Pn Junction Chip Deep Groove Corrosion Research

Currently the high-power AC/DC converters of wide applications are allsilicon-semiconductor rectifiers. In terms of the rectifier variety, from single-phase0.5Arectifiers to three-phase200A rectifiers, their inner rectification chips are all ofdeep-diffusion deep PN junction with glass-passivated protection.This thesis conducts an analysis and research on the erosion mechanism during theerosion process of glass-passivated protection wafer manufacturing in view of thespecification requirement of1200V glass-passivated protection wafer and concludes themain reasons why the form of channel after erosion will have influence on the reversevoltage of chip and also affect the glass coverage thickness and so on. The channel formafter erosion is not only closely related to the clinging of photo resist and the designdifference of glass mask, but also to the erosion liquid temperature, flow speed andvibration and so on.We develop the “beak form” deep channel with positive/negative angleslow-variation absorption structure to alleviate the surface electric filed. But thiscompatible structure leads to a channel form with over erosion, which is called “beak”.Usually it is sharp at this point and glass layer will be thick when conducting glasspassivation and cannot offer a proper protection, which can easily cause leakage. Thechip strength becomes lower and vulnerable to the stress. Through the analysis of theforming of this point, this thesis conducts a research on rule how different erosionformulations and temperatures influence the forming of channel and explores a formthat allows positive/negative angle slow-variation absorption structure but has no sharppoint that may influence the electrical characteristics and reliability, eliminates theerosion formulation and process, and fundamentally solve the problem of P+channelingand get a deep-channel erosion for the chip of deep PN-junction that meets therequirement of high voltage, low scrap rate and also allowing the positive/negativeangle slow-variation absorption structure. This could not only ensure the quality ofsemiconductor packing but also reduce the production cost, which improves the productcompetitiveness of LRC.