Abstract:
Techniques for atomic layer deposition (ALD) are disclosed. In one particular exemplary embodiment, the techniques may be realized as a system for ALD comprising a plurality of reactors in a stacked configuration, wherein each reactor comprises a wafer holding portion for holding a target wafer, a gas assembly coupled to the plurality of reactors and configured to provide at least one gas to at least one of the plurality of reactors, and an exhaust assembly coupled to the plurality of reactors and configured to exhaust the at least one gas from the at least one of the plurality of reactors. The gas assembly may further comprise a valve assembly coupled to each of the first gas inlet, the second gas inlet, and the third gas inlet, where the valve assembly is configured to selectively release at least one of the first gas, the second gas, and the third gas.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure relates generally to semiconductor manufacturing and, more particularly, to techniques for atomic layer deposition. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    Modern semiconductor manufacturing has created a need for precision, atomic-level deposition of high quality thin film structures. Responsive to this need, a number of film growth techniques collectively known as “atomic layer deposition” (ALD) or “atomic layer epitaxy” (ALE) have been developed in recent years. ALD technology is capable of depositing uniform and conformal films with atomic layer accuracy. A typical ALD process uses sequential self-limiting surface reactions to achieve control of film growth in a monolayer thickness regime. Due to its excellent potential for low temperature and high conformity/uniformity of a film, ALD has become the technology of choice for advanced applications such as high dielectric constant (high-k) gate oxide, storage capacitor dielectrics, and high aspect ratio fill in microelectronic devices. In fact, ALD technology may be useful for any advanced application that benefits from precise control of thin film structures on the nanometer (nm) or sub-nanometer scales. 
         [0003]    However, conventional ALD techniques may suffer from various deficiencies and have not found widespread adoption in the semiconductor industry. For example, a single wafer ALD process may tend to be slow due to numerous repeated cycles of reactions. This may result in low productivity due to a throughput of only several wafers per hour. 
         [0004]    In a batch ALD process, productivity may appear to be substantially increased since a furnace reactor that accommodates the batch ALD process may support approximately 100 wafers. However, overall productivity remains comparable to that of the single ALD process because cycle time increases due to the large volume of the furnace reactor. In addition, the batch ALD process may not have as much process flexibility or clustering capability when compared to other conventional ALD processes. 
         [0005]    A semi-batch ALD process having a planar reactor may also be used to process a plurality of wafer at the same time. Although there may be some improvement in productivity, such improvement remains minimal. 
         [0006]    In view of the foregoing, it may be understood that there are significant problems and shortcomings associated with current atomic layer deposition (ALD) technologies. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    Techniques for atomic layer deposition (ALD) are disclosed. In one particular exemplary embodiment, the techniques may be realized as a system for atomic layer deposition (ALD) comprising a plurality of reactors in a stacked configuration, wherein each reactor comprises a wafer holding portion for holding a target wafer, a gas assembly coupled to the plurality of reactors and configured to provide at least one gas to at least one of the plurality of reactors, and an exhaust assembly coupled to the plurality of reactors and configured to exhaust the at least one gas from the at least one of the plurality of reactors. 
         [0008]    In accordance with other aspects of this particular exemplary embodiment, the stacked configuration may be a vertically stacked configuration such that the plurality of reactors are stacked on top of one another. 
         [0009]    In accordance with further aspects of this particular exemplary embodiment, the stacked configuration may be a horizontally stacked configuration such that the plurality of reactors are stacked next to one another. 
         [0010]    In accordance with additional aspects of this particular exemplary embodiment, the gas assembly may comprise a first gas inlet configured to provide a first gas to the plurality of reactors, a second gas inlet configured to provide a second gas to the plurality of reactors, and a third gas inlet configured to provide a third gas to the plurality of reactors. 
         [0011]    In accordance with other aspects of this particular exemplary embodiment, the first gas may be a first reactive gas, the second gas may be a second reactive gas, and the third gas is an inert gas. 
         [0012]    In accordance with further aspects of this particular exemplary embodiment, the gas assembly may further comprise a valve assembly coupled to each of the first gas inlet, the second gas inlet, and the third gas inlet, wherein the valve assembly may be configured to selectively release at least one of the first gas, the second gas, and the third gas. 
         [0013]    In accordance with additional aspects of this particular exemplary embodiment, the valve assembly may be in a vertical valve configuration, the valve assembly may further comprise a first set of nozzles configured to selectively release the first gas in a plane substantially parallel to a surface of the target wafer, a second set of nozzles configured to selectively release the second gas in a plane substantially parallel to a surface of the target wafer, and a third set of nozzles configured to selectively release the third gas in a plane substantially parallel to a surface of the target wafer, such that the first set of nozzles, the second set of nozzles, and the third set of nozzles may be stacked on top of each other. 
         [0014]    In accordance with other aspects of this particular exemplary embodiment, the valve assembly may be in a horizontal valve configuration, the valve assembly further comprising a first set of nozzles configured to selectively release the first gas in a plane substantially parallel to a surface of the target wafer, a second set of nozzles configured to selectively release the second gas in a plane substantially parallel to a surface of the target wafer, and a third set of nozzles configured to selectively release the third gas in a plane substantially parallel to a surface of the target wafer, such that the second set of nozzles may be positioned adjacent to the first set of nozzles, and the third set of nozzles may be positioned adjacent to the second set of nozzles. 
