Semiconductor device and method for forming the same

A method for forming a semiconductor device, comprising:

• forming a seal ring structure, a plurality of first bonding features, and a first alignment mark at least partially overlapping the seal ring structure without overlapping the first bonding features in a top die;
• forming a plurality of second bonding features and a second alignment mark in a bottom wafer;
• attaching the top die to the bottom wafer via the first bonding features and the second bonding features;
• and
• aligning the top die with the bottom wafer using the first alignment mark and the second alignment mark,
• wherein in a top view, the first alignment mark comprises four patterns, and a shape of each of the patterns of the first alignment mark is substantially the same.

A semiconductor device, comprising:

• a top die comprising:
• a plurality of first bonding features;
• and
• a first alignment mark comprising a plurality of first patterns defining a first benchmark;
• and
• a bottom wafer comprising:
• a plurality of second bonding features in contact with the first bonding features;
• and
• a second alignment mark comprising a plurality of second patterns defining a second benchmark,
• wherein in a top view, a distance between two adjacent first patterns of the first alignment mark is less than a width of each of the first patterns of the first alignment mark, at least two of the first patterns are oriented along a first direction, and at least two of the first patterns are oriented along a second direction that is different from the first direction, and
• wherein the top die is aligned with the bottom wafer by adjustment of a virtual axis passing through the first benchmark and the second benchmark to be substantially parallel with the first direction.