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A new method of cleaning InP substrates under molecular beam epitaxy conditions involving heating to ⩾500 °C in an As4 flux (JAs4 ≃1015–1016 cm−2 s−1) is described. Evidence of surface cleanliness, good morphology, ordered surface reconstruction, and integrity of chemical composition at the interface is given. Lattice-matched layers of Ga0.47In0.53As grown on InP substrates cleaned in this way showed excellent electrical properties: e.g. a room-temperature mobility μ300=8600 cmPu2 V−1 s−1 at n300 =1016 cm−3.

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has been investigated. The reactions were followed gravimetrically, using a Sartorius microbalance ; measurements were made over the temperature range 25750°C. Atomic oxygen enhanced the rate of oxidation of metals which formed a single p-type oxide (e.g., Ni) but had little or no effect if the oxide scale was n-type, e.g., Zr02, or composed of several oxides, e.g., FeO+Fe,0,+Fe203. These results are explained in terms of Wagner's theory of oxidation, which is extended to include the effect of atoms in the gas phase. Atomic oxygen also increased the rate of reaction when the rate-limiting step was at the gas/oxide interface, e.g., in Cu oxidation, and with silver it caused extensive oxidation where none was detected using molecular oxygen.

Thin films of 0.5 ~xn Ti and 0.5 ~m Au have been deposited on Si and SiO~ substrates in technical vacuum (HV, --~10 -6 Torr) and ultrahigh vacuum (UHV, 10 -9 Torr). After deposition and subsequent annealing in Ne containing -----1% 02 at 300~176 the films were analyzed, principally using Auger sputter ion profiling, but also using electrical resistivity, x-ray, Rutherford backscattering, and SEM/microprobe measurements. While the UHV films were clean to the techniques used, several percent of C and O were present in the HV deposited Ti films. On SiO2 substrates the reaction proceeded via formation of Au4Ti and oxidation of Ti to TiO2 as it came in contact with the air interface. The rate of alloy formation was almost an order of magnitude faster in the UHV deposited films and the oxidation rate was also enhanced. The importance of these usually unmonitored impurities in determining the reactivity of films deposited in technical vacuum is stressed.Gold is widely accepted as the preferred metallic conductor for interconnection patterns on semiconductors, particularly where high current densities are encountered. Its advantages include high electrical conductivity, corrosion resistance, and full compatibility with gold wire thermocompression bonding. Its two main drawbacks, poor metallurgical bonding to the semiconductor and catastrophic reduction of carrier lifetime in the semiconductor, can both be solved by the use of an intermediate layer of titanium between the gold and the semiconductor. While more complex three-layer metallizations incorporating a third layer of Pd or Pt to reduce the Au-Ti interaction are widely used, extremely reliable transistors can be fabricated using Au-Ti metallization only (1).The interaction of Au-Ti thin film couples under thermal stressing and varying humidity has been studied previously (2-4), reflecting its importance both individually and as part of the three-layer metallization schemes. All these studies used films prepared in technical vacuum comparable with that used in device fabrication. As part of a wider program aimed at optimization of the Ti-Au system we have also studied films prepared in ultrahigh vacuurm This paper describes the significant differences between films formed in the two different ways. Resistivity/anneal time plots have been used to identify distinct stages in the interaction and compositional analysis, principally by Auger electron spectroscopy with sputter ion profiling, was carried out at these points. The importance of low levels of impurities such as oxygen and carbon in determining the stability of the layers used in device fabrication is clearly illustrated. ExperimentalSample preparation.--The main series of Au-Ti layers were deposited on a thermally grown SiO2 layer (3500A thick) on Si(lll) slices to allow simple resistivity determinations. Other series of Au-Ti layers, deposited directly on Si (111) substrates, were also subjected to compositional analysis to check for any effects due to the introduction of the SiO2 layer. A standard depositio...