Selenium-germanium-antimony-tellurium-doped phase change target material and preparation method thereof

Abstract

The invention belongs to the technical field of target material preparation, and discloses a preparation method of a selenium-germanium-antimony-tellurium-doped phase change target material, which comprises the following steps: mixing selenium powder and germanium-antimony-tellurium alloy powder, homogenizing to obtain powder A, carrying out primary sintering on the powder A to obtain an intermediate alloy, crushing and sieving the intermediate alloy to obtain powder B, and finally carrying out secondary sintering on the powder B to obtain the selenium-germanium-antimony-tellurium-doped phase change target material. The secondary sintering is hot pressing sintering, the hot pressing sintering sequentially comprises a first stage, a second stage, a third stage and a fourth stage, the first stage is a pre-pressing stage, the second stage is a first heating and non-pressurization stage, the third stage is a second heating and non-pressurization stage, pressurization is started after the third stage is completed, and the fourth stage is a second heating and non-pressurization stage. By means of the design, the selenium-germanium-antimony-tellurium doped target material has the good density and the good component distribution uniformity degree at the same time, and in addition, the invention further discloses the selenium-germanium-antimony-tellurium doped phase change target material.

Description

Technical Field

[0001] The present application relates to the technical field of target material preparation, and in particular to a selenium-doped germanium-antimony-tellurium phase change target material and a preparation method thereof. Background Art

[0002] Phase change memory (PCRAM) has the advantages of long cycle life, low power, radiation resistance, fast reading, and simple manufacturing process. It is considered by the International Semiconductor Industry Association to be the most likely mainstream memory product to replace Flash in the future and has broad market prospects. Phase change materials are the core part of phase change memory, so the research and application of phase change materials have become the focus of scientific researchers. Germanium antimony tellurium (Ge2Sb2Te5) is currently the most widely used phase change material. However, due to the relatively low crystallization temperature and high reset current of this material, the power consumption of the device operation is high, and the thermal stability and erase speed also need to be further improved.

[0003] Compared with germanium antimony telluride, selenium-doped germanium antimony telluride quaternary alloy has the characteristics of low melting point, fast erase speed and high contrast. When the material film is converted between crystal and mixture, the atoms only need to diffuse over a short distance. Therefore, it has high erase rate, good thermal stability and cyclic performance, and low power consumption, making it one of the preferred materials for phase change memory.

[0004] Chinese patent application 201610742155.1 discloses a method for preparing atomic ratio doped Ge2Sb2Te5 phase change film by analytical method. The specific preparation steps are: calculating the thickness ratio of the deposited films of the two targets, the deposition rate of the films corresponding to the two targets, selecting the substrate and pretreatment, determining the sputtering power of the two targets, sputtering coating, detecting the chemical composition of the film and comparing it with the target film, and fine-tuning the sputtering power to prepare Ge2Sb2Te5 film that meets the doping atom requirements.

[0005] It can be seen that the above-mentioned process can purposefully and clearly set the sputtering process parameters, which is fast and efficient. And the film composition can be accurately controlled by precisely controlling the sputtering power of the two targets. But at the same time, the preparation of germanium antimony tellurium target materials containing doped elements has a relatively high technical content, requires very precise control, and the preparation process is slightly complicated.

[0006] Chinese patent application 202310661181.1 discloses a silicon-germanium-antimony-telluride doped target and its preparation method. The steps include: mixing a certain proportion of silicon powder with Ge x Sb y Te zThe powders are mixed, then wet-milled, left to stand, and dried to obtain silicon-germanium-antimony-telluride powder. Then, silicon-germanium-antimony-telluride targets are prepared by vacuum hot pressing and machining. This solution can also solve the problem that traditional double-target sputtering for preparing thin films is difficult to match and control the sputtering rate. However, selenium and silicon do not belong to the same main group of elements. Whether the method of preparing targets with silicon-germanium-antimony-telluride can be applied to Se-doped germanium-antimony-telluride phase change targets remains to be verified.

