In the broad field of materials science, targets play a key role. The target, or sputtering target, is the core material used for film preparation. They have a profound significance in the history of materials science, especially in the rise of the semiconductor and microelectronics industries, the application of targets became a revolutionary technology. Advances in thin film preparation techniques, such as magnetron sputtering and electron beam evaporation, rely heavily on the development and use of high-quality targets.

Metal target: Metal target is the most common class, including copper, aluminum, gold, silver, etc. The main characteristics of this kind of target are high conductivity and good thermal conductivity. In thin film preparation, metal targets are often used to create conductive films, such as conductive paths in electronic devices. The purity of the metal target is extremely high, usually above 99.99%, which is essential to ensure the uniformity and electrical properties of the film.

Oxide targets: Such targets include alumina, zinc oxide, etc., which are mainly used to prepare films with special electrical and optical properties. Oxide targets are particularly important in the semiconductor and photovoltaic industries because they enable the preparation of thin films with high dielectric constants, special optical properties or specific conductivity. These oxide films are widely used in sensors, photovoltaic cells and display technology.

Alloy target: Alloy target is a target made of two or more metal elements in accordance with a certain proportion, such as copper indium gallium selenium (CIGS) alloy target, mainly used in the manufacture of solar cells. The characteristic of the alloy target is that the properties of the film, such as conductivity, magnetic or optical properties, can be adjusted by changing the proportion of elements.

Rare earth target: Rare earth elements such as lanthanum and cerium are widely used in the manufacture of thin films with special functions due to their unique electronic structure. For example, rare earth targets are used in display technology to make light-emitting layers, or in data storage technology to make high-density storage materials.

Special synthetic target: This type of target is prepared by special chemical synthesis methods, such as the target of high temperature superconducting materials. They are often used in very specialized and high-end applications, such as the study of particle accelerator targets or high-temperature superconducting materials.

When selecting the target, it is necessary to consider not only its composition and purity, but also its physical and chemical stability, thermal expansion coefficient, melting point and other factors, which directly affect the deposition process and final properties of the film. In addition, the shape and size of the target also vary according to different film preparation technologies, which need to be customized according to the specific application requirements.

Magnetron sputtering: In this technique, the target is bombarded with particles to "sputter" atoms or molecules onto the substrate, forming a thin film. Here, the physical properties of the target, such as composition, density, and crystal structure, directly determine the deposition rate and uniformity of the film. For example, a uniform, dense metal target can provide a more consistent film coverage.

Electron beam evaporation: In this process, the electron beam is used to heat the target, causing it to evaporate and form a film on the substrate. The melting point and vapor pressure of the target are key factors, as they affect the evaporation rate and the uniformity of the film. Different targets also have different absorption efficiency of the electron beam, which further affects the deposition process.

Chemical vapor deposition (CVD) : In CVD, the target material, usually in the form of gas or vapor, reacts with other chemical reactants at high temperatures to form the desired film. Here, the chemical stability and reactivity of the target are the main considerations.

When selecting a target, in addition to considering its purity and chemical composition, it is also necessary to consider its compatibility with the film preparation technology used. For example, certain targets may perform well in magnetron sputtering, but not so well in electron beam evaporation. Therefore, a thorough understanding and proper selection of the target material is crucial to the quality and performance of the film.

Raw material selection: This is the starting point for target preparation. Selecting the right raw material is crucial to determining the basic properties of the target. For example, for metal targets, high purity metal is usually required; For oxide or alloy targets, the proportion of elements needs to be precisely controlled.

Powder metallurgy: Most of the targets are made by powder metallurgy technology. This involves crushing the raw material into a powder and then forming it by pressing. The particle size of the powder and the pressure during the molding process have significant effects on the density and uniformity of the target material.

Sintering: The target material after forming is subjected to a sintering process to enhance its mechanical strength and improve its microstructure. The sintering temperature and holding time have a profound effect on the final properties of the target.

Post-treatment: The sintered target often requires further processing, such as cutting, polishing and cleaning, to meet the size and surface quality requirements of the specific application.

Quality control: Strict quality control is essential throughout the preparation process. This includes testing the composition, density, purity and microstructure of the target material to ensure that it meets strict standards.

Each step needs to be precisely controlled, as any small deviation can affect the quality of the target and, in turn, the properties of the final film.

Semiconductor industry: In this industry, the application of targets is particularly critical. Silicon targets, for example, play a central role in making transistors for a variety of microelectronic devices. The purity and uniformity of the target material directly affect the performance of the transistor, which in turn affects the performance of the entire device.

Photovoltaic materials: In the production process of solar cells, such as the use of copper indium gallium selenium (CIGS) targets to manufacture absorption layers, which directly improves the conversion efficiency of solar cells. In this field, the precise chemical composition of the target determines the performance of the photovoltaic cell.

Display technology: For example, in the manufacture of liquid crystal display (LCD) or organic light-emitting diode (OLED), specific targets are used to deposit conductive and light-emitting layers, which have a direct impact on the color performance and efficiency of the screen.

These cases show that the target material has an irreplaceable role in many fields of modern science and technology. Target requirements vary from application to application, but all emphasize the importance of the quality of the target to the performance of the final product.