CN111816674A

CN111816674A - Magnetic random access memory and forming method thereof

Info

Publication number: CN111816674A
Application number: CN201910284671.8A
Authority: CN
Inventors: 平尔萱; 朱一明
Original assignee: Changxin Memory Technologies Inc
Current assignee: Changxin Memory Technologies Inc
Priority date: 2019-04-10
Filing date: 2019-04-10
Publication date: 2020-10-23

Abstract

A magnetic random access memory and a method of forming the same, the magnetic random access memory comprising: the surface of the substrate is provided with a conductive contact pad; the magnetic storage layer is positioned on the surface of the substrate and comprises at least two sub-storage layers stacked on the surface of the substrate, a plurality of magnetic storage units vertically penetrating through the sub-storage layers and connected with the conductive contact pads are arranged in the magnetic storage layers, the magnetic storage units comprise magnetic tunnel junctions, and each sub-storage layer comprises at least one magnetic tunnel junction. The magnetic random access memory has high performance.

Description

Magnetic random access memory and forming method thereof

Technical Field

The invention relates to the technical field of memories, in particular to a magnetic random access memory and a forming method thereof.

Background

A magnetic random access memory (mram) is based on the integration of silicon-based complementary oxide semiconductor (CMOS) and Magnetic Tunnel Junction (MTJ) technologies, and is a non-volatile memory that possesses the high-speed read and write capabilities of static random access memories, as well as the high integration of dynamic random access memories.

Please refer to fig. 1, which is a schematic structural diagram of a conventional magnetic random access memory.

The magnetic random access memory includes an access transistor 110 and a magnetic tunnel junction 120, the magnetic tunnel junction 120 including a pinned layer 121, a tunneling layer 122, and a free layer 123. The drain 111 of the access transistor 110 is connected to the pinned layer 121 of the magnetic tunnel junction 120, and the free layer 123 of the magnetic tunnel junction 120 is connected to a bit line 130; the source 112 of the access transistor 110 is connected to a source line 140.

During normal operation of the magnetic random access memory, the magnetization direction of the free layer 123 can change while the magnetization direction of the pinned layer 121 remains unchanged. The resistance of the magnetic random access memory is related to the relative magnetization directions of the free layer 123 and the fixed layer 121. When the magnetization direction of the free layer 123 changes relative to the magnetization direction of the fixed layer 121, the resistance value of the magnetic random access memory changes accordingly, corresponding to different stored information.

In the existing process technology node, the density of the magnetic tunnel junction in the unit area of the magnetic random access memory is high, and the magnetic tunnel junction is easily damaged in the process of forming the magnetic tunnel junction by etching, so that the yield of chips is influenced.

Disclosure of Invention

The invention aims to solve the technical problem of avoiding damage to the magnetic tunnel junction in the process of etching to form the magnetic tunnel structure.

In order to solve the above problems, the present invention provides a magnetic random access memory, comprising a substrate, a first conductive layer and a second conductive layer, wherein the substrate has a conductive contact pad formed on the surface thereof; the magnetic storage layer is positioned on the surface of the substrate and comprises at least two sub-storage layers stacked on the surface of the substrate, a plurality of magnetic storage units vertically penetrating through the sub-storage layers and connected with the conductive contact pads are arranged in the magnetic storage layers, the magnetic storage units comprise magnetic tunnel junctions, and each sub-storage layer comprises at least one magnetic tunnel junction.

Optionally, the magnetic tunnel junctions of the plurality of magnetic storage cells are randomly arranged in each sub-storage layer.

Optionally, the magnetic tunnel junctions in each sub-storage layer are arranged in a random form or an array form.

Optionally, the magnetic tunnel junctions of adjacent magnetic storage cells are respectively located in different sub storage layers.

Optionally, in the same sub-storage layer, the spacing between at least part of adjacent magnetic tunnel junctions is greater than the minimum spacing between magnetic random access memory cells.

Optionally, in the magnetic storage layer, a distance between adjacent magnetic storage units is a; the minimum spacing between adjacent magnetic tunnel junctions in the same sub-storage layer is

n is the number of sub-memory layers in the magnetic memory layer.

Optionally, a dielectric layer is filled between adjacent magnetic storage units of the magnetic storage layer.

Optionally, each magnetic storage cell further includes a conductive pillar, and the conductive pillar is located in the sub storage layer above and/or below the magnetic tunnel junction in the magnetic storage cell and electrically connected to the magnetic tunnel junction.

Optionally, a plurality of access transistors are further formed in the substrate and connected to the memory cells in a one-to-one correspondence, where the access transistors include at least one of a planar transistor, a buried gate transistor, and a gate-all-around transistor.

In order to solve the above problems, the present invention further provides a method for forming a magnetic random access memory, including: providing a substrate, wherein a conductive contact pad is formed on the surface of the substrate; and forming a magnetic storage layer connected with the conductive contact pad on the substrate, wherein the magnetic storage layer comprises at least two sub-storage layers stacked on the surface of the substrate, the magnetic storage layer comprises a plurality of magnetic storage units vertically penetrating through the sub-storage layers and arranged in an array form, the magnetic storage units comprise magnetic tunnel junctions, and each sub-storage layer comprises at least one magnetic tunnel junction.

Optionally, the magnetic tunnel junctions in each sub-storage layer are arranged in a random or array.

Optionally, the sub-storage layers are formed layer by layer from the surface of the substrate upwards.

Optionally, the forming method of each sub-storage layer includes: forming a magnetic tunnel junction structure layer, forming a graphical mask layer on the surface of the magnetic tunnel junction structure layer, and etching the magnetic tunnel junction structure layer by taking the graphical mask layer as a mask to form a magnetic tunnel junction; forming a dielectric layer filled between the magnetic tunnel junctions; etching the dielectric layer to form a through hole; and forming the conductive columns for filling the through holes.

Optionally, in the formation process of different sub-storage layers, patterned mask layers with different patterns are respectively used, and the pattern positions of the patterned mask layers are not overlapped.

