TW201504450A - Method of making molybdenum alloy target - Google Patents

Abstract

A method of making a molybdenum alloy target comprises: (1) blending molybdenum powder with powder of C and at least one metal element selected from the group consisting of Ti, Cr, Nb and T to form uniform alloy powder; (2) adding the alloy powder to a pressurized container and subjecting the pressurized container to a degasing process under vacuum and sealing the degasing hole; (3) using static pressing techniques such as heat to pressurize and heat and adding oxygen into the pressurized container to convert the alloy powder to alloy billet; (4) annealing the alloy billet in a high temperature oven; and (5) subjecting the alloy to cutting, grinding and mechanical processing to form a molybdenum alloy target product. The method of this invention can simplify conventional molybdenum alloy target process and shorten the production cycle of the molybdenum alloy target and effectively increase the plasticity of the molybdenum alloy target.

Description

Method for preparing molybdenum alloy target

The invention belongs to a method for preparing a molybdenum alloy target, which can simplify the process of the conventional molybdenum alloy target, reduce the production cycle of the molybdenum alloy target, and greatly reduce the production cost.

Molybdenum targets are widely used in flat panel displays, microelectronics and optical glass coatings. If the coating needs to be resistant to heat and corrosion, sometimes the molybdenum target will be added to other metals to become a molybdenum alloy target.

Since molybdenum metal has a high melting point, it is usually produced by powder metallurgy. For example, TW I310407 "sputter target material and its preparation method": preparing 6 μm average particle size Mo powder, 100 μm average particle size Nb powder, 100 μm average particle size Cr powder, 100 μm average particle size Ti powder, 100 μm average particle size Zr powder, and 100 μm average particle size V powder.

The manufacturing steps are as follows:

(1) To produce each of the samples, a specific atomic % of Mo powder and any of the additive element powders were weighed.

(2) The weight-measured powder was mixed for 10 minutes using a V-type mixer to obtain a raw material powder.

(3) The raw material powder is pressed by a CIP (cold isostatic pressing) machine to form a green body.

(4) The green body was ground using a masher and a disc grinder to produce a secondary powder.

(5) The secondary powder was mixed in a V-type mixer for 10 minutes and then added to a pressurized container. After the secondary powder is added to the pressurized container, the upper cover having the vent hole is welded to the pressurized container to seal the hole.

(6) The pressurized container to which the secondary powder is added is subjected to a degassing process under vacuum at a temperature of 450 ° C, and the degassing hole is sealed.

(7) The pressurized container was pressurized with a HIP (hot isostatic pressing) machine and the secondary powder was sintered. The working conditions of the HIP machine are 1250 ° C temperature, 120 MPa pressure and 5 hours working time.

(8) Machining or plastic working (such as hot rolling) to obtain the final target size.

SEM I310407 "Sputter target material and its preparation method" SEM microstructure of the sputtering target as shown in Fig. 4, the sputtering target has a microstructure in which the metal element island is dispersed in the molybdenum substrate, and the oxide particles are formed in the molybdenum The metal element in the substrate is in and around the island.

However, TW I310407 "sputter target material and its preparation method" in the preparation of molybdenum alloy, the raw material powder is pressed by a CIP machine to form a green body, and then the green body is crushed using a masher and a disc grinder to make a second Powder, and after the completion of sintering, the target embryo needs to be further subjected to hot rolling and the like as described above, before the target can be made into a uniform composition of molybdenum alloy sputtering target, which not only takes time and money, but also the production cycle Longer time.

And the research shows that: Molybdenum crystal belongs to Body-Centered Cubic Crystal Structure (BCC), and there are few independent slip systems. When stress deformation occurs, the coordination deformation ability between grains is poor, and the grain boundary is easy. Stress concentration occurs to cause cracks, causing grain boundary fracture. At the same time, the molybdenum alloys prepared by various techniques in the industry contain a small amount of impurities such as O, C and N, and the presence of these residual impurities seriously affects the mechanical properties and microstructure of the molybdenum alloy components. Impurities of O, C, N and other impurity elements in molybdenum are very low. These elements exist in the form of oxides, carbides, nitrides, etc., and precipitate around grain boundaries, subgrain boundaries, and defects including misalignment, which not only weaken the grain boundary strength, but also hinder the dislocation motion, promote crack formation, and make molybdenum. The alloy exhibits typical room temperature brittleness.

