The cost of optical interconnects determine their application scope. For cost-efficient integration of electro-optical transceivers all components need to be integrated on chip. The roadmap of electro-optical integration is shown in the figure below. Today, silicon photonics integration is versatile and already mostly cost-efficient. However, due to the indirect bandgap of silicon, active optical components such as lasers cannot be realized efficiently on this material system. Therefore, allways additional materials are required for the (external) laser sources which will be included into a hybrid packagage together with the electronics and silicon photonic parts. This also leads to higher (coupling) losses and makes the system more expensive again. In research also a semi-hybrid hybrid III-V-on-silicon integration approach of laser sources with silicon photonic and electronic parts have been demonstrated. However, the highest cost- and performance-efficiency can only be achieved if all components are integrated on the same chip. In this regard DIMENSION develops a BREAKTHROUGH integration technology which enables the processing of III-V devices at silicon level. Thus, laser sources, photonics and electronics can be fabricated on the same chip.
For the combination of (Bi)CMOS electronics, photonics and III-V on a single chip, DIMENSION develops a new technology platform for monolithic electro-optical integration. This enables integrated devices, with CMOS, photonic and III-V functionality at the cost of silicon volume fabrication. The integration concept, which has already been IP protected, is shown in the figure below. It constists of the following approach:
Fabricating the electronics and silicon photonics back-end-of-line in BiCMOS technology.
Applying the first inter-layer dielectric (ILD1), followed by a surface planarization scheme (e.g., chemical-mechanical polishing) and molecular wafer-bonding.
Patterning of the active III-V layers to form active devices, such as laser sources.
Metallization to interconnect the active III-V devices with the BiCMOS electronics. Further electrical interconnection levels are applied forming fully integrated electro-optical circuits.
This processing sequence clearly demonstrates the fully integrated nature of the III-V-on-silicon technology as well as the true CMOS nature of the process – going far beyond compatibility. DIMENSION for the first time will pursue the monolithic integration of electronics, passive silicon photonics with III-V-based active optical devices, such as directly modulated lasers.