Paper PS1-MoM2
Molecular Dynamics Simulation of Hydrogen Induced Damage to Si and SiO₂ Substrates during Reactive Ion Etching (RIE) Processes

Monday, October 15, 2007, 8:20 am, Room 606

As the dimensions of transistors diminish in Ultra-Large-Scale Integrated (ULSI) circuits, "small" damage to the substrate materials caused by plasma etching during chip fabrication processes can have adverse effects on chip performance. In the present work, we investigate damage to Si and SiO₂ caused by energetic hydrogen injections in, for example, a reactive ion etching (RIE) process of Si with a gas containing HBr, using classical molecular dynamics (MD) simulations. In this work, we performed MD simulations of energetic hydrogen injections into Si and SiO₂ substrates and measured penetration depths of H atoms and also reaction characteristics, e.g., bond formation of injected hydrogen with substrate atoms, as functions of the injection energy in the range of 50 -200eV. As injected species, we examined both atomic and molecular hydrogen, i.e., H and H₂. It is usually difficult to determines penetration (implant) depth profiles for hydrogen experimentally, so these MD simulation may give good insight into such problems. It was found that the average penetration depth is essentially proportional to the injection energy. For Si and SiO₂ substrates, hydrogen is found to penetrate deeper in Si than in SiO₂ for the same injection energies. The penetration depth has been also found to depend only on the impact energy of each H atom whether it is injected as a hydrogen atomic or part of a hydrogen molecule. As to reaction characteristics, in the case of a SiO₂ substrate, the majority of injected hydrogen atoms are bound with substrate oxygen atoms, generating hydroxyl groups. In this case, H₂ molecules are hardly formed. Similarly, in the case of a Si substrate, the majority of injected hydrogen atoms form Si-H bonds. However, in this case, H₂ molecules can be also generated in the Si bulk. These MD simulations are based on a newly developed classical interatomic potential functions for Si, C, O, F, and H systems. The model potential functions were developed from data obtained from the density functional calculations based on Gaussian03 (B3LYP), a first-principle simulation code. We are also in the process of evaluating sputtering yields of SiOCH by energetic injections of fluorocarbon radical ions, i.e., CF_x⁺. Details of such reactions will be also discussed.