A method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors

Abstract

The present invention provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors, the preparation method comprising the following steps: (1) subjecting a tantalum powder raw material to dehydrogenation treatment and then subjecting it to hydrogen reduction to obtain a low-oxygen tantalum powder; the oxygen content of the low-oxygen tantalum powder is ≤300ppm; (2) subjecting the low-oxygen tantalum powder to cold isostatic pressing treatment, degassing treatment and hot isostatic pressing treatment in sequence to obtain a low-oxygen powder metallurgy tantalum target for semiconductors. The preparation method of the present invention is simple to operate, and the oxygen content in the tantalum powder is controlled to be ≤300ppm by subjecting the tantalum powder raw material to hydrogen reduction, and then subjecting it to cold isostatic pressing treatment, degassing treatment and hot isostatic pressing treatment to solve the problem of high oxygen content in the powder metallurgy tantalum target, and has a prospect for wide-scale promotion and application.

Description

Technical Field

[0001] The invention relates to the technical field of target material preparation, and in particular to a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors. Background Art

[0002] In the field of microelectronics, tantalum targets are often used to prepare thin-film electrodes, interconnects, and barrier layers for semiconductor devices, and the purity and gas content of tantalum targets are very high. According to the preparation process of tantalum targets, they can be divided into powder metallurgy tantalum targets and smelting tantalum targets. Compared with tantalum targets made by traditional smelting methods, powder metallurgy tantalum targets have the advantages of uniform organization, small grain size, simple process, and more uniform and dense sputtering coating. However, tantalum powder, the raw material of powder metallurgy tantalum targets, has a great affinity for oxygen. Tantalum powder obtained through crushing and other processes often contains too much oxygen. At the same time, the hot isostatic pressing sintering temperature is much lower than the smelting temperature, and the oxygen in the powder cannot be completely eliminated, resulting in a high oxygen content in powder metallurgy tantalum targets. When the oxygen element in the target material is high, abnormal discharge is prone to occur during the sputtering coating process. The resulting large-particle sputtering particles are prone to cause film defects, affecting the quality of sputtering coating, and thus leading to a reduction in the yield of semiconductor chips. Therefore, how to reduce the oxygen content in tantalum targets is a technical problem that needs to be urgently solved for powder metallurgy tantalum targets.

[0003] At present, the preparation methods of powder metallurgy tantalum targets mainly include electric spark sintering, hot pressing sintering, hot isostatic pressing sintering, high temperature vacuum sintering, etc. However, since tantalum metal has a great affinity for oxygen, the sintering temperature of the above powder metallurgy sintering method is much lower than the melting temperature, and the oxygen in the powder cannot be completely eliminated, resulting in the powder metallurgy tantalum target often containing too much oxygen.

[0004] CN105177513A discloses a method for preparing a high-performance tantalum target material by powder metallurgy, comprising the following steps: (1) loading tantalum powder to be sintered into a mold; (2) placing the mold into an electric spark sintering furnace to perform discharge plasma sintering on the powder; (3) after sintering, cooling to no more than 160° C., removing from the furnace, and demolding; (4) machining the obtained tantalum target blank into the required size.

[0005] CN102367568A discloses a method for preparing a high-purity tantalum target, which comprises the steps of mixing tantalum powder uniformly; loading the mixed tantalum powder into a mold; cold pressing the mold; and vacuum hot pressing and sintering. The internal texture of the target is uniformly distributed and the sputtering performance is excellent.

[0006] CN103147050A discloses a method for producing a high-purity tantalum target material, comprising: (1) placing a tantalum block of 5 to 10 mm × 5 to 10 mm in size in a hydrogenation furnace for hydrogen absorption; (2) crushing the tantalum after hydrogen absorption into powder of 200 mesh and placing it in a steel ladle, heating and evacuating the powder at a certain rate and stage, then placing the steel ladle in a hot isostatic press for sintering, the sintering temperature being 1100 to 1500° C., the atmosphere pressure being 50 to 200 MPa, and finally machining and cutting into a specified shape to obtain the target material.

