| 摘要 |
The present invention provides a bipolar transistor in which a lightly doped n-type hot-carrier shield extends in an epitaxial layer adjacent from a poly-emitter to an extrinsic base. This hot-carrier shield minimizes performance impairment that would otherwise occur due to a hot-carrier effect. Key steps in the method of making the bipolar transistor include a differential thermal oxidation while the poly-emitter is covered with a nitride cap. After the nitride cap is removed, an n-type dopant is implanted. The unprotected poly emitter is heavily doped. The implant partially penetrates a relatively thin oxide growth, thereby forming the hot-carrier shield. Other areas, such as the extrinsic base, and a polycrystalline base extension are covered by a relatively thick oxide growth and are unaffected by the n-type implant.
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