Patent Publication Number: US-2007095283-A1

Title: Pumping System for Atomic Layer Deposition

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      The present invention claims priority to a U.S. provisional patent application Ser. No. 60/732,428 filed on Oct. 31, 2005 entitled “ALD Pumping System” which is included herein at least by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention is in the field of semiconductor manufacturing equipment used in chemical vapor deposition (CVD) processes including a category of CVD known as Atomic Layer Deposition (ALD). The invention pertains particularly to methods and apparatus for regulating and manipulating purge exhaust pumping steps between reactive vapor deposition steps.  
      2. Discussion of the State of the Art  
      ALD processing encompasses one or more time-separated pulses of gas reactants, typically including but not limited to reactive gases, that react with a surface treatment of a work piece to provide deposition of a thin film of material resultant of the reaction. Usually gas phase reactants and sub-atmospheric pressure are used to form thin films on substrates heated to a moderate temperature of 100 to 400° C. In the material deposition of one or more substrates, small increases of the thin film material produced from the reactive substances accumulate over subsequent deposition cycles building up to a final film thickness over a number of cycles.  
      Therefore, in CVD processing and particularly with ALD processing, the importance of quickly cycling gasses in and out of the reactive area of the processing chamber is well known. Likewise, it is also desired that there is little or no reaction of gasses in the gas exhaust region beyond the reactive region.  
      In typical practice, the best chemistries known for creating thin films in ALD processing, for example, include reactive components that react very strongly. When mixed in gas phase, those components react violently and without adequate controls can form undesired deposits and/or particles deposited directly out of the gas phase. In some cases these deposits and/or particles can debilitate or destroy a vacuum pumping system. Therefore, it is extremely important particularly with ALD, to fully remove a first reactant before introducing the next reactant into a reactive region. Likewise, as mentioned further above it is important to ensure that reaction is suppressed, or even completely eliminated in the exhaust region.  
      In ALD, a very small amount of reactant gas may be utilized per deposition cycle. For example, a single dose of reactant required to coat a 300 mm diameter semiconductor wafer with one layer of molecules may be as small as 0.02 std cc. (One mole of gas occupies 22.4 liters at a standard chamber condition of 0 degrees Celsius and 1 atm.) Given that reactor volumes are typically on the order of liters, it is not uncommon for an ALD process to operate at less than 1% efficiency rate. This introduces another problem in that the inefficient use of a gas reactant is not only costly but also increases the possibility of undesired reaction in the exhaust from the chamber. This inefficiency factor contributes to increased maintenance, not withstanding risk to vacuum pumps and elevated “scrubbing” requirements before exhaust can be released to atmosphere.  
      Most efficient use of ALD, in particular, involves a dosing step and a purge step for each single reactive cycle under different conditions. In most cases, a dosing should entail a low gas flow, a longer residence time, and maximum precursor concentration. A purging step should entail a higher gas flow, a shorter residence time to most quickly achieve a minimum residual precursor concentration. Depending partly on the application and the chemistry being used, ALD may require dose and purge steps on the order of 100 milliseconds or less. Cycling a physical mass at those speeds is challenging by itself. The faster the mass needs to move, the lower the mass has to be to equate to success.  
      A typical approach is to utilize small valves that have been developed and that can respond in 5 ms. Such valves are commonly used for controlling the injection of reactants and purge gas. However, moving a larger device that can regulate a large cross-section separating a reactive and an exhaust region in an ALD apparatus can be much more challenging. Use of gas injected by small valves and flow restrictors has been proposed, but may suffer from being difficult to set up and operate consistently over time. Configurations using some form of exhaust constriction by mechanical means have also been proposed. However, implementation of these mechanical means as suggested may actually increase formation of particles from physical contact between moving members or increased opportunity for unwanted reactions in the exhaust region.  
      What is clearly needed in the art is an apparatus and method for varying pumping speeds in real time to accomplish more desirable results, increasing efficiency while also lowering particulate contaminants and/or undesired deposits in both the reactive region as well as in the exhaust region.  