[0007] CN104480439A discloses a preparation process of a tantalum target material, comprising the following steps: A) isostatically pressing tantalum powder to obtain a tantalum blank; B) sintering the tantalum blank, rolling the sintered tantalum blank, and heat treating the rolled tantalum blank to obtain a tantalum target material.

[0008] However, the above process mainly focuses on the preparation of powder metallurgy tantalum targets, and has not studied the problem of high oxygen content in powder metallurgy tantalum targets.

[0009] Therefore, it is of great significance to develop a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors. Summary of the invention

[0010] In order to solve the above technical problems, the present invention provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors, by reducing tantalum powder with hydrogen to make the oxygen content of the tantalum powder ≤300ppm, and performing cold isostatic pressing on the low-oxygen tantalum powder, followed by degassing and hot isostatic pressing to finally obtain a low-oxygen powder metallurgy tantalum target for semiconductors.

[0011] To achieve this object, the present invention adopts the following technical solutions:

[0012] The present invention provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors, the preparation method comprising the following steps:

[0013] (1) subjecting the tantalum powder raw material to dehydrogenation treatment and then reducing it with hydrogen to obtain low-oxygen tantalum powder; the oxygen content of the low-oxygen tantalum powder is ≤300 ppm;

[0014] (2) The low-oxygen tantalum powder is subjected to cold isostatic pressing, degassing and hot isostatic pressing in sequence to obtain a low-oxygen powder metallurgy tantalum target for semiconductors.

[0015] The method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors of the present invention is to dehydrogenate the tantalum powder raw material because there is a large amount of residual hydrogen in the tantalum powder, which is not conducive to the preparation of tantalum targets; then perform hydrogen reduction to reduce the oxygen content in the tantalum powder, and subsequently perform cold isostatic pressing, degassing and hot isostatic pressing to solve the problem of high oxygen content in the powder metallurgy tantalum target. The degassing treatment realizes dehydrogenation, ensuring that the low-oxygen powder metallurgy tantalum target for semiconductors meets the requirements of sputtering.

[0016] Preferably, the oxygen content of the low-oxygen tantalum powder is ≤300 ppm, for example, it can be 300 ppm, 290 ppm, 260 ppm, 230 ppm, 220 ppm, 200 ppm or 100 ppm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the tantalum powder raw material in step (1) is obtained by crushing the hydrogenated tantalum ingot, which can further reduce the oxygen content in the tantalum powder.

[0018] Preferably, the purity of the tantalum ingot is >99.99%, for example, it can be 99.991%, 99.993%, 99.994%, 99.995%, 99.997% or 99.998%, etc., but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the tantalum ingot is placed in a hydrogenation furnace and evacuated, then filled with hydrogen and heated to 600-700°C, for example, 600°C, 610°C, 620°C, 640°C, 650°C, 670°C or 700°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; when the pressure in the furnace no longer decreases, heating is stopped to obtain the hydrogenated tantalum ingot.

[0020] Preferably, in the crushing process, the hydrogenated tantalum ingots are first crushed using a double-roll mill, and then crushed using a jet mill and classified.

[0021] Preferably, the crushing process obtains tantalum powder raw material with a size of 180 to 325 mesh, for example, it can be 180 mesh, 190 mesh, 200 mesh, 230 mesh, 250 mesh, 300 mesh or 325 mesh, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the dehydrogenation treatment in step (1) is carried out in a hydrogenation furnace.

[0023] Preferably, the temperature of the dehydrogenation treatment is 750-850°C, for example, it can be 750°C, 760°C, 770°C, 780°C, 800°C, 830°C or 850°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the hydrogen flow rate during the hydrogen reduction process in step (1) is 300-600sccm, for example, it can be 300sccm, 320sccm, 350sccm, 400sccm, 450sccm, 500sccm or 600sccm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] The present invention preferably uses a hydrogen flow rate of 300-600 sccm during the hydrogen reduction process. This hydrogen flow rate is mainly based on the safe hydrogen flow rate that can be set by the equipment. Powders of the same mass have the same oxygen content. In order to react the oxygen content in the powder, the larger the flow rate, the shorter the hydrogen flow time; the smaller the flow rate, the longer the hydrogen flow time; so the flow rate should be combined with time.

