Abstract:
In some embodiments, methods and systems are provided for improved handling of lithography masks including loading a mask via a first load port from a first carrier; inverting the mask using a first contact pad; cleaning the mask; inverting the mask using a second contact pad; and unloading the mask via a second load port into a second carrier. Numerous other aspects are provided.

Description:
[0001]    The present application claims priority to commonly owned, co-pending U.S. Provisional Patent Application 61/884,048, filed on Sep. 28, 2013, and entitled “APPARATUS AND METHODS FOR A MASK INVERTER,” (Attorney Docket No. 20470-02/L), and commonly owned, co-pending U.S. Provisional Patent Application 61/884,049, also filed on Sep. 28, 2013, and entitled “METHODS AND SYSTEMS FOR IMPROVED MASK PROCESSING,” (Attorney Docket No. 20470/L), which are both hereby incorporated herein by reference in their entirety for all purposes. 
     
    
     FIELD 
       [0002]    The present application relates to processing masks, and more specifically to methods and systems for improved handling of masks. 
       BACKGROUND 
       [0003]    Particle contamination can be a significant problem in semiconductor manufacturing. A photomask is typically protected from contaminating particles by a pellicle, a thin transparent film stretched over a frame that is glued over one side of the photomask. The pellicle is far enough away from the mask patterns so that moderate-to-small sized particles that land on the pellicle will be too far out of focus to print. Although they are designed to keep particles away, pellicles become a part of the imaging system and their optical properties effect the lithography and are taken into account. 
         [0004]    Conventionally, a pellicle can be used to protect and prevent contamination of the patterned side of ultraviolet (e.g., using 193 nm argon fluorine exciplex lasers) optical lithography masks. However, extreme ultraviolet (EUV) lithography does not allow the use of a pellicle due to the optical effects of the pellicle. However, if the bare mask is not handled properly, there is a risk of contamination. 
         [0005]    Thus, EUV masks (without the protection of a pellicle) are typically only handled in a vacuum. For example, a mask carrier with a nested inner carrier that conforms to the SEMI E152 standard provides double isolation of the bare mask for contamination control, with the assumption that the inner carrier will only be opened in a vacuum. However, an inner carrier opener in a vacuum presents significant cost and complexity. Thus, what is needed are methods and systems that facilitate mask handling without requiring nested carriers and vacuum isolation. 
       SUMMARY 
       [0006]    In some embodiments, the invention provides a method of handling a mask. The method includes loading a mask via a first load port from a first carrier; inverting the mask using a first contact pad; cleaning the mask; inverting the mask using a second contact pad; and unloading the mask via a second load port into a second carrier. 
         [0007]    In other embodiments, the invention provides an alternative method of handling a mask. The alternative method includes loading a mask via a load port from a first carrier; replacing the first carrier with a second carrier at the load port; inverting the mask using a first contact pad; cleaning the mask; inverting the mask using a second contact pad; and unloading the mask via the load port into the second carrier. 
         [0008]    In yet other embodiments, the invention provides a system for handling masks. The system includes a processor; and a memory coupled to the processor and storing program instructions to load a mask via a first load port from a first carrier; invert the mask using a first contact pad; clean the mask; invert the mask using a second contact pad; and unload the mask via a second load port into a second carrier. 
         [0009]    Numerous other aspects are provided in accordance with these and other aspects of the invention. Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic depiction of a first example system for improved mask processing according to some embodiments provided herein. 
           [0011]      FIG. 2  is a schematic depiction of a second example system for improved mask processing according to some embodiments provided herein. 
           [0012]      FIG. 3  is a flow chart depicting a first example method for improved mask processing according to some embodiments provided herein. 
           [0013]      FIG. 4  is a flow chart depicting a second example method for improved mask processing according to some embodiments provided herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    In some embodiments of the present invention, methods and systems are provided for minimizing or reducing the risk of contamination while handling bare EUV masks, particularly at atmospheric conditions. The methods include using a dedicated set of contact pads and end effectors when handling “uncleaned” (e.g., versus post-cleaned) masks within a wet clean tool to prevent re-contamination after cleaning and using a second set of dedicated contact pads and end effectors for handling masks that have been cleaned. Thus, cleaned masks are not handled with contact pads or end effectors that have previously handled masks before the masks were cleaned and masks that have not yet been cleaned are not handled with contact pads or end effectors dedicated to only handling masks that have been cleaned. 