         [0015]    In accordance with further aspects of this particular exemplary embodiment, the valve assembly may be configured to release gas from the at least one of the first set of nozzles, the second set of nozzles, and the third set of nozzles such that the release gas substantially covers an entire surface of the target wafer. 
         [0016]    In accordance with additional aspects of this particular exemplary embodiment, the first set of nozzles, the second set of nozzles, and the third set of nozzles may be alternatively positioned such that gas released from one nozzle may be different than gas released from nozzles immediately adjacent the one nozzle. 
         [0017]    In accordance with other aspects of this particular exemplary embodiment, the valve assembly may use a rod valve to selectively release at least one of the first gas, the second gas, and the third gas. 
         [0018]    In accordance with further aspects of this particular exemplary embodiment, the exhaust assembly may comprise a first exhaust line configured to exhaust at least one gas from a side opposite that of where the at least one gas may be provided. 
         [0019]    In accordance with additional aspects of this particular exemplary embodiment, the gas assembly may further comprise a fourth gas inlet configured to provide a fourth gas to the plurality of reactors, such that the first gas inlet and the third gas inlet may be positioned on a first side of the wafer and the second gas inlet and the fourth gas inlet may be positioned on a second side of the wafer, where the second side may be opposite to the first side. 
         [0020]    In accordance with other aspects of this particular exemplary embodiment, the exhaust system may further comprise a first exhaust line and a second exhaust line, such that the first exhaust line may be positioned on the second side and the second exhaust line may be positioned on the first side in order to exhaust gas from the plurality of reactors in a counter-flow scheme to improve uniformity. 
         [0021]    In another particular exemplary embodiment, the techniques may be realized as a method for atomic layer deposition (ALD) comprising releasing a first gas into a chamber of each of a plurality of reactors in order to provide atomic layer deposition of a first species, exhausting at least the first gas from the chamber while the first gas is being released into the chamber, and releasing an inert gas into the chamber to purge the chambers of the first gas. 
         [0022]    In accordance with other aspects of this particular exemplary embodiment, the method may further comprise exhausting at least the inert gas from the chamber while the inert gas is being released into the chamber. 
         [0023]    In accordance with further aspects of this particular exemplary embodiment, the method where exhausting at least the first gas may begin simultaneously with the release of the first gas. 
         [0024]    In accordance with additional aspects of this particular exemplary embodiment, the method where exhausting at least the first gas may begin after a predetermined time lag after the release of the first gas. 
         [0025]    In accordance with other aspects of this particular exemplary embodiment, the method where exhausting at least the first gas may be continuous once the at least the first gas is exhausted from the chamber while the first gas is being released into the chamber. 
         [0026]    In accordance with further aspects of this particular exemplary embodiment, the method where exhausting at least the first gas may be achieved from a side of the chamber opposite that of a side where the first gas is released. 
         [0027]    In accordance with additional aspects of this particular exemplary embodiment, the method may further comprise releasing a second gas into the chamber in order to provide atomic layer deposition of a second species, exhausting at least the second gas from the chamber while the second gas is being released into the chamber, and releasing an inert gas into the chamber to purge the chamber of the second gas. 
         [0028]    In accordance with other aspects of this particular exemplary embodiment, the second gas may be released from a side of the chamber opposite that of a side where the first gas is released. 
         [0029]    In accordance with further aspects of this particular exemplary embodiment, the method may further comprise exhausting at least the inert gas from the chamber while the inert gas is being released into the chamber. 
         [0030]    In accordance with additional aspects of this particular exemplary embodiment, the method where exhausting at least the second gas may begin simultaneously with the release of the second gas. 
         [0031]    In accordance with other aspects of this particular exemplary embodiment, the method where exhausting at least the second gas may begin after a predetermined time lag after the release of the second gas. 
         [0032]    In accordance with further aspects of this particular exemplary embodiment, the method where exhausting at least the second gas may be continuous once the at least second gas is exhausted from the chamber while the second gas is being released into the chamber. 
         [0033]    In accordance with additional aspects of this particular exemplary embodiment, the method where exhausting gas may be achieved from a side of the chamber opposite that of a side where the second gas is released. 
         [0034]    The present disclosure will now be described in more detail with reference to exemplary embodiments thereof as shown in the accompanying drawings. While the present disclosure is described below with reference to exemplary embodiments, it should be understood that the present disclosure is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein, and with respect to which the present disclosure may be of significant utility. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    In order to facilitate a fuller understanding of the present disclosure, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the present disclosure, but are intended to be exemplary only. 
           [0036]      FIGS. 1A-1B  depict an atomic layer deposition (ALD) configuration according to an embodiment of the present disclosure. 
           [0037]      FIGS. 2A-2G  depict a gas valve configuration according to various embodiments of the present disclosure. 
           [0038]      FIGS. 3A-3B  depict a gas valve configuration according to other embodiments of the present disclosure. 
           [0039]      FIG. 4  depicts an exemplary graph illustrating a cycle for atomic layer deposition (ALD) according to an embodiment of the present disclosure. 