Optionally, in the magnetic storage layer, a distance between adjacent magnetic storage units is a; when each sub-storage layer is formed, the minimum distance between adjacent patterns of the patterned mask layer is

n is the number of sub-memory layers in the magnetic memory layer.

In the forming method of the magnetic random access memory, the magnetic storage unit array with at least two layers of sub storage layers is formed, the magnetic tunnel junctions of adjacent magnetic storage units are respectively positioned in different sub storage layers, so that the distance between the magnetic tunnel junctions in the same sub storage layer is increased, when the magnetic tunnel junctions in the same sub storage layer are formed, a process window can be increased, the damage to the side wall of the magnetic tunnel junctions caused by etching ion reflection is reduced, the performance of the finally formed memory is improved, and the unit storage density can be further improved.

Furthermore, the number of layers of the sub-storage layers can be reasonably set according to the distance between the storage units of the storage to be formed, and the minimum distance between adjacent magnetic tunnel junctions in the same sub-storage layer is reasonably adjusted, so that the damage to the magnetic tunnel junctions in the process of forming the magnetic tunnel junctions by etching is reduced to the maximum extent.

The magnetic storage layer of the magnetic random access memory comprises at least two sub storage layers, and each sub storage layer comprises at least one magnetic tunnel junction, so that the number of the magnetic tunnel junctions positioned in the same layer is reduced for the same storage unit density, the process window for forming the magnetic tunnel junctions is favorably increased, the quality of the formed magnetic tunnel junctions is improved, and the performance of the memory is improved.

Drawings

FIG. 1 is a diagram of a conventional MRAM architecture;

FIGS. 2 to 3 are schematic structural diagrams illustrating a process of forming a magnetic random access memory according to an embodiment of the present invention;

FIGS. 4 to 13 are schematic structural diagrams illustrating a process of forming a magnetic random access memory according to another embodiment of the present invention;

FIGS. 14 to 15 are schematic structural diagrams of a magnetic random access memory according to another embodiment of the present invention;

FIGS. 16 to 19 are schematic structural diagrams of a magnetic random access memory according to another embodiment of the present invention;

FIG. 20 is a diagram illustrating an MRAM in accordance with another embodiment of the present invention;

FIG. 21 is a diagram illustrating a MRAM according to another embodiment of the invention.

Detailed Description

The following describes in detail a specific embodiment of the magnetic random access memory and a method for forming the same according to the present invention with reference to the accompanying drawings.

Fig. 2 to fig. 3 are schematic structural diagrams illustrating a process of forming a magnetic random access memory according to an embodiment of the present invention.

Referring to fig. 2, a substrate 200 is provided, and a first metal layer 212 and a dielectric layer 211 are formed on a surface of the substrate 200; and forming a magnetic tunnel junction structure layer 220 on the deposition surfaces of the first metal layer 212 and the dielectric layer 211.

Referring to fig. 3, the magnetic tunnel junction structure layer 220 (see fig. 2) is patterned by an exposure etching process to form magnetic tunnel junction pillars 221 arranged in an array. Due to the high storage density requirements of the memory, the distance between adjacent magnetic tunnel junction pillars 221 is small, and the size of the trench to be etched is small. The magnetic tunnel junction structure layer 220 is etched by using a plasma etching process, and etching ions are easily reflected to the side wall of the adjacent magnetic tunnel junction cylinder 221 in a bombardment process, so that the magnetic tunnel junction cylinder 221 is easily damaged, and the performance of a memory and the yield of chips are affected.

The damage of the magnetic tunnel junction pillar 221 due to the reflection of the etching ions can be reduced by increasing the distance between the magnetic tunnel junction pillars 221, but the chip area is increased and the integration of the memory is reduced.

Based on the problems, the invention provides a novel magnetic random access memory and a forming method thereof, which adopt two or more than two deposition-etching steps to distribute the magnetic tunnel junctions in a plurality of sub-storage layers, and the number of the magnetic tunnel junctions to be formed is reduced in each deposition-etching step, thereby increasing the distance between the adjacent magnetic tunnel junctions, enlarging an etching window, reducing the damage to a magnetic tunnel junction cylinder, improving the yield of chips and the performance of the memory, and not reducing the integration level of the memory. In addition, under the condition of the same etching pitch, the storage density of the memory can be increased by forming a plurality of sub-storage layers.

The forming method of the magnetic random access memory comprises the following steps: providing a substrate, wherein a conductive contact pad is formed on the surface of the substrate; and forming a magnetic storage layer connected with the conductive contact pad on the substrate, wherein the magnetic storage layer comprises at least two sub-storage layers stacked in a direction vertical to the surface of the substrate, a magnetic storage unit in the magnetic storage layer comprises a magnetic tunnel junction, and each sub-storage layer comprises at least one magnetic tunnel junction. The new magnetic random access memory and the forming method thereof will be described in detail with reference to the accompanying drawings.

Referring to fig. 4 to 13, there are shown structural diagrams illustrating a process of forming a magnetic random access memory according to an embodiment of the present invention. In this embodiment, two deposition-etch steps are used to form the array of magnetic memory cells.

Referring to fig. 4, a substrate 400 is provided, and a conductive contact pad 412 and a first dielectric layer 411 are formed on a surface of the substrate 400.

The base 400 is a semiconductor substrate, which may be a single crystal silicon substrate, a single crystal germanium substrate, a silicon-on-insulator substrate, a germanium-on-insulator substrate, or the like, and a doped region, a semiconductor device, or the like may be formed in the base 400. The material and structure of the substrate 400 can be selected according to the specific design and practical requirements of the memory, and are not limited herein.

In one embodiment, the substrate 400 includes a substrate having an access transistor formed thereon and a dielectric layer covering the surface of the substrate having a conductive structure formed therein that is connected to the access transistor. The access transistor can adopt any transistor structure, and can be at least one of various types of transistor structures such as a buried gate structure transistor, a gate-all-around field effect transistor and a planar structure transistor.

