Method for improving electroplating in sub-0.1um interconnects by adjusting immersion conditions

Abstract

Embodiments of the invention provide methods of reducing electroplating defects by adjusting immersion conditions. For one embodiment, the immersion conditions are adjusted based upon characteristics of the substrate, including feature size. Additionally or alternatively, the immersion conditions may be adjusted based upon aspects of the electroplating process, including motion of the substrate upon immersion. Immersion conditions that may be adjusted in accordance with various embodiments of the invention include entry bias voltage/current, vertical immersion speed, and angle of immersion.

What is claimed is:  
     
         1 . A method comprising: 
 evaluating one or more characteristics of a wafer; and    determining one or more wafer immersion conditions of a set of wafer immersion conditions of an electroplating process based upon one or more of the characteristics.    
     
     
         2 . The method of  claim 1  wherein the wafer includes at least one feature and the one or more characteristics include a dimension of one of the features.  
     
     
         3 . The method of  claim 2  wherein the one or more wafer immersion conditions includes an entry bias voltage.  
     
     
         4 . The method of  claim 3  wherein the dimension of one of the features is less than 0.1 um and the entry bias voltage is in the range of 0.3V-0.8V.  
     
     
         5 . The method of  claim 1 , further comprising: 
 evaluating one or more aspects of the electroplating process; and    determining additional wafer immersion conditions based upon one or more of the aspects of the electroplating process.    
     
     
         6 . The method of  claim 5  wherein the one or more aspects of the electroplating process include a motion of the wafer upon immersion and the additional wafer immersion conditions include a vertical immersion speed of the wafer.  
     
     
         7 . The method of  claim 6  wherein the vertical immersion speed of the wafer is less than 12 millimeters per second.  
     
     
         8 . The method of  claim 6  wherein the additional wafer immersion conditions include an angle of immersion of the wafer.  
     
     
         9 . An apparatus comprising: 
 a substrate having one or more features formed thereon; and    a layer of conductive metal formed on the substrate through an electroplating process applying an entry bias current that substantially reduces etching of a seed layer by acid with an electroplating solution, the entry bias current also substantially reducing unregulated electroplating during immersion of the substrate into the electroplating solution, and subsequently applying a regulated current waveform such that the one or more features are filled, the electroplating process helping to reduce the occurrence of voids or seams in the layer of conductive metal.    
     
     
         10 . The apparatus of  claim 9  wherein the substrate comprises a semiconductor wafer and the layer of conductive metal comprises a layer of copper.  
     
     
         11 . The apparatus of  claim 9  wherein at least one of the features has dimensions of less than 0.1 um.  
     
     
         12 . The apparatus of  claim 11  wherein the entry bias current is in the range of 0A-1A.  
     
     
         13 . A method comprising: 
 applying an entry bias voltage to a substrate having a metal seed layer deposited thereon and a plating cell anode, the entry bias voltage selected to help reduce etching of the metal seed layer and helping to reduce unregulated electroplating of the substrate;    completely immersing the wafer in an electroplating solution; and    applying a regulated current waveform to electroplate a desired metal layer on the substrate.    
     
     
         14 . The method of  claim 13  wherein the entry bias voltage is selected such that substantially no etching of the metal seed layer occurs and substantially no unregulated electroplating of the substrate occurs.  
     
     
         15 . The method of  claim 13  wherein the substrate has a plurality of features formed thereon and the entry bias voltage is selected such that unregulated electroplating during immersion does not fill the features.  
     
     
         16 . The method of  claim 15  wherein at least one of the features has a dimension of less than 0.1 um and the entry bias voltage is between 0.3V and 0.8V.  
     
     
         17 . The method of  claim 15  wherein the substrate comprises a semiconductor wafer and the metal seed layer comprises a copper layer.  
     
     
         18 . The method of  claim 16  wherein the entry bias voltage is selected based upon the dimension of the at least one feature and an aspect ratio of the at least one feature.  
     
     
         19 . A method comprising: 
 determining a vertical immersion velocity of a substrate into an electroplating solution for a specified electroplating process, the substrate having features formed thereon and a metal seed layer deposited thereon, the vertical immersion velocity determined such that the occurrence of defects in a resulting electroplate is reduced;    determining an angle of immersion for the substrate into the electroplating solution for the electroplating process, the angle of immersion determined such that the occurrence of defects in a resulting electroplate is reduced; and    immersing the substrate at the determined vertical immersion velocity and determined angle of immersion.    
     
     
         20 . The method of  claim 19  wherein the vertical immersion velocity is less than 50 millimeters per second.  
     
     
         21 . The method of  claim 19  wherein the vertical immersion velocity is more than 12 millimeters per second.  
     
     
         22 . The method of  claim 19  wherein the substrate comprises a semiconductor wafer and the metal seed layer comprises a copper seed layer.  
     
     
         23 . The method of  claim 19  wherein the vertical immersion velocity and the angle of immersion are determined based upon one or more aspects of the specified electroplating process.  
     
     
         24 . The method of  claim 23  wherein the one or more aspects of the specified electroplating process include the electroplating tool and motion of the substrate upon entry into the electroplating solution.