CN114361202A - Phase change memory cell and manufacturing method thereof - Google Patents

Abstract

The invention relates to a phase change memory cell and a manufacturing method thereof, wherein the phase change memory cell comprises: a substrate; the lower electrode is arranged in the substrate, and the upper contact surface of the lower electrode is exposed outside the substrate and is flush with the upper surface of the substrate; the horizontal part of the phase-change material layer is connected with the lower electrode, and the phase-change material layer is L-shaped; the filling material is arranged above the vertical part of the phase change material layer and forms a phase change storage structure together with the phase change material layer; and the upper electrode is arranged above the phase change material layer. The invention can effectively reduce the phase change area of the phase change memory unit.

Description

A phase change memory cell and method of making the same

technical field

The invention relates to the technical field of microelectronics, in particular to a phase-change memory cell and a manufacturing method thereof.

Background technique

The phase change memory technology is based on the phase change thin film proposed by Ovshinsky in the late 1960s (Phys. Rev. Lett., 21, 14501453, 1968) and the early 1970s (Appl. Phys. The concept of applying the phase change storage medium is established, which is a storage device with low price and stable performance. Phase change memory can be made on silicon wafer substrate, and its key materials are recordable phase change films, heating electrode materials11, thermal insulation materials and lead-out electrode materials. , including how to reduce device material, etc. The basic principle of phase change memory is to use electrical pulse signals to act on the device unit to make the phase change material undergo a reversible phase transition between amorphous and polycrystalline states. The low resistance can realize the writing, erasing and reading operations of information.

Phase change memory is considered by the International Semiconductor Industry Association as the most likely to replace the current flash memory due to its advantages of high-speed reading, high rewritable times, non-volatile, small component size, low power consumption, strong vibration resistance and radiation resistance. The memory will become the mainstream memory product in the future and the first device to become a commercial product.

The read, write and erase operations of the phase change memory are to apply voltage or current pulse signals of different widths and heights on the device unit: erase operation (RESET), when a short and strong pulse signal is added to make the phase change material in the device unit After the temperature rises above the melting temperature, it is rapidly cooled to realize the transformation from the polycrystalline state to the amorphous state of the phase change material, that is, the transformation from the "1" state to the "0" state; the write operation (SET), when a A long and medium-intensity pulse signal raises the temperature of the phase change material below the melting temperature and above the crystallization temperature, and maintains it for a period of time to promote the growth of the crystal nucleus, thereby realizing the transformation from amorphous to polycrystalline state, that is, "0" State to "1" state conversion; read operation, after adding a very weak pulse signal that will not affect the state of the phase change material, read its state by measuring the resistance value of the device unit.

The research of memory has been developing in the direction of high speed, high density, low power consumption and high reliability. At present, most of the institutions engaged in the research and development of phase change memory in the world are large companies in the semiconductor industry. One of the focuses of their attention is how to reduce the size of the heating electrode of the phase change memory. Type heating electrode (Proc.Symp.Very Large Scale Integr.(VLSI)Technol., 2003:175-176), annular heating electrode (Jpn.J.Appl.Phys.,2006,45(4B):3233-3237) With blade-shaped heater electrode (IEEE Conference Proceedings of International Electron Devices Meeting, 2011, 3.1.1-3.1.4) and STMicroelectronics' μ-type heater electrode (Proc. Symp. Very Large Scale Integr. (VLSI) Technol., 2004 , 3.1:18-19), but the disadvantage of the above structure is that low power consumption is mainly achieved by reducing the size of the electrode, while the size of the phase change material is relatively large, and the gate tube has a significant impact on the density of the phase change memory, OTS (Ovonic Threshold Switching, Oliver Threshold Switching) as a new type of gate device can greatly improve the density of memory, it is necessary to propose a new nano-device unit structure to solve the above technical problems.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a phase-change memory cell and a manufacturing method thereof, which can effectively reduce the phase-change region of the phase-change memory cell.