The substrate 400 has a conductive contact pad 412 formed on a surface thereof, and the conductive contact pad 412 is used for connecting a magnetic memory cell to be formed subsequently. The conductive contact pad 412 is also connected to a conductive structure in the substrate 400 to connect to a drain of an access transistor in the substrate 400.

The first dielectric layer 411 serves as an isolation structure between the conductive contact pads 412. The forming method of the first dielectric layer 411 and the conductive contact pad 412 includes: depositing a first dielectric layer 411 on the surface of the substrate 400, etching the first dielectric layer 411, forming a through hole in the first dielectric layer 411, filling a conductive material in the through hole, and planarizing to form the conductive contact pad 412.

In another embodiment, the method for forming the first dielectric layer 411 and the conductive contact pad 412 includes: after depositing a first metal material layer on the surface of the substrate 400, patterning the first metal material layer to form a patterned conductive contact pad 412; after forming the first dielectric material layer covering the substrate 400 and the conductive contact pad 412, the first dielectric material layer is planarized to expose the surface of the conductive contact pad 412, so as to form the first dielectric layer 411.

The arrangement density and the position of the conductive contact pads 412 are set according to the arrangement position and the density of the memory cells of the magnetic random access memory to be formed. In this particular embodiment, the spacing between adjacent conductive contact pads 412 is the lateral spacing between adjacent magnetic storage cells in the memory to be formed.

Referring to fig. 5, a first magnetic tunnel junction structure layer 500 is formed on the surfaces of the first dielectric layer 411 and the conductive contact pad 412.

The first magnetic tunnel junction structure layer 500 includes a pinned layer, a tunneling layer, and a free layer stacked from bottom to top, which are not specifically shown in fig. 5.

Referring to fig. 6, a first patterned mask layer 600 is formed on the surface of the first magnetic tunnel junction structure layer 500. The first patterned mask layer 600 may be made of a mask material such as photoresist or silicon oxide. The first patterned mask layer 600 is used to define the location and size of a first magnetic tunnel junction within a first sub-storage layer.

Referring to fig. 7, the magnetic tunnel junction structure layer 500 (see fig. 6) is etched using the first patterned mask layer 600 as a mask to form a first magnetic tunnel junction 501 on a portion of the surface of the conductive contact pad 412.

In this embodiment, the first magnetic tunnel junctions 501 are formed only on a portion of the surface of the conductive contact pad 412, so that the distance between adjacent first magnetic tunnel junctions 501 may be greater than the minimum distance between magnetic memory cells to be finally formed, and thus the possibility that the reflected etching ions damage the sidewalls of the first magnetic tunnel junctions 501 during the etching of the magnetic tunnel junction structure layer 500 may be reduced, thereby improving the quality of the formed first magnetic tunnel junctions 501.

The number of the magnetic tunnel junctions in each storage layer can be randomly set according to the number of the sub-storage layers of the magnetic storage layer of the memory to be formed, so that at least one magnetic tunnel junction is formed in each sub-storage layer, the distance between at least part of adjacent magnetic tunnel junctions in each storage layer is larger than the distance between the storage units, and the number of the magnetic tunnel junctions damaged due to ion reflection in the process of forming the magnetic tunnel junctions can be reduced to a certain extent.

To minimize damage to the magnetic tunnel junctions, the magnetic tunnel junctions in adjacent memory cells may be located in different sub-storage layers such that the minimum spacing between the magnetic tunnel junctions in each sub-storage layer is greater than the minimum spacing between memory cells.

In one embodiment, the number of memory cells of the memory to be formed is a, and the magnetic memory cell array is formed by using n deposition-etching processes, then the number of magnetic tunnel junctions formed at each time can be an integer closest to a/n. In other embodiments, the number of magnetic tunnel junctions formed at a time may be set according to practical situations, and it is only necessary that the spacing between at least two magnetic tunnel junctions in the sub-storage layers formed at a time is larger than the minimum spacing between the storage units of the memory to be formed.

In this embodiment, the number of the first magnetic tunnel junctions 501 formedIs A/2, and A is an even number. In other embodiments, if a is an odd number, the number of magnetic tunnel junctions formed twice may be respectively

And

referring to fig. 8, the first patterned mask layer 600 (see fig. 6) is removed, and a second dielectric layer 800 is filled between adjacent first magnetic tunnel junctions 501.

The material of the second dielectric layer 800 may be an insulating dielectric material such as silicon oxide, silicon oxynitride, or the like. After depositing a second dielectric material layer on the surfaces of the first dielectric layer 411 and the conductive contact pad 412, planarizing the second dielectric material layer by using the first magnetic tunnel junction 501 as a stop layer to form the second dielectric layer 800.

Referring to fig. 9, the second medium 800 is etched to form a via hole on the surface of the conductive contact pad 412 between the adjacent first magnetic tunnel junctions 501; filling the first conductive pillar 900 connected to the conductive contact pad 412 in the via. The vias expose the surfaces of the other conductive contact pads 412.

Referring to fig. 10, a second magnetic tunnel junction structure layer 1000 is formed to cover the second dielectric layer 800, the first magnetic tunnel junction 501 and the first conductive pillar 900; and forming a second patterned mask layer 1001 on the surface of the second magnetic tunnel junction structure layer 1000, wherein the second patterned mask layer 1001 is used for defining the position and size of a second magnetic tunnel junction in a second sub-storage layer.

Referring to fig. 11, the second patterned mask layer 1001 (see fig. 10) is used as a mask to etch the second magnetic tunnel junction structure layer 1000 (see fig. 10) to form a second magnetic tunnel junction 1002; a third dielectric layer 1100 is filled between the second magnetic tunnel junctions 1002.

In this particular embodiment, the number of second magnetic tunnel junctions 1002 is A/2.

The pattern positions of the second patterned mask layer 1001 (see fig. 10) and the first patterned mask layer 600 (see fig. 6) are not overlapped, so that the first magnetic tunnel junction 501 and the second magnetic tunnel junction 1002 are not overlapped in a direction perpendicular to the surface of the substrate 400.

