Very interesting that this POET patent application was just published. I was just trying to learn more about the temperature limitations associated with LWLG packaging and their efforts to find a hermetic seal that can be processed at extremely low temp of 100’C as disclosed recently by the company to remove the need for a gold box.

Below is a statement from one of the LWLG patents:

A major problem that is present in the manufacture of such integrated circuits is that the semiconductor and polymer components will degrade or even fail when subjected to the moisture and gasses in the atmosphere. Prior art sealing methods generally include encapsulating the circuits in material that can be deposited over the entire circuit, such as silicon nitride or the like. This procedure introduces more problems in that the deposition generally requires high enough temperatures to damage the components. Also, it can be difficult to provide electrical contacts through the encapsulation and to provide optical pathways to allow optical communication through the encapsulation. Generally, attempts to reduce the encapsulation to allow electrical and optical communication, degrades the seal so that it is no longer hermetic, thereby causing eventual failure of the components.

POET uses pick and place tools to first insert all die one at a time in rapid succession into the 400 or so optical engines per wafer and fix them in place temporarily with an initial solder connection. Once all devices are placed the bonds are made permanent with a solder reflow of the entire wafer in one step. 278’C is the quoted temperature for this reflow. The hermetic seal is managed in a similar way as the cap is fixed in place at a lower temperature to avoid disturbing the permanent optical die bonds. 

This is a very general description of the process and I will need to spend a little more time to refresh my memory and go over the new patent publication.

My hope is to get off my butt and provide a POET story. Important details of just how remarkable the POET platform is should be provided for new eyes to digest.

The fact that POET’s waveguides are largely athermal  and are generally immune from wavelength drift requiring minimal temperature control. The ability to isolate and control the thermal signature of each device  such that the material set of that device is optimized individually. The monolithic approach associated with traditional silicon photonics requires all components to be co-optimized for temperature and material limitations with a resulting trade off of operating efficiencies.

Enjoy the day and as always spread the love.