JP2012142415A - Magnetic device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of a magnetic device due to damage introduced by a magnetic tunnel junction.SOLUTION: The magnetic device comprises a lower electrode 28 provided with a recess 26 in the upper surface, a magnetic tunnel junction layer 30 formed on the inner surface of the recess in the lower electrode and on the lower electrode on the outside of the recess, and including a tunnel barrier layer and a magnetization fixed layer and a magnetization free layer sandwiching a tunnel barrier layer vertically, and an upper electrode 40 formed on the magnetic tunnel junction layer so as not to reach the side surface of the magnetic tunnel junction layer.

Description

  The present invention relates to a magnetic device, and more particularly to a magnetic device including a magnetic tunnel junction and a manufacturing method thereof.

  For example, an MRAM (Magnetic Random Access Memory) which is a kind of nonvolatile memory includes a magnetic tunnel junction (MTJ) element. The magnetic tunnel junction element includes a structure in which a tunnel barrier layer made of a nonmagnetic material is sandwiched between a magnetization fixed layer and a magnetization free layer made of a ferromagnetic material. The magnetization fixed layer includes an antiferromagnetic layer and a pinned layer, and the magnetization of the pinned layer is not easily reversed by the antiferromagnetic layer. On the other hand, the magnetization of the magnetization free layer is easily reversed. For this reason, for example, the magnetization of the magnetization free layer can be reversed using a spin injection method or the like. When the magnetizations of the magnetization free layer and the magnetization fixed layer are parallel, the resistance value of the magnetic tunnel junction element becomes small. When the magnetizations of the magnetization free layer and the magnetization fixed layer are antiparallel, the resistance value of the magnetic tunnel junction element increases. Thus, for example, data can be stored in a nonvolatile manner according to the magnetization direction of the magnetization free layer.

  For example, a magnetization free layer is formed. An interlayer insulating film is formed which covers the magnetization free layer and is formed with a via hole exposing the magnetization free layer at the bottom surface. A method of forming a tunnel barrier layer and a magnetization fixed layer in a via hole of an interlayer insulating film is known. According to this method, since the magnetization free layer is not exposed when the magnetization fixed layer is processed, damage to the magnetization free layer can be reduced.

  For example, a sidewall insulating film is formed on the side surface of the magnetization free layer. A method of etching a tunnel barrier layer and a magnetization fixed layer using a sidewall insulating film is known. According to this method, adhesion of reactive organisms to the tunnel barrier layer can be prevented.

JP 2008-226919 A JP 2007-214229 A JP 2004-214600 A

  As described above, there is a demand for a structure with less damage introduced into the magnetic tunnel junction element. However, according to the exemplified method, it is difficult to ensure the distance between the end face of the magnetic tunnel junction layer and the region operating as the magnetic tunnel junction element. Therefore, it is difficult to suppress deterioration of the magnetic device due to damage introduced into the magnetic tunnel junction layer, for example, the tunnel barrier layer. An object of the present magnetic device and its manufacturing method is to suppress deterioration of the magnetic device due to damage introduced into a magnetic tunnel junction layer, for example, a tunnel barrier layer.

  For example, a lower electrode having a concave portion on the upper surface, an inner surface of the concave portion of the lower electrode, and the lower electrode outside the concave portion, and a magnetization barrier layer and a magnetization that sandwich the tunnel barrier layer and the tunnel barrier layer vertically A magnetic device comprising: a magnetic tunnel junction layer including a free layer; and an upper electrode formed on the magnetic tunnel junction layer so as not to reach a side surface of the magnetic tunnel junction layer. .

  For example, a step of forming a magnetic tunnel junction layer including a tunnel barrier layer and a magnetization fixed layer and a magnetization free layer sandwiching the tunnel barrier layer vertically on the inner surface of the recess of the lower electrode and on the lower electrode outside the recess And a step of forming an upper electrode on the magnetic tunnel junction layer; a step of polishing an upper surface of the upper electrode so that an upper surface of the magnetic tunnel junction layer is exposed in a region separated from the recess; and And a step of etching the magnetic tunnel junction layer and the lower electrode so that the electrode does not reach the side surface of the magnetic tunnel junction layer.