The distance between adjacent second magnetic tunnel junctions 1002 is large, so that in the process of etching the second magnetic tunnel junction structure layer 1000 to form the second magnetic tunnel junction 1002, the damage to the second magnetic tunnel junction 1002 caused by etching ion reflection can be reduced.

Referring to fig. 12, the third dielectric layer 1100 is etched to form a through hole exposing the first magnetic tunnel junction 501, and the through hole is filled with the second conductive pillar 1200.

The second conductive pillar 1200 is electrically connected to the underlying first magnetic tunnel junction 501. Bit lines connected to the second conductive pillars 1200 and the second magnetic tunnel junctions 1001 are formed on the surface of the third dielectric layer 1100.

The first sub-storage layer where the first magnetic tunnel junction 501 is located and the second sub-storage layer where the second magnetic tunnel junction 1001 is located constitute a magnetic storage layer on the surface of the substrate 400. Each magnetic storage unit in the magnetic storage layer comprises a magnetic tunnel junction and a conductive column connected with the top or the bottom of the magnetic tunnel junction.

FIG. 13 is a schematic diagram of the location of each magnetic memory cell in the magnetic memory layer according to this embodiment. FIG. 12 is a schematic sectional view taken along the cut line AA' in FIG. 13. The circles with

numbers

1 and 2 in fig. 13 represent memory cells having a first magnetic tunnel junction 501 and a second magnetic tunnel junction 1002, respectively, and the first magnetic tunnel junction 501 and the second magnetic tunnel junction 1002 are located in different sub-memory layers, respectively.

In this embodiment, the individual magnetic storage cells are arranged in the form of a rectangular array of cells. The magnetic tunnel junctions of each row and each column are alternately distributed in the first sub-storage layer and the second sub-storage layer, so that the magnetic tunnel junctions in each sub-storage layer are also arranged in an array.

In the magnetic storage layer, a magnetic layer is formed,the spacing between adjacent magnetic memory cells is a (the distance between the central axes of adjacent memory cells). Taking the second sub-storage layer as an example, two pitches, d1 and d2, are formed between the adjacent second magnetic tunnel junctions 1002 in the second sub-storage layer, where d2 is 2a,

are all greater than a.

Therefore, the first sub-storage layer and the second sub-storage layer are sequentially formed through two deposition-etching steps, and in the process of forming the magnetic tunnel junction through each etching, the minimum distance between at least part of adjacent magnetic tunnel junctions in the same sub-storage layer can be increased, so that the damage to the side wall of the magnetic tunnel junction caused by etching ion reflection can be reduced, and the performance of the finally formed memory is improved.

In other embodiments, three or more sub-storage layers may be formed, and the number of magnetic tunnel junctions in each sub-storage layer may be further reduced, thereby increasing the minimum spacing between adjacent magnetic tunnel junctions in each sub-storage layer. And in the forming process of different sub-storage layers, graphical mask layers with different graphs are respectively adopted, and the graph positions for defining the magnetic tunnel junctions in the graphical mask layers are not overlapped.

The number and the positions of the magnetic tunnel junctions in each sub-storage layer can be randomly set; the number and the positions of the magnetic tunnel junctions in each sub-storage layer can be set according to a certain rule, so that the distribution of the magnetic tunnel junctions in each sub-storage layer is regular, the density of the magnetic tunnel junctions in each sub-storage layer is uniform, heat generated by the magnetic tunnel junctions is uniformly distributed in each sub-storage layer in the working process of the memory, and the problem of over-fast local temperature rise is avoided.

In a specific embodiment of the present invention, a minimum spacing between adjacent magnetic storage cells within a magnetic storage layer of a memory to be formed is a; when the magnetic tunnel junctions in the adjacent memory cells are respectively positioned in different sub-memory layers, the damage to the magnetic tunnel junctions can be reduced to the greatest extent. At the time of forming each of the sub-storage layers,the minimum spacing between adjacent patterns of the patterned mask layer employed may be

I.e., the minimum spacing between the formed magnetic tunnel junctions is

Where n is the number of sub-memory layers included in the magnetic memory layer.

For example, in the case of forming three sub-memory layers using three deposition-etching steps, the minimum spacing between magnetic tunnel junctions located in the same layer can be increased to

In the case where four deposition-etching steps are used to form four sub-memory layers, the minimum spacing between magnetic tunnel junctions located in the same layer can be increased to 2 a.

Referring to fig. 14 and 15, a memory cell of a magnetic random access memory formed by three deposition-etching steps according to another embodiment of the present invention is shown, and fig. 15 is a cross-sectional view along a cut line BB' in fig. 14.

In this embodiment, the magnetic memory layer formed on the substrate 1500 includes three sub-memory layers. The circles in which

numbers

1, 2, and 3 are located respectively indicate memory cells having first magnetic tunnel junction 1501, second magnetic tunnel junction 1502, and third magnetic tunnel junction 1503, which are sequentially located in the first to third sub-memory layers.

In this embodiment, the memory cells of the memory are arranged in a diamond array. The magnetic tunnel junctions in the memory cells in each row are sequentially distributed in the first sub-memory layer, the second sub-memory layer and the third sub-memory layer, so that the magnetic tunnel junctions in each sub-memory layer are also arranged in an array form, the number of the magnetic tunnel junctions in each sub-memory layer is close, and the magnetic tunnel junctions in each sub-memory layer are uniformly distributed.

Storage in the magnetic random access memoryAnd under the condition that the minimum distance between the storage units is a, three deposition-etching steps are adopted, so that the formed magnetic storage unit array has three sub storage layers. Taking the first sub-storage layer as an example, three different pitches, c1, c2 and c3, are formed between the adjacent first magnetic tunnel junctions 1501 in the first sub-storage layer; when the minimum spacing between adjacent memory cells is a, c1 is 3a,

c3 is 2a with a minimum spacing of

Greater than the minimum spacing a between magnetic storage cells in the array of magnetic storage cells.

