Fine pitch microcontacts and method for forming thereof
A method includes applying a final etch-resistant material to an in-process substrate so that the final etch-resistant material at least partially covers first microcontact portions integral with the substrate and projecting upwardly from a surface of the substrate, and etching the surface of the substrate so as to leave second microcontact portions below the first microcontact portions and integral therewith, the final etch-resistant material at least partially protecting the first microcontact portions from etching during the further etching step. A microelectronic unit includes a substrate, and a plurality of microcontacts projecting in a vertical direction from the substrate, each microcontact including a base region adjacent the substrate and a tip region remote from the substrate, each microcontact having a horizontal dimension which is a first function of vertical location in the base region and which is a second function of vertical location in the tip region.
1. A method of forming an element having microcontacts, comprising:
(a) providing a first etch-resistant material at selected locations on a top surface of a substrate, a first metal being exposed at the top surface, wherein the substrate includes a first metal layer including the first metal, a second metal layer exposed at a bottom surface of the substrate, and a third metal layer between the first and second metal layers, the third metal layer including a metal different from a metal of the first and second metal layers;
(b) etching the first metal at the top surface of the substrate by applying processing to the substrate from a location above the top surface at locations not covered by the first etch-resistant material and thereby forming first microcontact portions projecting upwardly at the selected locations;
(c) providing a second etch-resistant material on the first microcontact portions;
(d) further etching the first metal of the substrate to form second microcontact portions below the first microcontact portions, the second etch-resistant material at least partially protecting the first microcontact portions from etching during the further etching step, thereby patterning the first metal layer selectively with respect to the third metal layer;
(e) patterning the second metal layer by applying processing to the substrate from a location below the bottom surface of the substrate to form the second metal layer into electrically conductive traces extending in lateral directions defining a plane; and
(f) removing portions of the third metal layer to leave the microcontacts and the traces, such that the second microcontact portions extend away from the traces in a vertical direction transverse to the plane,
wherein the microcontacts are configured to be bonded by at least one of solder, eutectic, or diffusion bonding to corresponding contacts on a face of a microelectronic element, the microcontacts are arranged in an array having a plurality of rows of microcontacts and a plurality of columns of microcontacts, and each microcontact is generally in the form of a body of revolution about a central axis.
2. The method of claim 1 , wherein the step of etching the top surface is performed so that the first etch-resistant material projects laterally from the first microcontact portions.
3. The method of claim 1 , wherein the step of providing the second etch-resistant material includes depositing the second etch-resistant material and exposing the deposited material to radiation.
4. The method of claim 3 , wherein during the step of exposing the deposited material to radiation, the laterally projecting first etch-resistant material protects portions of the deposited second etch-resistant material from radiation.
5. The method of claim 1 , further comprising removing the first and second etch-resistant materials.
6. The method of claim 1 , wherein the step of providing the first etch-resistant material at selected locations comprises depositing the first etch-resistant material over the top surface of the substrate and the step of exposure includes placing a mask on the first etch-resistant material.
7. The method of claim 6 , wherein the first etch-resistant material and the mask are exposed to radiation.
8. A method of forming an element having microcontacts, comprising:
(a) providing a first etch-resistant material at selected locations on a top surface of a substrate, a first metal being exposed at the top surface;
(b) etching the first metal at the top surface of the substrate at locations not covered by the first etch-resistant material and thereby form first microcontact portions projecting upwardly at the selected locations;
(c) providing a second etch-resistant material on the first microcontact portions;
(d) further etching the first metal of the substrate to form second microcontact portions below the first microcontact portions, the second etch-resistant material at least partially protecting the first microcontact portions from etching during the further etching step; and
(e) providing a third etch-resistant material on the second microcontact portions;
(f) further etching the first metal of the substrate to form third microcontact portions below the second microcontact portions, the third etch-resistant material at least partially protecting the first and second microcontact portions from further etching; and
(g) patterning the substrate to form electrically conductive traces extending in lateral directions defining a plane,
wherein the third microcontact portions extend away from the traces in a vertical direction transverse to the plane, and
wherein the microcontacts are configured to be bonded by at least one of solder, eutectic, or diffusion bonding to corresponding contacts on a face of a microelectronic element, the microcontacts are arranged in an array having a plurality of rows of microcontacts and a plurality of columns of microcontacts, and each microcontact is generally in the form of a body of revolution about a central axis.
