High-purity high-density graphite target material as well as preparation method and application thereof

Abstract

The invention provides a high-purity high-density graphite target material and a preparation method and application thereof, and the preparation method comprises the following steps: carrying out compression molding on graphite powder to obtain a preliminarily molded target blank; and sequentially performing hot isostatic pressing sintering treatment and graphitization treatment under a protective atmosphere to obtain the high-purity and high-density graphite target material. The preparation method provided by the invention simplifies the preparation process, is simple to operate and is beneficial to large-scale production; in addition, introduction of impurities can be effectively reduced in the preparation process, and the purity of the obtained target material is improved; according to the preparation method provided by the invention, the density of the obtained graphite target material can be ensured while the purity is ensured, and the contradiction between the density and the purity in the prior art is solved, so that the high-purity and high-density graphite target material with the purity of more than 5N and the density of more than 1.8 g / cm < 3 > is obtained.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology and relates to a graphite target material, in particular to a high-purity and high-density graphite target material and a preparation method and application thereof. Background Art

[0002] Graphite is a material with excellent electrical and thermal conductivity, and is widely used in various electronic devices and battery manufacturing. Among them, high-purity graphite is widely used in high-end fields such as semiconductors, nuclear reactors, and high-temperature furnaces due to its excellent physical and chemical properties. However, the preparation process of high-purity graphite is complicated, costly, and it is difficult to ensure both purity and density at the same time.

[0003] Target material is an important raw material in semiconductor manufacturing. Its purity and density directly affect the quality of semiconductor products. At present, the main manufacturing methods of target materials include powder metallurgy and hot isostatic pressing. However, these methods cannot guarantee the purity and density of target materials at the same time, and impurities are easily introduced during the preparation process, affecting the performance of the target material.

[0004] CN105271216A discloses a method for preparing high-purity graphite, which comprises the following steps:

[0005] (1) medium carbon or high carbon graphite is passed into a first stage graphite purification device and treated at 1000-2000° C. for 0.5-2 h; (2) the solid product obtained by the treatment in step (1) is passed into a second stage graphite purification device and treated at 2000-3000° C. for 0.5-1 h to obtain high purity graphite.

[0006] CN109867281A discloses a method for preparing a high-purity graphite material, comprising: (1) taking a graphite raw material, placing it in a self-made graphite purification device, heating it to 1000° C. under nitrogen protection, and carrying a certain amount of halogen-containing mixed gas with nitrogen at 1000-1800° C. for treatment for 0.5-2 h; (2) further heating the solid product obtained after the treatment in step (1) to 2300° C., and introducing a certain amount of gas at 2000-2300° C. for treatment for 1-2 h to obtain high-purity graphite.

[0007] However, the above-mentioned prior art can only produce high-purity graphite, and is not suitable for the preparation of graphite targets with high requirements for density and purity. In addition, in the preparation process of graphite targets, it is necessary to optimize the preparation process and avoid introducing impurities to avoid affecting the purity of the target. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention aims to provide a high-purity and high-density graphite target material and a preparation method and application thereof, wherein the preparation method can balance the balance between density and purity, thereby obtaining a graphite target material with a purity of more than 5N and a density of 1.8g / cm 3 The above high-purity and high-density graphite targets.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a high-purity and high-density graphite target, the preparation method comprising the following steps:

[0011] The graphite powder is pressed into shape to obtain a preliminarily formed target blank; then, hot isostatic pressing sintering treatment and graphitization treatment are sequentially performed under a protective atmosphere to obtain the high-purity and high-density graphite target material.

[0012] The preparation method provided by the present invention first presses graphite powder into a preliminarily formed target blank, which can effectively control the shape and size of the graphite target material, and can also avoid the introduction of impurities during the forming process, thereby ensuring the purity of the graphite target material finally obtained; the subsequent hot isostatic pressing treatment can further improve the purity of the graphite target material while improving the density and strength of the graphite target material; the graphitization treatment can further increase the carbon content, thereby improving the purity of the graphite target material; moreover, the preparation method provided by the present invention has a simple process, reduces the preparation cost, improves the production efficiency of the graphite target material, and can obtain a graphite target material with a purity of more than 5N and a density of 1.8g / cm 3 The above high-purity and high-density graphite targets.

[0013] Preferably, the purity of the graphite powder is 4N or above.

[0014] Preferably, the compression molding method is cold isostatic pressing.

