Abstract:
A system and method for improved thin film deposition is described. One embodiment includes a perimeter mask for thin film deposition, the perimeter mask comprising an at least one mask surface, the at least one mask surface comprising a mask edge, wherein the mask edge is configured to be positioned proximate to a deposition surface; and wherein the at least one mask surface undercuts away from the mask edge. In various embodiments, the perimeter mask may comprise a bezel shape, a parabolic-curve shape, or a segmented curve shape. In some embodiments, the perimeter mask may partially surround a deposition source, such as a heated-pocket deposition source, a PECVD deposition source, or a sputter deposition source. The perimeter mask can assist in achieving more uniform layers of deposition material and improve processing by containing deposition material and reducing cleaning time. In addition, the perimeter mask itself may be heated in order to prevent deposition on the mask itself and further reduce off-time required for cleaning.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to systems and methods for depositing thin films on a substrate. 
       BACKGROUND OF THE INVENTION 
       [0002]    The use of thin film coated substrates is ubiquitous in today&#39;s society. For example, thin film deposition is used for numerous aspects of consumer electronics (from integrated circuit fabrication to cell phone, computer and television display coatings), optics (e.g., coating glass), microparticle fabrication, photovoltaic fabrication, and packaging (e.g., aluminum coating on plastic for potato chip bags). In general, thin film deposition can be characterized as the deposition of a thin film, or thin layer, of material onto a substrate. Here substrate can refer to both the base material onto which the thin film is being deposited and any previously deposited layers. Thin film deposition can be split into chemical deposition and physical deposition processes. 
         [0003]    Taking the production of solar modules or photovoltaic modules as an example, this is an area where the quality of the thin films and the expense and efficiency of producing the photovoltaic modules with the thin films are all significant in producing a commercially viable product. Numerous methods have been used for thin film deposition in photovoltaic module production, such as chemical vapor deposition (CVD) processes, including plasma-enhanced chemical vapor deposition (PECVD), and physical vapor deposition processes, including sputter deposition and evaporative deposition. While there has been significant development and improvement of thin film deposition processes for photovoltaic module production, any process can benefit from improved film uniformity, lower material waste and reduced downtime. 
         [0004]    Taking one of these processes as an example, referring to  FIG. 1  and  FIG. 2  there are sectional views of an exemplary evaporative deposition system  1000  that could be used for thin film deposition during photovoltaic module production. This evaporative deposition system  1000  could be used for a closed space sublimation (CSS) or heated pocket deposition (HPD) process. The evaporative deposition system  1000  shown in  FIG. 1  and  FIG. 2  includes a source  1100  that contains a deposition material  1200 . The source  1100  is disposed within a vacuum chamber (not shown). In  FIG. 1 , a substrate transport  2000  is shown which is configured to carry and position a substrate  3000  over the source  1100 .  FIG. 2 , which is a sectional view orthogonal to that of  FIG. 1 , shows the substrate transport  2000  holding the sides of substrate  3000  carrying the substrate into (or out of) the paper. 
         [0005]    In operation, the source  1100  is heated sufficiently such that the deposition material  1200  reaches a sublimation point. At the sublimation point, particles  1210  of the deposition material  1200  separate and enter a vapor pocket  1300 . Optimally, the particles  1210 , or vapor  1210 , will travel through the vapor pocket  1300  and condense evenly across the surface of substrate  3000  forming a thin film. In order for this to occur, two conditions must occur (1) the energy of a particle  1210  must be low enough so that it does not continue to bounce off the substrate  3000 ; and (2) the surface temperature of the substrate  3000  must be low enough to absorb the latent heat within the particle  1210 . However, numerous factors can negatively impact the quality of the thin film and the efficiency of the process. 
         [0006]    For example, in current evaporative deposition systems  1000  the walls  1110  of the source  1100  are vertical. As a result (a) thermal energy radiated directly to the substrate  3000  heating the edges of the substrate  3000  near the walls  1110 ; and (b) a particle  1210  which impacted the vertical side wall would gain energy. These affects would make it less likely for a particle  1210  to deposit near the edges of the substrate  3000  resulting in the deposition of a non-uniform thin film. 
