A method for preparing a compositionally uniform low-oxygen MoSi alloy target

Abstract

The application provides a preparation method of a low-oxygen MoSi alloy target material with uniform components, and the preparation method comprises the following steps: first mixing molybdenum powder and silicon powder, and pre-sintering to obtain pre-sintered material; performing refinement treatment on the pre-sintered material to obtain pre-sintered powder; second mixing the pre-sintered powder to obtain mixed material; and performing hot isostatic pressing sintering on the mixed material to obtain the MoSi alloy target material. The preparation method adopts the mode of pre-alloying molybdenum powder and silicon powder first and then sintering to improve the problems of poor component uniformity and high oxygen content, and the raw material powder forms a stable MoSi2 phase after pre-alloying, and the component content is stable and the oxygen content is not easy to increase during ball milling.

Description

Technical Field

[0001] This invention belongs to the field of target processing technology, and particularly relates to a method for preparing a uniformly composed, low-oxygen MoSi alloy target. Background Technology

[0002] MoSi alloy thin films are primarily used in semiconductor photolithography on photomasks. In photolithography, the light-shielding layer on the mask needs to precisely block light transmission. MoSi-based thin films can achieve high and uniform optical density (ensuring light shielding) and controllable anti-reflection properties (reducing unnecessary reflections) by adjusting the composition and deposition process. This is crucial for forming high-fidelity patterns on the substrate. As photolithography technology advances to smaller nodes, traditional binary masks encounter diffraction limitations. Phase-shifting mask technology introduces a 180-degree phase shift using materials like MoSi, causing the light intensity at the boundary of adjacent patterns to cancel out due to interference, thus significantly improving imaging contrast and resolution. The role of the MoSi layer in this process is to precisely control the phase of the light rays.

[0003] MoSi alloy targets are key materials for depositing MoSi alloy thin films. Their uniform composition and low oxygen content are prerequisites for preparing high-quality MoSi alloy thin films.

[0004] Currently, the preparation method for MoSi alloy targets usually involves mixing elemental Mo powder and elemental Si powder and then directly molding and sintering them. However, elemental Mo powder and Si powder have a large density difference, making it difficult to achieve a uniform distribution of Mo powder and Si powder after mixing, resulting in poor compositional uniformity of the sintered target blank. Furthermore, the mixing of Mo powder and Si powder is generally carried out by ball milling, which can easily lead to an increase in oxygen content during the ball milling process of elemental powder. Summary of the Invention

[0005] This invention provides a method for preparing a uniform, low-oxygen MoSi alloy target. The method involves pre-alloying molybdenum powder and silicon powder before sintering to improve the problems of poor composition uniformity and high oxygen content. After pre-alloying, the raw material powder forms a stable MoSi2 phase with stable composition and content, and the oxygen content is not easily increased during ball milling.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a homogeneous, low-oxygen MoSi alloy target, the method comprising: Molybdenum powder and silicon powder are first mixed and then pre-sintered to obtain pre-fired material; The pre-calcined material is refined to obtain pre-calcined powder; the pre-calcined powder is then mixed a second time to obtain a mixture. The mixture is subjected to hot isostatic pressing sintering to obtain the MoSi alloy target material.

[0007] In this invention, the raw material powders, namely molybdenum powder and silicon powder, are first fully mixed. Then, through pre-alloying, the raw material powders form a stable MoSi2 phase with stable composition and low oxygen content during ball milling. After that, the uniformity of the molybdenum powder and silicon powder mixture is further improved by crushing and secondary mixing. Finally, after hot isostatic pressing sintering, a low oxygen MoSi alloy target with uniform composition is obtained.

[0008] As a preferred embodiment of the present invention, the particle size of the molybdenum powder is 2~4μm, such as 2μm, 2.2μm, 2.5μm, 3μm, 3.2μm, 3.5μm or 4μm, etc.; the particle size of the silicon powder is 2~4μm, such as 2μm, 2.2μm, 2.5μm, 3μm, 3.2μm, 3.5μm or 4μm, etc., but is not limited to the listed values, and other unlisted values ​​within the above ranges are also applicable.

[0009] Preferably, the molybdenum powder has a purity >3N5 and an oxygen content <50ppm; the silicon powder has a purity >5N and an oxygen content <50ppm.

