Stable electroless fine pitch interconnect plating

Abstract

A method and apparatus for plating facilitates the plating of a small contact feature of a wafer die while providing a relatively stable plating bath. The method utilizes a supplemental plating structure that is larger than a die contact that is to be plated. The supplemental plating structure may be located on the wafer, and is conductively connected to the die contact. Conductive connection between the die contact and the supplemental plating structure facilitates the plating of the die contact. The supplemental plating structure also can be used to probe test the die prior to singulation.

1 - 36 . (canceled)  
   
   
       37 . A plating apparatus comprising: 
 an electroless plating bath for plating at least portions of semiconductor wafers; and    a system controller for controlling contents of the electroless plating bath, wherein said contents include: 
 a nickel salt;  
 a hypopohosphite salt;  
 at least one organic acid or chelating agent; and  
 a stabilizer.  
   
   
   
       38 . The apparatus of  claim 37 , wherein the system controller includes an autotitrator.  
   
   
       39 . The apparatus of  claim 37 , wherein said system controller monitors the stability of the plating bath and determines the rate of injection for said contents.  
   
   
       40 . The apparatus of  claim 39 , wherein said system controller includes a calibrator for calibrating the stabilizer concentration in said electroless bath.  
   
   
       41 . The apparatus of  claim 37 , wherein said electroless plating bath includes a means for stacking said semiconductor wafers one above the other during said plating.  
   
   
       42 . The apparatus of  claim 37 , wherein said electorless bath plates said supplemental plating structures on each said die.  
   
   
       43 . The apparatus of  claim 42 , wherein said electroless bath also plates said contacts.  
   
   
       44 . The apparatus of  claim 37 , wherein said electroless bath plates portions of said semiconductor wafers including a die contact and a supplemental plating structure conductively connected to said contact.  
   
   
       45 . A controller for controlling a plating method, said controller comprising: 
 a monitor for monitoring the stability of an electroless plating bath for electrolessly plating features on semiconductor wafers; and    an injector for injecting contents into said plating bath, wherein the contents include: 
 a nickel salt;  
 a hypopohosphite salt;  
 at least one organic acid or chelating agent; and  
 a stabilizer.  
   
   
   
       46 . The controller of  claim 45 , wherein said controller comprises a computer.  
   
   
       47 . The controller of  claim 45 , further comprising an autotitrator for titrating the contents to a pre-determined concentration.  
   
   
       48 . The controller of  claim 47 , wherein the pre-determined concentration is calibrated by said controller using a size of said features to be plated.  
   
   
       49 . The controller of  claim 45 , wherein said nickel salt is NiSO 4 .  
   
   
       50 . The controller of  claim 45 , wherein said hypophosphite salt is NaH 2 PO 2  or NH 4 H 2 PO 2 .  
   
   
       51 . The controller of  claim 45 , wherein said stabilizer is selected from the group consisting of S, Se, Te, AsO 2   − , IO 3   − , MoO 4   2− , heavy metal cations, and unsaturated organic acids.