Phase change materials

Abstract

The present invention provides a phase change material which is suitable for the achievement of a larger capacity.　A phase change material which contains, in atomic percentage, 1-40% of Ge, 40-90% of Te, and not less than 0% but less than 5% of Sb, while additionally containing one or more elements that are selected from among Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca and Mg in an amount of 1-59%.

Description

Technical Field

[0001] The present invention relates to phase change materials.

Background Art

[0002] The development of phase change memory, which is a next-generation memory, is progressing. Phase change memory is a non-volatile memory that records information by utilizing the difference in electrical resistance between the amorphous state and the crystalline state of the phase change material used. Phase change memory has been attracting increasing attention for its high speed and large capacity.

[0003] Conventionally, Ge-Sb-Te-based phase change materials such as Ge , , , ,

[0005] , , ,

[0007] , , , , ,

[0004] ,

[0006] , , , , Sb 22 Te 56 (GST) have been widely used (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since GST has a low crystallization temperature, the amorphous state tends to become unstable at high temperatures. In addition, because the melting point of the crystalline state is high and a large amount of energy is required for the phase change from the crystalline state to the amorphous state, the power consumption tends to increase. When the power consumption increases, GST tends to reach a high temperature, so the amorphous state tends to become even more unstable. Therefore, phase change memory using GST has a problem that it is difficult to further increase the capacity.

[0006] In view of the above, an object of the present invention is to provide a phase change material suitable for increasing the capacity.

Means for Solving the Problems

[0007] Various embodiments of phase change materials that solve the above problems will be described.

[0008] The phase change material of Embodiment 1 is characterized by containing, in atomic percent, Ge 1% to 40%, Te 40% to 90%, Sb 0% to less than 5%, and further containing 1% to 59% of one or more types selected from Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg.

[0009] In the phase change material of Embodiment 2, it is preferable that the ratio of Te to Ge content, Te / Ge, is 2 to 8 in Embodiment 1.

[0010] The phase change material of Embodiment 3 preferably contains 0% to less than 5% Sb+As in Embodiment 1 or Embodiment 2.

[0011] In the phase change material of Embodiment 4, it is preferable that the crystallization temperature Tx is 150°C or higher in any one embodiment from Embodiments 1 to 3.

[0012] In the phase change material of Embodiment 5, it is preferable that the crystal melting point Tm is 600°C or less in any one embodiment from Embodiments 1 to 4.

[0013] In the phase change material of embodiment 6, it is preferable that the difference Δ(Tm-Tx) between the crystal melting point Tm and the crystallization temperature Tx is 400°C or less in any one embodiment from embodiment 1 to embodiment 5.

[0014] The phase change material of embodiment 7 is characterized by containing, in atomic percent, Ge 1% to 40%, Te 40% to 90%, Ge+Te 41% to 99%, and Sb 0% to less than 5%, and having a difference Δ(Tm-Tx) between the crystal melting point Tm and the crystallization temperature Tx of 400°C or less.

[0015] The phase change material of Aspect 8 contains, in atomic percentage, 1% to 40% of Ge, 40% to 90% of Te, 41% to 99% of Ge + Te, less than 0% to 5% of Sb, and 0% to 59% of Ga, and is characterized by containing at least one crystal selected from GeTe4, GeTe, Te, and Ga2Te3 in the crystalline state.

[0016] The target of Aspect 9 is characterized by using the phase change material in any one of Aspects 1 to 8.

[0017] The thin film of Aspect 10 is characterized by using the phase change material in any one of Aspects 1 to 8.

[0018] The memory element of Aspect 11 is characterized by containing the phase change material in any one of Aspects 1 to 8.

[0019] The memory device of Aspect 12 is characterized by including the memory element in Aspect 11.

[0020] The method of Aspect 13 is a method of recording information, and includes the step of recording information by applying a voltage to a memory layer made of a phase change material and causing a phase change of the memory layer from a first state to a second state. The memory layer contains, in atomic percentage, 1% to 40% of Ge, 40% to 90% of Te, less than 0% to 5% of Sb, and further contains 1% to 59% of one or more selected from Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, Mg, and is characterized by including a phase change material.

