Semiconductor device and method of manufacture therefor
First Claim
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1. A bi-directional trench field effect power transistor, comprising:
- a substrate with a substrate top surface;
a layer stack extending over the substrate top surface, a first vertical trench and a second vertical trench being present in the layer stack, each of said first and second vertical trenches extending in a vertical direction from a top layer of the layer stack towards the substrate;
a first current terminal and a second current terminal, the first current terminal being situated in said vertical direction below the second current terminal and the second current terminal being situated on or above the top layer; and
an electrical path which can be selectively enabled or disabled to allow current to flow in a first direction or a second direction, opposite to the first direction, between the first current terminal and the second current terminal, the electrical path comprising;
a body extending laterally between the first and second vertical trenches and vertically between said first current terminal and said second current terminal;
a first drift region extending, in said vertical direction, between the body and the first current terminal;
a second drift region extending, in said vertical direction, between the body and the second current terminal;
wherein the first vertical trench and the second vertical trench have the same of option (a) and/or (b);
option (a) being;
the first and second vertical trenches extend, in said vertical direction, from said top layer beyond an upper boundary of the first drift region, and in a lateral direction parallel to the substrate top-surface electrically isolate, and define, the first drift region;
option (b) being;
each of said first and second vertical trenches comprising;
a gate electrode in an first part of the vertical trench, the gate electrode being electrically coupled to the body, for forming, when a suitable voltage is applied to the gate, a vertical channel in the body through which a current can flow from the first drift region to the second drift region or vice versa;
a lower shield plate, the shield plate being situated in a lower part of the trench, the lower part being closer to the substrate than the first part, for generating an accumulation layer in the first drift region when the lower shield plate is biased with respect to the first current terminal in a first polarity and locally reducing the electrical field density when the lower shield plate is biased with respect to the first current terminal in a second polarity; and
a body-side vertical sidewall, and another vertical sidewall facing the body-side vertical sidewall, of which at least the body-side vertical sidewall is covered with a dielectric which separates the gate electrode and the shield plate from the body-side vertical sidewall, the dielectric being thicker in the first part than in the lower part.
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Abstract
A semiconductor device comprises a first contact layer, a first drift layer adjacent the first contact layer, a buried body layer adjacent the first drift layer and a second contact layer. A first vertical trench and a second vertical trench are provided, the first and second vertical trenches being spaced with respect to each other and extending from the second contact layer to substantially beyond the buried body layer. A second drift layer is also provided and sandwiched between the buried body layer and the second contact layer.
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Citations
20 Claims
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1. A bi-directional trench field effect power transistor, comprising:
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a substrate with a substrate top surface; a layer stack extending over the substrate top surface, a first vertical trench and a second vertical trench being present in the layer stack, each of said first and second vertical trenches extending in a vertical direction from a top layer of the layer stack towards the substrate; a first current terminal and a second current terminal, the first current terminal being situated in said vertical direction below the second current terminal and the second current terminal being situated on or above the top layer; and an electrical path which can be selectively enabled or disabled to allow current to flow in a first direction or a second direction, opposite to the first direction, between the first current terminal and the second current terminal, the electrical path comprising; a body extending laterally between the first and second vertical trenches and vertically between said first current terminal and said second current terminal; a first drift region extending, in said vertical direction, between the body and the first current terminal; a second drift region extending, in said vertical direction, between the body and the second current terminal; wherein the first vertical trench and the second vertical trench have the same of option (a) and/or (b); option (a) being; the first and second vertical trenches extend, in said vertical direction, from said top layer beyond an upper boundary of the first drift region, and in a lateral direction parallel to the substrate top-surface electrically isolate, and define, the first drift region; option (b) being;
