Charles W. Magee

A SIMS analysis of deuterium diffusion in hydrogenated amorphous silicon

Secondary ion mass spectroscopy (SIMS) has been used to measure the diffusion of deuterium in hydrogenated amorphous silicon. For a film deposited in a dc glow discharge in SiH4 at a substrate temperature of 315 °C, the diffusion data fits D (T) =1.17×10−2 exp(−1.53 eV/kT) cm2/s. This result implies that degradation of these films due to hydrogen out‐diffusion at 100 °C will not be significant until after more than 104 years.Secondary ion mass spectroscopy (SIMS) has been used to measure the diffusion of deuterium in hydrogenated amorphous silicon. For a film deposited in a dc glow discharge in SiH4 at a substrate temperature of 315 °C, the diffusion data fits D (T) =1.17×10−2 exp(−1.53 eV/kT) cm2/s. This result implies that degradation of these films due to hydrogen out‐diffusion at 100 °C will not be significant until after more than 104 years.

Profiling Hydrogen in Materials Using Ion Beams

Abstract Over the last few years many ion beam techniques have been reported for the profiling of hydrogen in materials. We have evaluated nine of these using similar samples of hydrogen ion-implanted into silicon. When possible the samples were analysed using two or more techniques to confirm the ion-implanted accuracy. We report the results of this work which has produced a consensus profile of H in silicon which is useful as a calibration standard. The analytical techniques used have capabilities ranging from very high depth resolution ( ≈50 A ) and high sensitivity (

Hydrogen localization near boron in silicon

Several models of boron neutralized by atomic hydrogen in silicon were tested by secondary ion mass spectrometry and infrared spectrometry. The hydrogen concentration is comparable to that of boron. Boron neutralization appears as a drop in free‐carrier absorption and as an increase in resistivity. A new infrared vibrational mode attributed to 〈111〉 vibrations of H tied to Si appears at 1875 cm−1.

Secondary ion quadrupole mass spectrometer for depth profiling--design and performance evaluation.

A quadrupole-based secondary ion mass spectrometer designed for depth profiling is described which combines ultrahigh vacuum construction with high sputtering rate, detection sensitivity, depth resolution, mass spectral purity, and abundance sensitivity. Impurities such as B and Al implanted in Si can be profiled to levels below one part per million atomic (ppma), at a depth resolution equal to that obtained by commercial ion microprobes. The primary beam consists of 5-keV, mass-analyzed (40)Ar(+) ions, focused to about 70 microm in diameter. Its high current density (>25mA/cm(2)) permits adequate beam rastering and electronic signal-gating to optimize depth resolution. A secondary ion extraction lens and spherical energy filter are responsible for achieving abundance sensitivities of five to six orders of magnitude on the low mass side of a matrix peak. The ultrahigh vacuum environment of the sample dramatically reduces molecular peaks containing H, C, and O, allowing even hydrogen to be profiled to concentrations below 10 ppma. Because large amounts of data are generated by multi-element depth profiling, means for automated instrument control and data acquisition have been developed.

On the use of CsX+ cluster ions for major element depth profiling in secondary ion mass spectrometry

Abstract The use of Cs bombardment secondary ion mass spectrometry (SIMS) in conjunction with the detection of positively charged Cs-cluster ions, CsX + , is described. This methodology is shown to be useful for the quantitative analysis of matrix-level elements in III–V compounds such as AlGaAs, and atom fractions in mixed Group IV semiconductors such as Si:Ge alloys. The technique obtains this quantitative accuracy while not sacrificing the beneficial characteristics of SIMS such as excellent depth resolution, high dynamic range, and ability to analyze small areas. Data are shown which demonstrate the ability to detect dopant profiles (Zn) while simultaneously obtaining quantitative depth profiles for the major constituents of the sample (AlGaAs). In addition, descriptions are given of this techniques use in quantitative analysis of a sample directly from the CsX + mass spectrum. A mechanism is also put forth which explains the surprising uniformity of sensitivites for elements detected as CsX + cluster ions. The mechanism involves a recombination above the sample surface of the leaving flux of resputtered Cs ions and the leaving sputtered neutral atoms of the sample material. This mechanism separates the ionization process from the sputtering process much like electron gas or electron beam sputtered neutral mass spectrometry (SNMS). The result can be thought of as cesium-ion SNMS.