         [0007]    In addition, it should be recognized that the substrate  3000  can deform under its own weight and/or bow due to thermal gradient through the thickness of the substrate  3000 . Elevated temperatures in certain process conditions can further accentuate these problems. For purposes of illustration, this deformation is shown in exaggerated form in  FIG. 1 . Due to the deformation of the substrate  3000  there needs to be sufficient clearance between the substrate transport  2000  and the source  1100 . However, this clearance creates a gap  1120  between the substrate  3000  and the source  1100  where particles  1210 , or vapor  1210 , can escape and deposit on other portions of the vacuum chamber (not shown). This causes multiple sources of inefficiency, such as material loss, increased costs for cleaning surfaces inside the vacuum chamber, and lost production time when the process is shutdown for cleaning 
         [0008]    Although present devices are functional, they are not sufficiently accurate or otherwise satisfactory. Accordingly, a system and method are needed to address the shortfalls of present technology and to provide other new and innovative features. 
       SUMMARY OF THE INVENTION 
       [0009]    Exemplary embodiments of the present invention that are shown in the drawings are summarized below. These and other embodiments are more fully described in the Detailed Description section. It is to be understood, however, that there is no intention to limit the invention to the forms described in this Summary of the Invention or in the Detailed Description. One skilled in the art can recognize that there are numerous modifications, equivalents and alternative constructions that fall within the spirit and scope of the invention as expressed in the claims. 
         [0010]    The present invention can provide a system and method for movably seal a vapor pocket in a deposition chamber. In one exemplary embodiment, the present invention can include a system for coating a substrate, the system comprising a deposition chamber; a vapor pocket located within the deposition chamber; and an at least one movable seal, wherein the at least one movable seal is configured to form a first seal with a first portion of a substrate, and wherein the first seal is configured to prevent a vapor from leaking past the first portion of the substrate out of the vapor pocket. In some embodiments, the movable seal may comprise a first flange, wherein the first flange forms a wall of the vapor pocket; and a second flange, wherein the second flange is configured to be movably disposed within a first groove of the source block. 
         [0011]    In another embodiment, the present invention can provide a system for coating a substrate, the system comprising a vapor pocket; a substrate; and an actuator, wherein the actuator is configured to movably seal the vapor pocket with the substrate to prevent a vapor from leaking past the substrate out of the vapor pocket. The system may further comprise a first movable insert, wherein the first movable insert is configured to be moved by the actuator to form a first seal with a first portion of the substrate. 
         [0012]    In another embodiment, the present invention may provide a method for coating a substrate, the method comprising providing a substrate in a deposition chamber; positioning the substrate proximate to a vapor pocket, wherein positioning the substrate forms a gap where a vapor in the vapor pocket could leak past a first portion of the substrate; and movably sealing the gap. In one embodiment, movably sealing the gap may comprise moving a first insert, wherein the first insert contacts the first portion of the substrate. In various embodiments, the substrate may be positioned over a source block and the gap may be movably sealed by lowering the substrate, raising the source block, or some combination thereof 
         [0013]    In yet another embodiment, the present invention may comprise a perimeter mask for thin film deposition, the perimeter mask comprising an at least one mask surface, the at least one mask surface comprising a mask edge, wherein the mask edge is configured to be positioned proximate to a deposition surface; and wherein the at least one mask surface undercuts away from the mask edge. In various embodiments, the perimeter mask may comprise a bezel shape, a parabolic-curve shape, or a segmented curve shape. In some embodiments, the perimeter mask may partially surround a deposition source, such as a heated-pocket deposition source, a PECVD deposition source, or a sputter deposition source. 
         [0014]    In yet another embodiment, the present invention may comprise a heated-pocket deposition source comprising a vapor source, wherein the vapor source is configured to heat a deposition material in order to form a deposition vapor; a vapor pocket connected to the vapor source; an aperture, wherein the aperture is configured to allow the deposition vapor to move from the vapor pocket and deposit on a substrate; and an aperture edge, wherein a portion of the aperture edge is formed by an undercut pocket wall. 
         [0015]    As previously stated, the above-described embodiments and implementations are for illustration purposes only. Numerous other embodiments, implementations, and details of the invention are easily recognized by those of skill in the art from the following descriptions and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Various objects and advantages and a more complete understanding of the present invention are apparent and more readily appreciated by reference to the following Detailed Description and to the appended claims when taken in conjunction with the accompanying Drawing wherein: 
           [0017]      FIG. 1  illustrates a sectional view of typical prior art evaporative deposition system. 
           [0018]      FIG. 2  illustrates an orthogonal sectional view of the evaporative deposition system in  FIG. 1 . 