[0015] Preferably, the cold isostatic pressing pressure is 200-250 MPa.

[0016] Preferably, the cold isostatic pressing time is more than 1 hour.

[0017] Preferably, the gas used for the protective atmosphere includes nitrogen and / or an inert gas.

[0018] Preferably, the inert gas includes any one of helium, neon or argon, or a combination of at least two of them.

[0019] Preferably, the hot isostatic pressing treatment includes a first heat treatment and a second heat treatment performed sequentially;

[0020] The endpoint temperature of the first heat treatment is 1480-1520°C;

[0021] The terminal temperature of the second heat treatment is 1980-2020°C.

[0022] Preferably, the heating rate of the first heat treatment is 8-10°C / min.

[0023] Preferably, the holding time of the first heat treatment is more than 1 hour.

[0024] Preferably, the endpoint pressure of the first heat treatment is 48-52 MPa.

[0025] Preferably, the heating rate of the second heat treatment is 5-8°C / min.

[0026] Preferably, the holding time of the second heat treatment is more than 3 hours.

[0027] Preferably, during the second heat treatment, the pressure is maintained at 48-52 MPa.

[0028] Preferably, the heating rate of the graphitization treatment is 8-10°C / min.

[0029] Preferably, the temperature of the graphitization treatment is 2980-3020°C.

[0030] Preferably, the graphitization treatment time is more than 5 hours.

[0031] In a second aspect, the present invention provides a high-purity and high-density graphite target material, wherein the high-purity and high-density graphite target material is prepared by the preparation method described in the first aspect;

[0032] The purity of the high-purity and high-density graphite target is above 5N and the density is 1.8g / cm 3 above.

[0033] In a third aspect, the present invention provides an application of the high-purity and high-density graphite target material as described in the second aspect, wherein the high-purity and high-density graphite target material is used for magnetron sputtering.

[0034] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The preparation method provided by the present invention first presses graphite powder into a preliminarily formed target blank, which can effectively control the shape and size of the graphite target material, and can also avoid the introduction of impurities during the forming process, thereby ensuring the purity of the graphite target material finally obtained; the subsequent hot isostatic pressing treatment can further improve the purity of the graphite target material while improving the density and strength of the graphite target material; the graphitization treatment can further increase the carbon content, thereby improving the purity of the graphite target material; moreover, the preparation method provided by the present invention has a simple process, reduces the preparation cost, improves the production efficiency of the graphite target material, and can obtain a graphite target material with a purity of more than 5N and a density of 1.8g / cm 3 The above high-purity and high-density graphite targets. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0038] A certain embodiment of the present invention provides a method for preparing a high-purity and high-density graphite target, the preparation method comprising the following steps:

[0039] The graphite powder is pressed into shape to obtain a preliminarily formed target blank; then, hot isostatic pressing sintering treatment and graphitization treatment are sequentially performed under a protective atmosphere to obtain the high-purity and high-density graphite target material.

[0040] The preparation method provided by the present invention first presses graphite powder into a preliminarily formed target blank, which can effectively control the shape and size of the graphite target material, and can also avoid the introduction of impurities during the forming process, thereby ensuring the purity of the graphite target material finally obtained; the subsequent hot isostatic pressing treatment can further improve the purity of the graphite target material while improving the density and strength of the graphite target material; the graphitization treatment can further increase the carbon content, thereby improving the purity of the graphite target material; moreover, the preparation method provided by the present invention has a simple process, reduces the preparation cost, improves the production efficiency of the graphite target material, and can obtain a graphite target material with a purity of more than 5N and a density of 1.8g / cm 3 The above high-purity and high-density graphite targets.

[0041] The higher the purity of graphite powder, the more conducive it is to improving the purity of the final high-purity and high-density graphite target; however, too high purity will lead to a sharp increase in the cost of graphite powder; the preparation method provided by the present invention can prepare a graphite target with a purity of more than 5N and a density of 1.8g / cm without making the graphite powder have a high initial density. 3 The above high-purity and high-density graphite targets.

[0042] In some embodiments, the purity of the graphite powder is above 4N, for example, it can be 99.99wt%, 99.991wt%, 99.993wt%, 99.995wt%, 99.997wt% or 99.999wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In certain embodiments, the compression molding method is cold isostatic pressing.