     SUMMARY OF THE INVENTION  
      A pumping apparatus is provided for evacuating a reactant from a reactive region. The pumping apparatus includes a vacuum able chamber, a hearth for supporting a workpiece, one or more gas introduction valves, one or more exhaust evacuation valves, and an adjustable valve providing one or more pathways there through formed by alignment of separate components of the valve, the components containing two or more openings to form the pathways. In one embodiment, the pumping apparatus is used in atomic layer deposition. In another embodiment, the pumping apparatus is used in chemical vapor deposition.  
      In one embodiment, the valve components are annular plates arranged one above the other and wherein one of those plates may be rotated to form or to block the pathways. In this embodiment, the plate that is not rotated is permanently affixed to the chamber and to a centrally located hearth. In one embodiment, magnetic coupling from outside the chamber controls the rotably adjustable plate. In another embodiment, a centrally located spindle controls the rotably adjustable plate.  
      In one embodiment, the chamber includes one reactive region located above the adjustable valve, and one exhaust region located below the adjustable valve. In another embodiment, the chamber includes one reactive region located above the adjustable valve, and two or more isolated exhaust regions located below the adjustable valve, the exhaust regions isolated from one another by the rotated position of the rotably adjustable plate of the valve. In one embodiment using a spindle, the spindle is magnetically coupled to the rotably adjustable plate. In a variation of this embodiment, the spindle is physically attached to the rotably adjustable plate.  
      According to another aspect of the invention, an adjustable valve is provided for evacuating a reactive precursor from a reactive region in a semiconductor thin film process chamber. The adjustable valve includes a first perforated component rendered stationary within the process chamber, and a second perforated component geometrically similar to the first perforated component, the second perforated component rotable within the chamber to align one or more of the perforations common to both components to form one or more pathways through the valve and rotable within the chamber to misalign all of the perforations common to both components to prevent pathways through the valve.  
      In one embodiment, the semiconductor thin film process is an atomic layer deposition process. Also in one embodiment, the first and second perforated components are annular plates. In a variation of this embodiment, the second perforated component is adjustable using magnetic coupling. In another variation of this embodiment, the first perforated component is contiguously formed with the process chamber. In one embodiment, both perforated components have identical perforations strategically located in identical patterns.  
      According to a further aspect of the present invention a method is provided for purging a reactant from a reactive region of a semiconductor thin film process using an adjustable valve adjacent to the reactive region, the valve including a first perforated component rendered stationary within a process chamber, and an adjustable second perforated component geometrically similar to the first perforated component. The method includes the acts (a) determining that a reaction has occurred in the reactive region, and (b) adjusting the second perforated component to align one or more perforations common to both perforated components, the adjustment performed under vacuum pressure.  
      In one aspect of the method in act (a), the determination is made according to the passing of a pre-planned time window in which the reaction is expected to have occurred and completed. In one aspect of the method in act (b), the perforated components are annular plates and the adjustment is a rotation of one of the plates.  
      In one aspect n in act (a), sensors indicating the actual position of the adjustable valve are provided and control the actuation of gas introduction valves used for reactant and purge gas injection in act (b). 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       FIG. 1  is an elevation section view of an atomic layer deposition apparatus according to an embodiment of the present invention.  
       FIG. 2  is a plan view of a vacuum evacuation plate valve according to an embodiment of the present invention.  
       FIG. 3  is an elevation section view of an atomic layer deposition apparatus according to another embodiment of the present invention.  
       FIG. 4  is a process flow chart illustrating acts for purging reactants into a single exhaust region according to an embodiment of the present invention.  
       FIG. 5  is a process flow chart illustrating acts for purging reactants into alternate exhaust regions according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  is an elevation section view of an atomic layer deposition apparatus according to an embodiment of the present invention. Atomic Layer Deposition (ALD) apparatus  101  is logically illustrated in this example as representative of a typical ALD processing environment including a stationary hearth and frame structure  103  that supports a workpiece  102  that will be developed with thin films. Hearth  103  and workpiece  102  are, during processing, enclosed in a vacuum-tight ALD chamber  104  as is typical in the art. Workpieces  102  may be a silicon wafer or a wide variety of other types of workpieces that may be coated.  