[0021] The method of Aspect 14 is, in Aspect 13, in the step of recording information, GeTe 4、 It is preferable that at least one crystal selected from GeTe, Te, and Ga2Te3 precipitates.

Advantages of the Invention

[0022] According to the present invention, a phase change material suitable for increasing the storage capacity can be provided.

Brief Description of the Drawings

[0023] [Figure 1] Figure 1 is a schematic cross-sectional view of a memory element according to the first embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view of a memory element according to the second embodiment of the present invention. [Figure 3] Figure 3 is a schematic cross-sectional view of a memory element according to the third embodiment of the present invention. [Figure 4] Figure 4 is a schematic cross-sectional view of a memory element according to the fourth embodiment of the present invention. [Figure 5] Figure 5 is a schematic cross-sectional view of a memory element according to the fifth embodiment of the present invention. [Figure 6] Figure 6 is a schematic cross-sectional view of a memory element according to the sixth embodiment of the present invention. [Figure 7] Figure 7 is a schematic cross-sectional view of a memory element according to the seventh embodiment of the present invention. [Figure 8] Figure 8 is a schematic cross-sectional view of a memory element according to the eighth embodiment of the present invention. [Figure 9] Figure 9 is a schematic cross-sectional view of a memory element according to the ninth embodiment of the present invention. [Figure 10] Figure 10 is a schematic cross-sectional view of a memory element according to the tenth embodiment of the present invention. [Figure 11] Figure 11 is a schematic cross-sectional view of a memory element according to the eleventh embodiment of the present invention. [Figure 12] Figure 12 is a schematic cross-sectional view of a memory element according to the twelfth embodiment of the present invention. [Figure 13] Figure 13 is a schematic cross-sectional view of a memory element according to the thirteenth embodiment of the present invention. [Figure 14] Figure 14 is a schematic cross-sectional view of a memory element according to the fourteenth embodiment of the present invention. [Figure 15] Figure 15 is a schematic cross-sectional view of a memory element according to the fifteenth embodiment of the present invention. [Figure 16] Figure 16 is a schematic cross-sectional view of a memory element according to the sixteenth embodiment of the present invention. [Figure 17] Figure 17 is a schematic cross-sectional view of a memory element according to the 17th embodiment of the present invention. [Figure 18] Figure 18 is a schematic cross-sectional view of a memory element according to the 18th embodiment of the present invention. [Figure 19] Figure 19 is a schematic cross-sectional view of a memory element according to the 19th embodiment of the present invention. [Figure 20] Figure 20 is a schematic three-dimensional view of a memory element according to one embodiment of the present invention. [Modes for carrying out the invention]

[0024] Preferred embodiments are described below. However, the following embodiments are merely illustrative, and the present invention is not limited to these embodiments.

[0025] <Phase change materials> The phase-change material of the present invention is characterized by containing, in atomic percent, Ge 1% to 40%, Te 40% to 90%, Sb 0% to less than 5%, and further containing 1% to 59% of one or more elements selected from Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg. The reasons for defining the composition in this way and the content of each component will be explained below. In the following explanation, unless otherwise specified, "%" means "atomic percent".

[0026] Ge is an essential component that increases the crystallization temperature of phase change materials and stabilizes the amorphous state. The Ge content is preferably 1% to 40%, with ranges of 1% to 39%, 2% to 35%, 2% to 30%, 5% to 30%, 7.5% to 30%, 7.5% to 25%, 10% to 25%, and especially 10% to 20%. If the Ge content is too low, the amorphous state tends to become unstable. Also, the precipitation of GeTe4 crystals, as described later, becomes difficult. If the Ge content is too high, the crystal melting point tends to become too high.

[0027] Te is an essential component of phase change materials. The Te content is 40% to 90%, with 45% to 90%, 47% to 90%, 50% to 85%, 50% to 82.5%, 55% to 82.5%, 60% to 82.5%, 60% to 80%, 62.5% to 80%, and especially 65% ​​to 80%. If the Te content is too low, the crystallization temperature will decrease, and the amorphous state will tend to become unstable. If the Te content is too high, the crystallization temperature will also decrease, and the amorphous state will tend to become unstable.