Referring to fig. 16, 17 and 18, a memory cell of a magnetic random access memory formed by four deposition-etching steps according to another embodiment of the present invention is shown, fig. 17 is a cross-sectional view taken along a cut line CC ' in fig. 16, fig. 18 is a cross-sectional view taken along a cut line DD ' in fig. 16, and fig. 18 is a cross-sectional view taken along a cut line EE ' in fig. 16.

In this embodiment, the magnetic storage layer formed on the substrate 1700 includes four sub-storage layers, where the circles numbered 1, 2, 3, and 4 in fig. 16 are used to represent memory cells having the first magnetic tunnel junction 1701, the second magnetic tunnel junction 1702, the third magnetic tunnel junction 1703, and the fourth magnetic tunnel junction 1704, respectively, and the first magnetic tunnel junction 1701, the second magnetic tunnel junction 1702, the third magnetic tunnel junction 1703, and the fourth magnetic tunnel junction 1704 are sequentially located in the first to fourth sub-storage layers.

In this embodiment, the memory cells are arranged in a rectangular array unit, the magnetic tunnel junctions in each row of memory cells are respectively distributed in two sub-memory layers at intervals, and the magnetic tunnel junctions in adjacent rows of memory cells are respectively located in different sub-memory layers. For example, the magnetic tunnel junctions of the memory cells of the first row are respectively located in the third and second sub-storage layers, and the magnetic tunnel junctions of the memory cells of the second row are respectively located in the first and fourth sub-storage layers, and the distribution of the magnetic tunnel junctions of the memory cells of the first row is consistent with that of the memory cells of the first row in every three rows. When the minimum pitch between adjacent memory cells is a, taking the third sub-memory layer as an example, the minimum pitch e between adjacent third magnetic tunnel junctions 1703 is 2 a.

In other specific embodiments, the arrangement form of the memory cells may not be limited, and the memory cells may be arranged in a regular array or may be randomly distributed. Also, the arrangement positions of the magnetic tunnel layers within the respective sub-storage layers may be arranged randomly or in an array.

In the forming process of the memory, at least two layers of memory cell sub-memory layers are sequentially formed through at least two deposition-etching steps, and a magnetic tunnel junction of a memory cell is formed in each sub-memory layer. Therefore, the space between part of adjacent magnetic tunnel junctions in the same sub-storage layer can be at least increased, so that when the magnetic tunnel junction structure layer is etched, the damage to the side wall of the magnetic tunnel junction caused by the reflection of etching ions is reduced, the process window is enlarged, and the performance of the finally formed memory is improved.

Also, as the number of sub-storage layers formed increases, the minimum spacing between adjacent magnetic tunnel junctions within the same sub-storage layer increases. The number of the sub array layers can be reasonably set according to the minimum distance between the storage units of the memory to be formed and the minimum distance required by etching for forming the magnetic tunnel junction with higher quality, and the performance of the memory is improved to the maximum extent on the premise of not changing the storage density of the memory.

The invention also provides a magnetic random access memory formed by the method.

Please refer to fig. 12 and 13, which are schematic structural diagrams of a magnetic random access memory according to an embodiment of the present invention. FIG. 12 is a schematic sectional view taken along the cut line AA' in FIG. 13.

The magnetic random access memory includes: a substrate 400, wherein a conductive contact pad 412 is formed on the surface of the substrate 400; the magnetic storage layer is positioned on the surface of the substrate 400 and comprises at least two sub-storage layers stacked on the surface of the substrate, a plurality of magnetic storage units vertically penetrating through the sub-storage layers and connected with the conductive contact pads are arranged in the magnetic storage layers, the magnetic storage units comprise magnetic tunnel junctions, and each sub-storage layer comprises at least one magnetic tunnel junction.

The magnetic tunnel junction includes a fixed layer, a tunneling layer, and a free layer stacked.

A plurality of access transistors are formed in the substrate 400 and are connected to the memory cells in a one-to-one correspondence, and the access transistors include at least one of a planar transistor, a buried gate transistor, and a gate-all-around transistor.

In this embodiment, a first dielectric layer 411 is formed between adjacent conductive contact pads 412. The first dielectric layer 411 is made of an insulating material and serves as an isolation layer between the conductive contact pads 412. The magnetic storage layer comprises two sub-storage layers, a first magnetic tunnel junction 501 is formed in the first sub-storage layer, a second magnetic tunnel junction 1002 is formed in the second sub-storage layer, and the first magnetic tunnel junction 501 and the second magnetic tunnel junction 1002 belong to different storage units respectively.

The first sub-storage layer further includes a first conductive pillar 900 connected to the conductive contact pad 412 and the second magnetic tunnel junction 1002, and a second dielectric layer 800 is formed between the first conductive pillar 900 and the first magnetic tunnel junction 501.

The second sub-storage layer further includes a second conductive pillar 1200 connected to the first magnetic tunnel junction 501, and a third dielectric layer 1100 is formed between the second conductive pillar 1200 and the second magnetic tunnel junction 1002.

In fig. 13, circles numbered 1 and 2 represent memory cells in which the first magnetic tunnel junction 501 and the second magnetic tunnel junction 1002 are located, respectively. In this embodiment, the individual magnetic storage cells are arranged in the form of a rectangular array of cells. The magnetic tunnel junctions of each row and each column are alternately distributed in the first sub-storage layer and the second sub-storage layer, so that the magnetic tunnel junctions in each sub-storage layer are also arranged in an array. Two distances are respectively d1 and d2 between adjacent magnetic tunnel junctions in each sub storage layer. When adjacent memory cellWith a minimum distance therebetween, d 1-2 a,

referring to fig. 14 and 15, there are shown schematic structural diagrams of a magnetic random access memory according to another embodiment of the present invention. Fig. 15 is a schematic sectional view along the cut line BB' in fig. 14.

