Abstract:
Stepper and/or scanner machines including cleaning devices and methods for cleaning stepper and/or scanner machines are disclosed herein. In one embodiment, a stepper and/or scanner machine includes a housing, an illuminator, a lens, a workpiece support, a cleaning device for removing contaminants from the workpiece support, and a stage carrying the workpiece support. The stage and/or cleaning device is movable to selectively position the workpiece support proximate to the cleaning device. It is emphasized that this Abstract is provided to comply with the rules requiring an abstract. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 C.F.R. § 1.72(b).

Description:
TECHNICAL FIELD  
       [0001]     The present invention is related to stepper and/or scanner machines patterning features on microfeature workpieces. More particularly, the invention is directed to stepper and/or scanner machines including cleaning devices and methods of cleaning stepper and/or scanner machines.  
       BACKGROUND  
       [0002]     Photolithography is one of the primary processes used in the manufacture of microelectronic devices (e.g., dies) on semiconductor wafers or micromechanical devices. In photolithography, a stepper or scanner machine exposes photosensitive materials to pattern the design of the features onto the semiconductor wafer&#39;s surface. A conventional stepper or scanner machine includes a wafer chuck, an illuminator to project light or other radiation, a lens to focus the light, and a reticle. The reticle can be a glass plate with a layer of chrome having a pattern corresponding to the layout of features that are to be constructed on the wafer. In a typical photolithography process, a wafer having a layer of photoresist material is positioned under the lens in the stepper or scanner machine. Next, the illuminator projects a pattern of light onto a portion of the wafer through the corresponding pattern on the reticle and the lens. The light changes the material characteristic of the exposed areas of the photoresist layer to make the exposed areas more or less susceptible to a developing solution. The stepper or scanner machine then positions another portion of the wafer under the reticle and repeats the exposure operation until the entire wafer has been patterned.  
         [0003]     In a subsequent operation, the photoresist layer is typically baked and then developed to create the desired pattern in the resist layer for forming the features. Accordingly, the pattern must be formed in the proper location on the photoresist layer and with very precise dimensions to form very small features of 0.11 μm or less. Errors in photolithography can cause many problems including distorted patterns, misplaced patterns, and other defects. These types of errors can ultimately result in defective microelectronic devices. Moreover, as the feature sizes decrease, slight imperfections or misalignments can result in defects.  
         [0004]     A common cause of errors in photolithography is contamination of the wafer chuck in the stepper or scanner machine. More specifically, particles or other contaminants from other processes, such as chemical-mechanical planarization, vapor depositions, etc., may remain on the wafer as it is loaded into the stepper or scanner machine. These contaminants can be left on the support surface of the wafer chuck, which prevents subsequent wafers from being properly positioned in the wafer chuck. For example,  FIG. 1  is a schematic side cross-sectional view of a wafer  20 , a wafer chuck  50 , and a particle P between the wafer  20  and the wafer chuck  50  (shown exaggerated for illustrative purposes). The wafer chuck  50  includes a plurality of holes  54  coupled to a vacuum pump  58  to hold the wafer  20  against the chuck  50 . The particle P causes the wafer  20  to deform as the vacuum pump  58  draws the water  20  against the chuck  50 . This portion of the wafer  20 , for example, can project outward from the wafer chuck  50  a distance T. As the feature sizes decrease, even a very small deformation of the wafer  20  may be greater than the field depth of the lens such that the lens may not properly focus the pattern of light on the area of the wafer  20  over the particle P. Improper focusing on a region of the wafer causes what is known as a focus spot. If focus spots are detected at a consistent location on several wafers, the wafer chuck is likely contaminated and must be cleaned.  
         [0005]     One problem with existing stepper and scanner machines is that accessing the wafer chuck for cleaning is difficult and the stepper and scanner machines must be recalibrated after each cleaning. More specifically, the cleaning process includes shutting down the stepper or scanner machine, removing one or more panels of the housing, sliding the wafer chuck out of the housing, and cleaning the chuck manually. After the wafer chuck is manually cleaned, the chuck is repositioned in the stepper or scanner machine and the panels are reattached. However, before the stepper or scanner machine can continue processing wafers, it must be recalibrated. Recalibrating stepper and scanner machines is a difficult and time-consuming process that may also require processing target wafers to ensure the stepper or scanner machine is properly registered. The entire process requires significant downtime and consequently causes a significant reduction in throughput. Accordingly, there exists a need to reduce the downtime required to clean the stepper and/or scanner machine. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a schematic side cross-sectional view of a wafer in a contaminated wafer chuck.  
         [0007]      FIG. 2  is a schematic side view of a stepper or scanner machine including a cleaning device in accordance with one embodiment of the invention.  