           [0040]      FIGS. 5A-5B  depict exemplary graphs illustrating the effects of performing atomic layer deposition (ALD) according to an embodiment of the present disclosure. 
           [0041]      FIGS. 6A-6C  depict an atomic layer deposition (ALD) configuration according to another embodiment of the present disclosure. 
           [0042]      FIG. 7  depicts an exemplary graph illustrating a cycle for atomic layer deposition (ALD) according to an embodiment of the present disclosure. 
           [0043]      FIGS. 8A-8B  depict various exemplary atomic layer deposition (ALD) module configurations according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0044]    Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. It should be appreciated that the same reference numbers may be used throughout the drawings to refer to the same or like parts. It should be appreciated that the following detailed description is exemplary and explanatory only and is not restrictive. 
         [0045]    Embodiments of the present disclosure provide techniques for atomic layer deposition (ALD). In addition, embodiments of the present disclosure provide various exemplary configurations for atomic layer deposition (ALD). 
         [0046]    To solve the aforementioned problems associated with conventional atomic layer deposition techniques, embodiments of the present disclosure improve ALD productivity by introducing a stacked ALD configuration. Here, uniform flow and rapid gas delivery may be provided to each reactor to improve uniformity and repeatability of film thickness at sufficient levels. 
         [0047]    Referring to  FIG. 1A , a side view of an atomic layer deposition (ALD) configuration  100  according to an embodiment of the present disclosure is depicted. The ALD configuration  100  may be a stacked configuration comprising a plurality of reactors  102  stacked on top of one another. Each of the plurality of reactors  102  may comprise a wafer  104  positioned over one or more heating elements  106  and a thermal element  108 . The one or more heating elements  106  and the thermal element  108  may provide thermal conditioning for optimum ALD processing at each of the plurality of reactors  102 . 
         [0048]    The ALD configuration may also comprise a plurality of gas inlets  110   a,    110   b,  and  110   c  coupled to each of the plurality of reactors  102 . At each of the plurality of reactors  102 , a gas valve  112  may be provided to control gas flow over the wafer  104  in the plurality of reactors  102 . At the opposite end of the plurality of gas inlets  110   a,    110   b,  and  110   c,  an exhaust line  114  may be provided. An exhaust valve  116  may also be provided at each of the plurality of reactors  102  to control gas flow out of each of the plurality of reactors  102 . Other various embodiments may also be provided. 
         [0049]    At each of the plurality of reactors  102 , the gas valve  112  and/or the exhaust valve  116  may be used to control gas flow. In some embodiments, gas flow may be controlled by various combinations of turning on/off the gas valve  112  and/or the exhaust valve  116 . It should be appreciated that the gas valve  112  and/or the exhaust valve  116  may be positioned near a reaction chamber or space of each of the plurality of reactors  102 . Such proximity may be particularly advantageous for precise control of gas volume/flow over the wafer  104 . 
         [0050]    In one embodiment, there may be three gas inlets. For example, a first gas inlet  110   a  may provide a first gas (e.g., a first reactant gas) to the reaction chamber of each of the plurality of reactors  102  via the gas valve  112 , a second gas inlet  110   b  may provide a second gas (e.g., a second reactant gas) to the reaction chamber of the reactor  102  via the gas valve  112 , and a third gas inlet  110   c  may provide a third gas (e.g., an inert gas) to the reaction chamber of the reactor  102  via the gas valve  112 . In this example, the first gas and the second gas may be used to provide ALD reactions and the third gas may be used to purge the reaction chamber of the reactive gases (e.g., the first gas and/or the second gas). 
         [0051]    In one embodiment, for example, there may be several gas flow combinations turning on or turning off the various gas inlets  110   a,    110   b,  and  110   c.  In a first position (e.g., position  1 ), only the first gas inlet  110   a  may be opened to release a first reactive gas (e.g., reactive gas A). In a second position (e.g., position  2 ), only the second gas inlet  110   b  may be opened to release a second reactive gas (e.g., reactive gas B). In a third position (e.g., position  3 ), only the third gas inlet  110   c  may be open to release a third gas (e.g., inert gas N). In a fourth position (e.g., position  4 ), all gas inlets  110   a/   110   b,  and  110   c  may be closed. The exhaust valve may have an open position and a closed position. Other various embodiments may also be provided. 
         [0052]    It should be appreciated that while embodiments of the present disclosure are directed to using three gas inlets  110   a,    110   b,  and  110   c  to supply three gases, other various embodiments may also be provided. For example, a greater or lesser number of gas inlets, exhaust lines, gases, and/or configurations may also be provided. 
         [0053]      FIG. 1B  depicts a top view of the atomic layer deposition (ALD) configuration  100  according to an embodiment of the present disclosure. In this view, the wafer  104  may be transferred to the reactor  102  at a side adjacent to the plurality of gas inlets  110   a,    110   b,  and  110   c  and/or the exhaust line  114 . Also in this view, thermal conditioning (e.g., heat transfer) of the reactor  102  may be conducted through another side of the reactor  102 . It should be appreciated that the wafer  104  may also be rotated (e.g., about a center) (as depicted by curved arrows in  FIG. 1B ). This may be achieved via a platen, platform, or other similar assembly (not shown). 