The technical solution adopted by the present invention to solve the technical problem is to provide a phase-change storage unit, comprising:

substrate;

at least one lower electrode, the lower electrode is arranged in the substrate, and the upper contact surface of the lower electrode is exposed outside the substrate and is level with the upper surface of the substrate;

a phase change material layer, the horizontal part of the phase change material layer is connected to the lower electrode, and the phase change material layer is L-shaped;

a filling material, the filling material is arranged above the vertical part of the phase change material layer, and together with the phase change material layer constitutes a phase change memory structure;

an upper electrode, the upper electrode is arranged above the phase change material layer.

The filling material is an isolation material and an OTS material that are filled in sequence.

The filling material is a heating electrode material.

A support structure is also included, the support structure is disposed on the substrate and located at one side of the lower electrode, and the support structure is connected with the phase change memory structure.

When the number of the lower electrodes is plural, an isolation groove is also included, and the isolation groove is used for separating the phase change material layers.

It also includes an insulating layer, the insulating layer is filled in the isolation trench and filled to be flush with the upper surface of the phase change memory structure.

Also included is a cladding layer overlying the phase change memory structure.

The technical solution adopted by the present invention to solve the technical problem is to provide a method for manufacturing a phase-change memory cell, including:

Step (1): at least one lower electrode is embedded in the substrate, and the upper contact surface of the lower electrode is exposed to the outside of the substrate and is level with the upper surface of the substrate;

Step (2): a support structure is arranged on the substrate and on one side of the lower electrode;

Step (3): disposing an L-shaped phase change material layer on the upper contact surface of the lower electrode and on the sidewall surface of the support structure;

Step (4): Etch the phase change material layer along the sidewall direction parallel to the support structure to form an isolation groove, and use an insulating layer to perform etching in the space around the etched phase change material layer and the space around the isolation groove. filling;

Step (5): polishing the insulating layer until the upper surface of the insulating layer, the upper surface of the support structure, and the upper surface of the phase change material layer are flat;

Step (6): performing self-aligned etching on the top of the polished phase change material layer to form a defined hole;

Step (7): placing a filling material in the defined hole, and the filling material and the phase change material layer together constitute a phase change memory structure;

Step (8): disposing an upper electrode on the upper surface of the filling material.

Between the step (3) and the step (4), the method further includes: covering the outer periphery of the phase change material layer with a cladding layer.

The filling material is an isolation material and an OTS material or a heating electrode material filled in sequence.

beneficial effect

Due to the adoption of the above technical solutions, the present invention has the following advantages and positive effects compared with the prior art: the phase change memory cell of the present invention can adopt a 1S1R phase change cell structure formed by a blade-shaped phase change material (ie, set isolation material and OTS material), because the thickness of the 1S1R phase change unit structure is very small and easy to control, the contact surface can be minimized, and the purpose of further reducing the phase change area of the phase change memory cell can be achieved, thereby improving the phase change speed, Reduce the power consumption of the device and increase the density of the phase change memory; the phase change memory cell of the present invention can also use a limited cell structure formed by a blade-shaped phase change material (that is, provided with a heating electrode material), due to the thickness of the limited cell structure. It is very small and easy to control, so that the contact surface can be minimized, and the purpose of further reducing the phase change area of the phase change memory cell can be achieved, thereby increasing the phase change speed and effectively reducing the power consumption of the device.