  According to the present magnetic device and the manufacturing method thereof, it is possible to suppress deterioration of the magnetic device due to damage introduced into the magnetic tunnel junction layer, for example, the tunnel barrier layer.

FIG. 1 is a cross-sectional view of an MRAM cell according to a comparative example. FIG. 2 is a circuit schematic diagram of the MRAM cell. FIG. 3 is a cross-sectional view of a magnetic tunnel junction of a comparative example. FIG. 4 is a diagram showing a resistance value with respect to the area of the magnetic tunnel junction element in the comparative example. FIG. 5 is a schematic cross-sectional view of a sample in which the upper electrode and the lower electrode are short-circuited. FIG. 6 is a diagram showing a resistance value with respect to an area of a sample obtained by over-etching the upper electrode and the magnetic tunnel junction layer. FIG. 7 is a schematic cross-sectional view of a sample when the upper electrode and the magnetic tunnel junction layer are over-etched. FIG. 8 is a cross-sectional view of the MRAM cell according to the first embodiment. FIG. 9 is a cross-sectional view of the magnetic tunnel junction of Example 1. FIG. 10A to FIG. 10D are cross-sectional views (part 1) showing the method for manufacturing the magnetic tunnel junction part of the first embodiment. FIG. 11A to FIG. 11C are cross-sectional views (part 2) illustrating the method for manufacturing the magnetic tunnel junction part of the first embodiment. FIG. 12 is a top view of the cover film in FIG. FIG. 13 is a graph showing resistance values with respect to the area of the magnetic tunnel junction element in Example 1. FIG. 14 is a cross-sectional view of the magnetic tunnel junction element of Example 2.

  First, a comparative example will be described in order to explain damage introduced into the magnetic tunnel junction layer. FIG. 1 is a cross-sectional view of an MRAM cell according to a comparative example. A transistor Tr is formed on the silicon semiconductor substrate 10. The transistor Tr includes a gate electrode 12, a source region 13, and a drain region 14. The gate electrode 12 is formed on the semiconductor substrate 10 (or a diffusion region in the semiconductor substrate) via a gate insulating film. The gate electrode 12 also functions as the word line WL.

  A source region 13 and a drain region having a conductivity type opposite to that of the semiconductor substrate 10 are formed in the semiconductor substrate 10 on both sides of the gate electrode 12. On the semiconductor substrate 10, a plug metal layer 15 and a wiring layer 16 penetrating the interlayer insulating film are laminated. In FIG. 1, the interlayer insulating film is not shown. The source region 13 is connected to the source line SL formed by the wiring layer 16 via the plug metal layer 15 and the wiring layer 16. The drain region 14 is connected to one of the magnetic tunnel junctions 50 via one or more plug metal layers 15 and wiring layers 16. The other of the magnetic tunnel junctions 50 is connected to a bit line BL formed from the wiring layer 16. A logic circuit may be formed on the chip including the MRAM using the same wiring layer 16 or the like.

  FIG. 2 is a circuit schematic diagram of the MRAM cell. The source of the transistor Tr is connected to the source line SL. The gate of the transistor Tr is connected to the word line WL. The drain of the transistor Tr is connected to the bit line BL via the magnetic tunnel junction 50.

  FIG. 3 is a cross-sectional view of a magnetic tunnel junction of a comparative example. For example, a plug metal layer 22 made of copper or the like that penetrates the insulating film 20 such as a silicon oxide film vertically is formed. A lower electrode 28 electrically connected to the plug metal layer 22 is formed on the insulating film 20. A magnetic tunnel junction layer 30 including a magnetization fixed layer 32, a tunnel barrier layer 34, and a magnetization free layer 36 is formed on the lower electrode 28. An upper electrode 40 is formed on the magnetic tunnel junction layer 30.

The formation conditions of the lower electrode 28 are as follows.
Layer structure: Ta film, Ru film, NiFe film, Ta film from below Film forming device: Sputtering Film thickness: Ta film 5 nm, Ru film 50 nm, NiFe film 5 nm, Ta film 10 nm
DC applied power: 1kW
Sputtering gas: Ar
Gas flow rate: 15sccm
Gas pressure: 0.02 Pa or less Substrate heating: None

  After the lower electrode 28 is formed, the lower electrode 28 is etched.