      Chamber  104  may be provided in aluminum, stainless steel, or any other durable material known to be applicable in ALD processing. Workpiece  102  is assumed to be pre-treated with an agent that will react with an introduced reactive gas. Chamber  104  has an input valve  113 , through which gasses are introduced into a process region, also called a reactive region  111 . Introduction valve  113  is exemplary only. There may be other locations for introduction valves on chamber  104 , as well as more than one valve without departing from the spirit and scope of the present invention.  
      In this example, reactive precursors are introduced through valve  113  into reactive region  111  in the direction of the arrow shown. Reactive region  111  is generally defined as the space closest to the workpiece where the introduced precursor reacts with the material on the surface of the workpiece to produce a layer of thin film.  
      A pair of annular valve plates illustrated herein as a valve plate  105  and a valve plate  106  further defines reactive region  111 . Valve plates  105  and  106  together form a vacuum valve for enabling very quick high-flow purging of any gas reactant from reactive region  111  after a cycle of reaction has occurred. The precursor gasses introduced, typically one at a time, flow radially out over workpiece  102  with the plate-valve typically closed during the reaction phase of each ALD cycle.  
      Plate  105  and  106  are not identical plates. One plate, plate  105  in this example, is welded, contiguously formed with or otherwise intimately attached around its outer diameter to the inside wall of chamber  104  such that gasses are restricted from passing around the periphery of the plate. In one embodiment, plate  105  has an inner diameter just large enough to fit over the outer diameter of the main body of hearth  103 . Plate  105  may also be permanently affixed by welding, contiguously formed with or otherwise intimately attached to the outer wall of hearth  103  such that gasses are restricted from passing by the inner wall of the plate. In this example, plate  105  is fixed in ALD apparatus  101  and cannot be moved, adjusted or rotated. In one embodiment, plate  105  is fixed to chamber  104  and hearth  103  such that there is no gap between the plates outer and inner diameters and the interfacing walls of the chamber and hearth. In one embodiment, plate  105  is a contiguous part of chamber  104  and is not a separate piece that must be attached. In this embodiment, plate  105  is created along with chamber  104  when it is machined.  
      Plate  106 , unlike plate  105 , is not fixed to apparatus  101 , and maybe adjusted rotably about hearth  103  in either direction. Plate  106  has an outer diameter just smaller that the inner diameter of chamber  104  and an inner diameter just larger than the outer diameter of the main body of hearth  103 . The gap between the outer diameter of plate  106  and the chamber wall and the gap between inner diameter of plate  106  and the hearth main body are not as important as the gap spacing between plates  105  and  106  for determining the leakage of the overall valve structure. However, because of the simple geometry of the valve structure commonly used machining techniques can hold gaps within a range of about 20 to 50 microns if so required. Plates  105  and  106  have a very small gap between them just enough to enable rotation of one plate in geometric relation to the other without binding the plates or creating undesired contact or friction. In one embodiment, each plate on its interfacing surface has a pattern of concentric micro-rings machined therein such that one pattern is raised and the other is grooved. In this case, the plates may be brought very close together without touching while eliminating any gap between them by virtue of mating the patterns. In one embodiment, plate  105  may be the rotatable plate and plate  106  may be the fixed plate. However, the inventor prefers the rotate able plate to be on the bottom so that reactants cannot seep through to the lower plate unless it is rotated to an open position. However, it is not absolutely necessary to have a completely vacuum tight reactive region in order to practice the present invention successfully. In particular, a non-sealing valve such as implemented by plates  105  and  106  can be instrumental in preventing particles from both physical contact and unwanted reaction. Incorporating additional features such as grooves, narrowed passages, and possibly introduction of local purge gas in the gap between  105  and  106  all can effectively route each reactant towards separated locations and thereby suppress unwanted reaction.  
