The essential difference between target materials and ordinary metals: the functionalization revolution and the advancement of materials science
Release time:
2025-06-11
In thin film preparation techniques such as physical vapor deposition (PVD), the target material is bombarded by high-speed, high-energy particles. When high-energy particles strike the surface of the target material, atoms or molecules of the target material detach from the target and deposit on the substrate surface in gaseous form, thereby forming a thin film with specific functions.
In the vast field of materials science, targets and ordinary metals, while both belonging to the category of metallic materials, exhibit significant differences in many key aspects. Targets, as a type of material with special uses, play a pivotal role in modern high-tech industries, while ordinary metals, with their common characteristics, are widely used in various basic fields. A thorough exploration of the differences between the two not only helps us clarify the properties and application scenarios of different materials, but also provides theoretical basis and practical guidance for the development of related industries.
I. Definition and Concept
Ordinary Metals
Ordinary metals usually refer to metallic materials that are relatively common in nature, relatively abundant in reserves, and widely used in daily production, life, and traditional industrial fields. Iron, aluminum, copper, zinc, and lead all belong to ordinary metals. They possess the general characteristics of metals, such as good electrical conductivity, thermal conductivity, and ductility, have a metallic luster, and can undergo metal chemical reactions to a certain extent. Taking iron as an example, iron is an extremely abundant metal on Earth and is the main raw material for the steel industry. By adding an appropriate amount of carbon and other alloying elements to iron, various steels with different properties can be manufactured, widely used in construction, machinery manufacturing, transportation, and many other fields. Aluminum, with its low density and corrosion resistance, is often used in aerospace, architectural decoration, and packaging industries. For example, aircraft fuselages and engine components often use aluminum alloy materials, taking advantage of aluminum's lightweight and high-strength properties.
Targets
Targets are materials bombarded by high-speed, high-energy particles in thin film preparation techniques such as physical vapor deposition (PVD). When high-energy particles strike the surface of the target, target atoms or molecules detach from the target and deposit on the substrate surface in gaseous form, forming a thin film with specific functions. Targets are extremely diverse, encompassing metallic targets (such as pure aluminum, titanium, copper, tantalum, etc.), alloy targets (such as nickel-chromium alloys, nickel-cobalt alloys, etc.), and ceramic compound targets (such as oxides, silicides, carbides, sulfides, etc.). These targets play an indispensable role in high-tech fields such as semiconductor chip manufacturing, display panel production, solar cell preparation, and magnetic recording storage. For example, in semiconductor chip manufacturing, copper targets are sputtered to form highly conductive copper wiring on the wafer surface, constructing the complex circuit structure inside the chip and realizing various functions of the chip.
II. Purity Requirements
Ordinary Metals
In most conventional applications, the purity requirements for ordinary metals are not extremely stringent. Generally, a purity of 95% - 99%, sometimes even lower, can meet the needs. Taking construction steel as an example, it contains a certain amount of carbon and other impurity elements. The different carbon content and the type and content of alloying elements determine the different properties and uses of the steel. Common construction reinforcing bars do not have extremely high purity but achieve good strength and toughness through reasonable component control to meet the mechanical requirements of the building structure. In the field of mechanical manufacturing, some ordinary metal materials used for mechanical parts also allow for certain impurities, which have a relatively small impact on the material's properties within a reasonable range, while also reducing production costs. For example, ordinary cast iron contains a relatively large amount of carbon and other impurities, but it has good casting properties and low cost, and is widely used in manufacturing various mechanical bases, housings, and other parts.
Targets
Targets have extremely stringent purity requirements, especially in high-end applications. Generally, the purity of semiconductor-grade targets must reach 99.999% (5N) or higher, and some advanced processes even require 99.9999% (6N) or higher purity. This is because impurities in the target will seriously negatively affect the performance of the resulting thin film during the thin film deposition process. In semiconductor chip manufacturing, even trace amounts of impurities can cause short circuits, leakage current, or affect electron mobility inside the chip, thereby reducing chip performance, reliability, and yield. Taking the copper interconnection process using copper targets in chip manufacturing as an example, if the copper target contains trace amounts of iron, zinc, and other impurities, these impurity atoms will become electron scattering centers in the copper film, increasing resistance and affecting the chip's signal transmission speed and power consumption. In high-end display panel production, indium tin oxide (ITO) targets used to prepare transparent conductive electrodes also require extremely high purity, otherwise, the transmittance of the panel will decrease, and the conductivity will be uneven, affecting the display effect.
