Abstract:
A contamination mitigation or surface modification system for ion implantation processes includes a gas source, a controller, a valve, and a process chamber. The gas source provides delivery of a gas, be it atmospheric or reactive, to the valve and is controlled by the controller. The valve is located on or about the process chamber and controllably adjusts flow rate and/or composition of the gas to the process chamber. The process chamber holds a target device, such as a target wafer and permits interaction of the gas with an ion beam to mitigate contamination of the target wafer and/or to modify the existing properties of the processing environment or target device to change a physical or chemical state or characteristic thereof. The controller selects and adjusts composition of the gas and flow rate according to contaminants present within the ion beam, or lack thereof, as well total or partial pressure analysis.

Description:
RELATED APPLICATION  
       [0001]     This application claims the priority of U.S. Provisional Application Ser. No. 60/719,247, filed Sep. 21, 2005, entitled SYSTEMS AND METHODS THAT MITIGATE CONTAMINATION DURING ION IMPLANTATION PROCESSES THROUGH THE INTRODUCTION OF REACTIVE GASES. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates generally to ion implantation typically employed in semiconductor device fabrication, and more particularly, to mitigating contamination and/or modifying the surface characteristics of target devices through the introduction of gases during ion implantation.  
       BACKGROUND OF THE INVENTION  
       [0003]     Ion implantation is, typically, a physical process that is employed in semiconductor device fabrication to selectively implant dopant into semiconductor and/or wafer material. Thus, the act of implanting does not rely on a chemical interaction between a dopant and semiconductor material. For ion implantation, dopant atoms/molecules are ionized, accelerated, formed into a beam, analyzed, and swept across a wafer, or the wafer is swept through the beam. The dopant ions physically bombard the wafer, enter the surface and come to rest below the surface, at a depth related to their energy.  
         [0004]     An ion implantation system is a collection of sophisticated subsystems, each performing a specific action on the dopant ions. Dopant elements, in gas or solid form, are positioned inside an ionization chamber and ionized by a suitable ionization process. In one exemplary process, the chamber is maintained at a low pressure (vacuum). A filament is located within the chamber and is heated to the point where electrons are created from the filament source. The negatively charged electrons are attracted to an oppositely charged anode also within the chamber. During the travel from the filament to the anode, the electrons collide with the dopant source elements (e.g., molecules or atoms) and create a host of positively charged ions from the elements in the molecule.  
         [0005]     Generally, other positive ions are created in addition to desired dopant ions. The desired dopant ions are selected from the ions by a process referred to as analyzing, mass analyzing, selection, or ion separation. Selection is accomplished utilizing a mass analyzer that creates a magnetic field through which ions from the ionization chamber travel. The ions leave the ionization chamber at relatively high speeds and are bent into an arc by the magnetic field. The radius of the arc is dictated by the mass of individual ions, speed, and the strength of the magnetic field. An exit of the analyzer permits only one species of ions, the desired dopant ions, to exit the mass analyzer.  
         [0006]     An acceleration system is employed to accelerate or decelerate the desired dopant ions to a predetermined momentum (e.g., mass of a dopant ion multiplied by its velocity) to penetrate the wafer surface. For acceleration, the system is generally of a linear design with annular powered electrodes along its axis. As the dopant ions enter therein, they are accelerated there through.  
         [0007]     An end station holds one or more target wafers into which an ion beam from the acceleration system implants one or more dopants. The end station is operable to move or scan the one or more target wafers in one or two dimensions as the ion beam strikes the target wafer(s) in order to obtain desired coverage of the target wafer and dose amount in accordance with a prescribed ion implantation process.  
         [0008]     One problem that can occur during the ion implantation process is the unwanted introduction of atomic or molecular contaminant particles into the ion beam. These contaminant particles can be introduced into the beam at various stages of the system, such as within the mass analysis subsystem, the acceleration electrodes and/or the end station. These particles can be undesirably implanted into, or deposited onto, one or more target wafers, resulting in degradation or failure of devices formed thereon.  
       SUMMARY OF THE INVENTION  
       [0009]     The following presents a simplified summary in order to provide a basic understanding of one or more aspects of the invention. This summary is not an extensive overview of the invention, and is neither intended to identify key or critical elements of the invention, nor to delineate the scope thereof. Rather, the primary purpose of the summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.  
