CN111211221B

CN111211221B - High-stability low-power-consumption Hf-Ge-Sb nano phase change film and preparation method and application thereof

Info

Publication number: CN111211221B
Application number: CN202010015582.6A
Authority: CN
Inventors: 翟继卫; 华思聪; 沈波
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2020-01-07
Filing date: 2020-01-07
Publication date: 2021-12-07
Anticipated expiration: 2040-01-07
Also published as: CN111211221A

Abstract

The invention relates to a high-stability low-workHf-Ge-Sb nano phase change film and preparation method and application thereof, wherein the chemical general formula of the nano phase change film is Hf_x(Ge₅Sb₉₅)_1‑x(0<x<0.3); the preparation method comprises the step of carrying out magnetron sputtering on Ge₅Sb₉₅The alloy material and the Hf material are compounded in nanometer level on the substrate to form Hf_x(Ge₅Sb₉₅)_1‑x(0<x<0.3) a nano phase change film; the prepared nano phase change film can be used for preparing a phase change memory. Compared with the prior art, the nanometer phase change film is environment-friendly, does not contain toxic element Te, has higher crystallization temperature, crystallization activation energy and larger crystalline resistance, simultaneously keeps nanosecond-level phase change time, and is beneficial to realizing the PCRAM with high stability and low power consumption storage.

Description

High-stability low-power-consumption Hf-Ge-Sb nano phase change film and preparation method and application thereof

Technical Field

The invention belongs to the technical field of microelectronic materials, and relates to a high-stability low-power-consumption Hf-Ge-Sb nano phase change film, and a preparation method and application thereof.

Background

The development of large data and the increasing number of processor cores place extremely high demands on the speed, capacity, power consumption and reliability of memory. The most widely used non-volatile memory at present is a Flash memory (Flash memory) based on floating gate technology. As the memory technology continues to be developed, the process size is further reduced, the microscopic characteristics of electrons become more and more obvious, and the traditional memory technology faces dilemma in terms of system stability, data reliability and other problems due to the factors such as the physical characteristic restriction of the device itself. In view of the above, semiconductor companies are developing new non-volatile Memory technologies following flash memories, such as Ferroelectric Random Access Memory (Fe RAM), Magnetic Random Access Memory (MRAM), Phase-change Random Access Memory (PCRAM), and the like. In contrast, PCRAM has faster read and write speeds, lower power consumption, and high erase and write times. At the same time, it is possible to overcome difficulties that cannot be overcome by several other memories: devices are simple in structure, small in size, and easy to scale down, thus having great potential in increasing storage density.

The phase change memory (PCRAM) is a novel non-volatile memory for realizing information storage based on phase change of substances, and the principle of the phase change memory mainly utilizes the huge resistance difference of chalcogenide compounds in amorphous and polycrystalline states as data '0' and '1' for data storage. The material has semiconductor characteristics in an amorphous state, and the resistance value of the material is high; in the crystalline state, the material behaves as a semimetal and has a low resistance value. The phase-change material can be reversibly switched between an amorphous state and a crystalline state under the action of a current thermal effect, so that repeated reading and writing of data are realized. The crystallization process from the high resistance state to the low resistance state is referred to as a SET transition process, and the amorphization process from the low resistance state to the high resistance state is referred to as a RESET transition process.

In PCRAM, the performance of the phase change material largely determines the performance of the memory. The memory is continuously developed towards high speed, high density, high stability, low power consumption, low cost, etc., and most important conditions to be satisfied by the phase change material are as follows:

1) the crystallization time is short: the crystallization process corresponds to the SET process of the device operation, and the operation time of the SET process determines the device read-write speed of the PCRAM;

2) the resistance difference between the crystalline state and the amorphous state is large: this is to ensure the device has higher data resolution and noise tolerance, resulting in distinguishing distinct logic states "0" and "1";

3) the amorphous has high thermal stability: the higher the amorphous state thermal stability of the material is, the stronger the data retention capacity of the device at a certain temperature is, and the higher the reliability of the device is;

4) the volume change rate before and after phase change is small: the reliability of the device in the reversible cycle process is improved;

5) the micro-shrinkage performance is good: this requires that the material components be as simple as possible, and that the material properties have a high tolerance to component fluctuations and maintain good properties at nanometer dimensions to meet the requirements of PCRAM for high density and high reliability.

Most of materials meeting the phase change storage requirements belong to chalcogenide compounds of a Ge-Sb-Te ternary system. Different matrix materials often have unique advantages and disadvantages. For example, GeTe has good thermal stability in an amorphous state, but has a relatively slow crystallization rate; the Sb-rich Ge-Sb phase change material belongs to a crystal grain growth dominance type crystallization mechanism, the crystallization speed is high, but the amorphous state thermal stability is extremely poor, partial crystallization to complete crystallization exists at normal temperature, and the crystalline state resistance is to be further improved. The development of high density phase change memories and in some applications requiring high temperature require that the memory material have high thermal stability of the amorphous state to prevent reliability problems caused by crosstalk and data failure. Generally, researchers can make reasonable component adjustment or doping modification based on the phase change materials by utilizing the unique advantages of the phase change materials so as to meet the application requirements of high thermal stability, high operation speed, high storage density, low operation power consumption and the like. The Chinese patent CN107359238A introduces Ti atoms into Ge-Sb based phase change material, inhibits crystallization process, reduces grain size, and further improves film data retention and crystalline resistivity, thereby realizing application requirements of high thermal stability and low power consumption. Kim and the like improve the crystallization temperature and crystalline resistivity of the thin film by doping Se atoms in the Ge-Sb based phase change material, thereby achieving the aims of high thermal stability and low power consumption.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a high-stability low-power-consumption Hf-Ge-Sb nanometer phase-change film, a preparation method and application thereof, which are used for solving the problems of crosstalk and data failure caused by poor amorphous state thermal stability of a phase-change storage material.

