Method of controlling oxygen levels for electroless plating of catalytic fine lines or features

Abstract

A method of controlling oxygen levels for electroless plating of catalytic fine lines or features includes selecting a substrate that includes a plurality of catalytic lines or features that are part of or are disposed on the substrate. The plurality of catalytic lines or features include at least one catalytic fine line or feature and at least one catalytic standard line or feature. A dissolved oxygen concentration of an electroless plating solution is regulated to a candidate controlled oxygen level. The candidate controlled oxygen level is set to a smallest value in a regulated range in a first pass of the method. The substrate is submerged in the solution for a period of time sufficient to initiate plating of the at least one catalytic standard line or feature. The substrate is evaluated and candidate controlled oxygen level is incremented or the previous value is selected as the regulated oxygen level.

What is claimed is: 
     
         1 . A method of controlling oxygen levels for electroless plating of catalytic fine lines or features comprising:
 selecting a substrate that includes a plurality of catalytic lines or features that are part of or are disposed on the substrate, wherein the plurality of catalytic lines or features include at least one catalytic fine line or feature and at least one catalytic standard line or feature;   regulating a dissolved oxygen concentration of an electroless plating solution to a candidate controlled oxygen level, wherein the candidate controlled oxygen level is set to a smallest value in a regulated range in a first pass of the method;   submerging the substrate in the electroless plating solution for a period of time sufficient to initiate plating of the at least one catalytic standard line or feature;   removing the substrate from the electroless plating solution;   evaluating the substrate to determine whether the at least one catalytic fine line or feature initiated at approximately the same time as the at least one catalytic standard line or feature;   evaluating the substrate to determine whether the at least one catalytic fine line or feature exhibits one or more failure modes;   if the at least one catalytic fine line or feature initiated at approximately the same time as the at least one catalytic standard line or feature and did not exhibit one or more failure modes, incrementing the candidate controlled oxygen level by an increment and iterate the method; and   if the at least one catalytic fine line or feature exhibits one or more failure modes, selecting the previous value of the candidate controlled oxygen level as a regulated oxygen level.   
     
     
         2 . The method of  claim 1 ,
 wherein the at least one catalytic fine line or feature has the smallest width among the plurality of catalytic lines or features that are part of or are disposed on the substrate; and   wherein the at least one catalytic standard line or feature includes the largest width among the plurality of catalytic lines or features that are part of or are disposed on the substrate.   
     
     
         3 . The method of  claim 1 , wherein the at least one catalytic fine line or feature has a width less than approximately 5 micrometers. 
     
     
         4 . The method of  claim 1 , wherein the at least one catalytic fine line or feature has a width in a range between approximately 5 micrometers and approximately 10 micrometers. 
     
     
         5 . The method of  claim 1 , wherein the at least one catalytic fine line or feature has a width in a range between approximately 10 micrometers and approximately 20 micrometers. 
     
     
         6 . The method of  claim 1 , wherein the at least one catalytic standard line or feature has a width on the order of magnitude of at least 20 micrometers. 
     
     
         7 . The method of  claim 1 , wherein the at least one catalytic standard line or feature has a width on the order of magnitude of at least a millimeter. 
     
     
         8 . The method of  claim 1 , wherein the at least one catalytic standard line or feature has a width on the order of magnitude of at least a centimeter. 
     
     
         9 . The method of  claim 1 , wherein the at least one catalytic standard line or feature has a width on the order of magnitude of at least a decimeter. 
     
     
         10 . The method of  claim 1 , wherein regulating the dissolved oxygen concentration comprises controlling a surface area of the electroless plating solution exposed to air. 
     
     
         11 . The method of  claim 1 , wherein regulating the dissolved oxygen concentration comprises controlling a flow rate of inert gas that is introduced into the electroless plating solution. 
     
     
         12 . The method of  claim 1 , wherein regulating the dissolved oxygen concentration comprises controlling a flow rate of oxygen or gas containing oxygen that is introduced into the electroless plating solution. 
     
     
         13 . The method of  claim 1 , wherein regulating the dissolved oxygen concentration comprises controlling a recirculation speed of the electroless plating solution. 
     
     
         14 . The method of  claim 1 , wherein regulating the dissolved oxygen concentration comprises controlling an agitation level of the electroless plating solution. 
     
     
         15 . The method of  claim 1 , wherein regulating the dissolved oxygen concentration comprises increasing the dissolved oxygen concentration. 
     
     
         16 . The method of  claim 15 , wherein the dissolved oxygen concentration may be increased by:
 introducing oxygen or a gas containing oxygen into the electroless plating solution and diffusing the introduced oxygen or gas containing oxygen in the electroless plating solution.   
     
     
         17 . The method of  claim 15 , wherein the dissolved oxygen concentration may be increased by increasing a surface area of the electroless plating solution exposed to air. 
     
     
         18 . The method of  claim 1 , wherein regulating the dissolved oxygen concentration comprises reducing the dissolved oxygen concentration. 
     
     
         19 . The method of  claim 18 , wherein the dissolved oxygen concentration may be reduced by introducing an inert gas into the electroless plating solution. 
     
     
         20 . The method of  claim 18 , wherein the dissolved oxygen concentration may be reduced by pulling a vacuum. 
     
     
         21 . The method of  claim 1 , wherein the regulated range is in a range between approximately 0.6 PPM and approximately 1.6 PPM. 
     
     
         22 . The method of  claim 1 , wherein the regulated range is in a range between approximately 0.7 PPM and approximately 1.5 PPM. 
     
     
         23 . The method of  claim 1 , wherein the regulated range is in a range between approximately 0.8 PPM and approximately 1.4 PPM. 
     
     
         24 . The method of  claim 1 , wherein the regulated range is in a range between approximately 0.9 PPM and approximately 1.3 PPM. 
     
     
         25 . The method of  claim 1 , wherein the regulated range is in a range between approximately 1.0 PPM and approximately 1.2 PPM. 
     
     
         26 . The method of  claim 1 , wherein the determination of whether the at least one catalytic fine line or feature initiated at approximately the same time as the at least one catalytic standard line or feature comprises:
 examining a surface of the at least one catalytic standard line or feature for evidence of initiation;   examining a surface of the at least one catalytic fine line or feature for evidence, or lack thereof, of initiation; and   comparing the evidence of initiation for the at least one catalytic standard line or feature to the evidence, or lack thereof, of initiation for the at least one catalytic fine line or feature;   wherein the at least one catalytic fine line or feature is determined to have initiated at approximately the same time as the least one catalytic standard line or feature if the at least one catalytic fine line or feature exhibits approximately the same evidence of initiation as that of the at least one catalytic standard line or feature.   
     
     
         27 . The method of  claim 1 , wherein the determination of whether the at least one catalytic fine line or feature etched prior to initiation comprises:
 examining a shape of the at least one catalytic fine line or feature; and   comparing the shape of the at least one catalytic fine line or feature to a shape of a corresponding line or feature in a source design;   wherein the at least one catalytic fine line or feature is determined to have etched prior to initiation if the at least one catalytic line or feature exhibits narrow portions, breaks, or discontinuities that do not exist in the corresponding line or feature in the source design.   
     
     
         28 . The method of  claim 1 , wherein the dissolved oxygen concentration is monitored by dipping a dissolved oxygen meter into the electroless plating solution.