[0026] Preferably, the temperature of the hydrogen reduction is 600-800°C, for example, it can be 600°C, 620°C, 650°C, 670°C, 700°C, 750°C or 800°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] The present invention preferably uses a hydrogen reduction temperature of 600-800°C, and a temperature at which the oxygen in the tantalum powder reacts with hydrogen is greater than 600°C. If the temperature is lower than 600°C, the oxygen and hydrogen do not react completely and oxygen cannot be completely removed. If the temperature is too high, energy loss is unnecessary.

[0028] The insulation time is 1 to 2 hours, for example, it can be 1 hour, 1.2 hours, 1.3 hours, 1.4 hours, 1.8 hours or 2 hours, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, after the hydrogen reduction, the temperature is lowered in a hydrogen atmosphere to obtain low-oxygen tantalum powder.

[0030] Preferably, the cooling treatment is to a temperature <100°C, for example, 99°C, 98°C, 97°C, 95°C, 93°C, 92°C or 90°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the pressure of the cold isostatic pressing treatment in step (2) is 190-250 MPa, for example, it can be 190 MPa, 200 MPa, 210 MPa, 220 MPa, 230 MPa or 250 MPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the temperature of the cold isostatic pressing treatment is 20-30°C, for example, it can be 20°C, 22°C, 24°C, 25°C, 26°C, 28°C or 30°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the temperature of the degassing treatment in step (2) is 400-600°C, for example, it can be 400°C, 410°C, 430°C, 440°C, 500°C or 600°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the degassing treatment time is 6 to 9 hours, for example, it can be 6 hours, 6.3 hours, 6.5 hours, 6.7 hours, 7 hours, 7.5 hours, 8 hours or 9 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the low-oxygen tantalum powder is placed in a stainless steel sheath during the degassing process, and the vacuum degree in the stainless steel sheath is 1.0×10 -3 ~1.0×10 -2 Pa, for example, can be 1.0×10 -3 Pa, 1.5×10 -3 Pa, 3.0×10 -3 Pa, 5.0×10 -3 Pa, 8.0×10 -3 Pa or 1.0×10 -2 Pa, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the temperature of the hot isostatic pressing treatment in step (2) is 1000-1250°C, for example, it can be 1000°C, 1050°C, 1100°C, 1150°C, 1180°C, 1200°C or 1250°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the pressure of the hot isostatic pressing treatment is 170-190 MPa, for example, it can be 170 MPa, 175 MPa, 178 MPa, 180 MPa, 185 MPa, 188 MPa or 190 MPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the hot isostatic pressing treatment time is 3 to 6 hours, for example, it can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, after the hot isostatic pressing treatment in step (2), the sheath is removed and machining is performed.

[0040] Preferably, the machining comprises turning.

[0041] Preferably, the oxygen content of the low-oxygen powder metallurgy tantalum target for semiconductor is ≤300ppm, for example, it can be 300ppm, 290ppm, 260ppm, 230ppm, 220ppm, 200ppm or 100ppm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0043] (1) A tantalum ingot with a purity of more than 99.99% is placed in a hydrogenation furnace and evacuated, then filled with hydrogen and heated to 600°C to 700°C. When the pressure in the furnace no longer decreases, heating is stopped to obtain a hydrogenated tantalum ingot; the hydrogenated tantalum ingot is first crushed using a double-roll mill, and then crushed using a jet mill and classified to obtain a tantalum powder raw material of 180 to 325 mesh;

[0044] The tantalum powder raw material is heated to 750-850° C. in a hydrogenation furnace for dehydrogenation treatment, and then subjected to hydrogen reduction, and then cooled in a hydrogen atmosphere to a temperature of less than 100° C. to obtain low-oxygen tantalum powder with an oxygen content of ≤300 ppm;