[0007] The problem that this solution needs to solve is: How to propose a method for preparing a selenium-germanium-antimony-tellurium phase change target material with good density. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing a selenium-doped germanium-antimony-tellurium phase change target. The method makes the selenium-doped germanium-antimony-tellurium target have good density and good component distribution uniformity by sintering with variable pressure and variable heating rate multiple times during the secondary sintering process.

[0009] To achieve the above object, the present application discloses a method for preparing a selenium-doped germanium-antimony-tellurium phase change target, comprising the following steps:

[0010] Step 1: Mix and homogenize selenium powder and germanium antimony tellurium alloy powder to obtain powder A;

[0011] Step 2: Sintering the powder A once to obtain a master alloy;

[0012] Step 3: crush and sieve the master alloy to obtain powder B;

[0013] Step 4: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target;

[0014] The secondary sintering is hot pressing sintering, which includes the first stage, the second stage, the third stage and the fourth stage in sequence;

[0015] The first stage is the pre-pressing stage, and the pressure in the pre-pressing stage is 5-20T, the duration is 6-8s, and then the pressure is released;

[0016] The second stage is the first heating without pressurization stage, the temperature of the first heating without pressurization stage is 230-300°C, the pressure is 0T, and the duration is 30-60min;

[0017] The third stage is the second heating without pressurization stage, the temperature of the second heating without pressurization stage is 550-580°C, the pressure is 0T, and the duration is 20-30min; and after the third stage is completed, the powder B is pressurized to 41-45T, and then enters the fourth stage;

[0018] The fourth stage is the heat preservation and pressure holding stage. The temperature of the heat preservation and pressure holding stage is the same as the temperature of the second heating and non-pressurization stage. The pressure is 41~45T and the duration is 60~90min.

[0019] Preferably, powder B includes large-particle-size powder B, medium-particle-size powder B, and small-particle-size powder B;

[0020] The particle size of the large-particle powder B is 150-200 mesh, the particle size of the medium-particle powder B is 200-270 mesh (excluding 200 mesh), and the particle size of the small-particle powder B is 270-360 mesh (excluding 270 mesh);

[0021] The mass ratio of large particle size powder B, medium particle size powder B and small particle size powder B is 1:1.2 to 2:4.

[0022] Preferably, step 1 specifically comprises: mixing selenium powder and germanium antimony tellurium alloy powder, and homogenizing at a rotation speed of 25 to 35 rpm for 3 to 8 hours to obtain powder A.

[0023] Preferably, step 2 is specifically as follows: placing powder A in a reducing gas atmosphere, first heating the temperature to 200-240° C. at a heating rate of 8-15° C. / min and keeping the temperature for 2-4 hours;

[0024] Then raise the temperature to 550-650°C at a rate of 3-10°C / min, keep warm for 4-6 hours, and then cool to obtain an intermediate alloy.

[0025] Preferably, in step 1, the mass ratio of selenium powder to germanium antimony tellurium alloy powder is 5-10:90-95.

[0026] Preferably, the first stage is a pre-pressing stage, and the pressure of the pre-pressing stage is 8 to 15T, and the duration is 6 to 8s.

[0027] In addition, the present application also discloses a selenium-doped germanium-antimony-tellurium phase change target material, which is prepared by the above-mentioned method for preparing the selenium-doped germanium-antimony-tellurium phase change target material.

[0028] Preferably, the relative density of the Se-doped Germanium Antimony Telluride phase change target is not less than 95%.

[0029] The beneficial effects of the present invention are:

[0030] The present invention provides a method for preparing a selenium-doped germanium-antimony-tellurium phase change target. The method makes the selenium-doped germanium-antimony-tellurium target have good density and good component distribution uniformity by sintering with variable pressure and variable heating rate multiple times during the secondary sintering process. DETAILED DESCRIPTION

[0031] In the description of the present invention, it should be noted that, if the specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0032] Example 1

[0033] Step 1: Selenium powder and germanium antimony tellurium alloy powder were mixed at a ratio of 5:95 and homogenized at a speed of 25 rpm for 8 hours to obtain powder A;

[0034] Step 2: Place powder A in a reducing gas atmosphere, first increase the temperature to 200°C at a heating rate of 8°C / min and keep the temperature for 4 hours;

