Patent ID: 9224943
Filing Date: 2015-12-29
Classification: H01L

Abstract:
1. A method of forming an annular storage unit of a magneto-resistive memory, which is applied to a magneto-resistive random access memory, wherein said method comprises the following steps: Step 1: a thin-film layer of magnetic channel junction is deposited on a wafer substrate; then a silicon oxide layer and a silicon nitride layer are formed on the thin-film layer of said magnetic channel junction; Step 2: a photo-resist pattern is defined on the silicon nitride layer by photoetching process; the top view of said photo-resist pattern is a circular groove, and the diameter of said circular groove ranges from 40 nm to 200 nm; Step 3: said silicon nitride layer is etched, and said etching process stops at said silicon oxide layer below said silicon nitride layer, then remaining photo-resist is removed to form a circular silicon nitride trench; Step 4: a poly-silicon thin film with good step coverage property is covered on the surface of the wafer to form a poly-silicon layer, and a plasma etching-back is performed on the poly-silicon layer; the etching process stops at said silicon nitride layer, and an annular poly-silicon structure is formed on the sidewalls of said silicon nitride trench, in the step of forming the poly-silicon layer, the thickness of the poly-silicon thin film covered on the bottom side, on the sidewall and on the upside of the circular silicon nitride trench is substantially identical; Step 5: the remaining silicon nitride layer is removed by etching, and the etching process stops at said silicon oxide layer below said silicon nitride layer; only said annular poly-silicon structure remains on the surface of the wafer after etching; Step 6: said poly-silicon structure formed in Step 5 is used as a hard mask while said underlying thin-film layer of a magnetic channel junction is etched with dry plasma etching to form the annular structure of the magnetic channel junction.