Abstract:
A method for affecting film growth on a substrate during a deposition process includes steps of: applying a first voltage or current to a first zone of a chuck adapted to hold the substrate in position, the film growth on at least a portion of the substrate proximate the first zone being affected as a function of a level of the first voltage or current; and applying a second voltage or current to a second zone of the chuck, the film growth on at least a portion of the substrate proximate the second zone being affected as a function of a level of the second voltage or current.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of pending U.S. patent application Ser. No. 11/063,788 filed on Feb. 22, 2005, the disclosure of which is incorporated herein by reference in its entirety for all purposes. 
     
    
     BACKGROUND 
       [0002]    A. Technical Field 
         [0003]    The present invention relates generally to the field of semiconductor wafer fabrication, and more particularly, to providing more uniform depositions on semiconductor wafers. 
         [0004]    B. Background of the Invention 
         [0005]    During the manufacturing of semiconductor devices, including integrated circuits or microchips, metal or dielectric films are deposited onto a wafer. These films range from highly conductive metal films, such as aluminum, tungsten, and copper, to dielectric films, such as silicon-dioxide, silicon nitride, and various other films having low dielectric (low k) values. The metal and dielectric films may be deposited using any of a number of deposition chambers and different processes, such as Chemical Vapor Deposition (CVD) and Plasma Chemical Vapor Deposition (PCVD). 
         [0006]    During a typical process, a solid film (metal or dielectric) is formed on a wafer substrate by the reaction of vapor-phase chemicals or reactants that contain the required constituents. Typically, the reactant gases are introduced into a reaction chamber and are decomposed or reacted at a heated surface to form a thin film. During this process, an electrostatic chuck is used to hold the wafer in position in the deposition chamber. The chuck holds the wafer in position by electro-static forces, which is accomplished by applying a voltage to the entire chuck. 
         [0007]    Due to uneven topography of the wafer, possibly resulting from previous deposition cycles or other manufacturing processes, reactants may grow uneven layers onto the surface of the wafer. Furthermore, the geometric layout of the wafer may create areas of uneven deposition. 
         [0008]    Uneven film deposition may require additional processing to make the wafer layer even. Additional processing creates added costs and waste. Furthermore, additional processes, such as chemical mechanical polishing or planarization, are limited in their ability to correct unevenness of a wafer surface. Thus, uneven film deposition can result in increased costs due to costs of additional processing and loss of yield. 
       SUMMARY OF THE INVENTION 
       [0009]    Thus, an object of the present invention is to provide systems and methods that allow for more uniform growth of films on substrates. 
         [0010]    In an embodiment of the present invention, a chuck for holding a substrate in a deposition chamber comprises at least two electrically distinct zones, wherein voltages or currents may be applied to each of the zones. In an embodiment, a controller provides the ability to control the timing, magnitude, and polarity of the voltage or current applied to each of the zones. The voltage or current applied to one or more zones may affect the growth of a film on a substrate by attracting or repelling reactants to a portion of the substrate. 
         [0011]    An embodiment of the present invention comprises a method for affecting film growth on a substrate during a deposition process. In one embodiment, the method comprises placing a substrate on a chuck, wherein the chuck comprises at least two zones. Each of the zones in the chuck is electrically distinct from each other so that a voltage or current may be applied individually to each zone. A voltage or current is applied to one or more zones to affect the growth of a film on a substrate by attracting or repelling reactants to a portion of the substrate. In an alternate embodiment, the method may further comprise the step of varying the voltage or current applied to at least one of the zones during a deposition process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments. 
           [0013]      FIG. 1  is a top view of a chuck with a plurality of circular electrical zones. 
           [0014]      FIG. 2  illustrates a partial profile of a reaction chamber with reactants present and a wafer placed on an embodiment of a multi-zone chuck. 
           [0015]      FIG. 3  is a top view of a chuck with a plurality of radial electrical zones. 
           [0016]      FIG. 4  is a top view of a chuck with a plurality of parallel electrical zones. 
           [0017]      FIG. 5  is a top view of a chuck with a plurality of electrical zones. 
           [0018]      FIG. 6  is a block diagram of an embodiment of a multi-zone chuck functionally connected to a voltage controller. 
           [0019]      FIG. 7  is a flow chart illustrating an embodiment of a method for creating a wafer by varying the electrical profile of a multi-zone chuck. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    In the following description, for purposes of explanation, specific details are set forth in order to provide an understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these details. Furthermore, one skilled in the art will recognize that embodiments of the present invention, described below, may be performed in a variety of ways and using a variety of mediums, including software, hardware, or firmware, or a combination thereof. Accordingly, the embodiments described below are illustrative of specific embodiments of the invention and are meant to avoid obscuring the invention. 
         [0021]    Reference in the specification to “one embodiment,” “a preferred embodiment,” or “an embodiment” means that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment,” “in an embodiment,” or the like in various places in the specification are not necessarily all referring to the same embodiment. 
         [0022]    Currently, chucks employed in chemical vapor deposition and plasma chemical vapor deposition wafer production processes function to hold the wafer in place during processing. The present invention provides the ability to provide additional functionality by varying electrical zones or regions on the chuck  100 . 
         [0023]      FIG. 1  depicts an embodiment of a multi-zone electrical chuck  100 A. Multi-zone chuck  100 A comprises a plurality of electrically distinct zones or regions  101 . In the embodiment depicted in  FIG. 1 , chuck  100 A is comprised of five electrically distinct zones  101 A- 101 E. Each zone  101 A-E is electrically isolated from each other zone, and each zone  101 A- 101 E is capable of being set to a voltage independent of the voltage applied to each of the other zones. For example, each zone may be divided by an insulating material and a conductor attached to each zone may apply the voltage. It should be noted that although each zone is capable of being set to a voltage level different from the other zones, two or more zones may be set to the same voltage. 
