TWI878782B - Magnetic memory device - Google Patents

Abstract

The embodiment of the present invention provides a magnetic memory device with excellent characteristics or reliability. The magnetic memory device of the embodiment has a plurality of memory cells, and the plurality of memory cells respectively include: a magnetoresistance effect element; and a switch element, which is arranged on the lower layer side of the magnetoresistance effect element and connected in series with respect to the magnetoresistance effect element; and the switch element includes: a lower electrode; an upper electrode; and a switch material layer, which is arranged between the lower electrode and the upper electrode; and the upper electrode includes: a first part, which is formed of a first material; and a second part, which is arranged on the lower layer side of the first part and is formed of a second material different from the first material.

Description

Magnetic memory device

An embodiment of the present invention relates to a magnetic memory device.

A magnetic memory device is proposed in which a memory cell including a magnetoresistance effect element and a selector (switching element) is integrated on a semiconductor substrate.

The problem to be solved by the invention is to provide a magnetic memory device with excellent characteristics or reliability.

The magnetic memory device of the implementation form has a plurality of memory cells, which respectively include: a magnetoresistance effect element; and a switch element, which is arranged on the lower layer side of the above-mentioned magnetoresistance effect element and is connected in series with the above-mentioned magnetoresistance effect element; and the above-mentioned switch element includes: a lower electrode; an upper electrode; and a switching material layer, which is arranged between the above-mentioned lower electrode and the above-mentioned upper electrode; and the above-mentioned upper electrode includes: a first part, which is formed by a first material; and a second part, which is arranged on the lower layer side of the above-mentioned first part and is formed by a second material different from the above-mentioned first material.

Hereinafter, the implementation will be described with reference to the drawings.

FIG. 1 is a perspective view schematically showing the structure of a magnetic memory device of an embodiment.

The magnetic memory device shown in FIG1 includes: a plurality of first wiring lines 10, each extending in the X direction; a plurality of second wiring lines 20, each extending in the Y direction; and a plurality of memory cells 30, each connected between the plurality of first wiring lines 10 and the plurality of second wiring lines 20. In addition, the X direction, the Y direction, and the Z direction are mutually intersecting directions. More specifically, the X direction, the Y direction, and the Z direction are mutually orthogonal directions.

Each memory cell 30 includes a magnetoresistive element 40 and a selector (switch element) 50 disposed on the lower layer side of the magnetoresistive element 40 and connected in series with the magnetoresistive element 40.

The first wiring 10 is provided on the lower layer side of the selector 50 and is electrically connected to the selector 50. The second wiring 20 is provided on the upper layer side of the magnetoresistive effect element 40 and is electrically connected to the magnetoresistive effect element 40. One of the first wiring 10 and the second wiring 20 corresponds to a word line, and the other of the first wiring 10 and the second wiring 20 corresponds to a bit line.

FIG. 2 is a cross-sectional view schematically showing the detailed structure of the memory cell 30.

As shown in FIG. 2 , the memory cell 30 includes a magnetoresistive element 40 , a selector (switch element) 50 , a hard mask layer 60 , and a protective insulating layer 70 .

FIG. 3 is a cross-sectional view schematically showing the basic structure of the magnetoresistive effect element 40 .

The magnetoresistive element 40 is an MTJ (Magnetic Tunnel Junction) element, including a storage layer (first magnetic layer) 41 , a reference layer (second magnetic layer) 42 , a tunnel barrier layer (nonmagnetic layer) 43 , a bottom electrode 44 , and a top electrode 45 .

The memory layer 41 is a ferromagnetic layer with a variable magnetization direction. The variable magnetization direction means that the magnetization direction changes relative to a specific write current. The reference layer 42 is a ferromagnetic layer with a fixed magnetization direction. The fixed magnetization direction means that the magnetization direction does not change relative to a specific write current. The tunnel barrier layer 43 is an insulating layer disposed between the memory layer 41 and the reference layer 42.

When the magnetization direction of the memory layer 41 is parallel to the magnetization direction of the reference layer 42, the magnetoresistive element 40 is in a low resistance state with a relatively low resistance. When the magnetization direction of the memory layer 41 is antiparallel to the magnetization direction of the reference layer 42, the magnetoresistive element 40 is in a high resistance state with a relatively high resistance. Therefore, the magnetoresistive element 40 can store binary data according to the resistance state.

The magnetoresistive element 40 is a STT (Spin Transfer Torque) type magnetoresistive element having perpendicular magnetization, that is, the magnetization direction of the memory layer 41 is perpendicular to the film surface, and the magnetization direction of the reference layer 42 is perpendicular to the film surface.

