Tatsuo Asamaki

RF Sputter-Etching by Fluoro-Chloro-Hydrocarbon Gases

In order to enhance an etching rate using a conventional rf sputtering system, sputtering gases of fluoro-chloro-hydro-carbon were examined, the compositions of which were CF4, CCl2F2, CCl3F, CHCl2F, CHClF2, (CCl2F)2, CCl2FCClF2, and (CBrF2)2. Etching specimens were Si, quartz, glass, Al, Mo, stainless steel and photo resist. With the rf power density of 1.3 W/cm2 at the etching table, the etching rate of Si was ranged from 1000 to 2000 A/min, which were ten to twenty times higher than that by argon. High etching rate is considered to be due the formation of volatile compounds on the surface of specimens. However, etching mechanism is not clarified in detail now. The effect of oxygen on the etching rate was also investigated, and it was found that the etching rate of Si did not decrease up to 12.5% in content of oxygen.

Epitaxial Growth of Al on Si by Gas-Temperature-Controlled Chemical Vapor Deposition

Epitaxial Al(111) film was deposited on Si(111) by low-pressure chemical vapor deposition with the use of tri-isobutyl aluminum (TIBA) at the substrate temperature of 400°C with the deposition rete of 0.9 µm/min. It was necessary for epitaxy to preheat the TIBA gas just before the deposition on the substrate (gas-temperature controlling). The film surface was very smooth; reflectance was higher than 90%. Streaks were observed in RHEED patterns. The rocking curve measured by X-ray diffraction was very narrow. Analysis by SIMS showed the film contained about 0.1% of Si and 20 ppm of O, C, and H. No hillock appeared on the film after 430°C annealing for 40 min.

Gas-Temperature-Controlled (GTC) CVD of Aluminum and Aluminum-Silicon Alloy Film for VLSI Processing

In order to investigate the feasibility of CVD metallization for IC manufacturing processes, Al and Al-Si film depositions on silicon (100) wafers were studied using a precursor gas of triisobutylaluminum with and without disilane. A new mechanism for the gas temperature controller (GTC) was provided in the process chamber so as to activate the gas thermally just prior to its arrival at a heated substrate. The typical deposition rate was 700 nm/min. Without post-annealing, an alloy of Al-0.4%Si was obtained. Specific resistivity was 3.0 µΩcm, and specularity was about 60% at 550 nm for the GTC-CVD films of 1 µm thickness.

A theory on planar magnetron discharge

A new theory on planar magnetron discharge is developed by taking into account relevant parameters: the kinetic energy of electrons, the potential distribution, the magnetic flux density distribution, the collision frequency and the ionization probability. The discharge current is expressed as a function of the average electric field strength and the magnetic flux density. Experimental results show good agreement with the theory.

Epitaxial Growth of Al on Si By Gas-Temperature-Controlled CVD

Epitaxial Al(111) film was deposited on Si(lll) by low-pressure chemical vapor deposition with the use of tri-isobutyl aluminum (TIBA) at the substrate temperature of 400 °C with the deposition rate of 0.9 μm/min. It was necessary for epitaxy to preheat the TIBA gas just before the deposition on the substrate. The preheat was made by gas-temperature-controller provided in the chamber. The film surface was so smooth that reflectance was higher than 90 % of Si and 20 ppm of O, C, and H. No hillock appeared on the film after 430 °C annealing for 40 min. The interface of Al and Si was rather stable so that no alloy penetration occured. The possibility of epitaxial growth of Al(100) on Si(100) was also shown.