In this embodiment, the magnetic random access memory includes a substrate 1500 and a magnetic storage layer formed on the substrate 1500, the magnetic storage layer includes three sub-storage layers from the surface of the substrate 1500 to the top, a first magnetic tunnel junction 1501 is formed in a first sub-storage layer at the bottom layer, a second magnetic tunnel junction 1502 is formed in a second sub-storage layer at the surface of the first sub-storage layer, and a third magnetic tunnel junction 1503 is formed in a third sub-storage layer at the surface of the second sub-storage layer; the first magnetic tunnel junction 1501, the second magnetic tunnel junction 1502 and the third magnetic tunnel junction 1503 are located in different memory cells. Each sub-storage layer is also formed with a conductive pillar that connects the magnetic tunnel junction in the upper or/lower sub-storage layer. And the conductive columns in the same sub-storage layer are isolated from the magnetic tunnel junctions by the dielectric layer.

In fig. 15,

reference numerals

1, 2, and 3 denote memory cells in which the first magnetic tunnel junction 1501, the second magnetic tunnel junction 1502, and the third magnetic tunnel junction 1503 are located, respectively. In this embodiment, three spacings, c1, c2 and c3, exist between adjacent magnetic tunnel junctions in each sub-memory layer. When the minimum spacing between adjacent memory cells is a, c1 is 3a,

c3 is 2a with a minimum spacing of

Are larger than the minimum spacing a between memory cells in the memory cell array.

Referring to fig. 16, 17 and 19, a memory cell of a magnetic random access memory according to another embodiment of the present invention is shown, fig. 17 is a cross-sectional view taken along a cut line CC ' in fig. 16, fig. 18 is a cross-sectional view taken along a cut line DD ' in fig. 16, and fig. 19 is a cross-sectional view taken along a cut line EE ' in fig. 16.

The magnetic storage layer formed on the substrate 1700 of the magnetic random access memory in this embodiment includes four sub-array layers, where the circles numbered 1, 2, 3 and 4 in fig. 16 represent the memory cells in which the first magnetic tunnel junction 1701, the second magnetic tunnel junction 1702, the third magnetic tunnel junction 1703 and the fourth magnetic tunnel junction 1704 are located, respectively, and the first magnetic tunnel junction 1701, the second magnetic tunnel junction 1702, the third magnetic tunnel junction 1703 and the fourth magnetic tunnel junction 1704 are sequentially located in the first to fourth sub-storage layers.

In this embodiment, the memory cells are arranged in a rectangular array unit, the magnetic tunnel junctions in each row of memory cells are respectively distributed in two sub-memory layers at intervals, and the magnetic tunnel junctions in adjacent rows of memory cells are respectively located in different sub-memory layers. For example, the magnetic tunnel junctions of the memory cells of the first row are respectively located in the third and second sub-storage layers, and the magnetic tunnel junctions of the memory cells of the second row are respectively located in the first and fourth sub-storage layers, and the distribution of the magnetic tunnel junctions of the memory cells of the first row is consistent with that of the memory cells of the first row in every three rows.

When the minimum pitch between adjacent memory cells is a, taking the third sub-memory layer as an example, the minimum pitch e between adjacent third magnetic tunnel junctions 1703 is 2a, which is larger than the minimum pitch between adjacent memory cells.

In other embodiments, the magnetic random access memory comprises an array of magnetic storage cellsThe magnetic storage device comprises n stacked sub storage layers, the spacing between adjacent magnetic storage units is a, when the magnetic tunnel junctions in the adjacent storage units are respectively positioned in different sub storage layers, the minimum spacing between the adjacent magnetic tunnel junctions in the same sub storage layer is

In other embodiments of the present invention, the number of magnetic tunnel junctions in each storage layer may be randomly set according to the number of sub-storage layers of a magnetic storage layer of a memory to be formed, so that at least one magnetic tunnel junction is formed in each sub-storage layer, and thus, the distance between at least some adjacent magnetic tunnel junctions in each storage layer is greater than the distance between storage units, which may reduce the number of magnetic tunnel junctions damaged by ion reflection during the formation of the magnetic tunnel junctions to a certain extent.

To minimize damage to the magnetic tunnel junctions, the magnetic tunnel junctions in adjacent memory cells may be located in different sub-memory layers such that the minimum spacing between the magnetic tunnel junctions in each sub-memory layer is greater than the minimum spacing between the memory cells. When the magnetic tunnel junctions in the sub-storage layers are distributed regularly and the density of the magnetic tunnel junctions in the sub-storage layers is uniform, the heat generated by the magnetic tunnel junctions is uniformly distributed in the sub-storage layers in the working process of the memory, so that the problem of too fast local temperature rise is avoided.

In other specific embodiments, the arrangement form of the memory cells of the memory may not be limited, and the memory cells may be arranged in an array according to a certain rule or may be distributed randomly. Also, the arrangement positions of the magnetic tunnel layers within the respective sub-storage layers may be arranged randomly or in an array.

Compared with the magnetic random access memory with all the magnetic tunnel junctions on the same layer, the magnetic tunnel junctions of the magnetic random access memory are distributed in at least two sub-storage layers, the distance between at least part of the magnetic tunnel junctions in the same sub-storage layer is increased, the process window for forming the magnetic tunnel junctions can be effectively improved, the damage to the side walls of the magnetic tunnel junctions caused by the reflection of etching ions is reduced, the quality of the formed magnetic tunnel junctions is improved, and the performance of the magnetic random access memory is improved.

Please refer to fig. 20, which is a schematic structural diagram of a memory according to another embodiment of the present invention.

In this embodiment, a ring gate type transistor is formed in the substrate 2000 of the memory as an access transistor.

Specifically, the base 2000 includes a substrate 2001, memory access transistors 2002 formed on the substrate 2001, and isolation layers 2003 located between the access transistors 2002.

The access transistor 2002 is a vertical Gate All Around FET (vertical Gate All Around FET) and includes a source 2004, a channel region 2005, and a drain 2006 arranged vertically upward from a surface of a substrate 2001, a Gate 2007 disposed Around the channel region 2005, and a Gate dielectric layer 2008 between the Gate 2007 and the channel region 2005.