The formation conditions of the magnetization fixed layer 32 are as follows.
Layer structure: PtMn film (strong diamagnetic layer), CoFe film, Ru film, CoFeB film from below Film forming device: Sputtering film thickness: PtMn film 15 nm, CoFe film 2.5 nm, Ru film 0.68 nm, CoFeB film 2nm
DC applied power: 200 W for PtMn film, 400 W for other films
Sputtering gas: Ar
Gas flow rate: 20sccm
Gas pressure: 0.02 Pa or less Substrate heating: None

The conditions for forming the tunnel barrier layer 34 are as follows.
Layer structure: MgO film Film forming device: Sputtering Film thickness: 1.2 nm
DC applied power: 200W
Sputtering gas: Ar
Gas flow rate: 30sccm
Gas pressure: 0.5 Pa or less Substrate heating: None

The conditions for forming the magnetization free layer 36 are as follows.
Layer structure: CoFeB film Film forming device: Sputtering Film thickness: CoFeB film 1.5 nm
DC applied power: 250W
Sputtering gas: Ar
Gas flow rate: 15sccm
Gas pressure: 0.02 Pa or less Substrate heating: None

The formation conditions of the upper electrode 40 are as follows.
Layer structure: Ru film, Ta film from bottom Film forming device: Sputtering Film thickness: Ru film 10 nm, Ta film 30 nm
DC applied power: 200W
Sputtering gas: Ar
Gas flow rate: 15sccm
Gas pressure: 0.02 Pa or less Substrate heating: None

After the upper electrode 40 is formed, the upper electrode 40 and the magnetic tunnel junction layer 30 are etched.
The etching conditions for the upper electrode 40 and the magnetic tunnel junction layer 30 are as follows.
Mask: Photoresist Etching equipment: RIE (Reactive Ion Etching) method Etching gas: Methanol Overetching amount: 120-150%
Substrate heating: None

As the cover film 42, a silicon nitride film is formed so as to cover the lower electrode 28, the magnetic tunnel junction layer 30, and the upper electrode 40.
The conditions for forming the cover film 42 are as follows.
Film formation method: Thermal CVD (Chemical Vapor Deposition) method Film thickness: 30 nm
Gas: NH ₃ (100 sccm), SiH ₄ (250 sccm)
Gas pressure: 0.5Pa
Substrate temperature: 250 ° C

  An insulating film 46 such as a silicon oxide film is formed on the cover film 42, and a plug metal layer 48 penetrating the insulating film 46 vertically is formed. Plug metal layers 22 and 48 correspond to plug metal layer 15 of FIG.

  FIG. 4 is a diagram showing a resistance value with respect to the area of the magnetic tunnel junction element in the comparative example. The resistance value Ra is a resistance value when the magnetic tunnel junction element is in a high resistance state (a state where the magnetization fixed layer and the magnetization free layer are magnetized in opposite directions). Nine types of samples with lengths L = 100 nm, 120 nm, and 140 nm were prepared for the width W = 60 nm, 80 nm, and 100 nm of the magnetic tunnel junction element, respectively. As shown in FIG. 4, in the sample with W = 60 nm, the resistance value Ra is small. This indicates that the upper electrode 40 and the lower electrode 28 are short-circuited.

  FIG. 5 is a schematic cross-sectional view of a sample in which the upper electrode 40 and the lower electrode 28 are short-circuited. As shown in FIG. 5, it is considered that the etching product 52 of the upper electrode 40 and the magnetic tunnel junction layer 30 is attached to the side wall of the magnetic tunnel junction layer 30 with the miniaturization. Etching products can be removed by wet etching, such as ammonia hydrogen peroxide (APM) or nitrate hydrogen peroxide (SPM). However, when the tunnel barrier layer 34 has deliquescence properties such as MgO (magnesium oxide), the wet treatment is difficult.