         [0008]      FIG. 3  is a schematic side cross-sectional view of a portion of the stepper or scanner machine and the cleaning device of  FIG. 2 .  
         [0009]      FIG. 4  is a schematic side cross-sectional view of a portion of a stepper or scanner machine including a cleaning device in accordance with another embodiment of the invention.  
         [0010]      FIG. 5  is a schematic side view of a stepper or scanner machine including a cleaning device in accordance with another embodiment of the invention.  
     
    
     DETAILED DESCRIPTION  
       [heading-0011]     A. Overview  
         [0012]     The present invention is directed toward stepper and/or scanner machines for processing microfeature workpieces and methods of cleaning stepper and/or scanner machines. The term “microfeature workpiece” is used throughout to include substrates in or on which microelectronic devices, micromechanical devices, data storage elements, and other features are fabricated. For example, microfeature workpieces can be semiconductor wafers, glass substrates, insulated substrates, or many other types of substrates. Several specific details of the invention are set forth in the following description and in  FIGS. 2-5  to provide a thorough understanding of certain embodiments of the invention. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that other embodiments of the invention may be practiced without several of the specific features explained in the following description.  
         [0013]     One aspect of the invention is directed to stepper or scanner machines for processing microfeature workpieces. In one embodiment, a stepper or scanner machine includes a housing, an illuminator, a lens, a workpiece support, a cleaning device for removing contaminants from the workpiece support, and a stage carrying the workpiece support. The stage and/or cleaning device is movable to selectively position the workpiece support proximate to the cleaning device. In one aspect of this embodiment, the stepper or scanner machine further includes a positioning device coupled to the cleaning device to move the cleaning device relative to the housing. Alternatively, the cleaning device may be fixed relative to the housing. In another aspect of this embodiment, the stepper or scanner machine further includes a vacuum pump operably coupled to the cleaning device to draw contaminants from the workpiece support. The stepper or scanner machine can also include a cleaning fluid supply operably coupled to the cleaning device to provide a cleaning fluid to the workpiece support.  
         [0014]     In another embodiment, a stepper or scanner machine includes a photolithographic exposure system, a workpiece support, an internal cleaning device, and a stage carrying the workpiece support. The workpiece support has a recess to receive a microfeature workpiece, and the internal cleaning device has a distal portion with a passageway for removing contaminants from the recess of the workpiece support. The stage and/or cleaning device is movable to position the distal portion of the cleaning device at least proximate to the recess of the workpiece support. In one aspect of this embodiment, the distal portion of the cleaning device includes an end effector configured to engage the workpiece support to remove contaminants.  
         [0015]     Another aspect of the invention is directed to methods of cleaning stepper and/or scanner machines. In one embodiment, a method includes positioning a cleaning device at least proximate to a workpiece support without removing a portion of a housing of the stepper or scanner machine. The workpiece support and the cleaning device are disposed within the stepper or scanner machine. The method further includes removing contaminants from the workpiece support with the cleaning device. In one aspect of this embodiment, removing contaminants from the workpiece support can include engaging the workpiece support with an end effector. In another aspect of this embodiment, removing contaminants from the workpiece support includes drawing contaminants from the workpiece support through a passageway in the cleaning device with a vacuum pump. In another aspect of this embodiment, the method further includes providing a cleaning fluid to the workpiece support through a first passageway in the cleaning device and exhausting the cleaning fluid from the workpiece support through a second passageway in the cleaning device.  
         [heading-0016]     B. Embodiments of Stepper and/or Scanner Machines  
         [0017]      FIG. 2  is a schematic side view of a stepper or scanner machine  100  for patterning a photoresist layer on a microfeature workpiece W using a photolithography process in accordance with one embodiment of the invention. The patterns are used in the construction of microelectronic devices, micromechanical devices, and/or other features on the microfeature workpiece W. In the illustrated embodiment, the stepper or scanner machine  100  includes a housing  110  enclosing a workpiece support  150 , a lens  180 , a reticle  190 , and an illuminator  194 . The housing  110  can include a plurality of panels  112  (two of which are identified individually as  112   a - b ) that define an internal chamber  114 . The panels  112  can be removed to access the internal components of the stepper or scanner machine  100 . The temperature, humidity, and other environmental factors in the internal chamber  114  can be precisely controlled to consistently process microfeature workpieces under optimal conditions.  
         [0018]     The workpiece support  150  carries the microfeature workpiece W during the patterning process. The workpiece support  150  can include a recess  152  defined in part by a support surface  153  to receive the microfeature workpiece W. In one embodiment, the workpiece support  150  further includes a plurality of holes  154  in the support surface  153  and a vacuum line  156  connected to the holes  154 . A vacuum pump  158  (shown schematically) can be coupled to the vacuum line  156  to secure the microfeature workpiece W to the workpiece support  150  during patterning. In other embodiments, the workpiece support  150  may not include a recess, and/or the microfeature workpiece W may be secured to the workpiece support  150  by a device other than a vacuum pump.  
