Gas distribution showerhead featuring exhaust apertures

Abstract

Embodiments in accordance with the present invention relate to systems and methods for distributing process gases over the surface of a workpiece. In accordance with one embodiment of the present invention, process gases are flowed from a source to a workpiece surface through a gas distribution showerhead defining a plurality of orifices. The gas distribution showerhead also features a plurality of exhaust orifices for removing material above the wafer surface. The supplemental exhaust afforded by the showerhead exhaust orifices serves to reduce variations in gas velocity attributable to radial flow across the wafer surface, thereby enhancing the uniformity between resulting processing at the wafer edge and center. The ratio of the distribution and exhaust aperture areas may vary or remain constant across the faceplate. Additionally, the size and number of distribution and exhaust apertures may be selected to optimize gas distribution across the semiconductor wafer surface.

1 . An apparatus comprising: 
 walls enclosing a process chamber;    a wafer susceptor positioned within the chamber;    a first exhaust conduit in fluid communication with the chamber; and    a processing gas source in fluid communication with the chamber through a gas distribution showerhead, the gas distribution showerhead comprising; 
 a first channel in fluid communication with the processing gas source and with apertures distributed over a lower surface of the showerhead; and  
 a second channel separate from the first channel and in fluid communication with a second exhaust conduit and with exhaust apertures distributed over the lower surface of the showerhead.  
   
   
   
       2 . The apparatus of  claim 1  wherein the apertures define a first area and the exhaust apertures define a second area.  
   
   
       3 . The apparatus of  claim 2  wherein a ratio of the first area to the second area is substantially constant as a function of radial distance from the center of the gas distribution showerhead.  
   
   
       4 . The apparatus of  claim 2  wherein a ratio of the first area to the second area varies as a function of radial distance from the center of the gas distribution showerhead.  
   
   
       5 . The apparatus of  claim 4  wherein the ratio of the first area to the second area varies linearly as a function of radial distance from the center of the gas distribution showerhead.  
   
   
       6 . The apparatus of  claim 4  wherein the ratio of the first area to the second area varies nonlinearly as a function of radial distance from the center of the gas distribution showerhead.  
   
   
       7 . The apparatus of  claim 4  wherein the ratio of the first area to the second area increases as a function of radial distance from the center of the gas distribution showerhead.  
   
   
       8 . The apparatus of  claim 4  wherein the ratio of the first area to the second area decreases as a function of radial distance from the center of the gas distribution showerhead.  
   
   
       9 . The apparatus of  claim 1  wherein the first exhaust conduit and the second exhaust conduit are in fluid communication with a common foreline.  
   
   
       10 . The apparatus of  claim 9  wherein the plurality of second channels are in fluid communication with the foreline through a first valve and the second exhaust conduit is in fluid communication with the foreline through a second valve.  
   
   
       11 . The apparatus of  claim 1  wherein the first exhaust conduit and the second exhaust conduit are in communication with a common vacuum pump.  
   
   
       12 . The apparatus of  claim 1  wherein the first exhaust conduit and the second exhaust conduit are in communication with separate vacuum pumps.  
   
   
       13 . A method of processing a semiconductor workpiece, the method comprising: 
 flowing a process gas to a semiconductor workpiece through a first plurality of orifices positioned in a gas distribution faceplate; and    removing gas from over the semiconductor workpiece through a chamber exhaust port and a second plurality of orifices positioned in the gas distribution faceplate.    
   
   
       14 . The method of  claim 13  further comprising removing the gas through only the chamber exhaust port prior to flowing the process gas.  
   
   
       15 . The method of  claim 13  further comprising removing the gas through the chamber exhaust port and the second plurality of orifices prior to flowing the process gas.  
   
   
       16 . The method of  claim 13  further comprising initially removing gas through only the chamber exhaust port.  
   
   
       17 . The method of  claim 13  further comprising initially removing gas through only the second plurality of orifices.  
   
   
       18 . The method of  claim 13  wherein the processing chamber is evacuated to a pressure below 20 Torr.  
   
   
       19 . The method of  claim 18  further comprising generating a plasma in the processing chamber prior to flowing the process gas.  
   
   
       20 . The method of  claim 13  further comprising adjusting a rate of removal of gas through the chamber exhaust port during processing.  
   
   
       21 . The method of  claim 13  further comprising adjusting a rate of removal of gas through the second plurality of orifices is adjusted during processing.  
   
   
       22 . A method of processing a semiconductor wafer in a chamber comprising: 
 inserting a semiconductor wafer into the chamber;    evacuating the chamber through a first exhaust port;    introducing at least one process gas through a first set of orifices located on a surface of a showerhead;    removing gas through the first exhaust port; and    removing gas through a plurality of orifices positioned on the surface of the showerhead.    
   
   
       23 . The method of  claim 22  wherein a larger volume of gas is removed through the first exhaust port than is removed through the plurality of orifices.  
   
   
       24 . The method of  claim 22  wherein the chamber is evacuated to a pressure below 20 Torr.  
   
   
       25 . The method of  claim 24  wherein a plasma is generated in the chamber prior to the step of introducing the at least one process gas.  
   
   
       26 . The method of  claim 22  wherein removal of the gas through the first exhaust port and through the plurality of orifices occurs substantially simultaneously.  
   
   
       27 . A method of controlling uniformity of a property of a film deposited on a semiconductor wafer, the method comprising: 
 positioning a wafer in a processing chamber;    introducing gases to the wafer through a first plurality of orifices positioned on a faceplate;    removing the gases through a second plurality of orifices positioned on the faceplate; and    simultaneously removing the gases across a radial exhaust path.    
   
   
       28 . The method of  claim 27  further comprising evacuating the chamber across the radial exhaust path only, prior to flowing the gases.  
   
   
       29 . The method of  claim 27  further comprising evacuating the chamber across the radial exhaust path and the second plurality of orifices prior to flowing the gases.  
   
   
       30 . The method of  claim 27  further comprising initially removing the gases through only the radial exhaust path.  
   
   
       31 . The method of  claim 27  further comprising initially removing the gases through only the second plurality of orifices.  
   
   
       32 . The method of  claim 27  wherein the chamber is evacuated to a pressure below about 20 Torr.  
   
   
       33 . The method of  claim 32  further comprising generating a plasma in the chamber.  
   
   
       34 . The method of  claim 27  wherein a rate of removing gas across the radial exhaust path is adjusted during processing.  
   
   
       35 . The method of  claim 27  wherein a rate of removing gas through the second plurality of orifices is adjusted during processing.