  Therefore, it is conceivable to over-etch the upper electrode 40 and the magnetic tunnel junction layer 30. When the amount of overetching was increased, short-circuiting in a sample having a width W = 60 nm disappeared at an overetching amount of 200%. When the over-etching amount was less than 200%, the short circuit in the sample having the width W = 60 nm was not improved.

  FIG. 6 is a diagram illustrating a resistance value with respect to an area of a sample in which the upper electrode 40 and the magnetic tunnel junction layer 30 are over-etched. In FIG. 6, the upper electrode 40 and the magnetic tunnel junction layer 30 are over-etched by 200%. Other etching conditions are the same as those of the sample of FIG. As shown in FIG. 6, the resistance value Ra of the sample having the width W = 60 nm was increased. This is considered that the etching product was etched by over-etching. However, the resistance value Ra is not stable.

  FIG. 7 is a schematic cross-sectional view of a sample when the upper electrode 40 and the magnetic tunnel junction layer 30 are over-etched. Although the etching product is removed by overetching, for example, the tunnel barrier layer 34 of the magnetic tunnel junction layer 30 is exposed to the etching gas and is eroded (reference numeral 54). As described above, the tunnel barrier layer 34 is damaged, so that the resistance value Ra becomes high and varies.

  As described above, the comparative example has a problem that it is difficult to suppress deterioration of the magnetic device due to damage introduced into the magnetic tunnel junction layer 30, for example, the tunnel barrier layer 34. The damage introduced into the etching product 52 and the magnetic tunnel junction layer 30 resulting from the etching is a problem that can occur regardless of the material and etching conditions of the upper electrode 40 and the magnetic tunnel junction layer 30 exemplified in the comparative example. is there. Even in the prior art illustrated, it is difficult to solve the above problem because the distance between the tunnel barrier layer 34 and the magnetic tunnel junction element cannot be secured. Hereinafter, examples for solving the above-described problems will be described.

  FIG. 8 is a cross-sectional view of the MRAM cell according to the first embodiment. A magnetic tunnel junction 50 is formed immediately above the plug metal layer 15, and the plug metal layer 15 is formed immediately above the magnetic tunnel junction 50. Other configurations are the same as those in FIGS. 1 and 2 of the comparative example, and a description thereof will be omitted.

  FIG. 9 is a cross-sectional view of the magnetic tunnel junction 50 of the first embodiment. A plug metal layer 22 penetrating the insulating film 20 is formed. A base layer 24 is formed on the insulating film 20. A recess 26 is formed on the plug metal layer 22 of the base layer 24. A lower electrode 28 is formed on the inner surface of the recess 26 formed on the foundation layer 24 and on the foundation layer 24. A recess of the lower electrode 28 is formed in the recess of the base layer 24. A magnetic tunnel junction layer 30 is formed on the inner surface of the recess of the lower electrode 28 and on the lower electrode 28 outside the recess. The magnetic tunnel junction layer 30 includes a tunnel barrier layer 34, a magnetization fixed layer 32 and a magnetization free layer 36 sandwiching the tunnel barrier layer 34 up and down. A recess of the magnetic tunnel junction layer 30 is formed in the recess of the lower electrode 28. In FIG. 9, the magnetization fixed layer 32 is formed below the tunnel barrier layer 34, and the magnetization free layer 36 is formed on the tunnel barrier layer 34. The magnetization free layer 36 may be formed under the tunnel barrier layer 34, and the magnetization fixed layer 32 may be formed over the tunnel barrier layer 34.

  An upper electrode 40 formed so as not to be exposed to the side surface of the magnetic tunnel junction layer 30 is formed on the inner surface of the concave portion of the magnetic tunnel junction layer 30 and on the magnetic tunnel junction layer 30 outside the concave portion. The upper surfaces of the upper electrode 40 and the magnetic tunnel junction layer 30 are planarized. A cover film 42 is formed on the upper surfaces of the upper electrode 40 and the magnetic tunnel junction layer 30. Side surfaces of the lower electrode 28 and the magnetic tunnel junction layer 30 are defined by side surfaces of the cover film 42. For example, the side surface of the cover film 42, the side surface of the magnetic tunnel junction layer 30, and the side surface of the lower electrode form the same plane. In addition, each side surface may be located inside or outside the side surface of the cover film 42 by side etching due to a difference in material. An insulating film 46 that covers the cover film 42 is formed. A plug metal layer 48 that penetrates the insulating film 46 and the cover film 42 and reaches the upper electrode 40 is formed.

