Method of manufacturing phase change memory and phase change memory

A method of manufacturing a phase change memory includes: forming a stacked structure including a conductive layer, a lower electrode layer over the conductive layer, an upper electrode layer, a phase change material between the lower and upper electrode layers, and a selector material between the conductive layer and the lower electrode layer; etching the upper electrode layer to form an upper electrode wire; etching the phase change material according to the upper electrode wire to form a phase change material layer and expose a portion of the lower electrode layer, wherein the phase change material layer has an exposed side surface; after etching the phase change material, performing a nitridizing treatment on the side surface of the phase change material layer to form a nitridized phase change material layer covering the same; and etching the lower electrode layer, the selector material and the conductive layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to China Application Serial Number 202010477856.3, filed May 29, 2020, which is herein incorporated by reference.

BACKGROUND

Field of Invention

The present invention relates to a method of manufacturing a phase change memory and a phase change memory.

Description of Related Art

Electronic products (e.g., mobile phones, tablets, and digital cameras) often have memory elements that store data. Conventional memory elements can store information through storage nodes of memory cells. Among them, the phase change memory uses resistance states (e.g., high resistance and low resistance) of the memory element to store information. The memory element may have a material that can be switched between different phase states (e.g., a crystalline phase and an amorphous phase). The different phase states enable the memory cell to have different resistance states for representing different values of stored data.

Generally, the phase change memory includes an upper electrode, a lower electrode, and a phase change material layer between the upper electrode and the lower electrode. Lithography and etching processes are commonly used to manufacture the phase change memory.

SUMMARY

The present invention provides a method of manufacturing a phase change memory, which includes: forming a stacked structure, the stacked structure including a conductive layer; a lower electrode layer disposed over the conductive layer; an upper electrode layer disposed over the lower electrode layer; a phase change material disposed between the lower electrode layer and the upper electrode layer; and a selector material disposed between the conductive layer and the lower electrode layer; etching the upper electrode layer according to a first mask to form an upper electrode wire; etching the phase change material according to the upper electrode wire to form a phase change material layer beneath the upper electrode wire and expose a portion of the lower electrode layer, in which the phase change material layer has an exposed side surface; after etching the phase change material, performing a nitridizing treatment on the side surface of the phase change material layer to form a nitridized phase change material layer covering the side surface of the phase change material layer; and etching the lower electrode layer, the selector material and the conductive layer according to the phase change material layer and the nitridized phase change material layer to form a lower electrode wire, a selector material layer and a conductive wire therebeneath.

In some embodiments, performing the nitridizing treatment on the side surface of the phase change material layer comprises performing the nitridizing treatment using a nitrogen-containing gas plasma.

In some embodiments, the nitrogen-containing gas plasma comprises nitrogen plasma, ammonia plasma, or a combination thereof.

In some embodiments, etching the phase change material according to the upper electrode wire comprises etching the phase change material using inductively coupled plasma (ICP), plasma ion sputtering or a combination thereof.

In some embodiments, the method further includes: before performing the nitridizing treatment on the side surface of the phase change material layer, side-etching the side surface of the phase change material layer, so that a width of the phase change material layer is smaller than a width of the upper electrode wire.

In some embodiments, side-etching the side surface of the phase change material layer comprises using an etchant.

In some embodiments, the method further includes: forming an isolation material layer laterally adjacent to the upper electrode wire, the phase change material layer, the nitridized phase change material layer, the lower electrode wire and the conductive wire; etching the upper electrode wire according to a second mask to form a plurality of upper electrode units; etching the phase change material layer according to the upper electrode units to form a plurality of phase change units beneath the upper electrode units, respectively; and etching the lower electrode wire according to the phase change units to form a plurality of lower electrode units beneath the phase change units, respectively.

In some embodiments, each of the phase change units has an exposed side surface, and the method further includes: after etching the phase change material layer, performing another nitridizing treatment on the side surface of each of the phase change units to form another nitridized phase change material layer covering the side surface of each of the phase change units.

