Presentation Information
[7p-S103-11]Development of Pd Pretreatment for Fabricating Ultrathin Continuous ALD-Co Films
〇(P)Yubin DENG1, Jun Yamaguchi1, Yuhei Otaka1, Souga Nagai1, Noboru Sato1, Naoki Tamaoki1, Atsuhiro Tsukune1, Yukihiro Shimogaki1 (1.The Univ. of Tokyo)
Keywords:
Nucleation enhancer,ALD,ULSI
Ultrathin Co(W) films are promising candidates for single-layer liner/barrier applications in next-generation ULSI Cu interconnects. To meet the stringent demands of advanced integration, a robust and controllable ALD process for fabricating 1-nm-thick Co(W) films is essential. While some studies have explored the combination of ALD and ALE to achieve ultrathin film formation [1], such approaches often involve complex procedures, potential impurity incorporation, and initial growth defects. Given that the formation of continuous ultrathin films requires a high nucleation density, Pd has attracted attention as an effective nucleation enhancer due to its strong catalytic activity in enhancing precursor adsorption and surface reactions. Prior studies have shown that ALD-Co deposited on SiO2 substrates pretreated with Pd results in smaller and more densely distributed nuclei than untreated samples due to catalytic effects of Pd [2]. In this study, the Pd deposition process was further investigated to optimize Co nucleation behavior and enhance film continuity.
All samples were prepared on Si substrates with a 100-nm-thick thermally grown SiO2 layer, followed by cleaning with ethanol and APM. Pd was deposited using either ALD or sputtering. Subsequent Co film deposition was carried out via ALD at 150 °C for 500 cycles. As shown in Fig. 1(a–b), ALD-Pd with a loading of 4.1×10-8 mol/cm2 achieved smaller and more densely distributed Co nuclei (~9 nm, ~1.1 × 1012 cm-2) compared to the sample with a lower ALD-Pd loading of 5.2×10-9 mol/cm2 (~17 nm, ~3.0× 1011 cm-2). Notably, as shown in Fig. 1(c), sputtered-Pd with an even lower loading (1.8×10-9 mol/cm2) resulted in the formation of much smaller and denser Co nuclei (~5 nm, ~4.0 × 1012 cm-2).
All samples were prepared on Si substrates with a 100-nm-thick thermally grown SiO2 layer, followed by cleaning with ethanol and APM. Pd was deposited using either ALD or sputtering. Subsequent Co film deposition was carried out via ALD at 150 °C for 500 cycles. As shown in Fig. 1(a–b), ALD-Pd with a loading of 4.1×10-8 mol/cm2 achieved smaller and more densely distributed Co nuclei (~9 nm, ~1.1 × 1012 cm-2) compared to the sample with a lower ALD-Pd loading of 5.2×10-9 mol/cm2 (~17 nm, ~3.0× 1011 cm-2). Notably, as shown in Fig. 1(c), sputtered-Pd with an even lower loading (1.8×10-9 mol/cm2) resulted in the formation of much smaller and denser Co nuclei (~5 nm, ~4.0 × 1012 cm-2).