Oxygen-Free Protection Layer Formation in Wafer Bonding Process

A method comprising:

• bonding a device wafer over a carrier wafer;
• thinning a semiconductor substrate of the device wafer;
• trimming the device wafer, wherein an edge portion of the device wafer is trimmed;
• depositing a protection layer on the device wafer and the carrier wafer, wherein the depositing the protection layer comprises:
• depositing a first sub layer comprising a first material;
• and
• depositing a second sub layer comprising a second material different from the first material;
• revealing a top surface of the device wafer;
• and
• forming an interconnect structure over the device wafer, wherein the interconnect structure is electrically connected to integrated circuit devices in the device wafer.

A method comprising:

• bonding a device wafer over a carrier wafer, wherein a first dielectric layer in the device wafer is bonded to a second dielectric layer in the carrier wafer;
• trimming the device wafer, wherein a portion of a first semiconductor substrate in the device wafer is trimmed, and a top surface of a second substrate in the carrier wafer is exposed;
• depositing a protection layer on the device wafer and the carrier wafer, wherein the depositing the protection layer is performed using process gases free from oxygen therein;
• removing horizontal portions of the protection layer from the device wafer and the carrier wafer;
• and
• removing the second substrate.