MECHANISM OF STEP COVERAGE FORMATION OF SiO2 FILMS FROM TEOS AND EFFECTS OF GAS PHASE ADDITIVES STUDIED BY MICRO/MACROCAVITY METHOD

The mechanism of SiO2 deposition by pyrolysis of TEOS at 973K was studied by the micro/macrocavity method proposed previously by the authors. We analyzed the deposition-rate profiles in macrocavities (0.1 - 0.5 mm x 10 mm) and microcavities (3µm x 2µm), based on a model of diffusion and chemical reaction occurring simultaneously. Analysis of deposition-rate profiles under reduced pressure (2 Torr) and medium pressure (60 Torr) showed the existence of two kinds of intermediate species, a highly active one and low active one. The effects of gas phase additives (NH3 or H2O) were also examined. Conformal depositions in microcavities were achieved by the addition of H2O in this reaction system

Development of sup 1 sup 9 sup 2 Ir radiation sources for intravascular irradiation

Intravascular brachytherapy is a novel therapy for preventing the restenosis of coronary artery by use of low-dose irradiation. JAERI and Kyoto University have been developing sup 1 sup 9 sup 2 Ir radiation sources by the cooperative research project entitled as 'The research on safety and effectiveness of the intravascular brachytherapy for preventing restenosis of the coronary artery disease' since 1998. The radiation source was introduced into the stenosis through a catheter (a guide-tube to insert directly into vascular) to irradiate the diseased part. Ten sup 1 sup 9 sup 2 Ir seed sources (phi 0.4 mm x 2.5 mm) were positioned between nylon spacers (phi 0.3 mm x 1.0 mm) in a flexible covering tube and the tube was plugged with a core-wire; the tube was shrunk to fix the inside materials and the size is 0.46 mm in diameter and 3 m in length. The physically optimal design was determined to insert the radiation source easily into vascular and to get the dose uniformity in the diseased part. The production method of the radiation source, which is practical to use in the clinics was also established