CN102227015B - Phase transition storage material and preparation method thereof - Google Patents

Abstract

The invention relates to a phase-change storage material and a preparation method thereof, wherein the phase-change storage material is a compound of gallium-antimony-selenium. The chemical composition is Ga _x Sb _y Se _z , where 4<x<40, 25<y<85, 5<z<70, x+y+z=100. Compared with the commonly used Ge ₂ Sb ₂ Te ₅ (GST) material, the gallium-antimony-selenium phase change thin film material of the invention has better thermal stability, faster phase change speed and lower melting point. At the same time, the gallium-antimony-selenium phase-change thin film material of the present invention does not contain element Te, is environmentally friendly, does not pollute semiconductor equipment, and is convenient for subsequent processing. The phase change memory made of the phase change memory material has the advantages of strong data retention, low power consumption, fast operation speed, stable electrical performance and the like.

Description

A kind of phase change memory material and preparation method thereof

technical field

The invention provides a phase-change storage material and a preparation method thereof, in particular to a gallium-antimony-selenium phase-change thin-film storage material for phase-change storage.

Background technique

Phase change memory (PCM) is a non-volatile semiconductor memory that has emerged in recent years. Compared with a variety of existing semiconductor storage technologies, it has the advantages of shrinkable device size (nanoscale), high-speed reading, low power consumption, high density, and simple manufacturing process. Widely optimistic about a strong competitor, it is expected to replace flash memory (Flash technology) and become the mainstream storage technology of the next generation of non-volatile memory, so it has a broad market prospect.

Phase-change memory uses Joule heat generated by electrical or optical pulses to make phase-change memory materials undergo reversible phase transitions between crystalline (low resistance) and amorphous (high resistance) states to achieve data writing and erasing. The readout is achieved by measuring the state of the resistor. The core of phase change memory is the phase change storage medium material, and the commonly used phase change storage material system is mainly tellurium-based compounds, such as Ge-Sb-Te, Si-Sb-Te, Ag-In-Sb-Te, etc. Especially Ge ₂ Sb ₂ Te ₅ (GST) has been widely used in phase-change optical discs and phase-change memories. However, there are also the following problems: one, the crystallization temperature is low, the data retention cannot be guaranteed, and the danger of data loss is faced, which restricts its application field; two, the power consumption is large, and a large driving current (greater than 1 mA). As the size shrinks, the driving capability of transistors or diodes is very limited, and it is difficult to meet high-current driving, so it is difficult to achieve high-density storage; 3. The phase change speed needs to be further improved. Studies have shown that phase change memory based on GST can achieve stable RESET operation. The electrical pulse is at least 500 ns. DRAM completes erasing and writing at high speed, which requires us to explore storage materials with faster phase change speed. 4. Tellurium-based phase-change storage materials contain easily diffused tellurium, which makes the interface between the phase-change storage material and the electrode unstable, and the components of the phase-change storage material are also easy to segregate, and it is easy to pollute semiconductor equipment, which is harmful to the human body and The environment is also unfavorable, which is contrary to the current environmental protection policy advocated by the state.

Therefore, how to provide a phase change thin film material with good thermal stability, strong data retention, low power consumption, fast phase change speed, environmental friendliness and compatibility with CMOS technology is a problem to be solved in the current technical field.

Contents of the invention

The invention provides a phase-change storage material and a preparation method thereof, in particular to a gallium-antimony-selenium phase-change thin film material used in a phase-change storage. The invention can solve the problems of poor thermal stability and data retention ability, slow phase change speed, high power consumption and environmental pollution exhibited by phase change storage materials in the prior art.

To achieve the above object, the present invention adopts the following technical solution: a phase change memory material, which is a compound of gallium-antimony-selenium.

Preferably, the chemical composition is Ga _x Sb _y Se _z , where 4<x<40, 25<y<85, 5<z<70, x+y+z=100.

Preferably, the chemical composition is Ga _x Sb _y Se _z , where 10≤x≤20, 50≤y≤85, 20≤z≤40, x+y+z=100.

Preferably _{, the} chemical composition is _GaxSbySez , where x=8, y=34, z=58.

Preferably, _the chemical composition is _GaxSbySez , where x=13, y=32, z=55 _.

