## 7 Prospects, Expectations, and Future Development  
This comprehensive review synthesized the fundamental principles, technological implementations, and chemical specificities of plasma cleaning systems applied to semiconductor packaging processes. The conclusions of this paper can be initiated by discussing the summary of the parametric scoring achieved by each of the plasma cleaning sources. The comparative assessment of plasma sources, summarized in Table 21 reveals distinct operational characteristics influencing their suitability. While ECR microwave systems demonstrate superior potential for efficient chemical processing due to their ability to achieve high plasma densities and electron temperatures, this advantage is tempered by their significant operational complexity, arising from the need to precisely coordinate the static magnetic field with the microwave input, and their associated higher costs. In contrast, radio frequency (RF) sources, particularly ICP systems, offer a robust and often more practical balance of process control and density, explaining their widespread prevalence in industrial applications, especially those leveraging physical bombardment. Direct current (DC), dielectric barrier discharge (DBD), and dielectric coplanar surface barrier discharge (DCSBD) systems present simpler atmospheric-pressure alternatives, but often compromise on uniformity, stability, or energy density, limiting their application for high-precision semiconductor tasks where vacuum processing remains dominant for cleanliness and control. The choice of source is therefore not merely about achieving the highest parametric score, but involves balancing performance requirements with operational constraints and cost-effectiveness. Key findings from the comparative analysis indicate that advanced sources like ECR-microwave systems generally offer superior control over plasma parameters critical for effective cleaning, though RF systems remain widely used. A deeper analysis pertains to the selection of process gases, whose characteristics dictate the primary cleaning mechanism--chemical reaction or physical bombardment--and the ultimate surface condition. This is summarized in Table 22.  
As summarized in Table 22, oxygen stands out for its unparalleled efficacy in removing organic contaminants through oxidation, forming volatile by-products. However, its inherent tendency to oxidize the underlying lead frame metal, such as copper, necessitates careful process control or subsequent reduction steps. Conversely, hydrogen plasma excels at chemically reducing metal oxides, particularly copper oxides, and can offer a degree of surface passivation against re-oxidation. Its effectiveness, however, can be temperature-dependent, and potential hydrogen embrittlement requires management. For processes prioritizing physical cleaning, argon remains the industry workhorse. Its appropriate mass enables efficient sputtering for removing thin contaminants and surface oxides, and inducing surface roughening beneficial for adhesion, all without introducing chemical alteration or significant safety hazards. While heavier noble gases like xenon offer theoretically higher bombardment yields, their prohibitive cost restricts their use. Lighter noble gases like helium provide extremely gentle treatment. but suffer from low sputtering efficiency. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Type of System Source** & **Energy Distribution and Plasma Uniformity** & **Plasma Stability** & **Plasma Energy Density** & **Electron Heating** \\ \hline Direct Current and Pulsed Direct Current & & & & \\ \hline \end{tabular}
\end{table} 
Table 21: Summary of comparative assessment parametric scoring achieved by the various plasma cleaning sources based on the literature study.