Method for preparing power MOS tube capable of improving grid oxic horizon homogeneity

Abstract

The invention provides a preparation method for a power MOS pipe capable of increasing evenness of grid oxide layer. The power MOS pipe is prepared on a silicon substrate. In prior art, flow rate of oxygen gas is low, so that thickness of the prepared grid oxide layer is extremely asymmetric and the MOS pipe is easy to leak electricity or to be broken down. The method includes steps: preparing a drain electrode region by re-doping the silicon substrate; preparing a light doping epitaxial layer having same doping style with the drain electrode region; optically etching a grid groove; preparing a grid oxide layer by dry oxygen oxidation, wherein flow rate of the oxygen gas is 15-18 L / min; preparing a grid; preparing a inverse substrate having a reversed doping style with the drain electrode region and a re-doping source electrode region having same doping style with the drain electrode region; finally preparing a grid, source and drain electrode, wherein depth of the grid groove is larger than total thickness of the inverse substrate and the source electrode region. The method of the present invention can greatly increase evenness of the grid oxide layer.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for manufacturing a power MOS transistor capable of improving the uniformity of a gate oxide layer. Background technique [0002] In traditional MOS transistors, the gate, source, and drain are on the same level (that is, the horizontal channel). This structure is very convenient in manufacturing, but it cannot meet the requirements of the large distance because the distance between the source and the drain is too close. The demand for power transistors, in order to meet the needs of high-power transistors, a MOS tube with a vertical channel (that is, a power MOS tube) appeared in the late 1970s, which not only inherited the high input impedance of the horizontal channel MOS tube, but also the low drive current. It also has the advantages of high withstand voltage, large working current, high output power, and fast switching speed. [0003] see figure 1 , sho...

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Problems solved by technology

The film thickness uniformity of the gate oxide layer 12 produced by the above step (d) is less than 75%, so the power MOS transistor 1 produced by the above method has a large leakage current and is extremely easy to be broken down.

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