[0044] In some embodiments, the cold isostatic pressing pressure is 200-250 MPa, for example, 200 MPa, 210 MPa, 220 MPa, 240 MPa or 250 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] The present invention performs pressing and molding by cold isostatic pressing. During the cold isostatic pressing treatment, as the pressing time increases, the powder particles gradually shift and rearrange under the action of pressure, and the density of the target blank is rapidly improved. However, when the pressing time is extended to a certain extent, the density of the target blank reaches a limit, and the effect of further increasing the pressing time on improving the density is no longer obvious. Therefore, in order to improve the production efficiency of graphite targets, it is necessary to optimize the time of cold isostatic pressing.

[0046] In some embodiments, the cold isostatic pressing time is more than 1 hour, for example, it can be 1 hour, 1.5 hours or 2 hours, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0047] In some embodiments, the protective atmosphere includes nitrogen and / or an inert gas.

[0048] In some embodiments, the inert gas includes any one of helium, neon or argon, or a combination of at least two of them. Typical but non-limiting combinations include a combination of helium and neon, a combination of neon and argon, a combination of helium and argon, or a combination of helium, neon and argon.

[0049] Controlling the appropriate temperature during hot isostatic pressing is beneficial to improving the purity and density of the graphite target. If the temperature during hot isostatic pressing is too high, it will cause excessive growth of the grains, thereby reducing the grain boundaries, reducing the uniformity of the material, and destroying the structural stability of the graphite target. The appropriate temperature can promote the bonding and fusion between the grains and improve the density of the target.

[0050] In some embodiments, the hot isostatic pressing treatment includes a first heat treatment and a second heat treatment performed sequentially;

[0051] The terminal temperature of the first heat treatment is 1480-1520°C, for example, it can be 1480°C, 1490°C, 1500°C, 1510°C or 1520°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] The terminal temperature of the second heat treatment is 1980-2020°C, for example, it can be 1980°C, 1990°C, 2000°C, 2010°C or 2020°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In some embodiments, the heating rate of the first heat treatment is 8-10°C / min, for example, 8°C / min, 9°C / min or 10°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] During the hot isostatic pressing process, as time goes by, the pores between the grains are gradually eliminated, but too long a time will not further increase the density of the graphite target; therefore, in order to improve the production efficiency of the graphite target, it is necessary to optimally control the time of the first heat treatment.

[0055] In some embodiments, the holding time of the first heat treatment is more than 1 hour, for example, it can be 1 hour, 1.5 hours or 2 hours, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0056] In certain embodiments, the endpoint pressure of the first heat treatment is 48-52 MPa, for example, 48 MPa, 49 MPa, 50 MPa, 51 MPa or 52 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0057] In some embodiments, the heating rate of the second heat treatment is 5-8°C / min, for example, 5°C / min, 6°C / min, 7°C / min or 8°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] During the hot isostatic pressing process, as time goes by, the pores between the grains are gradually eliminated, but too long a time will not further increase the density of the graphite target; therefore, in order to improve the production efficiency of the graphite target, it is necessary to optimize the time of the second heat treatment.

[0059] In some embodiments, the holding time of the second heat treatment is more than 3 hours, for example, it can be 3 hours, 3.5 hours or 4 hours, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0060] In some embodiments, during the second heat treatment, the pressure is maintained at 48-52 MPa, for example, 48 MPa, 49 MPa, 50 MPa, 51 MPa or 52 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] In some embodiments, the heating rate of the graphitization treatment is 8-10°C / min, for example, 8°C / min, 9°C / min or 10°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0062] In some embodiments, the temperature of the graphitization treatment is 2980-3020°C, for example, 2980°C, 3000°C or 3020°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0063] In some embodiments, the graphitization treatment time is more than 5 hours, for example, it can be 5 hours, 5.5 hours or 6 hours, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0064] A certain embodiment of the present invention provides a high-purity and high-density graphite target material, wherein the high-purity and high-density graphite target material is prepared by the preparation method described in any embodiment;

[0065] The purity of the high-purity and high-density graphite target is above 5N and the density is 1.8g / cm 3 above.

[0066] A certain embodiment of the present invention provides an application of the high-purity and high-density graphite target material described in any embodiment, wherein the high-purity and high-density graphite target material is used for magnetron sputtering.

