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Selective deep-Si-trench etching with dimensional control

The recent development of a high-aspect ratio Si etch (HARSE) process has enabled the fabrication of a variety of Si structures where deep trench etching is necessary. The HARSE process relies on the formation of a sidewall etch inhibitor to prevent lateral etching of the Si structures during exposure to an aggressive SF6/Ar plasma etch chemistry. The process yields highly anisotropic profiles with excellent dimensional control for high aspect ratio features. In this study, Si etch rates and etch selectivities to photoresist are reported as a function of chamber pressure, cathode rf-power, ICP source power, and gas flow. Si etch rates greater than 3 micrometer/min with etch selectivities to resist greater than 75:1 were obtained. Lateral dimensional control, etch selectivities to SiO2 and Si3N4, and aspect ratio dependent etching (ARDE) will also be discussed.