Study of Nickel-Silicon Reaction by In Situ Stress Measurement

• Main Authors: Yu, Kun Ho, 游坤和
• Other Authors: Tsai Cho Jen
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/73146135297474287005

碩士 === 國立中興大學 === 材料工程學研究所 === 86 === Metal silicides have been widely used as ohmic contacts, gate electrodes, and interconnects in high－speed deep submicron CMOS devices. NiSi is a possible candidate as next generation silicide material due to its low stresses, low resistivity, low formation temperatures (>375oC), little silicon consumption, extended thermal stability range (375-811oC), and no linewidth dependence of the sheet resistance. In this thesis, the evolution of stresses was studied using in situ curvature measurements with scanning laser method during isochronal annealing in a vacuum with pressure better than 3*10-6 Torr. For Ni(100nm)/Si samples, the phase sequence of Ni->Ni2Si-> NiSi->NiSi2 occurs with increased annealing temperatures at a constant ramping rate, 5oC/min. We observed three apparent valleys in the curvature-to-temperature plot. In this case, the first (328oC) and the second (375oC) valleys were identified to be completely transformed phases of Ni2Si and NiSi, respectively. According to Arrhenius plot of the duration for a specific phase transformation at various annealing temperatures, the activation energy was determined to be 1.53eV for NiSi formation. The activation energies determined by Kissinger-like analysis based on the various ramp rates ranging from 1oC/min to 30oC/min were 1.81, 1.55 and 3.42eV for Ni2Si, NiSi and NiSi2 formation, respectively. For Ni(100nm)/Si samples with measurable oxygen impurity at Ni/Si interfaces, the formation temperature for Ni2Si and NiSi were retarded. Therefore, there was only one (470oC) broad valley in the curvature-to- temperature plot. The effect of a thin Pd layer between Ni film and Si substrate on the silicidation process includes changing the formation sequence of the nickel silicide and retarding the transformation of Ni2Si from NiSi. The curvature-to-temperature plots for samples with thin Pd layers were different from those without thin Pd layers. Two steep valleys (268oC and 420oC) and one broad valley (562oC) were observed. The 420oC valley was identified to be associated with formation of NiSi.