Fabrication Process of Superjunction Devices

Abstract

The invention discloses a production process of a super-junction device. Trenches are etched and filled to form a super-junction. Each trench is etched section by section, so that etching difficulty is greatly reduced, and the sidewall of the trench is more vertical. During a filling process, a depth-to-width ratio of each trench is small, so that filling difficulty is greatly reduced and defects are greatly lessened; meanwhile, by the use of the sectional process, charge balance can be easily maintained for all positions, and breakdown voltage is increased. In addition, by the use of sectional process, the quantity of electric charge can be locally changed, and more device feature optimization methods are provided for designers.

Description

technical field [0001] The invention relates to the field of semiconductors, in particular to a preparation process of a super junction device. Background technique [0002] Super-Junction (SJ, super junction) transistor is a unique N / P interactive structure, so that only thinner EPI (epitaxial layer) and higher EPI doping are required under the same breakdown voltage, thus greatly reducing the The specific on-resistance of the device-Rsp, and the figure of merit (FOM, quality factor) value. [0003] At present, the Super-Junction is usually formed by multiple epitaxy + implantation + annealing. However, this method causes the concentration of local P-pillars to be too high, which easily leads to premature breakdown, such as figure 1 As shown, P columns are formed in the composite epitaxial layer 2 formed by multi-layer epitaxial layers prepared on the substrate 1. At the same time, because the concentration and area of ​​the effective N columns are reduced due to the need...

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Problems solved by technology

[0005] And these put forward very high requirements on the manufacturing process, which is generally difficult to achieve

In particular, it is necessary to further reduce the cell size to achieve a smaller Rsp, and the general manufacturing process can only be prohibitive

[0006] Due to the deep depth of the groove prepared, it is necessary to use DRIE (Deep Reactive Ion Etching, deep reactive ion etching) equipment for etching. At present, the cost of DRIE equipment is very expensive, which undoubtedly increases the production cost and preparation difficulty; at the same time Due to the relatively large depth-width ratio of the prepared trench, during the process of filling the trench with the P-type epitaxial layer 3, the P-type epitaxial layer 3 may form a blockage at the opening, causing a cavity 4 to be formed at the bottom of the trench, such as Figure 2f As shown, this will have an adverse effect on device performance; furthermore, because it is difficult to make the trench side wall absolutely straight, the traditional trench-SJ often has a very narrow bottom, which causes the N / P charge imbalance to cause breakdown voltage drop

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