Post Si(C)N hillock nucleation and growth in IC copper lines controlled by diffusional creep

International audiencePost Si(C)N hillocks are characterized on Cu interconnects networks. Each network is compounded by standard damascene process electroplated Cu lines with given width and local line density. AFM results show that total volume per area of post Si(C)N hillocks both on narrow and large lines increases linearly with local Cu line density. Two trends of hillocks nucleation and growth are highlighted depending on line width. For line widths inferior to 4 pun, hillocks are located at the line edge. As line density increases, the number of hillocks remains constant but their mean volume proportionally increases. For wider lines, hillocks preferentially nucleate at the center of the line. The number of hillocks proportionally increases as line density increases, but hillock mean volume remains constant. Post Si(C)N hillocks density is found to be proportional to post CMP Cu grain surface boundary density before capping. It is proposed that hillocks growth could be controlled by Cu/Ta interface diffusion on narrowest lines and by grain boundary diffusion on wider ones. (C) 2009 Elsevier B.V. All rights reserved

Chemically assisted vapour transport for bulk ZnO crystal growth

International audienceA chemically assisted vapour phase transport (CVT) method is proposed for the growth of bulk ZnO crystals. Thermodynamic computations have confirmed the possibility of using CO as a sublimation activator for enhancing the sublimation rate of the feed material in a large range of pressures (10(-3) to 1 atm) and temperatures (800-1200 degrees C). Growth runs in a specific and patented design yielded single ZnO crystals up to 46 mm in diameter and 8 mm in thickness, with growth rates up to 400 mu m/h. These values are compatible with an industrial production rate. N type ZnO crystals (mu = 182 cm(2)/(V s) and n=7 10(15) cm(-3)) obtained by this CVT method (Chemical Vapour Transport) present a high level of purity (10-30 times better than hydrothermal ZnO crystals), which may be an advantage for obtaining p-type doped layers ([Li] and [Al] < 10(+15) cm(-3)). Structural (HR-XRD), defect density (EPD), electrical (Hall measurements) and optical (photoluminescence) properties are presented

Cu grain growth in damascene narrow trenches

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Cu grain growth in damascene narrow trenches

Since the end of the last century, Cu damascene integration scheme has been the favoured choice for advanced interconnect technologies. Indeed, due to the lowest Cu bulk resistivity and to it higher resistance to electromigration, performances enhancement with respect to Al have been obtained. Nevertheless, dimensional scaling considerably reduces these performances. At line width below 150nm, grain size is usually measured around line dimension and thus decreases with down scaling. Moreover, columnar grain morphology perpendicular to line sidewall is frequently observed. This results in a large increase of Cu resistivity and in degradation of resistance to electromigration. Optimization of Cu microstructure in damascene architecture is then required. This is the topic of this work. Direct measurements of microstructure through electron microscopy (TEM, EBSD) and X ray diffraction methods are performed. Indirect measurement of grain size evolutions via resistivity characterization is done. Complementary grain growth simulations are performed using vertex method. It is observed that, depending on line dimension, anneal conditions and electrolyte, different type of microstructures are achieved. As expected, certainly due grain boundary pinning on sidewall, for long time anneal, a stable situation is reached. We evidence that Cu line microstructure results from an interaction between grain growth inside the trenches and grain growth in the Cu overburden. On one hand, for the larger lines, the grain size is directly related to the grain growth in the overburden, on the other hand, for the narrowest lines, interfaces limit the impact of this layer on the inline grain growth. A quantitative measurement of overburden microstructure extension in trenches is reported. It could be used to optimize the in-line microstructure with respect to resistivity and electromigration resistance. © 2009 American Institute of Physics