FIG. 10A to FIG. 11D are cross-sectional views showing a method for manufacturing the magnetic tunnel junction part of the first embodiment. As shown in FIG. 10A, the insulating film 20 is formed from a silicon oxide film. The insulating film 20 may be an insulating film having a low dielectric constant, for example. A plug metal layer 22 penetrating the insulating film 20 is formed using copper. The plug metal layer 22 may be a metal such as tungsten, for example. A base layer 24 is formed of a silicon oxide film on the insulating film 20 and the plug metal layer 22 using the CVD method. For example, the base film 24 may be an insulating film having a low dielectric constant. As shown in FIG. 10B, a recess 26 that penetrates the base layer 24 vertically is formed. The lower surface of the recess 26 is in contact with the plug metal layer 22. The depth of the recess 26 can be controlled by, for example, the processing time when polishing the surface of the base layer 24 using the CMP method. In the first embodiment, the depth of the recess 26 is selected to be a depth that can ensure coverage with respect to the bottom and side walls of the recess. Generally, it is within 3 times the length of the short side. For example, in FIG. 13 described later, the relationship between the area of the magnetic tunnel junction element and the depth of the recess is as follows.
When the area is 60 nm × 100 to 140 nm, the depth of the recess is 180 nm.
When the area is 80 nm × 100 to 140 nm, the depth of the recess is 240 nm. When the area is 100 nm × 100 to 140 nm, the depth of the recess is 300 nm.

  As shown in FIG. 10C, the lower electrode 28 is formed on the inner surface of the recess 26 of the base layer 24 and on the base layer 24. The formation conditions of the lower electrode 28 are the same as those in FIG.

The following ranges can also be used as the formation conditions of the lower electrode 28.
Layer structure: Ru film, Ta film from below Film thickness: Ru film 5-15 nm, Ta film 10-40 nm
The formation of the lower electrode 28 may use other conditions or other metals.

  A magnetic tunnel junction layer 30 is formed on the inner surface of the lower electrode 28 in the recess 26 and on the lower electrode 28. The magnetic tunnel junction layer 30 includes a tunnel barrier layer 34, a magnetization fixed layer 32 and a magnetization free layer 36 sandwiching the tunnel barrier layer 34. The formation conditions of the magnetization fixed layer 32, the tunnel barrier layer 34, and the magnetization free layer 36 are the same as those in FIG.

The formation condition of the magnetization fixed layer 32 can also be in the following range.
Film thickness: PtMn film 5-20 nm, CoFe film 1.5-3.5 nm, Ru film 0.5-1.0 nm, CoFeB film 1.0-3.0 nm
DC applied power: 200-800W
Gas flow rate: 15-30sccm

The formation conditions of the tunnel barrier layer 34 can also be in the following ranges.
Film thickness: 0.5-1.5nm
Gas flow rate: 30sccm

The formation conditions of the magnetization free layer 36 can also be in the following ranges.
Film thickness: CoFeB film 1.0-2.0 nm
DC applied power: 200-300W
Gas flow rate: 15-30sccm
The formation of the magnetization fixed layer 32 and the magnetization free layer 36 may use other conditions or other ferromagnetic materials. The tunnel barrier layer 34 may be formed under other conditions or other nonmagnetic materials.

  An upper electrode 40 is formed on the inner surface of the magnetic tunnel junction layer 30 in the recess 26 and on the magnetic tunnel junction layer 30. The formation conditions of the upper electrode 40 are the same as those in FIG.

The formation conditions of the upper electrode 40 can also be in the following ranges.
Layer structure: Ta film, Ru film, Ta film from bottom Thickness: Ta film 80 nm, Ru film 10 nm, Ta film 1 nm
DC applied power: 200-1000W
Gas flow rate: 10-30sccm
The formation of the upper electrode 40 may use other conditions or other metals.

  If the surface morphology deteriorates in the process from the lower electrode 28 to the upper electrode 40, the characteristics deteriorate. Therefore, the process from the lower electrode 28 to the upper electrode 40 is preferably performed without being exposed to the atmosphere.

