Method of Using a Barrier-Seed Tool for Forming Fine Pitched Metal Interconnects

Abstract

A barrier seed tool is configured to clean trenches in a first chamber, line the trenches with a diffusion barrier layer, and form a copper seed layer over the diffusion barrier layer in a second chamber. The clean chamber is configured to reduce overhangs in the copper seed layer by producing a plasma comprising positively and negatively charged ions including halogen ions, filtering the plasma to selectively exclude positively charged ions, and bombarding with the filtered plasma. The tool and related method can be used to reduce overhangs and improve subsequent gap fill while avoiding excessive damage to the dielectric matrix.

What is claimed is: 
     
         1 . A copper barrier-seed tool, comprising:
 a copper diffusion barrier deposition chamber;   a copper seed layer deposition chamber; and   a cleaning chamber that comprises:
 a first volume equipped with a plasma generator; 
 a second volume equipped with a wafer support; and 
 an ion filter separating the first volume from the second volume. 
   
     
     
         2 . The tool of  claim 1 , wherein the wafer support is a heated pedestal coupled to a voltage supply. 
     
     
         3 . The tool of  claim 2 , further comprising a first heater configured to heat a wall enclosing the second volume. 
     
     
         4 . The tool of  claim 3 , wherein the first heater is positioned adjacent to the wall enclosing the second volume. 
     
     
         5 . The tool of  claim 4 , wherein the first heater is functional to heat the wall to a first temperature in a range between 50° C. and 100° C. 
     
     
         6 . The tool of  claim 5 , wherein the wafer support includes a second heater to heat a wafer mounted on the heated pedestal to a second temperature that is at least two times as large as the first temperature. 
     
     
         7 . The tool of  claim 6 , wherein the second temperature is in a range between 200° C. and 300° C. 
     
     
         8 . The tool of  claim 1 , wherein the ion filter is set to exclude positive ions while permitting the passage of negative ions. 
     
     
         9 . The tool of  claim 6 , further comprising a degas chamber configured to perform a degas operation by heating the wafer to a third temperature at which water adsorbed on the surface of the wafer desorbs. 
     
     
         10 . The tool of  claim 9 , wherein the degas chamber puts the wafer under vacuum to reduce temperatures at which gases desorb. 
     
     
         11 . The tool of  claim 9 , further comprising:
 a loading device configured to load wafers from a wafer cassette into a central area of the copper barrier seed tool, the central area of the copper barrier seed tool including equipment to transport wafers between the copper diffusion barrier deposition chamber, the copper seed layer deposition chamber, the cleaning chamber, and the degas chamber.   
     
     
         12 . A copper barrier-seed tool, comprising:
 a loading device configured to load a wafer from a wafer cassette into a central area of the copper barrier seed tool, the wafer including a dielectric matrix layer with patterned trenches in the dielectric matrix layer;   a copper diffusion barrier deposition chamber adjacent to the central area of the copper barrier seed tool and configured to receive the wafer including the dielectric matrix layer with the patterned trenches in the dielectric matrix layer, the copper diffusion barrier deposition chamber configure to form a copper diffusion barrier layer along lower surfaces and sidewalls of the patterned trenches;   a copper seed layer deposition chamber adjacent to the central area of the copper barrier seed tool and configured to receive the wafer including the copper diffusion barrier layer, the copper seed layer deposition chamber configured to form a copper seed layer over the copper diffusion barrier layer in the patterned trenches, the copper seed layer having an overhang proximate uppermost openings of the patterned trenches; and   a cleaning chamber configured to generate a plasma comprising ions, filter the ions of the plasma to generate a filtered plasma, and bombard the copper seed layer with the filtered plasma to reduce the overhang.   
     
     
         13 . The copper barrier-seed tool of  claim 12 , wherein the cleaning chamber comprises:
 a first volume equipped with a plasma generator to generate the plasma comprises the ions;   a second volume equipped with a wafer support to retain the wafer; and   an ion filter separating the first volume from the second volume, the ion filter configured to filter the ions of the plasm to generate the filtered plasma.   
     
     
         14 . The copper barrier-seed tool of  claim 13 , further comprising a degas chamber configured to perform a degas operation by putting the wafer under vacuum to reduce temperatures at which gases desorb and then heating the wafer to a first temperature at which water adsorbed on the surface of the wafer desorbs. 
     
     
         15 . The tool of  claim 14 , wherein the wafer support is a heated pedestal coupled to a voltage supply. 
     
     
         16 . The tool of  claim 15 , further comprising a heater positioned adjacent to the wall enclosing the second volume, the heater configured to heat a wall enclosing the second volume. 
     
     
         17 . The tool of  claim 4 , wherein the heater is functional to heat the wall to a first temperature in a range between 50° C. and 100° C., and wherein the wafer support is configured to heat the wafer to a second temperature in a range between 200° C. and 300° C. 
     
     
         18 . A device, comprising:
 a semiconductor substrate;   a dielectric layer disposed over the semiconductor substrate;   a diffusion barrier layer lining trenches which are disposed in the dielectric layer, the trenches each having a width of 32 nanometers or less and having a pitch of 64 nanometers or less, and the diffusion barrier lining continuing downward from lower extents of the trenches to line sidewalls and lower surfaces of vias which extend downward from bottom surfaces of the trenches; and   a copper seed layer lining the trenches and the vias over the diffusion barrier layer, wherein the copper seed layer includes a first overhang region that protrudes outwardly from a shoulder region when a via meets a trench and a second overhang region the protrudes outwardly from an uppermost sidewall of the copper seed at the top of the trench.   
     
     
         19 . The device of  claim 18 , wherein the first overhang region lines opposite sides of the via and the second overhang region lines opposite sides of the trench such that nearest inner sidewalls of the first overhang region are more closely spaced than nearest inner sidewalls of the second overhang region. 
     
     
         20 . The device of  claim 18 , wherein the diffusion barrier layer completely separates the copper seed layer from the dielectric layer.