[0010] As a preferred embodiment of the present invention, the first mixing is carried out in a three-dimensional powder mixer at a rotation speed of 20-40 rpm and a mixing time of 40-50 h. The rotation speed can be 20 rpm, 22 rpm, 25 rpm, 28 rpm, 30 rpm, 32 rpm, 35 rpm, 38 rpm, or 40 rpm, etc., and the mixing time can be 40 h, 41 h, 42 h, 43 h, 44 h, 45 h, 46 h, 47 h, 48 h, 49 h, or 50 h, etc., but is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0011] As a preferred embodiment of the present invention, the vacuum pressureless sintering method is performed at a temperature of 1200~1400℃ for 3~5 hours, with a vacuum degree of <8×10⁻⁶. -2 Pa. The temperature can be 1200℃, 1220℃, 1250℃, 1280℃, 1300℃, 1320℃, 1350℃, 1380℃ or 1400℃, etc., and the time can be 3 h, 3.2 h, 3.5 h, 3.8 h, 4 h, 4.2 h, 4.5 h, 4.8 h or 5 h, etc., but is not limited to the listed values. Other unlisted values ​​within the above ranges are also applicable.

[0012] As a preferred technical solution of the present invention, the refining process is ball milling.

[0013] As a preferred technical solution of the present invention, the mass ratio of pre-burned material to grinding balls in the ball milling process is 1:2 to 4, such as 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, 1:3.2, 1:3.5, 1:3.8 or 1:4, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] Preferably, the grinding ball is a molybdenum ball, and the mass ratio of D10, D20 and D30 in the molybdenum ball is 2:1~2:1~2, preferably 2:1:1.

[0015] Preferably, the planetary disc rotation speed of the ball mill is 60-100 rpm, the spindle rotation speed is 5-10 rpm, and the time is 60-90 min. The planetary disc rotation speed can be 60 rpm, 65 rpm, 70 rpm, 75 rpm, 80 rpm, 85 rpm, 90 rpm, 95 rpm, or 100 rpm, etc., and the spindle rotation speed can be 5 rpm, 6 rpm, 7 rpm, 8 rpm, 9 rpm, or 10 rpm, etc., but is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0016] As a preferred technical solution of the present invention, the pre-calcined powder is subjected to sieving after the refining process, and the particle size of the pre-calcined powder is not greater than 50 μm.

[0017] The material can be sieved using a 200 or 300 mesh sieve, and the powder passing through the sieve can be collected. Larger particles on the sieve can be returned to be crushed together with the next batch of raw materials.

[0018] As a preferred embodiment of the present invention, the second mixing is carried out in a three-dimensional powder mixer at a rotation speed of 20-40 rpm for a mixing time of 8-10 h. The rotation speed can be 20 rpm, 22 rpm, 25 rpm, 28 rpm, 30 rpm, 32 rpm, 35 rpm, 38 rpm, or 40 rpm, etc., and the mixing time can be 8 h, 8.2 h, 8.5 h, 8.8 h, 9 h, 9.2 h, 9.5 h, 9.8 h, or 10 h, etc., but is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0019] As a preferred embodiment of the present invention, the hot isostatic pressing sintering temperature is 1400~1600℃, the pressure is 90~110 MPa, and the time is 3~5 h. The temperature can be 1400℃, 1420℃, 1450℃, 1480℃, 1500℃, 1520℃, 1550℃, 1580℃, or 1600℃, etc.; the pressure can be 90 MPa, 92 MPa, 95 MPa, 98 MPa, 100 MPa, 102 MPa, 105 MPa, 108 MPa, or 110 MPa, etc.; and the time can be 3 h, 3.2 h, 3.5 h, 3.8 h, 4 h, 4.2 h, 4.5 h, 4.8 h, or 5 h, etc., but is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0020] In this invention, the mixture is placed in a stainless steel sleeve before hot isostatic pressing, compacted, and then placed in a hot isostatic pressing sintering apparatus for sintering.

[0021] In this invention, to avoid introducing excessive oxygen during mixing, both the first and second mixing are carried out under a protective atmosphere, such as argon and nitrogen.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides a method for preparing a uniform, low-oxygen MoSi alloy target. The method involves pre-alloying molybdenum powder and silicon powder before sintering to improve the problems of poor composition uniformity and high oxygen content. After pre-alloying, the raw material powder forms a stable MoSi2 phase with stable composition and content, and the oxygen content is not easily increased during ball milling. Detailed Implementation

[0023] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0024] Example 1 This embodiment provides a method for preparing a uniformly composed, low-oxygen MoSi alloy target, which includes the following steps: Mo powder and Si powder were loaded into a mixing tank with a Si content of 54wt%, and the tank was filled with argon for protection. The first mixing was carried out using a three-dimensional powder mixer at a speed of 30 rpm for 45 h. The Mo powder had a purity >3N5, an oxygen content <50ppm, and a particle size of 2~4μm. The Si powder had a purity >5N, an oxygen content <50ppm, and a particle size of 2~4μm. The mixed powder was placed in a Mo crucible and pre-alloyed using a vacuum pressureless sintering method at a sintering temperature of 1300℃ for 4 h, with a vacuum degree <8×10⁻⁶. -2 Pa; The pre-alloyed MoSi alloy block was placed in a ball mill jar for ball milling. Mo balls of D10, D20 and D30 were weighed in a ratio of 2:1:1. The alloy block and Mo balls were placed in the ball mill jar in a weight ratio of 1:3 for ball milling. The ball milling parameters were: planetary disk speed 80 rpm, spindle speed 8 rpm, and time 75 min. The alloy powder after ball milling is sieved using a 300-mesh sieve to ensure that the particle size of the alloy powder is below 50μm; large particles that do not pass the sieve can be ball-milled again and sieved again. The sieved MoSi alloy powder was loaded into a mixing tank, which was filled with argon gas for protection. A second mixing was carried out using a three-dimensional powder mixer at a speed of 30 rpm for 9 hours. The MoSi alloy powder after secondary mixing was placed in a stainless steel sleeve and subjected to hot isostatic pressing sintering at a temperature of 1500℃, a pressure of 100MPa, and a sintering time of 4 h.