      Plates  105  and  106  may be manufactured of aluminum or stainless steel or other acceptable materials used in ALD processes. Typically such materials may be machined to a high state of finish and may maintain in a high degree of flatness and dimensional integrity through repeated ALD processing, which may exhibit temperature and pressure fluctuations.  
      In this example, plates  105  and  106  are perforated with a pattern of openings provided for enabling evacuation of precursor from reactive region  111  via vacuum exhaust pumping. In one embodiment, each pattern of openings may be identical for each plate. In another embodiment, one plate may have more openings than another plate. The exact number and profile of individual openings as well as strategic patterning of those openings, if any is observed, is a matter of design. As with many vapor deposition processes, shapes and sizes of openings provided for gas injection and evacuation may very, sometimes specifically, according to the types of chemistries used in the process. A general goal for reactive chemistries is to provide very low flows for dosing a reactive region in deposition and very high flows for purging the reactive region.  
      In this example, there are two fully bound elongated slots in each plate with both patterns identical to the other. It is noted herein that the openings do not have to be fully bound in order to practice the invention. For example, the openings may be slots that open to the outside wall of the plate. Plate  105  has openings  107  and  109  and plate  106  has openings  108  and  110 . In this example, plate  106  may be rotated against plate  105  to align the openings forming pathways through the valve or to close off the openings blocking all potential pathways. Plates  105  and  106  together form a vacuum assisted evacuation valve for quick evacuation of any reactants left over from a deposition cycle.  
      Apparatus  101  has an exhaust region  112  that generally includes the region below plates  105  and  106 . Apparatus  101  is pumped down using one or more vacuum pumps (not illustrated) or other mechanisms that can produce the vacuum required by the process. When plates  105  and  106  are aligned with respect to common perforations or openings, gas previously introduced into work region  111  may be quickly pumped out by exhaust region  112 . A simple rotation of plate  106  in this example causes immediate evacuation of the gas through the aligned openings. One or more of the perforations in the plates are aligned, and the flow from region  111  to region  112  is very high and pressure very low providing optimum conditions needed for a purge step in the deposition cycle. When plates  105  and  106  are not aligned all of the openings are blocked. In this state there is little or no flow from region  111  into region  112 . The pumping speed out of reactive region  111  is reduced or stopped entirely so that low flows and high pressure can be used to most efficiently utilize reactants during the dose step or reactive phase of the deposition cycle. This state is held for the required time of the reaction to form a layer of thin film on the work piece.  
      The mechanism and apparatus for powering the rotation of plate  106  is not illustrated in this example, but may be assumed present. In one embodiment, rotation of plate  106  may be accomplished through a magnetic coupling interface that may be mounted on the outside chamber  104  such that a magnetic interface makes contact with a similar interface provided on plate  106 . Plate  106  may be controlled relative to rotation by automated computer-aided system in terms of rotation direction, amount of rotation, and frequency of rotation. The mechanics of controlling the rotation via magnetic coupling may be electronic, pneumatic, or compressed air assisted. At typical cycle speeds of 100 milliseconds or less for a complete dose and purge, one with skill in the art will appreciate that a purge valve such as the valve of this invention comprising plates  105  and  106  is much easier to move than a linearly activated vacuum plate typical of current practice. Moreover, the plate thickness required of linear plates under the typical vacuum conditions reached in chamber  104  is much higher, up to two times the required thickness of plate  106 . Therefore faster dose and purge sequences are possible using the apparatus of the present invention.  
