Wafer bonding method and bonded device structure

A structure comprising:

• a first device comprising a first dielectric layer, a first bonding pad in the first dielectric layer, and a first alignment mark, the first alignment mark comprising a first magnetic cross;
• and
• a second device comprising a second dielectric layer, a second bonding pad in the second dielectric layer, and a second alignment mark, the second alignment mark comprising a second magnetic cross, the first magnetic cross being aligned with the second magnetic cross, the first bonding pad and the second bonding pad comprising a conductive material, the first alignment mark and the second alignment mark comprising a magnetic material, the magnetic material being different from the conductive material, the magnetic material having greater transparency than the conductive material at infrared light, the first dielectric layer bonded to the second dielectric layer by dielectric-to-dielectric bonds, the first bonding pad bonded to the second bonding pad by metal-to-metal bonds.

A structure comprising:

• a first device comprising a first dielectric layer and a first alignment mark in the first dielectric layer, the first alignment mark comprising a first magnetic cross, the first magnetic cross comprising first arms that protrude from a first central portion, a first pair of adjacent arms of the first arms forming a first north pole of the first magnetic cross, a second pair of adjacent arms of the first arms forming a first south pole of the first magnetic cross, each of the first arms having a first width, each of the first arms having a first length, the first length being different than the first width;
• and
• a second device comprising a second dielectric layer and a second alignment mark in the second dielectric layer, the second alignment mark comprising a second magnetic cross, the second magnetic cross comprising second arms that protrude from a second central portion, a first pair of adjacent arms of the second arms forming a second north pole of the second magnetic cross, a second pair of adjacent arms of the second arms forming a second south pole of the second magnetic cross, the first north pole aligned with the second south pole, the first south pole aligned with the second north pole.