Schottky barrier rectifiers and methods of forming same
First Claim
1. A Schottky rectifier, comprising:
- a semiconductor substrate having first and second opposing faces;
a cathode region of first conductivity type in said semiconductor substrate, adjacent the first face;
a drift region of first conductivity type in said semiconductor substrate, said drift region extending between said cathode region and the second face and having a concentration of first conductivity type dopants therein which increases monotonically in a direction from the second face to said cathode region;
a cathode electrode contacting said cathode region;
a trench in said semiconductor substrate at the second face, said trench having a bottom and sidewall extending adjacent said drift region;
an insulating region on the sidewall; and
an anode electrode on the second face and on said insulating region, said anode electrode forming a Schottky rectifying junction with said drift region at the second face.
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Accused Products
Abstract
A Schottky rectifier includes MOS-filled trenches and an anode electrode at a face of a semiconductor substrate and an optimally nonuniformly doped drift region therein which in combination provide high blocking voltage capability with low reverse-biased leakage current and low forward voltage drop. The nonuniformly doped drift region contains a concentration of first conductivity type dopants therein which increases monotonically in a direction away from a Schottky rectifying junction formed between the anode electrode and the drift region. A profile of the doping concentration in the drift region is preferably a linear or step graded profile with a concentration of less than about 5×1016 cm-3 (e.g., 1×1016 cm-3) at the Schottky rectifying junction and a concentration of about ten times greater (e.g., 3×1017 cm-3) at a junction between the drift region and a cathode region. The thickness of the insulating regions (e.g., SiO2) in the MOS-filled trenches is also greater than about 1000 Å to simultaneously inhibit field crowding and increase the breakdown voltage of the device. The nonuniformly doped drift region is preferably formed by epitaxial growth from the cathode region and doped in-situ.
194 Citations
38 Claims
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1. A Schottky rectifier, comprising:
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a semiconductor substrate having first and second opposing faces; a cathode region of first conductivity type in said semiconductor substrate, adjacent the first face; a drift region of first conductivity type in said semiconductor substrate, said drift region extending between said cathode region and the second face and having a concentration of first conductivity type dopants therein which increases monotonically in a direction from the second face to said cathode region; a cathode electrode contacting said cathode region; a trench in said semiconductor substrate at the second face, said trench having a bottom and sidewall extending adjacent said drift region; an insulating region on the sidewall; and an anode electrode on the second face and on said insulating region, said anode electrode forming a Schottky rectifying junction with said drift region at the second face. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A Schottky rectifier, comprising:
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a semiconductor substrate having first and second opposing faces; a first trench in said semiconductor substrate at the second face; an insulating region on a sidewall and bottom of said first trench; a cathode region of first conductivity type in said semiconductor substrate, adjacent the first face; a cathode electrode electrically coupled to said cathode region, at the first face; an anode electrode on the second face and on said insulating region; and a drift region of first conductivity type in said semiconductor substrate, said drift region forming a Schottky rectifying junction with said anode electrode, extending between said cathode region and the second face and having a concentration of first conductivity type dopants therein which is nonuniform in a direction orthogonal to the second face so that when said anode electrode is reverse biased relative to said cathode electrode an electric field profile which is entirely monotonically decreasing in a direction from the second face to said cathode region is established in said drift region. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A Schottky rectifier, comprising:
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a semiconductor substrate having first and second opposing faces, a pair of adjacent trenches of first depth at the second face, a cathode region of first conductivity type extending adjacent the first face and a drift region extending from said cathode region and between the pair of adjacent trenches to the second face, said drift region having a concentration of first conductivity type dopants therein which is nonuniform in a direction orthogonal to the second face; an insulating region on sidewalls of the pair of adjacent trenches; an anode electrode on said insulating region and on the second face, said anode electrode forming a Schottky barrier rectifying junction with said drift region at the second face; a cathode electrode on the first face; and wherein the nonuniformity of the concentration of first conductivity type dopants in said drift region is selected so that at the onset of reverse-bias breakdown of the Schottky barrier rectifying junction, the electric field in said drift region at a first position, which is equidistant from each of the pair of adjacent trenches and spaced from the second face by a distance equal to one-half the first depth, is greater than one-half the electric field in said drift region at a second position at the second face which is equidistant from each of the pair of trenches. - View Dependent Claims (25, 26, 27, 28, 29)
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30. A Schottky rectifier, comprising:
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a silicon cathode region of first conductivity type; a nonuniformly doped silicon drift region of first conductivity type on said silicon cathode region and forming a non-rectifying junction therewith, said drift region having a face thereon and a thickness of at least about 3.5 μ
m as measured between the face and the non-rectifying junction;first and second adjacent trenches having depths of at least about 3.0 μ
m, at the face;an insulating region having a thickness greater than about 1500 Å
on sidewalls of the first and second adjacent trenches;an anode electrode on said insulating region and forming a Schottky barrier rectifying junction having a reverse-bias breakdown voltage greater than about 50 Volts with said drift region, at the face; and a cathode electrode on said cathode region. - View Dependent Claims (31, 32)
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33. A Schottky rectifier, comprising:
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a semiconductor substrate having first and second opposing faces and a drift region therein extending to the second face; first and second adjacent trenches of first depth at the second face, said first and second adjacent trenches having sidewalls and bottoms extending adjacent said drift region; first and second electrically insulating regions lining the sidewalls and bottoms of the first and second adjacent trenches, respectively; an anode electrode on said first and second electrically insulating regions and on the second face, said anode electrode forming a Schottky barrier rectifying junction with said drift region at the second face; a cathode electrode electrically coupled to said drift region; wherein said drift region has a concentration of first conductivity type dopants therein which is nonuniform in a direction orthogonal to the second face; and wherein the nonuniformity of the concentration of first conductivity type dopants in said drift region is selected so that at the onset of reverse-bias breakdown of the Schottky barrier rectifying junction, the electric field in said drift region at a first position, which is equidistant from each of said first and second adjacent trenches and spaced from the second face by a distance equal to one-half the first depth, is greater than one-half the electric field in said drift region at a second position at the second face which is equidistant from each of said first and second adjacent trenches. - View Dependent Claims (34, 35, 36, 37, 38)
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Specification