[0045] The hydrogen flow rate during the hydrogen reduction process is 300-600 sccm; the temperature of the hydrogen reduction is 600-800°C, and the holding time is 1-2h;

[0046] (2) The low-oxygen tantalum powder is subjected to cold isostatic pressing at a pressure of 190 to 250 MPa and a temperature of 20 to 30° C., degassing at a temperature of 400 to 600° C. for 6 to 9 hours, and hot isostatic pressing at a temperature of 1000 to 1250° C. and a pressure of 170 to 190 MPa for 3 to 6 hours, and the jacket is removed and turned to obtain a low-oxygen powder metallurgy tantalum target for semiconductors with an oxygen content of ≤300 ppm;

[0047] The low-oxygen tantalum powder in the degassing process is placed in a stainless steel sheath, and the vacuum degree in the stainless steel sheath is 1.0×10 -3 ~1.0×10 -2 Pa.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] The preparation method of the low-oxygen powder metallurgy tantalum target for semiconductors provided by the present invention is simple to operate. The oxygen content in the tantalum powder is controlled to be ≤300ppm by subjecting the tantalum powder raw material to hydrogen reduction. Subsequently, cold isostatic pressing, degassing and hot isostatic pressing are performed to solve the problem of high oxygen content in the powder metallurgy tantalum target. The method has a prospect for wide-scale promotion and application. DETAILED DESCRIPTION

[0050] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0051] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0052] Example 1

[0053] This embodiment provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors, the preparation method comprising the following steps:

[0054] (1) A tantalum ingot with a purity of 99.993% is placed in a hydrogenation furnace and evacuated, and then filled with hydrogen and heated to 620° C. After the pressure in the furnace no longer decreases, the heating is stopped to obtain a hydrogenated tantalum ingot; the hydrogenated tantalum ingot is first crushed using a double-roll mill, and then crushed using a jet mill and classified to obtain a 200-mesh tantalum powder raw material;

[0055] The tantalum powder raw material is heated to 800° C. in a hydrogenation furnace for dehydrogenation treatment, and then reduced with hydrogen, and then cooled to 80° C. in a hydrogen atmosphere to obtain low-oxygen tantalum powder;

[0056] The hydrogen flow rate during the hydrogen reduction process is 500 sccm; the temperature of the hydrogen reduction is 700° C., and the holding time is 1.2 h;

[0057] (2) The low-oxygen tantalum powder is subjected to cold isostatic pressing at a pressure of 200 MPa and a temperature of 23° C., degassing at a temperature of 480° C. for 6.9 h, and hot isostatic pressing at a temperature of 1150° C. and a pressure of 178 MPa for 3.6 h, and the jacket is removed and turned to obtain a low-oxygen powder metallurgy tantalum target for semiconductors;

[0058] The low oxygen tantalum powder in the degassing process is placed in a stainless steel sheath, and the vacuum degree in the stainless steel sheath is 3.0×10 - 3 Pa.

[0059] Example 2

[0060] This embodiment provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors, the preparation method comprising the following steps:

[0061] (1) A tantalum ingot with a purity of 99.998% is placed in a hydrogenation furnace and evacuated, then filled with hydrogen and heated to 600°C. When the pressure in the furnace no longer decreases, heating is stopped to obtain a hydrogenated tantalum ingot; the hydrogenated tantalum ingot is first crushed using a double-roll mill, and then crushed using a jet mill and classified to obtain a 180-mesh tantalum powder raw material;

[0062] The tantalum powder raw material is heated to 830° C. in a hydrogenation furnace for dehydrogenation treatment, and then reduced with hydrogen, and then cooled to 90° C. in a hydrogen atmosphere to obtain low-oxygen tantalum powder;

[0063] The hydrogen flow rate during the hydrogen reduction process is 600 sccm; the temperature of the hydrogen reduction is 600° C., and the holding time is 1.5 h;