Therefore, in order to solve the above disadvantages, the inventors actively search for a solution, and after many tests and improvements, finally create a method for preparing a molybdenum alloy target.

In order to achieve the above object, a method for preparing a molybdenum alloy target is provided, wherein the step (1) divides the quantitative molybdenum powder into at least three metal element powders selected from the group consisting of Ti, Cr, Nb and Ta groups. And then each molybdenum powder and at least one metal element selected from the group consisting of Ti, Cr, Nb and Ta groups and the powder of C are separately mixed into a small mixture powder, and each small portion of the mixed powder is divided into at least three groups, and then separately Mix and finally put together, then mix all the mixed powders into a uniform Gold powder; step (2) adding the alloy powder into a pressurized container, depressurizing the pressurized container under vacuum, and sealing the degassing hole; and step (3) using a hot isostatic pressing process to pressurize and heat, And adding oxygen into the pressurized container to make the alloy powder into an alloy embryo; step (4) annealing the alloy embryo at a high temperature furnace at 1500 to 1600 ° C; step (5) cutting the alloy embryo, grinding, mechanical Processed into a finished molybdenum alloy target.

1. The method of the present invention comprises mixing molybdenum powder with at least one metal element selected from the group consisting of Ti, Cr, Nb and Ta groups and powder of C, and directly heating and pressing the alloy powder into an alloy blank by hot isostatic pressing. It is not necessary to use the CIP machine to press the raw material powder to form the raw embryo and then crush it to make the secondary powder, and the target embryo does not need to be hot rolled after the sintering is completed. The procedure is not only less steps than the conventional molybdenum alloy target, but also reduces the production cycle of the molybdenum alloy target, which can greatly reduce the production cost.

2. In the manufacturing process of the molybdenum alloy target of the present invention, an appropriate amount of C is adjusted in the molybdenum alloy, which can effectively improve the plasticity of the molybdenum alloy material and reduce the plastic-brittle transition temperature. In addition, during the annealing or cooling process, using the strong binding energy between C and O, C can also inhibit the segregation of O to the grain boundary, thereby further reducing the influence of impurity element O on molybdenum plasticity. When the carbon-oxygen atomic ratio is above 2:1, the alloy molybdenum exhibits good plasticity.

The above-mentioned objects, structures and features of the present invention will be described in detail with reference to the preferred embodiments of the present invention. .

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Fig. 1 is a flow chart showing the preparation method of the molybdenum alloy target of the present invention.

Fig. 2 is a schematic diagram showing the measurement of the bending property of the MoNb-C rod of the present invention.

Figure 3 is a longitudinal metallographic microstructure analysis of the MoNb-C of the present invention.

Figure 4 is a scanning electron microscope (SEM) cross-sectional view of a conventional molybdenum alloy target.

First, the preferred embodiment of the present invention is shown in FIG. 1, but the embodiments are for illustrative purposes only and are not limited by the structure.

The method for preparing the molybdenum alloy target comprises the steps of: (10) dividing the quantitative molybdenum powder into at least three portions of the powder of at least one metal element selected from the group consisting of Ti, Cr, Nb and Ta groups, and then each Molybdenum powder and at least one metal element selected from the group consisting of Ti, Cr, Nb and Ta groups are mixed with powder of C separately into small mixed powders, and each mixed powder is divided into at least three groups, and then separately mixed and finally combined. Together, all the mixed powders are further mixed into a uniform alloy powder; step (2) 20 is added to the pressurized container, the pressurized container is degassed under vacuum, and the degassing holes are sealed; (3) 30 Pressurize and warm with a HIP (hot isostatic pressing) machine, and add oxygen to the pressurized container. The HIP machine operation is divided into three temperature zones; 0~800°C, 800~1600°C, 1600~2000°C, and each temperature zone is sintered for at least 3 hours, and the working pressure is often 100~200 MPa, so that the alloy powder becomes an alloy embryo. Step (4) 40 annealing the alloy embryo at a high temperature furnace at 1500 to 1600 ° C; step (5) 50, the alloy embryo is cut, refined, and mechanically processed into a finished molybdenum alloy target, wherein the finished molybdenum alloy target The shape can be a flat plate or a round tube.