each of said first and second vertical trenches comprising;a gate electrode in an first part of the vertical trench, the gate electrode being electrically coupled to the body, for forming, when a suitable voltage is applied to the gate, a vertical channel in the body through which a current can flow from the first drift region to the second drift region or vice versa; a lower shield plate, the shield plate being situated in a lower part of the trench, the lower part being closer to the substrate than the first part, for generating an accumulation layer in the first drift region when the lower shield plate is biased with respect to the first current terminal in a first polarity and locally reducing the electrical field density when the lower shield plate is biased with respect to the first current terminal in a second polarity; and a body-side vertical sidewall, and another vertical sidewall facing the body-side vertical sidewall, of which at least the body-side vertical sidewall is covered with a dielectric which separates the gate electrode and the shield plate from the body-side vertical sidewall, the dielectric being thicker in the first part than in the lower part. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A semiconductor product, comprising:
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a plurality of power transistors, each of the power transistors comprising; a substrate with a substrate top surface; a layer stack extending over the substrate top surface, a first vertical trench and a second vertical trench being present in the layer stack, each of said first and second vertical trenches extending in a vertical direction from a top layer of the layer stack towards the substrate; a first current terminal and a second current terminal, the first current terminal being situated in said vertical direction below the second current terminal and the second current terminal being situated on or above the top layer; and an electrical path which can be selectively enabled or disabled to allow current to flow in a first direction or a second direction, opposite to the first direction, between the first current terminal and the second current terminal, the electrical path comprising; a body extending laterally between the first and second vertical trenches and vertically between said first current terminal and said second current terminal; a first drift region extending, in said vertical direction, between the body and the first current terminal; a second drift region extending, in said vertical direction, between the body and the second current terminal; wherein the first vertical trench and the second vertical trench have the same of option (a) and/or (b); option (a) being; the first and second vertical trenches extend, in said vertical direction, from said top layer beyond an upper boundary of the first drift region, and in a lateral direction parallel to the substrate top-surface electrically isolate, and define, the first drift region; option (b) being;
each of said first and second vertical trench comprising;a gate electrode in an first part of the vertical trench, the gate electrode being electrically coupled to the body, for forming, when a suitable voltage is applied to the gate, a vertical channel in the body through which a current can flow from the first drift region to the second drift region or vice versa; a lower shield plate, the shield plate being situated in a lower part of the trench, the lower part being closer to the substrate than the first part, for generating an accumulation layer in the first drift region when the lower shield plate is biased with respect to the first current terminal in a first polarity and locally reducing the electrical field density when the lower shield plate is biased with respect to the first current terminal in a second polarity; and a body-side vertical sidewall, and another vertical sidewall facing the body-side vertical sidewall, of which at least the body-side vertical sidewall is covered with a dielectric which separates the gate electrode and the shield plate from the body-side vertical sidewall, the dielectric being thicker in the first part than in the lower part; a first current electrode connected to the first current terminal of each of said power transistors; a second current electrode connected to the second current terminal of each of said power transistor; and a gate feed connected to the gate electrode of each power transistor wherein the first current electrode, second current electrode and gate feed are connectable to an external power supply. - View Dependent Claims (18, 19)
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20. A method of manufacturing a power transistor comprising:
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providing on a substrate a layer stack extending over said substrate, and providing the layer stack with a first vertical trench and a second vertical trench, each of said vertical trenches extending in a vertical direction from a top layer of the stack towards the substrate; providing a second current terminal on or above the top layer and a first current terminal, in said vertical direction, below the second current terminal; and providing an electrical path which can be selectively enabled or disabled to allow current to flow between the first current terminal and the second current terminal, providing the electrical path comprising; providing a body between said first current terminal and said second current terminal, the body extending laterally between the first and second vertical trenches and vertically; providing a first drift region, in said vertical direction, between the body and the first current terminal; and providing a second drift region, in said vertical direction, between the body and the second current terminal; providing each of said first and second vertical trenches with a gate electrode in a first part of the vertical trench, the gate electrode being electrically coupled to the body; providing a lower shield plate in a lower part of the trench closer to the substrate than the first part; and providing a body-side vertical sidewall of each of the vertical trenches with a dielectric which separates the gate electrode and the shield plate from the body-side vertical sidewall, the dielectric being thicker in the first part than in the lower part.
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Specification