The purpose of the invention can be realized by the following technical scheme:

a high-stability low-power consumption Hf-Ge-Sb nano phase-change film is a Ge phase-change film doped with a metal element Hf₅Sb₉₅The chemical composition of the nano phase change film conforms to the chemical general formula Hf_x(Ge₅Sb₉₅)_1-xWherein x is the atomic percentage of metal Hf element and 0<x<0.3。

As a preferable technical scheme, the selection range of x is 0.02< x ≦ 0.28.

Furthermore, the thickness of the nanometer phase change film is 20-200 nm.

High melting point metals generally have a better effect in raising the crystallization temperature of phase change materials. Hafnium (Hf), an element commonly used in industry, isThe melting point of the simple substance metal reaches 2233 ℃ which is higher than that of Ti metal (1668 ℃) doped in CN107359238A, therefore, the Hf has more obvious effect on improving the phase change stability of the film by doping the same content of elements. By doping metal Hf atoms into the nano phase-change film, the crystallization process is inhibited, the crystallization temperature and the crystallization activation energy are improved, and the phase-change film can be crystallized only by needing more energy, so that the amorphous thermal stability is obviously improved, and the nano phase-change film is suitable for high-temperature occasions. After metal Hf is doped, the grain size is obviously reduced, so that the grain boundary is obviously increased, the carrier scattering is increased, the crystalline resistivity is obviously improved, the RESET operation current is favorably reduced, and the operation power consumption is reduced. In addition, the electronegativity of the Hf element is weaker than that of the Ti element, so that the Hf element can easily replace the Sb element in the nano phase change film to be oxidized, the oxidation of the Sb element can be effectively inhibited by the existence of the Hf element, and the phase change reliability of the film is improved. Thus, by doping with metallic Hf atoms, Ge is allowed to grow₅Sb₉₅The phase change film becomes a phase change material which has comprehensive excellent performances of high phase change speed, high stability, low operation power consumption and the like, and has good market application prospect.

In the high-stability low-power-consumption Hf-Ge-Sb nanometer phase-change film, if the atomic percent x value of Hf element is too high, the film material loses the phase-change capability and the phase-change performance is deteriorated. If the value range of the atomic percent x of the Hf content is less than 0.02, the crystal activation energy and the crystal resistance of the phase-change film are not obviously improved, the thermal stability is not excellent enough, and when the Hf content is applied to a phase-change memory, the performance of the device needs to be further improved.

The preparation method of the high-stability low-power-consumption Hf-Ge-Sb nanometer phase-change film comprises the following steps of: ge by magnetron sputtering₅Sb₉₅The alloy material and the Hf material are compounded on the substrate in a nanometer order to form Hf_x(Ge₅Sb₉₅)_1-x(0<x<0.3) nanometer phase change film.

Further, the substrate is SiO after cleaning and drying₂a/Si (100) substrate;

the SiO₂Of a/Si (100) substrateThe cleaning and drying process comprises the following steps: mixing SiO₂the/Si (100) substrate is sequentially placed in an ethanol solution, an acetone solution and deionized water and is respectively subjected to ultrasonic cleaning; then sequentially carrying out high-purity nitrogen blow-drying and high-temperature drying processes to obtain clean and dried SiO₂a/Si (100) substrate.

The SiO₂The cleaning and drying process of the/Si (100) substrate specifically comprises the following steps:

a1, mixing SiO₂Putting the/Si (100) substrate into an ethanol solution, and ultrasonically cleaning for 10-20min to remove dust particles and inorganic impurities on the surface of the substrate;

a2, SiO washed with ethanol₂Putting the/Si (100) substrate into an acetone solution, and ultrasonically cleaning for 10-20min to remove organic impurities on the surface of the substrate;

a3, washing acetone to obtain SiO₂Putting the/Si (100) substrate into deionized water, ultrasonically cleaning for 10-20min, and cleaning the surface again;

a4, washing SiO with deionized water₂Drying the surface and the back of the/Si (100) substrate by high-purity nitrogen, and placing the substrate in a drying oven for standby drying to obtain clean and dried SiO₂a/Si (100) substrate.

Preferably, the ultrasonic time in the step A1), the step A2), the step A3) and the step A4) is 15 min.

Further, in the magnetron sputtering method, the target material comprises Ge stacked from bottom to top₅Sb₉₅Alloy target and Hf target.

Further, the Ge is₅Sb₉₅The alloy target is a circular target, the Hf target is a fan-shaped target, and the Ge is₅Sb₉₅The alloy target and the Hf target are concentrically arranged.

Further, the radius of the Hf target material is 10-15mm, the thickness is 2-4mm, and the central angle is 20-40 degrees;

when Ge is present₅Sb₉₅When at least two Hf targets are arranged on the alloy target, the Hf targets are uniformly distributed at equal included angles.

Preferably, the radius of the Hf target material is 12.5mm, the thickness is 3mm, and the central angle is 30 degrees.

