| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS+MN-WeM |
| Session: | Plasma Processing for 3D Integration, TSV, and MEMS |
| Presenter: | T. Tillocher, GREMI, France |
| Authors: | T. Tillocher, GREMI, France J. Ladroue, GREMI - STMicroelectronics, France F. Moro, GREMI, France G. Gommé, GREMI, France P. Lefaucheux, GREMI, France M. Boufnichel, STMicroelectronics, France P. Ranson, GREMI, France R. Dussart, GREMI, France |
| Correspondent: | Click to Email |
The STiGer cryoetching process can be alternatively used to the Bosch process or the cryogenic process to etch high aspect ratio structures. It has been developed thanks to our knowledge of the passivation mechanisms in cryoetching. In the standard cryogenic process, patterned Si substrates cooled down to very low temperatures are exposed to continuous SF6/O2 plasmas. A SiOxFy-type passivation layer is formed on the sidewalls and prevents etching. This film has the property to desorb under ion bombardment or when the substrate is heated. We also showed that SiF4/O2 plasmas can be used to create or reinforce a passivation layer in cryogenic etching.
The STiGer process consists of cycling passivation steps (SiF4/O2 plasmas) and etching steps to get vertical structures. The etching steps can be either isotropic (SF6 plasmas) or anisotropic (SF6/O2 plasmas). Like the cryogenic process, it is required to cool the Si substrate with liquid nitrogen.
The STiGer process combines advantages of both Bosch process and cryogenic process. Due to the cyclic passivation steps, the SiOxFy film is stronger than in “standard” cryoetching. In addition, the passivation layer desorbs when the substrate is heated back to room temperature. Thus, unlike the Bosch process, there is no need to clean the microstructures and the chamber walls after each process run. Moreover, the robustness is enhanced in comparison with “standard” cryoetching : the profiles are less sensitive to temperature variations.
But, like the standard cryogenic process, a cooling is required and like in Bosch etching, a scalloping is present on the sidewalls. However, it is possible to minimize this effect by tuning the etching and the deposition steps.
We will present our most recent performances with the STiGer process. Our objectives are to etch sub-micron trenches and holes that will be further used for the realization of integrated capacitors and Through Silicon Vias (TSV). But obviously, the STiGer process can be utilized for silicon micromachining in general.
Finally, we will see how such a process can amplify Columnar MicroStructures (CMS).