[0067] Example 1

[0068] This embodiment provides a method for preparing a high-purity and high-density graphite target material, and the preparation method comprises the following steps:

[0069] (1) Graphite powder with a purity of 4N is pressed by cold isostatic pressing at 220 MPa for 1 h to obtain a preliminarily formed target blank;

[0070] (2) performing a first heat treatment and a second heat treatment in sequence under an argon atmosphere;

[0071] First heat treatment: heating to 1500°C at a heating rate of 9°C / min and keeping at a pressure of 50MPa for 1h;

[0072] Second heat treatment: maintaining the pressure at 50 MPa, heating to 2000°C at a heating rate of 6°C / min, and keeping the temperature for 3 hours;

[0073] (3) Under an argon atmosphere, the temperature was continuously raised to 3000° C. at a heating rate of 9° C. / min, and graphitization treatment was performed for 5 hours to obtain the high-purity and high-density graphite target.

[0074] Example 2

[0075] This embodiment provides a method for preparing a high-purity and high-density graphite target material, and the preparation method comprises the following steps:

[0076] (1) Graphite powder with a purity of 4N is pressed by cold isostatic pressing at 200 MPa for 1 h to obtain a preliminarily formed target blank;

[0077] (2) performing a first heat treatment and a second heat treatment in sequence under an argon atmosphere;

[0078] First heat treatment: heating to 1480°C at a heating rate of 8°C / min and keeping at a pressure of 48MPa for 1h;

[0079] Second heat treatment: maintaining the pressure at 48 MPa, heating to 1980°C at a heating rate of 5°C / min, and keeping at this temperature for 3 hours;

[0080] (3) Under an argon atmosphere, the temperature was continuously raised to 2980° C. at a heating rate of 8° C. / min, and graphitization treatment was performed for 5 h to obtain the high-purity and high-density graphite target.

[0081] Example 3

[0082] This embodiment provides a method for preparing a high-purity and high-density graphite target material, and the preparation method comprises the following steps:

[0083] (1) Graphite powder with a purity of 4N is pressed by cold isostatic pressing at 250 MPa for 1 h to obtain a preliminarily formed target blank;

[0084] (2) performing a first heat treatment and a second heat treatment in sequence under an argon atmosphere;

[0085] First heat treatment: heating to 1520°C at a heating rate of 10°C / min and keeping at a pressure of 52MPa for 1h;

[0086] Second heat treatment: maintaining the pressure at 52 MPa, heating to 2020°C at a heating rate of 8°C / min, and keeping the temperature for 3 hours;

[0087] (3) Under an argon atmosphere, the temperature was continuously raised to 3020° C. at a heating rate of 10° C. / min, and graphitization treatment was performed for 5 h to obtain the high-purity and high-density graphite target.

[0088] Example 4

[0089] This embodiment provides a method for preparing a high-purity and high-density graphite target material, which is the same as that of Embodiment 1 except that the terminal temperature of the first heat treatment is 1400°C.

[0090] Example 5

[0091] This embodiment provides a method for preparing a high-purity and high-density graphite target material, which is the same as that of Embodiment 1 except that the terminal temperature of the first heat treatment is 1600°C.

[0092] Example 6

[0093] This embodiment provides a method for preparing a high-purity and high-density graphite target material, which is the same as that of Embodiment 1 except that the end temperature of the second heat treatment is 1900°C.

[0094] Example 7

[0095] This embodiment provides a method for preparing a high-purity and high-density graphite target material, which is the same as that of Embodiment 1 except that the end temperature of the second heat treatment is 2100°C.

[0096] Example 8

[0097] This embodiment provides a method for preparing a high-purity and high-density graphite target material, which is the same as that of Embodiment 1 except that the temperature of the graphitization treatment is 2900°C.

[0098] Example 9

[0099] This embodiment provides a method for preparing a high-purity and high-density graphite target material, which is the same as that of Embodiment 1 except that the graphitization temperature is 3100°C.

[0100] Example 10

[0101] This embodiment provides a method for preparing a high-purity and high-density graphite target material, and the preparation method comprises the following steps:

[0102] (1) Graphite powder with a purity of 4N is pressed by cold isostatic pressing at 220 MPa for 1 h to obtain a preliminarily formed target blank;

[0103] (2) performing a first heat treatment under an argon atmosphere;

[0104] First heat treatment: heating to 1500°C at a heating rate of 9°C / min and keeping at a pressure of 50MPa for 4h;

[0105] (3) Under an argon atmosphere, the temperature was continuously raised to 3000° C. at a heating rate of 9° C. / min, and graphitization treatment was performed for 5 hours to obtain the high-purity and high-density graphite target.