         [0010]     The present invention discloses methods and systems that mitigate contamination and/or modify surface characteristics during ion implantation processes by introduction of atmospheric or reactive gases during the ion implantation process. It has been discovered that these introduced gas(es) can prevent or mitigate contaminants from being implanted into target devices, such as silicon wafers by one or more mechanisms. While not intending to be confined by theory, it is assumed that one of the mechanisms is the formation of gaseous volatile compounds by the reactive gas, which interact with the contaminants at the target surface, whereby the volatile compounds are then removed by, for example, a cryogenic or turbo-molecular pump. Another mechanism involves the formation of a surface layer, such as a passivation layer, created by the presence of the reactive gas during ion implantation. The surface layer mitigates or prevents implanting of contaminants into underlying layers of the device.  
         [0011]     In accordance with one aspect of the present invention, a contamination mitigation system for ion implantation processes includes a process chamber having a gas source/supply, a controller, and a valve coupled thereto. The gas source, for example, a pressurized gas cylinder, delivers a reactive gas to the process chamber via a valve that is selectively operated by the controller. The valve is located on or about the process chamber and controllably adjusts flow rate and/or composition of the gas(es) delivered to the process chamber. The process chamber holds a target device, such as a target wafer such that the gas(es) is permitted to interact with the ion beam or the wafer surface to mitigate contamination of the target wafer. In one embodiment, the controller can select and adjust the composition of the reactive gas as well as the flow rate according to monitored contaminants present within the ion beam or on the surface of the device or target. Other systems, methods, and detectors are also disclosed.  
         [0012]     To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects and implementations of the invention. These are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a block diagram of an ion implantation system in accordance with one or more aspects of the present invention.  
         [0014]      FIG. 2  is a block diagram of an ion implantation process modification system in accordance with an aspect of the present invention.  
         [0015]      FIG. 3  is a block diagram depicting an interior of a process chamber during an ion implantation process in which a reactive gas in introduced to mitigate contamination in accordance with an aspect of the present invention.  
         [0016]      FIG. 4  is a diagram of an ion implantation process modification system is described in accordance with an aspect of the present invention.  
         [0017]      FIG. 5  is a flow diagram illustrating a method mitigating contamination of a target device by contaminants during ion implantation in accordance with an aspect of the present invention.  
         [0018]      FIG. 6  is a flow diagram illustrating a method mitigating contamination of a target device by contaminants during ion implantation that introduces a reactive gas and measures gas within a process chamber during ion implantation in accordance with an aspect of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The present invention will now be described with reference to the attached drawings, wherein like reference numerals are used to refer to like elements throughout. It will be appreciated by those skilled in the art that the invention is not limited to the exemplary implementations and aspects illustrated and described hereinafter.  
         [0020]     As semiconductor devices, such as sub-micron CMOS structures, become smaller and smaller, the ion implantation processes required to modify electrically active regions of semiconductor devices become shallower and more sensitive to the material properties in the surface and near surface regions of the semiconductor devices. Additionally, semiconductor devices are more sensitive to surface contamination from sputtered materials and absorbed gases present during implantation processes, particularly the concentration and distribution of contaminants within active device regions. Contaminants or particles can be implanted with the ion beam and negatively impact diffusion and other properties of formed structures and/or devices. As a result, for example, this contamination can result in undesirable and varied device parameters for fabricated semiconductor devices.  
         [0021]     Particles or atomic contaminants, which are also referred to later as ion beam contaminants, can arise for a variety of sources during ion implantation. For example, carbon can be generated from apertures and other surfaces within the ion implantation system. Typically, the carbon particles are generated by ion beam striking carbon based surfaces such as graphite, which is a commonly used material within ion implantation systems. Additionally, sputtering processes and other deposition mechanisms can release unwanted carbon particles. Additionally, photoresist material, which is commonly used as a mask for ion implantation typically, contains carbon, which can then be released during ion implantation. Although carbon is provided as an example of a type of particle or contaminant, contamination from other materials or types of particles or contaminants is contemplated by the present invention.  