      In another embodiment, plate  106  may be controlled through a vertical spindle apparatus (not illustrated) that extends from the bottom-sealing surface of chamber  104  up through hearth  103  to the level of plate  106 . In this case, magnetic coupling may also be implemented inside chamber  105  between the spindle and the inner diameter of plate  106 , coupling accomplished through the wall of hearth  103 . In a variation of this embodiment, there may be one or more a mechanical arms extending from the spindle through slots strategically placed through the wall of hearth  103  those arms connected to the inside wall of plate  106 . Controlled rotation of the spindle then rotates the plate as required. In this embodiment, rotation amounts may be indexed and there may be continuing revolutions of plate  106  in one direction, or there may be back and forth rotations of a specific distance for aligning and blocking the openings. Control of the spindle may be electronic pneumatic or compressed air indexed. There are many possible physical manifestations that may be implemented using existing technologies that will not interrupt vacuum inside chamber  104  or otherwise interfere with the mechanics of the overall processing.  
       FIG. 2  is a plan view of a vacuum evacuation plate valve  200  according to an embodiment of the present invention. In this example, Plates  105  and  106  described above form valve  200 . Either plate  105  or plate  106  may be the rotably adjustable plate in valve  200 , but it is generally preferred that the bottom plate is the rotably adjustable plate for flow restriction purposes in this embodiment. In this example, openings  107  and  109  of plate  105  are not in alignment with openings  108  and  110  of plate  106 . In this example, a 90 degree back and forth rotation of plate  106  can open and close valve  200 . In one embodiment, there may be other planned amounts of rotation such as to partially align the perforations common to plates  105  and  106  to provide smaller or larger pathways if required. The flow speed variability is not limited and desired flow speeds depend on planned process chemistries used and required dose and purge cycle times associated to those chemistries. There are many possibilities.  
       FIG. 3  is an elevation section view of an atomic layer deposition apparatus  300  according to another embodiment of the present invention. Apparatus  300  is very similar in conceptual design to apparatus  100  described above, with an exception that apparatus  300  is capable of alternating purge cycles such that gases may be pumped into two or more separated exhaust regions. In this example, a chamber  301  is illustrated and is logically separated into two different isolated exhaust regions. These exhaust regions are exhaust region  309  and exhaust region  310 . As described further above with chamber  104 , reactive gasses are introduced into chamber  300  through a central valve  302 . A work piece  313  supported by a central hearth  308  is analogous to work piece  102  supported by hearth  103  described above.  
      In this example, a plate  304  and a plate  303  accomplish the valve of the present invention. In this example, plate  304  is the rotably adjustable plate and plate  303  is the fixed plate although the configuration may be reversed without departing from the spirit and scope of the present invention as was described further above. Fixed plate  303  has two openings illustrated here as opening  306  and opening  307 . In this example, the openings are located approximately on opposite sides of the plate, one at zero degrees and the other at approximately 180 degrees. Openings  306  and  307  may be analogous in shape and size to openings  107  and  109  described further above. Other shapes and sizes as well as numbers and locations of openings may also be provided without departing from the spirit and scope of the present invention. The configuration shown here is exemplary only.  
      Unlike plate  303  that has two openings (one for each exhaust region) plate  304  may have a single opening or more openings. One opening visible in this example is opening  305 . Opening  305  is positioned in alignment with opening  306  through plate  303 . If there is a second opening in plate  304 , it is not visible in this example because it is positioned behind hearth  308 , perhaps at 90 degrees approximate from opening  305 . In one embodiment, opening  305  is the only opening in plate  304 . For exemplary purposes only, vacuum pump-out valves  311  and  312  are illustrated in this example. Valve  311  is dedicated to pump out exhaust region  310  and valve  312  is dedicated to pump out exhaust region  309 .  
      In this particular configuration, it may be important that reactive gasses are purged into separate exhaust regions to, for example, allow for separated abatement treatment or routing to independent vacuum pumping system. For example in a first dose step a first reactive gas may be introduced into a reactive region or work region illustrated here as reactive region  314  through valve  302 . After the reaction occurs in the dose step, plate  304  is rotated as shown here to align openings  305  and  306 . In this case, the gas is pumped out through a pathway formed by openings  305  and  306  into exhaust region  310  and out through pump-out valve  311 . In this case there is a high flow and low pressure with respect to exhaust region  310 . The reactive gas is pumped out generally in the direction of the arrows.  
