Electronic Design

Transistor's Planar Structure Reduces Reverse Leakage

Low reverse leakage current, high-voltage operation, high power dissipation—these are some of the outstanding characteristics claimed for the type 2N1613 transistor. The features result from the silicon unit's construction: both the collector-to-base and base-to-emitter junctions are embedded in the top surface of the planar structure (see the drawing). In the mesa structure, the collector-to-base junction is on the side of the device.

Made by Fairchild Semiconductor Corp. (545 Whisman Road, Mountain View, Calif.), some of the planar-structure transistors' advantages are:

  • A typical ICB0 of 0.0005 µamp at 60 v. This compares with 0.02 µamp at 60 v for a typical mesa unit.
  • A useful beta over a range of collector currents from 100 µamp to 0.5 amp.
  • The typical gain-bandwidth product is 100 mc.
  • Physical ruggedness: The planar structure makes the device "more resistant to thermal and mechanical shock and vibration than previous types."

Why have both diffused junctions in the top surface of the device? Because, the manufacturer says, the top surface of the silicon chip has a better "finish" to it than the sides. This leads to less surface sensitivity and better characteristics.

The type 2N1613 transistor is available in production quantities. (Electronic Design, March 30, 1960, p. 76)

This is the first depiction of the planar process that I've seen in any of the old issues of this magazine. Later in the year, Fairchild Semiconductor introduced its first integrated circuits based on this process, and the door to the future was opened wide. We'll cover these planar integrated circuits again in November.

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