           [0019]      FIGS. 3A and 3B  illustrates an embodiment of an evaporative deposition system with actuators for movably sealing the system. 
           [0020]      FIG. 4  illustrates an embodiment of a movable insert that can be used to form a seal with a portion of a substrate. 
           [0021]      FIG. 5  illustrates an embodiment of a movable insert that can be used to form a seal with a portion of a substrate. 
           [0022]      FIG. 6  illustrates an exterior side view of an evaporative deposition system that can be used consistent with the present invention. 
           [0023]      FIG. 7  illustrates an exterior top view of an evaporative deposition system that can be used consistent with the present invention. 
           [0024]      FIG. 8  illustrates a sectional view of the evaporative deposition system in  FIGS. 6-7  that can be used consistent with the present invention. 
           [0025]      FIG. 9A  illustrates an isometric view of an evaporative deposition system that can be used consistent with the present invention. 
           [0026]      FIG. 9B  illustrates an enlarged view of one end of the evaporative deposition system in  FIG. 9A . 
           [0027]      FIG. 10  illustrates an isometric view of an evaporative deposition system that can be used consistent with the present invention. 
           [0028]      FIG. 11  illustrates a sectional view of a prior art evaporative deposition system and an exemplary profile of a thin film deposited by such a system. 
           [0029]      FIG. 12  illustrates a sectional view of an evaporative deposition system consistent with the present invention and an exemplary profile of a thin film deposited by such a system 
           [0030]      FIG. 13  illustrates exemplary undercut perimeter edge shapes that can be used consistent with the present invention. 
           [0031]      FIG. 14  illustrates a PECVD deposition system with an undercut perimeter edge consistent with the present invention. 
           [0032]      FIG. 15  illustrates a sputtering deposition system with an undercut perimeter edge consistent with the present invention. 
           [0033]      FIG. 16  illustrates an embodiment of an evaporative deposition system consistent with the present invention which includes a vapor diffuser. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Referring now to the drawings, where like or similar elements are designated with identical reference numerals throughout the several views, and referring in particular to  FIG. 3 , it illustrates a cross section of an evaporative deposition system  1000  consistent with an embodiment of the present invention. As shown in  FIG. 3 , the evaporative deposition system  1000  comprises a source  1100 , a substrate transport  2000  for moving and positioning a substrate  3000  over a vapor pocket  1300 , and an actuator  4000  for movably sealing the vapor pocket  1300 . In  FIG. 3  the source  1100  is a box or cuboid configured to hold and heat a deposition material  1200 . The source  1100  forms a vapor pocket  1300  with the substrate  3000  where particles  1210 , or a vapor  1210 , from the deposition material  1200  escape during sublimation and can condense on the substrate  3000  to form a film. The source  1100  in  FIG. 3  is exemplary only and those of skill in the art will readily be aware of alternative shapes and designs that could be used consistent with the present invention. For example, in an alternative embodiment the source  1100  could have separate chambers or pockets in its base for storing and heating the deposition material  1200  (rather than having a flat base as shown in  FIG. 3 ). 
         [0035]    The actuator  4000  in  FIG. 3  is configured to raise or lower the source  1100 . For example, in  FIG. 3A , the actuator  4000  is in an open, or lowered, position in order to allow the substrate transport  2000  to carry the substrate  3000  over the vapor pocket  1300  while allowing clearance for the substrate  3000 , including any deformation of the substrate  3000 . As shown in  FIG. 3B , once the substrate is in position over the vapor pocket  1300  the actuator  4000  can movably seal the vapor pocket  1300  by raising the source  1100  so that the top of the walls of the source  1100  are proximate to, up to and including contacting, the substrate  3000 . It is not required that the walls  1110  of the source  1100  necessarily contact the substrate  3000  in order to seal the vapor pocket  1300 . Instead, the actuator  4000  movably seals the vapor pocket  1300  by moving the source  1100  sufficiently proximate to the substrate  3000  in order to prevent particles  1210  from escaping between the substrate  3000  and the source  1100 . 
         [0036]    While the substrate  3000  is in a horizontal position in  FIG. 3 , nothing in the present invention limits the application of this invention to such an embodiment. Those of ordinary skill in the art will understand how to modify and adapt the present invention to other substrate  3000  and source  1100  configurations. 
