A kind of fabrication method of superjunction structure

Abstract

The present invention relates to a super junction structure and a manufacturing method thereof, the method comprising: providing a substrate of a first conductivity type, forming a first epitaxial layer of the first conductivity type on the substrate; Forming a trench mask layer on the upper surface of the layer; performing first etching on the first epitaxial layer to form at least one trench; forming a polysilicon layer on the side walls of the trench and the side walls of the trench mask layer, and performing second etching of the trench, stopping the second etching when removing the polysilicon layer; filling the trench with a plurality of second epitaxial layers of the second conductivity type, the plurality of second epitaxial layers The two epitaxial layers are stacked sequentially from the bottom to the top of the trench, and the concentrations of the multiple second epitaxial layers decrease sequentially from the bottom to the top of the trench. The super junction structure formed by the above method has high reliability and uniform charge distribution.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a super junction structure and a manufacturing method thereof. Background technique [0002] In a semiconductor device, power loss can be reduced by reducing the on-resistance of the device. Since the breakdown voltage is inversely proportional to the on-resistance, when the on-resistance decreases, it will have an adverse effect on the breakdown voltage. To solve this problem, superjunction structures have been introduced, which include alternating P-type and N-type regions located below the active region of the device. The alternating P-type regions and N-type regions in the superjunction structure are ideally in a state of charge balance, so that these regions are mutually depleted under reverse voltage conditions, and can better withstand breakdown. [0003] Existing super-junction structures usually use trench etching technology. In terms of current etching technolo...

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Problems solved by technology

[0003] Existing super-junction structures usually use trench etching technology. In terms of current etching technology, since trenches are usually formed by one-time etching, for trenches exceeding 30um, the etching time usually takes more than 2 hours , Excessive etching time will make it difficult to remove the polymer remaining on the side wall of the trench, the steepness of the entire trench side wall is poor, there are more dangling bonds, more defects after epitaxy, device reliability failure, etc.

If step-by-step etching is used, since the polymer after the first etching remains on the trench sidewall during the second etching, the lateral undercut widths of the two etchings are different, resulting in very poor steepness

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