Reactive Ion Etching of Benzocyclobutene Using a Silicon Nitride Dielectric Etch Mask

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Abstract
The feasibility of patterning a cured polymeric film of benzocyclobutene (BCB) using silicon nitride as an etch mask was investigated. Due to the carbon‐ and silicon‐containing composition of BCB, a gas mixture with oxygen‐ and fluorine‐containing components is required, which unfortunately also etches . Therefore, a reactive ion etching process with high selectivity between the etch rates of the BCB, CYCLOTENE™ 3022‐46, and the was developed. We have investigated the dependence of the etch rates as a function of the content in the gas mixture. The surface morphology and the angle of the etched BCB sidewall were determined using a scanning electron microscope. A process with content was defined, exhibiting etch rates of 155 and 14 nm/min for the polymerized BCB and the , respectively. This yields a selectivity of 11:1. The morphology of the etched BCB surface is smooth. Depending on the shape of the etch mask, sidewall angles of the BCB structure between 70° and 80° were obtained. These inclinations allow an effective deposition of a contact metallization. For further technological processing, a residual dielectric film can be left on the structure when the BCB layer is etched.

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