Silicon carbide semiconductor device and manufacturing method thereof
First Claim
1. A silicon carbide semiconductor device comprising:
- a semiconductor substrate made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type;
a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer;
a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer;
a second semiconductor layer of the first conductive type consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench;
a gate insulating film formed at least on a surface of the second semiconductor layer;
a gate electrode layer formed on the gate insulating film in the trench;
a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate; and
a second electrode layer formed on a rear side of the semiconductor substrate,wherein when a reverse bias voltage is impressed on a pn junction between the first electrode layer and the second electrode layer a pn junction between the high-resistance semiconductor layer and the first semiconductor layer undergoes avalanche breakdown before the second semiconductor layer between the high-resistance semiconductor layer and the semiconductor region suffers punch-through.
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Accused Products
Abstract
In a silicon carbide semiconductor device such as a trench gate type power MOSFET, the film thickness and the impurity concentration of a thin film silicon carbide semiconductor layer formed on a trench side face to constitute an accumulation-type channel-forming region and enable the device to operate with a low gate voltage, low on-resistance and low power loss are set so that on impression of a reverse bias voltage a pn junction between a P-type epitaxial layer and an n- -type epitaxial layer undergoes avalanche breakdown before the thin film silicon carbide semiconductor layer undergoes punch-through. By this means it is possible to obtain a target high source-drain withstand voltage.
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Citations
17 Claims
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1. A silicon carbide semiconductor device comprising:
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a semiconductor substrate made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type; a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer; a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer; a second semiconductor layer of the first conductive type consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench; a gate insulating film formed at least on a surface of the second semiconductor layer; a gate electrode layer formed on the gate insulating film in the trench; a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate; and a second electrode layer formed on a rear side of the semiconductor substrate, wherein when a reverse bias voltage is impressed on a pn junction between the first electrode layer and the second electrode layer a pn junction between the high-resistance semiconductor layer and the first semiconductor layer undergoes avalanche breakdown before the second semiconductor layer between the high-resistance semiconductor layer and the semiconductor region suffers punch-through.
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2. A silicon carbide semiconductor device comprising:
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a semiconductor substrate made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type; a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer; a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer; a second semiconductor layer of the first conductive type consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench; a gate insulating film formed at least on a surface of the second semiconductor layer; a gate electrode layer of the second conductive type formed on the gate insulating film in the trench; a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate; and a second electrode layer formed on a rear side of the semiconductor substrate, wherein a film thickness X(μ
m) and an impurity concentration N(cm-3) of the second semiconductor layer with respect to a withstand voltage Y(V) thereof satisfy the relationship Y<
-10000{(X-0.8)+0.3(logN-15)}.
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3. A silicon carbide semiconductor device comprising:
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a semiconductor substrate made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type; a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer; a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer; a second semiconductor layer of the first conductive type consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench; a gate insulating film formed at least on a surface of the second semiconductor layer; a gate electrode layer of the first conductive type formed on the gate insulating film in the trench; a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate; and a second electrode layer formed on a rear side of the semiconductor substrate, wherein a film thickness X(μ
m) and an impurity concentration N(cm-3) of the second semiconductor layer with respect to a withstand voltage Y(V) thereof satisfy the relationship Y<
-10000{(X-0.6)+0.3(logN-15)}.
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4. A silicon carbide semiconductor device comprising:
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a semiconductor substrate consisting of hexagonal system monocrystalline silicon carbide and made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type; a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer; a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer and reaching the high-resistance semiconductor layer and having a side face substantially parallel with a [1100] direction; a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench; a gate insulating film formed at least on a surface of the second semiconductor layer; a gate electrode layer formed on the gate insulating film in the trench; a first electrode layer formed at least on a part of the semiconductor region at the surface of the semiconductor substrate; and a second electrode layer formed on a rear side of the semiconductor substrate. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A silicon carbide semiconductor device comprising:
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a semiconductor substrate consisting of silicon carbide and made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type; a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer; a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer; a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench; a gate oxide film formed at least on a surface of the second semiconductor layer; a gate electrode layer formed on the gate oxide film in the trench; a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate; and a second electrode layer formed on a rear side of the semiconductor substrate, wherein when a reverse bias voltage is impressed on a pn junction between the first electrode layer and the second electrode layer a pn junction between the high-resistance semiconductor layer of the first conductive type and the first semiconductor layer of the second conductive type becomes conductive before a surface of the gate oxide film at a bottom of the trench undergoes avalanche breakdown.
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11. A silicon carbide semiconductor device comprising:
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a semiconductor substrate consisting of silicon carbide and made up of a first low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type, a second low-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type; a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer; a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer and reaching at least the second low-resistance semiconductor layer; a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench; a gate oxide film formed at least on a surface of the second semiconductor layer; a gate electrode layer formed on the gate oxide film in the trench; a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate; and a second electrode layer formed on a rear side of the semiconductor substrate. - View Dependent Claims (12)
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13. A silicon carbide semiconductor device comprising:
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a semiconductor substrate consisting of silicon carbide and made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type; a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer; a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer; a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench; a gate oxide film formed at least on a surface of the second semiconductor layer; a gate electrode layer formed on the gate oxide film in the trench; a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate; and a second electrode layer formed on a rear side of the semiconductor substrate, wherein the high-resistance semiconductor layer is set to a thickness such that, when a reverse bias voltage is impressed on a pn junction between the first electrode layer and the second electrode layer and a pn junction between the high-resistance semiconductor layer and the first semiconductor layer has become conductive, a depletion layer extending from the gate oxide film toward the low-resistance semiconductor layer does not reach the low-resistance semiconductor layer. - View Dependent Claims (14)
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15. A silicon carbide semiconductor device comprising:
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a semiconductor substrate consisting of silicon carbide and made up of a low-resistance semiconductor layer of a first conductive type, a high-resistance semiconductor layer of the first conductive type and a first semiconductor layer of a second conductive type; a semiconductor region of the first conductive type formed in a predetermined region of a surface of the first semiconductor layer; a trench passing from a surface of the semiconductor substrate through the semiconductor region and the first semiconductor layer; a second semiconductor layer consisting of a thin film of silicon carbide formed at least on a surface of the first semiconductor layer at a side face of the trench; a gate oxide film formed at least on a surface of the second semiconductor layer; a gate electrode layer formed on the gate oxide film in the trench; a first electrode layer formed at least on a surface of a part of the semiconductor region at the surface of the semiconductor substrate; a second electrode layer formed on a rear side of the semiconductor substrate; and an embedded semiconductor layer formed in the high-resistance semiconductor layer to be away from the trench and in contact with the first semiconductor layer. - View Dependent Claims (16, 17)
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Specification