Si or of the photoresist on the cathode; there is no polymer formation with an Al cathode coating. The polymer contamination on the reactor walls is cleaned off by an O2plasma and the residual fluorine forms a passivative layer with the Al of the reactor walls. During the plasma etching of a SiO2film, there is formation of C–Si, C–C, O–Si–F, F–Si bonds but it is only when there is no oxygen left that CFxbonds are formed. These polymer layers stop the etching process on silicon. They are cleaned by O2or NF3plasma, but the latter removes the polymers without increasing the oxygen, fluorine or nitrogen contamination and appears to be most appropriate for improving the surface quality of silicon after fluorocarbon plasma etching.

ISSN:0734-2101    

DOI:10.1116/1.577149

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The adhesion between 30 nm Ni films and quartz substrates was examined as a function of the interfacial chemistry and mixing induced by low temperature (<100 °C)40Ar+and28Si+ion mixing. The Ni/quartz specimens were implanted with either 65 keV40Ar+or 55 keV28Si+to doses between 1 and 10×1016atom/cm2. Both types of implants were observed to induce extensive interfacial grading. X‐ray photoelectron spectroscopy analyses indicated that Ni–O–Si types of interfacial complexes were present in the as‐deposited specimens, but that these complexes were eliminated by the40Ar+ion mixing. In contrast, high dose28Si+ion mixing was shown to induce the formation of new interfacial complexes (Ni–Si–O and new Ni–O–Si complexes). Adhesion measurements, performed using a scratch tester, indicated that the adhesion of the as‐deposited specimens was good (20 N), but that this adhesion got progressively worse (to less than 1 N) with40Ar+implantation. In the case of28Si+ion mixing, adhesion was reduced (to 5 N) in the low dose specimens, but was substantially increased (to 45 N) in the high dose specimens. Overall, Ni/quartz adhesion was shown to correlate with the concentration of interfacial complexes that could chemically attach the Ni films and quartz substrates.

ISSN:0734-2101    

DOI:10.1116/1.577150

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The reaction of dimethylzinc on Si(100)‐2×1 was studied using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). Dimethylzinc dissociated on this surface at temperatures less than 400 K producing zinc metal and surface methyl groups. During TPD experiments the zinc metal desorbed completely by 600 K, leaving only methyl groups on the surface at higher temperatures. The predominate decomposition pathway for the surface methyl species was complete dehydrogenation producing molecular hydrogen and depositing carbon on the surface. HREELS results indicated that methyl group dehydrogenation occurred at temperatures greater than 700 K. For high initial coverages of dimethylzinc, in addition to complete dehydrogenation products, methyl radicals and acetylene were also detected. The hydrogen desorption temperature was found to increase as a function of the amount of carbon deposited on the surface.

ISSN:0734-2101    

DOI:10.1116/1.577151

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The excimer laser induced desorption rate of SiCl molecules from a chlorinated silicon surface is measured in real time together with the transient change of the surface reflectivity at 632.8 nm. It is demonstrated that, under conditions where gas‐phase chlorine is not photoexcited and does not collide with the surface during the laser pulse, laser induced desorption occurs only when the surface melts, at the laser wavelengths 308 and 248 nm.

ISSN:0734-2101    

DOI:10.1116/1.577152

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The effects of ion irradiation on polyimide surfaces have been studied using x‐ray photoemission techniques. Ion bombardment with energies in the range 0.5–2.0 keV and doses between 8×1013and 1×1015ions/cm2were carried outinsituin the x‐ray photoelectron spectrometer and the chemistry of the modified surface was monitored using core level spectral changes. At low doses and energies, carbonyl groups were preferentially sputtered keeping the rest of the monomer intact. Loss of nitrogen was insignificant compared to losses of carbon and oxygen. At higher energies and doses, the polymer undergoes extensive bond scission, restructuring of various functional groups and species, together with radical and anion formation. High resolution spectra indicated a binding energy scale shift to a lower value, which increased with ion energy and dose, and which was related to the creation of a surface negative charge. The effects of exposure to moisture in the ambient on the surface charge, on the surface structure, and on the surface chemistry was studied.

ISSN:0734-2101    

DOI:10.1116/1.577153

出版商:American Vacuum Society    

年代:1991

数据来源: AIP