[0035] Then the temperature was raised to 550°C at 3°C / min, kept at that temperature for 6 hours, and then cooled to obtain an intermediate alloy;

[0036] Step 3: Take out the master alloy, crush and sieve it to obtain powder B with a particle size of 285±10 mesh;

[0037] Step 4: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target;

[0038] The secondary sintering is hot pressing sintering, which includes the first stage, the second stage, the third stage and the fourth stage in sequence;

[0039] The first stage is the pre-pressing stage, and the pressure in the pre-pressing stage is 5T, the duration is 6s, and then the pressure is released;

[0040] The second stage is the first heating without pressurization stage, the temperature of the first heating without pressurization stage is 230℃, the pressure is 0T, and the duration is 60min;

[0041] The third stage is the second heating without pressurization stage, the temperature of the second heating without pressurization stage is 550°C, the pressure is 0T, and the duration is 30min; and after the third stage is completed, the powder B is pressurized to 41T, and then enters the fourth stage;

[0042] The fourth stage is the heat preservation and pressure holding stage. The temperature of the heat preservation and pressure holding stage is the same as that of the second heating and non-pressurization stage. The pressure is 41T and the duration is 90min.

[0043] Example 2

[0044] Step 1: Selenium powder and germanium antimony tellurium alloy powder were mixed at a ratio of 8:92 and homogenized at a speed of 35 rpm for 3 hours to obtain powder A;

[0045] Step 2: Place powder A in a reducing gas atmosphere, first increase the temperature to 240°C at a heating rate of 15°C / min and keep the temperature for 2h;

[0046] Then the temperature was raised to 650°C at 10°C / min, kept at that temperature for 4h, and then cooled to obtain an intermediate alloy;

[0047] Step 3: Take out the master alloy, crush and sieve to obtain powder B with a particle size of 160±10 mesh;

[0048] Step 4: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target;

[0049] The secondary sintering is hot pressing sintering, which includes the first stage, the second stage, the third stage and the fourth stage in sequence;

[0050] The first stage is the pre-pressing stage, and the pressure in the pre-pressing stage is 20T, the duration is 8s, and then the pressure is released;

[0051] The second stage is the first heating without pressurization stage, the temperature of the first heating without pressurization stage is 300℃, the pressure is 0T, and the duration is 30min;

[0052] The third stage is the second heating without pressurization stage, the temperature of the second heating without pressurization stage is 580°C, the pressure is 0T, and the duration is 20min; and after the third stage is completed, the powder B is pressurized to 45T, and then enters the fourth stage;

[0053] The fourth stage is the heat preservation and pressure holding stage. The temperature of the heat preservation and pressure holding stage is the same as that of the second heating and non-pressurization stage. The pressure is 45T and the duration is 60min.

[0054] Example 3

[0055] Step 1: Selenium powder and germanium antimony tellurium alloy powder were mixed at a ratio of 10:90 and homogenized at a speed of 30 rpm for 5 hours to obtain powder A;

[0056] Step 2: Place powder A in a reducing gas atmosphere, first increase the temperature to 220°C at a heating rate of 12°C / min and keep the temperature for 3 hours;

[0057] Then the temperature was raised to 600°C at 6°C / min, kept at that temperature for 5h, and then cooled to obtain an intermediate alloy;

[0058] Step 3: Take out the master alloy, crush and sieve to obtain powder B with a particle size of 215±10 mesh;

[0059] Step 4: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target;

[0060] The secondary sintering is hot pressing sintering, which includes the first stage, the second stage, the third stage and the fourth stage in sequence;

[0061] The first stage is the pre-pressing stage, and the pressure in the pre-pressing stage is 13T, the duration is 7s, and then the pressure is released;

[0062] The second stage is the first heating without pressurization stage, the temperature of the first heating without pressurization stage is 270℃, the pressure is 0T, and the duration is 45min;

[0063] The third stage is the second heating without pressurization stage, the temperature of the second heating without pressurization stage is 560°C, the pressure is 0T, and the duration is 25min; and after the third stage is completed, the powder B is pressurized to 43T, and then enters the fourth stage;

[0064] The fourth stage is the heat preservation and pressure holding stage. The temperature of the heat preservation and pressure holding stage is the same as that of the second heating and non-pressurization stage. The pressure is 43T and the duration is 75min.