Furthermore, in the magnetron sputtering method, the used sputtering gas is argon, the flow rate of the sputtering gas is 20-40SCCM, the pressure of the sputtering gas is 0.1-0.3Pa, and the sputtering power is 10-30W.

Preferably, the flow rate of the sputtering gas is 30SCCM, the pressure of the sputtering gas is 0.2Pa, and the sputtering power is 20W.

Furthermore, in the magnetron sputtering method, the sputtering speed is 3-10s/nm, and the sputtering time is 100-1000 s.

The magnetron sputtering method is specifically a same-target double-target co-sputtering method, and comprises an early preparation stage and a preparation stage, wherein the early preparation stage comprises the following steps:

b1, converting circular Ge₅Sb₉₅The alloy target is arranged on the target position of a sputtering instrument and is positioned on the circular Ge₅Sb₉₅Placing a fan-shaped Hf target material on the alloy target material, enabling the circle centers of the alloy target material and the Hf target material to coincide, and removing dust particles on the surface of the target material by using an ear washing ball;

b2, cleaning the dried SiO₂Fixing the/Si (100) substrate in the center of the sample tray, closing the cavity of the sputtering instrument, and closing the vent valve to seal the cavity of the sputtering instrument;

b3, starting a vacuum gauge and a mechanical pump to vacuumize the cavity of the sputtering instrument, simultaneously opening circulating water, starting a molecular pump when the vacuum degree in the cavity reaches 10Pa or below, opening a gate valve, and vacuumizing to 2 multiplied by 10^-4Pa below;

b4, using high-purity Ar gas as sputtering gas, setting the flow rate of Ar gas to be 20-40SCCM, and keeping the gas pressure to be 0.1-0.3Pa during sputtering;

b5, sputtering the target by using a radio frequency power supply, wherein the sputtering power is 10-30W.

The preparation stage comprises: monitoring the whole coating process by using upper computer software, setting the sputtering time to be 100-1000s and the sputtering speed of the target material to be 3-10s/nm, and rotating the substrate to Ge₅Sb₉₅(Hf) target position, starting radio frequency power supply, and starting at SiO₂Sputtering on a Si (100) substrate to obtain Hf in the form of 20-200nm deposit_x(Ge₅Sb₉₅)_1-x(0<x<0.3) alloy film, and after the sputtering is finished, closing Ge₅Sb₉₅(Hf) radio frequency power supply of target site.

The high-stability low-power-consumption Hf-Ge-Sb nano phase change film can be applied to a phase change memory, and the high resistivity of the nano phase change film in an amorphous state and the low resistivity of the nano phase change film in a crystalline state are utilized to realize the state recording of data of '0' and '1'.

Compared with the prior art, the invention has the following characteristics:

1) the Hf-Ge-Sb nanometer phase change film material has higher crystallization temperature and crystallization activation energy, and is beneficial to realizing the PCRAM with high thermal stability;

2) the Hf-Ge-Sb nanometer phase change film material has higher crystalline resistance and is beneficial to realizing the PCRAM with low operation power consumption;

3) the fluctuation of the film volume before and after the crystallization of the Hf-Ge-Sb nano phase change film material is small, and the PCRAM with good reliability is favorably realized

4) The Hf-Ge-Sb nano phase change film material does not contain toxic element Te, is environment-friendly, is compatible with the existing CMOS manufacturing process, and can realize low-cost manufacture

5)Hf_x(Ge₅Sb₉₅)_1-x(0<x<0.3) has nanosecond-level phase change time as a phase change film material, and has great potential in the aspect of preparing PCRAM with high thermal stability, low operation power consumption and high reliability.

Drawings

FIG. 1 shows Hf in example 4_x(Ge₅Sb₉₅)_1-x(x＝0.07，0.14，0.28)、Ge₅Sb₉₅A relation curve diagram of the in-situ resistance and the temperature of the nano phase change film;

FIG. 2 shows Hf in example 5_x(Ge₅Sb₉₅)_1-x(x＝0.07，0.14，0.28)、Ge₅Sb₉₅The nanometer phase change film Kissinger fits the obtained crystallization activation energy diagram;

FIG. 3 shows Hf in example 6_x(Ge₅Sb₉₅)_1-x(x＝0.07，0.14，0.28)、Ge₅Sb₉₅XRD pattern of nano phase change film in crystalline state;

FIG. 4 shows Hf in example 6_x(Ge₅Sb₉₅)_1-xA relation graph of a nanometer phase change film Sb phase diffraction peak (003) FWHM, a grain size and Hf content;

FIG. 5 shows Hf at different annealing temperatures in example 7_0.14(Ge₅Sb₉₅)_0.86An XRD pattern of (a);

FIG. 6 is a graph of Hf at different annealing temperatures in example 7_0.14(Ge₅Sb₉₅)_0.86The FWHM of the Sb phase diffraction peak (003), the grain size and the annealing temperature of (1);

FIG. 7 shows Hf in example 8_0.14(Ge₅Sb₉₅)_0.86With Ge₅Sb₉₅XRR diffraction patterns of the nano phase change film before and after crystallization;

FIG. 8 shows Hf in example 8_0.14(Ge₅Sb₉₅)_0.86With Ge₅Sb₉₅A modified Bragg equation fitting curve graph of the nano phase change film before and after crystallization;

FIG. 9 shows Hf base in example 9_0.14(Ge₅Sb₉₅)_0.86And Ge₅Sb₉₅I-V characteristic curve diagram of PCRAM device unit of the nanometer phase change film;

FIG. 10 shows Hf-based results in example 9_0.14(Ge₅Sb₉₅)_0.86And Ge₅Sb₉₅R-V characteristic curve chart of PCRAM device unit of nanometer phase change film.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

Phase change thin film Ge of comparative example and example below₅Sb₉₅And Hf_x(Ge₅Sb₉₅)_1-x(0<x<0.3) thickness by observing the cross section with a field emission Scanning Electron Microscope (SEM)Phase change film Hf_x(Ge₅Sb₉₅)_1-xThe atomic percent of the middle Hf element is obtained by analysis of an X-ray energy spectrometer.