  As shown in FIG. 10D, the upper surface of the upper electrode 40 is polished using a CMP (Chemical Mechanical Polishing) method so that the upper surface of the magnetic tunnel junction layer 30 is exposed in a region separated from the recess 26. For example, the upper electrode 40 is polished until the upper surface of the magnetic tunnel junction layer 30 is exposed. At this time, when viewed from above, the region of the upper surface of the upper electrode 40 includes the region of the recess 26 of the base layer 24, and the magnetic tunnel junction layer 30 is exposed outside the upper electrode 40.

  As shown in FIG. 11A, the cover film 42 is formed using a silicon nitride film so as to cover the lower electrode 28, the magnetic tunnel junction layer 30, and the upper electrode 40. The method for forming the cover film 42 is the same as in FIG.

The formation conditions of the cover film 42 can be in the following ranges.
Film thickness: 10-30nm
_{Gas: NH 3 (50~100sccm), SiH} 4 (250sccm)
Gas pressure: 0.1-1.0 Pa
The cover film 42 may be formed using other conditions or an insulating film other than the silicon nitride film.

  Referring to FIG. 11B, a mask is formed on cover film 42, and cover film 42, magnetic tunnel junction layer 30, and lower electrode 28 are etched using the mask.

The etching conditions for the cover film 42, the magnetic tunnel junction layer 30, and the lower electrode 28 are as follows.
Mask: Photoresist Etching equipment: RIE Etching gas: Methanol Over etching amount: 120-150%
Substrate heating: None Note that a hard mask such as titanium nitride or silicon oxide may be used as the mask.

  At this time. The side surfaces of the magnetic tunnel junction layer 30 and the lower electrode 28 are defined by the side surfaces 44 of the cover film 42. Further, the upper electrode 40 is not exposed on the side surface 44. FIG. 12 is a top view of the cover film in FIG. As shown in FIG. 12, the upper electrode 40 is separated from the side surface 44 of the magnetic tunnel junction layer 30 of the cover film 42.

  As shown in FIG. 11C, an insulating film 46 is formed using a silicon oxide film so as to cover the lower electrode 28, the magnetic tunnel junction layer 30, the upper electrode 40 and the cover film 42. The insulating film 46 may be an insulating film such as a low-k insulating film. A plug metal layer 48 that penetrates the insulating film 46 and the cover film 42 and is electrically connected to the upper electrode 40 is formed. Thus, the magnetic tunnel junction part according to Example 1 is completed.

  FIG. 13 is a graph showing resistance values with respect to the area of the magnetic tunnel junction element in Example 1. White circles indicate Example 1, and black circles indicate a comparative example (same as FIG. 6). In Example 1, the area of the magnetic tunnel junction element indicates the area of the recess 26 of the underlayer 24. Three types of samples having lengths L = 100 nm, 120 nm, and 140 nm were prepared for the width W = 60 nm of the magnetic tunnel junction element. As shown in FIG. 13, in Example 1, the resistance value Ra is stable. This is because, for example, even if an etching product adheres to the side surface 44 from the cover film 42 to the lower electrode 28, the upper electrode 40 is separated from the etching product, so that a leak current is generated via the etching product. This is because it is difficult. Furthermore, damage is introduced into the tunnel barrier layer 34 by over-etching the magnetic tunnel junction layer 30. Alternatively, the tunnel barrier layer 34 is etched by removing the etching product by wet etching. In such a case as well, since the upper electrode 40 is separated from the side surface 44 as shown in FIG. 12, it is possible to suppress the damage introduced into the tunnel barrier layer 34 from affecting the characteristics of the magnetic tunnel junction element. .

  According to the first embodiment, the recess 26 is formed in the base layer 24. A lower electrode 28, a magnetic tunnel junction layer 30, and an upper electrode 40 are formed in the recess 26. The upper electrode 40 is formed so as not to reach the side surface of the magnetic tunnel junction layer 30. Thereby, the distance between the side surface of the magnetic tunnel junction layer 30 and the magnetic tunnel junction element defined by the upper electrode 40 can be secured. Therefore, the instability of the junction resistance due to, for example, damage or loss of the tunnel barrier layer 34 can be eliminated. Thus, the deterioration of the magnetic device due to the damage introduced into the magnetic tunnel junction layer 30 can be suppressed.

