High write selectivity and low power magnetic random access memory and method for fabricating the same

Abstract

A low-power magnetic random access memory (MRAM) with high write selectivity is provided. Write word lines and pillar write word lines covered with a magnetic material are disposed in an zigzag relation, solving the magnetic interference problem generated by cells adjacent to the pillar write word line in the magnetic RAM with the pillar write word line form. According to the disclosed structure, each of the cells has a smaller bit size and a lower write current. This effectively reduces the power consumption of the MRAM.

Description

[0001] This application is a Divisional of co-pending application Ser. No. 10 / 846,663 filed on May 14, 2004, and for which priority is claimed under 35 U.S.C. §120; and this application claims priority of Application No. 92136353 filed in Taiwan on Dec. 19, 2003 under 35 U.S.C. §119; the entire contents of all are hereby incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of Invention [0003] The invention relates to a magnetic random access memory (MRAM) and, in particular, to an MRAM with high write selectivity and low power consumption. [0004] 2. Related Art [0005] Magnetic random access memory (MRAM) is nonvolatile memory. Using its magnetic resistance property to record information, it has the advantages of non-volatility, high densities, high access speeds, and anti-radiation. [0006] The basic operation principles of the MRAM are the same as storing data on a hard disk drive (HDD). Each bit of data is determined by its magnetization orientation to be either 0 ...

AI Technical Summary

Benefits of technology

[0011] In view of the foregoing, a primary objective of the invention is to provide a magnetic random access memory (MRAM) with high write selectivity and low power consumption. The invention reduces the write current required by the MRAM, thereby reducing the power consumption during the write period thereof.

[0012] The disclosed structure can eliminate the magnetic interference problem of the write word lines on adjacent MTJ's. This increases the write selectivity of the MRAM.

[0013] To achieve the above-mentioned objective, the disclosed MRAM has a plurality of MTJ cells, a plurality of bit lines, a plurality of middle metal pillars, and a plurality of PWWL's. Each MTJ cell is comprised of a magnetic tunnel junction cell and a lower electrode. Changing the magnetization orientation of the magnetic tunnel junction cell determines the memory state. Each bit line provides the read and write current channels for the corresponding MTJ cell. Each middle metal pillar connects the MTJ cell and the bit line. Each write word line is comprised of an upper layer write word line, a lower layer write word line and a pair of PWWL's, providing the write current channel for the MTJ cell. This increases the induced magnetic field at the MTJ cell. The PWWL's of the adjacent MTJ cells are disposed in an interleaving fashion (zigzag pattern as shown in the FIG. 2). Aside from the part of the PWWL facing the surrounding of the magnetic tunnel junction cell, the rest is covered by a sidewall keeper. The sidewall keeper covering the PWWL's of the disclosed MRAM can reduce the write current required by the MRAM.

[0014] The invention has to add a photo mask process after the PWWL process. Furthermore, the disclosed sidewall keeper structure confines the magnetic flux on the MTJ so that adjacent MTJ's are not affected by the magnetic field produced by the PWWL's. The write selectivity of the MRAM is thus greatly increased.

Problems solved by technology

As memory devices are becoming smaller, the MRAM starts to encounter the electron migration problem because the write-in electrical current needed to change data approaches the current density limit that can be carried by a metal wire.

Nonetheless, this structure has a problem.

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