Paper
Mechanism of surface selectivity in aluminum chemical vapor deposition
Published 1990 · G. Higashi, K. Raghavachari, M. Steigerwald
Journal of Vacuum Science & Technology B
16
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Abstract
The pyrolysis of triisobutylaluminum occurs much more readily on the surface of Al than on the surface of an oxide. This propensity allows Al to be grown selectively on a wafer and may simplify certain metallization steps in integrated circuit manufacture. In this study, ab initio molecular orbital techniques have been used to elucidate how the transition state energy for beta‐hydride elimination of the alkyl ligand varies for Al atoms in different chemical environments. Elementary considerations of the nature of the four‐center transition state suggest that the energetics of promoting an electron to the empty pπ‐orbital on Al determines the energy of the transition state. Molecular cluster calculations are then used to show that the energy of this electron promotion increases substantially when comparing an Al atom bonded to other Al atoms versus O atoms, explaining the observed surface selectivity.
Surface selectivity in aluminum chemical vapor deposition is due to the increased energy of electron promotion when bonded to other Al atoms compared to O atoms, explaining the observed surface selectivity in integrated circuit manufacturing.
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