III. Microstructure and Performance
Ordinary Metals
The microstructure of ordinary metals is relatively simple and rough. The grain size is usually large. In terms of macroscopic properties, ordinary metals mainly focus on meeting basic mechanical performance requirements, such as strength, hardness, and toughness, to adapt to different application scenarios. For example, steel used in building structures needs to have high strength and good toughness to withstand the building's self-weight and various external loads, preventing fracture during use. In this case, the microstructure of the steel is mainly composed of ferrite and pearlite. By controlling the rolling process and heat treatment process, the ratio and morphology of ferrite and pearlite can be adjusted to optimize the mechanical properties of the steel. For example, copper used to manufacture wires and cables mainly focuses on its good conductivity and certain flexibility. In this case, the microstructure of the copper has a greater impact on conductivity, and it is generally hoped that the copper has a larger grain size to reduce the obstruction of grain boundaries to electron transport, thereby reducing resistance and improving conductivity.
Targets
The microstructure of targets requires extremely fine and strict control. The grain size of targets is often at the micrometer or even nanometer level, and there are strict requirements for grain orientation, uniformity, and internal defects. These microstructural characteristics directly determine the behavior of the target during the sputtering process and the quality of the prepared thin film. For semiconductor chip manufacturing targets, nanometer-scale grain size can greatly improve the uniformity of the thin film, significantly reduce defects in the thin film, and thus improve the accuracy and consistency of thin film deposition in chip manufacturing, which is crucial for improving chip yield and performance. For example, in the manufacturing of very-large-scale integrated circuits, high-quality metal thin films need to be formed by sputtering cobalt targets as interconnects. The microstructure factors of the cobalt target, such as grain size, orientation, and internal defects, will directly affect the conductivity, stress state, and interface bonding performance with other materials of the cobalt film, thereby affecting the electrical performance and reliability of the chip. In display panel manufacturing, the uniformity of the microstructure of molybdenum targets used to prepare electrode wiring films has an important impact on the deposition rate and distribution uniformity of molybdenum atoms during sputtering, which in turn determines the thickness uniformity and electrical properties of the electrode wiring film, ultimately affecting the display quality and stability of the display panel.
IV. Manufacturing Process
Ordinary Metals
The manufacturing process of ordinary metals is relatively mature and conventional. It usually includes ore mining, beneficiation, smelting, refining, and subsequent processing and forming. Taking steel manufacturing as an example, iron is first enriched from iron ore through beneficiation to obtain iron concentrate. Then, the iron concentrate is smelted in a blast furnace with raw materials such as coke and limestone, and pig iron is obtained through a high-temperature reduction reaction. After further steelmaking process, adjusting the carbon content and removing harmful impurities, different types of steel can be obtained. Subsequently, through processing processes such as rolling, forging, and casting, steel is made into products of various shapes and specifications, such as steel plates, steel bars, and steel pipes. In the production of aluminum, alumina is first extracted from bauxite, and then metallic aluminum is obtained by electrolyzing alumina. The obtained aluminum ingots can be processed into various aluminum profiles through extrusion, rolling, and other processing methods, and applied to the construction, automotive, and other industries. These manufacturing processes have been developed and improved for a long time, the technology is relatively stable, the production efficiency is high, and the cost is relatively controllable.
Targets
The manufacturing process of target materials is extremely complex and technologically advanced. Due to the strict requirements on the purity and microstructure of target materials, its manufacturing process involves a variety of advanced technologies and precise control. First, the purification of raw materials is a key step, and advanced chemical purification methods, such as zone melting, electrolytic refining, and vacuum distillation, are needed to increase the purity of the metal raw materials to the level required for target materials. Taking the preparation of high-purity copper target materials as an example, multiple zone meltings are required to enrich the impurity elements in copper to a specific area, thereby achieving separation from copper and improving the purity of copper. In terms of forming processes, commonly used methods include powder metallurgy and melting casting. Powder metallurgy is a method in which high-purity metal powder is processed into a target material blank through pressing and sintering, and then the final target material product is obtained through subsequent processing. This method can precisely control the composition and microstructure of the target material, but the process is more complex and the cost is higher. The melting casting method is to melt high-purity metal raw materials in a specific furnace and then cast them into a mold to form. In order to obtain the ideal microstructure, the temperature, cooling rate, and other parameters need to be precisely controlled during melting and casting, and post-processing processes such as hot isostatic pressing may also be used to further improve the density and microstructure of the target material. For example, when preparing titanium target materials for the semiconductor industry, the melting casting method is used. During the melting process, the temperature and composition of the titanium melt are strictly controlled. After casting, hot isostatic pressing is used to eliminate internal defects and improve the quality and performance of the target material.