         [0054]    It should also be appreciated that although the plurality of gas inlets  110   a,    110   b,  and  110   c  are positioned opposite to that of the exhaust line  114 , other various configurations may also be provided. For example, in some embodiments, the exhaust line  114  may be on the same side as the plurality of gas inlets  110   a,    110   b,  and  110   c,  adjacent to the plurality of gas inlets  110   a,    110   b,  and  110   c,  on the opposite side of the plurality of gas inlets  110   a,    110   b,  and  110   c  or a combination thereof. 
         [0055]    Although the ALD configuration  100  is depicted in a vertical configuration (e.g., where reactors are vertically stacked on one another), it should be appreciated that reactors  102  may also be stacked in a horizontal configuration. Other stacking configurations that minimize volume and/or space may also be provided. 
         [0056]    An advantage of using the stacked ALD configuration  100 , as described above, may improve ALD productivity. For example, reaction space at each reactor  102  may be reduced. Such reduction may improve timing and/or control of gas flow within the reactor  102 . Additionally, smaller reaction chambers may also allow better control of thermal conditions and/or reductions in the amount of reactive gases that are used. Furthermore, by stacking reactors  102  (e.g., vertically, horizontally, etc.) with smaller chambers or reactive spaces, overall volume may be reduced. Thus, a greater number of wafers may be subject to ALD without sacrificing quality and control. 
         [0057]    Referring to  FIG. 2A , a frontal view of a vertical gas valve configuration  212  according to various embodiments of the present disclosure is depicted. Here, the vertical gas valve configuration  212  may comprise a set of nozzles  213  for each gas and/or gas inlet. For example, a first set of nozzles  213   a  may be vertically placed on top of a second set of nozzles  213   b,  which may in turn be placed on top of a third set of nozzles  213   c.  In one embodiment, the first set of nozzles  213   a  may correspond to the first gas inlet  110   a,  the second set of nozzles  213   b  may correspond to the second gas inlet  110   b,  and the third set of nozzles  213   c  may correspond to the third gas inlet  110   c.  Accordingly, flow of the various gases (e.g., reactive gas A, reactive gas B, inert gas N, etc.) into the reaction chamber of each of the plurality of reactors  102  may be easily controlled using the vertical valve configuration  212 . 
         [0058]      FIG. 2B  depicts a top view of the vertical gas valve configuration  212  using a rod valve  215  according to an embodiment of the present disclosure. In this example, the nozzles  213  may be controlled (e.g., opened or closed) by a rear rod valve  215   a.  The rear rod valve  215   a  may be positioned behind the nozzles  213  and actuated by sliding in a direction horizontal to gas flow (as depicted by arrows in  FIG. 2B ). Accordingly, at an extended position, the nozzles  213  may be closed, and at a retracted position, the nozzles  213  may be opened. 
         [0059]      FIG. 2C  depicts a side view of the vertical gas valve configuration  212  using the rear rod valve  215   a  according to an embodiment of the present disclosure. In this view, the rear rod valve  215   a  is shown behind each set of nozzles  213 . In one embodiment, each rear rod valve  215   a  may be independently controlled (as depicted by arrows in  FIG. 2C ). 
         [0060]      FIG. 2D  depicts a top view of the vertical gas valve configuration  212  using a rod valve  215  according to another embodiment of the present disclosure. In this example, the nozzles  213  may be controlled (e.g., opened or closed) by a front rod valve  215   b.  The front rod valve  215   b  may be S positioned in front of the nozzles  213  and actuated by sliding in a direction horizontal to gas flow (as depicted by arrows in  FIG. 2D ). Accordingly, at an extended position, the nozzles  213  may be closed, and at a retracted position, the nozzles  213  may be opened. 
         [0061]      FIG. 2E  depicts a side view of the vertical gas valve configuration  212  using the front rod valve  215   b  according to an embodiment of the present disclosure. In this view, a front rod valve  215   a  is shown behind each set of nozzles  213 . In one embodiment, each front valve  215   b  may be independently controlled (as depicted by arrows in  FIG. 2E ). 
         [0062]      FIGS. 2F-2G  depict top views of the vertical gas valve configuration  212  using a rod valve  215  according to another embodiment of the present disclosure. In this example, the nozzles  213  may be controlled (e.g., opened or closed) by a sliding rod valve  215   c.  The sliding rod valve  215   c  may be positioned behind (or in front of) the nozzles  213  and actuated by sliding in a direction perpendicular to gas flow (as depicted by arrows in  FIGS. 2F-2G ). The sliding rod valve  215   c  may have holes that correspond or match the nozzles  213 . In a closed positioned, the holes of the sliding rod valve  215   c  may be staggered and therefore not match up with the nozzles, as depicted in  FIG. 2F . Here, gas may be prevented from flowing into the reaction chamber of the reactor  102 . In an opened position, however, the sliding rod valve  215   c  may be positioned so that the holes of the sliding rod valve  215   c  match up with the nozzles, as depicted in  FIG. 2G . Here, gas may be allowed to flow into the reaction chamber of the reactor  102 . It should be appreciated that the sliding valve  215   c  of each set of nozzles may also be independently controlled. 
