Structures of and methods of fabricating trench-gated MIS devices
First Claim
1. A trench-gated MIS device formed in a semiconductor chip and comprising:
- an active area containing transistor cells;
a gate metal area containing no transistor cells; and
a gate metal layer, wherein a trench is formed in a pattern on a surface of the semiconductor chip, the trench extending from the active area into the gate metal area, the trench having walls lined with a layer of an insulating material, a conductive gate material being disposed in the trench, a top surface of the conductive gate material being at a level below a top surface of the semiconductor chip, a nonconductive layer overlying the active and gate metal areas, an aperture being formed in the nonconductive layer over a portion of the trench in the gate metal area, the aperture being filled with a gate metal such that the gate metal contacts the gate material in an area of contact within the trench.
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Accused Products
Abstract
In a trench-gated MIS device contact is made to the gate within the trench, thereby eliminating the need to have the gate material, typically polysilicon, extend outside of the trench. This avoids the problem of stress at the upper corners of the trench. Contact between the gate metal and the polysilicon is normally made in a gate metal region that is outside the active region of the device. Various configurations for making the contact between the gate metal and the polysilicon are described, including embodiments wherein the trench is widened in the area of contact. Since the polysilicon is etched back below the top surface of the silicon throughout the device, there is normally no need for a polysilicon mask, thereby saving fabrication costs.
82 Citations
48 Claims
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1. A trench-gated MIS device formed in a semiconductor chip and comprising:
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an active area containing transistor cells;
a gate metal area containing no transistor cells; and
a gate metal layer, wherein a trench is formed in a pattern on a surface of the semiconductor chip, the trench extending from the active area into the gate metal area, the trench having walls lined with a layer of an insulating material, a conductive gate material being disposed in the trench, a top surface of the conductive gate material being at a level below a top surface of the semiconductor chip, a nonconductive layer overlying the active and gate metal areas, an aperture being formed in the nonconductive layer over a portion of the trench in the gate metal area, the aperture being filled with a gate metal such that the gate metal contacts the gate material in an area of contact within the trench. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A process of fabricating an MIS device comprising:
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forming a trench in a surface of a semiconductor chip;
forming a nonconductive layer on a wall of the trench;
depositing a layer of a conductive gate material such that the gate material overflows onto the surface of the semiconductor chip outside the trench; and
etching the gate material such that a top surface of the gate material is reduced to a level below the surface of the semiconductor chip in all areas of the chip. - View Dependent Claims (21)
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22. A process of fabricating an MIS device, the device comprising an active region and a termination region, comprising:
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forming a trench mask over the surface of a semiconductor substrate, the substrate being doped with material of a first conductivity type, the trench mask having an aperture defining the location of a termination trench to be formed;
etching through the aperture in the trench mask to form a termination trench in the substrate;
removing the trench mask;
forming a first nonconductive layer on a wall of the termination trench;
depositing a layer of a conductive gate material into the termination trench, the conductive gate material overflowing the surface of the substrate outside the termination trench;
etching the gate material without a mask such that a top surface of the gate material in the termination trench is reduced to a level below the surface of the substrate;
depositing a second nonconductive layer over the surface of the substrate, forming a contact mask over the second nonconductive layer, the contact mask having a gate contact aperture;
etching the second nonconductive layer through the gate contact aperture in the contact mask to form a gate contact aperture in the second nonconductive layer;
removing the contact mask; and
depositing a second conductive layer over the second nonconductive layer, the second conductive layer extending through the gate contact aperture to make contact with the conductive gate material in the termination trench. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. A process of fabricating an MIS device comprising:
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providing a semiconductor substrate doped with dopant of a first conductivity type;
growing an epitaxial layer of a second conductivity type on a semiconductor substrate;
forming a trench mask over the surface of the epitaxial layer, the trench mask having a first aperture in an active region of the device and a second aperture in a termination region of the device, the termination region being located between the active region and a channel stopper region;