[0065] Example 4

[0066] The method is basically the same as Example 1, except that step 3 specifically comprises taking out the intermediate alloy, crushing it, and sieving it to obtain a large-particle powder B and a small-particle powder B;

[0067] The particle size of large particle size powder B is 160±10 mesh;

[0068] The particle size of small-particle powder B is 285±10 mesh;

[0069] The mass ratio of large particle size powder B to small particle size powder B is 1:4.

[0070] Example 5

[0071] The same as Example 1, except that step 3 specifically comprises taking out the intermediate alloy, breaking broken, Sieve to obtain large-size powder B and medium-size powder B;

[0072] The particle size of large particle size powder B is 160±10 mesh;

[0073] The particle size of medium-sized powder B is 215±10 mesh;

[0074] The mass ratio of large particle size powder B to medium particle size powder B is 1:1.6.

[0075] Example 6

[0076] The same as Example 1, except that step 3 specifically comprises taking out the intermediate alloy, breaking broken, Sieve to obtain medium-sized powder B and small-sized powder B;

[0077] The particle size of medium-sized powder B is 215±10 mesh;

[0078] The particle size of small-particle powder B is 285±10 mesh;

[0079] The mass ratio of medium-sized powder B to small-sized powder B is 1.6:4.

[0080] Example 7

[0081] The same as Example 1, except that step 3 specifically comprises taking out the intermediate alloy, breaking broken, Sieve to obtain large-size powder B and small-size powder B;

[0082] The particle size of large particle size powder B is 160±10 mesh;

[0083] The particle size of medium-sized powder B is 215±10 mesh;

[0084] The particle size of small-particle powder B is 285±10 mesh;

[0085] The mass ratio of large particle size powder B, medium particle size powder B and small particle size powder B is 1:1.6:4.

[0086] Comparative Example 1

[0087] The method is basically the same as Example 1, except that step 4 specifically comprises: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target;

[0088] The secondary sintering is hot pressing sintering, which includes the first stage, the second stage, the third stage and the fourth stage in sequence;

[0089] The first stage is the pre-pressing stage, and the pressure of the pre-pressing stage is 5T and the duration is 6s;

[0090] The second stage is the first heating and pressurizing stage. The temperature of the first heating and non-pressurizing stage is 230°C, the pressure is 5T, and the duration is 60min.

[0091] The third stage is the second heating and pressurizing stage. The temperature of the second heating and non-pressurizing stage is 550°C, the pressure is 5T, and the duration is 30min. After the third stage is completed, the powder B is pressurized to 41T, and then enters the fourth stage.

[0092] The fourth stage is the heat preservation and pressure holding stage. The temperature of the heat preservation and pressure holding stage is the same as that of the second heating and non-pressurization stage. The pressure is 41T and the duration is 90min.

[0093] Comparative Example 2

[0094] The method is basically the same as Example 1, except that step 4 specifically comprises: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target;

[0095] The secondary sintering is hot pressing sintering, which includes the second stage, the third stage and the fourth stage in sequence;

[0096] The second stage is the first heating without pressurization stage, the temperature of the first heating without pressurization stage is 230℃, the pressure is 0T, and the duration is 60min;

[0097] The third stage is the second heating and pressurizing stage. The temperature of the second heating and non-pressurizing stage is 550°C, the pressure is 0T, and the duration is 30min. After the third stage is completed, the powder B is pressurized to 41T, and then enters the fourth stage.

[0098] The fourth stage is the heat preservation and pressure holding stage. The temperature of the heat preservation and pressure holding stage is the same as that of the second heating and non-pressurization stage. The pressure is 41T and the duration is 90min.