         [0037]    In some embodiments of the present invention, an insulator (not shown) can be used between the source  1100  and the substrate  3000 . The source  1100  is typically maintained at an elevated temperate, commonly ranging from 200-700° C., in order to heat the deposition material  1200 . Moreover, the walls of the source  1100  are also maintained at an elevated temperature in order to prevent deposition on the walls. Because the substrate  3000  must be maintained at a lower temperature to promote particle  1210  condensation on the substrate  3000 , it can be beneficial to reduce thermal transfer between the substrate  3000  and the source  1100 . Reducing thermal transfer between the substrate  3000  and the source  1100  promotes film growth uniformity by reducing temperature differences across the substrate  3000 . Moreover, in some embodiments the material composition of the substrate  3000  may require insulation to prevent a high temperature source  1100  from negatively impacting the substrate structure due to contact. An insulator (not shown) could be used to accomplish these and other functions. 
         [0038]    In some embodiments, such as is shown in  FIG. 3 , the actuator  4000  could comprise hydraulic lifts configured to raise and lower the source  1100 . In another embodiment, an actuator can be configured to raise and lower a substrate transport  2000  for transport and sealing. Numerous options exist depending on the type of substrate transport being used. For example, in one embodiment the substrate transport  2000  may comprise a track system with belts which guide the substrate  3000  through the device. These belts may be supported on rails that can be raised and lowered for transport and sealing. Those of skill in the art will be readily aware of alternative design options. It may be necessary or beneficial to use an insulator (not shown) between the source  1100  and the actuator  4000 . 
         [0039]      FIG. 4  shows another embodiment of the present invention, wherein a movable seal or movable insert  5000  is configured to form a seal with the substrate  3000 . Given the weight of the source  1100 , it may be preferred in some instances to move a relatively small insert  5000  rather than the entire source  1100 . It is noted that it in some embodiments it may be preferred to use both an actuator  4000  to move the source  1100  and the movable inserts  5000  described here to seal against the substrate  3000 . It is also noted that in some embodiments the substrate transport  2000  can be configured to move the substrate  3000  in order to form the seal with the source  1100 . 
         [0040]    The actuator  4000  in  FIG. 4  can be used lower (open) or raise (close) the movable insert  5000 . The movable insert  5000  in  FIG. 4  comprises a flange  5100  used to block particles from entering the open space  5200  formed between the movable insert  5000  and the source  1100  when the movable insert  5000  is in a closed (or sealed) position. The actuator  4000  may be attached to, or separated from the source  1100 . Depending on the construction of the actuator  4000 , thermal concerns may encourage the use of insulation between the source  1100  and the actuator  4000 . 
         [0041]    The view shown in  FIG. 4  is a sectional view of the movable insert  5000 . In one embodiment, the movable insert  5000  could extend the width of substrate  3000  between the portions of the substrate transport  2000  which are holding the substrate  3000 . In another embodiment, multiple movable inserts  5000  could be used to extend along that length. The movable insert  5000  forms a seal with a portion of the substrate  3000  and prevents particles from escaping past that portion. In order to prevent any particles or vapor from escaping the vapor pocket  1300  the perimeter of the substrate  3000  must be sealed. Taking a rectangular substrate as an example, movable inserts  5000  can be used to seal one side or multiple sides of the rectangular substrate. In one embodiment, the substrate transport  2000  can be configured to fit against, or form a seal with, the source  1100  on two sides of the rectangular substrate. If the rectangular substrate were deformed, the deformation will be more pronounced closer to the middle of the rectangular substrate than the edges. Movable inserts  5000  on the remaining two sides of the vapor pocket  1300  could be configured to lower sufficiently to allow the substrate  3000  to move over the vapor pocket  1300  and then rise in order to form a seal with the remaining two edges of the rectangular substrate, forming a seal around the vapor pocket  1300 . 
         [0042]    A movable insert  5000  may also be configured such that the shape of the upper surface of the movable insert  5000 , where the movable insert  5000  forms a seal with the substrate  3000 , more closely matches the shape of the substrate  3000 . For example, if the portion of the substrate  3000  that forms the seal with the movable insert  5000  is non-linear, such as because of deformation due to process conditions or because the substrate is intentionally non-linear, the movable insert  5000  can be configured to more closely match against that shape. 
         [0043]    In order to prevent deposition on the movable insert  5000  it may also be configured to promote thermal transfer from the source  1100 . For example, the design and material properties (including the composition of the material and the directional thermal transfer properties of the material) of the movable insert  5000  can all be adapted to promote thermal transfer.  FIG. 5  shows one embodiment of a movable insert  5000  and actuator  4000  design to promote thermal transfer between the source  1100  and the movable insert  5000 . 
