Electrochemical polishing method and polishing method

Abstract

The present invention provides an electrochemical polishing method capable of increasing a polishing speed while preventing excessive polishing, such as dishing or erosion. In the electrochemical polishing method, when a voltage applied to a conductive film formed on the surface of a substrate is increased at a contact surface pressure of 0 between the surface of the substrate and a polishing pad, a voltage at a first change point C that allows a current density to start to decrease after an increase is referred to as a minimum voltage. In addition, when the voltage is increased at a contact surface pressure having a finite value, a voltage at a second change point B that allows the current density to be maintained constant after the decrease is referred to as a maximum voltage. In this case, the surface of the conductive film is polished while maintaining the voltage to be not lower than the minimum voltage and not higher than the maximum voltage. Further, the present invention provides an electrochemical polishing method capable of rapidly removing a conductive film in regions other than a contact plug or wiring line forming region while preventing excessive polishing, such as dishing or erosion. In the electrochemical polishing method, in a step of increasing a voltage, when the voltage is increased at a contact surface pressure of 0, a voltage at a first change point C that allows a current density to start to decrease after an increase is referred to as a threshold voltage, and the voltage is increased such that a voltage in a region in which a barrier film is exposed is higher than the threshold voltage.

1 . An electrochemical polishing method comprising:
 a step of contacting an electrolyte with a conductive film formed on the surface  5  of a substrate to apply a voltage to the conductive film; and   a step of moving the substrate relative to a polishing pad while pressing the surface of the substrate against the polishing pad at a predetermined contact surface pressure, thereby polishing the surface of the conductive film,   wherein the electrolyte has a pH in the range of 4 to 10,   when the voltage is increased at a contact surface pressure of 0, a voltage that allows a current density to start to decrease after an increase is referred to as a minimum voltage,   when the voltage is increased at a contact surface pressure having a finite value, a voltage that allows the current density not to decrease any further after the decrease is 15 referred to as a maximum voltage, and   the surface of the conductive film is polished while maintaining the voltage to be not lower than the minimum voltage and not higher than the maximum voltage.   
   
   
       2 . An electrochemical polishing method comprising:
 a step of contacting an electrolyte with a conductive film formed on the surface of a substrate to apply a voltage to the conductive film; and   a step of moving the substrate relative to a polishing pad while pressing the surface of the substrate against the polishing pad at a predetermined contact surface pressure, thereby polishing the surface of the conductive film,   wherein the electrolyte has a pH in the range of 4 to 10,   when the voltage is increased at a contact surface pressure of 0, a voltage that allows a current density to start to decrease after an increase is referred to as a minimum voltage,   when the voltage is increased at a contact surface pressure having a finite value,   a voltage that allows the current density to start to decrease after an increase is referred to as a maximum voltage, and   the surface of the conductive film is polished while maintaining the voltage to be not lower than the minimum voltage and not higher than the maximum voltage.   
   
   
       3 . The electrochemical polishing method according to  claim 1 , wherein the polishing speed of the conductive film is controlled by adjusting the pH of the electrolyte. 
   
   
       4 . The electrochemical polishing method according to  claim 1 ,
 wherein the electrolyte includes an additive that reacts with the conductive film to generate an electrical insulating material, and   the polishing speed of the conductive film is controlled by adjusting the concentration of the additive.   
   
   
       5 . The electrochemical polishing method according to  claim 1 ,
 wherein the polishing speed of the conductive film is controlled by adjusting the number of revolutions of the polishing pad.   
   
   
       6 . The electrochemical polishing method according to  claim 1 ,
 wherein the conductive film is a tungsten film.   
   
   
       7 . A polishing method comprising:
 a protective firm forming step of applying a voltage that is not lower than a threshold voltage to a conductive film contacting an electrolyte, without contacting a  5  substrate with a polishing pad, thereby forming a protective film on the surface of the conductive film; and   a polishing step of moving the substrate relative to the polishing pad while pressing the surface of the substrate against the polishing pad at a predetermined contact surface pressure, thereby polishing the conductive film formed on the surface of the substrate,   wherein, when the voltage that is applied to the conductive film contacting the electrolyte is increased at a contact surface pressure of 0 while moving the substrate relative to the polishing pad, a voltage that allows a current density not to decrease after an increase is referred to as the threshold voltage.   
   
   
       8 . The polishing method according to  claim 7 ,
 wherein the polishing step is a chemical mechanical polishing step or an electrochemical polishing step.   
   
   
       9 . The polishing method according to  claim 7 , wherein the conductive film is a tungsten film. 
   
