Trench IGBT with waved floating P-well electron injection
First Claim
1. A method of manufacturing a trench Insulated Gate Bipolar Transistor (IGBT) die structure, wherein the trench IGBT die structure has a substantially planar upper semiconductor surface, the method comprising:
- forming a floating P type well region that extends into an N−
type drift layer, wherein the floating P type well region has a thinner portion disposed between two of a plurality of thicker portions, wherein the thinner portion of the floating P type well region extends to a depth DP2THIN measured from the substantially planar upper semiconductor surface, wherein the thicker portions of the floating P type well region extend to a depth DP2THICK measured from the substantially planar upper semiconductor surface, wherein DP2THIN is smaller than DP2THICK, wherein the floating P type well region has a closed polygonal outer periphery when the trench IGBT die structure is considered from a top-down perspective, and wherein the floating P type well region at a location along its polygonal outer periphery defines a sidewall of a trench and extends from the substantially planar upper semiconductor surface to the depth DP2THICK, the trench completely surrounding the floating P type well region, wherein the thinner portion of the floating P type well has a polygonal shape when the trench IGBT die structure is considered from the top-down perspective.
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Accused Products
Abstract
A trench IGBT includes a floating P well and a floating N+ well that extends down into the floating P well. A bottom surface of the floating P well has a novel waved contour so that it has thinner portions and thicker portions. When the IGBT is on, electrons flow from an N+ emitter, vertically through a channel along a trench sidewall, and to an N− type drift layer. Additional electrons flow through the channel but then pass under the trench, through the floating P well to the floating N+ well, and laterally through the floating N+ well. NPN transistors are located at thinner portions of the floating P type well. The NPN transistors inject electrons from the floating N+ type well down into the N− drift layer. The extra electron injection reduces VCE(SAT). The waved contour can be made without adding any masking step to an IGBT manufacturing process.
41 Citations
18 Claims
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1. A method of manufacturing a trench Insulated Gate Bipolar Transistor (IGBT) die structure, wherein the trench IGBT die structure has a substantially planar upper semiconductor surface, the method comprising:
forming a floating P type well region that extends into an N−
type drift layer, wherein the floating P type well region has a thinner portion disposed between two of a plurality of thicker portions, wherein the thinner portion of the floating P type well region extends to a depth DP2THIN measured from the substantially planar upper semiconductor surface, wherein the thicker portions of the floating P type well region extend to a depth DP2THICK measured from the substantially planar upper semiconductor surface, wherein DP2THIN is smaller than DP2THICK, wherein the floating P type well region has a closed polygonal outer periphery when the trench IGBT die structure is considered from a top-down perspective, and wherein the floating P type well region at a location along its polygonal outer periphery defines a sidewall of a trench and extends from the substantially planar upper semiconductor surface to the depth DP2THICK, the trench completely surrounding the floating P type well region, wherein the thinner portion of the floating P type well has a polygonal shape when the trench IGBT die structure is considered from the top-down perspective.- View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of manufacturing an Insulated Gate Bipolar Transistor (IGBT) die structure, the method comprising:
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forming a floating P type well region that extends into an N−
type drift layer and that is laterally separated from a P type body region, wherein the N−
type drift layer is disposed over a P type collector layer, wherein the P type body region extends into the N−
type drift layer, wherein the floating P type well region and has at least one thinner portion disposed between two of a plurality of thicker portions, wherein the thinner portion of the floating P type well region extends to a depth DP2THIN measured from a substantially planar upper semiconductor surface, wherein the thicker portions of the floating P type well region extend to a depth DP2THICK measured from the substantially planar upper semiconductor surface, wherein DP2THIN is smaller than DP2THICK, wherein the floating P type well region has a closed polygonal outer periphery when the trench IGBT die structure is considered from a top-down perspective, and wherein the floating P type well region at a location along its polygonal outer periphery defines a sidewall of a trench and extends from the substantially planar upper semiconductor surface to the depth DP2THICK, the trench completely surrounding the floating P type well region;forming a trench gate electrode disposed in the trench, wherein the trench gate electrode is disposed at least in part between the P type body region on one side of the trench and the floating P type well region on an opposite side of the trench; and forming a floating N+ type well region that extends into the floating P type well region from a substantially planar upper semiconductor surface, wherein the floating P type well region is separated from the substantially planar upper semiconductor surface by the floating N+ type well region, and wherein the floating N+ type well region extends laterally over the at least one thinner portion, wherein the trench extends from the substantially planar upper semiconductor surface to a depth DT, wherein the P type body region extends to a depth DP1 measured from the substantially planar upper semiconductor surface, wherein the thicker portions of the floating P type well region extend to a depth DP2THICK measured from the substantially planar upper semiconductor surface, wherein DT is greater than DP1, and wherein DT is greater than DP2THICK, wherein the floating N+ type well region has a polygonal outer periphery when the IGBT die structure is considered from a top-down perspective, and wherein the trench extends around the outer periphery of the floating N+ type well region and the floating P type well region such that it surrounds the floating N+ type well region and the floating P type well region when the IGBT die structure is considered from the top-down perspective. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of manufacturing a trench Insulated Gate Bipolar Transistor (IGBT) die structure, wherein the trench IGBT die structure has a substantially planar upper semiconductor surface, the method comprising:
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forming a floating P type well region that extends into an N−
type drift layer, wherein the floating P type well region has a thinner portion disposed between two of a plurality of thicker portions, wherein the thinner portion of the floating P type well region extends to a depth DP2THIN measured from the substantially planar upper semiconductor surface, wherein the thicker portions of the floating P type well region extend to a depth DP2THICK measured from the substantially planar upper semiconductor surface, wherein DP2THIN is smaller than DP2THICK, wherein the floating P type well region has a closed polygonal outer periphery when the trench IGBT die structure is considered from a top-down perspective, and wherein the floating P type well region at all locations along its polygonal outer periphery defines a sidewall of a trench and extends from the substantially planar upper semiconductor surface to the depth DP2THICK, the trench completely surrounding the floating P type well region, wherein the thinner portion of the floating P type well region is less than half as thick as the thicker portions of the floating P type well region, the method further comprising;forming a floating N+ type well region that extends into the floating P type well region from the substantially planar upper semiconductor surface, wherein the floating P type well region does not reach the substantially planar upper semiconductor surface but rather the floating N+ type well region is disposed between the floating P type well region and the substantially planar upper semiconductor surface. - View Dependent Claims (18)
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Specification