Protection Structures for Bonded Wafers

A method comprising:

• forming a first wafer comprising:
• forming a plurality of dielectric layers;
• and
• forming a metal pipe penetrating through the plurality of dielectric layers, with portions of the plurality of dielectric layers encircled by the metal pipe forming a dielectric region;
• forming a second wafer comprising:
• forming a metal pad;
• and
• forming an etch stop layer over and contacting the metal pad;
• bonding the first wafer to the second wafer, wherein the metal pipe overlaps the metal pad;
• etching the first wafer and the second wafer to form an opening, wherein the dielectric region is removed in the etching, and the etching is stopped on a top surface of the etch stop layer;
• etching the etch stop layer;
• and
• forming a conductive plug in the opening.

A structure comprising:

• a first die comprising:
• a first semiconductor substrate;
• a plurality of dielectric layers underlying the first semiconductor substrate;
• a plurality of metal rings, each in one of the plurality of dielectric layers, wherein inner lateral dimensions of the plurality of metal rings are different from each other, and wherein the plurality of metal rings are stacked to form a metal pipe;
• and
• a first surface dielectric layer underlying the plurality of metal rings and the plurality of dielectric layers;
• a second die comprising:
• a second semiconductor substrate;
• a metal pad over the second semiconductor substrate;
• a second surface dielectric layer overlying the metal pad, wherein the first surface dielectric layer is bonded to the second surface dielectric layer;
• and
• a conductive plug penetrating through the first die to contact a top surface of the metal pad.