         [0063]    Referring to  FIG. 3A , a frontal view of a horizontal gas valve configuration  312  according to an embodiment of the present disclosure is depicted. Here, the horizontal gas valve configuration  312  may comprise a nozzle  313  for each gas and/or gas inlet adjacent to another nozzle  313  for another gas and/or gas inlet. For example, in a configuration using three gases and/or three gas inlets, a first nozzle  313   a  may be placed horizontally and adjacent to a second nozzle  313   b,  which in turn may be placed horizontally and adjacent to a third nozzle  313   c.  In one embodiment, the first nozzle  313   a  may correspond to the first gas inlet  110   a,  the second nozzle  313   b  may correspond to the second gas inlet  110   b,  and the third nozzle  313   c  may correspond to the third gas inlet  110 c. This alternating pattern may be repeated along the entire length of the horizontal gas valve configuration  312 . Accordingly, flow of the various gases (e.g., reactive gas A, reactive gas B, inert gas N, etc.) into the reaction chamber of each of the plurality of reactors  102  may be controlled using the horizontal valve configuration  312 . 
         [0064]    For example,  FIG. 3B  depicts a top view of the horizontal gas valve configuration  312  using a rod valve  315  according to an embodiment of the present disclosure. In this example, the nozzles  313   a,    313   b,  and  313   c  may be controlled (e.g., opened or closed) by using a sliding rod valve  315 . In one embodiment, the sliding rod valve  315  may be positioned in front of the nozzles  313   a,    313   b,  and  313   c  and actuated by sliding in a direction perpendicular to gas flow (as depicted by arrows in  FIG. 3B ). In a configuration using three gases and/or three gas inlets, the sliding rod valve  315  may have holes that correspond or match every three nozzles. For example, the gas inlet  110 b may output reactive gas B at the nozzle  313   b.  The nozzle  313   b  may repeat every three nozzles along the horizontal valve configuration  312 . In an open position (e.g., where the holes of the sliding rod valve  315  may be actuated in a direction perpendicular to gas flow (see arrows) to match up with the reactive gas B nozzles, e.g., nozzle  313   b  ), the other nozzles (e.g., nozzle  313   a  for reactive gas A and nozzle  313   c  for inert gas N) may be blocked in a closed positioned since no holes match up with these nozzles. Accordingly, for any nozzle of a particular gas and/or gas inlet in an open position, the nozzles of other gases and/or gas inlets may be in a closed position. 
         [0065]    It should be appreciated that while embodiments of the present disclosure are directed to using rod valves and/or sliding valves to turn of/off the nozzles for three different gases, on/off valves and/or multi-position (e.g., three-position) valves may also be placed at the gas lines which are proximate to the nozzles. 
         [0066]      FIG. 4  depicts an exemplary graph  400  illustrating a cycle for atomic layer deposition (ALD) according to an embodiment of the present disclosure. In the graph  400 , each block may represent an amount of time a particular valve is opened. At the beginning of one cycle, the valve (e.g., Valve A) corresponding to the first reactive gas (e.g., reactive gas A) may be opened to introduce reactive gas A into each of the plurality of reactors  102 . In some embodiments, the exhaust valve may be opened at the same time as when Valve A is opened or shortly thereafter (e.g., after a predetermined time lag (Tg)), as depicted in  FIG. 4 . It should be appreciated that when there is no time lag, Tg may be zero (0). By opening the exhaust valve simultaneously with Valve A or some time thereafter, laminar flow may created. This may allow the gas, e.g., reactive gas A, to cover and adhere to the wafer  104  with greater uniformity. 
         [0067]    After a predetermined time period of ALD processing with the first reactive gas, Valve A may be closed while the exhaust valve is left open to exhaust the first reactive gas from the chamber of each of the plurality of reactors  102 . In some embodiments, exhausting reactive gas A in this manner may be eliminated. In other embodiments, the valve (e.g., Valve N) corresponding to an inert gas (e.g., inert gas N) may be opened to introduce inert gas N into each of the plurality of reactors  102  while the exhaust valve remains open. This may serve to purge any residual first reactive gas (e.g., reactive gas A) remaining in the reaction chamber of each of the plurality of reactors  102 . 
         [0068]    Once reactive gas A is purged by the flow of inert gas N, the valve N may be closed while the exhaust is kept open. This may serve to exhaust the remaining inert gas before introducing a second reactive gas. In some embodiments, exhausting inert gas N in this manner may be eliminated. 
         [0069]    Once the second reactive gas is ready to be introduced, the valve (e.g., Valve B) corresponding to the second reactive gas (e.g., reactive gas B) may be opened to introduce reactive gas B into each of the plurality of reactors  102 . In some embodiments, the exhaust valve may be opened at the same time as when Valve B is opened or shortly thereafter (e.g., after a predetermined time lag (Tg)), similar to as described above. By opening the exhaust valve simultaneously with Valve B or some time thereafter, laminar flow may created. This may allow the gas, e.g., reactive gas B, to cover and adhere to the wafer  104  with greater uniformity. 
         [0070]    After a predetermined time period of ALD processing with the second reactive gas, Valve B may be closed while the exhaust valve is left open to exhaust the second reactive gas from the chamber of each of the plurality of reactors  102 . In some embodiments, exhausting reactive gas B in this manner may be eliminated. In other embodiments, the valve (e.g., Valve N) corresponding to an inert gas (e.g., inert gas N) may be opened to introduce inert gas N into each of the plurality of reactors  102  while the exhaust valve remains open. This may serve to purge any residual second reactive gas (e.g., reactive gas B) remaining in the reaction chamber of each of the plurality of reactors  102 . 
