Lateral PNP bipolar transistor with narrow trench emitter
First Claim
1. A lateral bipolar transistor, comprising:
- a semiconductor substrate of a first conductivity type;
an epitaxial layer of a second conductivity type formed on the substrate, the second conductivity type being opposite the first conductivity type;
a first buried layer of the first conductivity type and a second buried layer of the second conductivity type both formed between the substrate and the epitaxial layer, the first buried layer being located under a trench isolation structure and the second buried layer being located under a base region;
a dielectric layer formed over the epitaxial layer;
first and second trenches formed in the dielectric layer and the epitaxial layer, the trenches being tilled with at least one polysilicon layer, the polysilicon layer being insulated from at least a bottom portion of each trench by a second dielectric layer, and the polysilicon layer being doped with dopants of the first conductivity type; and
first and second diffusion regions of the first conductivity type formed in the epitaxial layer surrounding only the sidewalls of respective first and second trenches, the polysilicon layer of each trench being in electrical and physical contact with the respective diffusion region surrounding sidewalls of the respective trench, wherein an emitter region is formed in the polysilicon layer in the first trench and the first diffusion region, a collector region is formed in the polysilicon layer in the second trench and the second diffusion region, the base region being formed in the epitaxial layer between the first and second diffusion regions associated with the first and second trenches, the polysilicon layer in the first trench being formed over the dielectric layer and extending beyond the first diffusion region formed surrounding the first trench and overlying at least a portion of the base region, the extended portion of the polysilicon layer of the first trench functioning as a field plate for the base region to shield the base region from electrostatic build-up in the dielectric layer overlying the base region.
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Abstract
A lateral bipolar transistor includes trench emitter and trench collector regions to form ultra-narrow emitter regions, thereby improving emitter efficiency. The same trench process is used to form the emitter/collector trenches as well as the trench isolation structures so that no additional processing steps are needed to form the trench emitter and collector. In embodiments of the present invention, the trench emitter and trench collector regions may be formed using ion implantation into trenches formed in a semiconductor layer. In other embodiments, the trench emitter and trench collector regions may be formed by out-diffusion of dopants from heavily doped polysilicon filled trenches.
35 Citations
16 Claims
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1. A lateral bipolar transistor, comprising:
- a semiconductor substrate of a first conductivity type;
an epitaxial layer of a second conductivity type formed on the substrate, the second conductivity type being opposite the first conductivity type;
a first buried layer of the first conductivity type and a second buried layer of the second conductivity type both formed between the substrate and the epitaxial layer, the first buried layer being located under a trench isolation structure and the second buried layer being located under a base region;
a dielectric layer formed over the epitaxial layer;
first and second trenches formed in the dielectric layer and the epitaxial layer, the trenches being tilled with at least one polysilicon layer, the polysilicon layer being insulated from at least a bottom portion of each trench by a second dielectric layer, and the polysilicon layer being doped with dopants of the first conductivity type; and
first and second diffusion regions of the first conductivity type formed in the epitaxial layer surrounding only the sidewalls of respective first and second trenches, the polysilicon layer of each trench being in electrical and physical contact with the respective diffusion region surrounding sidewalls of the respective trench, wherein an emitter region is formed in the polysilicon layer in the first trench and the first diffusion region, a collector region is formed in the polysilicon layer in the second trench and the second diffusion region, the base region being formed in the epitaxial layer between the first and second diffusion regions associated with the first and second trenches, the polysilicon layer in the first trench being formed over the dielectric layer and extending beyond the first diffusion region formed surrounding the first trench and overlying at least a portion of the base region, the extended portion of the polysilicon layer of the first trench functioning as a field plate for the base region to shield the base region from electrostatic build-up in the dielectric layer overlying the base region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
- a semiconductor substrate of a first conductivity type;
Specification