Fine pitch microcontacts and method for forming thereof

Abstract

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 microelectronic unit comprising:
 (a) a substrate; and   (b) 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.   
     
     
         2 . The microelectronic unit of  claim 1 , wherein the first and second functions are substantially different. 
     
     
         3 . The microelectronic unit of  claim 1 , wherein a slope of horizontal dimension versus vertical location changes abruptly at a boundary between the base and the tip regions. 
     
     
         4 . The microelectronic unit of  claim 1 , wherein each of the plurality of microcontacts has a longitudinal axis and a pitch defined by a distance between a first and a second longitudinal axis, wherein the pitch is less than about 200 microns. 
     
     
         5 . The microelectronic unit of  claim 4 , wherein the pitch is less than about 150 microns. 
     
     
         6 . The microelectronic unit of  claim 1 , wherein there is another region disposed between the base and tip regions. 
     
     
         7 . The microelectronic unit of  claim 1 , wherein, within each of the microcontacts, the base region and the tip region are formed as a unitary body of metal. 
     
     
         8 . The microelectronic unit of  claim 1 , wherein the substrate includes a dielectric layer and traces extending along the dielectric layer, at least some of the traces being connected to at least some of the microcontacts. 
     
     
         9 . A microelectronic unit comprising:
 a substrate;   a plurality of microcontacts projecting in a vertical direction from the substrate wherein a pitch between two adjacent microcontacts is less than 150 microns.   
     
     
         10 . The microelectronic unit as claimed in  claim 9  wherein the pitch is less than h+d, where h is the vertical height of each microcontact and d is the diameter of each microcontact at a tip of the microcontact, remote from the substrate. 
     
     
         11 . The microelectronic unit as claimed in  claim 9  wherein each microcontact has a height of at least about 50 microns and a tip diameter of at least about 20 microns. 
     
     
         12 . The microelectronic unit as claimed in  claim 9  wherein each microcontact has a tip with a substantially flat, horizontal surface. 
     
     
         13 . A microelectronic unit comprising:
 (a) a substrate; and   (b) a plurality of elongated 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 an axis and a circumferential surface which slopes toward or away from the axis in the vertical direction along the axis, such that the slope of the circumferential wall changes abruptly at a boundary between the tip region and the base region.   
     
     
         14 . The microelectronic unit of  claim 13 , wherein, within each of the microcontacts, the base region and the tip region are formed as a unitary body of metal. 
     
     
         15 . The microelectronic unit of  claim 13 , wherein a pitch between adjacent microcontacts is less than about 150 microns and each microcontact has a height of about 60 to about 150 microns. 
     
     
         16 . The microelectronic unit of  claim 15 , wherein each microcontact has a tip diameter of at least about 20 microns. 
     
     
         17 . The microelectronic unit as claimed in  claim 13  wherein the pitch is less than h+d, where h is the vertical height of each microcontact and d is the diameter of each microcontact at a tip of the microcontact, remote from the substrate. 
     
     
         18 . The microelectronic unit as claimed in  claim 13  wherein the substrate includes a dielectric layer and traces extending along the dielectric layer, at least some of the traces being connected to at least some of the microcontacts. 
     
     
         19 . The microelectronic unit as claimed in  claim 18  wherein the microcontacts project from a first side of the dielectric layer, the unit also including terminals exposed at the second side of the dielectric layer and electrically connected to at least some of the microcontacts by the traces. 
     
     
         20 . An assembly including a microelectronic unit as claimed in  claim 19  and a microelectronic element having contacts connected to the microcontacts. 
     
     
         21 . The assembly of  claim 17 , wherein there is another region disposed between the base and tip regions. 
     
     
         22 . A microelectronic unit comprising:
 (a) a substrate; and   (b) a plurality of microcontacts projecting in a vertical direction from the substrate, each microcontact having a proximal portion adjacent the substrate and an elongated distal portion extending from the proximal portion in the vertical direction away from the substrate, the width of the post increasing in stepwise fashion at the juncture between the proximal and distal portions.