V. Application Fields
Ordinary Metals
Ordinary metals, with their good comprehensive performance and relatively low cost, are widely used in various aspects of traditional industries and daily life. Iron, as the metal with the largest output, is the cornerstone of the construction industry. The steel bars in reinforced concrete structures provide the building with strong tensile strength, ensuring the structural safety of the building under various load conditions. In the field of mechanical manufacturing, steel is the main material for manufacturing various mechanical equipment, such as machine tools, automobile engines, and gears. Aluminum, due to its light weight and corrosion resistance, plays an important role in the aerospace field. The fuselage, wings, and other structural components of aircraft largely use aluminum alloy materials, which effectively reduces the weight of the aircraft, improves fuel efficiency, and improves flight performance. In the field of building decoration, aluminum alloy doors and windows, curtain walls, etc. are widely used, which are both beautiful and durable. Copper, due to its excellent conductivity and thermal conductivity, is the preferred material in the wire and cable industry. Whether it is the power transmission lines of urban power grids or the connecting wires inside electronic equipment, copper wires play a key role in conducting electricity. In the field of electrical appliance manufacturing, copper is also widely used to manufacture various electrical components, such as the windings of transformers and motors. Zinc is mainly used for galvanizing metal surfaces to improve the corrosion resistance of other metals. Galvanized steel sheets are widely used in the construction, automotive, and home appliance industries, extending the service life of metal products.
Targets
Target materials are mainly used in modern high-tech industries and are key materials for achieving high-performance and high-precision manufacturing in these fields. In the field of semiconductor chip manufacturing, target materials are the core materials for constructing the complex circuit structure inside the chip. By sputtering different target materials, such as copper targets for forming conductive lines and tantalum targets for making barrier layers, metal thin films are deposited layer by layer on the wafer surface. After a series of precise processes such as lithography and etching, chips with extremely high integration and excellent performance are finally manufactured. These chips are widely used in many fields such as computers, mobile phones, artificial intelligence, and the Internet of Things, driving the rapid development of information technology. In the display panel industry, target materials are also indispensable. For example, indium tin oxide (ITO) target materials are used to prepare transparent conductive electrodes for liquid crystal displays (LCDs) and organic light-emitting diode displays (OLEDs), which determine key performance indicators such as the transmittance, conductivity, and touch sensitivity of the panel. Molybdenum target materials, aluminum target materials, etc. are used to prepare electrode wiring films, which play an important role in the driving circuits and signal transmission of display panels. In the field of solar cells, target materials are used to prepare electrodes and functional films for batteries, such as copper indium gallium selenide (CIGS) alloy target materials used to manufacture thin-film solar cells, which improve the photoelectric conversion efficiency of solar energy and promote the development of the solar energy industry. In the field of magnetic recording, cobalt chromium alloys and other target materials are used to prepare magnetic films for hard disks, storing a large amount of data information to meet the high requirements of modern society for data storage and processing.
VI. Cost Difference
Ordinary Metals
Due to abundant reserves and mature mining and processing technologies, the production cost of ordinary metals is relatively low. Taking steel as an example, iron ore is widely distributed on the earth, and large-scale mining and efficient smelting technologies have resulted in huge steel output, and the price is relatively stable and low. The price of rebar used in construction is usually several thousand yuan per ton, and it can be widely used in various construction projects. Although the production of aluminum requires a large amount of electricity consumption, due to the abundant resources of its raw material bauxite and mature production technology, the price of aluminum ingots fluctuates within a relatively reasonable range, making aluminum alloy materials have high cost performance in many fields. The price of copper is relatively high, but due to its good performance and wide application, in industries such as wire and cable, through reasonable design and process optimization, the cost can also be controlled to a certain extent. The low cost of ordinary metals allows them to be widely used in large-scale industrial production and infrastructure construction, providing a solid material foundation for social and economic development.
Targets
Target materials are relatively expensive. On the one hand, target materials have extremely high requirements for the purity of raw materials. The purification process requires advanced and complex technologies and equipment, which greatly increases the cost of raw materials. For example, in order to meet the purity requirements of semiconductor-grade target materials, the purification process may require multiple zone melting and electrolytic refining operations. Each operation consumes a large amount of energy and specialized equipment, and also requires a high level of technical skill from the operators. On the other hand, the manufacturing process of target materials is complex. From raw material preparation to final forming, each link requires precise control and strict testing. The equipment investment is large, and the production efficiency is relatively low. For example, in the powder metallurgy method for preparing target materials, high-precision powder pressing equipment and sintering furnaces are required, and the temperature, pressure, and atmosphere parameters must be precisely controlled during the production process. Even slight deviations can lead to unqualified product quality. In addition, the scrap rate of target materials during the production process is relatively high, which further increases the cost. Since target materials are mainly used in high-end, high-tech industries, these industries have extremely high requirements for product performance and are willing to pay higher prices for high-quality target materials. However, overall, the high cost of target materials remains a significant limiting factor in their application and promotion.
