Depleted base transistor with high forward voltage blocking capability
First Claim
1. A depleted base transistor comprising:
- a semiconductor substrate having first and second opposing faces;
a cathode contact on the first face;
an anode contact on the second face;
a cathode region of first conductivity type in said substrate at the first face, said cathode region forming an ohmic contact with said cathode contact;
a trench in said substrate at the first face, said trench having a trench bottom and a trench sidewall extending between the trench bottom and the first face;
a base region of first conductivity type in said substrate, between said cathode region and said anode contact, said base region comprising;
a drift region of first conductivity type having a drift region doping concentration;
a blocking voltage enhancement region of first conductivity type extending between said drift region and said cathode region, said blocking voltage enhancement region forming non-rectifying junctions with said cathode region and said drift region and having a blocking voltage enhancement region doping concentration below the drift region doping concentration;
an insulated gate electrode in said trench; and
means, comprising a rectifying junction in said substrate, for depleting said blocking voltage enhancement region of majority free carriers to thereby inhibit traversal of majority carriers from said cathode region to said drift region.
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Accused Products
Abstract
A depleted base transistor with high forward voltage blocking capability includes cathode and anode regions on opposite faces of a semiconductor substrate, a base region therebetween, a rectifying junction for depleting a portion of the base region of majority free carriers and an insulated gate electrode in a trench for modulating the conductivity of the depleted portion of the base region. The regions are formed as a vertical stack of semiconductor layers with the anode region (e.g., P+) as the bottom layer, the buffer region (e.g., N+) on the anode region, the drift region/e.g., N-) on the buffer region, the blocking voltage enhancement region (e.g., N-) on the drift region and the cathode region (e.g., N+) as the top layer on the blocking voltage enhancement region. The trench extends into the substrate at the first face so that a sidewall thereof extends adjacent the cathode region and the blocking voltage enhancement region and defines an interface between these adjacent regions and the interior of the trench which contains the insulated gate electrode. The rectifying junction is provided to deplete at least a portion of the blocking voltage enhancement region so that the P-N diode formed by the stack of anode, buffer, drift, blocking voltage enhancement and cathode regions blocks forward voltages when the insulated gate electrode is maintained at the same potential as the cathode region.
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Citations
34 Claims
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1. A depleted base transistor comprising:
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a semiconductor substrate having first and second opposing faces; a cathode contact on the first face; an anode contact on the second face; a cathode region of first conductivity type in said substrate at the first face, said cathode region forming an ohmic contact with said cathode contact; a trench in said substrate at the first face, said trench having a trench bottom and a trench sidewall extending between the trench bottom and the first face; a base region of first conductivity type in said substrate, between said cathode region and said anode contact, said base region comprising; a drift region of first conductivity type having a drift region doping concentration; a blocking voltage enhancement region of first conductivity type extending between said drift region and said cathode region, said blocking voltage enhancement region forming non-rectifying junctions with said cathode region and said drift region and having a blocking voltage enhancement region doping concentration below the drift region doping concentration; an insulated gate electrode in said trench; and means, comprising a rectifying junction in said substrate, for depleting said blocking voltage enhancement region of majority free carriers to thereby inhibit traversal of majority carriers from said cathode region to said drift region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A depleted base transistor comprising:
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a monocrystalline silicon carbide substrate; a cathode contact and an anode contact on said silicon carbide substrate; a silicon carbide cathode region of first conductivity type in said silicon carbide substrate, said silicon carbide cathode region forming an ohmic contact with said cathode contact; a silicon carbide anode region of second conductivity type in said silicon carbide substrate, said silicon carbide anode region forming an ohmic contact with said anode contact; a silicon carbide base region of first conductivity type in said substrate, between said silicon carbide cathode region and said silicon carbide anode region, said silicon carbide base region comprising; a silicon carbide drift region of first conductivity type having a drift region doping concentration; a silicon carbide blocking voltage enhancement region of first conductivity type extending between said silicon carbide drift region and said silicon carbide cathode region, said silicon carbide blocking voltage enhancement region forming non-rectifying junctions with said silicon carbide cathode region and said silicon carbide drift region and having a blocking voltage enhancement region doping concentration below the drift region doping concentration; a trench in said substrate at the first face, said trench having a trench bottom which defines an interface between said silicon carbide drift region and an interior of said trench and a trench sidewall which defines an interface between said silicon carbide blocking voltage enhancement region and the interior of said trench; an insulated gate electrode in the interior of said trench; and means, comprising a silicon carbide rectifying junction spaced from the trench sidewall and selected from the group consisting of P-N junctions and Schottky junctions, for depleting said silicon carbide blocking voltage enhancement region of majority free carriers to thereby inhibit traversal of majority carriers from said silicon carbide cathode region to said silicon carbide drift region. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A trench-gated depleted base transistor, comprising:
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a semiconductor substrate having a cathode contact and an anode contact thereon; a cathode region of first conductivity type in said substrate and forming an ohmic contact with said cathode contact; an anode region of second conductivity type in said substrate and forming an ohmic contact with said anode contact; a base region of first conductivity type in said substrate, said base region forming non-rectifying and rectifying junctions with said cathode region and said anode region, respectively, and including a drift region having a nonuniform doping profile which is monotonically decreasing in a direction from said anode region to said cathode region; a trench in said substrate, said trench having a trench sidewall which defines an interface between said nonuniformly doped drift region and an interior of said trench; an insulated gate electrode in the interior of said trench; and means, comprising a rectifying junction spaced from the trench sidewall, for depleting said nonuniformly doped drift region of majority free carriers to thereby inhibit traversal of majority carriers from said cathode region to said anode region when said anode region is forward biased relative to said cathode region. - View Dependent Claims (20, 21, 22, 23)
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24. A depleted base transistor comprising:
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a semiconductor substrate having first and second opposing faces; a cathode contact on the first face; an anode contact on the second face; an anode region, buffer region, drift region, blocking voltage enhancement region, cathode region and collector region in said substrate, said anode region, buffer region, drift region, blocking voltage enhancement region and cathode region being arranged to respectively form a P+N+N-N-N+ diode from said anode contact to said cathode contact, said anode region, buffer region, drift region, blocking voltage enhancement region and collector region being arranged respectively to form a P+N+N-N-P+ bipolar junction transistor from said anode contact to said cathode contact and wherein an N-type conductivity of said blocking voltage enhancement region is less than about one half times an N-type conductivity type of said drift region; a trench in said substrate at the first face, said trench having a trench bottom and a trench sidewall extending between the trench bottom and the first face and adjacent the blocking voltage enhancement region; and an insulated gate electrode in said trench and positioned relative to said blocking voltage enhancement region so that the application of a bias to said insulated gate electrode causes the formation of an accumulation layer of majority free carriers adjacent the trench sidewall, between said cathode region and said drift region. - View Dependent Claims (25, 26)
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27. A depleted base transistor comprising:
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a semiconductor substrate having first and second opposing faces; a cathode contact on the first face; an anode contact on the second face; an N-type cathode region in said substrate at the first face, said cathode region forming an ohmic contact with said cathode contact; a P-type anode region in said substrate at the second face, said anode region forming an ohmic contact with said anode contact; a trench in said substrate at the first face, said trench having a trench bottom and a trench sidewall extending between the trench bottom and the first face; an N-type base region of first conductivity type in said substrate, said N-type base region extending between said N-type cathode region and said P-type anode region and forming a non-rectifying junction with said N-type cathode region; a P-type polycrystalline silicon insulated gate electrode in said trench; and means, comprising a rectifying junction in said substrate and adjacent the first face, for depleting a portion of said N-type base region of N-type carriers to thereby inhibit traversal of majority carriers from said N-type cathode region to said P-type anode region when said P-type anode region is forward biased relative to said N-type cathode region. - View Dependent Claims (28)
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29. A depleted base transistor comprising:
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a monocrystalline silicon carbide substrate having first and second opposing faces; a cathode contact and an anode contact on the first and second opposing faces of said silicon carbide substrate, respectively; an N-type silicon carbide cathode region in said silicon carbide substrate, said silicon carbide cathode region forming an ohmic contact with said cathode contact; an N-type silicon carbide base region in said substrate, between said silicon carbide cathode region and the second face, said silicon carbide base region comprising; a silicon carbide buffer region adjacent the second face, said silicon carbide buffer region forming an ohmic contact with said anode contact; a silicon carbide drift region of first conductivity type having a drift region doping concentration and forming a non-rectifying junction with said silicon carbide buffer region; a silicon carbide blocking voltage enhancement region of first conductivity type extending between said silicon carbide drift region and said silicon carbide cathode region, said silicon carbide blocking voltage enhancement region forming non-rectifying junctions with said silicon carbide cathode region and said silicon carbide drift region and having a blocking voltage enhancement region doping concentration below the drift region doping concentration; a trench in said substrate at the first face, said trench having a trench bottom which defines an interface between said silicon carbide drift region and an interior of said trench and a trench sidewall which defines an interface between said silicon carbide blocking voltage enhancement region and the interior of said trench; an insulated gate electrode in the interior of said trench; and means, comprising a silicon carbide rectifying junction spaced from the trench sidewall and selected from the group consisting of P-N junctions and Schottky junctions, for depleting said silicon carbide blocking voltage enhancement region of majority free carriers to thereby inhibit traversal of majority carriers from said silicon carbide cathode region to said silicon carbide drift region. - View Dependent Claims (30, 31, 32, 33, 34)
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Specification