[0064] (2) The low-oxygen tantalum powder is subjected to cold isostatic pressing at a pressure of 190 MPa and a temperature of 30° C., degassing at a temperature of 400° C. for 6.2 h, and hot isostatic pressing at a temperature of 1250° C. and a pressure of 190 MPa for 5 h, and the jacket is removed and turned to obtain a low-oxygen powder metallurgy tantalum target for semiconductors;

[0065] The low oxygen tantalum powder in the degassing process is placed in a stainless steel sheath, and the vacuum degree in the stainless steel sheath is 5.0×10 - 3 Pa.

[0066] Example 3

[0067] This embodiment provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors, the preparation method comprising the following steps:

[0068] (1) A tantalum ingot with a purity of 99.991% is placed in a hydrogenation furnace and evacuated, then filled with hydrogen and heated to 700°C. When the pressure in the furnace no longer decreases, heating is stopped to obtain a hydrogenated tantalum ingot; the hydrogenated tantalum ingot is first crushed using a double-roll mill, and then crushed using a jet mill and classified to obtain a 325-mesh tantalum powder raw material;

[0069] The tantalum powder raw material is heated to 850° C. in a hydrogenation furnace for dehydrogenation treatment, and then reduced with hydrogen, and then cooled to 70° C. in a hydrogen atmosphere to obtain low-oxygen tantalum powder;

[0070] The hydrogen flow rate during the hydrogen reduction process is 300 sccm; the temperature of the hydrogen reduction is 750° C., and the holding time is 2 h;

[0071] (2) The low-oxygen tantalum powder is subjected to cold isostatic pressing at a pressure of 250 MPa and a temperature of 20° C., degassing at a temperature of 600° C. for 9 h, and hot isostatic pressing at a temperature of 1000° C. and a pressure of 170 MPa for 3 h, and the jacket is removed and turned to obtain a low-oxygen powder metallurgy tantalum target for semiconductors;

[0072] The low-oxygen tantalum powder in the degassing process is placed in a stainless steel sheath, and the vacuum degree in the stainless steel sheath is 1.0×10 - 3 Pa.

[0073] Example 4

[0074] This embodiment provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors, the preparation method comprising the following steps:

[0075] (1) A tantalum ingot with a purity of 99.994% is placed in a hydrogenation furnace and evacuated, then filled with hydrogen and heated to 655°C. When the pressure in the furnace no longer decreases, heating is stopped to obtain a hydrogenated tantalum ingot; the hydrogenated tantalum ingot is first crushed using a double-roll mill, and then crushed using a jet mill and classified to obtain a 300-mesh tantalum powder raw material;

[0076] The tantalum powder raw material is heated to 750° C. in a hydrogenation furnace for dehydrogenation treatment, and then reduced with hydrogen, and then cooled in a hydrogen atmosphere to a temperature of 94° C. to obtain low-oxygen tantalum powder;

[0077] The hydrogen flow rate during the hydrogen reduction process is 520 sccm; the temperature of the hydrogen reduction is 710° C., and the holding time is 1.6 h;

[0078] (2) The low-oxygen tantalum powder is subjected to cold isostatic pressing at a pressure of 230 MPa and a temperature of 27° C., degassing at a temperature of 510° C. for 7.3 h, and hot isostatic pressing at a temperature of 1200° C. and a pressure of 185 MPa for 6.2 h, and the jacket is removed and turned to obtain a low-oxygen powder metallurgy tantalum target for semiconductors;

[0079] The low-oxygen tantalum powder in the degassing process is placed in a stainless steel sheath, and the vacuum degree in the stainless steel sheath is 1.0×10 - 2 Pa.

[0080] Example 5

[0081] This embodiment provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors. The preparation method is the same as that of Embodiment 1 except that the hydrogen flow rate in the hydrogen reduction process in step (1) is 250 sccm.

