Phase change material switch and manufacturing method

Abstract

Provided is a phase change material switch comprising a substrate, a phase change film formed above the substrate, first and second electrodes formed apart from each other on the phase change film, and a heater formed above at least a portion of a channel region between the first and second electrodes in the phase change film.

Description

Phase change material switch and method of manufacture

[0001] The present invention relates to phase change material switches and methods of manufacture.

[0002] Patent document 1 states that "the phase-change memory cell comprises a substrate 101, a chalcogenide material layer 113, and an upper electrode layer 114 (a first electrode layer 114a and a second electrode layer 114b) sequentially deposited on the substrate 101" (paragraph 0012).

[0003] Patent Document 2 states, "Next, as shown in FIG. 5(c), a phase change film 33 made of GeSeTe is deposited. ... Next, as shown in FIG. 5(d), SiO ２ The document states that "an insulating film 34 made of W / TiN is deposited by CVD, and the insulating film 34 and the phase change film 33 are selectively etched. ...Next, as shown in FIG. 5(e), a gate metal (resistance heater) 35 made of W / TiN is deposited on the insulating film 34, and this is etched by lithography to form a thin wire electrode." (Paragraphs 0032 to 0034) [Prior art documents] [Patent documents] [Patent document 1] International Publication No. 2010 / 073904 [Patent document 2] Japanese Patent Application Laid-Open No. 2006-173555 General disclosure

[0004] In a first aspect of the present invention, there is provided a phase change material switch comprising a substrate, a phase change film formed above the substrate, first and second electrodes formed spaced apart from each other on the phase change film, and a heater formed above at least a portion of a channel region in the phase change film between the first and second electrodes.

[0005] The phase change material switch may include a first insulating film between the phase change film and the heater.

[0006] Any of the phase change material switches described above may include a first anti-oxidation film between the phase change film and the first insulating film.

[0007] Any of the above phase change material switches may include a second anti-oxidation film between the substrate and the phase change film.

[0008] In any of the above phase change material switches, the heater and the first and second electrodes may be formed from the same electrothermal material.

[0009] In any of the above phase change material switches, the first and second electrodes may be formed of a conductive material having a higher electrical conductivity than the heater.

[0010] Any of the phase change material switches described above may include first and second heater electrodes formed integrally with the heater at both ends of the heater, and each of the first and second heater electrodes may have a wiring width larger than that of the heater.

[0011] In a second aspect of the present invention, there is provided a method for manufacturing a phase change material switch, comprising forming a phase change film above a substrate, forming first and second electrodes spaced apart from each other on the phase change film, and forming a heater above at least a portion of a channel region in the phase change film between the first and second electrodes.

[0012] The manufacturing method may include forming a first insulating film above the phase change film, and the heater may be formed above the first insulating film.

[0013] In any of the above manufacturing methods, both the formation of the phase change film and the formation of the first insulating film may be carried out while maintaining a vacuum.

[0014] Any of the above manufacturing methods may include forming a first insulating film above the phase change film, and then forming an electric heating material film covering the phase change film and the first insulating film, and forming the first and second electrodes and the heater by cutting between the first electrode, the second electrode, and the heater in the electric heating material film.

[0015] The above summary of the invention does not list all of the features of the present invention, and subcombinations of these features may also be inventions.

[0016] 1 shows a cross-sectional view of a phase change material switch 100 according to the present embodiment; FIG. 2 shows a plan view of the phase change material switch 100 according to the present embodiment; FIG. 3 shows a state in which a second insulating film 170 is formed on a substrate 110; FIG. 4 shows a state in which a phase change film 120 and a first insulating film 160 are formed on the second insulating film 170; FIG. 5 shows a state in which a portion of the first insulating film 160 has been removed; FIG. 6 shows a state in which an electrothermal material film 600 covering the phase change film 120 and the first insulating film 160 has been formed; FIG. 7 shows a state in which a first electrode 130, a second electrode 140, and a heater 150 have been formed; and FIG. 8 shows a cross-sectional view of a phase change material switch 800 according to a modified example of the present embodiment.

