Can silicon carbide target be DC sputtered? From semiconductors to optoelectronic materials, a comprehensive interpretation of future trends

1. Feasibility analysis of silicon carbide target in DC sputtering
2. The relationship between the electrical conductivity of silicon carbide and DC sputtering

1.1 Material characteristics analysis of silicon carbide

Silicon carbide is a wide-band gap semiconductor with many excellent physicochemical properties, such as high hardness, high melting point, good thermal stability, and excellent chemical inertness. These properties make it useful in semiconductor devices, high-temperature structural materials and optoelectronic materials. However, the electronic structure of SiC determines its low conductivity, especially in the case of undoped, which becomes a major technical obstacle in DC sputtering.

Dc sputtering requires the target to have sufficient conductivity to maintain a stable electric field during sputtering. For materials with poor electrical conductivity, such as silicon carbide, because the charge cannot be quickly derived, it is easy to form accumulation on the surface of the target, resulting in the abnormal enhancement of the local electric field of the target, which may eventually lead to arc discharge or even target breakdown. This phenomenon not only affects the sputtering efficiency, but also leads to uneven film quality and even defects.

1.2 Discussion on methods for improving electrical conductivity

In order to overcome the above challenges, researchers mainly improve the electrical conductivity of silicon carbide through doping technology. Doping is a method by which a small amount of impurity elements (such as nitrogen, phosphorus, aluminum, etc.) are introduced into the SiC crystal structure to improve its electrical conductivity. Specifically, adding nitrogen or aluminum can increase the concentration of free carriers (electrons or holes), thereby reducing the resistivity of SiC. For example, N-type SiC can significantly increase its electron concentration by incorporating nitrogen or phosphorus, making it more suitable for DC sputtering.

In addition to traditional doping methods, the feasibility of composite targets is also investigated. By combining silicon carbide with a metal material with better electrical conductivity (such as titanium, aluminum or copper) to form a composite target, not only can the excellent properties of SiC be retained, but also the electrical conductivity can be significantly improved. This kind of composite target can show more stable electric field distribution and reduce charge accumulation during DC sputtering, thus improving sputtering efficiency and film uniformity.

1.3 Doping and practical application of composite materials

In practical applications, doped silicon carbide targets and composite targets have shown good potential. For example, in the preparation of some high-temperature electronic devices, nitrogen-doped SiC targets have been successfully applied to DC sputtering to prepare high-quality films. In addition, SiC and metal composite targets also show superior performance in the preparation of photoelectric materials, especially in the manufacture of leds and lasers, these films have excellent thermal conductivity and electrical properties.

In summary, through doping and composite technology, the electrical conductivity of silicon carbide has been effectively improved, making its application in DC sputtering possible. However, these technologies also bring new challenges, such as the uniformity of doping, the interface compatibility of composite materials, etc., which need to be focused on in future research.

2. Possible problems and solutions during sputtering

2.1 Target breakdown problem and its causes

Target breakdown is a serious problem during DC sputtering, especially when using poorly conductive materials such as SiC. Breakdown is usually caused by excessive accumulation of charge on the surface of the target, resulting in excessive local electric field strength. When the electric field strength exceeds the dielectric strength of the material, it will cause arc discharge, resulting in partial damage or complete breakdown of the target. This not only interrupts the sputtering process, but also causes damage to the uniformity and integrity of the film.

2.2 Target breakdown prevention and solutions

In order to reduce or avoid target breakdown, the researchers proposed a variety of solutions:

Optimizing sputtering parameters: By reducing the sputtering voltage and power, the electric field strength can be effectively reduced, reducing the risk of breakdown. At the same time, pulsed DC sputtering technology reduces charge accumulation by periodically interrupting the electric field, allowing surface charges to dissipate during each pulse gap.

Target pretreatment: Surface pretreatment of SiC targets before sputtering, such as ion beam cleaning or plasma treatment, can remove oxides or contaminated layers on the surface, thereby reducing the formation of non-conductive areas. In addition, the surface polishing treatment of the target can also further reduce the possibility of breakdown by reducing surface defects and reducing the abnormal enhancement of local electric fields.

