摘要:

The coupled effect of molecular scattering and surface‐activated reactions on low‐pressure chemical vapor deposition (LPCVD) film conformality is investigated. Using a single‐precursor two‐step surface‐activated deposition as an example, film conformality can be found to depend on two first‐principle dimensionless parameters–Sc, theintrinsicsticking coefficient, and Sa, the surface saturation factor. An analytical integral material balance formulation, developed for the feature‐scale molecular transport, is solved numerically in a wide range of Sc and Sa. The results show that film conformality generally improves with decreasing Sc and increasing Sa. With Sc fixed in most LPCVD processes (due to the nature of the precursor species), the ability to control Sa in the process becomes the key to conformal deposition. The intrinsic surface‐activated deposition rate expression shows no apparent reaction order. Therefore, previously reported Monte Carlo schemes and integral‐differential models employing a single sticking parameter or a fixed reaction order to characterize LPCVD step coverage behavior are applicable only in limited cases. The two‐parameter model has been found useful in understanding the H2‐reduced tungsten CVD process, for which the first‐principle parameters can be determined from kinetic data reported in the literature.  

ISSN:0734-2101    

DOI:10.1116/1.578723

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

We have compared the physical, mechanical, microstructural, and structural properties of tungsten thin films produced by reducing tungsten hexaflouride by silane and hydrogen. We show that despite similarities in chemical composition and film density, the films exhibit differing film hardness and elastic compliances. The origin of the differences is shown to arise from the differences in film growth rate and the incorporation of impurities during film growth. Hydrogen reduction results in the formation of second phase W20O58particles in the tungsten bulk, which leads to film hardening. Silane reduced films show strong texture in the [110] direction, which decays with increasing film thickness. Silane films also show a larger tensile stress and faulted microstructure. Extensive transmission electron microscopy analysis has been carried out and the results have been correlated to x‐ray diffraction studies. We also have studied the surface morphology of the films and show clustering of grains which results in a larger surface feature, compared to the average grain size of the film. As a result of this study, we show the need to complete film characterization prior to changing chemistries to meet specific macroscopic film properties such as film step coverage.

ISSN:0734-2101    

DOI:10.1116/1.578724

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Tungsten and tungsten–carbon thin films have been produced from a W target sputtered in argon and argon–methane mixtures, respectively. The deposition rate of W films was measured as a function of the sputtering power and argon pressure varying in the range of 0.3–3 Pa. The crystallographic structure and composition of W films deposited on silicon and carbon substrates were investigated by x‐ray diffraction and Rutherford backscattering spectroscopy. The electrical resistivity of the W films was minimum (12 μΩ cm) when the internal stresses in the films were negligible. The carbon concentration in the W–C films determined by nuclear reaction analyses and Rutherford backscattering spectroscopy was varied from 10 to 95 at. % with increasing CH4content in the gas phase. The crystallographic structure of the W–C films was found to be dependent on the carbon concentration. Below 25 at. % of carbon, the structure of the W–C films was that of the cubic α‐W phase with a dilated lattice parameter. For higher carbon concentrations, the bcc α‐W phase disappeared and the structure was that of the nonstoichiometric cubic β‐WC1−xphase. The structure of W–C films with a carbon content greater than 65 at. % was nearly amorphous. Internal stresses and electrical resistivity of W–C films were determined as functions of the carbon concentration. The experimental parameters suitable to produce W and W–C films with low resistivities and reduced internal stress level are reported in this article.

