Integrated circuit package including wire bonds
View Patent ↗It has been found that integrated packages having dies with at least 10 bonding pads separated by a pitch of 65 μm or less are susceptible to corrosion upon wire bonding to these pads and subsequent encapsulation in a passivating material. In particular, crevices are potentially formed between the bonding wire and bonding pad that are not passivated and that promote corrosion. Avoidance of crevice formation through, for example, appropriately choosing the bonding pad and wire configuration substantially avoids such corrosion.
1. A process for fabricating an integrated circuit package, said package comprising:
1) an integrated circuit die including a bonding pad array,
2) a substrate comprising electrical contact pads, and
3) electrical communication structures with pitch of 65 μm or less, said structures comprising an electrically conducting wire compression bonded to a bonding pad of said array and bonded to at least one of said contact pads; said process comprising:
contacting said wire to said bonding pad,
then applying a force such that said wire is compression bonded to said bonding pad, and
then covering said die with a passivating material wherein:
said bonding pad comprises aluminum deposited at least partially over a passivation structure,
said bonding pad is surrounded by a partially overlaying passivation region, and
the configuration of said bonding pad before applying said force is such that, after applying said force, crevice formation between said bonding pad and said wire is substantially avoided.
2. The process of claim 1 wherein the thickness of said pads in less than 1.5 μm.
3. The process of claim 1 wherein said bonding pad has before application of said force voids underlying said wire into which said bonding pad distorts upon application of said force.
4. The process of claim 1 wherein said passivating material comprises a silicon oxide or silicon nitride.
5. The process of claim 1 wherein said passivating material includes bromine entities.
6. The process of claim 5 wherein said passivating material comprises an epoxy polymer.
7. The process of claim 1 wherein said force is in the range 2 to 20 grams.
8. The process of claim 1 wherein said pitch is 60 μm or less.
9. The process of claim 8 wherein said pitch is 55 μm or less.
10. The process of claim 1 wherein said force is applied using a capillary tube through which said wire passes.
11. A method for fabricating a bond pad on an integrated circuit, the method comprising:
providing a semiconductor substrate;
forming a first passivation layer on the substrate, the first passivation layer having a bond-pad opening having a first width and a passivation structure located within the bond-pad opening such that the passivation structure has a second width smaller than the first width;
overlaying the bond-pad opening, including the passivation structure, with a metal layer such that the top of the metal layer substantially follows the contours of the underlying bond-pad opening so as to form a depression in the metal layer;
forming a second passivation layer on the substrate, the second passivation layer having a passivation region surrounding and partially overlaying the metal layer; and
then bonding a wire terminated with a wire ball to the metal layer of the bond pad by placing the wire ball over the passivation structure and applying a force such that the wire is compression bonded to the metal layer of the bond pad, wherein the metal layer over the passivation structure distorts into the depression.
12. The method of claim 11 , wherein the metal layer comprises at least 95% aluminum.
13. The method of claim 11 , wherein the metal layer over the passivation structure distorts laterally into the depression.
14. The method of claim 11 , wherein the wire ball is bonded directly to the metal layer.
15. The method of claim 11 , further comprising, following the bonding step, encapsulating the integrated circuit in a molding compound.