Bonding structure with stress buffer zone and method of forming same

A method comprising:

• forming a first device structure comprising:
• depositing a first dielectric layer;
• forming a first metal pad in the first dielectric layer;
• and
• selectively etching an edge portion of the first metal pad to form a first recess;
• forming a second device structure comprising:
• depositing a second dielectric layer;
• forming a second metal pad in the second dielectric layer;
• and
• selectively etching an edge portion of the second metal pad to form a second recess;
• and
• bonding the second device structure to the first device structure, wherein the second metal pad is bonded to the first metal pad and the second dielectric layer is bonded to the first dielectric layer, wherein after the bonding a top surface of the first metal pad and a top surface of the second metal pad form a void therebetween.

A semiconductor device comprising:

• a first device structure comprising:
• a first dielectric layer;
• a first metal pad in the first dielectric layer;
• a first void at an edge portion of the first metal pad;
• a first dummy metal pad in the first dielectric layer;
• and
• a second void at an edge portion of the first dummy metal pad;
• and
• a second device structure comprising:
• a second dielectric layer in contact with the first dielectric layer;
• a second metal pad in the second dielectric layer and in contact with the first metal pad;
• a third void at an edge portion of the second metal pad;
• a second dummy metal pad in the second dielectric layer and in contact with the first dummy metal pad;
• and
• a fourth void at an edge portion of the second dummy metal pad.