Chip scale surface mounted device and process of manufacture
View Patent ↗A chip scale package has a semiconductor MOSFET die which has a top electrode surface covered with a layer of a photosensitive liquid epoxy which is photolithographically patterned to expose portions of the electrode surface and to act as a passivation layer and as a solder mask. A solderable contact layer is then formed over the passivation layer. The individual die are mounted drain side down in a metal clip or can with the drain electrode disposed coplanar with a flange extending from the can bottom.
1. A method of preparing a semiconductor die comprising:
forming a plurality of die in a semiconductor wafer, each die having at least one electrode on a major surface thereof;
covering said at least one electrode of said die in said semiconductor wafer with a mask material;
opening at least one opening in said mask material over each electrode, each said opening reaching said electrode at its bottom;
forming at least one metal layer over said electrode at said bottom of each said opening; and
singulating each die from said wafer.
2. A method according to claim 1 , wherein said die are power semiconductor devices.
3. A method according to claim 1 , wherein said die are power MOSFETs.
4. A method according to claim 3 , wherein said at least one electrode is a source electrode.
5. A method according to claim 1 , further comprising a second electrode on said major surface of each said die.
6. A method according to claim 5 , wherein said second electrode is a gate electrode.
7. A method according to claim 1 , wherein said mask material is a photoimagable solder mask.
8. A method according to claim 1 , wherein said mask material is an epoxy.
9. A method according to claim 8 , wherein said epoxy is photosensitive.
10. A method according to claim 1 , wherein said mask material is capable of serving as a plating resist.
11. A method according to claim 1 , wherein said mask material is capable of serving as a passivation.
12. A method according to claim 1 , wherein said mask material is comprised of silicon nitride.
13. A method according to claim 1 , wherein said opening step is carried out by a reticule.
14. A method according to claim 1 , wherein said opening step is carried out with a laser etch.
15. A method according to claim 1 , wherein said at least one metal layer is formed by plating.
16. A method according to claim 15 , wherein said at least one metal layer is comprised of nickel.
17. A method according to claim 1 , further comprising forming a second metal layer atop said one metal layer.
18. A method according to claim 17 , wherein said second metal layer is comprised of gold.
19. A method according to claim 17 , wherein said second metal layer is comprised of tin.
20. A method according to claim 17 , wherein said second metal layer is comprised of copper.
21. A method according to claim 17 , further comprising forming a third metal layer atop said second metal layer.
22. A method according to claim 21 , wherein said third metal layer is comprised of silver.
23. A method according to claim 22 , wherein said third metal layer is plated.
24. A method according to claim 17 , wherein said second metal layer is plated.