         [0024]    A chuck  100  with the ability to vary the voltage in different zones allows for greater uniformity to be achieved during a CVD or PCVD process. By changing the voltage level at different zones across the chuck, reactants in the process chamber may be attracted or repelled to regions of the wafer to create a desired deposition profile on the wafer. 
         [0025]      FIG. 2  is an illustration of a side view of part of a reaction chamber  200  with an embodiment of a multi-zone electric chuck  100 A holding a wafer substrate  202 . In  FIG. 2 , a reactant gas  203  constituting the chemicals for a film deposition is introduced over wafer  202 . Reactant  203  has a general concentration  205  over the surface of wafer  202 . As illustrated, there is a higher concentration  204  of the reactant over zone  101 B. As discussed with respect to  FIG. 1 , the multi-zone chuck  100 A has the ability to vary the voltages of its different zones. 
         [0026]    Each of zones  101 A- 101 E may be biased to different voltage levels according to a desired profile sought to be achieved during the CVD or PCVD process. For example, if the area above zone  101 B requires more layer growth on wafer  202  than other areas on wafer  202 , zone  101 B may be set to a higher voltage than other zones to attract a higher concentration  204  of reactant  203  to the area above zone  101 B, including attracting more reactants to the surface of the substrate  202  above region  101 B. The voltage level may be set higher or lower than other zones depending on the system configuration, such as the polarity of reactant  203  and whether reactant  203  is to be attracted or repelled from the specified area or portion. 
         [0027]    A desired profile may be determined in a number of ways. In one embodiment, sample wafers may be inspected to determine the profile resulting from the manufacturing process. In another embodiment, the desired profile may be determined given the known wafer geographies and/or previous manufacturing processes. In yet another embodiment, the wafer, itself, may be examined to determine its specific profile. 
         [0028]    One skilled in the art will recognize that the voltages applied to the various zones  101 A- 101 E need not be held static during the entire CVD or PCVD process. Rather, the voltages may be changed during the process to adjust the rates of film growth during the CVD or PCVD process. 
         [0029]      FIG. 3  depicts an alternate embodiment of a multi-zone electric chuck. Chuck  100 B possesses a plurality of zones  301 A- 301 H. Each of the zones  301 A- 301 H may be electrically distinct from each other zone. In the embodiment depicted in  FIG. 3 , zones  301 A- 301 H are pie-shaped sections of chuck  100 B. 
         [0030]      FIG. 4  depicts an alternate embodiment of a multi-zone electric chuck. Chuck  100 C possesses a plurality of parallel or substantially parallel zones  401 A- 401   n . Each of the zones  401 A- 401   n  may be electrically distinct from each other zone. In the embodiment depicted in  FIG. 4 , chuck  100 C may be configured with a number of zones varying from 2 to n. 
         [0031]      FIG. 5  depicts an alternate embodiment of a multi-zone electric chuck. Chuck  100 D possesses a plurality of small zones  501 A- 501   n . Each of zones  501 A- 501   n  may be electrically distinct from each other zone. In the embodiment depicted in  FIG. 5 , chuck  100 D may be configured with a number of zones varying from 2 to n. The small zones  501 A- 501   n  increase the ability to direct reactants to smaller portions on a wafer. It should be understood with this embodiment, as with each of the embodiments, that the different zones  501 A- 501   n  of chuck  100 D may be the same size and shape or may be different in size and/or shape. 
         [0032]      FIG. 6  depicts a block diagram of an embodiment of the present invention comprising a multi-zone chuck  100  functionally connected via connection  602  to a voltage controller  604 . It should be noted that where the specification discusses applying and/or controlling voltages to a zone, this also encompasses applying and/or controlling current flow through a zone. For example, in an embodiment, a voltage is applied to a zone by allowing a current to flow through the zone. One skilled in the art will also recognize that voltage controller  604  may be any of a number of devices or combination of devices known for controlling voltage levels or current flows. Furthermore, voltage controller  604  may be implemented in hardware, firmware, software, or any combination thereof. In an embodiment, voltage controller  604  may be a potentiometer, which is under the control of a user. In an alternate embodiment, voltage controller  604  may be a processor or a computer system that controls the voltage levels/current levels of the different zones on a chuck  100 . A processor or computer system may also be configured to receive wafer profile information prior to or during the CVD or PCVD process. After receiving the profile information, the system may adjust the voltages/currents applied to the zones of chuck  100  to achieve the desired profile during the CVD or PCVD process. 
         [0033]      FIG. 7  depicts a flow chart illustrating an embodiment of a method for controlling the film growth on a wafer by varying the electrical profile of a multi-zone chuck. With the wafer positioned on a chuck with at least two electrically distinct zones, a first voltage is applied  702  to a first zone of the multi-zone chuck. A second voltage is applied  704  to a second zone of the multi-zone chuck. Additional voltages may be applied to other zones on the chuck depending on the configuration of the multi-zone chuck and also depending on the desired profile. It should be noted that these voltages may be applied at the same time or at different times during the CVD or PCVD process. It should also be understood that the discussions within this specification of applying a voltage to a zone can include the application of zero, or no voltage, to a zone. In an embodiment, the voltages applied to a zone or zones may be varied or adjusted  206  during the CVD or PCVD process. 
         [0034]    The above description is included to illustrate embodiments of the present invention and is not meant to limit the scope of the invention. The scope of the invention is to be limited only by the following claims. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the spirit and scope of the present invention.