         [0015]    In addition, in some embodiments, a dedicated load port is used for unclean masks entering the wet clean tool and a separate dedicated load port is used for post-cleaned masks exiting the wet clean tool. In some embodiments, the same load port is used but different carriers are used for entry and exit. In some embodiments, control software logic is also provided that returns uncleaned masks back to the “unclean” incoming load port and post-cleaned masks to the “clean” outgoing load port in the event of a system fault within the wet clean tool. These and other embodiments provide advantages both in terms of reduced cost and complexity as well as a reduction of contamination of EUV masks which in turn increases yield and output from electronic device manufacturing facilities. In addition to EUV optical mask handling, the systems and methods provided herein can be applied to handling other masks, reticles, and electric device substrates to reduce particle contamination. 
         [0016]      FIG. 1  is a schematic diagram of a first example system  100  provided in accordance with some embodiments. A first load port  102  is coupled to the factory interface of a mask processing tool such as a mask cleaning tool. The load port  102  is disposed so that an atmospheric dual blade factory interface robot  104  can remove the mask to be cleaned from a carrier placed in the load port  102 . Thus, the carrier is opened into a non-vacuum factory interface. The robot  104  includes two end effectors. The first end effector is dedicated to only handling masks that have not yet been cleaned. The second end effector is dedicated to only handing masks that have already been cleaned. Thus, contamination of a mask that has been cleaned is avoided by not handling the clean mask with an end effector that has handled unclean masks. 
         [0017]    The inventors of the present application have determined that before a mask is cleaned, potentially contaminating particles are transferable from the unclean mask to the end effector when the mask is moved from the load port. Further, these particles can then be transferred again from the end effector to a subsequently handled mask. If the mask has already undergone a cleaning process, the particle transfer back to the mask from the end effector can contaminate the clean mask. Thus, one or more embodiments provided herein avoid this potential for contamination by only handing a clean mask with end effectors that have not handled unclean masks. 
         [0018]    The system  100  further includes a mask inverter  106 . In some embodiments, the mask inverter  106  can be disposed at a load port location as shown in  FIG. 1 . In some embodiments, the mask inverter can be located at any practicable location such as alongside the factory interface or between the tool and the factory interface within the system  100 . The mask inverter  106  includes two different contact pads. The first contact pad is dedicated to only handling and inverting masks that have not yet been cleaned. The second contact pad is dedicated to only handing masks that have already been cleaned. Thus, contamination of a mask that has been cleaned is avoided by not handling the clean mask with a contact pad that has held unclean masks. 
         [0019]    As with end effectors, the inventors of the present application have determined that before a mask is cleaned, potentially contaminating particles are transferable from the unclean mask to the contact pads of the inverter  106  when the mask is held by the inverter  106 . Further, these particles can then be transferred again from the contact pad to a subsequently held mask. If the mask has already undergone a cleaning process, the particle transfer back to the mask from the contact pad can contaminate the clean mask. Thus, one or more embodiments provided herein avoid this potential for contamination by only holding a clean mask with contact pads that have not held unclean masks. 
         [0020]    The system  100  can further include a dry clean tool  108  such as an etch process tool for, e.g., removing oxidation from the mask before the mask under goes wet clean processing. An example of such a tool is the Axiom™ strip chamber manufactured by Applied Materials, Inc. of Santa Clara, Calif. 
         [0021]    In some embodiments, the system  100  can include buffer stations  110 ,  116  within an intermediate module between the factory interface and an atmospheric process module that includes a plurality of mask wet clean chambers  112 . The buffer stations  110 ,  116  provide a location for the factory interface robot  104  and an atmospheric dual blade process robot  114  to facilitate mask handoff. One of the buffer stations  110  is dedicated to holding unclean masks while the other buffer station  116  is dedicated to holding cleaned masks. Thus, contamination of a mask that has been cleaned is avoided by not storing the clean mask on a buffer station that has held unclean masks. 
         [0022]    As with end effectors and contact pads, the inventors of the present application have determined that before a mask is cleaned, potentially contaminating particles are transferable from the mask to a buffer station when the unclean mask is held in the buffer station. Further, these particles can then be transferred again from the buffer station to a subsequently held mask. If the mask has already undergone a cleaning process, the particle transfer back to the mask from the buffer station can contaminate the clean mask. Thus, one or more embodiments provided herein avoid this potential for contamination by only holding a clean mask in a buffer station that has not held unclean masks. 
