Pulsed Laser Deposition of Ti-Based MAX Compounds for Next-Generation Wiring Technology

Abstract

Semiconductor wiring technology with a width of 10 nm or less is going in order to realize high performance and high integration of large-scale integrated circuits. Copper is currently used as the main wiring material, however, a barrier layer of TiN is necessary due to high diffusivity of Cu into Si or SiO2. In addition, the resistivity of TiN is ten times higher than that of Cu, which results in a drastic increase with decreasing line width less than 10 nm. Therefore, the development of a barrier layer free wiring material to replace copper should be necessary.The MAX compounds (M: transition metal element, A: A-group element, X: either carbon or nitrogen) is one of the promising candidates for next generation wiring technology. The stoichiometry of MAX compounds is Mn+1AXn (n = 1~3), and exhibits the properties of both ceramics and metals, and some of the compounds have a low volume resistivity as 10 μΩcm. In this study, pulsed laser deposition of TiSiN and TiGeN were carried out and physical and electrical properties were evaluated.Targets (TiN : Ti : Ge or Si = 3 : 1 : 1) was bought from TOSHIMA Manufacturing. Al2O3 (001) and 1-μm thickness thermal oxide on Si(001) was used as substrate. Substrate temperature was either room temperature or 600℃. N2 was introduced during deposition. Repetition frequency was fixed at 8 Hz, and laser energy was changed from 25 mJ to 75 mJ. Table 1 and 2 show deposition condition for TiGeN and TiSiN, respectively. X-Ray Diffraction and X-Ray Photoelectron Spectroscopy were used to evaluate the crystallographic structure and composition ratio, respectively. Film thickness was measured by using surface profiler. Electronic properties were measured by four point probe method. Figure 1 shows XRD pattern of TiGeN film deposited on Al2O3 substrate. When TiGeN was deposited at 600℃ and B.P., peaks ascribed to Ge(111), TiN(111) and TiN(200) were observed. TiN(111) peak position 36.85° from TiGeN is 0.04° higher than that from TiN (111) (36.81°, Card No. 00-006-0642), which suggests that lattice parameter decreased from 2.440 Å to 2.437Å. On the other hand, the peak intensity of TiN(200) from TiGeN deposited at 600℃ becomes clear by introducing N2 to 2.0 Pa. TiN(200) peak positions from TiGeN at 600℃ with 0.02 Pa and 2.0 Pa were 39.30° and 39.35°, respectively, the difference from TiN(200) (42.61°, Card No. 00-006-0642) were 3.31° and 3.26°. This suggests that lattice parameter becomes larger from 2.120 Å, to 2.291 (0.02 Pa) or 2.288 Å (2.0 Pa), respectively. One possible reason could be the incorporation fo Ge into TiN lattice. Figure 1