Preferably, _the chemical composition is _GaxSbySez , where x=34, y=40, z=26 _.

Preferably, the gallium-antimony-selenium compound has certain segregation in composition when the thin film is prepared, and the error of segregation elements is within 10%.

Preferably, the gallium-antimony-selenium compound further includes doping atoms, and the molar ratio of the doping atoms is 0% to 20%.

Preferably, the doping atoms are one of aluminum, bismuth, nitrogen, oxygen, silver, gold, tin, germanium, silicon or a mixed doping of the above elements.

Preferably, the phase-change storage material has a characteristic of reversible phase-change under the action of an external electric pulse.

Preferably, the phase-change memory material has two or more stable resistance states under external electric pulses.

Preferably, the phase-change memory material has a resistivity ratio of at least 4 in the amorphous state and in the crystalline state.

Preferably, the reflectivity of the phase-change storage material can undergo reversible changes under the action of laser pulses.

The present invention also includes a method for preparing a phase-change memory material. The preparation method includes any one of the following methods: (1) Two-target magnetron co-sputtering using a GaSb alloy target and a Sb _x Se alloy target, wherein 1 <x<8; (2) Using GaSb, Sb ₂ Se ₃ and Sb three-target magnetron co-sputtering.

Preferably, two-target magnetron co-sputtering of a GaSb alloy target and a Sb ₂ Se ₃ alloy target is used.

Compared with the commonly used GST, the gallium-antimony-selenium phase change thin film material of the invention has better thermal stability, faster crystallization speed and stronger data retention. At the same time, the material system does not contain the toxic element Te, so it is an environmentally friendly material that does not pollute semiconductor equipment, facilitates the processing and manufacturing of subsequent processes, and is better compatible with CMOS processes.

The preparation method of the phase-change memory material provided by the invention has simple process, is convenient for precise control of material composition and subsequent process, is beneficial to stable composition, shortens memory production cycle, and saves cost.

The invention provides that the phase-change memory material is applied to the phase-change memory, so that the phase-change memory has the advantages of strong data retention, fast erasing and writing speed, low power consumption, stable electrical performance, and the like.

Description of drawings

Fig. 1 is a schematic structural diagram of a phase-change memory cell;

Fig. 2 is the resistance-temperature relation figure of described phase-change storage material Ga-Sb-Se;

Fig. 3 is the calculation result diagram of the activation energy of the phase change memory material Ga-Sb-Se;

Fig. 4 is the calculation result figure of the data retention ability of described phase-change storage material Ga-Sb-Se;

FIG. 5 is a resistance-voltage relationship diagram of a Ga-Sb-Se phase change memory.

Detailed ways

The invention will be described in detail below through specific examples.

Embodiment one

Please refer to FIG. 1 , a phase-change memory cell with a vertical structure, the phase-change memory cell includes a lower electrode 1, a phase-change memory material layer 2 on the lower electrode 1, and a transition layer on the phase-change memory material layer 2 3 and the upper electrode 4 located on the transition layer 3; the lower electrode 1 is surrounded by an insulating medium 5.

The phase-change storage material layer 2 is a phase-change thin film material, which is selected from the gallium-antimony-selenium (Ga-Sb-Se) compound provided by the present invention. As a storage medium, it is the core of the phase change memory unit. Wherein, the lower electrode 1 and the upper electrode 4 can be selected from Al, Ti, W, graphite, TiN, Cu, TiW or other conductive materials. The transition layer 3 can be TiN or TaN, and its thickness is about 10-30 nanometers. Preferably 20 nm. The insulating layer 5 can be SiO ₂ or Si ₃ N ₄ material.

The Ga-Sb-Se compound of the present invention, as a phase-change thin film material, can also be used in a phase-change memory unit with a lateral structure.

The phase-change storage material Ga-Sb-Se described in the present invention can be prepared by multi-target co-sputtering, and its composition ratio can be obtained by adjusting the corresponding power of different targets. The Ga-Sb-Se can also be prepared by chemical vapor deposition, atomic layer deposition (ALD), electron beam evaporation and other methods, and can also obtain the required atomic ratio of Ga by ion implanting element Ga in the Sb-Se film. - Sb-Se material.