In some embodiments, performing the other nitridizing treatment on the side surface of each of the phase change units comprises performing the other nitridizing treatment using a nitrogen-containing gas plasma.

In some embodiments, the method further includes: before performing the other nitridation treatment on the side surface of each of the phase change units, side-etching the side surface of each of the phase change units, so that a width of the phase change unit is smaller than a width of the upper electrode unit.

The present invention also provides a phase change memory, which includes a lower electrode unit, an upper electrode unit, a phase change unit, a nitridized phase change material layer and a selector. The upper electrode unit is disposed over the lower electrode unit. The phase change unit is disposed between the lower electrode unit and the upper electrode unit. The nitridized phase change material layer covers a side surface of the phase change unit. The selector is disposed beneath the lower electrode unit.

In some embodiments, a sum of a width of the phase change unit and a width of the nitridized phase change material layer is greater than a width of the upper electrode unit.

In some embodiments, a width of the phase change unit is smaller than a width of the upper electrode unit.

In some embodiments, a sum of a width of the phase change unit and a width of the nitridized phase change material layer is less than or equal to a width of the upper electrode unit.

It should be understood that the above general description and the following detailed description are exemplary and are intended to provide a further explanation of the claimed invention.

DETAILED DESCRIPTION

In order that the present invention is described in detail and completeness, implementation aspects and specific embodiments of the present invention with illustrative description are presented, but it is not the only form for implementation or use of the specific embodiments of the present invention. The embodiments disclosed herein may be combined or substituted with each other in an advantageous manner, and other embodiments may be added to an embodiment without further description. In the following description, numerous specific details will be described in detail in order to enable the reader to fully understand the following embodiments. However, the embodiments of the present invention may be practiced without these specific details.

Further, spatially relative terms, such as “beneath,” “over,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as shown in the figures. The true meaning of the spatially relative terms includes other orientations. For example, when the figure is flipped up and down by 180 degrees, the relationship between one component and another component may change from “beneath” to “over.” The spatially relative descriptions used herein should be interpreted the same.

As described in the section of “Description of Related Art”, the lithography and etching processes are commonly used to manufacture the phase change memory. However, the phase change material layer in the phase change memory is very vulnerable to subsequent etching processes and thus is seriously damaged. Therefore, how to prevent the phase change material layer from being seriously damaged during the subsequent etching processes has become an important issue in this technical field.

Accordingly, the present invention provides a method of manufacturing a phase change memory by forming a nitridized phase change material layer on an exposed surface of the phase change material layer that can protect the phase change material layer to prevent the phase change material layer from being seriously damaged during the subsequent etching processes. Various embodiments of the method of manufacturing the phase change memory will be described in detail below.

FIGS. 1, 2, 3, 4, 5A-5B, 6A-6B, 7, 8, 9, 10are schematic diagrams of a method of manufacturing a phase change memory at various stages according to some embodiments of the present invention.

As shown inFIG. 1, a stacked structure100is formed, which includes a conductive layer120, a lower electrode layer140, an upper electrode layer160, and a phase change material150. In some embodiments, the stacked structure100is formed over a substrate110. In some embodiments, the substrate110is a semiconductor substrate, such as a silicon substrate, but is not limited thereto, and other suitable materials may be used as the substrate110, such as ceramic materials, organic materials, or glass materials.

In some embodiments, a material of the conductive layer120includes metallic materials, such as titanium, tantalum, tungsten, aluminum, copper, molybdenum, platinum, titanium nitride, tantalum nitride, tantalum carbide, tantalum silicon nitride, tungsten nitride, molybdenum nitride, molybdenum oxynitride, ruthenium oxide, titanium aluminum, titanium aluminum nitride, tantalum carbonitride, other suitable materials or a combination thereof. In some embodiments, the conductive layer120may be subsequently patterned to form a plurality of conductive wires parallel to each other, and these conductive wires may act as word lines or bit lines.