         [0022]     Aspects of the present invention mitigate contamination during ion implantation by employing a reactive gas, such as an atmospheric gas, oxygen containing gas, water vapor, and the like, that reacts with contaminants or particles in order to reduce contamination. Additionally, the reactive gas can also be used to modify the target properties or characteristics determined by previous processes.  
         [0023]     Referring initially to  FIG. 1 , an ion implantation system  100  suitable for implementing one or more aspects of the present invention is depicted in block diagram form. The system  100  includes an ion source  102  for producing an ion beam  104  along a beam path. The ion beam source  102  includes, for example, a plasma source  106  with an associated power source  108 . The plasma source  106  may, for example, comprise a relatively long plasma confinement chamber from which an ion beam is extracted.  
         [0024]     A beam line assembly  110  is provided downstream of the ion source  102  to receive the beam  104  there from. The beam line assembly  110  includes a mass analyzer  112 , and an acceleration structure  114 , which may include, for example, one or more gaps. The beam line assembly  110  is situated along the path to receive the beam  104 . The mass analyzer  112  includes a field generating component, such as a magnet (not shown), and operates to provide a field across the beam path so as to deflect ions from the ion beam  104  at varying trajectories according to mass (e.g., charge to mass ratio). Ions traveling through the magnetic field experience a force which directs individual ions of a desired mass along the beam path and which deflects ions of undesired mass away from the beam path.  
         [0025]     The acceleration gap or gaps within the acceleration structure  114  are operable to accelerate and/or decelerate ions within the beam to achieve a desired depth of implantation in a work piece. Accordingly, it will be appreciated that while the terms accelerator and/or acceleration gap may be utilized herein in describing one or more aspects of the present invention, such terms are not intended to be construed narrowly so as to be limited to a literal interpretation of acceleration, but are to be construed broadly so as to include, among other things, deceleration as well as changes in direction. It will be further appreciated that acceleration/deceleration means may be applied before as well as after the magnetic analysis by the mass analyzer  112 .  
         [0026]     An end station  118  is also provided in the system  100  to ion beam  104  from the beam line assembly  110 . The end station  118  supports one or more work pieces, such as semiconductor wafers (not shown), within a process chamber and along the beam path for implantation using the mass analyzed ion beam  104 . The end station  118  includes a target scanning system  120  for translating or scanning one or more target work pieces and the ion beam  104  relative to one another. The target scanning system  120  may provide for batch or serial implantation, for example, as may be desired under given circumstances, operating parameters and/or objectives.  
         [0027]     Particles or atomic contaminants can enter the ion beam  104  during ion implantation that, if implanted, can damage or degrade operation of semiconductor devices formed on the one or more work pieces. The particles or atomic contaminants arise for a variety of sources during ion implantation. For example, carbon can be generated from apertures and other surfaces within the acceleration structure  114 . Typically, the carbon particles are generated by ion beam striking carbon based surfaces such as graphite, which is a commonly used material within ion implantation systems. Additionally, sputtering processes and other deposition mechanisms can release unwanted carbon particles. Additionally, photoresist material, which is commonly used as a mask for ion implantation typically, contains carbon, which can then be released during ion implantation. Although carbon is provided as an example of a type of particle or contaminant, contamination from other materials or types of particles or contaminants is contemplated by the present invention.  
         [0028]     A gas insertion system  122  is also included within the end station  118  and inserts a gas, such as a reactive or atmospheric gas, that mitigates contamination of the one or more work pieces during ion implantation. The gas reacts with contaminants or particles within the ion beam  104  in order to reduce contamination. The gas can react with the contaminants in by a number of mechanisms to reduce contamination of the work pieces and remove the particles or atomic contaminants from the ion beam  104 .  
         [0029]     In one mechanism, the gas can form a passivation layer on a top surface of a target semiconductor devices formed on the one or more work pieces by interacting with the ion beam  104 . The passivation layer  104  can reduce contaminants from passing through to underlying layers and/or mitigate out diffusion of dopants during later fabrication steps. The passivation layer can be comprised of, for example, oxide, nitride, and the like and can be formed by an ion beam enhanced formation process. The passivation layer is formed by a process that is facilitated by the ion implantation and the presence of the reactive gas. For example, an ion beam destroys at least some of the surface bonds of silicon, which results in the silicon having a higher probability of forming an oxide. Then, by supplying an oxygen or water vapor containing gas during the ion implantation, oxide is more readily formed as a passivation layer. The passivation layer can then act as a diffusion barrier to mitigate out diffusion during later fabrication steps.  