         [0044]    As shown in  FIG. 5  the movable insert  5000  may include multiple flanges  5110 ,  5120 ,  5130 ,  5140 . In this case, a first flange  5110  is used as discussed above to help create a barrier between the vapor pocket  1300  and the open space or gaps  5200  formed between the movable insert  5000  and the source  1100 . Guide flanges  5120 ,  5130 ,  5140  are used to help guide movement of the movable insert  5000  and to increase surface area for thermal transfer between the source  1100  and the movable insert  5000 . In the embodiment in  FIG. 5 , one of the guide flanges  5130  is configured to rest against an actuator  4000 , here an actuator cam  4100 , for opening and closing the movable insert  5000 . 
         [0045]    A movable insert  5000  may be comprised of a material that both promotes heat transfer and minimizes thermal expansion. For example, for the embodiment discussed relative to  FIG. 5  the flanges  5100  of the movable insert  5000  must be configured to fit closely with source  1100  in order to promote heat transfer and prevent particles from entering between gaps. But the flanges  5100  must also have sufficient tolerance that any expansion due to elevated temperatures will not cause the flanges  5100  of movable insert  5000  to become lodged in the source  1100 . Possible materials include graphite, extruded graphite, isomolded graphite, titanium, thermally conductive ceramics and tungsten. Design considerations, operational conditions and cost are all important factors as those skilled in the art select a proper material. 
         [0046]    The actuator cam  4100  in  FIG. 5  is configured such that it can raise or lower the movable insert  5000  through rotation. In this embodiment, the actuator cam  4100  is disposed within a conduit  1130  in source  1100 . The size of the conduit  1130  may be selected to help reduce thermal transfer between the source  1100  and the actuator cam  4100 . In addition, the material selected for the actuator cam  4100  should be able to withstand repeated operations and operate under the thermal conditions. For example, stainless steels or ceramics may be potential materials for the cam  4100 . 
         [0047]    Now referring to  FIGS. 6-8  there is an embodiment of an evaporative deposition system  1000  consistent with the present invention.  FIGS. 6-7  show an exterior view of the evaporative deposition system  1000  with source  1100 , substrate transport  2000 , and the rotary flex cable  4110  for the actuator cam  4100 . One advantage of the actuator cam  4100  is that it allows for a thin rotary flex cable  4110  to be used. Given the complexity of deposition systems, and the operation conditions, it is advantageous to be able to minimize the size and number of parts that need to be close to the source  1100 . 
         [0048]    The top view in  FIG. 7  is shown looking down on substrate  3000 , substrate transport  2000 , source  1100 , rotary flex cable  4110 , and movable insert  5000 . Sectional view A-A, shown in  FIG. 8  depicts an embodiment of a movable insert  5000  consistent with the present invention. In this embodiment an undercut flange  5150  serves as a wall for vapor pocket  1300 . As shown, the undercut flange  5150  is undercut—that is, the surface of the undercut flange  5150  which faces the vapor pocket slants away from where the movable insert  5000  forms a seal with substrate  3000 . The benefits of an undercut design are discussed in greater detail below. In addition to being undercut, the undercut flange  5150  is also configured such that it extends into a pocket  1140  of source  1100 . Extending the length of the innermost flange—here undercut flange  5150 —protects against any deposition material getting into gaps  5200  between movable insert  5000  and source  1100 . As shown in  FIG. 8  the undercut flange  5150  has sufficient length that when the movable insert  5000  is in a raised or sealed position the undercut flange  5150  still protrudes into the source  1100 . 
         [0049]      FIGS. 9A ,  9 B and  10  show further isometric views of an embodiment consistent with the present invention. Referring first to  FIG. 9A , it shows a cut way view of an exemplary evaporative deposition system  1000 . In this example, two movable inserts  5000  are used at each end of the source  1100  in order to form seals with substrate  3000 .  FIG. 9B  shows an enlarged view of one movable insert  5000 . As shown, the movable insert  5000  has four flanges  5110 ,  5120 ,  5130 ,  5140  for promoting heat transfer, guiding motion, and protecting against deposition material getting into gaps between the movable insert  5000  and source  1100 . 
