Articles you may be interested inReview of trench and via plasma etch issues for copper dual damascene in undoped and fluorine-doped silicate glass oxide Experimental characterization and modeling of the reliability of three-terminal dual-damascene Cu interconnect trees

Thermo-mechanical stress of tungsten-filled (W-fill) through-silicon-via (TSV) is strongly depending on via shape, size and inter-via spacing, which places constraints on TSV design, including 2-D integrated circuit layout and 3-D structure profile. This paper summarizes these constraints and co-relations among thick (up to 1.2μm) tungsten (W) film, W-fill TSV, and surrounding silicon structures, using Flexus bowing measurement, Wright etch method, and also 3-D TSV stress simulations. In this study, the stress was found to be primarily tensile, and tended to be much higher along the longitudinal ends of the TSV compared to the longitudinal side wall. For an isolated TSV of given width and depth: with 30μm length the stress is 45% greater compared to the case of 7μm length. For an array of TSV with given length, width, and depth: larger spacing along the longitudinal axis (length directions) resulted in 35% lower stress at the longitudinal ends of the TSV, while smaller spacing along the transverse axis (width directions) of the TSV resulted in a 46% lower tensile stress. However, along the longitudinal side walls, the tensile stress increases by 200 MPa as the spacing along the transverse axis decreases between neighboring TSV.

GaN epitaxial films grown by hydride vapor phase epitaxy on polycrystalline chemical vapor deposition diamond substrates using surface nanostructuring with TiN or anodic Al oxide Effect of sapphire-substrate thickness on the curvature of thick GaN films grown by hydride vapor phase epitaxy Since we have found that an entire substrate can be chemically removed in less than 5 min and since GaN is impervious to chemical etching, the GaN on lithium gallate ͑LGO͒ system is an excellent template ͑due to near infinite etch selectivity͒ for developing a thin film/compliant GaN substrate. Here we report on our efforts to grow GaN on LGO, including improvement of the atomic surface morphology using pregrowth pretreatments. We also report the first transferred thin film GaN substrate grown on LGO, transferred off of LGO and mounted on GaAs. With this approach, ͑InAl͒GaN alloys can be grown on thin GaN films, implementing a ''compliant'' substrate for the nitride alloy system. In addition, the flexibility of bonding to low cost Si, metal or standard ceramic IC packages is an attractive alternative to SiC and hydride vapor phase epitaxy GaN substrates for optimizing cost verses thermal conductivity concerns. We have demonstrated high quality growth of GaN on LGO. X-ray rocking curves of 145 arcsec are shown on a 0.28 m thick films. For the first time, we present data on the out-of-plane crystalline quality of GaN/LGO material. Likewise, we show two orders of magnitude improvement in residual doping concentration and factors of 4 improvement in electron mobility. We show substantial vendor to vendor and intravendor LGO material quality variations. We have quantified the desorption of Ga and Li from the surface of LGO at typical growth temperatures using in situ desorption mass spectroscopy and x-ray photoelectron spectroscopy.

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