         [0030]     Another mechanism to reduce contamination is by employing a gas for consuming contaminants, such as carbon, that would otherwise be absorbed on the surface and driven into the material by the ion beam. The gas or components within the gas can react with the contaminants and form compounds that do not get implanted and/or can be swept away. For example, formation of volatile compounds or gaseous compounds, CO for example, can be readily pumped away or removed by a high vacuum system. This reduces or removes contaminants or particles that could be driven into target semiconductor devices.  
         [0031]     Referring initially to  FIG. 2 , an ion implantation process modification system  200  is described in accordance with an aspect of the present invention. The system  200  modifies a current ion implantation process by introducing atmospheric and/or reactive gases during the ion implantation process for the modification and control of material properties resulting from the ion implantation process. The system  200  can be employed, for example, with single wafer ion implantation systems, batch ion implantation systems, plasma immersion ion implantation systems and the like.  
         [0032]     The system  200  includes a gas source/supply  202 , a controller  204 , a gas analyzer  206 , a controllable valve  210 , and a process chamber. The gas source/supply  202  is a mechanism that controllably delivers a gas, such as atmospheric or reactive gas, to the process chamber  212  through a controllable valve  210 . The gas is comprised of one or more individual atmospheric and/or reactive gases. The gas source/supply  202 , in one example, is comprised of one or more gas cylinders, an evaporation or sublimation system, and/or atmospheric inlet (not shown). The gas cylinder contains a reactive gas or vapor at a pressure high enough to provide a required gas flow via the controllable valve  210  to the process chamber  212 . The evaporating system is comprised of water or any other liquid or solid material to generate a reactive gas vapor. In another example, the gas source/supply  202  comprises a source reservoir containing a reactive material in liquid or solid form capable of being evaporated or sublimated at a pressure sufficient to provide the gas. The valve  210  comprises one or more individual valves for selecting flow rate and composition of the reactive gas ultimately provided to the process chamber. The valve  210  is controlled by the controller  204 , which adjusts the flow rate and composition of the reactive gas in order to facilitate removal of contaminants or particles and to mitigate contamination of a target semiconductor device (not shown) within the process chamber  212 .  
         [0033]     The process chamber  212  is part of an end station of an ion implantation system, which can be a single wafer and/or batch ion implantation system. The process chamber  212  holds or supports one or more target devices, such as target wafers, for ion implantation. An ion beam, generated as part of the ion implantation system, enters the process chamber  212  and implants dopants within the ion beam into the target device(s). Typically, the ion beam and/or the process chamber include undesired particles or contaminants that result in contamination of the target devices, as described above.  
         [0034]     The reactive gas enters the process chamber  212  via the valve  210  and interacts with the ion beam to mitigate contamination of the target device(s) by the particles or contaminants. The reactive gas employed is selected according to a type or composition of expected particles or contaminants. Some examples of suitable gases that can be employed include atmospheric gases, such as oxygen, nitrogen, water vapor, and the like. However, other reactant gases can also be employed. The gas can react with the contaminants in by a number of mechanisms to reduce contamination, such as combining with the contaminants and becoming volatile and then removed by vacuum pumping and/or creating a surface condition that prevents or mitigates particles from being implanted beyond or about the created surface condition.  
         [0035]     As one example of a suitable mechanism, the gas can form a passivation layer on a top surface of a target semiconductor device by interacting with the ion beam. The passivation layer can be formed by an ion beam enhanced formation process. For example, ions or dopants within the ion beam can increase the propensity of surface silicon to react with one or more materials within the reactive gas, thereby forming the passivation layer as a result. The passivation layer can then act as a diffusion barrier to mitigate out diffusion during later fabrication steps and may mitigate particles or contaminants from being implanted into the target device(s). Surface reactions with previously deposited material or contaminants may be modified or enhanced as well.  
