The mechanochemical processing properties of silicon are evaluated by diamond-tip sliding using atomic force microscopy (AFM) in the atmosphere. Sharp-diamond-tip sliding produces grooves on the silicon surface. In contrast, large-radius-diamond-tip sliding produces protuberances on the silicon surface. Potassium hydroxide (KOH) solution etching is performed on the mechanochemically processed areas. Processed protuberance areas are hardly etched with KOH solution. In particular, the processed area, in which plastic deformation is observed, also acts as an etching mask for KOH solution. By application of this mechanochemical local oxidation area as a KOH solution etching mask, three-dimensional nanoprofiles such as three 1000 nm × 1000 nm squares, lines and spaces with a 200 nm period and a two-step table were fabricated on a silicon surface. By using thick oxidized mechanochemically processed masks with a high load and removal of the natural oxide layer by mechanical action with a low load, nanometre-scale three-dimensional profiles were processed by additional KOH solution etching.

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Nanoprotuberances and grooves were fabricated on a silicon surface by approximately 100-nm-radius diamond tip sliding using an atomic force microscope in atmosphere. To clarify the mechanical and chemical properties of these processed parts, changes in the protuberance and groove profiles due to additional diamond tip sliding and potassium hydroxide (KOH) solution etching were evaluated. Processed protuberances were negligibly removed, and processed grooves were easily removed by additional diamond tip sliding. The KOH solution selectively etched the unprocessed silicon area, while the protuberances, grooves and flat surfaces processed by diamond tip sliding were negligibly etched. Three-dimensional nanofabrication is performed in this study by utilizing these mechanochemically processed parts as a protective etching mask.

A new low-dielectric-constant spin-on glass (SOG) with a k value of 2.4 has been developed for a gap-filling process in advanced memory devices. The low-shrinkage characteristic of the SOG during thermal curing provides capabilities of gap filling and planarizing as high as those of conventional reflowable SOGs. The low-shrinkage SOG has thermal stability up to 800 C and chemical stability against diluted hydrofluoric acid, sulfuric acid-hydrogen peroxide, and amine-based solutions, which makes it possible to be used as an interlevel dielectric of memory devices. Tungsten and aluminum interconnects fabricated using the low-shrinkage SOG showed a parasitic capacitance 30% lower than those fabricated using silicon dioxide and a sufficiently long line-to-line dielectric breakdown lifetime. Taking advantage of the high chemical stability of the SOG, an all-wet damageless via-formation process using an amine-based photoresist stripper has been developed. By using the process, the lowshrinkage SOG can be applied to multilevel metallization. #