| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoA |
| Session: | Advanced BEOL/Interconnect Etching |
| Presenter: | Shuo Huang, University of Michigan |
| Authors: | S. Huang, University of Michigan C.M. Huard, University of Michigan S. Shim, Samsung Electronics Co., Ltd. S. Lee, Samsung Electronics Co., Ltd. I.-C. Song, Samsung Electronics Co., Ltd. S. Lu, Samsung Electronics Co., Ltd. M.J. Kushner, University of Michigan |
| Correspondent: | Click to Email |
As feature sizes continue to shrink and aspect ratios continue to increase in semiconductor processing, maintaining critical dimensions (CDs) of the features becomes more challenging. This is particularly the case for dielectric etch of high aspect ratio (AR) contacts (HARC), in which aspect ratios of 50-100 are desired. Our interests in this investigation are two challenges in the reactive ion etching of HARC in SiO2 using Ar/C4F8/O2 mixtures. The first is aspect ratio dependent etching (ARDE) where etch rates generally decrease as AR increases. The second is the origin of non-circular vias from nominally initially circular mask openings.
We report on results from a computational investigation of etching of HARCs in SiO2 using Ar/C4F8/O2 mixtures in a tri-frequency capacitively coupled plasma. Modeling of reactor scale and surface chemistry was performed using the Hybrid Plasma Equipment Model (HPEM). The feature scale modeling was performed using a 3-dimensional implementation of the Monte Carlo Feature Profile Model (MCFPM). The reactor utilizes 3 frequencies, two lower frequencies generally less than 10 MHz and 1 higher frequency of 50-100 MHz. For total powers approaching and exceeding10 kW, radical fluxes to the wafer are dominated by CFx, O and F due to there being significant dissociation of feedstock gas. Ion fluxes are dominated by Ar+ and CnFx+.
The general trend of ARDE is observed - etch rates decrease with etch depth within a feature and features simultaneously etched show lower etch rates in smaller features. However, peaks in the instantaneous etch rate may occur when the profile becomes tapered, which funnels hot neutrals to the etch front. Factors contributing to ARDE such as molecular transport of neutral species, shading of ions with non-normal incidence and etch front geometry will be discussed. The origin of non-circular vias is likely due to small asymmetries and imperfections in the mask, which are reinforced during the etch process.
Work was supported by Samsung Electronics Ltd., Department of Energy Office of Fusion Energy Science and the National Science Foundation.