The atomic percentage of at least one metal element powder selected from the group consisting of Ti, Cr, Nb and Ta groups is 1 to 50%, and the rest is molybdenum; the present inventors have found that among the impurity elements such as 0, C and N, carbon to molybdenum The influence of strength is the smallest, but it has a great influence on the elongation. For example, Table 1 shows the effect of carbon content on the elongation of molybdenum-niobium alloy. When the carbon content increases from 10 mg/kg to 20 mg/kg, the elongation of molybdenum alloy The rapid increase from 10% to 45% proves that carbon contributes to the improvement of the plasticity of the molybdenum alloy; and as the carbon content continues to increase, the elongation of the molybdenum alloy slows down. The higher the oxygen content of the molybdenum alloy, the higher the plastic-brittle transition temperature. Similarly, with the increase of nitrogen content, the critical yield stress of molybdenum alloy decreases sharply, and the plastic-brittle transition temperature also rises sharply, indicating that the presence of high content of oxygen and nitrogen in molybdenum alloy can seriously affect the mechanical properties of molybdenum alloy.

In the manufacturing process of the molybdenum alloy target of the present invention, adjusting the proper amount of C in the molybdenum alloy can effectively improve the plasticity of the molybdenum alloy material and lower the plastic-brittle transition temperature. The main reason is because the carbon in the molybdenum alloy will form Mo ₂ C, MoC and other compounds, Mo ₂ C with a molybdenum substrate has a strong binding force, the presence of Mo ₂ C can effectively strengthen relatively weak binding polymorph interface , reducing the tendency of brittle fracture along the crystal, so that the plasticity of the polycrystalline molybdenum material is improved. In addition, during the annealing or cooling process, using the strong binding energy between C and O, C can also inhibit the segregation of O to the grain boundary, thereby further reducing the influence of impurity element O on molybdenum plasticity. As shown in Table 2 and Table 3, the effect of the carbon-oxygen content ratio of the present invention on the transverse bending elongation of the molybdenum-niobium alloy, when the carbon-oxygen atomic ratio is above 2:1, the molybdenum alloy can exhibit better plasticity.

The lateral bending elongation rate η of the present invention is calculated as shown in Equations 1 and 2. Where R is the bending radius, mm; d is the sample thickness, mm. On a stainless steel block of 10 dimensions (length × width × height) of 50 mm × 40 mm × 20 mm, the cutting radius is 1 000, 400, 200, 133.33, 100, 66.67, 50, 33.33, 25 and 20 mm, respectively. The arc. The cross section of the sample extension rod to be measured is cut into a molybdenum strip of length × width × 10 mm × 4 mm × 2 mm, and placed in a steel mold of R = 1000 mm to be slowly pressed to bend the molybdenum strip, and then, sequentially placed in R Bend in the smaller steel mold until the molybdenum strip breaks and note the radius at break. Since the upper strain number is the largest when the sample is bent, the alloy plasticity is evaluated by calculating the maximum deformation amount, and the transverse plasticity formula is Equation 1:

It can be seen from Fig. 3 that a certain proportion of carbon and oxygen atoms are added to the molybdenum alloy. As the annealing temperature increases, the grain boundary of MoNb-C can gradually grow into a uniform perfect shape, such as an elliptical shape, which is annealed at 1500 ° C to 1600 ° C. When the alloy has the highest transverse bending elongation, it reaches 5%.

