Bipolar transistor structure using ballast resistor
US5374844A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 17, 1994 |
| Grant date | Dec 20, 1994 |
| Priority date | — |
| Expiry date | Feb 17, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10D84/125
Abstract
A transistor structure incorporates a polysilicon layer which is doped with N-type dopants and is used as an emitter ballast resistor in an array of NPN transistors. In one embodiment, the polysilicon layer is also used as a diffusion source to form N-type emitter regions within a deep and high resistivity P-well, which acts as a relatively high value base ballast resistor for the transistor. In another embodiment, a standard base is used, contributing little base ballast resistance. A buried collector region carries collector current. Preferably, the emitter regions are formed as oblong strips. P-type base contact regions, also generally formed as oblong strips, are formed in the surface of this P-well parallel to the emitter regions. The dimensions of the base contact regions may be varied in order to achieve a constant base-emitter voltage along the entire length of each emitter strip. An emitter metal layer overlies the polysilicon layer and contacts the polysilicon layer through openings in an insulating layer. The resulting three dimensional structure in one embodiment thus incorporates a stacked collector region, base ballast resistor, base region, emitter regions, emitter b…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.