Auxiliary field application: During the sputtering process, an auxiliary magnetic field or electric field can be applied to change the surface electric field distribution to avoid excessive local electric field. Magnetron sputtering technology makes the movement of sputtered ions on the surface of the target more uniform through the guidance of the magnetic field, reducing the local accumulation of charge, thereby reducing the risk of breakdown.

2.3 Surface contamination problems and solutions

Surface contamination is another problem that can occur when using SiC targets for DC sputtering. Contaminants may come from residual gases in the vacuum chamber or other materials in the equipment, which can form a non-conductive layer on the surface of the target, affecting the electric field distribution during sputtering and the quality of the film.

Solution：

Maintain a high vacuum environment: During sputtering, maintain a high vacuum in the vacuum chamber to reduce the influence of residual gases. Chamber cleanliness can be further improved by changing the vacuum pump oil more frequently or using a higher grade vacuum pump.

Regular equipment maintenance: Regular cleaning and maintenance of sputtering equipment, especially target fixtures and electrode parts, to avoid contamination caused by equipment aging or residue accumulation.

Target surface protection: When the target is not in use, take appropriate protective measures, such as the use of protective cover or dust film, to avoid impurities in the environment attached to the surface of the target.

2.4 Sputtering uniformity problem and solution

Sputtering uniformity directly affects the thickness and composition uniformity of the prepared films. For SiC target, the uneven electrical conductivity or the complexity of surface topography may lead to the uneven distribution of electric field during sputtering, thus affecting the uniformity of the film.

Solution：

Rotating the target: By rotating the target, you can ensure that sputtering is carried out more evenly across the various areas of the target surface, thereby improving the uniformity of the film.

Optimize the distance between the target and the substrate: By adjusting the distance between the target and the substrate, the flight path of the sputtered particles can be changed, and the electric field distribution can be optimized, thereby improving the sputtering uniformity.

Application of magnetron sputtering technology: Magnetron sputtering technology can guide sputtering ions through an external magnetic field, so that they are evenly distributed on the surface of the target, so as to improve the stability of the sputtering process and the uniformity of the film. This technique is particularly suitable for handling materials with poor electrical conductivity, such as SiC.

1. B. Application prospect of DC sputtering of silicon carbide target
2. Application in semiconductor device manufacturing

1.1 Advantages of silicon carbide and requirements for semiconductor devices

Silicon carbide is an ideal material for high power, high frequency and high temperature electronic devices because of its wide band gap, high breakdown voltage, high thermal conductivity and excellent radiation resistance. Traditional silicon materials are prone to performance degradation under high temperature and high electric field conditions, while silicon carbide can maintain stable electrical properties under extreme conditions. As a result, SiC has gradually replaced traditional silicon-based materials in power electronics, radio frequency devices and high temperature sensors.

Through DC sputtering technology, SiC can be precisely deposited on different types of substrates to prepare high-performance films that play a key role in the manufacture of semiconductor devices. For example, in the manufacture of power semiconductor devices such as Schottky diodes and metal-oxide-semiconductor field-effect transistors (MOSFETs), SiC films can significantly improve the efficiency and reliability of the devices.

1.2 Typical Application Scenarios

Power electronics: SiC power devices, due to their higher power density and lower switching losses, have great application prospects in electric vehicles, renewable energy systems, and smart grids. The SiC film prepared by DC sputtering can not only reduce the on-loss of the device, but also increase the breakdown voltage, and significantly improve the performance of the power electronic system.

High temperature sensors: The thermal stability of SiC makes it an ideal choice for sensor materials in high temperature environments. For example, in the monitoring of aircraft engines, SIC-based sensors can provide reliable data in high temperature and corrosive environments to ensure the safe operation of the engine. Dc sputtering technology can form a uniform SiC film on the sensor substrate, thus ensuring the sensitivity and reliability of the sensor.

Rf devices: Because SiC has lower power loss and higher operating frequency, it is increasingly used in RF power amplifiers. By DC sputtering, SiC films can be used as the active layer in high-frequency devices, significantly improving the performance of devices, especially in 5G communication and radar systems.