As shown in Fig. 3, the molybdenum alloy target of the present invention has the following advantages: 1. The crystal grains are relatively dense, and the film thickness uniformity after sputtering is better than the conventional one (as shown in Fig. 4). The shape of the grain target is good; 2. The elliptical grains are staggered to prevent the grain boundary from sliding, so that the target is not easily cracked during mechanical forming (for example, wire cutting);

Compare the efficacy of the prior art:

1. The method of the present invention comprises mixing molybdenum powder with at least one metal element selected from the group consisting of Ti, Cr, Nb and Ta groups and powder of C, and directly heating and pressurizing the alloy powder into an alloy blank by hot isostatic pressing. It is not necessary to use the CIP machine to press the raw material powder without the need to prepare the molybdenum alloy target as in the prior art. After the green embryo is formed, it is crushed to make a secondary powder, and after the sintering is completed, the target embryo does not need to be subjected to multiple processes such as hot rolling, which is less than the conventional steps of the molybdenum alloy target, and can reduce the molybdenum alloy target. Production cycle and production cost. The crystal grain of the molybdenum alloy target of the invention is denser than the prior art, the film thickness uniformity after sputtering film formation is good, and the crystal grains are staggered, which can prevent the grain boundary sliding, so that the target material is not easily broken during mechanical processing. .

2. In the manufacturing process of the molybdenum alloy target of the present invention, an appropriate amount of C is adjusted in the molybdenum alloy, which can effectively improve the plasticity of the molybdenum alloy material and reduce the plastic-brittle transition temperature. In addition, during the annealing or cooling process, using the strong binding energy between C and O, C can also inhibit the segregation of O to the grain boundary, thereby further reducing the influence of impurity element O on molybdenum plasticity. When the carbon-oxygen atomic ratio is above 2:1, high-purity molybdenum exhibits good plasticity.

The present invention has been described with reference to the preferred embodiments of the present invention. However, those skilled in the art can change and modify the present invention without departing from the spirit and scope of the invention. Such changes and modifications shall be covered in the scope defined by the following patent application.

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Claims (7)

A method for preparing a molybdenum alloy target, the steps of which are: (1) dividing the quantitative molybdenum powder with at least one metal element selected from the group consisting of Ti, Cr, Nb and Ta groups into at least three portions, and then each molybdenum powder and The at least one metal element selected from the group consisting of Ti, Cr, Nb and Ta groups is separately mixed with the powder of C to form a small mixed powder, and each small portion of the mixed powder is divided into at least three groups, then separately mixed and finally combined, and then Mixing all the mixed powder into a uniform alloy powder; (2) adding the alloy powder to a pressurized container, degassing the pressurized container under vacuum, and sealing the degassing hole; (3) using HIP (hot) Isostatic pressing, hot isostatic pressing) pressurizing, heating, and adding oxygen to the pressurized container to make the alloy powder into an alloy embryo; (4) annealing the alloy embryo in a high temperature furnace; (5) The alloy embryo is cut, refined and machined into a finished molybdenum alloy target. The method for producing a molybdenum alloy target according to claim 1, wherein at least one metal element powder selected from the group consisting of Ti, Cr, Nb and Ta groups has an atomic percentage of 1 to 50%, and the balance is molybdenum. The method for preparing a molybdenum alloy target according to claim 1, wherein the HIP machine operation is divided into three temperature zones; respectively, 0 to 800 ° C, 800 to 1600 ° C, and 1600 to 2000 ° C, and each temperature zone is sintered at least 3 hour. The method for producing a molybdenum alloy target according to claim 1, wherein the alloy billet is annealed in a high temperature furnace, and the temperature of the high temperature furnace is 1500 to 1600 °C. The method for preparing a molybdenum alloy target according to claim 1, wherein the shape of the finished molybdenum alloy target is a flat plate. The method for preparing a molybdenum alloy target according to claim 1, wherein the shape of the finished molybdenum alloy target is a round tube. The method for producing a molybdenum alloy target according to claim 1, wherein the grain boundary of the finished molybdenum alloy target is elliptical.