Comparison of chemical schemes for Si atomic layer epitaxy

Chemical schemes for Si atomic layer epitaxy (ALE) are discussed using a two-step sequence of reactions: (1) surface chlorination, using a chlorosilane molecule, and (2) reduction (Cl removal), using atomic H or a silane molecule. The schemes are compared in terms of equilibrium thermodynamics, to select the most promising schemes. All of the proposed processes based on atomic H are spontaneous (thermodynamically downhill). Two reactions using Si2H6 are endothermic, but may be thermally driven at useful Si-growth temperatures, due to a large, positive entropy change for the reaction. © 1992 American Chemical Society.