         [0071]    Once reactive gas B is purged by the flow of inert gas N, the valve N may be closed while the exhaust is kept open. This may serve to exhaust the remaining inert gas N. In some embodiments, exhausting inert gas N in this manner may be eliminated. At this point, one cycle may be completed and subsequent cycles may commence. 
         [0072]      FIGS. 5A-5B  depict exemplary graphs illustrating the effects of performing atomic layer deposition (ALD) according to an embodiment of the present disclosure. Referring to  FIG. 5A , graph  500 A shows that improvement in thickness uniformity on a wafer may be achieved placing a time lag (Tg) between opening a gas inlet valve and opening the exhaust valve. Dependency of the uniformity on the time lag (Tg) may be increased when the period during which the gas inlet valve is open becomes shorter for an ALD cycle. Therefore, controlling timing between the gas inlet valve and the exhaust valve may be an important feature/parameter providing sufficient uniformity during an ALD cycle. 
         [0073]    It should also be appreciated that adhesive coverage of a reactive gas may be high near the inlet nozzle and such adhesive coverage may gradually decrease in proportion to a distance further from the inlet nozzle. Accordingly, when a gas inlet valve is open for short period, adhesive coverage may become small at distances from the gas inlet valve. As a result, having a time lag (Tg) may allow reactive gas flowing from the gas inlet valve to diffuse over the wafer for uniform absorption. 
         [0074]    Wafer-to-wafer uniformity may also be improved by using such timing control. For example, when the exhaust valve  116  is kept open, film thickness may be dependent on the distance between each of the plurality of reactors  102  and/or a turbo molecular pump (not shown). As depicted in  FIG. 5B , graph  500 B shows that wafer-to-wafer uniformity may be improved using timing control of the exhaust valve as compared to not using timing control of the exhaust valve. 
         [0075]      FIGS. 6A-6C  depict an atomic layer deposition (ALD) configuration  600  according to another embodiment of the present disclosure. Referring to  FIG. 6A , a side view of an atomic layer deposition (ALD) configuration  600  according to another embodiment of the present disclosure is depicted. Similar to the ALD configuration  100  of  FIG. 1A , the ALD configuration  600  of  FIG. 6  may be a stacked configuration comprising a plurality of reactors  602  stacked on top of one another. Each of the plurality of reactors  602  may comprise a wafer  604  positioned over one or more heating elements  606  and a thermal element  608 . The one or more heating elements  606  and the thermal element  608  may provide thermal conditioning for optimum ALD processing at each of the plurality of reactors  602 . 
         [0076]    However, unlike the ALD configuration  100  of  FIG. 1A , the ALD configuration  600  of  FIG. 6A  may comprise a first set of gas inlets  610   a,    610   b  and a second set of gas inlets  611   a,    611   b.  In addition, the ALD configuration  600  may comprise a first exhaust line  614   a  and a second exhaust line  614   b.  In one embodiments, the first set of gas inlets  610   a,    610   b  may be positioned opposite that of the second set of gas inlets  611   a,    611   b  with respect to the reactors  602 . In other embodiments, the first exhaust line  614   a  may be on the same side of the wafer  604  as the first set of gas inlets  610   a,    610   b,  and the second exhaust line  614   b  may be on the same side of the wafer  604  as the second set of gas inlets  611   a,    611   b.  Other various positions and/or configurations may also be provided. 
         [0077]    At a first end of each of the plurality of reactors  602 , a first gas valve  612   a  may be provided to control gas flow from the first set of gas inlets  610   a,    610   b  over the wafer  604  in the reactors  602 . At an opposite end of each of the plurality of reactors  602 , a second gas valve  612   b  may be provided to control gas flow (e.g., in the opposite direction) from the second set of gas inlets  611   a,    611   b  over the wafer  604  in the reactors  602 . Here, the second exhaust line  614   b,  which is opposite that of the first gas valve  612   a,  may control gas flow out from the first set of gas inlets  610   a,    610   b,  and the first exhaust line  614   a,  which is opposite that of the second gas valve  612   b,  may control gas flow out from the second set of gas inlets  611   a,    611   b.  Other various embodiments may also be provided. 
         [0078]    In some embodiments, gas flow may be controlled by various combinations of turning on/off the gas valves  612   a,    612   b  and/or the exhaust valves  616   a,    616   b.  It should be appreciated that the gas valves  612   a,    612   b  and/or the exhaust valves  616   a,    616   b  may be positioned near a reaction chamber or space of the reactors  602 . Such proximity may be particularly advantageous for precise control of gas volume/flow over the wafer  604 . 
