# Development Status of Key Technologies for Optoelectronic Integrated Circuit Manufacturing
## 3 Manufacturing of Optoelectronic Integrated Circuits
### Integration Method  
According to the integration method (technology), optoelectronic integrated circuits can be categorized into two types, namely, monolithic integration and hybrid integration [27; 28]. Monolithic integration is the direct growth of specific materials on substrate materials to integrate multiple optical and electrical components. Hybrid integration involves transferring independent optoelectronic components to the substrate material for interconnection through a certain process. From the comparison in Table 1, monolithic integration and hybrid integration exhibit distinct advantages. Because hybrid integration technology was developed earlier, the process is more mature, and the combination is flexible. Monolithic integration incorporates processes, reduces volume, improves integration, and reduces the effect of component interconnection. Monolithic integration technology exhibits advantages in terms of performance, cost, and mass production and is critical for the development of optoelectronic integration [29].  
Electrical integration technology should focus on the compatibility of manufacturing technology and the cross-integration with other disciplines. Existing optoelectronic integrated materials include lithium niobate (LiNbO\({}_{3}\)), silicon-on-insulator (Si), silicon dioxide (SiO\({}_{2}\)), silicon nitride (Si\({}_{3}\)N\({}_{4}\)), optical glass, polymers, and III-V semiconductor materials [30; 31], which exhibit distinct properties (Table 2). Lithium niobate exhibits excellent electro-optical modulation properties, polymeric materials require simple processing, and silicon materials allow for large-scale integration. For the development of optoelectronic  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{**Monolithic Integration**} & \multicolumn{2}{c}{**Hybrid Integration**} \\ \hline Features & \multicolumn{2}{c}{Optoelectronic components can grow on substrate materials directly} & \multicolumn{2}{c}{Optoelectronic components can transfer to substrate materials} \\ \hline Advantages & \(\bullet\) & High integration & \(\bullet\) & High process maturity \\  & \(\bullet\) & Small volume & \(\bullet\) & High flexibility in combination \\  & \(\bullet\) & Improve the integration & \(\bullet\) & Small effect of component interconnection \\ \hline Disadvantages & \(\bullet\) & Cannot be integrated with a single chip & \(\bullet\) & Low integration degree \\  & \(\bullet\) & Cannot be integrated with a single chip & \(\bullet\) & High cost \\  & & & \(\bullet\) & Poor connection between each component \\  & & & \(\bullet\) & Difficult to realize miniaturization \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of the advantages and disadvantages of monolithic integration and hybrid integration.  
integrated circuits, various materials should be devised to complete the system integration. In 2017, [PERSON] et al. [32] replaced the conventional optoelectronic integrated materials with materials mixed with graphene and silicon nitride and produced optoelectronic modulators with enhanced optical models, superior modulation efficiency, and considerably reduced functional consumption. Regardless of the materials in optoelectronic integrated circuits, they exhibit optical loss when integrated on a large scale. Therefore, in the future, the development of optoelectronic integrated circuits should focus on reducing the energy consumption required for optical transmission.