Plasma can be classified from different perspectives, with various categorization methods. Typically, based on temperature differences, plasma can be divided into thermal plasma and non-thermal plasma; according to the degree of ionization, it can be categorized as fully ionized plasma or partially ionized plasma; depending on the environmental pressure conditions for plasma generation, it is classified into low-pressure plasma and atmospheric-pressure plasma. Regarding excitation methods based on operating frequencies, plasma is commonly categorized into direct current discharge, alternating current discharge, low-frequency discharge, radio frequency discharge, and microwave discharge. The frequency range for microwaves is 300 MHz to 300 GHz. The commonly used operating frequencies for microwave discharge are primarily 2.45 GHz and 915 MHz. These two frequencies—2.45 GHz and 915 MHz—are internationally allocated ISM (Industrial, Scientific, and Medical) bands for microwave applications.

Microwave plasma is generated by using electromagnetic waves in the microwave frequency band to excite gas molecules, promoting reactions such as electron excitation and ionization within the gas. The microwave frequency range (300 MHz to 300 GHz) offers moderate electromagnetic energy—sufficient to excite electrons in gas molecules without causing thermal decomposition. Additionally, microwaves exhibit strong penetration and efficient energy coupling. These characteristics enable effective energy transfer to gas molecules during plasma generation, enhancing ionization while maintaining high system stability and efficiency.  

Microwave plasma excitation does not require electrodes, though its discharge process still follows Paschen's Law. This law describes critical conditions for gas discharge. Although originally formulated for electrode-mediated discharges, Paschen's Law universally applies to collisional ionization processes between gas molecules, making it equally valid for microwave plasma systems lacking physical electrodes. By eliminating electrode wear and material contamination, microwave plasma technology—supported by advancements in solid-state microwave sources—offers flexible frequency and power adjustments, significantly broadening its applications.  

Compared to traditional DC, AC, or RF plasmas, microwave plasma achieves higher energy coupling efficiency and operates across a wider pressure range. Consequently, it holds significant value in diverse fields such as material processing, surface treatment, chemical reaction acceleration, exhaust gas conversion, and medical sterilization.

Atmospheric microwave plasma is a type of microwave plasma generated directly in an open ambient pressure environment, without the need for electrodes or complex vacuum systems. This means discharges can occur under atmospheric pressure and room temperature conditions, significantly reducing equipment investment and operational costs while simplifying system design and operational processes. Compared to low-pressure plasma, atmospheric microwave plasma offers a wider range of applications, lower operational costs, and simpler reaction systems. It is easier to integrate with existing industrial processes and laboratory conditions, bringing greater convenience and practical value to human industrial production and daily life.

Atmospheric microwave plasma can achieve chip etching and deposition under atmospheric pressure, with chip design precision reaching the nanometer level. This not only reduces reliance on chemical etchants but also enhances environmental sustainability. Compared to traditional low-pressure plasma processes, atmospheric microwave plasma technology eliminates the need for complex and expensive vacuum systems during treatment, effectively reducing overall production costs.

Atmospheric pressure microwave plasma can be applied to material surface treatments, such as surface cleaning, coating, and other processing procedures. Atmospheric pressure microwave plasma typically operates under non-thermal equilibrium conditions, transferring minimal heat to the treated materials during processing. This prevents excessive thermal impact on the overall material, making it highly suitable for thermally sensitive materials. Consequently, this technology enhances material performance and prolongs service life without requiring additional temperature or pressure equipment. Furthermore, atmospheric pressure microwave plasma can instantaneously generate high concentrations of reactive species that rapidly react with material surfaces, enabling swift completion of cleaning, activation, or coating processes. Compared to traditional surface treatment methods, atmospheric pressure microwave plasma treatment achieves faster speeds, higher efficiency, and lower costs.

Overall, compared with traditional plasma processing technologies, the advantages of atmospheric microwave plasma mainly lie in its simple operation, lower costs, ability to generate plasma under ambient temperature and pressure, and higher energy efficiency.