Integrated optoelectronic device with optical interconnect structure for improved BEOL device integration

A method for fabricating an optoelectronic device, the method comprising:

• performing front-end-of line, hereinafter FEOL, processing to provide a silicon-on-insulator, hereinafter SOI, substrate with a silicon layer arranged above a buried oxide layer and comprising one or more electronic components and with a FEOL optical waveguide formed in the silicon layer, wherein a FEOL coupling section is fabricated in the FEOL optical waveguide;
• performing back-end-of-line, hereinafter BEOL, processing to fabricate an interconnect stack on the substrate, the BEOL processing comprising
• fabricating a plurality of metal levels of the interconnect stack, which contain structured metal connect traces and are separated from each other by an interlevel dielectric material, the metal levels being named by order numbers counting incrementally with increasing vertical distance from the substrate and starting with a first metal level that is the one closest to the silicon layer of the substrate, up to a top metal level at a highest vertical distance from the substrate;
• and
• fabricating a photonic component arranged in the interconnect stack at a vertical distance from the substrate larger than that of the second metal level;
• and
• fabricating an optical coupling region that extends between a BEOL coupling section and the FEOL coupling section and comprises an optical interconnect structure arranged and configured for optically coupling radiation from the BEOL coupling section into the FEOL coupling section and vice versa;
• wherein fabricating the optical interconnect structure comprises
• fabricating a vertical stack of optically coupled waveguide elements made of a first dielectric material, which each are embedded in a second dielectric material and which in a desired wavelength range have an index of refraction of a higher value than the embedding second dielectric material;
• and
• arranging and configuring the optically coupled waveguide elements for
• receiving optical radiation in the desired wavelength range from the BEOL coupling section or the FEOL coupling section by coupling the optical radiation into at least one of the waveguide elements,
• cooperatively forming and sustaining, using the coupled optical radiation, one or more supermodes of optical radiation, each of the one or more supermodes being a superposition of modes of all of the at least two optically coupled waveguide elements, and for
• coupling optical radiation of the one or more supermodes into the FEOL coupling section or the BEOL coupling section, respectively.