2. Application in the preparation of advanced photoelectric materials

2.1 Unique advantages of SiC in optoelectronic devices

In the field of optoelectronics, SiC has also shown strong application potential. Its wide-band gap characteristics give it a significant advantage in the manufacture of high-power optoelectronic devices such as leds and lasers. Especially in environments where high temperatures or high power are required, SiC materials can effectively reduce the influence of thermal effects on optical properties.

Dc sputtering technology provides the possibility for the preparation of SiC films with high precision, so that these optoelectronic devices can still maintain high photoelectric conversion efficiency and stability under extreme conditions. For example, the use of SiC films as a buffer layer for light-emitting diodes (leds) can improve the luminous efficiency and lifetime of the device while reducing thermal attenuation. In addition, the application of SiC films in lasers can improve the energy output and stability of the laser, especially in the field of high-power lasers has a wide range of application prospects.

2.2 Specific Application fields

High power LED: The wide band gap characteristics of SiC make it ideal for use as a substrate or buffer layer for high power leds. Through DC sputtering technology, high-quality SiC films can be prepared on sapphire or silicon carbide substrates, thereby improving the electrical and optical properties of leds, significantly increasing their luminous efficiency and service life. This is of great significance for the development of solid-state lighting and display technology.

Laser film: SiC film plays a key role in lasers, especially in semiconductor lasers, SiC as a buffer or protective layer can improve the thermal management ability of the laser and reduce the influence of thermal effects on the laser output. In addition, SiC films can be used to manufacture mirrors and other optical components in high-power lasers, which require extremely high thermal conductivity and chemical stability to ensure the stability and lifetime of the laser at high power outputs.

Photodetectors: The high breakdown voltage and wide band gap of SiC materials make them ideal for photodetectors. Dc sputtering technology can accurately deposit SiC films on the substrate, thereby improving the optical responsiveness and signal-to-noise ratio of the detector, which is especially suitable for ultraviolet and X-ray detection.

3. Challenges and prospects in industrial scale production
   • Technical challenges of large-scale production

Although the application prospect of SiC target films prepared by DC sputtering is broad, there are still many challenges in the process of realizing industrial production.

Target cost: The preparation cost of high-purity SiC targets is higher, mainly due to the difficulty of production of SiC itself and the strict requirements for target purity. In order to reduce costs, it is necessary to develop more cost-effective SiC preparation technologies while improving the utilization rate of the target material.

Equipment compatibility: At present, many DC sputtering equipment is designed for metal or metal oxide targets, and equipment adjustment or improvement may be required when using SiC targets to adapt to their special physical and chemical properties. Especially for the low conductivity of SiC targets, the power system and magnetron system of the device may need to be specially optimized.

Batch stability: In industrial-scale production, batch to batch consistency is critical to product quality. In order to ensure the uniformity and stability of SiC films, it is necessary to strictly control the sputtering parameters during the production process, such as the pre-treatment of the target, the sputtering power, and the substrate temperature. This requires the establishment of a sound process control flow, and a large number of experiments to verify the repeatability and stability of the process.

• Future development trend

With the continuous advancement of SiC material technology, it is expected that its challenges in industrial scale production will be gradually solved. Here are some possible future trends:

Cost reduction: Through process optimization and economies of scale, it is expected that the production cost of high-purity SiC targets will gradually decrease. This will open the door to more application scenarios, especially in consumer electronics and large-scale industrial applications.

Equipment upgrade: With the deepening of research on SiC sputtering process, there may be DC sputtering equipment designed specifically for SiC materials in the future, which will be more efficient and stable, and can meet the needs of large-scale production.

Development of new material systems: Researchers may be able to develop more diverse SiC composite targets that not only have excellent electrical conductivity, but also retain all of the excellent properties of SiC, providing a wider choice for industrial applications.

Application field expansion: With the breakthrough of cost and technology, the application of SiC targets will gradually expand from high-end fields to a wider range of industrial applications, such as new energy, aerospace, intelligent manufacturing, etc., bringing new technological innovation and market opportunities to related industries.