Haruaki Sakurai

Chemical Mechanical Polishing with Nanocolloidal Ceria Slurry for Low-Damage Planarization of Dielectric Films

New chemical mechanical polishing processes using nanocolloidal ceria slurry are proposed for high-precision and low-damage planarization of silicon-dioxide-based dielectric films. In the polishing process of a shallow trench isolation structure, a hard pad and a cationic polymer additive are used in combination with the slurry. The new process is effective in improving the planarity and reducing the microscratch count in comparison with a conventional polishing process with calcined ceria slurry and a standard pad. In the polishing process of an interconnect structure with ultralow-k interlayer dielectrics (ULK-ILDs), the standard pad should be used since the ULK-ILDs are easily damaged. By employing a spin-on-type ULK-ILD having a self-planarizing effect, a high planarity is obtained when using the nanocolloidal ceria slurry with the standard pad. The electrical measurement of the interconnect structure indicates that dielectric damage due to the process is successfully suppressed.

Nano size cerium hydroxide slurry for scratch-free CMP process

We report recent progress in a novel cerium hydroxide polishing slurry with particle size of about 5 nm nano size cerium hydroxide (NSC) abrasive. NSC has succeeded in omitting particles over 1 μm, and in reducing scratches to 1/30 of those with calcined ceria slurry. Even though, NSC maintains oxide removal rate similar to conventional ceria. Mixing NSC with the specific additives brought out tunable polishing of SiO2, SiN, and poly-Si.

Low-Shrinkage Spin-On Glass for Low Parasitic Capacitance Gap-Filling Process in Advanced Memory Devices

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 low-shrinkage SOG can be applied to multilevel metallization.

Thermally and Chemically Robust, Non-Reflowable Low-k Spin-on Glass (k = 2.4) for Gap-Filling Technology in Sub-50-nm Memory Devices

A novel non-reflowable low-k spin-on glass (NR-SOG, k = 2.4) has been developed for the gap-filling technology in sub-50-nm memory devices. The new SOG has planarizing and gap-filling capabilities as high as conventional reflowable SOGs have, while it has thermal stability up to 800degC and chemical stabilities against HF and amine. A damage-less via-formation process for integrating NR-SOG into interconnects, where an amine-based solution is used for photoresist removal, was also developed. The fabricated fine-pitch interconnects with minimum spacing of 50 nm showed sufficiently low line-to-line capacitance and high TDDB reliability