Method for assembling EIC to PIC to build an optical engine

An integrated circuit comprising:

• a first substrate comprising a first side and a second side;
• a circuit disposed on the first side;
• a first dielectric layer positioned on the circuit, the first dielectric layer comprising a first surface;
• a second dielectric layer positioned on the second side, the second dielectric layer comprising a second surface;
• a first metal layer embedded in the first dielectric layer, the first metal layer being coupled to the circuit;
• a second metal layer positioned on the first surface, the second metal layer being coupled to the first metal layer;
• a first contact coupled to the second metal layer;
• a via comprising a first end and a second end, the first end being coupled to the first metal layer and a second end being positioned on the second surface and coupled to the second dielectric layer;
• a second substrate comprising a third, a fourth side, and a trench, the trench comprising a sidewall and a bottom;
• a third dielectric layer positioned on the third side, the third dielectric layer comprising a third surface;
• a third metal layer positioned on the third dielectric layer;
• a second contact coupled to the third metal layer and positioned on the third surface, the second contact being coupled to the second end of the via, the second surface being contacted with the third surface;
• a fourth metal layer positioned on the fourth side and on the sidewall to couple to the third metal layer at the bottom;
• and
• a third contact coupled to the fourth metal layer.