[0028] The Ge+Te (total amount of Ge and Te) content is preferably 41%~99%, 45%~99%, 50%~99%, 50%~98%, 55%~97%, 60%~96%, 65%~95%, 70%~95%, and especially preferably 75%~95%.

[0029] Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg are components that easily stabilize the amorphous state of phase change materials. Therefore, the phase change material of the present invention contains one or more components selected from Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg in amounts of 1% to 59%, and is particularly preferably contained in amounts of 1% to 58%, 1% to 55%, 1% to 50%, 1% to 45%, 1% to 40%, 1% to 35%, 1% to 30%, 1% to 25%, 1% to 20%, 1% to 15%, 2% to 15%, 2.5% to 15%, and especially 2.5% to 10%. If the content of these components is too high, the amorphous state tends to become unstable. Furthermore, the content of Si+Al+Ga+Sn+Bi+Cu+Ag+Zn+Y+In+Ca+Mg (total amounts of Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg) is preferably between 1% and 59%, with 1% to 58%, 1% to 55%, 1% to 50%, 1% to 45%, 1% to 40%, 1% to 35%, 1% to 30%, 1% to 25%, 1% to 20%, 1% to 15%, 2% to 15%, 2.5% to 15%, and particularly preferably between 2.5% and 10%. In this invention, "x+y+z+···" represents the total amount of each component. Here, it is not necessary to include each component as an essential component, and it is acceptable for some components to be absent (content of 0%). Furthermore, "x+y+z+··· A%~B%" includes cases such as "x=0%, y+z+··· A%~B%" and "x=0%, y=0%, z+··· A%~B%".

[0030] Of the above components, Ga is a component that easily increases the crystallization temperature and stabilizes the amorphous state. Also, as will be described later, it is a component that easily reduces the temperature difference Δ(Tm-Tx) between the crystallization temperature Tx and the crystal melting point Tm. The Ga content is preferably 0%~59%, 1%~59%, 1%~58%, 1%~55%, 1%~50%, 1%~45%, 1%~40%, 1%~35%, 1%~30%, 1%~25%, 1%~20%, 1%~15%, 2%~15%, 2.5%~15%, and especially preferably 2.5%~10%. If the Ga content is too high, the amorphous state tends to become unstable.

[0031] Of the above components, Ag is a component that easily stabilizes the amorphous state. Also, as will be described later, it is a component that easily reduces the temperature difference Δ(Tm-Tx) between the crystallization temperature Tx and the crystal melting point Tm. The Ag content is preferably 0%~59%, 1%~59%, 1%~58%, 1%~55%, 1%~50%, 1%~45%, 1%~40%, 1%~35%, 1%~30%, 1%~25%, 1%~20%, 1%~15%, 2%~15%, 2.5%~15%, and especially preferably 2.5%~10%. If the Ag content is too high, the amorphous state tends to become unstable.

[0032] The Ga+Ag (total amount of Ga and Ag) content is preferably 1%~59%, 1%~58%, 1%~55%, 1%~50%, 1%~45%, 1%~40%, 1%~35%, 1%~30%, 1%~25%, 1%~20%, 1%~15%, 2%~15%, 2.5%~15%, and especially preferably 2.5%~10%. This stabilizes the amorphous state, increases the crystallization temperature, and makes it easier to reduce Δ(Tm-Tx).

[0033] Sb is a component that tends to lower the crystallization temperature of phase change materials. Therefore, the Sb content is preferably 0% to less than 5%, and is preferably 0% to 4%, 0% to 3%, and especially 0% to 2%.

[0034] The phase change material of the present invention may contain the following components in addition to the above components.

[0035] F, Cl, Br, and I are components that easily stabilize the amorphous state of phase change materials. The content of F+Cl+Br+I (total amount of F, Cl, Br, and I) is preferably 0% to 40%, 0% to 30%, 0% to 20%, and especially 0% to 10%. If the content of F+Cl+Br+I is too high, the amorphous state tends to become unstable. Also, weather resistance tends to decrease. The content of each component of F, Cl, Br, and I is preferably 0% to 40%, 0% to 30%, 0% to 20%, and especially 0% to 10%.