      For the next cycle, a different gas may be used. Plate  304  is rotated to block all openings for the dose of the next reactant. Low flows and high pressure occupy reactive region  314  for the dose step. Plate  304  may then be rotated to align opening  305  with opening  307  to form a pathway for purge of reactant into exhaust region  309  and out pump-out valve  312 . In one embodiment, exhaust regions  310  and  309  may be controlled relative to volume to exist having minimal volume just under reactive region  314 . In another embodiment, direct porting may be implemented between openings  306  and  307  and respective pump-out valves  311  and  312  respectively. It is noted herein as well that there may be more than two separate exhaust regions implemented without departing from the spirit and scope of the present invention. Likewise, there may be more than two openings in plate  303  a portion of which may be dedicated to a specific exhaust region.  
       FIG. 4  is a process flow chart illustrating acts  400  for purging reactants into a single exhaust region according to an embodiment of the present invention. At act  401  a treated workpiece is staged for cycling. In some processes, staging a workpiece is automatic. In other processes, a user performs workpiece staging manually.  
      At act  402 , a determination is made regarding the plate valve state, for example whether the openings are blocked for dosing or open to create one or more pathways for purging. In most processes that repeat, the plate valve will automatically be closed by default at the beginning of a process. If at act  402  it is determined that the openings are open, in other words, the plates are aligned for purge, then at act  403 , the rotably adjustable plate of the pair comprising the plate valve is rotated to block the openings for the dosing portion of the sequence. The process then resolves to act  404  wherein the reactive precursor is introduced into the reactive region. If at act  402  it is determined that the openings are blocked then the process moves directly to act  404 .  
      At act  404  a reactive gas is introduced that reacts with the treated surface of the workpiece to produce a layer of thin film covering the exposed or un-masked areas of the workpiece. It is assumed that the reaction takes place in act  404  as the gas is introduced in a pulse. At act  405  the reaction may be monitored for progress. Act  405  may simply be a time period in which the reaction is expected to occur and culminate in the thin film layer. In one embodiment however, instrumentation may be provided for measuring the reaction and the results of that reaction. In another embodiment the change in position of the rotating plate itself is used to control the introduction of reactive gas and purge gas.  
      At act  406 , it is determined whether the reaction has completed. If it has, then the rotably adjustable plate is rotated to align the openings in both plates to create a pathway for purging what is left of the reactive gas. If at act  406  it is determined that the reaction is not complete then the process resolves back to act  405  for monitoring. An affirmative at act  406  may be just an indication of the end of the planned reaction time window. Act  407  may involve a total alignment of the openings or a partial alignment of the openings depending on the design of the process. Likewise, the openings may be holes, slots, or openings of varied shapes and sizes without departing from the spirit and scope of the present invention.  
      At act  408 , a purge step is performed to pump-out any residue in the reactive region into an exhaust region. Although not illustrated in this process flow, act  408  may involve introduction of an inert gas into the reactive region just before pump-out. During purge in act  408  very high flows are created at very low pressure. In one embodiment, there may be a sub-act associated with act  408  for monitoring the purge and determining when the purge act is complete. In one embodiment, a pre-planned time window is provided wherein the expected results of the purge should be accomplished. Therefore, the determination that the purge is complete may be just an indication of the end of the purge cycle in time. After act  408  is complete in any case, the process resolves back to act  403  wherein the rotably adjustable plate is rotated again to block the openings in the plates. At act  404  a next precursor may be introduced and the process continues until the workpiece is finished.  
       FIG. 5  is a process flow chart illustrating acts  500  for purging reactants into alternate exhaust regions according to an embodiment of the present invention. At act  501 , a treated workpiece is staged for processing as described above. At act  502 , a determination may be made as to the rotational position of the plates indicating alignment or blockage of the openings. If at act  502 , the openings are not blocked then the process resolves to act  503  wherein the rotably adjustable plate is rotated to block the opening or openings for the dose portion of the cycle. If at act  502  it is determined that the openings are blocked, then the process moves directly to act  504  wherein a reactive precursor is introduced into the reactive region. If the rotably adjustable plate has to be rotated to block the openings in act  503 , the process resolves to act  504  just described.  
