| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS1-ThM |
| Session: | Modeling of Plasmas and Plasma-Surface Interactions |
| Presenter: | Guillaume Le Dain, Institut des Matériaux Jean Rouxel – Université de Nantes, France |
| Authors: | G. Le Dain, Institut des Matériaux Jean Rouxel – Université de Nantes, France A. Rhallabi, Institut des Matériaux Jean Rouxel – Université de Nantes, France M. Boufnichel, ST Microelectronics, France F. Roqueta, ST Microelectronics, France |
| Correspondent: | Click to Email |
Deep silicon etching is now used in many semi-conductor devices such as high power devices, Micro-Electro-Mechanical-Systems (MEMS) and Systems In Package (SIP). The aim of deep silicon etching is to perform high aspect ratio profiles with a minimum of geometrical defects such as roughness and undercut. Bosch process is one of dry etching processes used for silicon deep etching. It is based on cyclic process consisting of alternating etching and deposition pulses. The optimization of this kind of etching processes for different applications requires a good understanding of the plasma surface interactions. Etching simulator can be considered as a complementary tool to improve the quality and the reliability of the silicon etch profile. In this context, we have developed a multi-scale approach to simulate the silicon etch profile evolution as a function of the operating conditions of Bosch process, performed in ICP reactor. Etching pulse is ensured by SF6/Ar plasma mixture while the deposition pulse is ensured by C4F8 plasma.
Our silicon etching simulator is thus composed of three models:
- 0D plasma kinetic models of SF6 and C4F8
- Sheath models of SF6 and C4F8
- 2D Surface model
0D kinetic model is based on the solving of the mass balance equations of all neutral and ion species considered in the reaction scheme coupled to charge neutrality equation and power balance equation. The solving of the non linear equation system, until it reaches to steady state. This solving allows to calculate the fluxes of neutral and ion species as well as the electron density and temperature. Those information are introduced as input data in the sheath and etching models. The sheath model provides angular and energetic ion distribution functions which are required in the quantification of the ion sputtering on the local etched surface.
The surface model is the third model which is based on the cellular Monte-Carlo method to describe the plasma surface interactions in a probabilistic way for silicon etching through the mask. Atomic fluorine and positive ions produced during SF6 plasma discharge are considered as the reactive species in the etching process steps while the CxFy radicals and positive ions are considered as the reactive species in the surface passivation steps.
The simulation results show the pressure variation which affects the etch profile especially the scalloping and the undercut effects. On the other hand the comparisons between the simulation and the experiment in terms of trenches aspect show a satisfactory agreement.