Process for electroplating metals into microscopic recessed features

Abstract

Several techniques are described for reducing or mitigating the formation of seams and/or voids in electroplating the interior regions of microscopic recessed features. Cathodic polarization is used to mitigate the deleterious effects of introducing a substrate plated with a seed layer into an electroplating solution. Also described are diffusion-controlled electroplating techniques to provide for bottom-up filling of trenches and vias, avoiding thereby sidewalls growing together to create seams/voids. A preliminary plating step is also described that plates a thin film of conductor on the interior surfaces of features leading to adequate electrical conductivity to the feature bottom, facilitating bottom-up filling.

1 - 28 . (canceled) 
     
     
         29 . A method of electroplating copper into trenches on a semiconductor substrate, the method comprising:
 (a) setting a power supply to provide a cathodic current that flows from an anode to the substrate immediately upon the substrate contacting an electrolyte in the plating bath; and   (b) increasing the current flowing between anode and substrate to a higher level than supplied in (a), wherein increasing the current is conducted substantially contemporaneously with or before the substrate contacts the electrolyte; and   (c) conducting an initiation phase upon the substrate's entry in the electrolyte, wherein at least a portion of the initiation phase is conducted at a current of between about 0.1 and 5 mA/cm2.   
     
     
         30 . The method of  claim 29 , wherein (a) and/or (b) comprises applying a cathodic voltage with reference electrode prior to the substrate making contact with the electrolyte. 
     
     
         31 . The method of  claim 29 , wherein the substrate comprise a copper seed layer onto which copper is plated. 
     
     
         32 . The method of  claim 29 , further comprising superimposing current pulses on the current delivered during (c). 
     
     
         33 . An apparatus for electroplating copper into trenches on a semiconductor substrate, the apparatus comprising:
 A vessel for containing electrolyte during plating;   A power supply; and   A controller configured to   (a) set the power supply to provide a cathodic current that flows from an anode to the substrate immediately upon the substrate contacting an electrolyte in the plating bath; and   (b) increase the current flowing between anode and substrate to a higher level than supplied in (a), wherein increasing the current is conducted substantially contemporaneously with or before the substrate contacts the electrolyte; and   (c) conduct an initiation phase upon the substrate's entry in the electrolyte, wherein at least a portion of the initiation phase is conducted at a current of between about 0.1 and 5 mA/cm2.