In addition, in the example of FIG. 3 , although a bottomless magnetoresistive element in which the memory layer 41 is located on the lower layer side of the reference layer 42 is used, a topless magnetoresistive element in which the memory layer 41 is located on the upper layer side of the reference layer 42 may also be used.

As shown in FIG2 , the selector 50 includes a lower electrode 51, an upper electrode 52, and a selector material layer (switch material layer) 53 disposed between the lower electrode 51 and the upper electrode 52. The lower electrode 51 is electrically connected to the first wiring 10 shown in FIG1 , and the upper electrode 52 is electrically connected to the magnetoresistive element 40.

The selector 50 is a two-terminal switch element, and when the voltage applied between the two terminals (between the lower electrode 51 and the upper electrode 52) becomes greater than the threshold voltage, the selector 50 changes from the disconnected state to the conductive state. In other words, when the voltage applied between the two terminals becomes greater than the threshold voltage, the selector 50 changes from the electrically non-conductive state to the electrically conductive state.

Therefore, when a voltage is applied to the memory cell 30 from the first wiring 10 and the second wiring 20 and the voltage applied to the selector 50 becomes equal to or higher than the threshold voltage, a current flows to the memory cell 30 and data can be written or read from the magnetoresistive element 40 .

The upper electrode 52 of the selector 50 includes: a first portion 52a, which is formed of a first material; a second portion 52b, which is disposed on the lower layer side of the first portion 52a and is formed of a second material different from the first material; and a third portion 52c, which is disposed on the lower layer side of the second portion 52b and is formed of a third material different from the second material. That is, the second portion 52b is disposed between the first portion 52a and the third portion 52c. In addition, the upper electrode 52 of the selector 50 may be used in common with the lower electrode 44 of the magnetoresistive element.

The etching rate of the second portion 52b for IBE (Ion Beam Etching) is lower than the etching rate of the first portion 52a for IBE. Specifically, in the IBE used when forming the pattern of the magnetoresistive effect element 40, the etching rate for the second portion 52b is lower than the etching rate for the first portion 52a. Since IBE is physical etching, the hardness of the second material used for the second portion 52b is usually higher than the hardness of the first material used for the first portion 52a.

As the first material, a material containing silicon (Si) or a material containing halogen (Hf) is used. That is, the first portion 52a is formed of a Si layer (polycrystalline Si layer) or a Hf layer.

The second material includes a material containing niobium (Hf) and boron (B), a material containing tungsten (W), a material containing carbon (C), or a material containing titanium (Ti) and nitrogen (N). That is, the second portion 52b is formed of a HfB layer, a W layer, a C layer, or a TiN layer.

The third material is a material containing titanium (Ti) and nitrogen (N), a material containing carbon (C), or a material containing aluminum (Al). That is, the third portion 52c is formed of a TiN layer, a C layer, or an Al layer.

A material containing silicon (Si), oxygen (O), and arsenic (As) is used for the selector material layer 53. Specifically, silicon oxide ( _SiO2 ) containing As or the like is used for the selector material layer 53.

A TiN layer containing titanium (Ti) and nitrogen (N) is used as the lower electrode 51 of the selector 50.

The hard mask layer 60 is disposed on the magnetoresistive element 40 and functions as an etching mask when the magnetoresistive element 40 is formed by IBE. The hard mask layer 60 is electrically connected to the second wiring 20 shown in FIG.

The protective insulating layer 70 is formed of, for example, silicon nitride containing silicon (Si) and nitrogen (N). The protective insulating layer 70 is provided along the side surface of the magnetoresistive effect element 40, the side surface of the first portion 52a of the upper electrode 52 of the selector 50, and the side surface of the hard mask layer 60, and covers the side surface of the magnetoresistive effect element 40, the side surface of the first portion 52a of the upper electrode 52 of the selector 50, and the side surface of the hard mask layer 60.

Since the protective insulating layer 70 is disposed on the upper layer side of the second portion 52b of the upper electrode 52 of the selector 50, the side surfaces of the second portion 52b and the third portion 52c of the upper electrode 52 are not covered.

Furthermore, the position of the lower end of the protective insulating layer 70 coincides with the position of the upper surface of the second portion 52b of the upper electrode 52. Therefore, the positions of the lower ends of the plurality of protective insulating layers 70 included in the plurality of memory cells 30 in the height direction coincide with each other.

Next, a method for manufacturing the magnetic memory device of this embodiment will be described with reference to FIGS. 4 to 7 and the cross-sectional view shown in FIG. 2 .