ISSN:0734-2101    

DOI:10.1116/1.578725

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Optical emission spectroscopy, Langmuir probes, andB‐field probes have been used to characterize electron cyclotron resonance plasmas used in the deposition of polycrystalline diamond films. These plasmas were generated at 1.33 Pa using selected ratios of CO:H2and CH4:O2:H2that produced the highest quality films (i.e., high degree of faceting and an intense Raman peak at 1332 cm−1). Electron temperature, ion density, plasma potential andB‐field profiles obtained at optimum growth conditions are presented. The best diamond films were produced on silicon (100) substrates biased to +40 V dc and maintained at a constant temperature of 500 °C. These substrates were placed downstream of an electron cyclotron resonance (ECR) layer (the region of high plasma density created by resonant microwave absorption at the 87.5 mTB‐field contour), characterized by aTenear 1 eV and ion densities near 4×1012cm−3. Actinometry was used to quantify the optical emission spectra. In the CO:H2system, quality films were obtained for line intensity ratios of Hγ/Ar=4.0, Hγ/C2=1.1, CH/C2=1.9, CO/C2=0.73, and O/C2=0.89. Nearly identical films were produced in the CH4:O2:H2system, with line intensity ratios of Hγ/Ar=4.2, Hγ/C2=1.2, CH/C2=1.5, CO/C2=0.78, O/C2=0.99. These results indicate that feedgas composition is less important than the critical ratios of C/O/H2in an ECR plasma.

ISSN:0734-2101    

DOI:10.1116/1.578275

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The reflectivity of x‐ray multilayers made of new pairs of materials was theoretically calculated at a wavelength of 45 Å. Carbon and inconel were then selected for ‘‘low index’’ and ‘‘high index’’ layers, respectively, in the multilayer system. Single layers, bilayers, and multilayers of carbon and inconel were characterized by grazing x‐ray reflectometry (GXR), x‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and spectroscopic ellipsometry (SE). From GXR data at 1.54 Å refractive indices and film thicknesses of inconel and carbon layers were obtained. From an analysis of SE data, the dielectric function and the thickness as of inconel and carbon thin films were deduced. XPS and AES measurements revealed the presence of carbides at the interface between carbon and inconel. GXR analysis was performed on ten‐layer C/inconel multilayers. The GXR interference pattern was found to broaden after annealing the samples at 600 °C.

ISSN:0734-2101    

DOI:10.1116/1.578276

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

We have explored a novel approach of electron‐impact postionization involving the use of a focused low‐energy electron beam directed at the flux of sputtered particles in very close proximity to the sample surface [‘‘matched’’ e‐beam sputtered neutral mass spectrometry (SNMS)]. The first version of an electron gun developed for this purpose delivers a 300 eV beam of ∼100 μA into a 100 μm spot. The postionization efficiency was investigated in a quadrupole based ion microprobe using samples of germanium and gallium arsenide bombarded with 10 keV Ar+. Singly and multiply charged species Mn+(withnup to 5 for As) were produced by electron impact. The position and size of the electron beam with respect to the ion beam could be controlled and optimized by recording raster scanning ion images of the postionized species. Inspection of the energy spectra showed that the ionization probability is larger the lower the velocity of the sputtered neutrals. At low energies (<5 eV) and with the maximum electron current density presently achievable, the intensity ratio of singly charged postionized atoms to secondary ions was ≊1 for Ge and ≊5 for As. Fractional ion yields of 2×10−8and 3×10−8, respectively, are estimated for these species. These numbers are higher by more than one order of magnitude than the yields obtained previously by ‘‘remote’’ e‐beam SNMS. Interference with the secondary ion flux was small or negligible in the case of doubly and multiply charged ions. The fractional ion yields for doubly charged ions ranged from 3 to 5×10−9. The results are compared with available cross sections for electron impact ionization. The measured SNMS ion yields are briefly compared with yields that can be achieved by charge transfer ionization using Ar+beams at maximum current density. Advantages and limitations of the matched e‐beam SNMS technique are discussed together with conceivable improvements using a more advanced electron gun and an improved ionization and ion extraction geometry.