[0099] Comparative Example 3

[0100] The method is basically the same as Example 1, except that step 4 specifically comprises: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target;

[0101] The secondary sintering is hot pressing sintering, which includes the first stage, the third stage and the fourth stage in sequence;

[0102] The first stage is the pre-pressing stage, and the pressure in the pre-pressing stage is 5T, lasting for 6s, followed by pressure relief;

[0103] The third stage is the second heating without pressurization stage, the temperature of the second heating without pressurization stage is 550°C, the pressure is 0T, and the duration is 90min; and after the third stage is completed, the powder B is pressurized to 41T, and then enters the fourth stage;

[0104] The fourth stage is the heat preservation and pressure holding stage. The temperature of the heat preservation and pressure holding stage is the same as that of the second heating and non-pressurization stage. The pressure is 41T and the duration is 90min.

[0105] Comparative Example 4

[0106] The method is basically the same as Example 1, except that step 4 specifically comprises: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target;

[0107] The secondary sintering is hot pressing sintering, which includes the first stage, the second stage and the fourth stage in sequence;

[0108] The first stage is the pre-pressing stage, and the pressure in the pre-pressing stage is 5T, the duration is 6s, and then the pressure is released;

[0109] The second stage is the first heating without pressurization stage, the temperature of the first heating without pressurization stage is 230°C, the pressure is 0T, and the duration is 90min; and after the second stage is completed, the powder B is pressurized to 41T, and then enters the fourth stage;

[0110] The fourth stage is the heat preservation and pressure holding stage. The temperature of the heat preservation and pressure holding stage is the same as that of the second heating and non-pressurization stage. The pressure is 41T and the duration is 90min.

[0111] Performance Testing:

[0112] The mass fraction of Se element in the Se-doped germanium antimony tellurium phase change target prepared in the present application was tested by the three-point method, and the relative density of the Se-doped germanium antimony tellurium phase change target prepared in the present application was tested by the Archimedean drainage method. The results are shown in Table 1:

[0113] Table 1

[0114] Group Point ASe / wt% B point Se / wt% C point Se / wt% Relative density Example 1 5.91％ 6.18％ 5.96％ 99.67％ Example 2 8.03％ 7.86％ 7.94％ 95.51％ Example 3 9.96％ 10.26％ 10.13％ 95.83％ Example 4 6.17％ 5.96％ 6.03％ 96.32％ Example 5 5.99％ 6.19％ 6.05％ 96.43％ Example 6 6.05％ 6.16％ 6.01％ 96.98％ Example 7 5.98％ 6.05％ 6.02％ 99.48％ Comparative Example 1 5.84％ 6.28％ 5.76％ / Comparative Example 2 5.35％ 6.02％ 5.70％ / Comparative Example 3 5.92％ 6.37％ 6.01％ 83.16％ Comparative Example 4 6.22％ 5.99％ 5.74％ 79.25％

[0115] Result analysis:

[0116] 1. It can be seen from Examples 1-3 that when the parameters in the target material preparation process are slightly adjusted in Examples 1-3, the relative density of Examples 1-3 changes to a certain extent, but the overall relative density is greater than 95%. Further observation of Example 1 shows that when Example 1 uses powder B with a smaller particle size to prepare the target material, the relative density of the target material prepared in Example 1 is significantly higher than that of Examples 2-3. The reason is that the use of powders with small particle sizes can reduce the gaps between the powders, thereby increasing the relative density of the target material;

[0117] 2. It can be seen from Examples 1 and 4-7 that when using large-particle powder B, small-particle powder B; large-particle powder B, medium-particle powder B; medium-particle powder B, small-particle powder B; all three cannot reach a level close to that of Example 1. Further observation of Example 7 shows that when Example 7 uses a mixture of large-particle powder B, medium-particle powder B, and small-particle powder B, the relative density of Example 7 is significantly reduced compared with that of Example 1. It can be seen that when large-particle powder B, medium-particle powder B, and small-particle powder B are mixed, the overall gap between the powders is reduced. Moreover, observation of Example 6 shows that even though the average particle size of Example 6 is smaller than that of Example 7, Example 6 still cannot achieve a good relative density.