Description of drawings

FIG. 1 is a schematic diagram of setting a lower electrode in a substrate according to an embodiment of the present invention;

2 is a schematic diagram of setting a support material on a substrate according to an embodiment of the present invention;

3 is a schematic diagram of a support structure provided on a substrate according to an embodiment of the present invention;

4 is a top view of the structure shown in FIG. 3 according to an embodiment of the present invention;

5 is a schematic diagram of disposing a phase change material layer on the surface of the sidewall of the support structure and above the lower electrode according to an embodiment of the present invention;

6 is a schematic diagram of coating a coating layer on the surface of a phase change material layer according to an embodiment of the present invention;

7 is a schematic diagram of opening an isolation groove between support structures according to an embodiment of the present invention;

8 is a schematic diagram of depositing an insulating layer in an isolation trench according to an embodiment of the present invention;

9 is a schematic diagram of planarizing an insulating layer deposited in an isolation trench according to an embodiment of the present invention;

10 is a schematic diagram of etching a defined hole on a phase change material layer according to an embodiment of the present invention;

11 is a schematic diagram of depositing filling materials (isolating materials and OTS materials) in a defined hole according to an embodiment of the present invention;

12 is a schematic diagram of a deposited metal layer configured to form an upper electrode according to an embodiment of the present invention;

13 is a schematic diagram of etching an upper electrode on a deposited metal layer according to an embodiment of the present invention;

14 is a schematic diagram of depositing a filling material (heating electrode material) in a defined hole according to an embodiment of the present invention;

15 is a schematic diagram of another deposited metal layer configured to form an upper electrode according to an embodiment of the present invention;

FIG. 16 is a schematic diagram of etching an upper electrode on another deposited metal layer according to an embodiment of the present invention.

Illustration: 1. Substrate, 2. Lower electrode, 3. Supporting structure, 4. Phase change material layer, 5. Cladding layer, 6. Isolation groove, 7. Insulation layer, 8. Isolation material, 9. OTS material , 10, the upper electrode, 11, the heating electrode material.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Embodiments of the present invention relate to a phase change memory cell comprising:

substrate 1;

at least one lower electrode 2, the lower electrode 2 is disposed in the substrate 1, and the upper contact surface of the lower electrode 2 is exposed to the outside of the substrate 1 and is flat with the upper surface of the substrate 1;

The phase change material layer 4, the horizontal part of the phase change material layer 4 is connected to the lower electrode 2, and the phase change material layer 4 is L-shaped;

Filling material, the filling material is arranged above the vertical part of the phase change material layer 4, and together with the phase change material layer 4 constitutes a phase change memory structure;

The upper electrode 10 is disposed above the phase change material layer 4 .

When the filling material is the isolation material 8 and the OTS material 9 filled in sequence, a 1S1R phase-change cell structure can be constructed; when the filling material is the heating electrode material 11 , a limited cell structure can be constructed.

A support structure 3 is also included, the support structure 3 is disposed on the substrate 1 and located on one side of the lower electrode 2 , and the support structure 3 is connected with the phase change memory structure.

When the number of the lower electrodes 2 is plural, an isolation groove 6 is further included, and the isolation groove 6 is used to separate the phase change material layer 4 .

An insulating layer 7 is also included, and the insulating layer 7 is filled in the isolation trench 6 and filled to be flush with the upper surface of the phase change memory structure.

It also includes a cladding layer 5 covering the phase change memory structure.

Embodiments of the present invention relate to a method for fabricating a phase-change memory cell, including:

Step (1): As shown in FIG. 1 , at least one lower electrode 2 is embedded in the substrate 1 , and the upper contact surfaces of the lower electrodes 2 are all exposed to the outside of the substrate 1 and are flush with the upper surface of the substrate 1 .

In this embodiment, at least four lower electrodes 2 are formed in the substrate 1, and the lower electrodes 2 are distributed in a lattice pattern of at least two rows and at least two columns.

Specifically, the substrate 1 is a conventional semiconductor substrate, and materials such as Si, Ge, and GaN can be used. The method for preparing the lower electrode 2 can be sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition and Any of the atomic layer deposition methods. The material of the lower electrode 2 can be any one of single metal materials W, Pt, Au, Ti, Al, Ag, Cu, Ta and Ni, or an alloy material composed of at least two single metal materials, Or nitrides or oxides of single metal materials.

As an example, the present embodiment adopts chemical vapor deposition (CVD) to prepare the lower electrode 2 made of a single metal material W, and the lower electrode 2 has a diameter of 70 nm and a height of 150 nm. In other embodiments, the lower electrode 2 may also adopt other dimensions.