         [0079]    In one embodiment, there may be four gas inlets. For example, the first gas inlet  610   a  of the first set of gas inlets may provide a first gas (e.g., a first reactant gas) to the reaction chamber of the reactors  602  via the gas valve  612   a.  The second gas inlet  610   b  of the first set of gas inlets may provide an inert gas (e.g., inert gas N 1 ) to the reaction chamber of the reactors  602  via the gas valve  612   a.  The first gas inlet  611   a  of the second set of gas inlets may provide a second gas (e.g., a first reactant gas) to the reaction chamber of the reactors  602  via the gas valve  612   b.  The second gas inlet  611   b  of the second set of gas inlets may provide another inert gas (e.g., inert gas N 2 ) to the reaction chamber of the reactors  602  via the gas valve  612   b.  In this example, the first gas and the second gas may be used to provide ALD reactions and the inert gases may be used to purge the reaction chamber of the reactive gases (e.g., the first gas and/or the second gas). It should be appreciated that inert gas N 1  may be the same or different from inert gas N 2 . Other various embodiments may also be provided. 
         [0080]    In one embodiment, for example, there may be several gas flow combinations turning on or turning off the various gas inlets  610   a,    610   b,    611   a,  and  611   d  so that a first reactive gas (e.g., reactive gas A) may form a counter-flow scheme with a second reactive gas (e.g., reactive gas B) Each gas valve  612  may have several positions: reactive gas open (e.g., position  5 ), inert gas open (e.g., position  6 ), and all gas closed (e.g., position  7 ). Each exhaust valve  616  may have an open position and closed position as well. 
         [0081]    It should also be appreciated that although the plurality of gas inlets  610   a,    610   b,    611   a,  and  611   b  are shown positioned opposite to that of the exhaust lines  614   a,    614   b,  respectively, other various configurations may also be provided. For example, in some embodiments, the exhaust lines  616   a,    616   b  may be on the same side as the plurality of gas inlets  110   a,    110   b,  and  110   c,  adjacent to the plurality of gas inlets  110   a,    110   b,  and  110   c,  on the opposite side of the plurality of gas inlets  110   a,    110   b,  and  110   c,  or a combination thereof. 
         [0082]    It should be appreciated that while the ALD configuration  600  is directed to using four gas inlets  610   a,    610   b,    611   a,  and  611   b,  two for reactive gases and two for inert gases, other various embodiments may also be provided. For example, a greater or lesser number of gas inlets, exhaust lines, gases, and/or configurations may also be provided. 
         [0083]      FIG. 6B  depicts a top view of the atomic layer deposition (ALD) configuration  600  according to an embodiment of the present disclosure. In this view, the wafer  604  may be transferred to the reactors  602  at either side adjacent to the plurality of gas inlets  610   a,    610   b,    611   a,  and  611   b  and/or the exhaust lines  614   a,    614   b.  Also in this view, thermal conditioning (e.g., heat transfer) of the reactors  602  may be conducted through another side of the reactors  602 . It should be appreciated that the wafer  604  may also be rotated (e.g., about a center of the wafer  604 ) (as depicted by curved arrows in  FIG. 6B ). This may be achieved via a platen, platform, or other similar assembly (not shown). 
         [0084]      FIG. 6C  depicts a top view of the atomic layer deposition (ALD) configuration  600  according to another embodiment of the present disclosure. In this embodiment, unlike the straight gas valves of  FIG. 6A-6B , a first gas valve  612   a ′ and a second gas valve  612   b ′ may be curved to conform to the edge of the wafer  604 . This may provide a more uniform gas flow across a surface of the wafer  604 . 
         [0085]    An advantage of using the ALD configuration  600 , as described above, is that such a configuration may improve ALD quality and productivity. For example, in addition to the benefits described with respect to the ALD configuration  100  of  FIGS. 1A-1B , the ALD configuration  600  may provide optimal flow for achieving improved uniformity. By flowing a first reactive gas in a direction counter to a direction of the second reactive gas, quality ALD processing may be achieved. 
         [0086]    It should be appreciated that gas flow may be highly controlled. For example, embodiments of the present disclosure may use customized injection points so that gas may be injected across a surface of a wafer at various points across a diameter of a chamber of the reactors  602  and/or at various angles. Other various embodiments may also be provided. 
         [0087]      FIG. 7  depicts an exemplary graph  700  illustrating a cycle for atomic layer deposition (ALD) according to an embodiment of the present disclosure. In the graph  700 , each block may represent an amount of time a particular valve is opened. At the beginning of one cycle, the first gas valve  610   a  of the first set of gas valves (e.g., Valve A) corresponding to the first reactive gas (e.g., reactive gas A) may be opened to introduce reactive gas A into the reactors  602 . In some embodiments, the second exhaust valve  616   b  (e.g., Valve E 2 ) may be opened at the same time as when Valve A is opened or shortly thereafter (e.g., after a predetermined time lag (Tg)), as depicted in  FIG. 7 . It should be appreciated that when there is no time lag, Tg may be zero (0). By opening Valve E 2  simultaneously with Valve A or some time thereafter, laminar flow may created. This may allow the gas, e.g., reactive gas A, to cover and adhere to the wafer  604  greater uniformity. 
         [0088]    After a predetermined time period of ALD processing with the first reactive gas, Valve A may be closed while Valve E 2  is left open to exhaust the first reactive gas from the chamber of the reactors  602 . In some embodiments, exhausting reactive gas A in this manner may be eliminated. In other embodiments, the valve  610   a  (e.g., Valve N 1 ) corresponding to a first inert gas (e.g., inert gas N 1 ) may be opened to introduce inert gas N 1  into the reactors  602  while the exhaust valve remains open. This may serve to purge any residual first reactive gas (e.g., reactive gas A) remaining in the reaction chamber of the reactors  602 . 