Depth profiling of sodium in SiO2 films by secondary ion mass spectrometry

A focused beam of electrons in coincidence with a high current density Ar+ sputtering beam and SIMS detection has been used to perform accurate depth profiling analyses of sodium in SiO2 films. Conditions for exact charge compensation are described, and analyses of a 150‐keV sodium implant in a 0.73‐μm film of SiO2 are presented. Without charge neutralization, 98% of the implanted sodium moved to the SiO2/Si interface during SIMS analysis, whereas optimum charge compensation resulted in a basically unaltered implant profile with only 0.06% sodium at the interface.

The use of nuclear reactions and SIMS for quantitative depth profiling of hydrogen in amorphous silicon

Depth profiles for hydrogen in amorphous silicon have been determined by the use of resonant nuclear reactions [1H(15N,αγ)12C and 1H(19F,αγ)16O] and by secondary ion mass spectroscopy (SIMS). Independent calibration procedures were used for the two techniques. Measurements were made on the same amorphous silicon film to provide a direct comparison of the two hydrogen analysis techniques. The hydrogen concentration in the bulk of the film was determined to be about 9 at.% H. The SIMS results agree with the resonant nuclear reaction results to within 10%, which demonstrates that quantitative hydrogen depth profiles can be obtained by SIMS analysis for materials such as amorphous silicon.

Cleaning and passivation of the Si(100) surface by low temperature remote hydrogen plasma treatment for Si epitaxy

This paper presents the results of a study of the hydrogen-passivated Si(100) surface prepared by a remote hydrogen plasma treatment which serves the dual purpose of cleaning and passivating the Si(100) surface prior to low temperature Si epitaxy by Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD). The remote hydrogen plasma treatment was optimized for the purposes of cleaning and passivation, respectively. To achieve a clean, defect-free substrate surface, the remote hydrogen plasma process was first optimized using Transmission Electron Microscopy (TEM) and Auger Electron Spectroscopy (AES). For hydrogen passivation, the substrate temperature was varied from room temperature to 250° C in order to investigate the degree of passivation as a function of substrate temperature by examining the amount of oxygen readsorbed on the substrate surface after air exposure. Low temperature Si expitaxy was subsequently performed on the air-exposed substrates without further cleaning to evaluate the effectiveness of the hydrogen passivation. It was found that better Si surface passivation is achieved at lower substrate temperatures as evidenced by the fact that less oxygen is observed on the surface using AES and Secondary Ion Mass Spectroscopy (SIMS) analyses. The amount of readsorbed oxygen on the H-passivated Si surface after a two hour air exposure was found to be as low as 0.1 monolayer from SIMS analysis. Using Reflection High Energy Electron Diffraction (RHEED) analysis, different surface reconstructions ((3 × 1) and (1 × 1)) were observed for H-passivated Si surfaces passivated at various temperatures, which was correlated to the results of AES and SIMS analyses. Epitaxial growth of Si films at 305° C was achieved on the air-exposed Si substrates, indicating a chemically inert Si surface as a result of hydrogen passivation. A novel electron-beam-induced-oxygen-adsorptiom phenomena was observed on the Hpassivated Si surface. Scanning Auger Microscopy (SAM) analysis was performed to study the reaction kinetics as well as the nature of Si—H bonds on the H-passivated Si surface. Preliminary results show that there is a two-step mechanism involved, and oxygen adsorption on the H-passivated Si surface due to electron beam irradiation may be due to the formation of O-H groups rather than the creation of Si—O bonds.

Hole‐mediated chemisorption of atomic hydrogen in silicon

It has been shown that at 120 °C atomic hydrogen diffuses into p‐type silicon where it ties to a Si dangling bond near an acceptor. However, a thin n‐type surface layer blocks the entry of atomic hydrogen. This demonstrates that free holes in the surface layer are needed to permit the entry of atomic hydrogen.

Sputtering of organic molecules

Abstract Mass spectrometrists are currently using kiloelectron-volt ion and atom bombardment to produce large, intact molecular ions from involatile organic compounds. The mechanism of particle emission from a surface involves momentum transfer from the bombarding particle to sample atoms and has been studied in some detail. Producing intact molecules successfully by this technique is dependent upon: (a) the nature of the momentum-transfer process; and (b) the amount of radiation damage incurred by the uppermost monolayer of the sample from which the molecules are emitted. This paper will address these two areas of critical importance.