Seamless bonding layers in semiconductor packages and methods of forming the same

A package comprising:

• a first semiconductor die including:
• a semiconductor substrate;
• a plurality of metal pads over the semiconductor substrate;
• a first passivation layer over the plurality of metal pads, wherein the first passivation layer has a first sublayer and a second sublayer over the first sublayer, wherein a density of the second sublayer is greater than a density of the first sublayer;
• a first bonding layer over the first passivation layer;
• a second bonding layer over the first bonding layer;
• and
• a bonding pad in the second bonding layer and electrically connected to one of the plurality of metal pads;
• and
• a second semiconductor die bonded to the first semiconductor die with a dielectric-to-dielectric bond and a metal-to-metal bond.

A method comprising:

• forming a plurality of metal pads over a semiconductor substrate;
• depositing a first portion of a passivation layer over and between adjacent ones of the plurality of metal pads;
• and
• performing a thinning process on the first portion of the passivation layer;
• after performing the thinning process, depositing a second portion of the passivation layer over the first portion of the passivation layer;
• and
• depositing a first bonding layer over the second portion of the passivation layer.