[0036] It may contain B, C, Cr, Mn, Ti, Fe, etc. The content of B+C+Cr+Mn+Ti+Fe (total amount of B, C, Cr, Mn, Ti, and Fe) is preferably 0% to 40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, 0% to 1%, and especially less than 0% to 1%. If the content of these components is too high, the amorphous state tends to become unstable. The content of each component B, C, Cr, Mn, Ti, and Fe is preferably 0% to 10%, 0% to 5%, 0% to 1%, and especially less than 0% to 1%.

[0037] As is a component that easily stabilizes the amorphous state of phase change materials. However, since As is a toxic component, from the viewpoint of reducing environmental impact, it is preferable that the As content be 30% or less, 25% or less, 20% or less, 10% or less, 5% or less, 3% or less, or especially substantially absent. In this specification, "substantially absent" means that the content is 0.1% or less.

[0038] The Sb+As (combined amount of Sb and As) content is preferably 0% to less than 5%, 0% to 4%, 0% to 3%, and especially 0% to 2%. This helps to suppress the decrease in crystallization temperature and reduce the environmental impact.

[0039] It is preferable that the material is substantially free of Cd, Tl, and Pb. This further reduces the environmental impact.

[0040] The phase-change material of the present invention, having the above configuration, makes it easier to increase the crystallization temperature. Specifically, the crystallization temperature Tx can be set to 150°C or higher, 160°C or higher, 170°C or higher, 175°C or higher, 180°C or higher, 185°C or higher, 190°C or higher, 195°C or higher, 200°C or higher, 205°C or higher, and especially 210°C or higher. This makes it easier to stabilize the amorphous state and improve the heat resistance of the phase-change material. In order to make Δ(Tm-Tx) a desired value, the upper limit of the crystallization temperature Tx can be, for example, 400°C or lower, 350°C or lower, and especially 300°C or lower.

[0041] The phase-change material of the present invention, having the above configuration, makes it easier to lower the crystal melting point. Specifically, it is preferable to set the crystal melting point Tm to 600°C or less, 550°C or less, 500°C or less, 450°C or less, 430°C or less, 410°C or less, and especially 400°C or less. This makes it easier to lower the energy required for the phase change. In order to make Δ(Tm-Tx) a desired value, it is preferable to set the lower limit of the crystal melting point Tm to, for example, 250°C or more, 260°C or more, 280°C or more, 300°C or more, 320°C or more, 340°C or more, 360°C or more, and especially 370°C or more.

[0042] The phase-change material of the present invention, having the above configuration, can achieve both a high crystallization temperature and a low crystal melting point. Therefore, the difference Δ(Tm-Tx) between the crystal melting point Tm and the crystallization temperature Tx can be 400°C or less, 350°C or less, 300°C or less, 250°C or less, 200°C or less, 190°C or less, 180°C or less, 170°C or less, 160°C or less, and especially 150°C or less. The lower limit of Δ(Tm-Tx) can be, for example, 50°C or more, and especially 80°C or more.

[0043] The phase-change material of the present invention preferably has a Te / Ge content ratio of 2 to 8, 3 to 7, 4 to 7, and particularly 4 to 6.5. When Te / Ge satisfies the above value, the phase-change material is more likely to contain GeTe4 crystals in its crystalline state.

[0044] The phase change material preferably contains at least one crystal selected from GeTe4, GeTe, Te, and Ga2Te3 as its main component in the crystalline state, and is particularly preferably GeTe4 crystal as its main component. Here, "containing a crystal as its main component" means that the intensity of the first peak in XRD is at least twice that of the first peak intensity of other crystalline components. The melting point of GeTe4 crystal is around 380°C, which is lower than the melting point of crystals precipitated by conventional GST (630°C). Therefore, a phase change material containing GeTe4 crystal requires less energy for the phase transition from the crystalline state to the amorphous state, thus reducing power consumption. Note that the phase change material may also contain crystals other than the main component. For example, it may contain GeTe4 crystal as its main component and also contain at least one crystal selected from GeTe, Te, and Ga2Te3.