         [0050]      FIG. 10  further displays the actuator  4000  used for lowering and raising the movable insert  5000 . As shown, the embodiment in  FIG. 10  employs an actuator cam  4100  with multiple, separate, points of contact  4200  being used to act against one of the flanges  5100  on the movable insert  5000 . Reducing the contact surface area between the actuator  4000  and the movable insert  5000  can help in reducing thermal transfer. However, in other embodiment the point of contact could be extended along the entire edge of the flange  5100 . Many design options will be readily understood by a person skilled in the art. 
         [0051]    Now referring to  FIGS. 11 and 12  illustrated are exemplary thin films deposited in an evaporative deposition system  1000  with straight walls  1110  ( FIG. 11 ) and an evaporative deposition system  1000  with an undercut perimeter mask  6000  ( FIG. 12 ). In  FIG. 11  the straight walls on the evaporative deposition system  1000  (a) radiate thermal energy on to the substrate  3000  heating the edges of the substrate  3000  near the walls; and (b) reflect off particles  1210  which impact the vertical side wall, adding energy to these particles  1210  and allowing the particles  1210  to reflect toward the substrate  3000 . As a result, it less likely for a particle  1210  to deposit near the edges of the substrate  3000 , and a greater number of particles are directed toward the center of the substrate resulting in a non-uniform thin film  1220 . In  FIG. 12 , which illustrates an embodiment consistent with the present invention, the walls are undercut in order to both (a) reduce the thermal energy radiated from the walls onto the substrate  3000 ; and (b) redirect impinging particles back toward the bottom of the source  1100  (rather than allowing the particles  1210  to bounce toward the substrate  3000 ). This results in a more uniform thin film  1230 . 
         [0052]    As shown in  FIG. 12 , the undercut mask  6000  includes a mask surface  6100  which undercuts away from the substrate  3000 . The mask surface  6100  includes a mask edge  6110  which is configured to be proximate to, up to an including touching, the surface of the substrate  3000 . In  FIG. 12  the mask edge  6110  is at the tip of a bezel formed by the mask surface  6100  and a portion of the undercut mask  6000  that contacts the substrate  3000 . This is exemplary only. It should be understood that the mask edge  6110  need only be a portion of the mask surface  6100  which is proximate to the substrate  3000 . Those of skill in the art will readily be aware for configurations consistent with the present invention. 
         [0053]    The undercut shape shown in  FIG. 12  is exemplary only. Further examples of undercut shapes include curves (e.g.,  FIG. 13A  and  FIG. 13B ), such as a parabolic curve (e.g.,  FIG. 13B ), or straight-line arcs (e.g.,  FIG. 13C ). Those of skill in the art will be readily aware of other shapes based on the present invention. Similarly, for  FIG. 12  the angle  6200  of the undercut can be changed based on process factors, manufacturing issues, or other conditions. For example, exemplary angles  6200  could include angles between 15 degrees and 75 degrees, wherein the angle  6200  is measured between (a) a perpendicular vector to the deposition surface and (b) the surface of the undercut wall. It is further notable that the shape of the undercut in an undercut mask  6000  does not need to be uniform. For example, for a vertical or slanted application of an undercut mask the undercut shape near the top of the mask  6000  may be different than the undercut shape near the bottom of the mask.  FIG. 13D  shows a slanted embodiment of an undercut mask  6000  wherein the upper portion of the mask  6000  comprises a different shape than the lower portion  6000 . 
         [0054]    Use of an undercut perimeter mask is not limited to an evaporative deposition system. An undercut perimeter mask may provide benefits for other types of thin film deposition systems, such as PECVD systems or sputtering systems.  FIG. 14  shows a sectional view of an undercut perimeter mask  6000  for use in a PECVD system  7000 . In this embodiment, the undercut perimeter mask  6000  is configured to be proximate to a substrate  3000 . The substrate  3000  may be on a substrate transport system  2000 , such as a track system, or on a substrate stand (e.g., see substrate stand  2200  in  FIG. 15 ). In some embodiments it may be preferential for the undercut perimeter mask  6000  to be lowered, or the substrate  3000  raised, in order to create a seal between the undercut mask  6000  and the substrate  3000 . In application, the undercut mask  6000  will be disposed within a vacuum chamber (not shown). In some applications, the undercut perimeter mask  6000  can be integrated with the walls of the vacuum chamber. 
