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Integrated High Voltage Bipolar Device with Reduced Surface Inversion and Parasitic Paths

IP.com Disclosure Number: IPCOM000087139D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Bartholomew, RF: AUTHOR [+4]

Abstract

A well-controlled surface implant in a high voltage bipolar device prevents inversion up to 40 volts in resulting parasitic field-effect transistor (FET) devices without serious reduction in collector-base breakdown voltages.

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Integrated High Voltage Bipolar Device with Reduced Surface Inversion and Parasitic Paths

A well-controlled surface implant in a high voltage bipolar device prevents inversion up to 40 volts in resulting parasitic field-effect transistor (FET) devices without serious reduction in collector-base breakdown voltages.

In Fig. 1, an arsenic implant 10 is formed across the surface of an epitaxial layer 12 united to a substrate 14. The layer 10 prevents inversion between high- doped regions 16 and 16' due to an overlying, negatively biased metal conductor 18 disposed on an oxide 20. The arsenic layer is formed after removal of all oxide. The arsenic is implanted at a dosage of 1.0x10/12/ atoms/cm/2/ at 150 KeV. The depth in the substrate at the end of the process is on the order of 0.7 microns and is introduced late in the bipolar process to minimize subsequent heat treatments. The control of concentration depth is necessary so that curvature-limited junction breakdown voltages can be kept high while maintaining a high threshold voltage for the unwanted FET devices between regions 16 and 16' and the like.

Fig. 2 shows that for dosages exceeding 1.0x10/12/ atoms/cm/2/ the threshold voltage becomes higher than that of the breakdown voltage for the collector-base of junctions formed in the layer 12. The concentration is kept low so as not to invert the normal P regions at the surface of the layer 12 nor to decrease the breakdown voltage excessively. The layer 10 may also b...