The substrate 2000 further includes a dielectric layer 2009 covering the isolation layer 2003 and the access transistor 2002, and a first electrical contact 2010 connected to the drain 2006 is further formed in the dielectric layer 2009.

The substrate 2000 has a surface formed with electrically conductive contact pads 2013, the electrically conductive contact pads 2013 being connected to the first electrical contacts 2010. The conductive contact pad 2013 is formed in a dielectric layer 2012.

A storage layer 2020 is formed over the substrate 2000, the storage layer 2020 includes a first sub-storage layer 2021 and a second sub-storage layer 2022, the storage layer 2020 includes memory cells vertically penetrating through each sub-storage layer, and the memory cells include

magnetic tunnel junctions

2031 and 2032 and conductive pillars 2033 above and/or below the magnetic tunnel junctions. In other embodiments, the storage layer 2020 may further include more than three sub-storage layers.

An access transistor 2002 is formed in the substrate 2000 under each memory cell, and each memory cell is electrically connected to the drain 2006 of the access transistor 2002 thereunder.

The memory cells in the memory layer 2020 may be arranged in a regular array, for example, in a diamond array or in a rectangular array.

In this embodiment, the magnetic tunnel junctions of the memory cells may be randomly distributed or distributed in an array within the first and second

sub-memory layers

2021 and 2022. In one embodiment, the magnetic tunnel junctions 2031 within the first sub-storage layer 2021 are distributed in rectangular array cells; the magnetic tunnel junctions 2032 within the second sub-storage layer 2022 are distributed in the form of rectangular array cells.

In other specific embodiments, the magnetic tunnel junctions 2031 within the first sub-storage layer 2021 are distributed in the form of diamond-shaped array cells; the magnetic tunnel junctions 2032 within the second sub-storage layer 2022 are distributed in the form of diamond-shaped array cells.

In other embodiments, the magnetic tunnel junctions 2031 in the first sub-storage layer 2021 and the magnetic tunnel junctions 2032 in the second sub-storage layer 2022 may also be randomly distributed.

In this particular embodiment, only one example structure of the access transistor 2002 is given. In other embodiments, the access transistor 2002 may also have a surrounding Gate structure, for example, the access transistor 2002 may also be a fin field effect transistor (FinFET) or a planar Gate All around fet.

The fin field effect transistor (FinFET) comprises a raised fin part formed on the surface of a substrate, and a grid electrode crossing the fin part, wherein the grid electrode surrounds the top and the side wall of a channel region; the source electrode and the drain electrode are respectively positioned in the fin parts at two sides of the grid electrode.

The planar surrounding gate structure comprises a channel region suspended on the surface of the substrate, a source electrode and a drain electrode which are positioned on the surface of the substrate and respectively connected with two sides of the channel region, and a gate electrode surrounding the channel region.

In other embodiments, other structures of the access transistor, such as a buried gate transistor, may be used to reduce the size of the memory transistor.

In this specific embodiment, a second dielectric layer 2024 is further formed on the surface of the storage layer 2020, and a third contact portion 2023 for connecting each memory cell is formed in the second dielectric layer 2024; a Bit Line (Bit Line)2030 and the third contact portion 2023 are formed on the surface of the second dielectric layer 2023.

The spacing between memory cells of a memory is limited not only by the process window of etching to form the magnetic tunnel junctions, but also by the size of the access transistors below the memory cells. In the above specific embodiment, the magnetic tunnel junctions of the storage units of the storage are distributed in the plurality of sub-storage layers, and the sub-storage layers are formed separately, so that on the premise that the magnetic tunnel junctions in the storage units are not overlapped in the vertical direction, the spacing between the magnetic tunnel junctions in the sub-storage layers can be set according to the limitation of the minimum process window, and thus the minimum spacing between the finally formed storage units can be increased, and the storage density of the storage is increased.

Furthermore, the access transistor in the substrate adopts a gate-all-around transistor, so that the size of the gate-all-around transistor can be greatly reduced, the minimum spacing between the memory cells can be reduced, and the storage density of the memory is improved.

In other specific embodiments, a buried gate transistor may be further formed in the substrate of the memory as an access transistor, a gate of the access transistor is located in the substrate, and a source and a drain of the access transistor are respectively located on two sides of the gate and have a bottom higher than a top of the gate.

Please refer to fig. 21, which is a schematic structural diagram of a memory according to another embodiment of the present invention.

Specifically, the substrate 2100 includes a substrate 2101, and the substrate 2101 includes an active region and an isolation structure 2102 surrounding the active region. In one embodiment, the isolation structures 2102 may be shallow trench isolation structures.

The access transistor is formed in an active region of the substrate 2101, the access transistor comprises a gate 2103 embedded in the substrate 2101, a source 2105 and a drain 2106 are respectively positioned in the substrate 2101 at two sides of the gate 2103, and the bottom of the access transistor is higher than the top of the gate 2103. An isolation layer 2107 is formed on top of the gate 2103, flush with the surface of the substrate 2101. A gate dielectric layer 2104 is formed between the gate 2103 and the substrate 2101.

In this embodiment, two adjacent transistors are formed in each active region, i.e., two gates 2104 are formed in the substrate 2101, and the adjacent transistors share the same source. Specifically, the source 2105 is located between two adjacent gates 2104, and the drain 2106 is located outside the gates 2104.

The base 2100 further includes a first dielectric layer 2108 covering the surface of the substrate 2101, the conductive contact pads 2013 being formed within the first dielectric layer 2108. A first electrical contact 2109 connected with the drain electrode 2106 and a second electrical contact 2110 connected with the gate electrode 2103 are further formed in the first dielectric layer 2108, and the second electrical contact 2110 is used for connecting a Source Line (Source Line).