etching the epitaxial layer through the first and second apertures in the trench mask to form first and second trenches, the second trench being substantially wider than the first trench;
removing the trench mask;
forming a first nonconductive layer on a wall of the first and second trenches;
depositing a layer of a conductive gate material into the first and second trenches, the layer of conductive gate material overflowing the surface of the substrate outside the trenches;
etching the conductive gate material such that a top surface of the conductive gate material in the first trench is reduced to a level below the surface of the substrate and the conductive gate material in the second trench is substantially removed;
depositing a second nonconductive layer over the surface of the epitaxial layer and over the gate material in the first trench and into the second trench;
forming a contact mask over the second nonconductive layer, the contact mask having a substrate contact aperture and a gate contact aperture;
etching the second nonconductive layer through the apertures in the contact mask to form a substrate contact aperture and a gate contact aperture in the second nonconductive layer;
removing the contact mask; and
depositing a second conductive layer over the second nonconductive layer, the second conductive layer extending through the substrate contact aperture to make contact with the substrate and through the gate contact aperture to make contact with the conductive gate material. - View Dependent Claims (39)
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40. A trench-gated MIS device comprising:
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a semiconductor substrate generally doped with a dopant of a first conductivity type, a trench being formed in an active region of the substrate;
an insulating layer disposed along a wall of the trench, the trench containing a conductive gate material, a surface of the gate material being at a level below a surface of the substrate;
a nonconductive layer overlying the surface of the substrate;
a conductive layer overlying the nonconductive layer, the conductive layer comprising a current-carrying portion and a gate bus portion, the current-carrying portion and the gate bus portion being electrically isolated from each other, the nonconductive layer having an aperture through which the current-carrying portion of the metal layer is in electrical contact with the substrate in the active region of the device, wherein the thickness of the nonconductive layer underlying the gate bus portion of the conductive layer is substantially the same as the thickness of the nonconductive layer underlying the current-carrying portion of the conductive layer. - View Dependent Claims (41, 42, 43)
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44. A trench-gated MIS device comprising an active device region and a channel stopper region, the device comprising:
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a semiconductor substrate generally doped to a conductivity of first type;
an epitaxial layer overlying the substrate;
a first trench formed in the epitaxial layer in the active region of the device, an insulating layer being disposed along a wall of the trench, the trench containing a conductive gate material, a surface of the conductive gate material being at a level below a surface of the epitaxial layer;
a second trench formed in the epitaxial layer at a location between the active region and the channel stopper region, the second trench being substantially wider than the first trench in at least one location of the second trench;
a nonconductive layer overlying the epitaxial layer in the active region, the nonconductive layer having an aperture in the active region;
a conductive layer overlying the nonconductive layer, the conductive layer comprising a current-carrying portion and a gate bus portion, the current carrying portion being located in the active region, the gate bus portion being located between the active region and the channel stopper region, the current-carrying portion extending through the aperture in the nonconductive layer to make electrical contact with the epitaxial layer, wherein the thickness of the nonconductive layer underlying the gate bus portion of the conductive layer is substantially the same as the thickness of the nonconductive layer underlying the current-carrying portion of the conductive layer. - View Dependent Claims (45)
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46. A trench-gated MIS device having an active area and a gate bus area, the device comprising:
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a semiconductor substrate, a first trench being formed in the substrate in the active area and a second trench being formed in the substrate in the gate bus region, an insulating layer being disposed along a wall of each of the first and second trenches, each of the first and second trenches containing a conductive gate material, the second trench being wider and deeper than the first trench in at least one location of the second trench, the conductive gate material in the second trench being in electrical contact with a gate bus;
at least one pair of protective trenches formed on opposite sides of the second trench, the second trench being deeper than the protective trenches, each of the protective trenches containing conductive gate material, the conductive gate material in the protective trenches being electrically connected to the conductive gate material in the second trench. - View Dependent Claims (47, 48)
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Specification