In some embodiments, the lower electrode layer140and the upper electrode layer160include metallic materials, such as tungsten, titanium, titanium nitride, tantalum nitride, aluminum titanium nitride, aluminum tantalum nitride, or a combination thereof.

In some embodiments, the stacked structure100further includes a selector material130disposed between the conductive layer120and the lower electrode layer140. In some embodiments, the selector material130includes a semiconductor material, such as silicon. In some embodiments, the selector material130includes a PN diode.

In some embodiments, the conductive layer120, the selector material130, the lower electrode layer140, the phase change material150, and the upper electrode layer160are blanket formed over the substrate110in sequence, as shown inFIG. 1.

Subsequently, as shown inFIGS. 1 and 2, a first mask172is formed over the upper electrode layer160of the stacked structure100, and the upper electrode layer160is then etched according to the first mask172to form a plurality of upper electrode wires162. In some embodiments, the first mask172is, for example, a photoresist (PR) or a hard mask (HM). In some embodiments, the process of etching the upper electrode layer160is, for example, a dry etching process or a wet etching process. In some embodiments, the dry etching process for etching the upper electrode layer160is, for example, a plasma etching process using a gas including Cl2, BCl3, SF6, or any combination thereof. In some embodiments, the wet etching process for etching the upper electrode layer160is, for example, a wet etching process using an etching solution including phosphoric acid, nitric acid, and acetic acid.

Next, as shown inFIGS. 2 and 3, the phase change material150is etched according to the upper electrode wire162to form a phase change material layer152beneath the upper electrode wire162and expose a portion of the lower electrode layer140, in which the phase change material layer152has an exposed side surface152a. In some embodiments, etching the phase change material150includes etching the phase change material150using inductively coupled plasma (ICP), plasma ion sputtering, or a combination thereof. In some embodiments, chlorine-based (Cl-based), fluorine-based (F-based) or bromine-based (Br-based) plasma and gas such as helium or argon are used in the inductively coupled plasma etching process.

Next, as shown inFIGS. 3 and 4, a nitridizing treatment is performed on the side surface152aof the phase change material layer152to form a nitridized phase change material layer182covering the side surface152aof the phase change material layer152. The nitridized phase change material layer182can effectively protect the phase change material layer152from damage during subsequent etching processes. In some embodiments, performing the nitridizing treatment on the side surface152aof the phase change material layer152includes performing the nitridizing treatment on the side surface152aof the phase change material layer152using a nitrogen-containing gas plasma. In some embodiments, the nitrogen-containing gas plasma includes nitrogen plasma, ammonia plasma, or a combination thereof. In some embodiments, a process temperature of the nitridizing treatment is in a range of from 200° C. to 400° C. In some embodiments, the nitridized phase change material layer182includes germanium antimony tellurium nitride, nitrogen-doped germanium antimony tellurium, antimony tellurium nitride, nitrogen-doped antimony tellurium, germanium antimony nitride, nitrogen-doped germanium antimony or a combination thereof.

Next, as shown inFIGS. 4 and 5A, the lower electrode layer140, the selector material130, and the conductive layer120are etched according to the phase change material layer152and the nitridized phase change material layer182to form a lower electrode wire142, a selector material layer132and a conductive wire122therebeneath. In some embodiments, the lower electrode layer140, the selector material130, and the conductive layer120are etched according to the phase change material layer152and the nitridized phase change material layer182.

In some embodiments, the process for etching the lower electrode layer140is, for example, a dry etching process or a wet etching process. In some embodiments, the dry etching process for etching the lower electrode layer140is, for example, a plasma etching process using a gas including Cl2, BCl3, SF6, or any combination thereof. In some embodiments, the wet etching process for etching the lower electrode layer140is, for example, a wet etching process using an etching solution including phosphoric acid, nitric acid, and acetic acid.