The conductive contact pads 2113 on the surface of the substrate 2100 are connected to the first electrical contacts 2109. A memory layer 2120 is formed over the substrate 2100, the memory layer 2120 includes a first sub-memory layer 2121 and a second sub-memory layer 2122, the memory layer 2120 includes memory cells vertically penetrating through the respective sub-memory layers, and the magnetic memory cells include

magnetic tunnel junctions

2131 and 2132 and conductive pillars 2133 above and/or below the magnetic tunnel junctions. In other embodiments, the storage layer 2120 may further include more than three sub-storage layers.

In another embodiment, only one access transistor may be formed in each active region of the substrate 2101, including a gate buried in the active region, a source and a drain on either side of the gate, the drain being connected to the conductive contact 2113 to electrically connect to the magnetic tunnel junction 2131 and the magnetic tunnel junction 2132.

In this embodiment, a second dielectric layer 2124 is further formed on the surface of the storage layer 2020, and a third contact portion 2123 for connecting each memory cell is formed in the second dielectric layer 2124; a Bit Line (Bit Line)2130 is formed on the surface of the second dielectric layer 2123 and connected to the third contact 2123.

The access transistor in the substrate adopts a buried gate transistor, so that the size of the transistor can be greatly reduced, the minimum spacing between the memory units can be reduced, and the storage density of the memory is improved. And the source electrode can be shared between the adjacent transistors, thereby further reducing the minimum space between the memory units.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A magnetic random access memory, comprising:

the surface of the substrate is provided with a conductive contact pad;

the magnetic storage layer is positioned on the surface of the substrate and comprises at least two sub-storage layers stacked on the surface of the substrate, a plurality of magnetic storage units vertically penetrating through the sub-storage layers and connected with the conductive contact pads are arranged in the magnetic storage layers, the magnetic storage units comprise magnetic tunnel junctions, and each sub-storage layer comprises at least one magnetic tunnel junction.

2. The MRAM of claim 1, wherein the magnetic tunnel junctions of the plurality of magnetic storage cells are randomly arranged within each sub-storage layer.

3. The magnetic random access memory according to claim 1, wherein the magnetic tunnel junctions in each sub-storage layer are arranged in a random pattern or an array pattern.

4. The MRAM of claim 1, wherein the magnetic tunnel junctions of adjacent magnetic storage cells are respectively located in different sub-storage layers.

5. The MRAM of claim 1, wherein at least some of the adjacent magnetic tunnel junctions within the same sub-storage layer are spaced apart by a distance greater than a minimum spacing between the magnetic random access memory cells.

6. The magnetic random access memory according to claim 1, wherein the magnetic storage layer has a spacing a between adjacent magnetic storage cells; the minimum spacing between adjacent magnetic tunnel junctions in the same sub-storage layer is

n is the number of sub-memory layers in the magnetic memory layer.

7. The MRAM of claim 1, wherein a dielectric layer is filled between adjacent magnetic storage cells of the magnetic storage layer.

8. The MRAM of claim 1, wherein each magnetic storage cell further comprises a conductive pillar located in the sub-storage layer above and/or below the magnetic tunnel junction in the magnetic storage cell and electrically connected to the magnetic tunnel junction.

9. The MRAM of claim 1, wherein the substrate further has a plurality of access transistors formed therein, the access transistors being connected to the memory cells in a one-to-one correspondence, the access transistors including at least one of planar transistors, buried gate transistors, and gate-all-around transistors.

10. A method for forming a Magnetic Random Access Memory (MRAM) device, comprising:

providing a substrate, wherein a conductive contact pad is formed on the surface of the substrate;

and forming a magnetic storage layer connected with the conductive contact pad on the substrate, wherein the magnetic storage layer comprises at least two sub-storage layers stacked on the surface of the substrate, the magnetic storage layer comprises a plurality of magnetic storage units vertically penetrating through the sub-storage layers and arranged in an array form, the magnetic storage units comprise magnetic tunnel junctions, and each sub-storage layer comprises at least one magnetic tunnel junction.

11. The method of claim 10, wherein the magnetic tunnel junctions of the plurality of magnetic storage cells are randomly arranged in each of the sub-storage layers.

12. The method of claim 10, wherein the magnetic tunnel junctions in each sub-storage layer are arranged in a random pattern or an array pattern.

13. The method of claim 10, wherein the magnetic tunnel junctions of adjacent magnetic storage cells are located in different sub-storage layers.

14. The method as claimed in claim 10, wherein each of the magnetic memory cells further includes a conductive pillar located in the sub-storage layer above and/or below the magnetic tunnel junction in the magnetic memory cell and electrically connected to the magnetic tunnel junction.

15. The method of claim 10, wherein the sub-memory layers are formed layer by layer from the surface of the substrate upward.

16. The method of claim 15, wherein the sub-memory layers are formed by a method comprising: forming a magnetic tunnel junction structure layer, forming a graphical mask layer on the surface of the magnetic tunnel junction structure layer, and etching the magnetic tunnel junction structure layer by taking the graphical mask layer as a mask to form a magnetic tunnel junction; forming a dielectric layer filled between the magnetic tunnel junctions; etching the dielectric layer to form a through hole; and forming the conductive columns for filling the through holes.

17. The method of claim 15, wherein different patterned mask layers with different patterns are used during the formation of different sub-memory layers, and the pattern positions of the patterned mask layers are not overlapped.

18. The method of claim 17, wherein a spacing between at least some adjacent magnetic tunnel junctions in the same sub-memory layer is greater than a minimum spacing between magnetic random access memory cells.

19. The method of claim 10, wherein the magnetic memory layer has a spacing a between adjacent magnetic memory cells; when each sub-storage layer is formed, the minimum distance between adjacent patterns of the patterned mask layer is

n is the number of sub-memory layers in the magnetic memory layer.

20. The method as claimed in claim 10, wherein a plurality of access transistors are formed in the substrate and connected to the memory cells in a one-to-one correspondence, wherein the access transistors include at least one of planar transistors, buried gate transistors, and gate-all-around transistors.