Method and apparatus for improving sidewall coverage during sputtering in a chamber having an inductively coupled plasma

Abstract

Increased sidewall coverage by a sputtered material is achieved by generating an ionizing plasma in a relatively low pressure sputtering gas. By reducing the pressure of the sputtering gas, it is believed that the ionization rate of the deposition material passing through the plasma is correspondingly reduced which in turn is believed to increase the sidewall coverage by the underlayer. Although the ionization rate is decreased, sufficient bottom coverage of the by the material is maintained. In an alternative embodiment, increased sidewall coverage by the material may be achieved even in a high density plasma chamber by generating the high density plasma only during an initial portion of the material deposition. Once good bottom coverage has been achieved, the RF power to the coil generating the high density plasma may be turned off entirely and the remainder of the deposition conducted without the high density plasma. Consequently, it has been found that good sidewall coverage is achieved in the latter part of the deposition.

1 . A process for sputter depositing a layer of material into a workpiece structure having a sidewall, comprising: 
 providing a sputtering gas into a chamber at a pressure below 20 mTorr;    applying RF power to a coil to ionize the sputtering gas to form a plasma;    sputtering a target to sputter target material toward a workpiece; and    ionizing a portion of said sputtered target material before it is deposited onto said workpiece.    
     
     
         2 . The process of  claim 1  wherein said sputtering gas is at a pressure of 5-10 mTorr.  
     
     
         3 . The process of  claim 1  wherein said target material is selected from the group of titanium, tantalum, aluminum, copper and tungsten.  
     
     
         4 . The process of  claim 3  wherein said target material is a compound of nitrogen and a material selected from the group of tantalum and titanium.  
     
     
         5 . A process for sputter depositing a layer of material into a via or channel of a workpiece, comprising: 
 providing a sputtering gas into a chamber;    applying RF power to a coil to ionize the sputtering gas to form a plasma;    sputtering a target to sputter target material toward a workpiece;    ionizing a portion of said sputtered target material before it is deposited onto said workpiece;    reducing said RF power to said coil while continuing to sputter said target so as to reduce ionization of said sputtered target material before it is deposited onto said workpiece.    
     
     
         6 . The process of  claim 5  wherein said RF power reducing step reduces said RF power to zero.  
     
     
         7 . A process for sputter depositing a layer of material into an opening of a workpiece, said opening having a bottom and sidewalls, said process comprising: 
 sputtering a target to sputter target material toward a workpiece;    ionizing a portion of said sputtered target material before it is deposited onto said workpiece so that sputtered material which is deposited in said opening is deposited primarily on the bottom of said opening; and    reducing said ionizing of sputtered material so that sputtered material deposited in said opening is deposited primarily on the sidewalls of said opening.    
     
     
         8 . The process of  claim 7  wherein said ionizing reducing step reduces ionization of sputtered material to zero.  
     
     
         9 . The process of  claim 7  wherein said sputtering gas is at a pressure of 5-10 mTorr.  
     
     
         10 . The process of  claim 7  wherein said target material is selected from the group of titanium, tantalum, aluminum, copper and tungsten.  
     
     
         11 . A process for sputter depositing layers of materials into a workpiece structure having a sidewall and a bottom, comprising: 
 sputtering a first target in a first chamber to sputter target material toward a workpiece;    ionizing a portion of said sputtered first target material before it is deposited onto said workpiece so that sputtered material which is deposited on said structure is deposited primarily on the bottom of said structure; and    reducing said ionizing of said sputtered first target material so that sputtered first target material deposited on said structure is deposited primarily on the sidewalls of said structure;    transferring said workpiece to a second chamber;    sputtering a second target to sputter a second target material onto said structure of said workpiece to deposit on top of said first material deposited on said structure.    
     
     
         12 . The process of  claim 11  wherein said sputtering gas is at a pressure of 5-10 mTorr.  
     
     
         13 . The process of  claim 11  wherein said first target material is selected from the group of titanium, tantalum, aluminum, copper and tungsten.  
     
     
         14 . The process of  claim 11  wherein said second target material is selected from the group of aluminum and copper.  
     
     
         15 . A process for sputter depositing layers of materials into a via or channel of a workpiece, comprising: 
 providing a sputtering gas into a first chamber at a pressure below 20 mTorr;    applying RF power to a coil in said first chamber to ionize said sputtering gas to form a plasma;    sputtering a target to sputter a first target material toward a workpiece;    ionizing a portion of said sputtered target material before it is deposited onto said workpiece;    transferring said workpiece to a second chamber;    sputtering a second target to sputter a second target material toward said workpiece.    
     
     
         16 . The process of  claim 15  wherein said sputtering gas is at a pressure of 5-10 mTorr.  
     
     
         17 . The process of  claim 15  wherein said first target material is selected from the group of titanium, tantalum, aluminum, copper and tungsten.  
     
     
         18 . The process of  claim 15  wherein said second target material is selected from the group of aluminum and copper.  
     
     
         19 . An apparatus for energizing a plasma within a semiconductor fabrication system to sputter material onto a workpiece, the apparatus comprising: 
 a semiconductor fabrication chamber having a plasma generation area within said chamber and containing a sputtering gas at a pressure less than 25 mTorr; and    a coil carried by said chamber and positioned to couple energy into said plasma generation area.    
     
     
         20 . The apparatus of  claim 19  including a target including is a target material selected from the group of titanium, tantalum, aluminum, copper and tungsten.  
     
     
         21 . A semiconductor fabrication system for sputtering multiple layers of materials onto a workpiece, the system comprising: 
 a first semiconductor fabrication chamber having a plasma generation area within said chamber and containing a sputtering gas at a pressure less than 25 mTorr;    said first chamber having a target of a first target material which includes a material selected from the group of titanium, tantalum, aluminum, copper and tungsten;    a coil carried by said first chamber and positioned to couple energy into said plasma generation area to ionize said first target material to form an underlayer of said first material on said workpiece;    a second semiconductor fabrication chamber; and    said second chamber having a second target of a second target material which includes a material selected from the group of aluminum and copper, for forming a layer on said underlayer.    
     
     
         22 . An apparatus for energizing a plasma within a semiconductor fabrication system to sputter material onto a workpiece, the apparatus comprising: 
 a semiconductor fabrication chamber having a plasma generation area within said chamber;    a coil carried by said chamber and positioned to couple energy into said plasma generation area to ionize said material prior to deposition onto said workpiece;    an RF generator coupled to said coil to provide RF power to said coil; and    control means for controlling said RF generator to provide power at a high level during an initial portion of a sputter deposition and to provide power at a reduced level including zero power in a subsequent portion of said sputter deposition.    
     
     
         23 . The apparatus of  claim 22  including a target including a material selected from the group of titanium, tantalum, aluminum, copper and tungsten.  
     
     
         24 . A semiconductor fabrication system for sputtering multiple layers of materials onto a workpiece, the system comprising: 
 a first semiconductor fabrication chamber having a plasma generation area within said chamber and a target of a first target material which includes a material selected from the group of titanium, tantalum, aluminum, copper and tungsten;    a coil carried by said chamber and positioned to couple energy into said plasma generation area to ionize said first target material prior to deposition onto said workpiece;    an RF generator coupled to said coil to provide RF power to said coil; and    control means for controlling said RF generator to provide power at a high level during an initial portion of a sputter deposition and to provide power at a reduced level including zero power in a subsequent portion of said sputter deposition;    a second semiconductor fabrication chamber; and    said second chamber having a second target of a second target material which includes is a material selected from the group of aluminum and copper, for forming a layer on said underlayer.