Abstract:
Radio frequency sputtering of high resistance films may be achieved in a cluster tool. Suitable radio frequency isolation may be utilized to enable RF sputtering in an environment which may sensitive to radio frequency energy.

Description:
BACKGROUND  
       [0001]     This invention relates generally to cluster tools for etching and depositing layers on semiconductor wafers.  
         [0002]     A cluster tool is a robot operated tool which includes a plurality of processing chambers for etching and deposition. One or more robots situated centrally relative to the processing chambers are responsible for transferring the wafers from chamber to chamber for processing.  
         [0003]     Commonly, DC sputtering or physical vapor deposition may be implemented in one or more of those chambers. However, such sputtering may not be successful in depositing relatively high resistance films such as chalcogenide materials.  
         [0004]     Thus, there is a need for other ways to deposit physical vapor deposition layers in cluster tools. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is a depiction of a physical vapor deposition chamber in accordance with one embodiment of the present invention;  
         [0006]      FIG. 2  is an enlarged depiction of a portion of the wafer clamp shown in  FIG. 1  in accordance with one embodiment of the present invention; and  
         [0007]      FIG. 3  is a top plan view of a cluster tool in accordance with one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0008]     Referring to  FIG. 1 , a radio frequency (RF) and pulsed direct current (DC) physical vapor deposition (PVD) reactor  10  includes a vacuum chamber  12 . In some embodiments, the vacuum chamber  12  may be grounded and may be formed of metal. A controller  22  controls the power supplies and the mass flow controller  24 . The mass flow controller  24  is responsible for inletting a gas source  26  to the vacuum chamber  12 . The gas source  26  may be a noble gas such as argon.  
         [0009]     Inside the chamber  12  is a grounded shield  14 . The grounded shield  14  is coupled to a wafer clamp  18 . The wafer clamp  18  clamps a wafer (not shown in  FIG. 1 ) on to a pedestal electrode  16 . The electrode  16  may be coupled to a bias potential controlled by the controller  22  in some embodiments.  
         [0010]     Also contained within the vacuum chamber  12  may be a floating shield  84 . Finally, at the top of the chamber  12  is the target  86  which is made of the material to be sputtered on the wafer mounted on the pedestal electrode  16  by the clamps  18 .  
         [0011]     The vacuum within the chamber  12  may be established by cryopump  20  which communicates through a port (not shown) with the chamber  12 . The cryopump  20  maintains a low pressure within the chamber  12 .  
         [0012]     The DC magnetron and radio frequency generator  28  may include a lid cover  27  made of metal, such a aluminum, instead of plastic for better RF shielding to the source. Also, the access plate  80 , for communication connections, may be made of a metal, such as aluminum, to isolate RF power from traveling on communication lines  82 . Finally, a metal plate  89  may be located between the target  86  and the generator  28 . The plate  89  may be formed of aluminum. The plate  89  may enable better source grounding.  
         [0013]     Over the generator  28  may be situated a radio frequency matching circuit  30 . The circuit  30  balances out the radio frequency energy from the generator to the chamber load. The RF matching circuit  30  enables the tuning of the RF power supply to the chamber  12 . The matching circuit  30  is coupled to a radio frequency power supply  32 .  
         [0014]     Referring to  FIG. 2 , the clamp ring  18  includes a pair of downwardly extending arms  38  and  36  which engage, between them the grounded shield  14 . An arm  40  extends transversely thereto and is useful for securing the wafer “W” in position on the pedestal electrode  16 . The arm  40  includes a pair of spaced prongs  41  and  42 . The outer prong  42  is spaced from the innermost edge  43  of the clamp ring  14  by a distance X.  
         [0015]     The clamp ring  18  may have an edge exclusion, indicated by the distance X, of 6 millimeters in some embodiments of the present invention. Such an edge exclusion results in minimal contact with the edge of the wafer W. Also, an increased edge exclusion may protect more surface area to prevent cross contamination in the RF physical vapor deposition environment.  
         [0016]     Referring to  FIG. 3 , a staged-vacuum wafer processing cluster tool  50  may include the reactor  10 . A plurality of other chambers  64  may be situated around a transfer robot chamber  58  which includes a robot therein. The robot contained within the chamber  58  transfers wafers between each of the chambers  64  surrounding it and the chamber  10 . The robot in the chamber  58  may receive wafers from the treatment chamber  62  and may pass wafers outwardly through the cool down treatment chamber  63 . Each of the chambers  64  may be capable of processing the wafer in a different fabrication step. In some cases, each of the chambers may be able to implement one or more of the steps involved in physical vapor deposition.  
         [0017]     The robot buffer chamber  60  also includes a robot. That robot may receive wafers from a load lock chamber  66 , and transfer them to different stations surrounding the robot buffer chamber  60  or to the treatment chamber  62  for transfer to the transfer robot chamber  58 . For example, the chamber  75  may be a pre-clean chamber and the chamber  56  may provide a barrier chemical vapor deposition chamber. The chambers  70  and  72  may be used for degassing and orientation.  
         [0018]     Thus, the robot in the robot buffer chamber  60  grabs a wafer from a load lock chamber  66  and transports the wafer to chambers  70 ,  72  for degassing and orientation. From there the robot in the chamber  60  transfers the wafer to chamber  56  for chemical vapor deposition barrier layer formation in some embodiments of the present invention. Then, the wafer may be transferred to the pre-clean chamber  75 .  
         [0019]     Finally, the wafer may be transferred by the robot in the robot buffer chamber  60  to the treatment chamber  62  for transfer to the robot chamber  58 . From there, various physical vapor deposition (or other steps) may be completed, including the RF or pulsed DC deposition of highly resistive layers in the chamber  10 . Once the processing is done, the robot in the chamber  58  transfers the wafer to the cool down treatment chamber  63 . From there, it can be accessed by the robot buffer chamber  60  robot and transferred out of the cluster tool  50  through a load lock chamber  66 .  
         [0020]     In some embodiments of the present invention, the reactor  10  may RF sputter deposit more highly resistive films, such as chalcogenide films. However, the same chamber may also be utilized for pulsed direct current sputtering as well. Because the RF power source is isolated from the rest of the components in the tool  50 , RF interference with other chambers and with computer cluster tool  50  controllers that control the robots and other RF sensitive elements may be reduced.  
         [0021]     In particular, better RF shielding for the source may be provided, RF power may be isolated from traveling on communication lines, and better source grounding may be achieved. As a result, in some embodiments of the present invention, RF sputtering may be implemented in a cluster tool despite the sensitivity of other components in the cluster tool to the radio frequency power.  
         [0022]     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.