First, as shown in FIG. 4 , a laminate film is formed on a lower region (not shown) including a semiconductor substrate (not shown) and the like. Specifically, a lower electrode layer 51p, a selector material layer 53p, an upper electrode layer 52p, and a magnetoresistive element layer 40p are formed. The upper electrode layer 52p includes a first partial layer 52ap, a second partial layer 52bp, and a third partial layer 52cp. Next, a pattern of a hard mask layer 60 is formed on the magnetoresistive element layer 40p.

Next, as shown in FIG5 , the hard mask layer 60 is used as a mask to etch the magnetoresistive element layer 40p and the first portion layer 52ap by IBE. Since the magnetoresistive element contains magnetic elements such as iron (Fe) or cobalt (Co), it is difficult to perform accurate etching by conventional etching methods. Therefore, physical etching, i.e., IBE, is used. When performing IBE, the substrate is rotated while an argon (Ar) ion beam is irradiated from an inclined direction. As a result, the side surfaces of the magnetoresistive element 40 and the first portion 52a are inclined in a cone shape.

As described above, the etching rate of the second portion 52b for IBE is lower than the etching rate of the first portion 52a for IBE. Therefore, the second portion layer 52bp functions as an etching stopper for IBE and can selectively etch the magnetoresistive element layer 40p and the first portion layer 52ap.

Next, as shown in FIG. 6 , a silicon nitride layer is deposited on the surface of the structure obtained in the step of FIG. 5 as a protective insulating layer 70 .

Next, as shown in Fig. 7, the protective insulating layer 70, the second portion layer 52bp and the third portion layer 52cp are etched by RIE (Reactive Ion Etching), thereby obtaining the pattern of the second portion 52b and the pattern of the third portion 52c.

2, the selector material layer 53p and the lower electrode layer 51p are etched by RIE, thereby obtaining the pattern of the selector material layer 53 and the pattern of the lower electrode 51.

In the steps of FIG7 and FIG2 , RIE is performed from a vertical direction. Therefore, the side surface of the second portion 52 b, the side surface of the third portion 52 c, the side surface of the selector material layer 53, and the side surface of the lower electrode 51 become vertical.

By the above-mentioned manufacturing method, a memory cell 30 as shown in FIG. 2 is formed.

As described above, in this embodiment, since the upper electrode 52 of the selector 50 includes the second portion 52b having a lower etching rate for IBE, an excellent magnetic memory device can be obtained as described below.

If the upper electrode 52 does not include the second portion 52b, when the magnetoresistive element 40 is patterned by IBE, the selector material layer 53 may be etched in addition to the upper electrode 52. Therefore, the selector material layer 53 may be damaged by IBE, and the characteristics or reliability of the selector 50 may be reduced.

In this embodiment, the etching rate of the second portion 52b for IBE is lower than the etching rate of the first portion 52a for IBE. Therefore, when the pattern of the magnetoresistive effect element 40 is formed by IBE, the second portion 52b functions as an etching stopper for IBE. As a result, the selector material layer 53 can be prevented from being etched due to IBE. Therefore, the damage of IBE to the selector material layer 53 can be suppressed, and a magnetic memory device with excellent characteristics and reliability can be obtained.

In general, there is a case where the space width between adjacent memory cells 30 is uneven due to unevenness in the lithography process. If there is unevenness in the space width, unevenness will also occur when forming the pattern of the memory cell 30. For example, the etching depth becomes smaller in a portion with a smaller space width than in a portion with a larger space width. Therefore, in a portion with a smaller space width, a problem such as the lower electrode 51 of the selector 50 cannot be separated between adjacent memory cells 30 occurs.

Although the IBE etching amount may be increased to enlarge the space width in order to reliably separate the lower electrode 51 of the selector 50, if the etching amount is increased, IBE damage to the selector material layer 53 may occur.

In this embodiment, the second portion 52b of the upper electrode 52 of the selector 50 is used as an etching stopper, and the pattern of the magnetoresistive element 40 and the pattern of the first portion 52a of the upper electrode 52 of the selector 50 are formed by IBE. By using the second portion 52b as an etching stopper, the time for performing IBE can be extended without causing IBE damage to the selector material layer 53. Therefore, the space width between adjacent memory cells 30 can be increased. Therefore, the lower electrode 51 of the selector 50 can be separated reliably, and a magnetic memory device with excellent characteristics and reliability can be obtained.

Next, a modified example of the embodiment will be described with reference to the cross-sectional view shown in FIG. 8 .

As shown in Fig. 8, in this variation, the upper electrode 52 of the selector 50 is formed by the first portion 52a and the second portion 52b provided on the lower layer side of the first portion 52a, and the third portion 52c is not provided on the lower layer side of the second portion 52b. The other basic structures are the same as those of the above-mentioned embodiment.