         [0023]    In some embodiments, the system  100  can include a second load port  118  coupled to the factory interface. The second load port  118  is disposed so that the atmospheric dual blade factory interface robot  104  can load a cleaned mask into a carrier placed in the load port  118 . 
         [0024]    In some embodiments, a second load port is not used and instead, cleaned masks exit the system via the first load port  102 . In such embodiments, a first carrier that brings the unclean mask to the system  100  is replaced with a second carrier to remove the cleaned mask from the system  100 . In other words, after a mask to be cleaned has been removed from the carrier within which the unclean mask arrived, the carrier is removed from the load port  102  and a new carrier that has not stored unclean masks is placed on the load port  102  to receive the clean mask. Therefore, some of the carriers used by the system are dedicated to holding only unclean masks while other carriers are dedicated to holding only cleaned masks. Thus, contamination of a mask that has been cleaned is avoided by not storing the cleaned mask in a carrier that has held unclean masks. 
         [0025]    As with end effectors, contact pads, and buffer stations, the inventors of the present application have determined that before a mask is cleaned, potentially contaminating particles are transferable from the mask to a carrier when the unclean mask is held in the carrier. Further, these particles can then be transferred again from the carrier to a subsequently held mask. If the mask has already undergone a cleaning process, the particle transfer back to the mask from the carrier can contaminate the clean mask. Thus, one or more embodiments provided herein avoid this potential for contamination by only holding a clean mask in a carrier that has not held unclean masks. 
         [0026]    Finally, the system  100  includes a controller  120  (e.g., a programmed processor) adapted to execute instructions to implement the functions and methods described herein. The controller  120  can be implemented as a single processor operatively coupled to each of the components to control their operation or the controller  120  can be implemented as multiple processors, one for each component, in communication with each other and/or with an electronic device manufacturing facility automation system. 
         [0027]      FIG. 2  is a schematic diagram of a second example system  200  provided in accordance with some embodiments. As with the first example system  100 , a first load port  102  is coupled to the factory interface of a mask processing tool such as a mask cleaning tool. The load port  102  is disposed so that an atmospheric dual blade factory interface robot  104  can remove the mask to be cleaned from a carrier placed in the load port  102 . Thus, the carrier is opened into a non-vacuum factory interface. The robot  104  includes two end effectors. The first end effector is dedicated to only handling masks that have not yet been cleaned. The second end effector is dedicated to only handing masks that have already been cleaned. Thus, contamination of a mask that has been cleaned is avoided by not handling the clean mask with an end effector that has handled unclean masks. 
         [0028]    The system  200  further includes two mask inverters  106 ,  202 . In some embodiments, the mask inverters  106 ,  202  can be disposed at load port locations as shown in  FIG. 2 . In some embodiments, the mask inverters can be located at any practicable locations such as alongside the factory interface or between the tool and the factory interface within the system  200 . The mask inverters  106 ,  202  include contact pads for holding the mask when the mask is inverted. One mask inverter  106  is dedicated to only handling and inverting masks that have not yet been cleaned. The second mask inverter  202  is dedicated to only handing masks that have already been cleaned. Thus, contamination of a mask that has been cleaned is avoided by not handling the clean mask with a mask inverter that has held unclean masks. 
         [0029]    As with the first example system  100 , the system  200  can further include a dry clean tool  108  such as an etch process tool for, e.g., removing oxidation from the mask before the mask under goes wet clean processing. An example of such a tool is the Axiom™ strip chamber manufactured by Applied Materials, Inc. of Santa Clara, Calif. 
         [0030]    As with the first example system  100 , in some embodiments, the system  200  can include buffer stations  110 ,  116  within an intermediate module between the factory interface and an atmospheric process module that includes a plurality of mask wet clean chambers  112 . The buffer stations  110 ,  116  provide a location for the factory interface robot  104  and an atmospheric dual blade process robot  114  to facilitate mask handoff. One of the buffer stations  110  is dedicated to holding unclean masks while the other buffer station  116  is dedicated to holding cleaned masks. Thus, contamination of a mask that has been cleaned is avoided by not storing the clean mask on a buffer station that has held unclean masks. 
         [0031]    As with the first example system  100 , in some embodiments, the system  100  can include a second load port (not shown) coupled to the factory interface. The second load port can be disposed so that the atmospheric dual blade factory interface robot  104  can load a cleaned mask into a carrier placed in the second load port. 
