There is significant interest in minimizing oxidative damage to substrate semiconductors (e.g., Si) during ALD. Non-hydrolytic ALD chemistries utilize oxygen sources other than water or oxygen and have been shown inflict less oxidative damage to substrates. We directly compare NH and traditional ALD aluminum oxide chemistries and have found the NH ALD films have a larger fixed negative charge and larger interface trap state density. The understanding and control of semiconductor-dielectric interfaces is critical for controlling charge transport, possibly through leaky dielectrics, and for minimizing interface recombination.
Tunnel layer dielectrics (thickness < 2 nm) have been recently examined for protection and for increasing energy conversion figures of merit. In principle, fixed charge within such dielectrics can influence the electrostatic barrier in the semiconductor, which will have a direct impact on these figures of merit. We have examined alumina-silicon interfaces, in which the fixed charge can be tuned over a large range (+1E12 to -5E12 charges cm-2) by changing processing conditions. Based on an electrostatic model, these changes in fixed charge density should shift barrier heights by nearly 200 meV. In MIS stacks, we have found no evidence of changes in fixed charge in metallized, ultra-thin aluminum oxide layers. We will present several possibilities for why the fixed charge that is otherwise always found at these interfaces may be absent in metallized layers. Use of fixed charge to tune barrier heights could allow for large energy conversion figures of merit by simply tuning surface tunnel dielectrics in a manner similar to interfacial dipoles.