[0045] The phase change material of the present invention is preferably used as a target. Furthermore, the phase change material of the present invention is preferably used as a thin film. The target is preferably, for example, a sputtering target. The thin film is preferably, for example, a memory layer of a memory element described later. By using the phase change material of the present invention in these applications, it can effectively contribute to increasing the capacity of phase change memory. In other words, targets and thin films using the phase change material of the present invention can effectively contribute to increasing the capacity of phase change memory.

[0046] The phase-change material of the present invention can be prepared, for example, as follows: First, raw materials are mixed to achieve the desired composition. Next, the mixed raw materials are placed in a quartz glass ampoule that has been heated and evacuated, and the ampoule is sealed with an oxygen burner while evacuating the vacuum. Next, the sealed quartz glass ampoule is held at approximately 650°C to 1000°C for 6 to 12 hours. After that, by rapidly cooling to room temperature, an amorphous and bulk phase-change material can be obtained.

[0047] Furthermore, the phase change material of the present invention is not limited to being amorphous and bulk. For example, a phase change material in the form of a powder sintered body can be obtained by mixing raw materials to obtain a homogeneous mixture of desired composition, and then hot-pressing the mixture.

[0048] The raw materials may include elemental raw materials (Ge, Ga, Si, Te, Ag, I, etc.) or compound raw materials (GeTe4, Ga2Te3, AgI, etc.). Alternatively, these may be used in combination.

[0049] For example, by using the obtained phase change material as a sputtering target, a thin film (memory layer) having the above-described composition can be formed. The sputtering target can be a powder sintered body of the phase change material. The sputtering target may be used in an amorphous state or in a crystalline state. For example, when using bulk phase change material as a sputtering target, the bulk phase change material can be pulverized in an inert atmosphere to produce fine powder, and then the fine powder can be hot-pressed to produce a powder sintered body. Note that using amorphous phase change material makes it easier to obtain a sputtering target in which the components are uniformly dispersed.

[0050] Furthermore, pure element targets (Ge, Te, Sb, Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg) may be used as sputtering targets. Alternatively, thin films having the above-mentioned composition may be formed by adjusting the deposition output as appropriate using a multi-component sputtering method with a binary alloy target or a ternary or higher alloy target.

[0051] The manufacturing method for the thin film is not particularly limited, and methods other than sputtering, such as CVD (Chemical Vapor Deposition) and ALD (Atomic Layer Deposition), can be selected. In particular, the sputtering method is preferred because it allows for easy control of composition and film thickness.

[0052] As described above, the phase change material of the present invention contains, in atomic percent, 1% to 40% Ge, 40% to 90% Te, and less than 5% Sb, and further contains 1% to 59% of one or more elements selected from Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg. Having the above configuration, the phase change material of the present invention can stabilize the amorphous state and improve heat resistance. Furthermore, it can lower the melting point of the crystalline state, thereby reducing the energy required for the phase change from the crystalline state to the amorphous state. Therefore, it is suitable for large-capacity applications.

[0053] <Memory element> Figure 1 is a schematic cross-sectional view of a memory element according to a first embodiment of the present invention. The memory element 10 comprises a first electrode 1, a second electrode 2, a memory layer 3, and an insulator 4. The memory layer 3 contains the phase change material of the present invention. The first electrode 1 is formed on the upper surface of the memory layer 3. The second electrode 2 is formed on the lower surface of the memory layer 3 and is positioned opposite the first electrode 1. The periphery of the second electrode 2 is covered with the insulator 4. In this embodiment, the memory layer 3 is positioned between the first electrode 1 and the second electrode 2. In addition, the insulator 4 is positioned on the side surface of the second electrode 2.

[0054] Inorganic materials can be used for the first electrode 1 and the second electrode 2. As inorganic materials, metallic materials and ceramic materials can be used. For metallic materials, it is preferable to use, for example, tungsten, titanium, copper, or platinum. For ceramic materials, it is preferable to use, for example, tungsten nitride or titanium nitride.

