Fumihiko Uesugi

Photothermal effect contribution on film quality improvement in excimer-laser induced metal CVD

KrF excimer laser induced Cr film deposition from Cr(CO)6 has been studied. Remarkable film quality dependence on laser intensity suggested the photothermal effect contribution of intensive uv laser pulses in the CVD process. A cw Ar-ion laser light and its second harmonic light were used, to separate photochemical and photothermal effects. As a result, photoinduced surface heating has been found to be very important for obtaining good quality metallic films in KrF laser induced Cr film CVD.

Resistless inverse projection patterning of aluminum by using synchrotron radiation induced suppression of thermal chemical vapor deposition

Abstract The influence of synchrotron radiation (SR) irradiation on the chemical vapor deposition (CVD) of dimethylaluminum hydride (DMAH) on a Si(100) surface carried out using a molecular-beam CVD technique is studied. The thermal CVD reaction is found to be suppressed almost completely by the SR irradiation. This suppression effect continues even after the irradiation is stopped. Auger analysis reveals that the surface composition of the irradiated area is changed to AIC, while pure aluminum is formed on the non-irradiated area. From these facts, we conclude that the suppression is caused by the very thin reaction blocking layer formed by SR-induced CVD. By using this suppression phenomenon, the inverse projection patterning of Al is successfully demonstrated without photolithography.

Direct projection patterning of aluminum on the SiO2 surface by using synchrotron radiation induced growth initiation of thermal chemical vapor deposition

Abstract The growth control of Al on SiO2 surfaces is studied using synchrotron radiation (SR) irradiation on molecular-beam chemical vapor deposition (CVD) with dimethylaluminum hydride (DMAH). The thermal CVD reaction is found to be initiated by the SR irradiation of the initial stage of the CVD. Once the CVD reaction is initiated, it continues even after the irradiation is stopped. This effect is caused by an initiation layer consisting of Al and C formed by SR-induced CVD. By using this initiation phenomenon, the projection patterning of Al is successfully demonstrated without conventional photolithography using photo-resist.

Photon energy dependence of synchrotron radiation induced growth suppression and initiation in Al chemical vapor deposition. II. Surface analysis by Auger electron spectroscopy

Abstract We analyzed the photochemical reaction of dimethyl aluminum hydride on Si and SiO 2 surfaces as a function of photon energy using synchrotron radiation. Al LVV chemical shifts in the Auger electron spectra were clearly different, depending on whether core or valence electrons were excited. When high-energy photons were used to excite the core electrons, aluminum carbide was formed on the Si surface. On the other hand, when low energy photons, which can only excite valence electrons, were utilized, metallic aluminum was formed on the Si and SiO 2 surfaces. These results were consistent with the previously reported photon energy dependence of CVD characteristics. That is, when AlC was formed with core electron excitation, growth was suppressed, and negative projection patterning was achieved. On the other hand, when Al was formed with valence electron excitation, growth was initiated and positive patterning was performed on the SiO 2 surface. We proposed a model which explained how the Al growth was controlled by the surface layers formed by photochemical reaction, and why growth suppression and initiation changed with the excitation photon energy.

Photon energy dependence of synchrotron radiation induced growth suppression and initiation in Al chemical vapor deposition

Abstract The influence of synchrotron radiation (SR) irradiation on Al chemical vapor deposition has been studied as a function of SR photon energy. A clear difference between inner shell electron excitation and valence electron excitation is observed. Suppression of Al growth on the Si surface is found to be induced effectively by the excitation of the inner shell electrons, while initiation of the growth on the SiO 2 surface is caused by the excitation of the valence electrons.

Synchrotron-radiation-induced growth suppression and initiation in molecular-beam chemical vapor deposition of aluminum

The origins of synchrotron radiation (SR) irradiation effects, the growth suppression on a Si surface and the initiation on a SiO2 surface, in the aluminum chemical vapor deposition (CVD) are revealed by the analysis of chemical shifts in Auger electron spectroscopy (ADS). The surface reaction control effect of SR irradiation is caused by a very thin (<2 nm) modified layer formed by SR-induced photochemical reaction: The suppression layer on a Si surface consists of aluminum carbide, and the initiation layer on a SiO2 surface is composed of metallic Al including carbon and a metallic Si reduced from the SiO2 surface.

Reaction of Si2H2 molecule on a silicon surface

Abstract The disilane (Si 2 H 6 ) decomposition process was studied by Si 2 H 6 molecular beam mass spectrometry. The decomposition rates obtained on Si(100), Si(111), and SiO 2 at 700°C were about 16%, 9%, and 0%, respectively. These values were almost constant above 700°C independently from substrate temperatures. SiH 3 was found to be generated on Si(111), on the other hand, SiH 4 was generated on a Si(100) surface. The difference of the decomposition reactions were interpreted in terms of a dangling bond structure.

Temperature dependence of synchrotron radiation induced growth initiation in the molecular beam chemical vapor deposition of Al on a SiO2 surface

Abstract Synchrotron radiation (SR) irradiation effect in the Al thermal growth on a SiO 2 surface is studied by using a molecular-beam chemical vapor deposition (MB-CVD) technique. Al growth is observed only on the SR-irradiated area at 200°C. The substrate temperature dependence of the SR-assisted Al growth rate is found to be non-monotonous: it rises from 150°C to reach a peak at 250°C, then falls to reach a minimum at 300°C, and rises again over 300°C. The origins of this non-monotonous temperature dependence are investigated by chemical shifts analysis in Auger electron spectroscopy (AES). We find that the peculiar temperature dependence is attributed to the change of the chemical bonding nature of the initiation layers formed by SR irradiation.

Anisotropic Si Etching by a Supersonic Cl 2 Beam

Perpendicular etching profiles of n + -Si(100) are obtained with a supersonic Cl 2 beam at substrate temperature of 900°C. Although small undercuts are observed just below the SiO 2 mask, the side wall etching caused by the background Cl 2 is almost negligible. An aspect ratio of greater than 6 and selectivity of greater than 8000 are obtained with 0.5 μm line & space mask pattern. From Arrhenius plots of etch rates, an effective activation energy of the nozzle beam etching is determined to 0.53 eV. Assuming that the reaction product is SiCl 2 , the reaction probability is estimated to be 19% at 900°C. Highly anisotropic etching of the Si(100) obtained here is due to the large reaction probability.

New molecular compound precursor for aluminum chemical vapor deposition

A new type of precursor for aluminum chemical vapor deposition (Al-CVD) has been developed by mixing dimethylaluminum hydride (DMAH) and trimethylaluminum (TMA). The new precursor has proven itself to be effective for Al-CVD, where a good selectivity between the Si and the SiO 2 mask, a 3.0 μΩ cm resistivity and a pure Al film with low C and O contamination levels (under 100 ppm) were achieved. Quadrupole mass and infrared absorption analysis have shown that the precursor contains a new molecular compound, consisting of a DMAH monomer and a TMA monomer. The mixture has lower viscosity than DMAH and can be easily bubbled for a stable precursor vapor supply.