| 摘要 |
A first (e.g. replaceable or disposable) dielectric spacer formed on a sidewall of a dummy emitter mandrel is removed after a raised extrinsic base layer and covering dielectric layer are formed. Thereafter, a second dielectric spacer is formed within the opening that results. As a result, the second dielectric spacer, which is not subjected to RIE processing, provides a desired level of isolation and tighter emitter final critical dimension than that which could be achieved through the technique described in the prior art. In a particular embodiment, an additional layer of silicon nitride is disposed over a passivation oxide layer as a sacrificial layer which protects the passivation oxide layer from being reduced in thickness and/or being undercut during the RIE process and one or more cleaning processes conducted after the RIE process.
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