Comparative example:

the chemical composition of the Ge-Sb nanometer phase change film not doped with the metal Hf element in the comparative example is Ge₅Sb₉₅The thickness of the film is 50nm, and the preparation method comprises the following steps:

1) cleaning SiO₂the/Si (100) substrate is dried to remove dust particles, organic and inorganic impurities attached to the surface;

1-1) SiO₂Putting the Si (100) substrate into an ethanol solution, and ultrasonically cleaning for 15 minutes to remove dust particles and inorganic impurities on the surface of the substrate;

1-2) placing the substrate cleaned by the ethanol into an acetone solution, and ultrasonically cleaning for 15 minutes to remove organic impurities on the surface of the substrate;

1-3) placing the substrate cleaned by acetone into deionized water, cleaning for 15 minutes by using ultrasonic waves, and cleaning the surface again;

1-4) drying the surface and the back of the substrate cleaned by the deionized water by using high-purity nitrogen, and placing the substrate in a drying box for later use;

2) preparing Ge by magnetron sputtering method₅Sb₉₅Early preparation of the phase change film:

2-1) reacting Ge₅Sb₉₅Placing the alloy target material on a target position of a sputtering instrument, and removing dust particles on the surface of the target material by using an aurilave;

2-2) cleaning and drying the SiO₂Fixing the/Si (100) substrate in the center of the sample tray, closing the cavity of the sputtering instrument, and closing the vent valve to seal the cavity of the sputtering instrument;

2-3) starting a vacuum gauge and a mechanical pump to vacuumize, simultaneously opening circulating water, starting a molecular pump when the vacuum degree in a cavity of the sputtering instrument reaches 10Pa or below, opening a gate valve, and vacuumizing to 2 multiplied by 10^-4Pa below;

2-4) using high-purity Ar gas as sputtering gas, setting the flow of Ar gas as 30SCCM, and keeping the gas pressure at 0.2Pa during sputtering;

2-5) sputtering the target material by using a radio frequency power supply, wherein the sputtering power is 20W;

3) monitoring the whole coating process by using upper computer software, setting the sputtering time to be 290s, the sputtering speed of the target material to be 5.8s/nm, and rotating the substrate to Ge₅Sb₉₅Target position, turn on the radio frequency power supply, at SiO₂Sputtering 290s on a/Si (100) substrate to obtain Ge in a 50nm deposited state₅Sb₉₅Alloy film, after sputtering is finished, Ge is closed₅Sb₉₅A radio frequency power source for the target site.

Example 1:

in the present embodiment, the chemical composition of the Hf-Ge-Sb nano phase change film is Hf_0.07(Ge₅Sb₉₅)_0.93The film thickness is 50nm, and the preparation method is as follows:

2) preparing Hf by adopting magnetron sputtering method_0.07(Ge₅Sb₉₅)_0.93Early preparation of the phase change film:

2-1) using the same target position double-target material co-sputtering method to form the circular Ge₅Sb₉₅The alloy target is placed on the target position of the sputtering instrument and is positioned on the circular Ge₅Sb₉₅1 fan-shaped Hf target material with the radius of 12.5mm, the thickness of 3mm and the central angle of 30 degrees is placed on the alloy target material to ensure that the Ge is round₅Sb₉₅The center of the alloy target material is coincided with the center of the sector Hf target material, and dust particles on the surface of the target material are removed by an ear washing ball;

2-5) sputtering the target material by adopting a radio frequency power supply, wherein the sputtering power is 20W.

3) Monitoring the whole coating process by using upper computer software, setting the sputtering time to be 290s, the sputtering speed of the target material to be 5.8s/nm, and rotating the substrate to Ge₅Sb₉₅(Hf) target position, starting radio frequency power supply, and starting at SiO₂Sputtering 290s on a/Si (100) substrate to obtain Hf in the 50nm as-deposited_0.07(Ge₅Sb₉₅)_0.93Alloy film, after sputtering is finished, Ge is closed₅Sb₉₅(Hf) radio frequency power supply of target site.

Hf prepared by magnetron sputtering method in this example_0.07(Ge₅Sb₉₅)_0.93The phase change film is applied to a PCRAM device, and data storage is realized by utilizing high resistivity of the phase change film in an amorphous state and low resistivity of the phase change film in a crystalline state.