[0055] The thickness of the first electrode 1 and the second electrode 2 can be designed as appropriate. For example, it is preferable to have a thickness of 200 nm or less, 100 nm or less, 80 nm or less, 60 nm or less, and especially 50 nm or less. The smaller the thickness, the more advantageous it is to increase the capacity of the memory device. The lower limit of the thickness is preferably, for example, 1 nm or more and 2 nm or more.

[0056] As shown in Figure 1, the memory element 10 can record information by changing the resistance state by applying a predetermined voltage to the memory layer 3. More specifically, the process includes the step of applying a voltage to the memory layer 3, which is made of a phase-change material, and recording information by changing the phase of the memory layer 3 from a first state to a second state. Here, the first state and / or the second state refer to a crystalline state or an amorphous state. The crystalline state has lower resistance than the amorphous state.

[0057] For example, if memory layer 3 is in a crystalline state, applying a high voltage to memory layer 3 and rapidly heating and cooling it can change the crystalline state to an amorphous state (first phase change). This allows memory layer 3 to undergo a phase change to an amorphous state with high resistance. In this case, the first state is the crystalline state and the second state is the amorphous state.

[0058] Furthermore, if the memory layer 3 is in an amorphous state, applying a lower voltage to the memory layer 3 compared to the first phase change, and performing gentle heating and cooling, can change the amorphous state to a crystalline state (second phase change). This allows the memory layer 3 to undergo a phase change to a crystalline state with low resistance. In this case, the first state is amorphous, and the second state is crystalline.

[0059] In this way, the resistance state can be changed by inducing a phase change in memory layer 3. This allows information to be recorded.

[0060] In the step of recording information, it is preferable that at least one crystal selected from GeTe4, GeTe, Te, and Ga2Te3 precipitates. Phase change materials containing GeTe4 crystals require less energy for the phase transition from a crystalline state to an amorphous state, thus reducing the power consumption of the memory element.

[0061] Note that the structure of the memory element is not limited to Figure 1. Figures 2 to 19 are schematic cross-sectional views of memory elements according to the second to 19th embodiments of the present invention. In the modified examples of the memory elements shown in Figures 2 to 19, the memory layer 3 also contains the phase change material of the present invention. Furthermore, information can be recorded by changing the resistance state of the memory layer 3.

[0062] For example, Figure 2 is a schematic cross-sectional view of a memory element according to a second embodiment of the present invention. In the memory element shown in Figure 2, an insulator 4 is arranged on the side surface of the first electrode 1 and the memory layer 3. In this embodiment as well, information can be recorded by changing the resistance state of the memory layer 3.

[0063] <Storage device> Figure 20 is a schematic three-dimensional view of a memory device according to one embodiment of the present invention. As shown in Figure 20, the memory device 100 includes a memory element 10, a switch element 20, a word line 30, and a bit line 40. The bit line 40 is perpendicular to the word line 30 in a plan view. The memory element 10 is positioned at the intersection of the word line 30 and the bit line 40 in a plan view. The memory device 100 of this embodiment is a so-called crosspoint type memory device. [Examples]

[0064] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0065] Tables 1-14 show Examples 1-21, 23-113, and Comparative Example 22 of the present invention.

[0066] [Table 1]

[0067] [Table 2]

[0068] [Table 3]

[0069] Table 4

[0070] Table 5

[0071] Table 6

[0072] Table 7

[0073] Table 8

[0074] Table 9

[0075] Table 10

[0076] Table 11

[0077] Table 12

[0078] Table 13

[0079] [Table 14]

[0080] The samples for the examples were prepared as follows. First, a quartz glass ampoule was heated and evacuated under vacuum. Then, the raw materials were mixed to the compositions shown in Tables 1-7 and placed into the quartz glass ampoule. Next, the quartz glass ampoule was sealed with an oxygen burner. Then, the sealed quartz glass ampoule was placed in a melting furnace and heated to 650°C-1000°C at a rate of 10°C-40°C / hour, and held for 6-12 hours. During the holding time, the quartz glass ampoule was inverted to agitate the molten material. Finally, the quartz glass ampoule was removed from the melting furnace and rapidly cooled to room temperature to obtain the sample.

