Hot-carrier shield formation for bipolar transistor
US5659197A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 23, 1994 |
| Grant date | Aug 19, 1997 |
| Priority date | — |
| Expiry date | Sep 23, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10D62/133
Abstract
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.