Ultra dense trench-gated power device with the reduced drain-source feedback capacitance and miller charge
First Claim
1. A semiconductor device having improved and reduced Miller capacitance in a repeated cellular structure, wherein the cells of the device comprise:
- a substrate having a first layer highly doped with a first conductivity dopant and formung a drain, a second layer over the first layer and lightly doped with a first conductivity dopant, a third layer over the second layer and doped with a second conductivity dopant opposite in polarity to the first conductivity component, a fourth layer on the opposite surface of the semiconductor substrate and highly doped with a first conductivity dopant;
a trench structure extending from the fourth layer into the substrate and dividing the fourth layer into a plurality of source regions and having a sidewall adjacent the third and fourth layers for controlling a channel in the third layer, said trench having upper and lower conductive layers separated by a dielectric layer.
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Abstract
The cellular structure of the power device includes a substrate that has a highly doped drain region. Over the substrate there is a more lightly doped epitaxial layer of the same doping. Above the epitaxial layer is a well region formed of an opposite type doping. Covering the wells is an upper source layer of the first conductivity type that is heavily doped. The trench structure includes a sidewall oxide or other suitable insulating material that covers the sidewalls of the trench. The bottom of the trench is filled with a doped polysilicon shield. An interlevel dielectric such as silicon nitride covers the shield. The gate region is formed by another layer of doped polysilicon. A second interlevel dielectric, typically borophosphosilicate glass (BPSG) covers the gate. In operation, current flows vertically between the source and the drain through a channel in the well when a suitable voltage is applied to the gate.
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Citations
22 Claims
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1. A semiconductor device having improved and reduced Miller capacitance in a repeated cellular structure, wherein the cells of the device comprise:
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a substrate having a first layer highly doped with a first conductivity dopant and formung a drain, a second layer over the first layer and lightly doped with a first conductivity dopant, a third layer over the second layer and doped with a second conductivity dopant opposite in polarity to the first conductivity component, a fourth layer on the opposite surface of the semiconductor substrate and highly doped with a first conductivity dopant;
a trench structure extending from the fourth layer into the substrate and dividing the fourth layer into a plurality of source regions and having a sidewall adjacent the third and fourth layers for controlling a channel in the third layer, said trench having upper and lower conductive layers separated by a dielectric layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 21, 22)
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14. A method for forming a semiconductor device with reduced Miller capacitance comprising the steps of:
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heavily doping a substrate with a first conductivity dopant to form a drain region;
growing an epitaxial layer on the substrate and lightly doping the epitaxial layer with a dopant of the first conductivity;
implanting the surface of the epitaxial layer with dopants of a second polarity opposite in polarity to the first conductivity dopant;
covering the substrate with a trench mask having openings corresponding to desired trench regions and removing material from the exposed regions to form trenches;
growing an oxide layer on the trench walls and floor and diffusing the second conductivity dopant to form well regions adjacent the trench sidewalls;
in said trench regions forming upper and lower conductive layers and separating the layers with a first dielectric layer;
forming source regions in the surface of the epitaxial layer with dopant of the first conductivity.
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Specification