[0082] Example 6

[0083] This embodiment provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors. The preparation method is the same as that of Embodiment 1 except that the hydrogen flow rate in the hydrogen reduction process in step (1) is 650 sccm.

[0084] Example 7

[0085] This embodiment provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors. The preparation method is the same as that of Embodiment 1 except that the temperature of hydrogen reduction in step (1) is 580°C.

[0086] Example 8

[0087] This embodiment provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors. The preparation method is the same as that of Embodiment 1 except that the temperature of hydrogen reduction in step (1) is 830°C.

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors. The preparation method is the same as Example 1 except that the tantalum powder raw material is not subjected to hydrogen reduction in step (1).

[0090] The oxygen content of the low-oxygen powder metallurgy tantalum targets for semiconductors obtained in the above examples and comparative examples was tested using a LECO oxygen, nitrogen and hydrogen analyzer. The results are shown in Table 1.

[0091] Table 1

[0092] Oxygen content (ppm) Example 1 245 Example 2 225 Example 3 287 Example 4 275 Example 5 432 Example 6 215 Example 7 675 Example 8 232 Comparative Example 1 755

[0093] From Table 1 we can see that:

[0094] (1) It can be seen from Examples 1 to 4 that the method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors provided by the present invention is simple to operate, and a low-oxygen powder metallurgy tantalum target for semiconductors with an oxygen content of ≤300 ppm is prepared;

[0095] (2) Combining Example 1 with Examples 5 to 6, it can be seen that in Example 5, the hydrogen flow rate is small and the oxygen in the tantalum powder cannot be completely reacted in the same time as in Example 1, resulting in a high oxygen content of 432 ppm in the final tantalum target; in Example 6, the hydrogen flow rate is large and the oxygen in the tantalum powder can be quickly reacted in the same time as in Example 1, but the introduction of excessive hydrogen will increase the preparation cost of the tantalum target;

[0096] (3) Combining Example 1 with Examples 7 to 8, it can be seen that the temperature of hydrogen reduction in Example 7 is relatively low, the reaction between oxygen and hydrogen is not complete, oxygen cannot be completely removed, and the oxygen content of the tantalum target is as high as 675 ppm; the temperature of hydrogen reduction in Example 8 is relatively high, and although the oxygen content of the tantalum target is low, the energy loss is large, and the preparation cost of the tantalum target is high;

[0097] (4) It can be seen from Example 1 and Comparative Example 1 that in the preparation process of powder metallurgy tantalum target, if the tantalum powder raw material is not reduced with hydrogen, the oxygen content of the final tantalum target will be significantly increased to 755 ppm.

[0098] In summary, the method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors provided by the present invention controls the oxygen content in the tantalum powder to ≤300ppm by subjecting the tantalum powder raw material to hydrogen reduction, and subsequently solves the problem of high oxygen content in the powder metallurgy tantalum target through cold isostatic pressing, degassing and hot isostatic pressing, and has a prospect for wide-scale promotion and application.

[0099] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a low-oxygen powder metallurgy tantalum target for semiconductors with an oxygen content of ≤300ppm, characterized in that: The preparation method comprises the following steps: (1) After dehydrogenation treatment, the tantalum powder raw material is subjected to hydrogen reduction to obtain low-oxygen tantalum powder; the oxygen content of the low-oxygen tantalum powder is ≤300ppm; the hydrogen flow rate during the hydrogen reduction process is 300-600sccm; the temperature of the hydrogen reduction is 600-800°C, and the insulation time is 1-2h; the tantalum powder raw material in step (1) is obtained by crushing the hydrogenated tantalum ingot; after the hydrogen reduction in step (1), the temperature is lowered in a hydrogen atmosphere to obtain low-oxygen tantalum powder; (2) The low-oxygen tantalum powder is subjected to cold isostatic pressing, degassing and hot isostatic pressing in sequence to obtain a low-oxygen powder metallurgy tantalum target for semiconductors; The oxygen content of the low-oxygen powder metallurgy tantalum target for semiconductor is ≤300ppm.

