Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – With means to increase breakdown voltage
Reexamination Certificate
2001-08-31
2004-09-07
Niebling, John F. (Department: 2812)
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
With means to increase breakdown voltage
C438S133000
Reexamination Certificate
active
06787816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the invention relates generally to the manufacturing of semiconductor devices, and more specifically to the manufacturing of thyristors.
2. Discussion of the Related Art
Conventional methods for fabricating silicon carbide thyristors and gate turn-off thyristors include utilizing an all-epitaxial growth technique to fabricate each layer of the device. This epitaxial growth involves doping the crystal during crystal growth. This method has been the only method used for silicon carbide (SiC) thyristor fabrication. For example, the all-epitaxial layer approach has been utilized in both 6H-SiC and 4H-SiC to manufacture thyristor semiconductor devices.
SUMMARY OF THE INVENTION
According to one embodiment of the invention, a method is provided for forming one or more doped layers using ion-implantation in the fabrication of thyristors. These thyristors may be made, for example, from single crystalline silicon carbide. According to one aspect of the invention, one of the required layers is formed by introducing dopants after crystal growth as opposed to conventional methods which involve doping during crystal growth. Specifically, impurities may be introduced by using the technique of ion implantation.
According to one aspect of the invention, a method is provide for forming at least one doped layer of a thyristor comprising providing a semiconductor crystal, the crystal having a crystal structure and being used as at least one doped layer of a thyristor, and introducing impurities in the crystal structure after the crystal structure has been formed. According to one embodiment of the invention, the act of introducing impurities includes introducing impurities using ion implantation. According to one embodiment of the invention, the semiconductor crystal is made of a single crystalline carbide material. According to one embodiment of the invention, the act of introducing impurities using ion implantation includes implanting phosphorus donors using high energy implantation. According to one embodiment of the invention, the act of implanting phosphorus donors is performed at approximately 500 degrees C., and the crystal is annealed at approximately 1200 degrees C. in argon.
According to one embodiment of the invention, the semiconductor crystal is of a first conductivity type and the method includes defining a plurality of layers, the act of defining a plurality of layers comprises defining a first layer of semiconductor material of a first conductivity type, defining a second layer of semiconductor material of a second conductivity type in contact with the first layer, defining a third layer of semiconductor material of the second conductivity type in contact with the second layer, defining a fourth layer of semiconductor material of a first conductivity type in contact with the fourth layer, and defining a fifth layer of semiconductor material of a second conductivity type in contact with the fourth layer.
According to one embodiment of the invention, the method further comprises doping at least one of the plurality of layers by ion implantation. According to one embodiment of the invention, the first layer is made of N+ material. According to one embodiment of the invention, the second layer is made of P material. According to one embodiment of the invention, the third layer is made of P− material. According to one embodiment of the invention, the fourth layer is made of N material. According to one embodiment of the invention, the fifth layer is made of P+material. According to one embodiment of the invention, the fourth layer is formed using ion implantation.
According to another aspect of the invention, a thyristor is provided comprising at least one doped layer, the layer comprising a semiconductor crystal having a crystal structure, the at least one doped layer being formed by introducing impurities in the crystal structure after the crystal structure has been formed. According to one embodiment of the invention, the thyristor is manufactured from a single crystalline silicon carbide. According to one embodiment of the invention, impurities are introduced by ion implantation.
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Chow Tatsing P.
Fedison Jeffrey B.
Lowrie Lando & Anastasi, LLP
Niebling John F.
Rensselaer Polytechnic Institute
Simkovic Viktor
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