         [0019]     The reticle  190  carries the patterns to be used in constructing the microelectronic devices, micromechanical devices, and/or other features on the microfeature workpiece W. For example, the reticle  190  can include a glass plate and a layer of chrome patterned on the plate. The lens  180  focuses the light pattern onto the workpiece W. In operation, the illuminator  194  projects light through the reticle  190  and the lens  180  to change the characteristics of areas of the photoresist layer exposed to the light. The exposed areas become more or less susceptible to removal in a developing solution. The illuminator  194  can project ultraviolet light or other types of electromagnetic radiation. Because the light must strike precise locations of the photoresist layer on the microfeature workpiece W, the stepper or scanner machine  100  can also include a vibration isolation system  120  to reduce alignment and focusing errors from vibration of the components within the housing  110 .  
         [0020]     The stepper or scanner machine  100  further includes a stage  140  to carry the workpiece support  150 , a positioning device  146  operably coupled to the stage  140 , and a controller  147  (shown schematically) to operate the positioning device  146 . The controller  147  can include a computer-readable medium that operates the positioning device  146  to move the stage  140  and properly align the microfeature workpiece W relative to the lens  180 . The microfeature workpiece W is properly aligned before exposure to the light so that the pattern is formed at the desired location on the workpiece W. The positioning device  146  can move the stage  140  along three orthogonal axes such as side to side (X direction), forward and backward (Y direction), and/or upward and downward (Z direction). The positioning device  146  may also rotate the stage  140  about each of the axes. The stepper or scanner machine  100  can also include a transfer mechanism  130  (shown schematically in broken lines) to load the microfeature workpiece W onto the workpiece support  150 .  
         [0021]     The stepper or scanner machine  100  further includes a cleaning device  160  disposed within the housing  110  and a vacuum pump  178  (shown schematically) operably coupled to the cleaning device  160 . In one aspect of the illustrated embodiment, the cleaning device  160  removes contaminants from the workpiece support  150  so that the microfeature workpiece W can be properly positioned on the support  150 . As described above, the incoming workpieces can deposit residual contaminants, such as small particles, on the workpiece support  150 . The cleaning device  160  of the illustrated embodiment automatically removes contaminants from the workpiece support  150  without manual ingress into the chamber  114 . The cleaning device  160  can accordingly prevent focus spots on the microfeature workpiece W as described below with reference to  FIG. 3  without the downtime normally associated with manually cleaning the workpiece support  150 .  
         [0022]     In one aspect of the embodiment, the cleaning device  160  is attached at a fixed position within the housing  110 . Accordingly, the controller  147  moves the stage  140  to position a portion of the cleaning device  160  in the recess  152  to remove contaminants from the workpiece support  150 . In other embodiments, such as the embodiment described below with reference to  FIG. 5 , the cleaning device can be movable within the housing  110  and accordingly move toward the workpiece support  150 . In the illustrated embodiment, the cleaning device  160  is shown positioned proximate to the lens  180 ; however, the cleaning device  160  can be positioned proximate to other components within the housing  110 .  
         [heading-0023]     C. Embodiments of Cleaning Devices  
         [0024]      FIG. 3  is a schematic side cross-sectional view of a portion of the stepper or scanner machine  100  and the cleaning device  160  of  FIG. 2 . In the illustrated embodiment, the cleaning device  160  includes a body  164  having a passageway  166  coupled to the vacuum pump  178  and a distal portion  162  with a lower surface  170 . After the microfeature workpiece W ( FIG. 2 ) is removed from the workpiece support  150 , the stage  140  can move the workpiece support  150  so that the distal portion  162  of the cleaning device  160  is received at least partially in the recess  152 . The surface  153  of the workpiece support  150  can be spaced apart from the lower surface  170  of the distal portion  162  to avoid damaging the cleaning device  160  or the workpiece support  150  during cleaning. Once the distal portion  162  is received in the recess  152 , the stage  140  can move the workpiece support  150  so that the cleaning device  160  sweeps back and forth across the recess  152  to remove the contaminants. As the distal portion  162  moves over the contaminants, the vacuum pump  178  draws the contaminants from the recess  152  through the passageway  166  in a direction D 1 . This cleaning process can occur at periodic intervals, or whenever focus spots are detected on the workpieces.  
