Passivation of flush junction on semiconductor surface - using layer of polycrystalline silicon contg. oxygen, then silicon nitride, silica, and finally glass

摘要

A pn-junction which is level with the surface of a substrate is covered by a layer (3) of polycrystalline Si doped with oxygen(sipox), and then with Si3N4(4) followed by SiO2(5) and finally glass (6). The sipox (3) pref. contains 20-30 mole% oxygen per ccm, and is 500-3000 angstroms thick. Layer (4) is pref. 100-400 angstroms thick, whereas layer (5) is 100-200 angstroms. The coatings are pref. obtd. by placing the substrate in a reactor heated to 800-920 deg.C. and fed with a gas forming SiCl2 during three stages. In the first stage a small amt. of N2O is added, whereas NH3 is used in the second stage, and a larger amt. of N2O is added in the third stage. The SiCl2 is pref. obtd. from either SiH2Cl2, or a mixt. of SiH4 and Cl2. A high breakdown voltage is achieved for semiconductors operating at high voltages and high temps., e.g. power transistors, thyristors, or triacs.