ISSN:0734-2101    

DOI:10.1116/1.578278

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The design, fabrication, and operation of a compact, portable, ultrahigh vacuum, two‐target magnetron sputter deposition system, consisting of independently pumped sample‐exchange and deposition chambers, is described. The target‐to‐substrate distance is 12.5 cm and, for alloy or superlattice growth, the substrate is typically placed at 45° to both target surfaces. A novel shutter system composed of a hollow cylinder with a rectangular opening is mounted on a rotary feedthrough driven by a precision direct‐current motor to controllably expose the substrate to sputter‐ejected flux from one or both targets. Film thickness and composition uniformity are achieved through the use of selectively transmitting shields which are first coated with target material to prevent film contamination. Automatic mass‐flow controllers, responding to a differential feedback signal from a capacitance manometer, are used to maintain the pressure constant during deposition. The film growth temperature can be varied from ambient to 1000 °C while adjusting the negative substrate bias from 0 to 500 V. In initial experiments using this system, epitaxial metastable Ti1−xAlxN alloys and TiN/Ti1−xAlxN superlattices were grown on MgO(001) and polycrystalline Ti1−xAlxN alloys were deposited on oxidized Si(001) substrates.

ISSN:0734-2101    

DOI:10.1116/1.578279

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Amorphous carbon films have been deposited by plasma enhanced chemical vapor deposition from methane and hydrogen gas mixtures excited at two different frequencies, 35 kHz and 13.56 MHz. Large differences observed in the optical emission spectra of the discharge have been attributed to changes in the main dissociative excitation processes of the CH4molecules. The deposition rate and film composition also depend on the discharge frequency. At 35 kHz, the high concentration of atomic hydrogen during the excitation process favors the etching of the amorphous carbon and extremely thin films are obtained. However, at 13.56 MHz, the deposition rate is much higher and the films present a high polymeric content, which has been related to one of the dissociative mechanism proposed at this frequency (i.e., CH4+e→CH2+H2+e).

ISSN:0734-2101    

DOI:10.1116/1.578280

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The electromagnetic fields which drive a radio‐frequency induction plasma are both modeled and measured. The plasma source consists of a planar, square coil separated from a low pressure plasma chamber by a 2.54‐cm‐thick quartz window. A small loop antenna, which is sealed in a pyrex tube, is immersed in the discharge to determine the magnitude and direction of the rf magnetic field. The measuredBfield is primarily radial and axial. Typical rf field strengths vary from 2 to 7 G for rf powers of 0.1–1 kW. The radialBfield decays exponentially in the axial direction. The skin depth of the electromagnetic field is 1.6–3.6 cm which is consistent with Langmuir probe measured ion densities (typically 3×1011cm−3) in argon. Invoking Maxwell’s equations to deduce the rf electric field from the measuredBfield, we find theEfield to be primarily azimuthal. Peak field strengths increase from 100 V/m at 100 W to 200 V/m at 600 W where they saturate for higher powers. Finally, we present a 3D finite element solution for the fields produced by this plasma source which employs a cold, collisionless plasma model to relate the relative plasma permittivity εrto the electron plasma frequency, ωpe, using εr=1−(ωpe/ω)2. The measured fields support this numerical solution.

ISSN:0734-2101    

DOI:10.1116/1.578281

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

In this work a planar, radio frequency induction plasma source is characterized in terms of ion density, electron temperature, and plasma potential using a single Langmuir probe in oxygen and noble gases. Probe measurements of density were also verified using microwave interferometry. Measured argon ion densities increase nearly linearly with power from 1×1011cm−3at 300 W rf power to 6×1011cm−3at 1.2 kW at 1×10−3Torr. Krypton ion densities are also linear with power but saturate above 1 kW at a density of 2×1012cm−3at 1×10−3Torr. Electron temperatures increase with decreasing pressure from 3 eV at 26×10−3Torr to 7 eV at 0.3×10−3Torr. Plasma potentials are typically 15–30 V and increase with decreasing pressure. Ion saturation current in oxygen at 5×10−3Torr is 2.5% uniform over diagonals of 20 cm when a magnetic multipole bucket is used to confine the plasma. Ion generation energy cost in argon is 100–250 W/A.

ISSN:0734-2101    

DOI:10.1116/1.578282

出版商:American Vacuum Society    

年代:1993

数据来源: AIP