  Further, by making the lower surface of the recess 26 of the base layer 24 the upper surface of the plug metal layer 22 that penetrates the insulating film 20 vertically, the chip area can be reduced.

  In the first embodiment, the base layer 24 is an insulating film, but the base layer 24 may be a metal, for example. For example, the plug metal layer 22 may be used as a base film, and a recess may be formed on the upper surface of the plug metal layer 22.

  Further, the upper surfaces of the upper electrode 40 and the magnetic tunnel junction layer 30 are flattened so that the upper electrode 40 does not reach the side surface of the magnetic tunnel junction layer 30 as shown in FIGS. be able to.

  Further, as shown in FIG. 9, a cover film 42 is formed on the upper electrode 40 and the magnetic tunnel junction layer 30. The upper electrode 40 is not exposed between the side surface of the cover film 42 and the side surface of the magnetic tunnel junction layer 30. Thereby, the distance between the side surface of the magnetic tunnel junction layer 30 and the magnetic tunnel junction element can be secured.

  Further, as shown in FIG. 9, the side surfaces of the lower electrode 28 and the magnetic tunnel junction layer 30 are defined by the side surfaces 44 of the cover film 42. Thereby, the upper electrode 40 can be prevented from being exposed from the magnetic tunnel junction layer 30.

  Example 2 is an example in which the underlying electrode 24 is not provided and the lower electrode 28 is provided with the recess 26. FIG. 14 is a cross-sectional view of the magnetic tunnel junction element of Example 2. As shown in FIG. 14, the lower electrode 28 includes a recess 26 on the upper surface. The magnetic tunnel junction layer 30 is formed on the inner surface of the magnetic tunnel junction layer 30 formed in the recess of the lower electrode 28 and on the lower electrode 28 outside the recess 26. The upper electrode 40 is formed on the inner surface of the magnetic tunnel junction layer 30 formed in the recess of the lower electrode 28 and on the magnetic tunnel junction layer 30 outside the recess 26. The upper electrode 40 is formed so as not to reach the side surface of the magnetic tunnel junction layer 30. For example, the upper surface of the upper electrode 40 is provided inside the side surface of the magnetic tunnel junction layer 30.

  Even in the structure of the second embodiment, the distance between the magnetic tunnel junction layer 30 and the upper electrode 40 can be secured. For this reason, the instability of the junction resistance due to the damage of the magnetic tunnel junction layer 30, for example, the damage or deficiency of the tunnel barrier layer 34 can be eliminated.

  Note that the recess 26 formed in the lower electrode 28 may have a forward taper structure in which the upper portion is larger than the lower portion as in the second embodiment. This facilitates embedding the upper electrode 40 in the recess of the magnetic tunnel junction layer 30.

  In Example 1 and Example 2, the tunnel barrier layer 34 may be made of a material other than magnesium oxide. For example, aluminum oxide may be used. However, when a deliquescent material such as magnesium oxide is used, it is particularly difficult to remove the etching product of FIG. Therefore, it is preferable to apply Example 1 or 2 when the tunnel barrier layer 34 is made of magnesium oxide.

  Although the example of MRAM was demonstrated as an example of a magnetic device, you may use for devices other than MRAM.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