Example 2:

in the present embodiment, the chemical composition of the Hf-Ge-Sb nano phase change film is Hf_0.14(Ge₅Sb₉₅)_0.86The thickness of the film is 50nm, and the preparation method comprises the following steps:

2) preparing Hf by adopting magnetron sputtering method_0.14(Ge₅Sb₉₅)_0.86Early preparation of the phase change film:

2-1) using the same target position double-target material co-sputtering method to form the circular Ge₅Sb₉₅The alloy target is placed on the target position of the sputtering instrument and is positioned on the circular Ge₅Sb₉₅Symmetrically placing 2 fan-shaped Hf targets with the radius of 12.5mm, the thickness of 3mm and the central angle of 30 degrees on the alloy target to ensure that the Ge is circular₅Sb₉₅The center of the alloy target material is coincided with the center of the sector Hf target material, and dust particles on the surface of the target material are removed by an ear washing ball;

2-3) starting a vacuum gauge and a mechanical pump to vacuumize, simultaneously opening circulating water, starting a molecular pump when the vacuum degree in the cavity reaches 10Pa or below, opening a gate valve, and vacuumizing to 2 multiplied by 10^-4Pa below;

2-4) sputtering the target material by adopting a radio frequency power supply, wherein the sputtering power is 20W.

3) Monitoring the whole coating process by using upper computer software, setting the sputtering time to be 290s, the sputtering speed of the target material to be 5.8s/nm, and rotating the substrate to Ge₅Sb₉₅(Hf) target position, starting radio frequency power supply, and starting at SiO₂Sputtering 290s on a/Si (100) substrate to obtain Hf in the 50nm as-deposited_0.14(Ge₅Sb₉₅)_0.86Alloy film, after sputtering is finished, Ge is closed₅Sb₉₅(Hf) radio frequency power supply of target site.

Hf prepared by magnetron sputtering method in this example_0.14(Ge₅Sb₉₅)_0.86The phase change film is applied to a PCRAM device, and data storage is realized by utilizing high resistivity of the phase change film in an amorphous state and low resistivity of the phase change film in a crystalline state.

Example 3:

in the present embodiment, the chemical composition of the Hf-Ge-Sb nano phase change film is Hf_0.28(Ge₅Sb₉₅)_0.72The thickness of the film is 50nm, and the preparation method comprises the following steps:

2) preparing Hf by adopting magnetron sputtering method_0.28(Ge₅Sb₉₅)_0.72Early preparation of the phase change film:

2-1) using the same target position double-target material co-sputtering method to form the circular Ge₅Sb₉₅The alloy target is placed on the target position of the sputtering instrument and is positioned on the circular Ge₅Sb₉₅Evenly placing 4 fan-shaped Hf target materials with the radius of 12.5mm, the thickness of 3mm and the central angle of 30 degrees on the alloy target material at equal included angles to ensure that the Ge is round₅Sb₉₅The center of the alloy target material is coincided with the center of the sector Hf target material, and dust particles on the surface of the target material are removed by an ear washing ball;

2-2) cleaning and drying the SiO₂Fixing the/Si (100) substrate in the center of the sample tray, closing the cavity of the sputtering instrument, closing the vent valve to ensure that the cavity of the sputtering instrumentSealing the body;

2-3) starting a vacuum meter and a mechanical pump for vacuumizing, simultaneously opening circulating water, starting a molecular pump when the vacuum degree in the cavity reaches 10Pa or below, opening a gate valve, and vacuumizing to below 2 x 10 < -4 > Pa;

3) Monitoring the whole coating process by using upper computer software, setting the sputtering time to be 290s, the sputtering speed of the target material to be 5.8s/nm, and rotating the substrate to Ge₅Sb₉₅(Hf) target position, starting radio frequency power supply, and starting at SiO₂Sputtering 290s on a/Si (100) substrate to obtain Hf in the 50nm as-deposited_0.28(Ge₅Sb₉₅)_0.72Alloy film, after sputtering is finished, Ge is closed₅Sb₉₅(Hf) radio frequency power supply of target site.

Hf prepared by the magnetron sputtering method_0.28(Ge₅Sb₉₅)_0.72The phase change film is applied to a PCRAM device, and data storage is realized by utilizing high resistivity of the phase change film in an amorphous state and low resistivity of the phase change film in a crystalline state.

Example 4:

this example compares Ge prepared in comparative example₅Sb₉₅Phase change films and Hf prepared in examples 1-3, respectively_0.07(Ge₅Sb₉₅)_0.93、Hf_0.14(Ge₅Sb₉₅)_0.86、Hf_0.28(Ge₅Sb₉₅)_0.72And respectively testing to obtain the relationship curve of the in-situ resistance and the temperature of each phase-change film material, as shown in figure 1.

As shown in FIG. 1, is Hf_0.07(Ge₅Sb₉₅)_0.93、Hf_0.14(Ge₅Sb₉₅)_0.86、Hf_0.28(Ge₅Sb₉₅)_0.72Nano phase change film and Ge for comparison₅Sb₉₅Temperature rise of the curve of the in-situ resistance of the phase change material along with the change of temperatureThe rates are all 10 ℃/min. Wherein the undoped film has a crystallization temperature of about 125 deg.C, and the crystallization temperature is increased to 145 deg.C after 7 at.% of Hf element, indicating Ge₅Sb₉₅The amorphous stability of the film after the Hf is doped is improved, and the data retention capability of the device is improved. With continued incorporation of Hf, Ge₅Sb₉₅The amorphous resistance and the crystalline resistance of the film are both obviously improved. For the device, under the condition of the same pulse width, the higher resistivity is beneficial to realizing the efficient transmission of energy in the reversible phase transition process of the film by ensuring that the phase-change film reaches certain energy (crystallization or melting energy), thereby reducing the programming current of the device. In addition, before and after the crystallization of the film, the resistance on-off ratio of amorphous and crystalline states is kept at 10²The above is sufficient for storage of information data. It can be seen that the incorporation of Hf impurity does not affect Ge₅Sb₉₅Logical identification of thin films

Example 5:

this example compares Ge prepared in comparative example₅Sb₉₅Phase change films and Hf prepared in examples 1-3, respectively_0.07(Ge₅Sb₉₅)_0.93、Hf_0.14(Ge₅Sb₉₅)_0.86、Hf_0.28(Ge₅Sb₉₅)_0.72And respectively carrying out tests, and fitting by using a Kissinger equation to obtain the crystallization activation energy of each phase change film material, wherein the result is shown in FIG. 2.