Step (2): A number of supporting structures 3 are arranged on the substrate 1, and the supporting structures 3 are distributed at intervals between the queues formed by the lower electrodes 2 (ie, the column direction of the lattice distribution is queues).

As an example, as shown in FIG. 2 , a monolithic support structure 3 may be provided on the substrate 1 , and then cut to obtain the pattern shown in FIG. 3 , on the substrate 1 , the lower electrodes 2 form alignments The supporting structures 3 are arranged at intervals therebetween, so that each supporting structure 3 is shared by the lower electrodes 2 on both sides thereof. FIG. 4 shows a top view of the structure shown in FIG. 3 .

Specifically, the support structure 3 is used for forming the phase change material layer 4 (ie, the L-shaped structure). The material of the support structure 3 may be any one or two of insulating nitrides, oxides, oxynitrides, and carbides. In this embodiment, a support structure 3 is prepared on the lower electrode 2 made of W by using a CVD method. The material of the support structure 3 is SiN, the height is 50-100 nm, and the width is 5-100 nm.

Step (3): disposing a phase change material layer 4 on the sidewall surface of the support structure 3 and the upper surface of the substrate 1, wherein the phase change material layer 4 is connected with the upper contact surface of the lower electrode 2 to form a phase change One end of the storage unit is covered with a cladding layer 5 on the periphery of the phase change material layer 4 .

Specifically, the material of the phase change material layer 4 is a chalcogenide compound: it can be any one of GeSb, SiSb, InGST, TaST, TaGST or metal oxides or metal oxides, and the phase change material layer 4 is prepared. The methods are sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition and atomic layer deposition. any of the .

As an example, in this embodiment, a magnetron sputtering method is used to prepare a phase change material layer 4 on a support structure 3 made of SiN using a ^CGe2Sb2Te5 alloy target. The Ar gas pressure was 0.2Pa, the sputtering power was 200W, the substrate temperature was 230°C, and the film thickness was 10nm.

Specifically, a cladding layer 5 is formed around the structure of the phase change material layer 4 (see FIG. 6 for details), and the material of the cladding layer 5 can be any of insulating nitrides, oxides, oxynitrides and carbides A sort of. In this embodiment, the material of the cladding layer 5 is preferably SiN, the height is in the range of 50-200 nm, and the width is in the range of 5-100 nm.

Step (4): The phase change material layer 4 is etched between the queues formed by the lower electrodes 2 without the support structure 3 and along the sidewall direction of the support structure 3 to form isolation trenches 6 and isolation trenches 6 It is used to separate the phase change material layer 4 , and use the insulating layer 7 to fill the space around the etched phase change material layer 4 and the space around the isolation trench 6 .

Specifically, as shown in FIG. 5 , after the phase change material layer 4 is deposited, the phase change material layer 4 covers the sidewalls of the plurality of support structures 3 and the plurality of lower electrodes 2 . In order to isolate the isolation material 8 and the OTS material 9 of each phase change memory cell, or the heating electrode material 11, in this embodiment, a through-hole is formed between the phase change material layers 4 located between two adjacent support structures 3. The isolation groove 6 of the phase change material layer 4 (see FIG. 7 for details), the isolation groove 6 divides the phase change material layer 4 into several separate blade-shaped phase-change material layers 4, the “blade-shaped” phase in this embodiment The phase change material layer 4 means that the thickness of the phase change material layer 4 is very thin.

As shown in FIG. 8 , after the isolation trench 6 is formed, an insulating layer 7 is further deposited in the isolation trench 6 and planarized. The purpose of depositing and planarizing the insulating layer 7 is to further form the upper electrode 10 later.

It is worth mentioning that the cross section of each phase change material layer 4 which is separated by the isolation groove 6 and in contact with the lower electrode 2 has an L-shaped blade-like structure.