[0025] Example 2 This embodiment provides a method for preparing a uniformly composed, low-oxygen MoSi alloy target, which includes the following steps: Mo powder and Si powder were loaded into a mixing tank with a Si content of 54wt%, and the tank was filled with argon gas for protection. The first mixing was carried out using a three-dimensional powder mixer at a speed of 20 rpm for 50 h. The Mo powder had a purity >3N5, an oxygen content <50ppm, and a particle size of 2~4μm. The Si powder had a purity >5N, an oxygen content <50ppm, and a particle size of 2~4μm. The mixed powder was placed in a Mo crucible and pre-alloyed using a vacuum pressureless sintering method. The sintering temperature was 1200℃, the sintering time was 5 h, and the vacuum degree was <8×10⁻⁶. -2 Pa; The pre-alloyed MoSi alloy block was placed in a ball mill jar for ball milling. Mo balls of D10, D20 and D30 were weighed in a ratio of 2:1:1. The alloy block and Mo balls were placed in the ball mill jar in a weight ratio of 1:3 for ball milling. The ball milling parameters were: planetary disk speed 60 rpm, spindle speed 5 rpm, and time 90 min. The alloy powder after ball milling is sieved using a 200-mesh sieve to ensure that the particle size of the alloy powder is below 50μm; large particles that do not pass the sieve can be ball-milled again and sieved again. The sieved MoSi alloy powder was loaded into a mixing tank, which was filled with argon gas for protection. A second mixing was carried out using a three-dimensional powder mixer at a speed of 20 rpm for 10 hours. The MoSi alloy powder after secondary mixing was placed in a stainless steel casing and subjected to hot isostatic pressing sintering at a temperature of 1400℃, a pressure of 110MPa, and a sintering time of 5 h.

[0026] Example 3 This embodiment provides a method for preparing a uniformly composed, low-oxygen MoSi alloy target, which includes the following steps: Mo powder and Si powder were loaded into a mixing tank with a Si content of 54wt%, and the tank was filled with argon gas for protection. The first mixing was carried out using a three-dimensional powder mixer at a speed of 40 rpm for 40 h. The Mo powder had a purity >3N5, an oxygen content <50ppm, and a particle size of 2~4μm. The Si powder had a purity >5N, an oxygen content <50ppm, and a particle size of 2~4μm. The mixed powder was placed in a Mo crucible and pre-alloyed using a vacuum pressureless sintering method. The sintering temperature was 1200℃, the sintering time was 5 h, and the vacuum degree was <8×10⁻⁶. -2 Pa; The pre-alloyed MoSi alloy block was placed in a ball mill jar for ball milling. Mo balls of D10, D20 and D30 were weighed in a ratio of 2:1:1. The alloy block and Mo balls were placed in the ball mill jar in a weight ratio of 1:2 for ball milling. The ball milling parameters were: planetary disk speed 100 rpm, spindle speed 10 rpm, and time 60 min. The alloy powder after ball milling is sieved using a 200-mesh sieve to ensure that the particle size of the alloy powder is below 50μm; large particles that do not pass the sieve can be ball-milled again and sieved again. The sieved MoSi alloy powder was loaded into a mixing tank, which was filled with argon gas for protection. A second mixing was carried out using a three-dimensional mixing machine at a speed of 40 rpm for 8 hours. The MoSi alloy powder after secondary mixing was placed in a stainless steel casing and subjected to hot isostatic pressing sintering at a temperature of 1600℃, a pressure of 90MPa, and a sintering time of 3 h.

[0027] Comparative Example 1 This comparative example is identical to Example 1 except that pre-alloying is not performed, i.e., the second mixing is performed directly after the first mixing.

[0028] Comparative Example 2 Except for the pre-alloying temperature of 1000°C, the conditions in this comparative example are the same as those in Example 1.

[0029] Comparative Example 3 Except for the pre-alloying temperature of 1600°C, the conditions in this comparative example are the same as those in Example 1.

