In-situ profile measurement in an electroplating process

Abstract

A method and apparatus for measuring differential voltages in an electrolyte of an electrochemical plating cell. Current densities are calculated from the measured differential voltages and correlated to thickness values of plated materials. A real time thickness profile may be generated from the thickness values.

1 . An electrochemical plating system, comprising,
 a fluid basin assembly having a fluid volume configured to retain an electrolyte therein;   a contact ring is configured to position a substrate in a plane across an upper portion of the fluid basin assembly and electrically contact the substrate for electrochemical plating;   an anode disposed in a lower portion of the fluid basin assembly; and   a sensor assembly disposed in the fluid volume, wherein the sensor assembly comprises at least a first sensor and a second sensor configured to measure local voltage levels in the fluid volume.   
     
     
         2 . The electrochemical plating system of  claim 1 , wherein the first and second sensors are positioned in a line substantially perpendicular to the plane where the substrate is positioned, and the first sensor is closer to the plane than the second sensor. 
     
     
         3 . The electrochemical plating system of  claim 2 , wherein the sensor assembly further comprises a third sensor, and the first sensor and the third sensor are positioned in a line substantially parallel to the plane. 
     
     
         4 . The electrochemical plating system of  claim 1 , wherein the first sensor and second sensor are wires electrically floating in the fluid volume. 
     
     
         5 . The electrochemical plating system of  claim 4 , wherein the wires are made of copper, copper plated over a novel metal, or a noble metal. 
     
     
         6 . The electrochemical plating system of  claim 1 , wherein the sensor assembly comprises an array of sensors distributed from near a center of the fluid basin assembly to near an edge region of the fluid basin assembly. 
     
     
         7 . The electrochemical plating system of  claim 6 , wherein the array of sensors comprise:
 a first row of sensors disposed on a printed circuit board; and   a second row of sensors disposed on the printed circuit board, wherein the first row of sensors are positioned in a distance closer to the plane than the second row of sensors.   
     
     
         8 . The electrochemical plating system of  claim 6 , wherein the array of sensors are disposed in a spiral pattern. 
     
     
         9 . The electrochemical plating system of  claim 1  further comprising a diffusion plate disposed in the fluid volume above the anode, wherein the sensor assembly is integrated in the diffusion plate. 
     
     
         10 . The electrochemical plating system of  claim 1 , further comprising a control unit connected to the sensor assembly and configured to determine a voltage difference between the first sensor and the second sensor, wherein the control unit comprises:
 an electric circuit connected to the sensor assembly, wherein the electric circuit is configured to sample and process input of the sensor assembly.   
     
     
         11 . An electrochemical plating system, comprising,
 a fluid basin assembly having a fluid volume configured to retain an electrolyte therein;   a contact ring having one or more electric contacting elements configured electrically contact a perimeter of a substrate being processed, wherein the contact ring is configured to support the substrate and position the substrate across an upper portion of the fluid volume;   an anode disposed in a lower portion of the fluid basin assembly;   a power supply coupled to connected to the contact ring and the anode to apply a bias between the contact ring and the anode; and   a sensor assembly comprising at least a first sensor and a second sensor, wherein the first and second sensors are conductors electronically floating in the fluid volume; and   a signal sampling and processing circuit connected to the sensor assembly, wherein the signal sampling and processing circuit is configured to obtain a voltage difference between the first sensor and the second sensor.   
     
     
         12 . The system of  claim 10 , wherein the sensors assembly comprise:
 a first row of sensors disposed in the fluid volume; and   a second row of sensors disposed directly underneath the first row of sensors, wherein the signal sampling and processing circuit is connected to obtain voltage differences between each sensor in the first row of sensors and a perspective sensor in on the second row of the sensors.   
     
     
         13 . The system of  claim 12 , wherein the first row and second row of sensors are conductors on a printed circuit board disposed in the fluid volume. 
     
     
         14 . The system of  claim 12 , wherein the first rows and the second rows of sensors are distributed across a radius of the fluid volume. 
     
     
         15 . The system of  claim 12 , wherein the first rows and the second rows of sensors are disposed in a spiral pattern. 
     
     
         16 . The system of  claim 10 , further comprising a diffusion plate disposed in the fluid volume above the anode, wherein the sensor assembly is integrated in the diffusion plate. 
     
     
         17 . A patterned substrate for calibrating a sensor assembly in an electrochemical plating cell, wherein the electroplating cell comprises a fluid basin assembly having a fluid volume, a contact ring is configured to position a substrate in a plane across an upper portion of the fluid basin assembly, an anode disposed in a lower portion of the fluid basin assembly, and the sensor assembly disposed in the fluid volume, comprising:
 a first conductive patch; and   a first contact point positioned in an edge of the patterned substrate and configured to connect the contact ring of the electroplating cell, wherein the first conductive patch is in electric communication with the first contact point through a protected trace.   
     
     
         18 . The patterned substrate of  claim 17 , further comprising:
 a plurality of conductive patches insulated from one another; and   a plurality of contact points insulated from one another positioned in the edge of the patterned substrate, wherein each of the plurality of the contact points is adapted to align with an individual contact pin of the contact ring of the electroplating cell, and each of the plurality of the conductive patches is in electric communication with a corresponding contact point of the plurality of the contact points.   
     
     
         19 . The patterned substrate of  claim 18 , wherein the plurality of patches are distributed across a radius of the patterned substrate. 
     
     
         20 . The patterned substrate of  claim 18 , wherein the plurality of patches are distributed in a straight line across a radius of the patterned substrate.