In some embodiments, the process of etching the selector material130to form the selector material layer132is to manufacture a PN diode with a vertical profile. Manufacturing the PN diode with the vertical profile is a known technique in this technical field, so the manufacturing process thereof is not repeated here.

In some embodiments, the process of etching the conductive layer120is, for example, a dry etching process or a wet etching process. In some embodiments, the dry etching process for etching the conductive layer120is, for example, a plasma etching process using a gas including Cl2, BCl3, SF6, or any combination thereof. In some embodiments, the wet etching process for etching the conductive layer120is, for example, a wet etching process using an etching solution including phosphoric acid, nitric acid, and acetic acid.

In some embodiments, certain chemicals used in the processes of etching the lower electrode layer140, the selector material130, and the conductive layer120may cause severe damage to the phase change material layer152. For example, the etching gas or etching liquid used in the subsequent etching of the lower electrode layer140, the selector material130, and the conductive layer120will damage the surface of the phase change material layer152and cause defects, so that the structural states of the crystalline phase and the amorphous phase of the phase change material layer152and the resistance values thereof have been different from those before the damage. Therefore, although the phase change material layer152can still be switched between the crystalline phase and the amorphous phase, the change of resistance value before and after the conversion will deviate from the originally predetermined change of resistance value. However, in the present invention, the nitridized phase change material layer182formed covering the side surface152aof the phase change material layer152can protect the phase change material layer152from these chemicals during subsequent etching processes and ensure that the resistance states (e.g., high resistance and low resistance) of the phase change material layer152used to store information are not affected, thereby improving the performance of the memory element.

FIG. 5Ais a cross-sectional view taken along line X-X′ ofFIG. 5Baccording to some embodiments of the present invention. In some embodiments, as shown inFIG. 5B, the conductive wire122, the selector material layer132, the lower electrode wire142, the phase change material layer152, and the upper electrode wire162extend along the Y direction. As shown inFIGS. 5A and 5B, the conductive wire122, the selector material layer132, the lower electrode wire142, the phase change material layer152, and the upper electrode wire162constitute a stacked structure102.

Subsequently, as shown inFIGS. 5A and 6A(orFIGS. 5B and 6B), an isolation material layer190is formed laterally adjacent to the upper electrode wire162, the phase change material layer152, the nitridized phase change material layer182, the lower electrode wire142, the selector material layer132and the conductive wire122. More specifically, in some embodiments, an isolation material is deposited over the first mask172and the stacked structure102and between the stacked structures102shown inFIG. 5B, and a polishing process (e.g., a chemical mechanical polishing process) is performed to remove the first mask172and excess isolation material, so that a top surface of the isolation material layer190after polishing is coplanar with a top surface of the upper electrode wire162, as shown inFIG. 6B. In some embodiments, the isolation material includes oxide, nitride, oxynitride, or a combination thereof, such as silicon oxide, silicon nitride, silicon oxynitride, or a combination thereof. In some embodiments, a chemical vapor deposition process may be used to deposit the isolation material.

FIG. 6Ais a cross-sectional view taken along line X-X′ ofFIG. 6Baccording to some embodiments of the present invention. In some embodiments, as shown inFIG. 6B, the isolation material layer190is filled between the two stacked structures102.

FIG. 7is a cross-sectional view taken along line Y-Y′ ofFIG. 6Baccording to some embodiments of the present invention. As shown inFIGS. 6B and 7, after the isolation material layer190is formed, a second mask174is formed over the upper electrode wire162of the stacked structure102. In some embodiments, the second mask174is, for example, a photoresist or a hard mask.

Next, as shown inFIGS. 7 and 8, the upper electrode wire162is etched according to the second mask174to form a plurality of upper electrode units164. In some embodiments, the process of etching the upper electrode wire162may be the same as the process of etching the upper electrode layer160, so description thereof is not repeated here.

