Interficial Reactions of Ni Thin Films on Si1-xGex Substrates

• Main Authors: Chi-Shen Lee, 李啟聖
• Other Authors: Lih-Juann Chen
• Format: Others
• Language: en_US
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/17665967814948490239

碩士 === 國立清華大學 === 材料科學工程學系 === 87 === Interfacial reactions of Ni on epitaxially grown Si1-xGex strained layer have been investigated. Ni thin films ( 300 A ) were evaporated by an electron beam evaporation system on the Si1-xGex substrates at room temperature. The solid-phase reactions were induced in a rapid thermal annealing (RTA) system by annealing at temperatures ranging from 300 to 700 ℃ for 30 seconds. The resulting films were characterized by transmission electron microscopy (TEM), Auger electron spectroscopy, glancing-angle x-ray diffraction method, energy dispersive x-ray spectrometry (EDS), and four-point probe method. The compositions of final stable phases in the Ni/Si1-xGex system were identified by TEM/EDS semi-quantitative analysis. The lowest resistivity in Ni/Si1-xGex system was found to be 22.28 2.65 μΩ-cm (x = 0.7 for 400 ℃ annealing). The resistivity of nickel germanosilicide is higher than corresponding nickel silicide. The sheet resistance was found to reduce with Ge composition in Ni/Si1-xGex (x = 0.3, 0.7) system. For temperatures above 400 ℃, the sheet resistance decreased rapidly to a minimum value. Ni inside the SiGe was found to be of a silicide- or germanide-like form. The Ge was one of the dominant diffusing species (the other one was Ni) in the Si1-xGex system. Ternary phase formation was found in as-deposited samples in Si0.7Ge0.3 and Si0.3Ge0.7 systems. The thickness of ternary phase layer was found to increase with Ge composition and/or RTA temperature. The textured structures were observed in samples annealed above 400 ℃ in the Ni/Si0.7Ge0.3 system. Ge segregation was observed in samples after 400 ℃ annealing in Ni/Si1-xGex (x = 0.3, 0.7) system. The temperature of Ge segregation was found to decrease with Ge composition. With Ge segregation at high temperatures, the defects were found at the thin film boundaries of Ni/Si0.7Ge0.3 samples after 600 ℃ annealing. Island structure was found in 600 and 700 ℃ annealed samples of Si0.3Ge0.7 and Si0.7Ge0.3 system, respectively. The temperature of island structure formation was also found to decrease with Ge composition. Fine features were observed to be present in island structure. The formation of Ni germanosilicide was dominated by the diffusion of Ni and Ge atoms. The Ni metallization on Si1-xGex substrates was found to be suitable for low temperature ( below 600 ℃) process applications.