         [0036]     Another example of a suitable mechanism to reduce contamination is by employing the reactive gas for consuming particles or contaminants, such as carbon, that would otherwise be absorbed on the surface and driven into the material by the ion beam. The gas or components within the gas can react with the contaminants and form compounds that do not get implanted and/or can be swept away. For example, formation of volatile compounds or gaseous compounds can be readily pumped away or removed by a high vacuum system. This reduces or removes contaminants or particles that could be driven into target semiconductor device(s).  
         [0037]     The gas analyzer  206  is a residual gas analyzer that analyzes background gases present within the ion implantation chamber  212 . The gas analyzer  206  generates feedback or a feedback signal for the controller  204  to adjust or control the flow rate of the reactive gases or rate of introduction and/or the reactive gas composition so as to facilitate removal of the contaminants or particles from the ion beam and/or target surface. It is noted that alternate aspects can omit employment of the gas analyzer  206  and still be in accordance with the present invention.  
         [0038]     The controller  204  initially sets the reactive gas composition and flow rate according to process conditions, such as expected contaminant compositions and amount during a particular ion implantation process. The controller  204  adjusts the gas source  202  to supply the reactive gas and adjusts the valve  210  to control flow rate and/or composition of the reactive gas. The controller  204  receives and analyzes the generated feedback from the gas analyzer  206  during ion implantation and determines whether or not corrective adjustments are required. The controller  204  can then perform the corrective adjustments that facilitate removal of contaminants and mitigate contamination, such as by adjusting the reactive gas composition and/or by adjusting the flow rate of the reactive gas to obtain a desired pressure within the process chamber  212 .  
         [0039]      FIG. 3  is a block diagram depicting an interior of a process chamber  300  during an ion implantation process in which a gas, such as a reactive or atmospheric gas, is introduced to mitigate contamination in accordance with an aspect of the present invention. This diagram is presented to further illustrate interaction of the reactive gas with contaminants during ion implantation and is not intended to limit the invention to particular structures or arrangements.  
         [0040]     The process chamber  300  includes a target device support structure  302  that supports a target wafer  304 . The structure  302  can be a process disk for a batch ion implantation system or a single wafer holder for a single wafer ion implantation system. The target wafer  304  is undergoing an ion implantation process, such as one implanting p-type or n-type dopants to form active regions. The target wafer  304  can be at one of a number of stages of fabrication.  
         [0041]     A gas inlet or valve  306  controllably supplies a gas  310  to be in close proximity to the target wafer  304 . The gas  310 , such as an atmospheric or reactive gas, is typically supplied about or near a surface of the target wafer  304  wherein the ion beam  308  is in contact, in this example. The inlet  306  can control the amount or flow rate of the reactive gas  310  and may, in some aspects, control or adjust composition of the reactive gas. The ion beam  308  comprises selected dopants or ions to be implanted and has a beam energy and current density in order to obtain a desired depth and/or concentration for implant on the target wafer  304 . Generally, the ion beam  308  or surrounding portions of the process chamber  300  include unwanted particles or atomic contaminants. The gas  310  can mitigate contamination of the target wafer  304  by a number of mechanisms. One such mechanism is for the gas  310  to combine with the particles or contaminants to form compounds, which are then removed from the process chamber by, for example, a vacuum pump. Another mechanism is to form a passivation layer by an ion beam enhanced formation process that may also mitigate contamination of the target wafer  304  and also serves to facilitate diffusion during later fabrication processes. Other mechanisms that employ the gas  310  to mitigate contamination are also contemplated.  
         [0042]      FIG. 4  is a diagram of an ion implantation process modification system  400  in accordance with an aspect of the present invention. The system  400  is provided for exemplary purposes and modifies a current ion implantation process by introducing atmospheric and/or reactive gases during the ion implantation process for the modification and control of material properties resulting from the ion implantation process. The system  400  can be employed, for example, with single wafer ion implantation systems, batch ion implantation systems, plasma immersion ion implantation systems and the like.  
         [0043]     The system  400  includes a gas source or cylinder  404 , a process chamber  402 , and a chamber vacuum pump  416 . The gas source or cylinder  404  is a mechanism that controllably delivers gas, such as reactive or atmospheric gas, to the process chamber  402  through a controllable valve  408 . A gas source, such as a reservoir, or cylinder valve  406  is employed to control and/or adjust operation of the gas source or cylinder  404 . A flow mechanism  418 , such as a teflon line, connects the source valve  412  with a process chamber valve  408  and also with the gas source valve  406 .  