         [0089]    Once reactive gas A is purged by the flow of inert gas N 1 , Valve N 1  may be closed while Valve E 2  is kept open. This may serve to exhaust the remaining inert gas N 1  before introducing a second reactive gas. In some embodiments, exhausting inert gas N 1  in this manner may be eliminated. 
         [0090]    Once the second reactive gas is ready to be introduced, the first gas valve  611   a  of the second set of gas valves (e.g., Valve B) corresponding to the second reactive gas (e.g., reactive gas B) may be opened to introduce reactive gas B into the reactors  602 . In some embodiments, the first exhaust valve  616   a  (e.g., Valve E 1 ) may be opened at the same time as when Valve B is opened or shortly thereafter (e.g., after a predetermined time lag (Tg)), similar to as described above. By opening Valve E 1  simultaneously with Valve B or some time thereafter, laminar flow may created. This may allow the gas, e.g., reactive gas B, to cover and adhere to the wafer  604  with greater uniformity. 
         [0091]    After a predetermined time period of ALD processing with the second reactive gas, Valve B may be closed while Valve E 1  is left open to exhaust the second reactive gas from the chamber of the reactors  602 . In some embodiments, exhausting reactive gas B in this manner may be eliminated. In other embodiments, the valve  611   b  (e.g., Valve N 2 ) corresponding to a second inert gas (e.g., inert gas N 2 ) may be opened to introduce inert gas N into the reactors  602  while Valve E 1  remains open. This may serve to purge any residual second reactive gas (e.g., reactive gas B) remaining in the reaction chamber of the reactors  602 . 
         [0092]    Once reactive gas B is purged by the flow of inert gas N, the valve N may be closed while Valve E 1  is kept open. This may serve to exhaust the remaining inert gas N 2 . In some embodiments, exhausting inert gas N 2  in this manner may be eliminated. At this point, one cycle may be completed and subsequent cycles may commence. 
         [0093]    It should be appreciated that while embodiments of the present disclosure are directed to exhausting reactive and/or inert gases to each side by opening Valve E 1  or Valve E 2 , in some embodiments, those gases may be exhausted to both sides by opening Valve E 1  and E 2  simultaneously for the faster ventilation of those gases. It also should be appreciated that while embodiments of the present disclosure are directed to purging reactive gas A and B with inert gas by opening Valve N 1  or Valve N 2  differently, in some embodiments, the inert gas may be supplied at both sides of the reactor by opening both of Valve N 1  and Valve N 2  simultaneously for faster ventilation of reactive gases. Other various embodiments may also be provided. 
         [0094]      FIGS. 8A-8B  depict various exemplary atomic layer deposition (ALD) setups according to additional embodiments of the present disclosure. Referring to  FIG. 8A , an ALD setup  800 A may comprise three (3) ALD configurations  600   a,    600   b,  and  600   c.  Referring to  FIG. 8B , an ALD setup  800 B may comprise five (S) ALD configurations  600   a,    600   b,    600   c,    600   d,  and  600   e.  Therefore, in addition to productivity advantages discussed above, these setups  800 A,  800 B and other similar setup configurations may be provided to further increase ALD productivity in an efficient manner. 
         [0095]    It should also be appreciated that wafer load locks  820  may be provided to secure wafers for single, batch, or semi-batch wafer processing. In addition, it should be appreciated that wafer handling may be achieved robotically, manually, or a combination thereof. In some embodiments, the setups  800 A,  800 B may also be equipped with additional features to optimize ALD processing. For example, load locks  820  may be equipped with the pre-heating/cooling to prepare wafers for ALD processing so that additional pre-heat/cooling time at each ALD reactor may be minimized. In other embodiments, post-heating/cooling may also be provided. For example, high temperature wafers may be cooled before being transferred to a wafer station at atmospheric temperature. Other pre-/post-treatment systems may also be provided in setups  800 A,  800 B to optimize ALD processing. Other various embodiments may also be provided. 
         [0096]    It should be appreciated that while embodiments of the present disclosure are directed to ALD configurations havng stacks of eight (8) reactors, other various configurations may be provided as well. For example, a greater or lesser number of reactors may be stacked to optimize volume, time, and production needs. Furthermore, it should be appreciated that each reactor may be integrally attached to and/or removable from each other in the ALD configuration. It should also be appreciated that each reactor may be equipped with a rotating wafer holder (not shown) to hold and/or rotate the wafer for optimal uniformity during ALD processing. 
         [0097]    It should also be appreciated that while embodiments of the present disclosure are directed towards ALD, other implementations, systems, and/or modes of operation may also be provided. These may include chemical vapor deposition (CVD), etching, etc. 
         [0098]    It should also be appreciated that while embodiments of the present disclosure are described using two reactive gases and one inert gas, a greater or lesser number/types of gases may also be provided. 
         [0099]    It should further be appreciated that the disclosed embodiments not only provide several modes of operation, but that these various modes may provide additional implantation customizations that would not otherwise be readily provided. 
         [0100]    The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.