Effects of H 2 and N 2 treatment for B 2 H 6 dosing process on TiN surfaces during atomic layer deposition: an ab initio study.

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 the W 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 B 2 H 6 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 B 2 H 6 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 B 2 H 6 precursor since the overall reactions of the B 2 H 6 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 B 2 H 6 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 B 2 H 6 bond dissociation. As a result, the effect of N 2 treatment serves as a catalyst to decompose B 2 H 6 . From the deep understanding of the effect of H 2 and N 2 during the B 2 H 6 dosing process, the use of proper gas treatment is required for the improvement of the W nucleation layers.