[0030] Comparative Example 4 This comparative example does not involve a second mixing process; that is, the sieved MoSi alloy powder is directly subjected to hot isostatic pressing sintering.

[0031] Comparative Example 5 In this comparative example, only D10 grinding balls were used for ball milling, and all other conditions were the same as in Example 1.

[0032] Comparative Example 6 In this comparative example, only D20 grinding balls were used for ball milling, and all other conditions were the same as in Example 1.

[0033] Comparative Example 7 In this comparative example, only D30 grinding balls were used for ball milling, and all other conditions were the same as in Example 1.

[0034] The oxygen content and elemental distribution uniformity of the MoSi alloy targets prepared in Examples 1-3 and Comparative Examples 1-7 were tested, and the results are shown in Table 1.

[0035] Oxygen content was tested using the inert gas melting-infrared method, and elemental distribution uniformity was observed using scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM-EDS).

[0036] Table 1 As can be seen from the test results in Table 1, the MoSi alloy target prepared by the method for preparing uniform low-oxygen MoSi alloy target provided by the present invention introduces almost no new oxygen elements during the preparation process, and the oxygen content of the finished product is <50 ppm. Furthermore, when the sample center and edge areas were observed by spark direct reading spectrometer, no uneven element distribution was observed.

[0037] Comparative Example 1, lacking pre-alloying, introduced some oxygen into the second mixture, resulting in an oxygen content increase of >50 ppm in the finished product. Comparative Example 2, with its lower pre-alloying temperature and insufficient pre-alloying, generated less MoSi2 phase, leading to the continued introduction of small amounts of oxygen into the subsequent second mixture, resulting in an oxygen content increase of >50 ppm in the finished product. Comparative Example 3, with its higher pre-alloying temperature, generated other alloy phases not belonging to MoSi2, making it impossible to effectively prevent the introduction of oxygen, resulting in an oxygen content increase of >50 ppm in the finished product.

[0038] Comparative Example 4 did not undergo a second mixing after crushing, resulting in insufficient uniform mixing of the raw material powder and areas of uneven element distribution in the finished product. Comparative Examples 5-7 used single-size grinding balls for ball milling, resulting in a large amount of material on the sieve. Multiple ball milling processes were required to meet the particle size requirements. Furthermore, multiple ball milling processes caused the raw material powder to remain in the high-energy environment for too long, thereby increasing the risk of introducing oxygen and causing the oxygen content of the finished product to rise above 50 ppm.

Claims

1. A method for preparing a homogeneous, low-oxygen MoSi alloy target, characterized in that, The preparation method includes: Molybdenum powder and silicon powder are first mixed and then pre-sintered to obtain pre-fired material; The pre-calcined material is refined to obtain pre-calcined powder; the pre-calcined powder is then mixed a second time to obtain a mixture. The mixture is subjected to hot isostatic pressing sintering to obtain the MoSi alloy target material.

2. The method for preparing MoSi alloy target material according to claim 1, characterized in that, The particle size of the molybdenum powder is 2~4μm, and the particle size of the silicon powder is 2~4μm.

3. The method for preparing MoSi alloy target material according to claim 1, characterized in that, The first mixing is carried out in a three-dimensional powder mixer at a speed of 20-40 rpm for a mixing time of 40-50 h.

4. The method for preparing MoSi alloy target material according to claim 1, characterized in that, The pre-sintering is performed using a vacuum pressureless sintering method.

5. The method for preparing the MoSi alloy target according to claim 4, characterized in that, The vacuum pressureless sintering method is performed at a temperature of 1200~1400℃ for 3~5 hours, with a vacuum degree <8×10⁻⁶. -2 Pa.

6. The method for preparing MoSi alloy target material according to claim 1, characterized in that, The refining process is ball milling.

7. The method for preparing MoSi alloy target material according to claim 6, characterized in that, The mass ratio of pre-calcined material to grinding balls in the ball mill crushing process is 1:2~4; The grinding ball is a molybdenum ball, and the mass ratio of D10, D20 and D30 in the molybdenum ball is 2:1~2:1~2, preferably 2:1:1; The planetary disc of the ball mill crusher rotates at 60-100 rpm, the spindle rotates at 5-10 rpm, and the time is 60-90 min.

8. The method for preparing the MoSi alloy target material according to claim 1, characterized in that, After the refining process, the pre-calcined powder is sieved, and the particle size of the pre-calcined powder is no greater than 50 μm.

9. The method for preparing MoSi alloy target material according to claim 1, characterized in that, The second mixing is carried out in a three-dimensional powder mixer at a speed of 20-40 rpm for 8-10 hours.

10. The method for preparing MoSi alloy target material according to claim 1, characterized in that, The hot isostatic pressing sintering temperature is 1400~1600℃, the pressure is 90~110 MPa, and the time is 3~5 h.

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