Jau-Shiung Fang

Evaluation of radio-frequency sputter-deposited textured TiN thin films as diffusion barriers between copper and silicon

Thin textured titanium nitride (TiN) films with thicknesses under 100 nm were grown on (100) silicon wafers by employing a radio-frequency generator to sputter reactively a Ti target under poisoned modes in mixtures of fixed Ar (3.6×10−1 Pa) and N2 at various partial pressures. The texture of the TiN films can be tailored by appropriately controlling the partial pressure of the reactive nitrogen. (111) textured films can be deposited over a broad range of lower N2 partial pressures from 2.9×10−2 to 1.8×10−1 Pa, while (100) textured films can be deposited in a narrow range of higher nitrogen partial pressures (2.3×10−1 to 3.3×10−1 Pa). The texturing effect is accounted for by a previously described thin film deposition mechanism. Scanning electron and atomic force microscopies demonstrate that the two textured TiN films both exhibit a column-grained structure; the columnar size of the (111) oriented TiN (⩾30 nm) is coarser than that of the (100) oriented TiN (10–20 nm). Evaluations of the textured TiN barr...

5-nm-thick TaSiC amorphous films stable up to 750°C as a diffusion barrier for copper metallization

Ultrathin TaSiC amorphous films prepared by magnetron cosputtering using TaSi2 and C targets on Si(100), in a sandwiched scheme Si(100)∕TaSiC(5nm)∕Cu, were evaluated for barrier performance in copper metallization. Optimizing carbon content maximizes thermal stability of the films as depicted by sheet-resistance, x-ray diffraction, and transmission electron microscopy examination. The stability temperatures of 700°C (24at.% C) and 750°C (34at.% C) have been systematically verified and discussed. Since Ta, Si, and C are compatible with integrated circuit (IC) processing, the TaSiC films are readily applicable for sub-65-nm IC production.

Phase transition behavior of reactive sputtering deposited Co–N thin films using transmission electron microscopy

Cobalt nitride thin films could be prepared by employing a direct current reactive sputtering deposition on (100) silicon substrates in mixtures of fixed Ar (4×10−1 Pa) and N2 at various partial pressures. The CoxN thin films could be tailored by appropriately controlling the partial pressure of the reactive nitrogen. With adequately increasing nitrogen to argon partial pressure, a series of sequence phase formation from α-Co, Co4N, Co3N, Co2N, and CoN could be observed. The phase transition sequence was accompanied by a substantial refinement and improvement of the films’ grain structure. Rapid thermal annealing of cobalt nitride thin films exhibited a stepwise decomposition via the dissociating of Co4N→Co3N+β-Co(N), Co3N→Co2N+β-Co(N), and Co2N→CoN+β-Co(N) with increasing the elevated temperature. Phase formation, thermal decomposition, electrical resistivity, and microstructure of reactive sputtered cobalt nitride films were discussed in this study.

Ultrathin Ru–Ta–C Barriers for Cu Metallization

The use of an ultrathin Ru-Ta-C film as a barrier for copper metallization in sub-32-nm ultra-large-scale integration (ULSI) has been evaluated. The films, fixed at 5 nm, were deposited by magnetron sputtering using Ru and TaC targets, and the film composition and structure were adjusted by tuning the respective deposition power. The structure of the Ru-Ta-C films gradually changed from Ru 4 Ta(C) to nanocrystalline or nearly amorphous when optimizing TaC. For a sandwiched scheme of Cu/Ru 82 Ta 12 C 5 /Si or Cu/Ru 77 Ta 15 C 7 /Si, the failure temperature was at least 750°C. We also electroplated Cu directly onto a Ru-Ta-C film without Cu seeding. Because of their low resistivity ( < 100 μΩ cm) and high thermal stability, Ru-Ta-C films are promising as a Cu barrier.

Highly Thermal-Stable Amorphous TaSi2C x Films as Diffusion Barrier

Structural changes at high temperature of amorphous TaS1 2 C x films deposited on Si(100) were evaluated. Increased carbon content remarkably raises crystallization temperature; thus, TaSi 2 C x films (x > 16 atom %) sustain amorphous phase at 800°C for at least 30 min. A preliminary evaluation of such films as a diffusion barrier of Cu metallization in a sandwich scheme Si(100) / TaSi 2 C x (20 nm)/Cu showed the stability of 750°C (x = 19 atom %) or 800°C (x = 22 atom %) for at least 5 min without a sharp increase in sheet resistance nor the formation of Cu 3 Si. Because Ta, Si, and C are compatible with integrated-circuit processing, these films are readily applicable as diffusion barriers in Cu metallization.

Highly Thermal-Stable Amorphous TaSi2Cx Thin Films

Highly thermal-stable amorphous TaSi2Cx thin films Ting-Yi Lin,Tsung-Shune Chin,Huai-Yu Cheng, and Jau-Shiung Fang Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 300, Taiwan, Republic of China Department of Materials Science and Engineering, National Formosa University, Huwei 632, Taiwan, Republic of China The corresponding authors: +886-35742630, tschin@mx.nthu.edu.tw and jsfang@sunws.nfu.edu.tw