AVS 62nd International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThP

Paper PS-ThP12
Simulation of Deep Silicon Etching under Cryogenic ICP SF6/O2/Ar Plasma Mixture using multi-Scale Approach

Thursday, October 22, 2015, 6:00 pm, Room Hall 3

Session: Plasma Science and Technology Poster Session
Presenter: Ahmed Rhallabi, Université de Nantes, France
Authors: Y. Haidar, Université de Nantes, France
A. Rhallabi, Université de Nantes, France
A. Pateau, Université de Nantes, France
A. Mokrani, Université de Nantes, France
F. Taher, Université Libanaise, Lebanon
Correspondent: Click to Email
SF6 based plasma is widely used in the dry etching of silicon. In many new devices manufacturing such as Systems in Packages (SIP) or Micro-Electro-Mechanical Systems (MEEMS), deep etching of silicon without any local morphological defects like bowing, undercut or trenching is required. Cryogenic silicon etching is used by adding oxygen in order to inhibit the sidewall etching and then improve the silicon etch anisotropy. The fraction of oxygen in SF6/O2/Ar plasma mixture is one of the critical parameters in the control of this process.

In order to know more about the plasma surface interaction in cryogenic ICP silicon etching process, we have developed silicon etching simulator. The model is composed of three modules: plasma kinetic model, sheath model and etching model. The plasma kinetic model is based on the 0D global approach which allows the calculation of the average densities and fluxes of neutral and ion species as well as the electron density and temperature in ICP SF6/O2/Ar plasma mixture versus the ICP machine parameters. Such output parameters are introduced as input parameters in the sheath model and silicon etching model. Cellular Monte-Carlo method is used to describe the plasma surface interactions in a probabilistic way for silicon etching trough the mask.

The aim of this work is to validate the set of simulation and show the influence of some input parameters (Rf power, pressure, gas flow rates and bias voltage) on the etching processes.

Particular attention is paid on the study of the effect of the oxygen fraction on the evolution of both the SF6/O2/Ar plasma kinetic and the silicon etch profile trough the mask. The simulations results show that up to 10% of O2, diminution of the undercut characterized by the surface etching under the mask is observed while beyond this value, the etching rate is considerably decreased. This is due to the domination of the passivation process by oxygen on the silicon trench bottom.