      At act  505 , the reaction resulting from the introduction of the precursor in act  504  may be monitored to determine results of the reaction and whether the reaction is complete. The monitoring may be active monitoring or just an indication of the end of a pre-planned time period in which the reaction is expected to take place and to complete. At act  506  a determination is made if the reaction is complete. If not, then the process resolves back to act  505 . If the reaction has completed in act  506 , then at act  507  the adjustable plate is rotated to open or align two or more openings to a specific exhaust region. This is where the process differs from the process explained in the description of  FIG. 4 . That is to say that in this example, a specific exhaust region of more than one region is dedicated to pumping out the precursor introduced in act  504 . Therefore, only a specific alignment has to be performed with respect to the rotably adjustable plate of the valve opening only the pathway or pathways dedicated to that exhaust region.  
      At act  508 , a purge process is performed, which may include a sub act for introduction of an inert gas and a sub act for monitoring. After the purge is complete into the designated exhaust region, the process resolves back to act  503  in which the rotably adjustable plate is rotated again to block all openings.  
      The process then moves to act  509  wherein a next reactive precursor, different from the precursor of act  504 , is introduced. The process then moves back to act  505  for monitoring and act  506  to determine if the reaction resulting from the gas introduction of act  509  is complete. It is noted herein that the cycle times may be different for different chemistries. If at act  506 , the next reaction is not complete, the process may loop back to monitoring at act  505 . If the reaction is determined to be complete at act  506 , then at act  510 , the rotably adjustable plate is rotated to align the opening or openings dedicated as passages into the next exhaust region. During this phase, the initial exhaust region and any other regions are blocked.  
      The process then moves back to act  508  for purging, which may include a sub-act for monitoring and a sub act for introducing an inert gas into the reactive region as previously described. After the purge act  508 , the process moves back to act  503  wherein the rotably adjustable plate is again rotated to block all openings in preparation for a dosing involving the next precursor introduction.  
      One with skill in the art will appreciate that use of different chemistries may alter the process somewhat without departing from the spirit and scope of the invention. Likewise, there may be fewer or more acts including sub-acts implemented in acts  400  or in acts  500  depending on the exact process design followed. Generally speaking the acts of rotably adjusting the plate valve according to its design and purpose, whether designed with one exhaust region or more than one exhaust region represents an improved process over those requiring linear displacement of large vacuum plates or lids.  
      In one embodiment, there may be sensors provided that indicate the actual positioning of the adjustable valve in order to control the actuation of gas introduction valves used for reactant and purge gas injection relative to dose and purge acts of this process. In this embodiment, provision of such motion or “travel” sensors allows the motion of the adjustable valve to be either continuous at variable speed, or in discrete steps, always with correct timing of reactant introduction and routing of each reactant to its own separated exhaust region with minimal undesired mixing.  
      Although the embodiments and processes described herein are targeted chiefly for ALD processing, it will be clear to one with skill in the art that advantages provided by the invention may also apply to many CVD processes as well. Likewise, other shapes of valve components may be envisioned and implemented without departing from the spirit and scope of the present invention. Such alternatives to rotably adjustable plates include a spherical component pair or a cylindrical component pair where one of the components is adjustable to align or misalign perforations or openings common to both components of the pair.  
      In still another alternative embodiment, two linear moveable valve plates may be provided, each having two or more openings that may be aligned to form pathways or blocked to prevent pathways using linear displacement of one of the plates. While less effective than rotation for reducing cycle time, such an apparatus would be more effective that a single heavy vacuum plate or lid. Therefore the methods and apparatus of the invention as described herein should be afforded the broadest possible scope under examination. The spirit and scope of the present invention should be limited only by the following claims.