Embodiment two

The phase-change storage material gallium-antimony-selenium (Ga-Sb-Se) compound provided by the present invention has a chemical composition of Ga _{x Sby Sez} , wherein 4<x<40, 25<y<85, 5<z <70, x+y+z=100.

When it is used in a phase-change memory unit with a vertical structure, the lower electrode 1 and the upper electrode 4 can be made of Al, Ti, W, graphite, TiN, Cu, TiW or other conductive materials. The transition layer 3 can be TiN or TaN, and its thickness is about 10-30 nanometers. Preferably 20 nm. The insulating layer 5 can be SiO ₂ or Si ₃ N ₄ material.

The phase-change storage material Ga-Sb-Se described in the present invention can be prepared by multi-target co-sputtering. The process parameters of two-target magnetron co-sputtering using GaSb alloy target and Sb ₂ Se ₃ (or Sb _x Se, 1<x<8) alloy target include: background vacuum degree is less than 2×10 ^-4 Pascal, sputtering pressure 0.18 Pascal to 0.25 Pascal, the sputtering gas is argon, the temperature is room temperature, the RF power applied to the GaSb alloy target is 10 watts to 45 watts, and the power applied to Sb ₂ Se ₃ (or Sb _x Se, 1<x< 8) The power of the radio frequency power supply on the target is 8 watts to 40 watts, the sputtering time is 20 minutes to 60 minutes, and the thickness of the deposited film is 50 nanometers to 200 nanometers.

Embodiment three

Preferably, the phase-change storage material gallium-antimony-selenium (Ga-Sb-Se) compound provided by the present invention has a chemical composition of Ga _x Sb _{y Sez} , wherein, 10≤x≤20, 50≤y≤ 85, 20≤z≤40, x+y+z=100.

The present invention also includes a method for preparing a phase-change memory material. The preparation method includes any one of the following methods: (1) Two-target magnetron co-sputtering using a GaSb alloy target and a Sb _x Se alloy target, wherein 1 <x<8; (2) Using GaSb, Sb ₂ Se ₃ and Sb three-target magnetron co-sputtering.

Embodiment four

Preferably, the present invention provides that the specific composition of the phase change memory material Ga-Sb-Se is Ga ₈ Sb ₃₄ Se ₅₈ , Ga ₁₃ Sb ₃₂ Se ₅₅ or Ga ₃₄ Sb ₄₀ Se ₂₆ .

Preferably, the present invention adopts two-target magnetron co-sputtering of GaSb alloy target and Sb ₂ Se ₃ alloy target.

In addition, in the process of preparing the phase-change memory material, the compound of gallium-antimony-selenium also includes doping atoms, and the molar ratio of the doping atoms is 0% to 20%. Specifically, the doping atoms are one of aluminum, bismuth, nitrogen, oxygen, silver, gold, tin, germanium, silicon or a mixed doping of the above elements.

The gallium-antimony compound, which is a phase-change memory material, has the characteristic of reversible phase transition under the action of an external electric pulse or light pulse, and the resistivity ratio between the amorphous state and the crystalline state is at least 4.

Optionally, the phase-change memory material has two or more stable resistance states under external electric pulses.

The preparation method of the phase-change storage material provided by the invention has simple process and is convenient for precise control of material composition and subsequent process.

The Ga-Sb-Se phase-change thin film material provided by the present invention is not limited to the phase-change memory structure shown in Figure 1, and all kinds of cell structures (such as lateral structures) that are used for phase-change memory can be used, including utilizing this The invention provides Ga-Sb-Se phase-change thin film materials with resistance difference between crystalline state and amorphous state to realize other functional devices for storage.

Various tests have been carried out to prepare the described phase change memory thin film Ga-Sb-Se and the phase change memory unit using Ga-Sb-Se of the present invention as storage medium on the semiconductor substrate, to evaluate the phase change memory material. Change characteristics, including crystallization temperature, thermal stability, data retention, and performance of phase change memory.

Fig. 2 is a diagram of the resistance-temperature relationship of the phase-change memory material Ga-Sb-Se. It can be seen from the figure that the crystallization temperature of the phase change memory material Ga-Sb-Se is between 230-310°C, which is higher than that of GST (about 140°C). When the antimony content is constant, the crystallization temperature of the phase change memory material increases with the increase of the GaSe ratio. Therefore, the crystallization temperature of the phase-change memory material Ga-Sb-Se can be conveniently controlled by adjusting the ratio of gallium-selenide content.

