Magnetron sputtering technology is an important technique widely used for material surface modification and thin film deposition. As the core component of this technology, the performance and quality of magnetron sputtering targets directly affect the characteristics and applications of the prepared thin films. This article will provide a comprehensive and in-depth introduction to magnetron sputtering targets, including their definition, classification, preparation methods, performance requirements, application areas, and future development trends.
Magnetron sputtering target refers to a material that is sputtered with atoms or molecules by high-energy particles during the magnetron sputtering process, and then deposited onto a substrate to form a thin film. It is usually composed of substances with specific chemical compositions and crystal structures, such as metals, alloys, compounds, etc.
Sputtering target material process flow:
Raw material powder - powder smelting - powder mixing - compression molding - atmosphere sintering - plastic processing - heat treatment - ultrasonic testing - water cutting - mechanical processing - metallization - binding - ultrasonic testing - ultrasonic cleaning - inspection - shipment.
The specific meanings of the main processes are as follows:
Powder smelting: perform preliminary atmosphere sintering on raw material powder and control the gas content in the raw material powder.
Powder mixing: The target material has a unique formula that requires precise control of the content of each component and strict limitation of impurity content. In the process of powder metallurgy, it is necessary to fully mix all elements evenly, with uniform particle size distribution to prevent contamination, and to prepare mixed composite powder through special process methods.
Compression molding: The target material prepared by powder metallurgy process requires pre pressing of the powder material to make it a medium density green body. The uniformity of its density and internal defects affect the yield of high-temperature sintering in the later stage.
Atmosphere sintering: The pre pressed green body needs to undergo one or more high-temperature sintering processes. Different sintering temperature curves are selected according to different materials, and different sintering environments such as sintering atmosphere and pressure are chosen to prepare high-density target bodies.
Plastic processing: Metal ingots need to undergo significant plastic deformation to obtain sufficient length, width, and thickness dimensions, and to cause sufficient tensile deformation of the internal grains, thereby generating enough dislocations inside. Heat treatment: After undergoing significant plastic deformation, metal ingots are subjected to heat treatment processes that are selected based on the characteristics of different materials, resulting in recrystallization of the metal material and removal of internal stresses.
Ultrasonic flaw detection: After the target blank is processed, ultrasonic waves need to be used to inspect whether there are defects inside the material. After the target blank is bound to the back plate, a water immersion ultrasonic scanner needs to be used to detect the bonding layer and check whether the bonding area meets the standard.
Mechanical processing: The target blank needs to undergo precision mechanical forming processing for the back plate used in combination with the target blank. Due to the precise coordination with the coating equipment and the ability to withstand high-pressure water cooling, it requires extremely high dimensional accuracy and mechanical strength. The processing difficulty is high, especially for the back plate with internal circulation water circuit. Due to the special material, the closed welding of the water circuit is very difficult and requires special welding technology.
Metalization: Before binding the target blank to the backing plate, in order to enhance the wetting performance of the target material and the metal between the target material and the solder, it is necessary to perform pre-treatment on the bonding surface to coat it with a transition layer.
Binding: Due to the limited physical or chemical properties of the material, most target materials cannot be directly installed and coated for use. Metal solder is required to weld and connect the target blank to the backing plate, and the effective surface bonding rate needs to reach a large-area welding rate of over 95%. The entire process needs to be carried out at high temperature and high pressure.
Classification of Magnetron Sputtering Target Materials
1. Metal target materials: including pure metal target materials (such as copper, aluminum, nickel, etc.) and alloy target materials (such as stainless steel, aluminum alloy, etc.).
2. Compound target materials: such as oxide target materials (such as silicon dioxide, aluminum oxide, etc.), nitride target materials (such as silicon nitride, aluminum nitride, etc.), carbide target materials (such as silicon carbide, tungsten carbide, etc.), etc.
3. Semiconductor target materials: such as silicon target materials, germanium target materials, etc.
Classified by target material structure:
1. Flat target material: It has a simple planar structure and is commonly used in conventional magnetron sputtering equipment.
2. Rotating target material: It can achieve continuous rotation, improve the utilization rate of the target material and the uniformity of the deposited film
Performance requirements for magnetron sputtering targets:
(1) Purity
High purity target materials can ensure the purity and performance of deposited thin films. Generally, the purity of the target material is required to be above 99.9%.
(2) Density reduction
High density target materials can reduce particle contamination during sputtering and improve the quality and uniformity of thin films.
(3) Uniformity of chemical composition
The chemical composition of the target material should be evenly distributed to ensure the stability of the deposited film.
(4) Crystal structure
A suitable crystal structure helps to improve the sputtering efficiency of the target material and the performance of the thin film.
(5) Dimensional and Shape Accuracy
The size and shape of the target material should meet the equipment requirements to ensure good installation and sputtering effect.
(6) Thermal stability
During the sputtering process, the target material is subjected to high temperature and high-energy particle impacts, thus requiring good thermal stability.
(7) Corrosion resistance
The target material should have a certain degree of corrosion resistance to extend its service life.
At present, with the rapid development of industries such as electronic information and new energy, the market demand for magnetron sputtering targets continues to grow. Magnetron sputtering targets, as the core component of magnetron sputtering technology, have broad application prospects in modern industry. With the continuous advancement of technology and the continuous development of industries, the performance and quality requirements for magnetron sputtering targets will also continue to increase.
High performance: With the continuous improvement of film performance requirements in application fields, higher requirements have been put forward for the performance of magnetron sputtering targets, such as higher purity, density, uniformity, etc.
Diversification: With the continuous emergence of new application fields, the types and performance requirements of magnetron sputtering targets are also becoming more diversified, such as new semiconductor material targets, new compound targets, etc.
