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High-purity Tantalum
High-purity tantalum is an important rare metal material with excellent physical and chemical properties. It is widely used in semiconductors, aerospace, medical and other fields.
Properties of high-purity tantalum
Chemical properties: Tantalum hardly reacts with chemicals at room temperature and has strong corrosion resistance, especially its resistance to hydrofluoric acid is very outstanding. This makes tantalum very popular in the manufacture of reactors, containers and other chemical equipment.
Physical properties: Tantalum is a heavy metal with a melting point of up to 2996°C. It has good ductility and toughness and can be processed into filaments or thin sheets. Its high melting point makes it stable even in high temperature environments.
Preparation method of high-purity tantalum
The preparation of high-purity tantalum usually involves the following steps:
Raw material selection: Tantalum is mainly extracted from niobium-tantalum ore, which is decomposed and purified to obtain pure tantalum compounds.
Reduction process: Tantalum powder can be prepared by metal thermal reduction or molten salt electrolysis. The commonly used method is to react potassium fluorotantalate with metallic sodium to obtain high-purity tantalum powder.
Target preparation: In order to produce high-purity tantalum targets, tantalum powder is first mixed, then cold pressed and vacuum hot pressed. This process can eliminate impurities that may be introduced in traditional methods and improve the crystal structure of the material, thereby improving the performance of the target.
Why is the purity requirement of high-purity tantalum
The purity requirement of high-purity tantalum mainly stems from its key applications in high-tech fields, especially in semiconductor and integrated circuit manufacturing. The following are important reasons for the purity requirement:
Affecting performance
Conductivity: The purity of tantalum directly affects its conductivity, and in semiconductor chips and thin film materials, the presence of any impurities may cause a decrease in conductivity, thereby affecting the overall performance of the device.
Material consistency: High-purity tantalum ensures the consistency of materials between batches, which is critical for precision manufacturing. Any slight change in impurities may lead to unstable product performance.
Application requirements
Integrated circuit targets: In integrated circuit manufacturing, the purity of high-purity tantalum targets is usually required to reach 4N5 (99.995%) or above, and for more advanced processes (such as 14nm technology), the purity requirement of tantalum even exceeds 6N5 (99.9999%). This reflects the continuous improvement of material purity requirements with technological advancement.
Control of impurities: In particular, there are strict control requirements for impurities such as alkali metals, alkaline earth metals and radioactive elements to prevent them from having a negative impact on the properties of semiconductor materials.
Purification Technology
The production of high-purity tantalum involves a complex purification process that usually combines chemical and physical methods to remove impurities and increase the purity of the metal. This includes techniques such as zone melting, vacuum distillation and electromigration, which can effectively reduce the impurity content in the metal to the required high purity level. In short, the strict purity requirements of high-purity tantalum are to ensure its performance and reliability in high-tech applications, especially in areas where the performance of electronic devices is critical.
The most critical step in the preparation of high-purity tantalum
In the preparation of high-purity tantalum, vacuum hot pressing sintering is the most critical step. This process directly affects the purity and performance of the final product.
The importance of vacuum hot pressing sintering
Process conditions: Vacuum hot pressing sintering needs to be carried out in an environment with a vacuum degree of more than 1Pa, and the sintering temperature is usually set between 1300℃ and 1800℃, and a pressure of more than 50MPa is applied. These conditions help to eliminate oxidation and impurities and ensure the high purity of tantalum.
Elimination of inherent texture bands: Through this step, tantalum powder is transformed into a dense tantalum block without reaching the melting point, avoiding the "inherent texture band" that may appear in traditional methods, thereby improving the consistency and performance of the material.
Uniformity and density: Vacuum hot pressing sintering not only ensures the high purity of the material, but also ensures the uniformity and density of the tantalum target, which is crucial for semiconductor applications because it directly affects the sputtering performance of the target.
Therefore, vacuum hot pressing sintering is an indispensable and extremely critical step in the preparation of high-purity tantalum.
The influence of "intrinsic texture band" of high purity tantalum on its performance
The "inherent texture bands" of high-purity tantalum have a significant impact on its performance, especially in semiconductor target applications.
The definition and formation of intrinsic texture bands
Intrinsic texture bands refer to specific crystal structures formed due to preferential slippage of grain orientation during tantalum processing. This structure is usually dominated by the (111) plane, resulting in uneven distribution of grains in the thickness direction.
Impact on performance
Sputtering performance: The inherent texture band will significantly reduce the sputtering rate and coating uniformity of the target. Due to the existence of preferential orientation, the target material may not be able to effectively release energy during the sputtering process, resulting in a reduction in the film deposition rate.
Film quality: Due to the influence of inherent texture bands, the generated films often have uneven thickness and unstable quality, which is unacceptable in semiconductor manufacturing with high precision requirements.
Process complexity: Traditional manufacturing methods require multiple plastic deformations and annealing in an attempt to improve grain orientation and eliminate texture bands, which not only increases production costs but also reduces yield.
Improvement methods
To eliminate inherent texture bands, modern manufacturing techniques such as powder metallurgy were introduced. This method can obtain a uniform and non-textured tantalum target through vacuum hot-pressing sintering and other processes, thereby improving its overall performance. This treatment not only reduces the grain size but also ensures consistent grain orientation, ultimately improving the target's efficiency and reliability in semiconductor applications.
In summary, the inherent texture bands of high-purity tantalum have a negative impact on its performance, especially in demanding applications. Its performance can be effectively improved by improving the manufacturing process.
Application fields of high-purity tantalum
High purity tantalum is widely used in many fields due to its superior performance, including:
Semiconductor industry: Tantalum targets are used to manufacture integrated circuits, especially as barrier materials in processes below 45nm.
Medical equipment: Tantalum is used to manufacture surgical instruments and artificial joints due to its biocompatibility.
Aerospace: Tantalum alloys are used to manufacture aircraft and missile components due to their high temperature resistance and strength.
High purity tantalum is a metal material with extremely high application value. Its unique physical and chemical properties make it play an important role in modern science and technology. Through advanced preparation technology, its purity and performance can be effectively improved to meet the strict requirements of various industries for materials.