[0017] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention as claimed. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0018] FIG. 1 shows a cross-sectional view of a phase change material switch 100 according to this embodiment. FIG. 2 shows a plan view of the phase change material switch 100 according to this embodiment. The phase change material switch 100 has a channel of a phase change film 120 between a first electrode 130 and a second electrode 140, and changes the phase state of the phase change film 120 by heating with a heater 150 formed above the channel. This allows the phase change material switch 100 to switch between an ON state in which the first electrode 130 and the second electrode 140 are electrically connected and an OFF state in which they are electrically disconnected, depending on the phase state of the phase change film 120.

[0019] The phase change material switch 100 comprises a substrate 110, a phase change film 120, a first electrode 130, a second electrode 140, a heater 150, a first heater electrode 152, a second heater electrode 154, a first insulating film 160, a second insulating film 170, and a protective film 180.

[0020] Substrate 110 has a surface (upper surface in the drawing) on ​​which each film of phase change material switch 100 is formed. Substrate 110 may be made of an insulating material or a material with relatively high electrical resistance, such as Si (silicon), SiO ２ (silicon dioxide), or other materials. Note that multiple phase change material switches 100 may be formed using the same substrate 110.

[0021] The phase change film 120 is formed above the substrate 110. Here, "formed above" means that the phase change film 120 is formed in a region above the substrate 110, and that the substrate 110 and the phase change film 120 may be in direct contact with each other, or another layer may be included between the substrate 110 and the phase change film 120. The phase change film 120 is made of a material such as GeTe (germanium telluride), Sb ２ Te ３ The phase-change film 120 may be formed of antimony telluride (antimony telluride) or other phase-change materials. The phase-change film 120 can reversibly change between an amorphous phase with high resistance and low refractive index and a crystalline phase with low resistance and high refractive index by undergoing a heating and cooling cycle. The phase-change film 120 according to this embodiment may change from the crystalline phase to the amorphous phase by being heated to a high temperature above its melting point and then rapidly cooled, and may change from the amorphous phase to the crystalline phase by being subjected to a thermal annealing treatment at a relatively low temperature above its crystallization temperature. For example, if the phase-change film 120 is a GeTe film, it may change from the crystalline phase to the amorphous phase by being heated to 700°C and then rapidly cooled, and then change from the amorphous phase to the crystalline phase by being subjected to a thermal annealing treatment at 200°C. As an example, the phase-change film 120 may have a thickness of approximately 100 nm.

[0022] The first electrode 130 and the second electrode 140 are formed on the phase change film 120 at a distance from each other. Here, "on" indicates that the first electrode 130 and the second electrode 140 are in direct contact with the phase change film 120. The first electrode 130 and the second electrode 140 are electrically connected to the phase change film 120. The first electrode 130 and the second electrode 140 are formed of a conductive material.

[0023] First electrode 130 and second electrode 140 may be formed of gold (Au), titanium (Ti / Au) which is an alloy of Au and titanium (Ti), or other conductive materials. In this case, first electrode 130 and second electrode 140 may be formed of a conductive material with higher electrical conductivity than heater 150 (described later). This allows the on-resistance of phase-change material switch 100 to be reduced.

[0024] The first electrode 130 and the second electrode 140 may be formed of W (tungsten) or other electrothermal materials. When the first electrode 130 and the second electrode 140 are formed of an electrothermal material, the first electrode 130 and the second electrode 140 may have a wiring width perpendicular to the direction of current flow that is larger than that of the heater 150. This can reduce the resistance of the first electrode 130 and the second electrode 140, and prevent the first electrode 130 and the second electrode 140 from generating heat.

[0025] The first electrode 130 and the second electrode 140 may be formed of multiple layers. For example, the first electrode 130 and the second electrode 140 may have a configuration in which an electrothermal material layer such as W and a conductive material layer such as Ti / Au are stacked on the phase-change film 120, or may have a configuration in which multiple types of conductive material layers are stacked. A conductive material layer separate from the electrode body may be provided between the electrode body and the phase-change film 120.

[0026] The first electrode 130 and the second electrode 140 may have a thickness of about 300 nm, for example.

