Selective aluminum chemical vapor deposition

Abstract

Selective deposition of metal is the key technology for deep-submicron multilevel metallization of future very large-scale integrated circuits. In this article, selective and nonselective deposition of high quality aluminum by low-pressure chemical vapor deposition using dimethylaluminum hydride (DMAH) and hydrogen was discussed. It was found that, by thermal decompsition, aluminum was deposited on the electrically conductive surface and was not deposited on the electrically insulating surface. A 0.3 μm φ deep-submicron via holes with large aspect ratio more than 3 were completely filled by the selective deposition of aluminum. The selectively deposited aluminum was confirmed to be single crystal (100) and (111) aluminum on (111) and (100) silicon, respectively. We have developed a new controllable method of the selective and the nonselective deposition using a plasma excitation technique. We have successfully planarized via holes with the selective and the subsequent nonselective deposition of aluminum. For the selective growth mechanism of aluminum on silicon, we have proposed a surface electrochemical reaction model, in which free electrons on the surface catalytically contribute to the reaction. In this model, a surface terminated hydrogen atom on silicon surface reacts with methyl radical in the DMAH molecule to produce volatile methane. The hydrogen atom of the DMAH molecule remains on the newly deposited aluminum surface as a new terminated hydrogen atom. The terminated hydrogen atom on the surface reacts repeatedly with methyl radical to deposit aluminum.