Copper pillar sidewall protection
View Patent ↗Methods for copper pillar protection may include forming a metal post over a contact on a semiconductor die, where the metal post comprises a sidewall. A metal cap may be formed on the metal post and may be wider than the width of the metal post. A solder bump may be formed on the metal cap, and a conformal passivation layer may be formed on at least the sidewall of the metal post. The metal cap may be rounded shaped or rectangular shaped in cross-section. The metal post and the metal cap may comprise copper. The metal cap may comprise a copper layer and a nickel layer. The seed metal layer may comprise one or more of titanium, tungsten, and copper. The conformal passivation layer may comprise a nonwettable polymer. Horizontal portions of the conformal passivation layer may be removed utilizing an anisotropic etch such as a plasma etch.
1. A method for semiconductor packaging, the method comprising:
forming a seed metal layer over a contact on a semiconductor die;
forming a metal post on the seed metal layer over the contact on the semiconductor die, the metal post comprising a sidewall;
forming a metal cap on the metal post;
forming a solder bump on the metal cap;
removing the seed metal layer from a portion of the contact extending beyond the metal post; and
after said removing, forming a conformal dielectric layer of a polymer material on at least the sidewall of the metal post, a lower surface of the metal cap, and the contact.
2. The method according to claim 1 , wherein the metal cap comprises two metal layers.
3. The method according to claim 2 , wherein the metal cap comprises a copper layer and a nickel layer.
4. The method according to claim 1 , wherein the metal cap comprises a rounded shaped cross-section.
5. The method according to claim 1 , wherein the metal cap comprises a rectangular shaped cross-section.
6. The method according to claim 1 , wherein the metal cap is wider than the width of the metal post.
7. The method according to claim 1 , wherein the metal post and the metal cap comprise copper.
8. The method according to claim 1 , wherein said seed metal layer comprises one or more of titanium, tungsten, and copper.
9. The method according to claim 1 , wherein the conformal dielectric layer comprises a nonwettable polymer.
10. The method according to claim 1 , comprising forming the conformal dielectric layer utilizing organic solderability preservatives.
11. The method according to claim 1 , comprising removing horizontal portions of the conformal dielectric layer utilizing an anisotropic etch.
12. The method according to claim 11 , wherein the anisotropic etch comprises a plasma etch.
13. A method for semiconductor packaging, the method comprising:
forming a pillar connection with a dielectric ring by, at least:
forming a photoresist layer on a substrate;
forming an opening in the photoresist layer over a portion of a metal contact on the substrate;
forming a metal post in the opening on the metal contact;
forming a conformal dielectric layer on the photoresist layer and the metal post;
removing portions of the conformal dielectric layer so that only a ring of the dielectric layer remains at an interface between the photoresist and the metal post;
forming a solder bump on the metal post such that the solder bump fills an interior of the ring and contacts an upper surface of the metal post, a lower surface of the ring rests upon an upper surface of the metal post, and a lower surface of the solder bump rests upon an upper surface of the ring; and
removing the photoresist.
14. An electronic device comprising:
a passivated sidewall pillar connection comprising:
a metal post formed over a contact on a semiconductor die, the metal post comprising a sidewall;
a solder bump on the metal post; and
a conformal dielectric layer in a ring shape;
wherein the solder bump fills an interior of the ringed-shaped, conformal dielectric layer and contacts an upper surface of the metal post;
wherein a lower surface of the ringed-shaped, conformal dielectric layer rests upon an upper surface of the metal post; and
wherein a lower surface of the solder bump rests upon an upper surface of the ringed-shaped, conformal dielectric layer.
15. The electronic device according to claim 14 , wherein a metal cap is formed on the metal post before the solder bump is formed.