2. The preparation method according to claim 1, characterized in that: The purity of the tantalum ingot is >99.99%.

3. The preparation method according to claim 1, characterized in that: The tantalum ingot is placed in a hydrogenation furnace and evacuated, then filled with hydrogen and heated to 600-700° C. When the pressure in the furnace stops decreasing, heating is stopped to obtain a hydrogenated tantalum ingot.

4. The preparation method according to claim 3, characterized in that: In the crushing process, the hydrogenated tantalum ingot is first crushed using a double-roll mill, and then crushed using a jet mill and classified.

5. The preparation method according to claim 1, characterized in that: The crushing process obtains tantalum powder raw material with a mesh size of 180 to 325.

6. The preparation method according to claim 1, characterized in that: The dehydrogenation treatment in step (1) is carried out in a hydrogenation furnace.

7. The preparation method according to claim 1, characterized in that: The temperature of the dehydrogenation treatment is 750-850°C.

8. The preparation method according to claim 1, characterized in that: The cooling treatment is performed to a temperature < 100°C.

9. The preparation method according to claim 1, characterized in that: The pressure of the cold isostatic pressing treatment in step (2) is 190 to 250 MPa.

10. The preparation method according to claim 1, characterized in that: The temperature of the cold isostatic pressing treatment is 20-30°C.

11. The preparation method according to claim 1, characterized in that: The temperature of the degassing treatment in step (2) is 400-600°C.

12. The preparation method according to claim 1, characterized in that: The degassing treatment time is 6 to 9 hours.

13. The preparation method according to claim 1, characterized in that: The low-oxygen tantalum powder in the degassing process is placed in a stainless steel sheath, and the vacuum degree in the stainless steel sheath is 1.0×10 -3 ~1.0×10 -2 Pa.

14. The preparation method according to claim 1, characterized in that: The temperature of the hot isostatic pressing treatment in step (2) is 1000-1250°C.

15. The preparation method according to claim 1, characterized in that: The pressure of the hot isostatic pressing treatment is 170-190 MPa.

16. The preparation method according to claim 1, characterized in that: The hot isostatic pressing treatment time is 3 to 6 hours.

17. The preparation method according to claim 1, characterized in that: After the hot isostatic pressing treatment in step (2), the sheath is removed and machining is performed.

18. The preparation method according to claim 17, characterized in that: The machining includes turning.

19. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: (1) A tantalum ingot with a purity of more than 99.99% is placed in a hydrogenation furnace and evacuated, then filled with hydrogen and heated to 600°C to 700°C. When the pressure in the furnace no longer decreases, heating is stopped to obtain a hydrogenated tantalum ingot; the hydrogenated tantalum ingot is first crushed using a double-roll mill, and then crushed using a jet mill and classified to obtain a tantalum powder raw material of 180 to 325 mesh; The tantalum powder raw material is heated to 750-850° C. in a hydrogenation furnace for dehydrogenation treatment, and then subjected to hydrogen reduction, and then cooled in a hydrogen atmosphere to a temperature of less than 100° C. to obtain low-oxygen tantalum powder with an oxygen content of ≤300 ppm; The hydrogen flow rate during the hydrogen reduction process is 300-600 sccm; the temperature of the hydrogen reduction is 600-800°C, and the holding time is 1-2h; (2) The low-oxygen tantalum powder is subjected to cold isostatic pressing at a pressure of 190 to 250 MPa and a temperature of 20 to 30° C., degassing at a temperature of 400 to 600° C. for 6 to 9 hours, and hot isostatic pressing at a temperature of 1000 to 1250° C. and a pressure of 170 to 190 MPa for 3 to 6 hours, and the jacket is removed and turned to obtain a low-oxygen powder metallurgy tantalum target for semiconductors with an oxygen content of ≤300 ppm; The low-oxygen tantalum powder in the degassing process is placed in a stainless steel sheath, and the vacuum degree in the stainless steel sheath is 1.0×10 -3 ~1.0×10 -2 Pa.