Subsequently, as shown inFIGS. 8 and 9, the phase change material layer152is etched according to the upper electrode units164to form a plurality of phase change units154beneath the upper electrode units164, respectively. In some embodiments, etching the phase change material layer152includes etching the phase change material layer152using inductively coupled plasma, plasma ion sputtering, or a combination thereof. These processes can also etch the nitridized phase change material layer182(not shown inFIG. 8, refer to the nitridized phase change material layer182inFIG. 6B) not covered by the second mask174and the upper electrode unit164. In addition, the inventor found that the etching rate of the phase change material layer152is about equal to that of the nitridized phase change material layer182. In some embodiments, as shown inFIGS. 8 and 9, the phase change unit154formed after the phase change material layer152and the nitridized phase change material layer182are etched according to the upper electrode unit164has a plurality of exposed side surfaces154a.

As shown inFIGS. 9 and 10, another nitridizing treatment is performed on the side surface154aof each of the phase change units154to form another nitridized phase change material layer184covering the side surface154aof each of the phase change units154. In some embodiments, the nitridizing treatment includes using a nitrogen-containing gas plasma, which includes nitrogen plasma, ammonia plasma, or a combination thereof. In some embodiments, a process temperature of the nitridizing treatment is in a range of from 200° C. to 400° C. In some embodiments, the nitridized phase change material layer184includes germanium antimony tellurium nitride, nitrogen-doped germanium antimony tellurium, antimony tellurium nitride, nitrogen-doped antimony tellurium, germanium antimony nitride, nitrogen-doped germanium antimony or a combination thereof.

Next, still referring toFIGS. 9 and 10, after the nitridized phase change material layer184is formed, the lower electrode wire142and the selector material layer132are etched according to the plurality of phase change units154to form a plurality of lower electrodes units144and a plurality of selectors134therebeneath. In some embodiments, the lower electrode wire142and the selector material layer132are etched according to the phase change units154and the nitridized phase change material layer184. In some embodiments, the processes of etching the lower electrode wire142and the selector material layer132may be the same as the processes of etching the lower electrode layer140and the selector material130, so description thereof are not repeated here.

In some embodiments, certain chemicals used in the process of etching the lower electrode wire142and the selector material layer132may cause severe damage to the phase change unit154. For example, the etching gas or etching liquid used in the subsequent etching of the lower electrode wire142and the selector material layer132will damage the surface of the phase change unit154and cause defects, so that the structural states of the crystalline phase and the amorphous phase of the phase change unit154and the resistance values thereof have been different from those before the damage. Therefore, although the phase change unit154can still be switched between the crystalline phase and the amorphous phase, the change of resistance value before and after the conversion will deviate from the originally predetermined change of resistance value. However, in the present invention, the nitridized phase change material layer184formed covering the side surface154aof the phase change unit154can protect the phase change unit154from these chemicals during subsequent etching processes and ensure that the resistance states (e.g., high resistance and low resistance) of the phase change unit154used to store information are not affected, thereby improving the performance of the memory element.

In some embodiments, the selector134, the lower electrode unit144, the phase change unit154, and the upper electrode unit164constitute a memory cell104. In some embodiments, an another conductive wire is formed over the memory cell104. Viewed from above, the other conductive wire and the conductive wire122are perpendicularly crossed with each other, and the other conductive wire and the conductive wire122can as act as a word line and a bit line, respectively.

FIG. 11is a schematic diagram of a method of manufacturing a phase change memory at a certain stage according to some embodiments of the present invention. In addition to the above operations, the method of manufacturing the phase change memory may optionally further include the operation shown inFIG. 11, which are described in detail below. As shown inFIGS. 3 and 11, before the nitridizing treatment is performed on the side surface152aof the phase change material layer152, the side surface152amay be side-etched, and the nitridizing treatment is then performed on the side surface152ato form a nitridized phase change material layer182covering the side surface152aof the phase change material layer152. The side-etching makes the phase change material layer152shrink inward in the lateral direction; preferably, it further makes a sum of a width of the phase change material layer152and a width of the nitridized phase change material layer182does not protrude outward beyond the width of the upper electrode wire162in the lateral X direction (as shown inFIG. 11), so the nitridized phase change material layer182does not protrude outward in the lateral direction. See the difference betweenFIG. 4without side-etching andFIG. 11with side-etching. After the side-etching, the width of the phase change material layer152becomes narrower (as shown inFIG. 11), and the sum of the width of the phase change material layer152and the width of the nitridized phase change material layer182does not protrude outward beyond the width of the upper electrode wire162in the lateral X direction.

