Fine pitch microelectronic contact array and method of making same
View Patent ↗Provided are microfabricated probe elements, including elastomer elements, and methods of making the same, that can be readily used with fine pitch microelectronic arrays, for instance by providing sufficient compliance in a small package, while minimizing deflection forces, and while precisely maintaining the planarity and positioning of the contact tips across vast grid arrays. Elastomer elements may be generated using photolithography, either directly or through a sacrificial lost-mold process. Elastomer probe elements are provided with rigid tip structures microfabricated thereon to improve contact pressure. A novel space transformation probe card assembly is also provided.
1. A process of manufacturing an array of elastomer probes on a surface comprising the steps of:
depositing a thin electrically conductive metal layer on the surface;
forming a metal base for the probe upon the thin electrically conductive metal layer;
forming a sacrificial structure in the likeness of the probe upon the thin electrically conductive metal layer;
electrodepositing a sacrificial metal upon the thin electrically conductive metal layer and thereby enveloping the sacrificial structure in the sacrificial metal;
planarizing the sacrificial metal and thereby exposing a top surface of the sacrificial structure;
removing the sacrificial structure, thereby leaving a void in the sacrificial metal at the location of the sacrificial structure;
forming elastomeric probe material into the void in the sacrificial metal;
depositing a second metal layer upon the elastomeric probe material and the sacrificial metal;
forming a metal pad upon the second metal layer using photolithography or electroforming;
forming a metal contact tip structure upon the metal pad using photolithography or electroforming;
electrodepositing a second sacrificial metal upon the second metal layer and thereby enveloping the metal pad and metal contact tip in the second sacrificial metal;
planarizing the second sacrificial metal and thereby exposing a top surface of the metal contact tip; and
removing at least part of: the second sacrificial metal, the second metal layer, the first sacrificial metal, and the thin electrically conductive metal layer.
2. The process of claim 1 , wherein the surface is selected from a group consisting of:
multi layer organic, thin film redistribution layer, ceramic, and combinations thereof.
3. The process of claim 1 , further comprising the step of removing at least a portion of the thin electrically conductive metal layer.
4. The process of claim 1 , wherein the step of depositing a thin electrically conductive metal layer on the surface comprises sputtering or vapor depositing.
5. The process of claim 1 , wherein the thin electrically conductive metal layer deposited on the surface comprises Ti, Cr, Au or Cu.
6. The process of claim 1 , wherein the step of forming a metal base for the probe upon the thin electrically conductive metal layer comprises forming a pattern in a negative photoresist such that the thin electrically conductive metal layer is exposed and the metal base is formed through electrodeposition in the pattern.
7. The process of claim 1 , wherein the step of forming a sacrificial structure in the likeness of the probe upon the thin electrically conductive metal layer comprises using photolithography to form a structure out of photoresist material.
8. The process of claim 1 , wherein the step of planarizing the sacrificial metal comprises any of the steps of lapping, polishing, chemical-mechanical polishing, or diamond turning.
9. The process of claim 1 , wherein the step of removing the sacrificial structures comprises either solvent dissolution or vapor-phase etching.
10. The process of claim 1 , wherein the step of forming elastomeric probe material into the voids in the sacrificial metal comprises casting a thermosetting silicone elastomer.
11. The process of claim 1 , wherein the step of forming elastomeric probe material into the voids in the sacrificial metal comprises casting polydimethylsiloxane (PDMS).
12. The process of claim 1 , wherein the probe material is electrically conductive.
13. The process of claim 1 , wherein the step of forming elastomeric probe material into the voids in the sacrificial metal further comprises planarizing the elastomeric probe material in the sacrificial metal.
14. The process of claim 1 , wherein the step of forming a metal pad upon the second metal layer comprises performing the Guckel process.
15. The process of claim 1 , wherein the step of forming a metal contact tip structure upon the metal pad comprises forming the metal contact tip structure out of hard, corrosion-resistant metal.
16. The process of claim 1 , wherein the step of forming a metal contact tip structure upon the metal pad comprises forming the metal contact tip structure out of material comprising Rhodium.
17. The process of claim 1 , wherein the step of removing at least part of: the second sacrificial metal, the second metal layer, the first sacrificial metal, and the thin electrically conductive metal layer, comprises wet or dry etching.
18. The process of claim 1 , further comprising the step of embedding metal in the elastomeric probe material.
19. The process of claim 1 , further comprising the step of embedding a wirebond in the elastomeric probe material.
20. The process of claim 1 , further comprising the step of at least partially encasing the elastomeric probe material in an outer rigid shell.
21. The process of claim 20 , further comprising the step of forming the outer rigid shell from a conductive metal.
22. The process of claim 20 , further comprising the step of microfabricating the outer rigid shell directly in place using photolithography or electroforming.
23. A probe array for a microelectronic contactor assembly, the probe array comprising:
a plurality of adjacent probes, each probe comprising:
an electrically conductive reinforcing column adjacent to a compliant and resilient elastomeric column, the electrically conductive reinforcing column having a first top surface and the resilient elastomeric column having a second top surface;
an electrically conductive column cap formed on the first top surface, the electrically conductive column cap electrically connected with an electrically conductive cantilever member that extends away from the first top surface and toward the second top surface where the electrically conductive cantilever member is electrically connected with an electrically conductive contact tip portion that is formed on the second top surface.
24. The probe array of claim 23 , wherein the plurality of adjacent probes are separated from each other by air gaps.
25. The probe array of claim 23 , wherein the probe array has a pitch equal to or less than 300 μm.
26. The probe array of claim 23 , wherein the probe array has a pitch equal to or less than 50 μm.
27. The probe array of claim 23 , wherein the electrically conductive column cap, the electrically conductive cantilever member, and the electrically conductive contact tip portion of a probe are all formed from a single piece of metal.
28. The probe array of claim 23 , wherein the electrically conductive reinforcing column of a probe comprises a metal post.