         [0055]    For the PECVD system  7000  in  FIG. 14 , a linear discharge tube  7100 , including inner conductor  7110 , is configured to provide sufficient power to ignite a support gas  7200  to form a plasma  7300 . The plasma  7300  then provides radicals which disassociate feedstock gas(es)  7400  into new deposition material which then deposits on the substrate  3000 . A waste gas removal system (now shown) can be integrated into the undercut perimeter mask or separately configured. By partially surrounding the linear discharge tube  7100  and feedstock gas  7400  the present invention can increase material use efficiency, reduce deposition on other surfaces inside the vacuum chamber (reducing off-time for cleaning) and achieve more uniform surfaces. 
         [0056]    In order to prevent deposition on the surfaces of the undercut perimeter mask  6000 , the mask may be configured to operate at an elevated temperature. For example, in one embodiment a mask  6000  can be configured with a heating element (not shown) that provides sufficient heat to the surfaces of the mask  6000  to reduce or prevent deposition on those surfaces. Based on the elevated temperature of the mask  6000 , the mask may include an insulator (not shown) which is positioned to contact the surface of the substrate  3000 —protecting the substrate from contact heating. 
         [0057]    In another embodiment, the undercut perimeter mask  6000  can be used within a sputter deposition system  8000 .  FIG. 15  shows an embodiment of the present invention where an undercut perimeter mask  6000  is used with a planar magnetron  8100 , including planar cathode and planar target. Those of skill in the art will understand modifications that may be made for other sputtering systems such as a rotatable magnetron system. In  FIG. 15  the sputtering deposition system  8000  includes a substrate stand  2200  which is configured to raise or lower a substrate  3000  such that the substrate is proximate to, up to and including touching, the undercut perimeter mask  6000 . This allows for a seal between the substrate  3000  and the undercut perimeter mask  6000 . As discussed above, the undercut perimeter mask  6000  can be configured to operate at an elevated temperature. Accordingly, in some embodiments an insulator (not shown) may be included to reduce contact heating between the undercut perimeter mask  6000  and the substrate  3000 . 
         [0058]    It should be further noted that the shape of the mask  6000 , as it contacts the substrate  3000 , can vary based on application. While the figures above show sectional views, this sectional view could be the side view of a rectangular undercut perimeter mask, a circular undercut perimeter mask, an oval undercut perimeter mask, etc. Those of skill in the art will be readily aware of different shapes and configurations consistent with the present disclosure. 
         [0059]    It is also noted that the undercut perimeter mask  6000  can be incorporated and combined with other design features. For example, referring now to  FIG. 16  it shows an embodiment of the present invention which further includes a vapor diffuser  9000 . The vapor diffuser  9000  includes at least one aperture  9100 , and here multiple apertures  9100 , configured to allow particles  1210 , or vapor  1210 , to move from the vapor pocket  1300  and deposit on the substrate  3000 . Those of skill in the art will recognize that the apertures  9100  can be evenly spaced and sized, or the spacing and size of the apertures  9100  may differ depending on the position of each aperture in order to promote more uniform deposition. Moreover, in some embodiments the aperture(s)  9100  size and position may be fixed or it may be variably controlled. In  FIG. 16  the internal wall  9200  of the vapor diffuser  9000  is undercut in order to promote improved thin film deposition. While not shown in  FIG. 16 , it is further notable that this embodiment could be modified to further include a movable insert  5000 . 
         [0060]    Nothing in the present description should suggest that a movable insert  5000  is limited to linear motion, or vertical or horizontal motion in order to movably seal the vapor pocket. In some embodiments, the movable insert  5000  may be designed to follow an angled path, an arced path, or some other path in order to form a seal. For example, if a movable insert  5000  were added to the system shown in  FIG. 16 , it may be designed to move at an angle substantially parallel to the undercut wall  9200  of the vapor diffuser. Similarly, for other systems using an undercut perimeter mask  6000  the shape and motion of the movable insert  5000  may vary to best fit the configuration of the mask  6000  and other design constraints. The present disclosure is exemplary and those of skill in the art will be aware of many design options consistent with the present invention. 
         [0061]    Those skilled in the art can readily recognize that numerous variations and substitutions may be made in the invention, its use and its configuration to achieve substantially the same results as achieved by the embodiments described herein. Accordingly, there is no intention to limit the invention to the disclosed exemplary forms. Many variations, modifications, and alternative constructions fall within the scope and spirit of the disclosed invention as expressed in the claims.