[0027] The heater 150 is formed above at least a portion of the channel region between the first electrode 130 and the second electrode 140 in the phase-change film 120. Here, the "channel region" refers to a region between the first electrode 130 and the second electrode 140 where current flow and current blocking are switched on and off. The heater 150 may be formed of an electrothermal material such as W. When the first electrode 130 and the second electrode 140 are formed of an electrothermal material, the heater 150 and the first electrode 130 and the second electrode 140 may be formed of the same electrothermal material or different electrothermal materials. The heater 150 may be a thin film of an electrothermal material, and may have a thickness of, for example, about 300 nm.

[0028] First heater electrode 152 and second heater electrode 154 are integrally formed with heater 150 at both ends of heater 150. First heater electrode 152 and second heater electrode 154 may each be formed from the same electrothermal material as heater 150. First heater electrode 152 and second heater electrode 154 may each have a larger wiring width than heater 150. This difference in wiring width allows phase change material switch 100 to pass a larger current per unit cross-sectional area through heater 150 than through first heater electrode 152 and second heater electrode 154, and to generate heat in heater 150 while suppressing heat generation in first heater electrode 152 and second heater electrode 154.

[0029] The first insulating film 160 is provided between the phase change film 120 and the heater 150. In the example shown in the figure, the first insulating film 160 contacts the phase change film 120 and the heater 150. In addition, in the example shown in the figure, the first insulating film 160 covers the entire channel region of the phase change film 120, and both ends of the first insulating film 160 contact the first electrode 130 and the second electrode 140. The first insulating film 160 may be formed of an insulating material, and may be formed of AlO (aluminum oxide) or other Al-based insulating material. As an example, the first insulating film 160 may have a thickness of about 50 nm.

[0030] The second insulating film 170 is provided between the substrate 110 and the phase change film 120. In the example shown in the figure, the second insulating film 170 is in contact with the substrate 110 and the phase change film 120. In the example shown in the figure, the second insulating film 170 covers the entire substrate 110. The second insulating film 170 is made of SiO ２ , or other insulating materials such as oxides. As an example, the second insulating film 170 may have a thickness of about 100 nm.

[0031] The protective film 180 is provided above the first electrode 130, the second electrode 140, the heater 150, and the first insulating film 160. In the example shown in the figure, the protective film 180 is in contact with the first electrode 130, the second electrode 140, the heater 150, and the first insulating film 160. The protective film 180 is made of SiO ２, SiN (silicon nitride), or other insulating materials. As an example, protective film 180 may have a thickness of about 300 nm. Protective film 180 covers each component of phase-change material switch 100, such as first electrode 130, second electrode 140, and heater 150, and protects them from oxidation, external impact, and the like.

[0032] 3 to 6 show an example of a method for manufacturing the phase-change material switch 100 according to this embodiment. First, a substrate 110 is prepared, and a second insulating film 170 is formed on the substrate 110. FIG. 3 shows the state in which the second insulating film 170 has been formed on the substrate 110. In this process, the second insulating film 170 may be formed on the substrate 110 by thermally oxidizing the upper surface of the substrate 110. Alternatively, the second insulating film 170 may be formed on the substrate 110 by a CVD method, a sputtering method, or a coating method. Furthermore, when a substrate 110 made of an insulating material is used, the second insulating film 170 does not need to be formed on the substrate 110.

[0033] Next, the phase change film 120 is formed on the second insulating film 170, and the first insulating film 160 is formed on the phase change film 120. FIG. 4 shows a state in which the phase change film 120 and the first insulating film 160 are formed on the second insulating film 170. In this process, the phase change film 120 may be formed above the substrate 110 by sputtering, and the first insulating film 160 may be formed above the phase change film 120. This process may be performed without exposing the phase change film 120 to the atmosphere. For example, this process may be performed in a chamber under vacuum or filled with an inert gas. Specifically, both the formation of the phase change film 120 and the formation of the first insulating film 160 may be performed while maintaining a vacuum.

[0034] Next, a portion of the first insulating film 160 is removed. FIG. 5 shows a state in which a portion of the first insulating film 160 has been removed. In this step, a portion of the first insulating film 160 may be removed by wet etching so that the first insulating film 160 remains only in the portion where the heater 150 will be formed in a later step. Specifically, the portion where the heater 150 will be formed may be protected with resist, and then a portion of the first insulating film 160 may be removed by wet etching using an alkaline solution. Thereafter, the resist may be removed to expose the remaining first insulating film 160.