   
       10 . An electrochemical polishing method comprising:
 a step of contacting an electrolyte with a metal film formed on the surface of a  25  substrate to apply a voltage to the metal film, the electrolyte having a pH in the range of 4 to 10 and the metal film including an underlying film, which is a lower layer, and a conductive film, which is an upper layer, having an electric resistance that is lower than that of the underlying film;   a step of moving the substrate relative to a polishing pad while pressing the surface of the substrate against the polishing pad at a predetermined contact surface pressure, thereby polishing the surface of the metal film;   a step of removing a portion of the conductive film in the vicinity of a point where the voltage is applied first to expose the underlying film; and   a step of increasing the voltage immediately before the exposure of the  10  underlying film or after the exposure of the underlying film the underlying film is exposed,   wherein, in the step of increasing the voltage,   when the voltage is increased at a contact surface pressure of 0 while moving the substrate relative to the polishing pad, a voltage that allows a current density to start to decrease after an increase is referred to as a threshold voltage, and the voltage is increased such that a voltage in a region in which the underlying film is exposed is higher than the threshold voltage.   
   
   
       11 . The electrochemical polishing method according to  claim 10 ,
 wherein, in the step of increasing the voltage,   when the voltage is increased at a contact surface pressure having a finite value, a voltage that allows the current density not to decrease after an increase is referred to as a maximum voltage, and   the voltage is increased such that a voltage in regions other than the region in which the underlying film is exposed is higher than the threshold voltage and lower than the maximum voltage.   
   
   
       12 . The electrochemical polishing method according to  claim 10 ,
 wherein, in the step of exposing the underlying film, the contact surface pressure between the substrate and the polishing pad in the region in the vicinity of the voltage application point is higher than that in regions other than the region in the vicinity of the voltage application point.   
   
   
       13 . The electrochemical polishing method according to  claim 10 ,
 wherein, in the step of exposing the underlying film,   an electrode opposite to the substrate is divided into a plurality of small electrodes that are concentrically arranged on the same plane, and   the voltage applied to the divided electrodes is controlled such that a portion of the conductive film that is more frequently opposite to an outer portion of the substrate is more rapidly polished.   
   
   
       14 . The electrochemical polishing method according to  claim 10 ,
 wherein, in the polishing step, polishing is performed while measuring the thickness of the remaining conductive film using an overcurrent method.   
   
   
       15 . The electrochemical polishing method according to  claim 10 ,
 wherein the conductive film is a tungsten film.   
   
   
       16 . An electrochemical polishing method comprising:
 a step of contacting an electrolyte with a metal film formed on the surface of a substrate to apply a voltage to the metal film, the electrolyte having a pH in the range of 4 to 10 and the metal film including an underlying film, which is a lower layer, and a conductive film, which is an upper layer, having an electric resistance that is lower than that of the underlying film;   a step of moving the substrate relative to a polishing pad while pressing the surface of the substrate against the polishing pad at a predetermined contact surface pressure, thereby polishing the surface of the metal film;   a step of arranging a point where the voltage is applied in a circumferential portion of the substrate and removing the conductive film in the circumferential portion first to expose the underlying film; and   a step of moving the voltage application point from the circumferential portion to the center of the substrate to expose the underlying film.   
   
   
       17 . An electrochemical polishing method comprising:
 a step of contacting an electrolyte with a metal film formed on the surface of a substrate to apply a voltage to the metal film, the electrolyte having a pH in the range of 4 to 10 and the metal film including an underlying film, which is a lower layer, and a conductive film, which is an upper layer, having an electric resistance that is lower than that of the underlying film;   a step of moving the substrate relative to a polishing pad while pressing the surface of the substrate against the polishing pad at a predetermined contact surface pressure, thereby polishing the surface of the metal film;   a step of arranging a point where the voltage is applied in a circumferential portion of the substrate and removing the conductive film in the circumferential portion first to expose the underlying film;   a step of moving the voltage application point from the circumferential portion  5  to the center of the substrate to expose the underlying film; and   a step of increasing the voltage immediately before the exposure of the underlying film or after the exposure of the underlying film the underlying film is exposed,   wherein, in the step of increasing the voltage,   when the voltage is increased at a contact surface pressure of 0 while moving the substrate relative to the polishing pad, a voltage that allows a current density to start to decrease after an increase is referred to as a threshold voltage, and   the voltage is increased such that a voltage in a region in which the underlying film is exposed is higher than the threshold voltage.   
   
   
       18 . The electrochemical polishing method according to  claim 1 , wherein a positive voltage is applied to the conductive film. 
   
   
       19 . The electrochemical polishing method according to  claim 2 ,
 wherein the polishing speed of the conductive film is controlled by adjusting the pH of the electrolyte.   
   
   
       20 . The electrochemical polishing method according to  claim 2 ,
 wherein the electrolyte includes an additive that reacts with the conductive film to generate an electrical insulating material, and   the polishing speed of the conductive film is controlled by adjusting the concentration of the additive.   
   
   
       21 . The electrochemical polishing method according to  claim 2 ,
 wherein the polishing speed of the conductive film is controlled by adjusting the number of revolutions of the polishing pad.   
   
   
       22 . The electrochemical polishing method according to  claim 2 ,
 wherein the conductive film is a tungsten film.   
   
   
       23 . The polishing method according to  claim 8 , wherein the conductive film is a tungsten film. 
   
   
       24 . The electrochemical polishing method according to  claim 2 , wherein a positive voltage is applied to the conductive film. 
   
   
       25 . The electrochemical polishing method according to  claim 7 , wherein a positive voltage is applied to the conductive film.