         [0044]     The process chamber valve  408  comprises one or more individual valves for selecting flow rate and composition of the gas ultimately provided to the process chamber. The valve  408  may be controlled by an external controller (not shown) or can be otherwise adjusted. The chamber valve  408  is generally set to adjust the flow rate and/or composition of the gas in order to facilitate removal of contaminants or particles and/or to mitigate contamination of a target semiconductor device (not shown) within the process chamber  402 .  
         [0045]     The process chamber  402  is part of an end station of an ion implantation system, which can be a single wafer and/or batch ion implantation system. The process chamber  402  holds or supports one or more target devices, such as target wafers, for ion implantation. An ion beam, generated as part of the ion implantation system, enters the process chamber  402  and implants dopants within the ion beam into the target device(s). Typically, the ion beam and/or the process chamber include undesired particles or contaminants that result in contamination of the target devices, as described above.  
         [0046]     The vacuum chamber pump  416  is connected to the process chamber  402  via a vacuum line  420  and removes air/gas from the process chamber  402  in order to obtain a selected or desired atmospheric pressure and to remove gases from the chamber  402 .  
         [0047]     The gas enters the process chamber  402  via the chamber valve  408  and interacts with the ion beam to mitigate contamination of the target device(s) by the particles or atomic contaminants. The gas can react with the contaminants in or about the target device by a number of mechanisms to reduce contamination, such as those described above, or modify the surface of the target.  
         [0048]     The chamber residual gas that can comprise at least a portion of the undesired particles or contaminants is then removed from the chamber by the vacuum pump  416  through the vacuum line  420 .  
         [0049]      FIG. 5  is a flow diagram depicting a method  500  for mitigating contamination of a target device by contaminants during ion implantation by introducing a gas, such as a reactive or atmospheric gas, near a surface of the target device in accordance with an aspect of the present invention. The method  500  can be employed in single and/or batch ion implantation systems.  
         [0050]     It is appreciated that the method  500 , as well as variations thereof, can be further appreciated with reference to other figures of the present invention. Additionally, the method  500  and description thereof can also be employed to facilitate a better understanding of other aspects of the invention described above.  
         [0051]     While, for purposes of simplicity of explanation, the method  500  is depicted and described as executing serially, it is to be understood and appreciated that the present invention is not limited by the illustrated order, as some aspects could, in accordance with the present invention, occur in different orders and/or concurrently with other aspects from that depicted and described herein. Moreover, not all illustrated features may be required to implement a methodology in accordance with an aspect the present invention.  
         [0052]     The method  500  begins at block  502  wherein an ion beam that may comprise contaminants is provided. The ion beam is provided, typically as part of an ion implantation system comprising an ion source, mass analyzer, and a beam line assembly. The ion beam undesirably can comprise contaminants, such as carbon contaminants, that could damage and/or alter a target device without interaction by a reactive gas. The contaminants can be introduced into the beam at various stages of the ion implantation system. The ion beam comprises one or more selected dopants at a selected energy with a selected beam current.  
         [0053]     A gas, such as an atmospheric or reactive gas, composition and flow rate are selected at block  504  according to process characteristics, such as expected contaminants. For example, a gas composition comprising oxygen or water vapor can be suitable for expected carbon contaminants. The flow rate is selected to obtain a desired pressure within the process chamber and permit interaction of the reactive gas and the contaminants.  
         [0054]     The gas is generated at block  506  according to the selected composition and/or flow rate. In one example, one or more gas sources and/or reservoirs can be present as well as a gas cylinder, evaporating system, and/or atmospheric inlet that comprise potential source gases. The gas cylinder contains a gas or vapor at a pressure high enough to provide a required gas flow to the process chamber through the controllable valve. The evaporating system is comprised of water or any other liquid or solid material to generate a reactive gas vapor. One or more valves can be employed to facilitate selection of composition and to also adjust the flow rate.  
         [0055]     The gas is directed toward an implant target location at block  508 . Tube(s), line(s) and/or hose(s) comprised of suitable materials can be employed to carry the reactive gas from gas source(s) to the process chamber. An inlet or valve within or a part of the process chamber can be employed to direct the reactive gas proximate to the implant target location of the target device, wherein the ion beam is impacting that target location.  
