Metal reduction in wafer scribe area
View Patent ↗A process for removing metal from a scribe area of a semiconductor wafer. The metal removed may include exposed metal in a saw path of the scribe area and the metal in a crack stop trench of the scribe area. In one example, copper is removed from the scribe area by wet etching the wafer. In one example, the wet etching process is performed after the removal of an exposed barrier adhesion layer on the wafer surface. Removal of the metal in the saw path may reduce the amount of metal buildup on a saw blade during singulation of the die areas of a wafer.
1. A method of forming semiconductor die comprising:
providing a wafer, the wafer comprising a substrate and a stack layer comprising a plurality of layers with interconnecting metal overlying the substrate, the stack layer comprising exposed metal at a portion of a surface of a saw path within a scribe area separating u plurality of die, some of the exposed metal extending into the plurality of layers;
forming a dielectric passivation layer selectively overlying the stack layer; and
removing exposed metal at least to a first depth in a saw path of the scribe area to form recessed regions in the saw path.
2. The method of claim 1 further comprising:
forming a continuous conductive barrier layer overlying the wafer;
forming a continuous metal layer overlying the continuous conductive barrier layer;
patterning photo resist over the wafer to expose areas where external contact is desired;
forming a contact stud in the areas where external contact is desired;
forming solder overlying the contact stud in the areas where external contact is desired;
removing the photo resist;
removing the continuous metal layer in all areas where there is no contact stud; and
removing the continuous conductive barrier layer in all areas where there is no contact stud.
3. The method of claim 2 further comprising:
while removing exposed metal in the saw path, also decreasing a circumference of the contact stud and leaving an exposed portion of the continuous conductive barrier layer adjacent the contact stud.
4. The method of claim 2 further comprising:
forming a polyimide layer overlying the dielectric passivation layer to define areas where external contact is desired, wherein the contact stud is bounded by the polyimide layer and the polyimide layer provides stress relief.
5. The method of claim 2 further comprising:
selecting at least one of TiW, TiN, Ta, Ni, or W as the continuous conductive barrier layer.
6. The method of claim 2 further comprising:
forming the contact stud as a copper stud in a ball grid array (BGA) package.
7. The method of claim 2 wherein the metal of the continuous metal layer has a higher conductivity than a barrier material of the continuous conductive barrier layer.
8. The method of claim 1 wherein removing exposed metal in the saw path of the scribe area further comprises:
removing all exposed metal in the saw path.
9. The method of claim 1 further comprising:
sawing the wafer using a single saw blade to separate multiple die or the wafer by cutting the wafer in the saw path.
10. The method of claim 1 wherein the removing exposed metal in the saw path further comprises:
forming open trenches in the scribe area.
11. The method of claim 1 wherein the first depth is less than a total depth of exposed metal.
12. The method of claim 1 further comprising:
forming a contact stud overlying a predetermined portion of a conductive area of the wafer, the contact stud being formed prior to the removing exposed metal in the saw path so that some cross sectional width of the contact stud is reduced from the removing exposed metal in the saw path.
13. The method of claim 1 wherein the stack layer includes a top layer, wherein the removing exposed metal at least to a first depth includes removing exposed metal in the top layer in the saw path of the scribe area.
14. The method of claim 1 wherein:
the stack layer includes a top layer, a via layer located below the top layer, and another layer located below the via layer;
the another layer includes a metal structure in the saw path and electrically coupled to a metal structure of the exposed metal in the top layer in the saw path by a metal via in the via layer,
the removing exposed metal at least to a first depth includes removing the metal structure of the exposed metal, the metal via, and the metal structure or the another layer.
15. A method of forming a semiconductor die comprising:
providing a substrate on a wafer having multiple die areas that are physically separated by a plurality of scribe areas each having a saw path;
forming a stack layer overlying the substrate and having dielectric material and interconnecting metal, the stack layer including exposed metal at a portion of a surface of a saw path of a scribe area of the plurality;
processing the saw path within the scribe area by etching the exposed metal to at least a first depth to form a recessed region in the saw path.
16. The method of claim 15 wherein the stack layer includes a top layer, wherein the etching the exposed metal at least to a first depth includes removing exposed metal in the top layer in the saw path of the scribe area.
17. The method of claim 15 wherein:
the stack layer includes a top stack layer, a via stack layer located below the top stack layer, and another stack layer located below the via stack layer;
the another layer includes a metal structure in the saw path electrically coupled to a metal structure of the exposed metal in the top stack layer in the saw path by a metal via in the via stack layer;
the etching the exposed metal at least to a first depth includes removing the metal structure of the exposed metal, the metal via, and the metal structure of the another layer.
18. The method of claim 15 wherein:
the stack layer includes a top layer, a via layer located below the top layer, and another layer located below the via layer;
the another layer includes a metal structure located in the saw path and electrically coupled to a metal structure of the exposed metal in the top layer by at least a metal via in the via layer;
the etching the exposed metal at least to a first depth includes removing the metal structure of the exposed metal but not the metal structure of the another layer.
19. The method of claim 15 further comprising:
forming a contact stud on at least one of the multiple die areas prior to etching exposed metal within the saw path.
20. The method of claim 15 further comprising:
forming a continuous conductive barrier layer overlying the wafer;
forming a continuous metal layer overlying the continuous conductive barrier layer;
patterning photo resist over the wafer to expose areas where external contact is desired;
forming a contact stud in the areas where external contact is desired, the contact stud;
forming solder overlying the contact stud in the areas where external contact is desired;
removing the photo resist;
removing the continuous metal layer in all areas where there is no contact stud; and
removing the continuous conductive barrier layer in all areas where there is no contact stud.
21. The method of claim 15 wherein the exposed metal comprises copper.
22. The method of claim 15 further comprising etching exposed metal in a crack stop trench in the scribe area.
23. The method of claim 1 wherein the removing exposed metal at least to a first depth in a saw path of the scribe area to form recessed regions in the saw path further includes removing metal of a via layer of the stack layer in the saw path.
24. The method of claim 15 wherein the processing the saw path within the scribe area further includes etching metal of a via layer of the stack layer in the saw path.