Investigation of Metallorganic Chemical Vapor Deposited Metal Nitride Films ( TixCyNz, NbNxCyOz,TaxNb(1-x)NyCmOn ) as Diffusion Barriers for the Integration of Low-k Dielectrics

• Main Authors: Wu-Chun Gau, 高武群
• Other Authors: Lih-Juann Chen
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/24649832997692533147

博士 === 國立清華大學 === 材料科學工程學系 === 91 === Metal organic chemical vapor deposition (MOCVD) TixCyNz films were deposited using tetrakis-dimethylamino-titanium (TDMAT) and NH3 as a reaction gas at 325 - 400 oC with Ar/NH3 plasma treatments. Effects of annealing and the subsequently performed Ar/NH3 plasma treatment on the microstructure, composition, and electrical properties of these films were investigated. TixCyNz barrier films were found to be nano-crystalline. Thermal annealing can decrease the reisitivity drastically after annealing above 500 oC, by reducing the concentration of carbon and induce the grain growth. <200> texture was found to increase. By multilayer plasma treatment, the resistivity of TixCyNz thin films decreased from 960 to 548 μΩ • cm with a decrease in the concentration of oxygen in barrier films. The plasma treatment can also remove partially the organic residue and induce crystallization at the surface of the as-deposited nano-crystalline TixCyNz films. Inter-diffusions in the Cu/CVD-TixCyNz/SiO2 and Cu/CVD-TixCyNz/methylsilsesquioxane (MSQ) multilayer structures on silicon wafer after annealing in furnace at 500 to 800 oC have also been investigated. With thermal annealing in N2 ambient for 30 min, Cu/CVD-TixCyNz/MSQ structure was found to be metallurgically stable up to 700 oC. Amorphous NbNxOyCz films were deposited by MOCVD using ethylimidotris-(diethylamido)niobium(V) [Nb=NEt(NEt2)3] source with and without NH3 at various temperatures. The diffusion barrier properties of NbNxOyCz films for Cu metallization were investigated. Both deposition temperature and resistivity of the film were found to decrease drastically upon the addition of NH3. The activation energy for the surface reaction was measured to be 68.40 ± 4.82 kJ/mol in the temperature range of 500 - 600 oC and decreased to 22.16 ± 3.85 kJ/mol by adding 20 sccm NH3 in the temperature range of 300 - 425 oC. The resistivities of the films deposited at the temperatures ranging form 300 to 400 oC are as high as 15,000 • cm. The resistivities of multilayer deposited NbNxCyOz films were significantly reduced to about 2,200 •cm. The NbNxOyCz films were found to be nearly amorphous. The concentration of C in films was reduced significantly and the concentration ratio of N to Nb was varied from 1.67 to 1.1 by using NH3 as a reactant gas. 50-nm-thick NbNxOyCz film was found to effectively prevent the penetration of Cu into the substrate in samples annealed at 600 oC for 1 hr. The barrier failure mechanism in NbNxOyCz is the diffusion of Cu through the barrier layer with the formation of niobium silicide. On the other hand, ternary NbxTa(1-x)NyOmCn diffusion barriers deposited by CVD for copper metallization have been investigated. The barriers were deposited at 375 ℃ with tetrakis-diethylamido-niobium (TDEAN) and pentakis-diethylamido-tantalum (PDEAT) as precursors. Amorphous thin films can be obtained by thermal deposition at temperatures from 500 to 600 ℃. The activation energy of the MOCVD process was determined to be 79.1  4.8 kJ/mol. By the incorporation of NH3 gas into reactants, both MOCVD deposition temperature and carbon concentration in the NbxTa(1-x)NyOmCn films were reduced. In addition, Ar/NH3 plasma post-treatment was implemented to prevent oxygen from being introduced into the barrier films. Amorphous NbxTa(1-x)NyOmCn barrier films were deposited with high resisivity and showed unstable state, especially exposed to oxygen ambient. It is proposed that NbxTa(1-x)NyOmCn films grown by MOCVD may embed in porous structure, which causes film properties to vary on exposure to oxygen ambient. The barrier films are of rather high resisivity. It is likely that NbxTa(1-x)NyOmCn diffusion barrier included a high density of impurities like oxygen and carbon in the deposited process. In addition, the amorphicity also leads to high resistivity.