As shown in FIG. 2 is Hf_0.07(Ge₅Sb₉₅)_0.93、Hf_0.14(Ge₅Sb₉₅)_0.86、Hf_0.28(Ge₅Sb₉₅)_0.72And Ge₅Sb₉₅And (3) fitting the obtained crystallization activation energy to the nano phase change film Kissinger. As can be seen, Ge₅Sb₉₅The crystallization activation energy E of the film is increased along with the increase of the atomic percent of the Hf doping_aGradually becoming larger, lifting from undoped 1.75eV to Hf_0.28(Ge₅Sb₉₅)_0.722.32eV of film. E_aHigher values indicate that more energy must be supplied to induce crystallization of the film. Non-of phase-change filmsThe crystallization temperature and crystallization activation energy are generally used for judging the crystallization thermal stability. Higher crystallization temperatures and crystallization activation energies have stronger data retention.

Example 6:

this example compares Ge prepared in comparative example₅Sb₉₅Phase change films and Hf prepared in examples 1-3, respectively_0.07(Ge₅Sb₉₅)_0.93、Hf_0.14(Ge₅Sb₉₅)_0.86、Hf_0.28(Ge₅Sb₉₅)_0.72The results of the X-ray diffraction test were shown in fig. 3 after annealing at 20 c higher than the crystallization temperature for 5 minutes, respectively.

As shown in FIG. 3 is Hf_0.07(Ge₅Sb₉₅)_0.93、Hf_0.14(Ge₅Sb₉₅)_0.86、Hf_0.28(Ge₅Sb₉₅)_0.72And Ge₅Sb₉₅And (3) annealing the nano phase change film at the temperature of 20 ℃ higher than the crystallization temperature for 5min, and then testing to obtain an XRD (X-ray diffraction) pattern. Undoped Ge₅Sb₉₅The film exhibited 2 characteristic diffraction peaks (003) and (006) which were normalized to the Rhombohedral Sb crystalline phase by comparison to a standard PDF card. Crystalline Hf with small amount of Hf element doped_0.07(Ge₅Sb₉₅)_0.93Still, a single Sb crystalline phase was exhibited, and no crystalline phase belonging to Hf or Ge was present. The characteristic diffraction peaks (003) and (006) broadened in peak form and weakened in intensity, indicating that the crystallization process of the film was suppressed and the grain size of the Sb phase became small.

To quantitatively evaluate Hf doping versus Ge₅Sb₉₅Effect of film grain size, taking diffraction peak (003) as an example, applying Scherrer formula to estimate Ge content of different Hf dopings₅Sb₉₅The grain size of the film is shown in FIG. 4.

As shown in FIG. 4, which is a graph of the FWHM value and the grain size of the Sb (003) plane as a function of the Hf dopant concentration, it can be seen that the grain size was reduced from the undoped 33.3nm to 11.7 nm. It can be seen that the grain size of the film is continuously decreasing with increasing Hf doping concentration.

Example 7:

this example is a Hf prepared in example 2_0.14(Ge₅Sb₉₅)_0.86The phase-change films were annealed at different annealing temperatures for 5 minutes and then subjected to X-ray diffraction test, and the results are shown in fig. 5.

As shown in FIG. 5 is Hf_0.14(Ge₅Sb₉₅)_0.86And (3) testing the obtained XRD pattern after the phase-change film is annealed for 5 minutes at different annealing temperatures. When the annealing temperature is 180 ℃, two obvious diffraction characteristic peaks appear on an XRD curve and belong to an Sb phase. As the annealing temperature increases, the intensity of the diffraction peak becomes stronger, indicating that the crystallinity of the phase-change film is higher. It can be seen that the phase structure change of the film is consistent with the R-T test results of fig. 1.

This example also examined the relationship between the FWHM value and the grain size of the Sb (003) plane and the Hf doping concentration by the same method as in example 6, and the results are shown in fig. 6. As can be seen, the grain size of the film is decreasing with increasing annealing temperature.

Example 8:

this example is a Hf prepared in example 2_0.14(Ge₅Sb₉₅)_0.86The phase-change thin film material is subjected to an X-ray Reflectivity test to obtain a relation curve of X-ray Reflectivity and an incident angle, as shown in FIG. 7.

As shown in FIG. 7 is Hf_0.14(Ge₅Sb₉₅)_0.86Phase change film as-deposited and annealed XRR patterns. As can be seen, the comparison of the as-deposited Hf_0.14(Ge₅Sb₉₅)_0.86For the film, after thermal annealing, the critical angle and the angle corresponding to the maximum or minimum strength of the film shift toward the high angle direction as a whole, indicating that the density of the film after crystallization increases and the volume shrinks accordingly.

