Fast recovery reduced p-n junction rectifier
First Claim
1. A rectifier device, which comprises:
- a n-type semiconductor substrate being a wafer;
a top metal layer having a first side and a second side disposed above said semiconductor substrate;
a backside layer disposed immediately below said semiconductor substrate, diffusion to said backside layer using same polarity species as said semiconductor substrate;
one or more reduced p-n junction structures disposed between said top metal layer and said semiconductor substrate, wherein each of said reduced p-n junction structures has a thin film of first p-type doping on top of a second p-type doping and the doping concentration of said first p-type is higher than said second p-type to create an early termination at p-side such that a total charge within the depletion region of said p-n junction is reduced, wherein the interface between said top metal layer and said first p-type at p-side is an ohmic contact; and
a plurality of edge termination structures formed proximate said first side and said second side of said top metal layer, and above said semiconductor substrate for protection purpose and sustaining high voltage.
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Abstract
A fast recovery rectifier structure with the combination of Schottky structure to relieve the minority carriers during the forward bias condition for the further reduction of the reverse recovery time during switching in addition to the lifetime killer such as Pt, Au, and/or irradiation. This fast recovery rectifier uses unpolished substrates and thick impurity diffusion for low cost production. A reduced p-n junction structure with a heavily doped film is provided to terminate and shorten the p-n junction space charge region. This reduced p-n junction with less total charge in the p-n junction to further improve the reverse recovery time. This reduced p-n junction can be used alone, with the traditional lifetime killer method, with the Schottky structure and/or with the epitaxial substrate.
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Citations
16 Claims
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1. A rectifier device, which comprises:
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a n-type semiconductor substrate being a wafer; a top metal layer having a first side and a second side disposed above said semiconductor substrate; a backside layer disposed immediately below said semiconductor substrate, diffusion to said backside layer using same polarity species as said semiconductor substrate; one or more reduced p-n junction structures disposed between said top metal layer and said semiconductor substrate, wherein each of said reduced p-n junction structures has a thin film of first p-type doping on top of a second p-type doping and the doping concentration of said first p-type is higher than said second p-type to create an early termination at p-side such that a total charge within the depletion region of said p-n junction is reduced, wherein the interface between said top metal layer and said first p-type at p-side is an ohmic contact; and a plurality of edge termination structures formed proximate said first side and said second side of said top metal layer, and above said semiconductor substrate for protection purpose and sustaining high voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A rectifier device for reducing reverse recovery time, which comprises:
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a n-type semiconductor substrate being a wafer, wherein said semiconductor substrate including one or more lifetime killer materials selected from the group consisting of Pt and Au; an epitaxial layer disposed above said semiconductor substrate, said epitaxial layer having same polarity but lower doping concentration than said semiconductor substrate; a plurality of reduced p-n junction anodes disposed in said epitaxial layer, wherein each of said reduced p-n junction anodes having opposite polarity to said epitaxial layer and said reduced p-n junction has a thin film of first p-type doping on top of a second p-type doping and the doping concentration of said first p-type is higher than said second p-type to create an early termination at p-side such that a total charge within the depletion region of said p-n junction is reduced, and the doping concentration of said second p-type of said reduced p-n junction is about 2 to about 10 times of n region; a plurality of Schottky contact regions disposed in said epitaxial layer and spaced apart by said p-n junction anodes, wherein said Schottky contact regions are the masked region of photo resist and oxide layer; a top metal layer having a first side and a second side, disposed above said reduced p-n junction anodes, wherein said top metal layer including one or more materials selected from the group consisting of Pt, Au, Ni, Mo, W, Cr and Ti; a plurality of guard rings disposed in said epitaxial layer and near said first side and second side of said top metal layer for high voltage purpose, wherein said guard rings having opposite polarity to said epitaxial layer; an insulation layer of oxide silicon, said insulation layer disposed above and adjacent to each of said guard rings to protect said guard rings; a backside layer having same polarity and disposed below said semiconductor substrate, wherein the doping concentration of said backside layer is higher than said semiconductor substrate; and a bottom layer disposed below said backside layer and made by a metallization process or Ni plating.
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Specification