MAGNETIC MEMORY DEVICE

According to one embodiment, a magnetic memory device includes an electrode, and a magnetoresistance effect element provided on the electrode. The electrode includes a first electrode portion and a second electrode portion provided between the magnetoresistance effect element and the first electrode portion and containing a metal element selected from molybdenum (Mo) and ruthenium (Ru).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-148039, filed Sep. 16, 2022, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic memory device.

BACKGROUND

A magnetic memory device has been proposed in which magnetoresistance effect elements are integrated on a semiconductor substrate.

DETAILED DESCRIPTION

In general, according to one embodiment, a magnetic memory device includes: an electrode; and a magnetoresistance effect element provided on the electrode, wherein the electrode includes a first electrode portion and a second electrode portion provided between the magnetoresistance effect element and the first electrode portion and containing a metal element selected from molybdenum (Mo) and ruthenium (Ru).

FIG.1is a cross-sectional view schematically showing a configuration of a magnetic memory device according to the embodiment.

The magnetic memory device of this embodiment has a configuration in which a plurality of stacked structures100are provided on a lower structure (not shown) that includes a semiconductor substrate.

The stacked structures100each include a magnetoresistance effect element10, an electrode20, a hard mask30, and a sidewall insulating layer40.

FIG.2shows a schematic cross-sectional view of the magnetoresistance effect element10.

The magnetoresistance effect element10is a magnetic tunnel junction (MTJ) device and is provided on the electrode20. The magnetoresistance effect element10has a stacked structure including a storage layer (first magnetic layer)11, a reference layer (second magnetic layer)12and a tunnel barrier layer (nonmagnetic layer)13.

The storage layer11is a ferromagnetic layer having a variable magnetization direction and includes, for example, a CoFeB layer containing cobalt (Co), iron (Fe) and boron (B). The term “variable magnetization direction” means that the magnetization direction changes for a given write current.

The reference layer12is a ferromagnetic layer having a fixed magnetization direction and includes, for example, a CoFeB layer containing cobalt (Co), iron (Fe) and boron (B). The term “fixed magnetization direction” means that the magnetization direction does not change for a given write current.

The tunnel barrier layer13is an insulating layer provided between the storage layer11and the reference layer12, and includes, for example, an MgO layer containing magnesium (Mg) and oxygen (O).

When the magnetization direction of the storage layer11is parallel to the magnetization direction of the reference layer12, the magnetoresistance effect element10exhibits a low resistance state. When the magnetization direction of the storage layer11is antiparallel to the magnetization direction of the reference layer12, the magnetoresistance effect element10exhibits a high resistance state. Therefore, the magnetoresistance effect element10can store binary data according to its resistance state (low resistance state and high resistance state).

The magnetoresistance effect element10is constituted by a spin transfer torque (STT) type magnetoresistance effect element and has perpendicular magnetization. That is, the magnetization direction of the storage layer11is perpendicular to its main surface, and the magnetization direction of the reference layer12is perpendicular to its main surface.

Note thatFIG.2shows a bottom-free type magnetoresistance effect element in which the storage layer11is located on a lower layer side of the reference layer12, but a top-free type magnetoresistance effect element in which the storage layer11is located on an upper layer side of the reference layer12may be used.

Let us now return to the explanation ofFIG.1. The electrode20functions as a bottom electrode of the magnetoresistance effect element10and includes a first electrode portion21and a second electrode portion22.

The first electrode portion21contains carbon (C). Specifically, the first electrode portion21contains carbon as a major component and is formed from a carbon layer that contains substantially no elements other than carbon.

The second electrode portion22is provided between the magnetoresistance effect element10and the first electrode portion21and contains a metal element selected from molybdenum (Mo) and ruthenium (Ru). Specifically, the second electrode portion22is formed from a molybdenum layer or ruthenium layer that contains a metal element selected from molybdenum and ruthenium as a main component and substantially contains no elements other than molybdenum and ruthenium. The upper surface of the second electrode portion22is in contact with the lower surface of the magnetoresistance effect element10, and the lower surface of the second electrode portion22is in contact with the upper surface of the first electrode portion21.

The hard mask30is provided on the magnetoresistance effect element10and is formed of a conductive material. The hard mask30functions as a mask used to form the pattern of the magnetoresistance effect element10and the pattern of the electrode20. The hard mask30functions as the top electrode of the magnetoresistance effect element10as well.

The sidewall insulating layer40is provided along a side surface of the magnetoresistance effect element10, a side surface of the second electrode portion22, and an upper portion of a side surface of the first electrode portion21. The sidewall insulating layer40has the function of protecting the magnetoresistance effect element10.

Next, with reference toFIGS.3,4and1, a method of manufacturing the magnetic memory device according to the embodiment will be described.

First, as shown inFIG.3, an electrode layer20sincluding a first electrode layer21sand a second electrode layer22slocated on the first electrode layer21sis formed on a lower structure (not shown) including a semiconductor substrate. The first electrode layer21sis formed from a carbon layer and the second electrode layer22sis formed from a molybdenum layer or a ruthenium layer. Subsequently, a magnetoresistance effect element layer10sincluding a storage layer, a reference layer, and a tunnel barrier layer is formed on an electrode layer20s. Further, a hard mask30is formed on the magnetoresistance effect element layer10s.