         [0056]     The gas reacts with the contaminants and/or mitigates contamination of the target location at block  510 . The gas can, in one example, combine with the contaminants and become volatile. Subsequently, the volatile compounds are removed by pumping. In another example, the gas creates a surface condition, such as a passivation layer, that prevents or mitigates particles from being implanted beyond or about the created surface condition.  
         [0057]      FIG. 6  is a flow diagram depicting a method  600  for mitigating contamination of a target device by contaminants during ion implantation by introducing a gas, such as a reactive or atmospheric gas, near a surface of the target device in accordance with an aspect of the present invention. The method  600  can be employed in single and/or batch ion implantation systems.  
         [0058]     It is appreciated that the method  600 , as well as variations thereof, can be further appreciated with reference to other figures of the present invention. Additionally, the method  600  and description thereof can also be employed to facilitate a better understanding of other aspects of the invention described above.  
         [0059]     While, for purposes of simplicity of explanation, the method  600  is depicted and described as executing serially, it is to be understood and appreciated that the present invention is not limited by the illustrated order, as some aspects could, in accordance with the present invention, occur in different orders and/or concurrently with other aspects from that depicted and described herein. Moreover, not all illustrated features may be required to implement a methodology in accordance with an aspect the present invention.  
         [0060]     The method  600  begins at block  602  wherein an ion beam that may comprise contaminants is provided. The ion beam may comprise contaminants, such as carbon contaminants, that could damage and/or alter a target device without interaction by a reactive gas. These contaminants can be introduced at various stages of an ion implantation system that provides the ion beam. The ion beam comprises one or more selected dopants at a selected energy and dose.  
         [0061]     An initial gas composition and flow rate are selected at block  604  according to process characteristics, such as expected contaminants. For example, a gas composition comprising oxygen or water vapor can be suitable for expected carbon contaminants. The flow rate is selected to obtain a desired pressure within the process chamber, permit interaction of the reactive gas and the contaminants, and remove volatile gases comprising the contaminants.  
         [0062]     The gas is generated at block  606  according to the selected composition and/or flow rate. One or more gas sources can be presented as a gas cylinder, evaporating system, and/or atmospheric inlet that comprise potential source gases. The gas cylinder contains a reactive gas or vapor at a pressure high enough to provide a required gas flow to the process chamber through the controllable valve. The evaporating system is comprised of water or any other liquid or solid material to generate a reactive gas vapor. One or more valves can be employed to facilitate selection of composition and to also adjust the flow rate.  
         [0063]     The gas is directed toward an implant target location at block  608 . Tube(s), line(s) and/or hose(s) comprised of suitable materials can be employed to carry the gas from gas source(s) to the process chamber. An inlet or valve within or a part of the process chamber can be employed to direct the gas proximate to the implant target location of the target device, wherein the ion beam is impacting that target location.  
         [0064]     The gas reacts with the contaminants and/or mitigates contamination of the target location at block  610 . The gas can, in one example, combine with the contaminants and become volatile. Subsequently, the volatile compounds are removed, for example, by pumping. In another example, the reactive gas creates a surface condition, such as a passivation layer, that prevents or mitigates particles from being implanted beyond or about the created surface condition.  
         [0065]     Gaseous partial pressures and composition are measured within the chamber at block  612 . A reactive gas analyzer is typically employed to measure the composition of the air/gas within the chamber. The measurements can include contaminants present, total partial pressure or vacuum, reactive gas present, and the like.  
         [0066]     If the measurements are outside of an acceptable range at block  614 , corrective adjustments for flow rate and composition of the gas are determined at block  616 . Additionally, the corrective adjustments can include a flow rate of exhaust gas from the process chamber.  
         [0067]     Then, the gas composition and flow rate corrective adjustments are applied at block  618 . Typically, the gas source and one or more controllable valves are employed to obtain the corrective adjustments. Subsequently, the method  600  returns to block  612  wherein new measurements are obtained.  
         [0068]     Although the invention has been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Additionally, the term “exemplary” is intended to indicate an example and not to indicate superior or best. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”