Thin films of TiN having low secondary electron emission (SEE) yields are coated on alumina rf windows in order to suppress the occurrence of multipactor. It is necessary to form films with a proper thickness in order to obtain a sufficient reduction of SEE as well as to avoid any excessive ohmic loss in conductive TiN films. For an optimization of the film thickness on an alumina surface, measurements of the SEE coefficients, and ohmic losses in the rf (S-band) field were carried out. High-power examinations of the coated windows were also performed. The results show that TiN films with a thickness of 0.5 nm or greater on alumina ceramics have SEE coefficients of less than unity at an incident energy of 10 keY. High-power tests have revealed that the "going away" of TiN films is probably due to excessive ohmic losses taking place when the thickness is greater than 1.5 nm. It is concluded that optimized film thickness for window coatings is 0.5-1.5 nm.
Organometallic vapor phase epitaxial (OMVPE) growth of GaAs, GaP and InP on Si has been studied using the two-step growth method. Growth parameters for a heteroepitaxial film with a specular surface, a single-domain structure and high crystallinity are demonstrated and discussed. Residual strains in grown films are evaluated and analyzed by taking account of elastic lattice deformation due to lattice mismatch or thermally- induced strain accomodation by rearrangement of misfit dislocations. Thin film GaAs and InP solar cells are fabricated and their performances are discussed in relation to defect density in the films. For GaAs cells, an efficiency of 18 % (AM1.5, active area) is attained by reducing defect density to 2×106 >cm−2 . The defect density is ~. 5×107 cm−2 in the present InP films, and is needed to be less than 106 cm−2 to attain an efficiency of 18 %.
This paper describes a new pillar-shaped via structure in a Cu-polyimide multilayer substrate and its novel fabrication process. forms a fine rectangular via conductor by pattern electroplating using a thick positive photoresist. Furthermore, a flat polyimide dielectric layer is formed only by the photolithographic process using a photosensitive polyimide precursor. The resulting pillar-shaped via conductor is 30 pm square and 25 thick. The area occupied by this via conductor is 25 % smaller than a conventional via not filled with copper conductor, the interconnection density is twice as high, and the thermal resistance is 50 % less. This new via structure is suitable for high-speed signal transmission in a Cu-polyimide multilayer substrate.
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