[0081] The crystallization temperature Tx and melting point Tm were measured for the obtained samples using DTA. The difference between Tm and Tx, Δ(Tm-Tx), was also determined.

[0082] The comparative example is Ge 22 S 22 Te 56 The crystallization temperature Tx and melting point Tm of (GST) were taken from literature values.

[0083] Next, a resistivity-changing material was deposited to a thickness of 150 nm to fabricate a thin film. The composition after deposition was determined by SEM-EDX. The determined deposition compositions are shown in Tables 8-14. The film deposition was performed by Ar sputtering under reduced pressure.

[0084] As is clear from Tables 1-7, the phase change materials of Examples 1-21 and 23-57 had a higher crystallization temperature Tx and a lower crystal melting point Tm compared to GST. Furthermore, Δ(Tm-Tx) was smaller compared to GST. In addition, thin films of Examples 58-113, shown in Tables 8-14, were successfully fabricated. [Industrial applicability]

[0085] The phase change material of the present invention can be suitably used in memory elements, memory devices, and sputtering targets applicable to their manufacture. [Explanation of symbols]

[0086] 1 1st electrode 2 2nd electrode 3 Memory layer 4. Insulator 10 memory elements 20 Switching elements 30 word lines 40-bit line 100 storage device

Claims

1. It contains, in atomic percent, Ge 1% to 40%, Te 40% to 90%, and Sb 0% to less than 5%. A phase change material further containing 1% to 59% of one or more elements selected from Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg, and 1% to 59% of Ga + Ag.

2. The phase change material according to claim 1, wherein the ratio of Te to Ge content, Te / Ge, is 2 to 8.

3. A phase change material according to claim 1 or 2, containing 0% to less than 5% Sb + As.

4. The phase change material according to claim 1 or 2, wherein the crystallization temperature Tx is 150°C or higher.

5. The phase change material according to claim 1 or 2, wherein the crystal melting point Tm is 600°C or less.

6. The phase change material according to claim 1 or 2, wherein the difference Δ(Tm-Tx) between the crystal melting point Tm and the crystallization temperature Tx is 400°C or less.

7. It contains, in atomic percent, Ge 1% to 40%, Te 40% to 90%, Ge + Te 41% to 99%, Sb 0% to less than 5%, and Ga + Ag 1% to 59%. A phase-change material in which the difference between the crystalline melting point Tm and the crystallization temperature Tx, Δ(Tm-Tx), is 400°C or less.

8. It contains, in atomic percent, Ge 1% to 40%, Te 40% to 90%, Ge + Te 41% to 99%, Sb 0% to less than 5%, Ga 0% to 59%, and Ga + Ag 1% to 59%. GeTe in the crystalline state ４ GeTe, Te and Ga ２ Te ３ A phase change material comprising at least one type of crystal selected from.

9. A target using the phase change material according to claim 1, 7, or 8.

10. A thin film using the phase change material according to claim 1, 7, or 8.

11. A memory element comprising the phase change material according to claim 1, 7, or 8.

12. A storage device comprising the storage element according to claim 11.

13. A method of recording information, The process includes the step of applying a voltage to a memory layer made of a phase-change material to change the phase of the memory layer from a first state to a second state and thereby record information. A method comprising a phase change material in which the memory layer contains, in atomic percent, 1% to 40% Ge, 40% to 90% Te, and less than 5% Sb, and further contains 1% to 59% of one or more selected from Si, Al, Ga, Sn, Bi, Cu, Ag, Zn, Y, In, Ca, and Mg, and 1% to 59% Ga + Ag.

14. The method according to claim 13, wherein in the step of recording information, at least one crystal selected from GeTe4, GeTe, Te, and Ga2Te3 is precipitated.

15. The phase change material according to claim 1, comprising 1 to 59% Ga by atomic percent.

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