As shown in FIG. 3 , the activation energy of the phase change memory material Ga—Sb—Se is obtained from the resistance-temperature relationship at different heating rates. The activation energy of the phase-change memory material Ga-Sb-Se increases with the increase of the gallium-selenium ratio, ranging from 4.06 to 5.52eV, which is obviously higher than that of GST (2.20eV). The high crystallization temperature and activation energy fully demonstrate that the thermal stability of the phase-change memory material Ga-Sb-Se is better than that of GST, so problems such as crosstalk in GST memories can be avoided. The 10-year data retention of the phase-change memory material Ga-Sb-Se also increases with the increase of the GaSe ratio.

As shown in Figure 4. The 10-year data maintains a temperature range between 159 and 230°C, which is at least 70°C higher than GST (88°C). The strong data retention capability enables the phase-change memory material Ga-Sb-Se to be used in high-temperature special occasions, such as automotive electronics, embedded storage, and the like. The phase-change memory material Ga-Sb-Se was prepared into a memory cell as shown in FIG. 1 , and the resistance-voltage relationship of the phase-change memory was obtained through testing.

As shown in Figure 5. Under the application of electric pulses, the phase change memory realizes reversible phase change, and the RESET voltage (the voltage corresponding to returning from low resistance to high resistance) is relatively low, so the power consumption of the device is relatively low. For example, under the electric pulse of 200 nanoseconds, the phase change memory can be obtained to realize "erase" (high resistance to low resistance) and "write" (low resistance to high resistance) operation at 1.4 and 3V respectively. The RESET voltage of the phase-change memory is lower than that of GST (3.5V for 500 nanoseconds), indicating that the phase-change memory has lower power consumption. In terms of phase change speed, the phase change memory can complete the "erasing window" of the phase change memory under the electric pulse of 50 nanoseconds, which is far lower than the "erasing window" of 500 nanoseconds usually reported by GST phase change memory. . Therefore, the phase change memory has obvious advantages in terms of power consumption and speed compared with the GST phase change memory.

In summary, compared with general storage materials, the phase change storage material Ga-Sb-Se compound provided by the present invention, wherein 4<x<40, 25<y<85, 5<z<70, x+y +z=100, good thermal stability, strong data retention ability, and adjustable physical properties; in addition, the phase change storage material Ga-Sb-Se does not contain easily polluting element Te, which is environmentally friendly and does not easily pollute semiconductor process equipment , for subsequent processing.

The preparation method of the phase-change storage material provided by the invention has simple process and is convenient for precise control of material composition and subsequent process.

The phase change memory prepared by using the phase change memory material Ga-Sb-Se has the advantages of low power consumption, fast operation speed, stable electrical performance and the like.

It can be understood that although the present invention has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or be modified to be equivalent to equivalent changes. Example. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, which do not deviate from the technical solution of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims (8)

1. A phase-change storage material, characterized in that, the phase-change storage material is a compound of gallium-antimony-selenium; Its chemical composition is Ga _x Sb _y Se _z , where x=34, y=40, z=26. 2 . The phase-change memory material according to claim 1 , wherein the gallium-antimony-selenium compound has certain segregation in composition when the thin film is prepared, and the error of segregation elements is within 10%. 3 . The phase-change memory material according to claim 1 , wherein the gallium-antimony-selenium compound further includes doping atoms, and the molar ratio of the doping atoms is 0% to 20%. 4. The phase-change memory material according to claim 3, wherein the dopant atom is one of aluminum, bismuth, nitrogen, oxygen, silver, gold, tin, germanium, silicon, or an element of the above-mentioned elements mixed doping. 5. The phase change memory material according to claim 1, characterized in that the phase change memory material has a characteristic of reversible phase change under the action of an external electric pulse. 6. The phase-change memory material according to claim 1, wherein the phase-change memory material has two or more stable resistance states under an external electric pulse. 7. The phase-change memory material according to claim 1, wherein the resistivity ratio between the amorphous state and the crystalline state of the phase-change memory material is at least 4. 8. The phase-change memory material according to claim 1, wherein the reflectivity of the phase-change memory material can change reversibly under the action of laser pulses.