Next, as shown inFIG.4, the magnetoresistance effect element layer10sand the second electrode layer22sare etched using the hard mask30as a mask. More specifically, the etching is performed by ion beam etching (IBE). In this etching process, the upper portion of the first electrode layer21sis etched as well. Here, a portion of the hard mask30is etched as well. With this etching process, the pattern of the magnetoresistance effect element10and the pattern of the second electrode portion22can be obtained.

Next, as shown inFIG.1, the sidewall insulating layer40is formed on a side surface of the pattern obtained in the etching process ofFIG.4. Subsequently, the first electrode layer21sis etched using the hard mask30as a mask to form the first electrode portion21. More specifically, the etching is performed by reactive ion etching (RIE). At this time, the magnetoresistance effect element10is protected by the sidewall insulating layer40.

In this manner, the magnetic memory device shown inFIG.1is formed.

As described above, in this embodiment, the electrode20includes a second electrode portion22provided between the magnetoresistance effect element10and the first electrode portion21, and the second electrode portion22contains a metal element selected from molybdenum and ruthenium. With this configuration, according to this embodiment, proper patterning as described below can be carried out.

In the case where the second electrode portion22is not provided, the material component of the magnetoresistance effect element layer10sgenerated in the IBE process ofFIG.4may undesirably remain on the surface of the first electrode layer21sby knocking. That is, the material component of the magnetoresistance effect element layer10smay undesirably remain on the surface of the first electrode layer21sas residue. Therefore, when etching the first electrode layer21sin the RIE process after the process shown inFIG.4, the etching of the first electrode layer21smay be inhibited by the residue remaining on the surface of the first electrode layer21s. As a result, a portion of the first electrode layer21smay remain between adjacent stacked structures100, and the first electrode layer21smay not be sufficiently separated between adjacent stacked structures100. In particular, as the magnetic memory device is miniaturized and the distance between adjacent stacked structures100becomes smaller, there rises an increasing possibility that the first electrode layer21scannot be sufficiently separated.

In this embodiment, a second electrode layer22scontaining a metal element selected from molybdenum and ruthenium is provided between the magnetoresistance effect element layer10sand the first electrode layer21s. Molybdenum and ruthenium are less likely to remain on the surface of the first electrode layer21sdue to knocking. Further, in the IBE process shown inFIG.4, since the second electrode layer22sis etched after the magnetoresistance effect element layer10sis etched, the material components of the magnetoresistance effect element layer10sgenerated by IBE are removed when the second electrode layer22is etched. Therefore, there is no substantial residue remaining on the surface of the first electrode layer21sthat would inhibit RIE. In this manner, the first electrode layer21scan be etched reliably in the RIE process, and the first electrode layer21scan be reliably separated between adjacent stacked structures100.

FIG.5is a perspective view schematically showing a brief structure of a magnetic memory device to which the stacked structure100described above is applied. Note here that X, Y, and Z directions shown inFIG.5are intersect each other, and more specifically, the X, Y, and Z directions are orthogonal to each other.

The magnetic memory device shown inFIG.5includes a plurality of first wiring lines110each extending in the X direction, a plurality of second wiring lines120each extending in the Y direction, and a plurality of memory cells130each provided between each respective one of the plurality of first wiring lines110and each respective one of the plurality of second wiring lines120. The first wiring lines110correspond to word lines, whereas the second wiring lines120correspond to bit lines, or vice versa.

The memory cells130each includes a magnetoresistance effect element140and a selector (switching element)150connected in series to the magnetoresistance effect element140, and the magnetoresistance effect element140and the selector150are provided between the respective first wiring line110and the respective second wiring line120. The memory cell130includes the stacked structure100described above, and inFIG.5, the magnetoresistance effect element140substantially corresponds to the stacked structure100described above.

The selector150is a 2-terminal type switching device including a bottom electrode, a top electrode, and a selector material layer provided between the bottom electrode and the top electrode, and has characteristics in which it changes from an off state to an on state when the voltage applied between the two terminals reaches or exceeds a threshold voltage.

That is, by applying a voltage between a first wiring line110and a second wiring line120to set the respective selector150to the on state, a current flows to the magnetoresistance effect element140, thus making it possible to write to or read from the magnetoresistance effect element140.

Note that as a material for the selector150, for example, a material having such properties (snap-back properties) that the resistance value drops sharply at a predetermined voltage and the applied voltage drops sharply therewith and the current increases can as well be applied.

Further, the electrode20shown inFIG.1may as well be used as the bottom electrode of the magnetoresistance effect element140and the top electrode of the selector150.

By applying the above-described stacked structure100to a magnetic memory device as shown inFIG.5, an excellent magnetic memory device can be obtained.

Note that inFIG.5, the magnetoresistance effect element140is provided on the upper layer side of the selector, but the magnetoresistance effect element140may as well be provided on the lower layer side of the selector.