[0035] After the first insulating film 160 is formed above the phase change film 120, an electrothermal material film 600 is formed to cover the phase change film 120 and the first insulating film 160. Fig. 6 shows the state in which the electrothermal material film 600 has been formed to cover the phase change film 120 and the first insulating film 160. In this process, the electrothermal material film 600 may be formed by sputtering.

[0036] Next, the electric heating material film 600 is cut to form the first electrode 130, the second electrode 140, and the heater 150. FIG. 7 shows the state after the first electrode 130, the second electrode 140, and the heater 150 have been formed. In this step, a resist 700 may be formed on the electric heating material film 600 in the areas where the first electrode 130, the second electrode 140, and the heater 150 are to be formed. The first electrode 130, the second electrode 140, and the heater 150 may be formed by cutting the electric heating material film 600 between the first electrode 130, the second electrode 140, and the heater 150 by dry etching using an F-based gas such as HF (hydrogen fluoride). In this case, the first electrode 130 and the second electrode 140 may be formed on the phase change film 120, spaced apart from each other, by removing the resist, and the heater 150 may be formed above at least a portion of the channel region between the first electrode 130 and the second electrode 140 in the phase change film 120. Alternatively, the heater 150 may be formed above the first insulating film 160 by forming a resist 700 above the first insulating film 160 and performing a dry etching process. If the first insulating film 160 is made of an Al-based material, it reacts with an F-based gas to form AlF in the dry etching process. Because AlF is passive, the portion of the phase change film 120 where the first insulating film 160 is formed, i.e., the channel region of the phase change film 120, is not affected by the dry etching. If necessary, after removing the resist 700, a protective film 180 covering the first electrode 130, the second electrode 140, the heater 150, and the first insulating film 160 may be formed by a CVD method, a sputtering method, or a coating method. If necessary, the phase change film 120 may be heated to change its phase from the amorphous phase to the crystalline phase.

[0037] FIG. 7 shows an example in which the first electrode 130, the second electrode 140, and the heater 150 are integrally formed from a single electrothermal material film 600. Alternatively, the first electrode 130, the second electrode 140, and the heater 150 may be formed separately. In FIG. 5 , after forming the first insulating film 160, the electrothermal material film 600 may be formed only on the first insulating film 160, and then a portion of the electrothermal material film 600 may be removed by dry etching to form the heater 150. The first electrode 130 and the second electrode 140 may then be formed on the phase-change film 120, spaced apart from each other, by vapor deposition and lift-off. Specifically, the first electrode 130 and the second electrode 140 may be formed by forming a resist on portions where the first electrode 130 and the second electrode 140 are not to be formed, vapor-depositing an electrode material, and then performing a lift-off process to remove the resist and excess electrode material. In this method, unlike the method shown in FIG. 7, the first electrode 130, the second electrode 140, and the heater 150 can be formed from different materials.

[0038] According to the manufacturing method of the phase-change material switch 100 described above, unlike when the heater 150 is embedded under the phase-change film 120, the process of forming the heater 150 does not include a step of embedding the heater 150 in an insulating film or the like that has been opened, and therefore, it is possible to prevent the heater 150 from being corroded. Furthermore, according to the manufacturing method described above, unlike when the heater 150 is embedded under the phase-change film 120, it does not include a step of exposing the heater 150 by chemical mechanical polishing, and therefore, the dimensional accuracy of the heater 150 is improved. Furthermore, according to the manufacturing method described above, unlike when the first electrode 130 and the second electrode 140 are formed on the phase-change film 120 by vapor deposition, the phase-change film 120 and the first insulating film 160 are formed while maintaining a vacuum, thereby preventing the channel region of the phase-change film 120 from reacting with the atmosphere and deteriorating. Furthermore, according to the manufacturing method described above, by forming the first electrode 130, the second electrode 140, and the heater 150 from a single electrothermal material film 600 by dry etching, it is possible to prevent tailing of the first electrode 130, etc., compared to when the first electrode 130, etc. is formed by evaporation and lift-off without forming the electrothermal material film 600.