As an example, in this embodiment, exposure and reactive ion etching are used to form separation grooves 6 to separate the CGe2Sb2Te5 films between phase change material layers 4 to form L-shaped blade-shaped phase-change material layers 4. The L-shaped blade-shaped phase change material layers 4 The thickness range of the change material layer 4 is 1 to 10 nanometers, preferably 10 nanometers; the height range is 10 to 500 nanometers, preferably 50 nanometers; the bottom width of the L-shaped blade-shaped phase change material layer 4 structure is in the range of 5 to 50 nanometers .

Step (5): polishing the insulating layer 7 until the upper surface of the insulating layer 7, the upper surface of the support structure 3, and the upper surface of the phase change material layer 4 are flat, even if the upper surface of the phase change material layer 4 is exposed (see details for details). Figure 9).

Specifically, the blade-shaped phase change material and its coating layer 5 are polished by a mechanical polishing process, so that one end of the phase change material layer 4 is exposed.

Step (6): performing self-alignment etching on the polished phase change material layer 4 to form a defined hole.

Specifically, the phase change material layer 4 is etched, and a defined hole of a certain depth is etched above the phase change material layer 4, and the height of the defined hole is 10-100 nanometers in height, as shown in FIG. 10 for details. .

Step (7): placing a filling material in the defined hole to form a phase change memory structure.

(1) When the filling material is the isolation material 8 and the OTS material 9 filled in sequence (see FIG. 11 for details), the isolation layer material 8 is one of carbon, Ti or tungsten metal and oxides and nitrides thereof or A mixture thereof; the OTS material 9 is AsTeGeSiN, AsGeTeSi, GeTe, GeSe and the like. The methods for preparing the isolation material 8 and the OTS material 9 are sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic Either vapor deposition method or atomic layer deposition method.

(2) When the filling material is the heating electrode material 11, the heating electrode layer material 8 is any one of the single metal material W, Ti or the alloy material WN, TiN, TaN, or an alloy material composed thereof, or The oxide material of the electrode single metal material. The method for preparing the heating electrode layer material 8 is sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition and Atomic Layer Deposition. Regarding the phase-change memory cell composed of the heating electrode material 11, please refer to FIG. 14 to FIG. 16 in turn.

Step (8): performing a polishing process on the filling material to form a flat upper surface.

Specifically, the OTS material 9 is polished by a mechanical polishing process to expose the upper surface.

Step (9): disposing the upper electrode 10 on the flat upper surface of the filling material, see FIG. 12 for details.

Step (10): disposing the upper electrode 10 on the upper surface of the filling material, etching the upper electrode 10 into a strip shape (see FIG. 13 for details), and the etching direction is the same as the direction in which the support structure 3 is arranged.

Specifically, the material of the upper electrode 10 is any one of single metal materials W, Pt, Au, Ti, Al, Ag, Cu and Ni, or an alloy material composed of a combination thereof, or the electrode single metal material of nitrides or oxides. The methods for preparing the upper electrode 10 are sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition and atomic vapor deposition Any of the layer deposition methods.

As an example, the magnetron sputtering method is used to prepare the upper electrode 10 on the phase change material layer 4, and the process parameters are: the background gas pressure is 1×10 ^-5 Pa, the gas pressure during sputtering is 0.2 Pa, and the gas flow rate of Ar/N2 The ratio was 1:1, the sputtering power was 300 W, the substrate temperature was 25 °C, and the electrode height on the TiN was 50 nm.

Subsequently, the upper electrode 10 and the lower electrode 2 can be further extracted by standard semiconductor process and integrated with the control switch, driving circuit and peripheral circuit of the device unit, thereby preparing a complete phase change memory device unit. The material of the extraction electrode may be any one of W, Pt, Au, Ti, Al, Ag, Cu and Ni, or a combination thereof to form an alloy material.

