Design and fabrication of rugged FRED

A fabrication process for making an enhanced avalanche ruggedness Fast Recovery Diode, the process comprising:

• selecting a semiconductor material of a first dopant type;
• patterning and introducing a first dopant of a second type opposite in polarity to the first dopant type into the top surface of the semiconductor material at a peripheral region of the device;
• diffusing said first dopant to create field spreading structures for blocking reverse voltage;
• introducing a second dopant of the first type into a central portion of the semiconductor material top surface;
• diffusing said second dopant to create a region with enhanced doping concentration of the first type within the semiconductor material in the central portion of the device;
• introducing and diffusing a third dopant of the second type to a predetermined depth within said enhanced doping region to form a main PN junction and effect a lower avalanche breakdown in the central portion in relationship to a periphery of the main PN junction;
• and
• forming metal electrodes on the top surface and a backside of the semiconductor material to conduct current through the diode;
• further comprising a first deep life-time control dopant profile having a gradient that is higher in doping concentration toward the backside of the semiconductor;
• and
• a second shallow life-time control profile having a gradient that is heavier toward the top surface forming a shallow gradient band of decreasing concentration near the PN junction.

A fabrication process for making an enhanced avalanche ruggedness Fast Recovery Diode, comprising:

• selecting a semiconductor material of a first dopant type;
• introducing a preliminary dopant of a first type prior to a step of patterning and introducing a first dopant of a second type to prevent current flow along a surface of the semiconductor material between an active area and an edge of the device across the field-spreading structures;
• diffusing said first dopant to create field spreading structures for blocking reverse voltage;
• introducing a second dopant of the first type into a central portion of the semiconductor material top surface;
• diffusing said second dopant to create a region with enhanced doping concentration of the first type within the semiconductor material in the central portion of the device;
• introducing and diffusing a third dopant of the second type to a predetermined depth within said enhanced doping region to form a main PN junction and effect a lower avalanche breakdown in the central portion in relationship to a periphery of the main PN junction;
• and
• completing the device by forming metal electrodes on the top surface and a backside of the semiconductor material to conduct current through the diode.

A fabrication process for making a Fast Recovery Diode, the process comprising:

• selecting a semiconductor material of a first dopant type;
• patterning and introducing dopant of a second type opposite in polarity to the first dopant type into the top surface of the semiconductor material;
• diffusing said dopant of a second type to create field spreading structures for blocking reverse voltage and to form a main PN junction in the central active portion of the device;
• forming metal electrodes on the top surface and a backside of the semiconductor material to conduct current through the diode;
• further comprising a blanket implant of a dopant of the first dopant type into the semiconductor surface to counter the effect of counter-doping and compensation by a life-time control dopant.

A fabrication process for making a Fast Recovery Diode, comprising:

• selecting a semiconductor material of a first dopant type;
• introducing a preliminary dopant of the first type prior to a step of patterning and introducing a first dopant of a second type opposite in polarity to the first dopant type to prevent current flow along a surface of the semiconductor material between an active area and an edge of the device across the field-spreading structures;
• diffusing said first dopant to create field spreading structures for blocking reverse voltage;
• patterning and introducing dopant of a second type opposite in polarity to the first dopant type into the top surface of the semiconductor material;
• diffusing said dopant of a second type to create field spreading structures for blocking reverse voltage and to form a main PN junction in the central active portion of the device;
• and
• completing the device by forming metal electrodes on the top surface and a backside of the semiconductor material to conduct current through the diode.