Method for thinning a bonding wafer

A method for thinning at least one silicon bonding wafer, the method comprising:

• providing a silicon bonding wafer coupled to a handling wafer by a low-k bonding layer, wherein the silicon bonding wafer contains metal filled vias extending through at least a portion of a thickness of the silicon bonding wafer;
• performing a wafer edge trimming process that forms a trimmed silicon bonding wafer, wherein the wafer edge trimming process removes an edge portion of the silicon bonding wafer and exposes an upper surface of the handling wafer;
• forming a protective mask by a spin-on process on the trimmed silicon bonding wafer and on the exposed upper surface of the handling wafer, wherein the protective mask comprises an oxide film, a nitride film, or an oxynitride film;
• planarizing the protective mask and the trimmed silicon bonding wafer, wherein the protective mask is removed from the trimmed silicon bonding wafer;
• performing a first wet etching process that selectively removes a portion of the planarized trimmed silicon bonding wafer relative to the protective mask;
• and
• after the first wet etching process, performing a second wet etching process that selectively removes the planarized protective mask.

A method for thinning at least one silicon wafer, the method comprising:

• providing a silicon bonding wafer coupled to a handling wafer by a low-k bonding layer, wherein the silicon bonding wafer contains metal filled vias extending through at least a portion of a thickness of the silicon bonding wafer, and wherein the metal filled vias are in direct contact with the bonding layer;
• performing a wafer edge trimming process that forms a trimmed silicon bonding wafer, wherein the wafer edge trimming process removes an edge portion of the silicon bonding wafer and exposes at least one upper surface of the handling wafer;
• forming a protective mask by a spin-on process on the trimmed silicon bonding wafer and on the exposed upper surface of the handling wafer, wherein the protective mask comprises a SiO2 film;
• planarizing the protective mask and the handling wafer, wherein the protective mask is removed from an upper surface of the trimmed silicon bonding wafer;
• performing a first wet etching process that selectively removes a portion of the planarized trimmed silicon bonding wafer relative to the protective mask, wherein the first wet etching process comprises exposing the planarizing protective mask and the planarized trimmed silicon bonding wafer to a liquid bath containing TMAH (tetramethyl ammonium hydroxide), HNA (aqueous solution containing hydrogen fluoride, nitric acid, and acetic acid), or KOH (potassium hydroxide), and
• after the first wet etching process, performing a second wet etching process that selectively removes the planarized protective mask, wherein the second wet etching process comprises exposing the planarized protective mask to liquid bath containing an organic solvent, or an aqueous solution, wherein the aqueous solution includes an aqueous solution of hydrogen fluoride.