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
• 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 an enhanced avalanche ruggedness Fast Recovery Diode comprising:

• selecting a semiconductor material of a first dopant type;
• patterning and defining a field spreading region and a central conduction region of the diode in a top surface of the semiconductor material;
• patterning and defining within the central conduction region trenches of a predetermined depth in the semiconductor material;
• introducing and diffusing a first dopant of a second type opposite in polarity to the dopant of the first type into the top surface in said defined field spreading region and central conduction region, said diffusion creating in the central conduction region a PN junction having acute curvature at the corners and edges of said trenches;
• and
• completing the device by forming metal electrodes on the frontside and backside of the semiconductor to conduct current through the device.

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

• selecting a semiconductor material of a first dopant type;
• patterning and defining a central conduction region bounded by a periphery in a top surface of the semiconductor material;
• etching to reduce the semiconductor material thickness by about 15 to 20% within said defined central conduction region in relationship to its periphery;
• patterning and defining a field spreading region surrounding the central conduction region of the device;
• introducing and diffusing a first dopant of a second type opposite in polarity to the dopant of the first type into the top surface in said defined field spreading region and central conduction region;
• and
• completing the device by forming metal electrodes on the frontside and backside of the semiconductor to conduct current through the device.