| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoM |
| Session: | Advanced FEOL/Gate Etching |
| Presenter: | Sonam Sherpa, Tokyo Electron Ltd. |
| Authors: | S.D. Sherpa, Tokyo Electron Ltd. P. Chan, Tokyo Electron Ltd. A. Ranjan, Tokyo Electron Ltd. |
| Correspondent: | Click to Email |
Sidewall image transfer (SIT) is an indirect patterning method that involves the deposition and etching of silicon nitride spacer to achieve sub-lithographic linewidths. Current approaches to etch silicon nitride spacer face two main challenges — footing and corner rounding. Solution to these problems requires a non-polymerizing chemistry that must be anisotropic and yet avoids the adverse impact of ion-bombardment. To this end, an alternative etching process based on the modification of silicon nitride by light ions followed by the selective removal of the modified layers by DHF has already been reported [1]. However, this process uses non-compatible etch techniques (dry and wet etch). To overcome this challenge, we have developed a plasma-based alternative to DHF. After the spacer etch, isotropic etching of silicon with infinite selectivity to the nitride spacer and underlying oxide is required for mandrel pull. Current methods used to etch silicon involve the redeposition of etch by-products and bombardment by energetic ions. Therefore, these processes are not isotropic and result in footing and significant damage to the underlying material.
In this presentation, we will demonstrate the feasibility of our approach to etch silicon nitride spacer without any footing and corner rounding. In addition, damage to the underlying oxide is negligible. We will also discuss the effects of non-idealities such as scattering and deflection of ions during the hydrogen plasma treatment and the incoming topographical defect on the etch profile. In addition, we will demonstrate the feasibility of novel strategies for isotropic etching of silicon with infinite selectivity to oxide, nitride, and other materials. These processes are by-product free and we do observe any footing. In addition, damage to the underlying material is negligible.
1. N. Posseme,O. Pollet, and S. Barnola, Appl. Phys. Lett., 105, 051605 (2014).