To quantitatively evaluate the shrinkage of the film before and after crystallization, the thickness variation ratio of the film was calculated using the modified Bragg equation, and the result is shown in fig. 8. Hf can be calculated from the slope of the curve in FIG. 8_0.14(Ge₅Sb₉₅)_0.86Volume change before and after crystallization of thin filmThe conversion rate is only 2.37 percent, and the value is less than that of undoped Ge₅Sb₉₅3.49% of the film. The smaller density/volume change helps to improve the interfacial properties of the thin film with surrounding materials, further improving the device's cycling performance.

Example 9:

this example compares Ge prepared in comparative example₅Sb₉₅Phase change film and Hf prepared in example 2_0.14(Ge₅Sb₉₅)_0.86The phase change films are respectively manufactured into phase change memories and subjected to electrical performance tests to obtain I-V and R-V characteristic curves of the phase change memories, which are respectively shown in fig. 9 and 10.

Ge prepared in comparative example is shown in FIG. 9 and FIG. 10, respectively₅Sb₉₅Phase change film and Hf prepared in example 2_0.14(Ge₅Sb₉₅)_0.86I-V and R-V characteristic curves of a PCRAM device unit made of the phase change film.

The device presents a low-resistance SET state after threshold conversion, which indicates that the phase-change film has completed the conversion from the amorphous state to the crystalline state under the action of electricity. As can be seen from FIG. 9, Hf_0.14(Ge₅Sb₉₅)_0.86The threshold voltage of the film is 1.15V and is less than Ge₅Sb₉₅4.13V and thus has less operating power consumption.

When voltage pulse is applied, the device can obtain a stable U-shaped resistance window, namely reversible SET/RESET operation can be completed, the ratio of the resistance of high resistance state to the resistance of low resistance state exceeds two orders of magnitude, and a sufficient programming window is provided for identification of information storage state. As can be seen from FIG. 10, based on Hf_0.14(Ge₅Sb₉₅)_0.86SET and RESET voltages for thin film devices are less than Ge-based₅Sb₉₅Again, it is demonstrated that it has less operating power consumption. In addition, the device can realize stable reversible phase change under 50ns of electric pulse. Generally, the smaller the pulse width that can achieve reversible SET and RESET operations, the faster the programming speed of the device. It can be seen that based on Hf_0.14(Ge₅Sb₉₅)_0.86The thin film device has high switching speed, and is favorable for realizing high speedAnd (4) quick erasing operation.

By combining the analysis and test results in the embodiments 4-9, it can be known that the Hf-Ge-Sb nano phase change film of the invention has the advantages of good thermal stability, fast phase change speed, small volume change, low power consumption and the like, and has excellent comprehensive properties.

Example 10:

the high-stability low-power consumption Hf-Ge-Sb nano phase change film has the chemical general formula of Hf_0.21(Ge₅Sb₉₅)_0.79The thickness is 20nm, and the phase change memory can be applied to a phase change memory, and the data '0' and '1' state recording is realized by utilizing the high resistivity in an amorphous state and the low resistivity in a crystalline state.

The preparation method of the Hf-Ge-Sb nano phase change film comprises the following steps:

1) mixing SiO₂Putting the/Si (100) substrate into an ethanol solution, and ultrasonically cleaning for 10min to remove dust particles and inorganic impurities on the surface of the substrate;

2) cleaning the ethanol to obtain SiO₂Putting the/Si (100) substrate into an acetone solution, and ultrasonically cleaning for 10min to remove organic impurities on the surface of the substrate;

3) cleaning acetone to obtain SiO₂Putting the/Si (100) substrate in deionized water, ultrasonically cleaning for 10min, and cleaning the surface again;

4) cleaning the SiO with deionized water₂Drying the surface and the back of the/Si (100) substrate by high-purity nitrogen, and placing the substrate in a drying oven for standby drying to obtain clean and dried SiO₂a/Si (100) substrate;

5) mixing round Ge₅Sb₉₅The alloy target is arranged on the target position of a sputtering instrument and is positioned on the circular Ge₅Sb₉₅3 fan-shaped Hf targets are uniformly distributed at equal included angles on the alloy target, and the round Ge is enabled to be₅Sb₉₅The center of the alloy target coincides with the center of a fan-shaped Hf target, and dust particles on the surface of the target are removed by an ear washing ball, wherein the radius of the Hf target is 10mm, the thickness of the Hf target is 2mm, and the central angle of the Hf target is 20 degrees;

6) cleaning and drying the SiO₂Fixing the/Si (100) substrate in the center of the sample tray, closing the cavity of the sputtering instrument, and closing the vent valve to seal the cavity of the sputtering instrument;

7) starting a vacuum gauge and a mechanical pump to vacuumize the cavity of the sputtering instrument, simultaneously opening circulating water, starting a molecular pump when the vacuum degree in the cavity reaches 10Pa or below, opening a gate valve, and vacuumizing to 2 multiplied by 10^-4Pa below;

8) using high-purity Ar gas as sputtering gas, setting the flow rate of the Ar gas as 20SCCM, and keeping the gas pressure at 0.3Pa during sputtering;

9) sputtering the target material by using a radio frequency power supply, wherein the sputtering power is 10W;

10) monitoring the whole process of coating with upper computer software, setting sputtering time as 100s, sputtering speed of target as 3s/nm, and rotating the substrate to Ge₅Sb₉₅(Hf) target position, starting radio frequency power supply, and starting at SiO₂Sputtering of/Si (100) substrate to obtain Hf in the 20nm as-deposited_0.21(Ge₅Sb₉₅)_0.21Alloy film, after sputtering is finished, Ge is closed₅Sb₉₅(Hf) radio frequency power supply of target site.