[0118] 3. It can be seen from Example 1 and Comparative Example 1 that when Comparative Example 1 is continuously pressurized during the secondary sintering process, cracks appear in the target material of Comparative Example 1. It can be seen that continuous pressurization is difficult to increase the density of the Se-doped Germanium Antimony Telluride phase change target material and may even damage the target material;

[0119] It can be seen from comparative example 2 that the target material prepared in comparative example 2 cannot be formed when the pre-pressing stage is missing. The reason may be that the target material cannot be formed into a rough blank due to the lack of pre-pressing, and the material expands too much in the subsequent heating process, which makes the target material unable to be formed.

[0120] Further observation of comparative examples 3-4 shows that when the second stage or the third stage is omitted, the relative density and uniform composition of the target material have a significant downward trend.

[0121] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a selenium-germanium-antimony-tellurium phase change target, characterized in that: The following steps are involved: Step 1: Mix and homogenize selenium powder and germanium antimony tellurium alloy powder to obtain powder A; Step 2: Sintering the powder A once to obtain an intermediate alloy; Step 3: crush and sieve the master alloy to obtain powder B; Step 4: performing secondary sintering on powder B to obtain a selenium-germanium-antimony-tellurium phase change target; The secondary sintering is hot pressing sintering, and the hot pressing sintering includes a first stage, a second stage, a third stage, and a fourth stage in sequence; The first stage is a pre-pressing stage, and the pressure in the pre-pressing stage is 5 to 20T, the duration is 6 to 8s, and then the pressure is released; The second stage is the first heating without pressurization stage, wherein the temperature of the first heating without pressurization stage is 230-300°C, the pressure is 0T, and the duration is 30-60min; The third stage is the second heating without pressurization stage, the temperature of the second heating without pressurization stage is 550-580°C, the pressure is 0T, and the duration is 20-30min; and after the third stage is completed, the powder B is pressurized to 41-45T, and then enters the fourth stage; The fourth stage is a heat preservation and pressure preservation stage, the temperature of the heat preservation and pressure preservation stage is the same as the temperature of the second temperature increase and non-pressurization stage, the pressure is 41-45T, and the duration is 60-90min.

2. The method for preparing the selenium-germanium-antimony-tellurium phase change target according to claim 1, characterized in that: The powder B includes large-particle powder B, medium-particle powder B, and small-particle powder B; The particle size of the large-particle powder B is 150-200 mesh, the particle size of the medium-particle powder B is 200-270 mesh (excluding 200 mesh), and the particle size of the small-particle powder B is 270-360 mesh (excluding 270 mesh); The mass ratio of the large-particle powder B, the medium-particle powder B, and the small-particle powder B is 1:1.2 to 2:

4.

3. The method for preparing the selenium-germanium-antimony-tellurium phase change target according to claim 1, characterized in that: The step 1 specifically comprises: mixing selenium powder and germanium antimony tellurium alloy powder, and homogenizing at a rotation speed of 25 to 35 rpm for 3 to 8 hours to obtain powder A.

4. The method for preparing the selenium-germanium-antimony-tellurium phase change target according to claim 1, characterized in that: The step 2 is specifically as follows: placing the powder A in a reducing gas atmosphere, first heating the temperature to 200-240° C. at a heating rate of 8-15° C. / min and keeping the temperature for 2-4 hours; Then raise the temperature to 550-650°C at a rate of 3-10°C / min, keep warm for 4-6 hours, and then cool to obtain an intermediate alloy.

5. The method for preparing the selenium-germanium-antimony-tellurium phase change target according to claim 1, characterized in that: In step 1, the mass ratio of selenium powder to germanium antimony tellurium alloy powder is 5-10:90-95.

6. The method for preparing the selenium-germanium-antimony-tellurium phase change target according to claim 1, characterized in that: The first stage is a pre-pressing stage, and the pressure of the pre-pressing stage is 8 to 15T, and the duration is 6 to 8s.

7. A selenium-germanium-antimony-tellurium phase change target, characterized in that: The target is prepared by the method for preparing the selenium-germanium-antimony-tellurium phase change target material as described in any one of claims 1 to 6.

8. The selenium-germanium-antimony-tellurium phase change target according to claim 7, characterized in that: The relative density of the selenium-germanium-antimony-tellurium phase change target material is not less than 95%.