         [0025]     In one aspect of this embodiment, the cleaning device  160  includes an end effector  172  (shown in broken lines) attached to the distal portion  162 . The end effector  172  engages the surface  153  of the workpiece support  150  to dislodge contaminants. The end effector  172  can include a brush with bristles, a pad, and/or another device depending on the type of contaminants and the material of the workpiece support  150 . For example, in one embodiment, the end effector  172  can include Teflon® brushes. The end effector  172  can include a plurality of apertures or openings to allow the vacuum pump  178  to draw contaminants through the end effector  172  and into the passageway  166 . In one embodiment, the stage  140  and workpiece support  150  can reciprocate back and forth so that the end effector  172  can scrub and dislodge trapped or attached contaminants. In other embodiments, the cleaning device  160  may not include an end effector.  
         [0026]     One feature of the stepper or scanner machine in the embodiment illustrated in  FIGS. 2 and 3  is that the cleaning device is disposed within the housing. An advantage of this feature is that the side panels of the housing do not need to be removed to access and clean the workpiece support. This is an improvement over prior art stepper and scanner machines that do not have an internal cleaning device. The prior art stepper and scanner machines require significant downtime to remove the workpiece support, manually clean the workpiece support, and recalibrate the stepper or scanner machine. In the illustrated embodiment, the housing panels and workpiece support do not need to be removed, and the cleaning device  160  can be quickly positioned to clean the workpiece holder  150  by merely moving the stage  140  within its normal operating range. This not only reduces the time and effort to clean the workpiece support compared to manual cleaning processes, but it also reduces or eliminates the need to recalibrate the stepper or scanner machine. Consequently, the downtime required to clean the stepper or scanner machine is reduced and the throughput of the stepper or scanner machine is increased compared to conventional manual cleaning processes.  
         [0027]      FIG. 4  is a schematic side cross-sectional view of a portion of a stepper or scanner machine  200  including a cleaning device  260  in accordance with another embodiment of the invention. The stepper or scanner machine  200  is generally similar to the stepper or scanner machine  100  described above with reference to  FIGS. 2 and 3 . For example, the stepper or scanner machine  200  includes a stage  140 , a workpiece support  150 , and a cleaning device  260 . The cleaning device  260  includes a body  264  having a first passageway  266   a , a second passageway  266   b , and a distal portion  262 . In the illustrated embodiment, the first and second passageways  266   a - b  are configured in a concentric arrangement with the first passageway  266   a  surrounding the second passageway  266   b ; however, in other embodiments, the passageways can have other configurations.  
         [0028]     The stepper or scanner machine  200  can further include a cleaning fluid supply  279  coupled to the first passageway  266   a  to provide a cleaning fluid to the surface  153  of the recess  152  for removing contaminants. The cleaning fluid can include deionized water, acetone, etchants, or any other suitable fluid to remove contaminants from the recess  152 . The stepper or scanner machine  200  can further include a vacuum pump  178  coupled to the second passageway  266   b  to remove the cleaning fluid and the contaminants from the surface  153  of the recess  152 . The cleaning fluid accordingly flows in a direction D 2  through the first passageway  266   a  to the recess  152  and is exhausted in a direction D 3  through the second passageway  266   b . The cleaning device  260  can also include an end effector  272  (shown in broken lines) similar to the end effector  172  described above with reference to  FIG. 3 . In other embodiments, the cleaning device can have other configurations.  
         [heading-0029]     D. Additional Embodiments of Stepper and/or Scanner Machines  
         [0030]      FIG. 5  is a schematic side view of a stepper or scanner machine  300  for processing microfeature workpieces in accordance with another embodiment of the invention. The stepper or scanner machine  300  can be generally similar to the stepper or scanner machine  100  described above with reference to  FIGS. 2 and 3 . For example, the stepper or scanner machine  300  includes a housing  110  enclosing a stage  140 , a workpiece support  150 , a lens  180 , a reticle  190 , and an illuminator  194 . The stepper or scanner machine  300  further includes a controller  147 , a cleaning device  160  and a positioning device  361  operably coupled to the controller  147  and the cleaning device  160 . The controller  147  can operate the positioning device  361  to move the cleaning device  160  along the X, Y, and/or Z axes to position the distal portion  162  of the cleaning device  160  in the recess  152  of the workpiece support  150 . Moreover, the controller  147  can operate the positioning device  361  to sweep the cleaning device  160  back and forth across the recess  152  to remove contaminants from the workpiece support  150  in a cleaning cycle. Accordingly, after the transfer mechanism  130  removes the microfeature workpiece from the workpiece support  150 , the stage  140  moves the workpiece support  150  along the X axis toward the cleaning device  160 . Once the stage  140  has moved the workpiece support  150  proximate to the cleaning device  160 , the positioning device  361  moves the cleaning device  160  to remove contaminants from the recess  152 . In other embodiments, the positioning device may not move the cleaning device along the X, Y, and Z axes. For example, the positioning device may only move the cleaning device along the Z axis.  
         [0031]     From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.