FIG. 12is a schematic diagram of a method of manufacturing a phase change memory at a certain stage according to some embodiments of the present invention. Similarly, as shown inFIG. 9, before the nitridizing treatment is performed on the side surface154aof each of the phase change units154, the side surface154amay also be side-etched, and the nitridizing treatment is then performed on the side surface154ato form another nitridized phase change material layer184covering the side surface154aof each of the phase change units154, as shown inFIG. 12. The side-etching makes the phase change unit154shrink inward in the lateral direction; preferably, it further makes a sum of a width of the phase change unit154and a width of the nitridized phase change material layer184does not protrude outward beyond the width of the upper electrode unit164in the lateral Y direction, so the nitridized phase change material layer184does not protrude outward in the lateral direction.

After the two side-etching processes, the widths of the phase change unit154in the X direction and the Y direction both become narrower and smaller than the width of the upper electrode unit164; preferably, the sum of the width of the phase change unit154and the width of the nitridized phase change material layer182/184does not protrude outward beyond the width of the upper electrode unit164in the lateral X/Y direction. Therefore, the distance between the two adjacent memory cells104can be further reduced, which helps to increase density of the memory cells104formed over the substrate110. In some embodiments, side-etching the side surface152aand side-etching the side surface154acan be achieved by a wet etching process using an etching solution.

The present invention also provides a phase change memory. Referring toFIG. 10, the phase change memory104includes a lower electrode unit144, an upper electrode unit164, a phase change unit154, a nitridized phase change material layer184, and a selector134.

The upper electrode unit164is disposed over the lower electrode unit144. The upper electrode unit164is substantially aligned with or aligned with the lower electrode unit144.

The phase change unit154is disposed between the lower electrode unit144and the upper electrode unit164. The phase change unit154is substantially aligned with or aligned with the lower electrode unit144and the upper electrode unit164.

The selector134is disposed beneath the lower electrode unit144. The selector134is substantially aligned or aligned with the lower electrode unit144. The selector134is disposed between the conductive wire122and the lower electrode unit144.

The nitridized phase change material layer184covers a side surface154aof the phase change unit154. In some embodiments, referring toFIGS. 9 and 10, from a stereoscopic perspective, the nitridized phase change material layer184covers four side surfaces154a (i.e., all side surfaces154a) of the phase change unit154.

In some embodiments, as shown inFIG. 10, a width of the phase change unit154is substantially the same as or the same as a width of the upper electrode unit164. In some embodiments, as shown inFIG. 10, a sum of the width of the phase change unit154and a width of the nitridized phase change material layer184is greater than the width of the upper electrode unit164.

In some embodiments, as shown inFIG. 12, a width of the phase change unit154is smaller than a width of the upper electrode unit164. In some embodiments, as shown inFIG. 12, a sum of the width of the phase change unit154and a width of the nitridized phase change material layer184is less than or equal to the width of the upper electrode unit164.

Although embodiments of the present invention have been described in considerable detail, other embodiments are possible. Therefore, the spirit and scope of the claim scope of the present invention should not be limited to the description of the embodiments contained herein.

It is obvious to those skilled in the art that various modifications and changes can be made to the structure of the present invention without departing from the scope or spirit of the present invention. In view of the foregoing, the present invention is intended to cover the modifications and changes of the present invention as long as they fall within the claim scope of the present invention.