Semiconductor seal ring and method of manufacture thereof
View Patent ↗An improved semiconductor seal ring and method therefore is described. The seal ring comprises a thick layer wherein at least a portion of the thick layer is removed from a singulation street prior to singulation, thereby avoiding damage to the thick layer during the singulation process. A thin moisture-proof barrier layer is preferably deposited over at least a portion of the thick layer to seal at least an edge of the thick layer. A thick nonmetallic layer preferably used for fabrication of active circuit elements may advantageously be employed as the thick layer (for example, an aluminum nitride (AlN) layer in, for example, a bulk acoustic wave (BAW) filter device). A thin amorphous nonmetallic layer (e.g., a silicon nitride (SiN) layer) may preferably be deposited over the thick layer. Alternatively, other materials may be used.
1. A method comprising:
depositing a thick layer of a first nonmetallic material over a semiconductor wafer, the first nonmetallic material comprising a brittle material;
depositing a thin layer of a second nonmetallic material over the thick layer, the second nonmetallic layer comprising an amorphous moisture-barrier material;
selectively removing a second portion of the thick layer to define a singulation street between a first die of the wafer and a second die of the wafer while leaving a first portion of the thick layer over the first die; and
cutting the wafer along the singulation street to separate the first die from the second die, wherein the cutting the wafer along the singulation street includes retaining a first portion of the thin layer between the first portion of the thick layer and a kerf defined by the cutting the wafer, wherein the first portion of the thin layer encapsulates the first portion of the thick layer.
2. The method of claim 1 , wherein depositing the thin layer of the second non-metallic material includes depositing the thin layer in contact with the thick layer.
3. The method of claim 1 , wherein the brittle material comprises aluminum nitride; and
wherein the amorphous moisture-barrier material comprises silicon nitride.
4. The method of claim 1 , further comprising:
forming circuitry on the first die; and
wherein depositing the thick layer includes depositing the thick layer with the first portion of the thick layer extending contiguously near a perimeter of the first die and surrounding the circuitry of the first die.
5. The method of claim 1 , wherein depositing the thick layer includes depositing the thick layer with a thickness of at least 500 nanometers.
6. The method of claim 1 , wherein selectively removing the second portion of the thick layer includes etching the thick layer to define tapered edges of the singulation street.