| AVS 56th International Symposium & Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS1-TuM |
| Session: | Advanced FEOL and BEOL Etch |
| Presenter: | A. Paterson, Lam Research |
| Authors: | A. Paterson, Lam Research T. Panagopoulos, Lam Research S. Sriraman, Lam Research A. Sato, Lam Research N. Benjamin, Lam Research N. Williams, Lam Research C. Lee, Lam Research Y. Yamaguchi-Adams, Lam Research A. Eppler, Lam Research L. Braly, Lam Research T. Kim, Lam Research H. Singh, Lam Research V. Vahedi, Lam Research |
| Correspondent: | Click to Email |
The continued scaling in semiconductor industry provides new challenges for etching Shallow Trench Isolation (STI) features to create active area islands. Control of the STI profile is of primary importance, e.g. trench angle control of 88o ± 0.2o being requested across a 300 mm wafer, along with the additional demand to control the trench depth range non-uniformity to <2.5%, for ~2500-3000 Å trench depth. Typically, the stringent profile control requirements are met by operating halogen based Transformer Coupled Plasma (TCPTM) plasmas in the mid-pressure operating regime, 20mT to 60mT. However, in this regime the trench depth non-uniformity is upward of 5% and has a characteristic wafer pattern that resembles a “donut”, which is due to the electron mean free path, λmfp, being short (e.g. 0.85cm for 20mT Cl2) compared to the chamber dimensions. The electrons and ions are predominately produced in the TCP’s torroidal power deposition region, with the torroid pattern then being transferred to the wafer plane through ion diffusion. The trench depth pattern can be substantially reduced by operating at lower pressure <5mT, such that the λmfp is comparable to the chamber dimensions and energized electrons can ionize neutrals with almost equal efficiency across the chamber, where the shape of the plasma density determined only by ambipolar diffusion. However, this severely inhibits profile control with trench angle and selectivity requirements not being met.
This paper will discuss the work undertaken at Lam Research to characterize halogen plasma’s produced by the TCP configuration of a KiyoTM process chamber. Plasma diagnostic and simulation data shows that the plasma density uniformity can be substantially improved for a given pressure operation regime by optimizing the TCP hardware configuration. This optimization will translated into achieving <2.5% trench depth uniformity at mid pressure operation whilst maintaining profile control. Future challenges facing STI trench depth etch will also be discussed.