Example 11:

the high-stability low-power consumption Hf-Ge-Sb nano phase change film has the chemical general formula of Hf_0.21(Ge₅Sb₉₅)_0.79The thickness is 200nm, and the phase change memory can be applied to a phase change memory, and the data '0' and '1' state recording is realized by utilizing the high resistivity in an amorphous state and the low resistivity in a crystalline state.

1) mixing SiO₂Putting the/Si (100) substrate into an ethanol solution, and ultrasonically cleaning for 20min to remove dust particles and inorganic impurities on the surface of the substrate;

2) cleaning the ethanol to obtain SiO₂Putting the/Si (100) substrate into an acetone solution, and ultrasonically cleaning for 20min to remove organic impurities on the surface of the substrate;

3) cleaning acetone to obtain SiO₂Putting the/Si (100) substrate in deionized water, ultrasonically cleaning for 20min, and cleaning the surface again;

4) cleaning the SiO with deionized water₂Drying the surface and the back of the/Si (100) substrate by high-purity nitrogen, and placing the substrate in a drying oven for drying to obtain clear liquidClean and dry SiO₂a/Si (100) substrate;

5) mixing round Ge₅Sb₉₅The alloy target is arranged on the target position of a sputtering instrument and is positioned on the circular Ge₅Sb₉₅3 fan-shaped Hf targets are uniformly distributed at equal included angles on the alloy target, and the round Ge is enabled to be₅Sb₉₅The center of the alloy target coincides with the center of a fan-shaped Hf target, and dust particles on the surface of the target are removed by an ear washing ball, wherein the radius of the Hf target is 15mm, the thickness of the Hf target is 4mm, and the central angle of the Hf target is 40 degrees;

8) using high-purity Ar gas as sputtering gas, setting the flow rate of Ar gas as 40SCCM, and keeping the gas pressure at 0.1Pa during sputtering;

9) sputtering the target material by using a radio frequency power supply, wherein the sputtering power is 10-30W;

10) monitoring the whole process of film coating by using upper computer software, setting the sputtering time to be 1000s, the sputtering speed of the target material to be 10s/nm, and rotating the substrate to Ge₅Sb₉₅(Hf) target position, starting radio frequency power supply, and starting at SiO₂Sputtering of a/Si (100) substrate to obtain Hf in the form of a 200nm deposit_0.21(Ge₅Sb₉₅)_0.79Alloy film, after sputtering is finished, Ge is closed₅Sb₉₅(Hf) radio frequency power supply of target site.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The high-stability low-power-consumption Hf-Ge-Sb nano phase-change film is characterized in that the chemical general formula of the nano phase-change film is Hf_x(Ge₅Sb₉₅)_1-xWherein x is the atomic percentage of metal Hf element and 0<x<0.3。

2. The Hf-Ge-Sb nano phase change film with high stability and low power consumption as claimed in claim 1, wherein the thickness of the nano phase change film is 20-200 nm.

3. The method for preparing the Hf-Ge-Sb nano phase change film with high stability and low power consumption as claimed in claim 1 or 2, wherein the method comprises the following steps: ge by magnetron sputtering₅Sb₉₅The alloy material and the Hf material are compounded on the substrate in a nanometer order to form Hf_x(Ge₅Sb₉₅)_1-x(0<x<0.3) nanometer phase change film.

4. The method for preparing the Hf-Ge-Sb nano phase-change film with high stability and low power consumption as claimed in claim 3, wherein the substrate is SiO after cleaning and drying₂a/Si (100) substrate;

the SiO₂The cleaning and drying process of the/Si (100) substrate comprises the following steps: mixing SiO₂the/Si (100) substrate is sequentially placed in an ethanol solution, an acetone solution and deionized water and is respectively subjected to ultrasonic cleaning; then sequentially carrying out high-purity nitrogen blow-drying and high-temperature drying processes to obtain clean and dried SiO₂a/Si (100) substrate.

5. The method for preparing the Hf-Ge-Sb nanometer phase change film with high stability and low power consumption as claimed in claim 3, wherein in the magnetron sputtering method, the target comprises Ge stacked from bottom to top₅Sb₉₅Alloy target and Hf target.

6. The method for preparing the Hf-Ge-Sb nano phase-change film with high stability and low power consumption as claimed in claim 5, wherein the Ge is₅Sb₉₅The alloy target is a circular target, the Hf target is a fan-shaped target, and the Ge is₅Sb₉₅The alloy target and the Hf target are concentrically arranged.

7. The method for preparing the Hf-Ge-Sb nanometer phase change film with high stability and low power consumption according to claim 6, wherein the radius of the Hf target material is 10-15mm, the thickness is 2-4mm, and the central angle is 20-40 degrees;

8. The method for preparing a high-stability low-power-consumption Hf-Ge-Sb nano phase-change film according to claim 3, wherein in the magnetron sputtering method, the sputtering gas used is argon, the flow rate of the sputtering gas is 20-40SCCM, the pressure of the sputtering gas is 0.1-0.3Pa, and the sputtering power is 10-30W.

9. The method as claimed in claim 3, wherein the sputtering rate is 3-10s/nm and the sputtering time is 100-1000 s.

10. The application of the high-stability low-power-consumption Hf-Ge-Sb nanometer phase-change film in the phase-change memory according to claim 1 or 2, wherein data recording is realized by utilizing the high resistivity of the nanometer phase-change film in an amorphous state and the low resistivity of the nanometer phase-change film in a crystalline state.