9. The method of claim 1 , wherein the first and second etch-resistant materials are gold.
10. The method of claim 1 , wherein the first and second etch-resistant materials are a photoresist.
11. A method of forming an element having microcontacts, comprising:
(a) applying a final etch-resistant material to an in-process substrate so that the final etch-resistant material at least partially covers first microcontact portions integral with the substrate and projecting upwardly from a surface of the substrate, wherein the substrate includes a first metal layer including a first metal exposed at the surface of the substrate, a second metal layer exposed at a bottom surface of the substrate, and a third metal layer between the first and second metal layers, the third metal layer including a metal different from a metal of the first and second metal layers;
(b) etching the first metal at the surface of the substrate by applying processing to the substrate from a location above the surface so as to leave second microcontact portions below the first microcontact portions and integral therewith, the final etch-resistant material at least partially protecting the first microcontact portions from etching during the etching step, thereby patterning the first metal layer selectively with respect to the third metal layer;
(c) patterning the second metal layer by applying processing to the substrate from a location below the bottom surface of the substrate to form the second metal layer into electrically conductive traces extending in lateral directions defining a plane; and
(d) removing portions of the third metal layer to leave the microcontacts and the traces, such that the second microcontact portions extend away from the traces in a vertical direction transverse to the plane,
wherein the microcontacts are configured to be bonded by at least one of solder, eutectic, or diffusion bonding to corresponding contacts on a face of a microelectronic element, the microcontacts are arranged in an array having a plurality of rows of microcontacts and a plurality of columns of microcontacts, and each microcontact is generally in the form of a body of revolution about a central axis.
12. The method of claim 11 , further comprising forming the in-process substrate by
(e) providing a preliminary etch-resistant material at selected locations on a top surface of the substrate; and
(f) etching the top surface of the substrate so as to remove portions of the substrate not covered by the preliminary etch-resistant material and thereby leave the first microcontact portions projecting upwardly from the etched surface.
13. The method of claim 12 , wherein the step of providing the preliminary etch-resistant material at selected locations includes providing the preliminary etch-resistant material over the top surface entirely and supplying a mask atop the preliminary etch-resistant material to expose the preliminary etch-resistant material to radiation.
14. The method of claim 11 , wherein the first microcontact portions have vertically-extensive side walls and the final etch-resistant material at least partially covers the side walls of the first microcontact portions.
15. The method of claim 12 , further comprising removing the preliminary and the final etch-resistant materials.
16. The method of claim 1 , wherein step (e) is performed after step (d).
17. The method of claim 1 , further comprising:
(g) forming a dielectric layer, wherein said traces contact at least portions of said dielectric layer.
18. The method of claim 11 , wherein step (c) is performed after step (b).
19. The method of claim 12 , further comprising:
(g) forming a dielectric layer, wherein said traces contact at least portions of said dielectric layer.
20. The method of claim 1 , wherein the microcontacts are formed with heights and diameters configured to permit sufficient bending and tilting of the microcontacts to accommodate differential thermal expansion and contraction of a microelectronic element relative to the element when the microcontacts are bonded to corresponding contacts of the microelectronic element.
21. The method of claim 1 , wherein a minimum pitch between the microcontacts in at least one direction parallel to the top surface of the substrate is less than a sum of a diameter of one of the microcontacts and a height of one of the microcontacts.
22. The method of claim 11 , wherein the microcontacts are formed with heights and diameters configured to permit sufficient bending and tilting of the microcontacts to accommodate differential thermal expansion and contraction of a microelectronic element relative to the element when the microcontacts are bonded to corresponding contacts of the microelectronic element.
23. The method of claim 11 , wherein a minimum pitch between the microcontacts in at least one direction parallel to the surface of the substrate is less than a sum of a diameter of one of the microcontacts and a height of one of the microcontacts.
24. The method of claim 1 , wherein each microcontact defines a minimum width, and the minimum width of each microcontact is located in the second microcontact portion adjacent the substrate.
25. The method of claim 11 , wherein each microcontact defines a minimum width, and the minimum width of each microcontact is located in the second microcontact portion adjacent the substrate.