[0039] 8 shows a cross-sectional view of a phase change material switch 800 according to a modification of this embodiment. Phase change material switch 800 is a modification of phase change material switch 100 shown in FIGS. 1 to 7, and therefore, a description thereof will be omitted hereinafter except for the differences.

[0040] The first oxidation resistant film 810 is provided between the phase change film 120 and the first insulating film 160. In the example shown in the figure, the first oxidation resistant film 810 is in contact with the phase change film 120 and the first insulating film 160. In addition, in the example shown in the figure, the first oxidation resistant film 810 covers the entire channel region of the phase change film 120, and both ends of the first oxidation resistant film 810 are in contact with the first electrode 130 and the second electrode 140. The first oxidation resistant film 810 may be formed of a nitride such as SiN. As an example, the first oxidation resistant film 810 may have a thickness of about 20 nm, and the sum of the thickness of the first oxidation resistant film 810 and the thickness of the first insulating film 160 may be about 50 nm.

[0041] The second oxidation resistant film 820 is provided between the substrate 110 and the phase change film 120. The second oxidation resistant film 820 may be provided between the second insulating film 170 and the phase change film 120. In the example shown in the figure, the second oxidation resistant film 820 is in contact with the phase change film 120 and the second insulating film 170. In addition, in the example shown in the figure, the second oxidation resistant film 820 covers the entire second insulating film 170. The second oxidation resistant film 820 may be formed of a nitride such as SiN. The second oxidation resistant film 820 may be formed of the same material as the first oxidation resistant film 810, or may be formed of a different material. As an example, the second oxidation resistant film 820 may have a thickness of about 10 nm.

[0042] According to the phase change material switch 800 described above, the phase change film 120 is not in direct contact with the substrate 110, the first insulating film 160, and the second insulating film 170, so that the channel region of the phase change film 120 can be prevented from coming into contact with oxygen in the oxide contained in the first insulating film 160, etc. and being oxidized.

[0043] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0044] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order.

[0045] REFERENCE SIGNS LIST 100 Phase change material switch 110 Substrate 120 Phase change film 130 First electrode 140 Second electrode 150 Heater 152 First heater electrode 154 Second heater electrode 160 First insulating film 170 Second insulating film 180 Protective film 600 Electric heating material film 700 Resist 800 Phase change material switch 810 First oxidation prevention film 820 Second oxidation prevention film

Claims

1. A phase change material switch comprising: a substrate; a phase change film formed above the substrate; first and second electrodes formed spaced apart from each other on the phase change film; and a heater formed above at least a portion of a channel region in the phase change film between the first and second electrodes.

2. The phase change material switch of claim 1, further comprising a first insulating film between said phase change film and said heater.

3. The phase change material switch according to claim 2, further comprising a first oxidation prevention film between the phase change film and the first insulating film.

4. The phase change material switch of claim 3, further comprising a second oxidation prevention film between the substrate and the phase change film.

5. The phase change material switch of claim 1, wherein said heater and said first and second electrodes are formed from the same electrothermal material.

6. The phase change material switch of claim 1, wherein the first and second electrodes are formed of a conductive material having a higher electrical conductivity than the heater.

7. A phase change material switch as described in claim 1, comprising first and second heater electrodes integrally formed with the heater at both ends of the heater, each of the first and second heater electrodes having a wiring width larger than that of the heater.

8. A method for manufacturing a phase change material switch, comprising: forming a phase change film above a substrate; forming first and second electrodes spaced apart on the phase change film; and forming a heater in the phase change film above at least a portion of a channel region between the first and second electrodes.

9. The method according to claim 8, further comprising forming a first insulating film above the phase change film, and the heater is formed above the first insulating film.

10. The manufacturing method according to claim 9, wherein both the formation of the phase change film and the formation of the first insulating film are carried out while maintaining a vacuum.

11. The manufacturing method described in claim 9, further comprising forming an electric heating material film covering the phase change film and the first insulating film after the first insulating film is formed above the phase change film, and forming the first and second electrodes and the heater by cutting between the first electrode, the second electrode, and the heater in the electric heating material film.

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