Regarding the embodiment including Examples 1 and 2, the following additional notes are disclosed.
APPENDIX 1: A lower electrode having a concave portion on the upper surface, an inner surface of the concave portion of the lower electrode and the lower electrode outside the concave portion, and a magnetization fixed layer sandwiching the tunnel barrier layer and the tunnel barrier layer vertically A magnetic device comprising: a magnetic tunnel junction layer including a magnetization free layer; and an upper electrode formed on the magnetic tunnel junction layer so as not to reach a side surface of the magnetic tunnel junction layer.
Appendix 2: A cover film is formed on the upper electrode and the magnetic tunnel junction layer, and the upper electrode is not exposed between the side surface of the cover film and the side surface of the magnetic tunnel junction layer. The magnetic device according to appendix 1, wherein:
(Supplementary note 3) The magnetic device according to Supplementary note 1 or 2, wherein side surfaces of the lower electrode and the magnetic tunnel junction layer are defined by a side surface of the cover film.
(Supplementary Note 4) A lower layer is formed on the inner surface of the recess of the base layer and on the base layer, and the recess of the lower electrode is formed in the recess of the base layer. The magnetic device according to any one of appendices 1 to 3, wherein the magnetic device is formed.
Appendix 5: An insulating film and a plug metal layer vertically penetrating the insulating film, the underlayer being formed on the insulating film, and a lower surface of the recess of the underlayer being an upper surface of the plug metal layer The magnetic device as set forth in Appendix 4, wherein:
Supplementary Note 6: The magnetic device according to any one of Supplementary notes 1 to 5, wherein upper surfaces of the upper electrode and the magnetic tunnel junction layer are flat.
APPENDIX 7: The magnetic device according to any one of appendices 1 to 6, wherein the tunnel barrier layer includes magnesium oxide.
APPENDIX 8: The magnetic device according to any one of appendices 1 to 7, wherein the magnetic device is an MRAM.
Supplementary Note 9: A magnetic tunnel junction layer including a tunnel barrier layer, a magnetization fixed layer and a magnetization free layer sandwiching the tunnel barrier layer vertically is formed on the inner surface of the recess of the lower electrode and on the lower electrode outside the recess. Polishing the upper surface of the upper electrode so that the upper surface of the magnetic tunnel junction layer is exposed in a region spaced from the recess; and And a step of etching the magnetic tunnel junction layer and the lower electrode so that the upper electrode does not reach the side surface of the magnetic tunnel junction layer.

20 Insulating Film 22 Plug Metal Layer 24 Underlayer 26 Recess 28 Lower Electrode 30 Magnetic Tunnel Junction Layer 32 Magnetization Fixed Layer 34 Tunnel Barrier Layer 34
36 Magnetization free layer 40 Upper electrode 42 Cover film

Claims (6)

A lower electrode having a recess on the upper surface;
A magnetic tunnel junction layer formed on the inner surface of the concave portion of the lower electrode and on the lower electrode outside the concave portion, and including a tunnel barrier layer and a magnetization fixed layer and a magnetization free layer sandwiching the tunnel barrier layer vertically;
An upper electrode formed on the magnetic tunnel junction layer so as not to reach a side surface of the magnetic tunnel junction layer;
A magnetic device comprising: Comprising a cover film formed on the upper electrode and the magnetic tunnel junction layer;
2. The magnetic device according to claim 1, wherein the upper electrode is not exposed between a side surface of the cover film and a side surface of the magnetic tunnel junction layer.   The magnetic device according to claim 1, wherein side surfaces of the lower electrode and the magnetic tunnel junction layer are defined by side surfaces of the cover film. Comprising a base layer with a recess,
The said lower electrode is formed in the inner surface of the recessed part of the said base layer, and the said base layer, The recessed part of the said lower electrode is formed in the recessed part of the said base layer, The Claim 1 to 3 characterized by the above-mentioned. The magnetic device according to any one of claims. Comprising an insulating film and a plug metal layer vertically penetrating the insulating film;
5. The magnetic device according to claim 1, wherein the underlayer is formed on the insulating film, and a lower surface of the concave portion of the underlayer is an upper surface of the plug metal layer. Forming a lower electrode having a recess on the upper surface;
Forming a magnetic tunnel junction layer including a tunnel barrier layer and a magnetization fixed layer and a magnetization free layer sandwiching the tunnel barrier layer above and below the inner surface of the recess of the lower electrode and on the lower electrode outside the recess;
Forming an upper electrode on the magnetic tunnel junction layer;
Polishing the upper surface of the upper electrode so that the upper surface of the magnetic tunnel junction layer is exposed in a region spaced from the recess;
Etching the magnetic tunnel junction layer and the lower electrode so that the upper electrode does not reach the side surface of the magnetic tunnel junction layer;
A method for manufacturing a magnetic device, comprising:

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