Methods for forming semiconductor devices with stepped bond pads
A method for forming a semiconductor structure includes forming a bond pad over a last metal layer of the semiconductor structure wherein the bond pad includes a wire bond region; and recessing the wire bond region such that the wire bond region has a first thickness and a region of the bond pad outside the wire bond region has a second thickness that is greater than the first thickness.
1. A method for forming a semiconductor structure, the method comprising:
forming a bond pad over a last metal layer of the semiconductor structure, wherein the bond pad is connected to a portion of the last metal layer, and the bond pad includes a wire bond region and a probe region; and
recessing the wire bond region such that the entire wire bond region has a first thickness and the entire probe region of the bond pad has a second thickness that is greater than the first thickness, wherein the first thickness is selected so that almost all of the bond pad in the wire bond region becomes part of an intermetallic compound during wire bonding; and
forming a wire bond in the wire bond region, wherein the probe region is outside the wire bond and the wire bond region and is not covered by a passivation layer.
2. The method of claim 1 , wherein the recessing the wire bond region is performed such that the first thickness is at most 60% of the second thickness.
3. The method of claim 1 , further comprising:
forming the passivation layer over the bond pad and last metal layer; and
forming an opening in the passivation layer to expose the wire bond region.
4. The method of claim 3 , wherein the recessing the wire bond region comprises performing an etch of the wire bond region using the passivation layer as a masking layer.
5. The method of claim 3 , further comprising:
forming a patterned masking layer over the passivation layer, wherein the patterned masking layer defines a location of the opening, and wherein the forming the opening in the passivation layer is performed using the patterned masking layer.
6. The method of claim 5 , wherein the recessing the wire bond region comprises performing an etch of the wire bond region using the patterned masking layer.
7. The method of claim 3 , further comprising:
forming a patterned masking layer over the passivation layer having a second opening which exposes the wire bond region, wherein the recessing the wire bond region comprises performing an etch of the wire bond region using the patterned masking layer.
8. The method of claim 1 , further comprising:
forming a second conductive layer over the bond pad.
9. The method of claim 1 , wherein the bond pad is further characterized as an aluminum bond pad.
10. The method of claim 1 , further comprising:
attaching a copper wire bond to the wire bond region.
11. The method of claim 1 , wherein the semiconductor structure further comprises conductive routing portions over the last metal layer, wherein the conductive routing portions have the second thickness.
12. The method of claim 11 , further comprising:
forming the passivation layer over the bond pad and last metal layer; and
forming an opening in the passivation layer to expose the wire bond region such that the passivation layer remains over the conductive routing portions.
13. A method for forming a semiconductor structure, the method comprising:
forming a bond pad over a last metal layer of the semiconductor structure, wherein the bond pad is connected to a portion of the last metal layer, and the bond pad includes a wire bond region and a probe region outside the wire bond region;
determining a first thickness of the bond pad over the wire bond region so that a majority of the bond pad in the wire bond region is consumed in an intermetallic compound during wire bonding;
recessing the wire bond region such that the entire wire bond region has the first thickness, and the entire probe region a second thickness that is greater than the first thickness; and
forming a wire bond in the wire bond region, wherein the probe region is accessible by a test probe after the wire bond is formed.
14. The method of claim 13 , wherein the recessing the wire bond region is performed such that the first thickness is between 30 and 60% of the second thickness.
15. The method of claim 13 , further comprising:
forming a passivation layer over the bond pad and last metal layer; and
forming an opening in the passivation layer to expose the wire bond region and the probe region.
16. The method of claim 15 , further comprising:
forming a first patterned masking layer over the passivation layer, wherein the first patterned masking layer defines a location of the opening, and wherein the forming the opening in the passivation layer is performed using the first patterned masking layer.
17. The method of claim 16 , further comprising:
forming a second patterned masking layer over the passivation layer having a second opening which exposes the wire bond region and does not expose the probe region, wherein the recessing the wire bond region comprises performing an etch of the wire bond region using the second patterned masking layer while the second patterned masking layer protects the probe region.
18. The method of claim 13 , wherein the bond pad is further characterized as an aluminum bond pad, and a wire bond of the wire bonding is further characterized as copper wire.
19. The method of claim 13 , wherein the semiconductor structure further comprises conductive routing portions over the last metal layer, wherein the conductive routing portions have the second thickness.