Effects of H-2 and N-2 treatment for B2H6 dosing process on TiN surfaces during atomic layer deposition: an ab initio study

Abstract

For the development of the future ultrahigh-scale integrated memory devices, a uniform tungsten (W) gate deposition process with good conformal film is essential for improving the conductivity of theW gate, resulting in the enhancement of device performance. As the memory devices are further scaled down, uniform W deposition becomes more difficult because of the experimental limitations of the sub-nanometer scale deposition even with atomic layer deposition (ALD) W processes. Even though it is known that the B2H6 dosing process plays a key role in the deposition of the ALD W layer with low resistivity and in the removal of residual fluorine (F) atoms, the roles of H-2 and N-2 treatments used in the ALD W process have not yet been reported. To understand the detailed ALD W process, we have investigated the effects of H-2 and N-2 treatment on TiN surfaces for the B2H6 dosing process using first-principles density functional theory (DFT) calculations. In our DFT calculated results, H-2 treatment on the TiN surfaces causes the surfaces to become H-covered TiN surfaces, which results in lowering the reactivity of the B2H6 precursor since the overall reactions of the B2H6 on the H-covered TiN surfaces are energetically less favorable than the TiN surfaces. As a result, an effect of the H-2 treatment is to decrease the reactivity of the B2H6 molecule on the TiN surface. However, N-2 treatment on the Ti-terminated TiN (111) surface is more likely to make the TiN surface become an N-terminated TiN (111) surface, which results in making a lot of N-terminated TiN (111) surfaces, having a very reactive nature for B2H6 bond dissociation. As a result, the effect of N-2 treatment serves as a catalyst to decompose B2H6. From the deep understanding of the effect of H-2 and N-2 during the B2H6 dosing process, the use of proper gas treatment is required for the improvement of the W nucleation layers.