Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – With means to increase breakdown voltage
Patent
1998-05-22
2000-02-01
Loke, Steven H.
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
With means to increase breakdown voltage
257147, 257170, 257623, H01L 2974, H01L 31111, H01L 2906
Patent
active
060206039
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high voltage semiconductor device such as a gate turn-off thyristor or the like and a method of fabricating the same, and more particularly, it relates to withstand voltage increase and capacity enlargement thereof.
2. Discussion of the Background
It is known that avalanche breakdown takes place at a voltage lower than a withstand voltage of original real ability of a P-N junction in a high voltage semiconductor device such as a high voltage diode or a high voltage gate turn-off thyristor and the high voltage semiconductor device cannot be fabricated unless a surface field of a main P-N junction is weakened.
Therefore, a technique called bevel formation for weakening the electric field by inclining an exposed part of the P-N junction is known.
However, there has been such a problem that, although a device thus inclined, i.e., bevelled, can attain withstand voltage increase as compared with a device not subjected to the bevelling, chipping readily takes place in an edge part formed on a boundary part between its outer peripheral part and the said bevelled part in fabrication, field concentration results from a strain field generated in the chipping part, withstand voltage increase is inhibited, and stable provision of a semiconductor device of a high withstand voltage is difficult as a result.
Particularly as to chipping, there has been such a problem that its influence is large in a semiconductor device of a large capacity in which the diameter of a semiconductor element is large, i.e., the outer peripheral length of the semiconductor element is long, and stable provision of a semiconductor device of a high withstand voltage and a large capacity is difficult as a result.
SUMMARY OF THE INVENTION
The present invention has been proposed in consideration of the aforementioned general circumstances, and aims at attaining stable provision of a semiconductor device of a high withstand voltage and a large capacity having a main P-N junction.
The device of the present invention is structured by forming a chamfer or a boundary surface of a prescribed radius of curvature on a boundary part between at least one of bevelled surfaces and an outer peripheral surface, whereby occurrence of chipping which has generally occurred on the boundary part between the said bevelled surfaces and the said outer peripheral part can be remarkably reduced as compared with the prior art, occurrence of field concentration which has generally occurred by a strain field of the chipping part is prevented, not only withstand voltage increase can be attained as a result but its effect is remarkably satisfactory in such a device of a large capacity that the diameter of a semiconductor element is large, i.e., the outer peripheral length of the semiconductor element is long, and there is an effect of enabling stable provision of a semiconductor device of a large capacity as a result.
Further, the device of the present invention is so structured that the depth of bevelling from an end surface of a second conductivity type low-resistance layer is deeper than a position of an end of that depletion layer from the end surface of the said second conductivity type low-resistance layer which is formed when a voltage is applied between a first conductivity type low-resistance layer and the said second conductivity type low-resistance layer, whereby the depletion layer is bent in the vicinity of the said bevelled surface as it will be shown by a broken line, and as a result, there is such an effect that the field intensity on the surface is reduced as compared with a device not having the said bevelled surface and withstand voltage increase and capacity enlargement of the semiconductor device can be attained.
Further, the device of the present invention is so structured that the field intensity on a bevelled surface formed from the second conductivity type low-resistance layer toward a first conductivity type high-resistance layer is smaller than the field intens
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Nakasima Nobuhisa
Sakamoto Tokumitsu
Tanaka Yasuo
Tokunoh Futoshi
Loke Steven H.
Mitsubishi Denki & Kabushiki Kaisha
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