[0106] Embodiment 11

[0107] This embodiment provides a method for preparing a high-purity and high-density graphite target material, and the preparation method comprises the following steps:

[0108] (1) Graphite powder with a purity of 4N is pressed by cold isostatic pressing at 220 MPa for 1 h to obtain a preliminarily formed target blank;

[0109] (2) In an argon atmosphere, the temperature was raised to 2000°C at a heating rate of 9°C / min and kept at a pressure of 50 MPa for 4 h; the pressure was kept below 50 MPa during the heating process;

[0110] (3) Under an argon atmosphere, the temperature was continuously raised to 3000° C. at a heating rate of 9° C. / min, and graphitization treatment was performed for 5 hours to obtain the high-purity and high-density graphite target.

[0111] Comparative Example 1

[0112] This comparative example provides a method for preparing a graphite target material, and the preparation method comprises the following steps:

[0113] (1) Graphite powder with a purity of 4N is pressed by cold isostatic pressing at 220 MPa for 1 h to obtain a preliminarily formed target blank;

[0114] (2) performing a first heat treatment and a second heat treatment in sequence under an argon atmosphere;

[0115] First heat treatment: heating to 1500°C at a heating rate of 9°C / min and keeping at a pressure of 50MPa for 1h;

[0116] Second heat treatment: maintaining the pressure at 50 MPa, heating to 2000°C at a heating rate of 6°C / min and keeping at this temperature for 3 hours.

[0117] Performance Characterization

[0118] The purity and density of the graphite targets obtained in the above examples and comparative examples were measured, and the results are shown in Table 1.

[0119] Table 1

[0120]

[0121]

[0122] In summary, the preparation method provided by the present invention first presses graphite powder into a preliminarily formed target blank, which can effectively control the shape and size of the graphite target material, and can also avoid the introduction of impurities during the forming process, thereby ensuring the purity of the final graphite target material; the subsequent hot isostatic pressing treatment can further improve the purity of the graphite target material while improving the density and strength of the graphite target material; the graphitization treatment can further increase the carbon content, thereby improving the purity of the graphite target material; moreover, the preparation method provided by the present invention has a simple process, reduces the preparation cost, improves the production efficiency of the graphite target material, and can obtain a graphite target material with a purity of more than 5N and a density of 1.8g / cm 3 The above high-purity and high-density graphite targets.

[0123] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-purity and high-density graphite target, characterized in that: The preparation method comprises the following steps: The graphite powder is pressed into shape to obtain a preliminarily formed target blank; then, hot isostatic pressing sintering treatment and graphitization treatment are sequentially performed under a protective atmosphere to obtain the high-purity and high-density graphite target material.

2. The preparation method according to claim 1, characterized in that: The purity of the graphite powder is above 4N.

3. The preparation method according to claim 1 or 2, characterized in that: The pressing method is cold isostatic pressing; Preferably, the cold isostatic pressing pressure is 200-250 MPa; Preferably, the cold isostatic pressing time is more than 1 hour.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The gas used in the protective atmosphere includes nitrogen and / or inert gas; Preferably, the inert gas includes any one of helium, neon or argon, or a combination of at least two of them.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The hot isostatic pressing treatment includes a first heat treatment and a second heat treatment performed sequentially; The endpoint temperature of the first heat treatment is 1480-1520°C; The terminal temperature of the second heat treatment is 1980-2020°C.

6. The preparation method according to claim 5, characterized in that: The heating rate of the first heat treatment is 8-10°C / min; Preferably, the holding time of the first heat treatment is more than 1 hour; Preferably, the endpoint pressure of the first heat treatment is 48-52 MPa.

7. The preparation method according to claim 5 or 6, characterized in that: The heating rate of the second heat treatment is 5-8°C / min; Preferably, the holding time of the second heat treatment is more than 3 hours; Preferably, during the second heat treatment, the pressure is maintained at 48-52 MPa.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The heating rate of the graphitization treatment is 8-10°C / min; Preferably, the temperature of the graphitization treatment is 2980-3020°C; Preferably, the graphitization treatment time is more than 5 hours.

9. A high-purity and high-density graphite target, characterized in that: The high-purity and high-density graphite target is prepared by the preparation method according to any one of claims 1 to 8; The purity of the high-purity and high-density graphite target is above 5N and the density is 1.8g / cm 3 above.

10. An application of the high-purity and high-density graphite target material as claimed in claim 9, characterized in that: The high-purity and high-density graphite target material is used for magnetron sputtering.

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