         [0032]    As with the first example system  100 , in some embodiments, a second load port is not used and instead, cleaned masks exit the system via the first load port  102 . In such embodiments, a first carrier that brings the unclean mask to the system  100  is replaced with a second carrier to remove the cleaned mask from the system  100 . In other words, after a mask to be cleaned has been removed from the carrier within which the unclean mask arrived, the carrier is removed from the load port  102  and a new carrier that has not stored unclean masks is placed on the load port  102  to receive the clean mask. Therefore, some of the carriers used by the system are dedicated to holding only unclean masks while other carriers are dedicated to holding only cleaned masks. Thus, contamination of a mask that has been cleaned is avoided by not storing the cleaned mask in a carrier that has held unclean masks. 
         [0033]    Finally, as with the first example system  100 , the system  200  includes a controller  120  (e.g., a programmed processor) adapted to execute instructions to implement the functions and methods described herein. The controller  120  can be implemented as a single processor operatively coupled to each of the components to control their operation or the controller  120  can be implemented as multiple processors, one for each component, in communication with each other and/or with an electronic device manufacturing facility automation system. 
         [0034]      FIG. 3  is a flowchart of a first example method  300  provided in accordance with some embodiments. A mask to be cleaned is loaded via a first load port from a first carrier ( 302 ). A first end effector of an atmospheric dual blade factory interface robot can be used. The mask is then loaded onto a first contact pad of an inverter with two sets of contact pads and then inverted ( 304 ). In some embodiments, the mask can be loaded into a first inverter with a single contact pad. 
         [0035]    The mask is then cleaned ( 306 ). Cleaning the mask can include putting the mask through a dry clean process chamber and/or a wet clean process chamber. End effectors and buffer stations used to handle the mask can include end effectors and buffer stations dedicated to handling the mask before the cleaning process and separate end effectors and buffer stations dedicated to handling the mask after the cleaning process. 
         [0036]    After the mask has been cleaned, the mask is transferred to a second contact pad of the inverter and the mask is inverted ( 308 ). In some embodiments, a second inverter is used in place of an inverter with two contact pads. An end effector that has not handled unclean masks is then used to transfer the mask from the inverter to a second carrier in a second load port to unload the mask from the system ( 310 ). 
         [0037]      FIG. 4  is a flowchart of a second example method  400  provided in accordance with some embodiments. A mask to be cleaned is loaded via a first load port from a first carrier ( 402 ). A first end effector of an atmospheric dual blade factory interface robot can be used. After the mask has been loaded, the first carrier is removed from the first load port and replaced with a second carrier. The mask is loaded onto a first contact pad of an inverter with two sets of contact pads and then inverted ( 404 ). In some embodiments, the mask can be loaded into a first inverter with a single contact pad. 
         [0038]    The mask is then cleaned ( 406 ). Cleaning the mask can include putting the mask through a dry clean process chamber and/or a wet clean process chamber. End effectors and buffer stations used to handle the mask can include end effectors and buffer stations dedicated to handling the mask before the cleaning process and separate end effectors and buffer stations dedicated to handling the mask after the cleaning process. 
         [0039]    After the mask has been cleaned, the mask is transferred to a second contact pad of the inverter and the mask is inverted ( 408 ). In some embodiments, a second inverter is used in place of an inverter with two contact pads. An end effector that has not handled unclean masks is then used to transfer the mask from the inverter to the second carrier waiting in the first load port to unload the mask from the system ( 410 ). 
         [0040]    In some embodiments, the above methods  300 ,  400  may include a fault recovery process. For example, at any stage of the methods  300 , 400 , in response to a fault (e.g., an alert message indicating the failure of a component has been detected), the system can transfer a mask to the first or second load port based upon the status of the mask. In other words, if a mask has not undergone a complete cleaning process, the system will return the mask to the first (e.g., in-coming) load port using end effectors and buffer stations that are dedicated to handling unclean masks. Further, if a mask has undergone a complete cleaning process, the system will bring the mask to the second (e.g., out-going) load port using end effectors and buffer stations that are dedicated to handling cleaned masks. In embodiments where only one load port is used, the system can request a carrier that corresponds to the status of the mask. In other words, if the mask has not undergone a complete cleaning process, the system will request a carrier that holds unclean masks to be placed at the load port and if a mask has undergone a complete cleaning process, the system will request a carrier that holds only clean masks to be placed at the load port. 
         [0041]    The foregoing description discloses only example embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. 
         [0042]    Accordingly, while the present invention has been disclosed in connection with example embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.