The manufacturing method of the phase-change memory cell of the present invention utilizes a support structure 3 to form the blade-shaped phase-change material layer 4, and makes the blade-shaped phase-change material layer 4 cross contact with the lower electrode 2 at a certain angle. The thickness of the change material layer 4 minimizes the contact surface, that is, the thinner the thickness of the phase change material layer 4, the smaller the contact area with the lower electrode 2, thereby achieving the purpose of reducing the phase change area of the device unit. Self-aligned etched defined holes, filled the isolation layer 8 and OTS material 9 in sequence in the defined holes to achieve 1S1R structure, or filled the defined holes with heating electrode material 11 to achieve a defined structure, thereby greatly reducing the power consumption consumption and increase storage density.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

1. A phase-change storage unit, characterized in that, comprising: substrate (1); At least one lower electrode (2), the lower electrode (2) being arranged in the substrate (1), the upper contact surface of the lower electrode (2) being exposed outside the substrate (1) and being connected to the substrate (1) the top surface is flat; a phase-change material layer (4), wherein the horizontal portion of the phase-change material layer (4) is connected to the lower electrode (2), and the phase-change material layer (4) is L-shaped; Filling material, the filling material is arranged above the vertical part of the phase change material layer (4), and together with the phase change material layer (4) constitutes a phase change memory structure; An upper electrode (10) is provided above the phase change material layer (4). 2. The phase change memory cell according to claim 1, wherein the filling material is an isolation material (8) and an OTS material (9) filled in sequence. 3. The phase change memory cell according to claim 1, wherein the filling material is a heating electrode material (11). 4. The phase change memory cell according to claim 1, characterized in that, further comprising a support structure (3), the support structure (3) being arranged on the substrate (1) and located at the bottom of the lower electrode (2) On one side, the support structure (3) is connected with the phase change memory structure. 5. The phase change memory cell according to claim 1, characterized in that, when the number of the lower electrodes (2) is plural, it further comprises an isolation groove (6), and the isolation groove (6) is used to separate the The phase change material layer (4) is separated. 6 . The phase change memory cell according to claim 5 , further comprising an insulating layer ( 7 ), the insulating layer ( 7 ) is filled in the isolation trench ( 6 ), and is filled to the same extent as the phase change memory structure. 7 . The top surface is flush. 7. The phase change memory cell according to claim 1, further comprising a cladding layer (5), the cladding layer (5) covering the phase change memory structure. 8. A method for fabricating a phase change memory cell, comprising: Step (1): at least one lower electrode (2) is embedded in the substrate (1), and the upper contact surface of the lower electrode (2) is exposed to the outside of the substrate (1) and is level with the upper surface of the substrate (1) ; Step (2): disposing a support structure (3) on the substrate (1) and at one side of the lower electrode (2); Step (3): providing an L-shaped phase change material layer (4) on the upper contact surface of the lower electrode (2) and on the sidewall surface of the support structure (3); Step (4): The phase change material layer (4) is etched in a direction parallel to the sidewall of the support structure (3) to form an isolation groove (6), and an insulating layer (7) is used in the etched The space around the phase change material layer (4) and the space around the isolation groove (6) are filled; Step (5): polishing the insulating layer (7) until the upper surface of the insulating layer (7), the upper surface of the support structure (3), and the upper surface of the phase change material layer (4) are flat; Step (6): performing self-aligned etching on the polished phase change material layer (4) to form a defined hole; Step (7): placing a filling material in the defined hole, and the filling material and the phase change material layer (4) together constitute a phase change memory structure; Step (8): disposing an upper electrode (10) on the upper surface of the filling material. 9 . The method for fabricating a phase change memory cell according to claim 8 , wherein between the steps (3) and (4), the method further comprises: covering the outer periphery of the phase change material layer (4) with a bag of Cladding (5). 10 . The method for manufacturing a phase change memory cell according to claim 7 , wherein the filling material is an isolation material ( 8 ) and an OTS material ( 9 ) or a heating electrode material ( 11 ) filled in sequence. 11 .

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