In this variation, similarly to the above-mentioned embodiment, when the pattern of the magnetoresistive element 40 is formed by IBE, the second portion 52b functions as an etching stopper. Therefore, the same effect as the above-mentioned embodiment can be obtained, and an excellent magnetic memory device can be obtained.

Although several embodiments of the present invention have been described, these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. These embodiments or their variations are included in the scope or subject matter of the invention, and are included in the invention described in the scope of the patent application and its equivalents. [References to related applications]

This application claims priority from Japanese Patent Application No. 2022-038150 (filing date: March 11, 2022) and U.S. Patent Application No. 17/943160 (filing date: September 12, 2022). This application incorporates all the contents of the basic application by reference.

10: 1st wiring 20: 2nd wiring 30: Memory cell 40: Magnetoresistive element 40p: Magnetoresistive element layer 41: Memory layer (1st magnetic layer) 42: Reference layer (2nd magnetic layer) 43: Tunnel barrier layer (non-magnetic layer) 44: Lower electrode 45: Upper electrode 50: Selector (switch element) 51: Lower electrode 51p: Lower electrode layer 52: Upper electrode 52a: Part 1 52ap: Part 1 layer 52b: Part 2 52bp: Part 2 layer 52c: Part 3 52cp: Part 3 layer 52p: Upper electrode layer 53: Selector material layer (switch material layer) 53p: Selector material layer 60: Hard cover layer 70: Protective insulation layer

FIG. 1 is a perspective view schematically showing the structure of a magnetic memory device of an embodiment. FIG. 2 is a cross-sectional view schematically showing the structure of a memory cell of a magnetic memory device of an embodiment. FIG. 3 is a cross-sectional view schematically showing the basic structure of a magnetoresistive element of a magnetic memory device of an embodiment. FIG. 4, FIG. 5, FIG. 6 and FIG. 7 are cross-sectional views schematically showing the manufacturing method of a magnetic memory device of an embodiment. FIG. 8 is a cross-sectional view schematically showing the structure of a variation of a memory cell of a magnetic memory device of an embodiment.

30: Memory cells

40: Magnetoresistance effect element

50: Selector (switch element)

51: Lower electrode

52: Upper electrode

52a: Part 1

52b: Part 2

52c: Part 3

53: Selector material layer (switch material layer)

60: Hard cover layer

70: Protective insulation layer

Claims (11)

A magnetic memory device having a plurality of memory cells, the plurality of memory cells respectively comprising: a magnetoresistance effect element; and a switch element, which is arranged on the lower layer side of the magnetoresistance effect element and connected in series with respect to the magnetoresistance effect element; and the switch element comprises: a lower electrode; an upper electrode; and a switch material layer, which is arranged between the lower electrode and the upper electrode; and the upper electrode comprises: a first part, which is formed of a first material; and a second part, which is arranged on the lower layer side of the first part and is formed of a second material different from the first material, and the etching rate of the second part to IBE (Ion Beam Etching) is lower than the etching rate of the first part to IBE. A magnetic memory device as claimed in claim 1, wherein the hardness of the second material is higher than the hardness of the first material. A magnetic memory device as claimed in claim 1, wherein the second material is a material containing tungsten (W), a material containing carbon (C), or a material containing titanium (Ti) and nitrogen (N). A magnetic memory device as claimed in claim 1, wherein the first material is a material containing silicon (Si) or a material containing halogen (Hf). A magnetic memory device as claimed in claim 1, wherein the upper electrode further comprises a third part disposed on the lower layer side of the second part and formed of a third material different from the second material. A magnetic memory device as claimed in claim 1, wherein each of the plurality of memory cells further comprises a protective insulating layer covering the side surface of the magnetoresistive element and the side surface of the first part. A magnetic memory device as claimed in claim 6, wherein the protective insulating layer does not cover the side surface of the second part. A magnetic memory device as claimed in claim 6, wherein the height direction positions of the lower ends of the protective insulating layers included in the plurality of memory cells are consistent. A magnetic memory device as claimed in claim 1, wherein the side surface of the first part is inclined and the side surface of the second part is vertical. A magnetic memory device as claimed in claim 1, wherein the magnetoresistance effect element comprises: a first magnetic layer; a second magnetic layer; and a non-magnetic layer disposed between the first magnetic layer and the second magnetic layer. The magnetic memory device of claim 1 further comprises: a first wiring, which is arranged on the lower layer side of the switch element, extends in the first direction, and is electrically connected to the switch element; and a second wiring, which is arranged on the upper layer side of the magnetoresistive effect element, extends in the second direction intersecting the first direction, and is electrically connected to the magnetoresistive effect element.