Process for making a high-voltage bipolar transistor.

摘要

1. A method of manufacturing a semiconductor device comprising at least one high-voltage bipolar transistor, according to which method there are successively deposited on a substrate (1) a first epitaxial layer (2) of a first conductivity type and a second epitaxial layer (3) of the second conductivity type opposite to the first type, a contact zone (10) is formed on the second epitaxial layer (3) and lateral isolating separation walls (6) of the first conductivity type are formed, these separation walls penetrating into the first epitaxial layer after having traversed the second epitaxial layer (3), the said lateral separation walls (6) surrounding an island formed in the second epitaxial layer (3), the thickness and the doping concentration of the second layer (3) being such that, when an inverse voltage is applied to the pn-junction between on the one hand the second epitaxial layer (3) and on the other hand the first epitaxial layer (2) and the isolating separation walls (6), the depleted zone produced by this voltage extends throughout the thickness of the second epitaxial layer (3) for a value of the said voltage lower than the breakdown voltage, the distance between the lateral isolating separation walls (6) and the contact zone (10) being larger than the maximum lateral extent of the depleted zone from the isolating separation walls (6) in the second epitaxial layer (3), characterized in that a third epitaxial layer (7) of the first conductivity type is deposited on the second epitaxial layer (3), in that the isolating separation walls (6) are manufactured in at least two stages, a first portion (6a) being formed before the deposition of the third epitaxial layer (7) and extending through at least the whole thickness of the second layer (3), amd a second portion (6b) being formed opposite to the first portion (6a) after the deposition of the third layer (7) and throughout the thickness of the latter, and in that a part of the third epitaxial layer (7) situated within the contour of the isolating separation walls (6) is electrically insulated from the said separation walls (6) by the formation of the contact zone (10) which surrounds the said part of the third epitaxial layer and is separated from the said lateral isolating separation walls (6) by a distance at least equal to the thickness of the depleted zone formed around the isolating junction of the said separation walls (6), and penetrates into the islands formed in the second epitaxial layer (3) of the same conductivity type after having traversed the third epitaxial layer (7).