Planarization of deep trenches

Cristina R. Rusu; Gerard Klaasse; Sherif Sedky; Heleen Esch; Brigitte Parmentier; Agnes Verbist; Ann Witvrouw

doi:10.1117/12.442970

28 September 2001 Planarization of deep trenches

Cristina R. Rusu, Gerard Klaasse, Sherif Sedky, Heleen Esch, Brigitte Parmentier, Agnes Verbist, Ann Witvrouw

Author Affiliations +

Proceedings Volume 4557, Micromachining and Microfabrication Process Technology VII; (2001) https://doi.org/10.1117/12.442970
Event: Micromachining and Microfabrication, 2001, San Francisco, CA, United States

Abstract

The ability of various deposition processes and materials to fill and planarize topographical features (trenches deeper than 10 micrometers ) is investigated in this work. Three different deposition processes are considered: LPCVD (Ge), PECVD (Ge, Si₃N₄, SiO₂) and spin coating (BCB, resist, polyimide). Comparing LPCVD and PECVD processes show that, for the same trench width, thick PECVD layers can close off trenches from the top, while thick LPCVD layers fill the trenches completely. The use of PECVD layers is thus advantageous for sealing applications, where a low bottom step coverage is desired. LPCVD layers on the other hand are very useful for planarization purposes where a low ratio between the deposited film thickness and the planarized trench width is desired. Also the deposition of polymers by spin coating yields excellent planarization results with a simpler process and lower thermal budget compared to LPCVD processes. All polymers investigated fill the trenches totally. If these planarization layers are used as sacrificial layers, they should be etched isotropically and selectively with respect to the structural layer. Ge can be etched in oxidizing solutions (H₂O₂/H₂O) and the sacrificial etch of Ge is selective towards Si, SiO₂ and many other layers. SiO₂ can be removed by wet or vapor HF, and resist, polyimide and BCB can be removed by O₂ or O₂/SF₆ plasma. Which layer should be used depends on the trench fill requirements, the thermal budget and the further processing needed.

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Cristina R. Rusu, Gerard Klaasse, Sherif Sedky, Heleen Esch, Brigitte Parmentier, Agnes Verbist, and Ann Witvrouw "Planarization of deep trenches", Proc. SPIE 4557, Micromachining and Microfabrication Process Technology VII, (28 September 2001); https://doi.org/10.1117/12.442970

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