AVS 64th International Symposium & Exhibition
    Plasma Science and Technology Division Thursday Sessions
       Session PS+TF-ThA

Paper PS+TF-ThA10
First-Principles Understanding and Kinetic Monte Carlo Analysis of Reaction Mechanisms in Plasma Enhanced Atomic Layer Deposition of Silicon Nitride

Thursday, November 2, 2017, 5:20 pm, Room 23

Session: Plasma Enhanced ALD
Presenter: Peter Ventzek, Tokyo Electron America
Authors: G. Hartmann, University of Texas at Austin
P.L.G. Ventzek, Tokyo Electron America
J.P. Zhao, Tokyo Electron America
T. Iwao, Tokyo Electron Tohoku Limited
K. Ishibashi, Tokyo Electron Tohoku Limited
G. Hwang, University of Texas at Austin
Correspondent: Click to Email
Plasma enhanced ALD (PEALD) allows fabrication of high quality and ultra-conformal SiN deposition at low temperature. The PEALD of SiN films involves a repetitive two-step process of i) silicon-containing precursor adsorption/decomposition and ii) nitridation. Halogenated silanes such as hexachlorodisilane, bis(tertiary-butyl-amino)- silane, and dicholorosilane (DCS, SiH2Cl2) have been utilized as Si precursors and nitrogen, hydrogen or ammonia have been used as nitrogen precursors. Despite previous studies, the underlying reaction mechanisms of these Si precursors with a nitrogen containing surface during PEALD still remain uncertain. First-principles density-functional theory (DFT) calculations have been used to identify a novel mechanism for the adsorption and decomposition of DCS on a hydrogenated SiN surface. Our study predicts that the DCS adsorption and dissociation can occur by overcoming a relatively low barrier (< 0.3 eV), far lower than the prohibitively large barriers predicted for previously proposed mechanisms. Through a detailed electronic structure analysis of the reaction intermediates, we have also elucidated the principles underlying the DCS adsorption and dissociation, notably the hypervalent nature of Si which permits chlorosilanes to adsorb prior to dissociation. A proper model of the interactions between the SiN surface are necessary to explain the ALD process and also indicate the mechanism for the formation of side products, which has a considerable contribution to the thermodynamic favorability of the proposed mechanism. Insights from the first principles calculations are incorporated into a Kinetic Monet Carlo Model (KMC) to illustrate different process scenarios. Understanding these principles allows us to develop guidelines for processing conditions, such as the importance of maintaining the proper surface composition to support Si precursor adsorption and dissociation.