Abstract:
An apparatus to control an ion beam includes a scanner configured in an first state to scan the ion beam wherein the scanner outputs the ion beam as a diverging ion beam; a collimator configured to receive along a side of the collimator the diverging ion beam and to output the diverging ion beam as a collimated ion beam; a beam adjustment component that extends proximate the side of the collimator; and a controller configured to send a first signal when the scanner is in the first state to the beam adjustment component to adjust ion trajectories of the diverging ion beam from a first set of trajectories to a second set of trajectories.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 61/894,069, filed Oct. 22, 2013. 
     
    
     FIELD 
       [0002]    The present embodiments relate to ion beam apparatus, and more particularly, to component to control ion beams in beamline ion implanters. 
       BACKGROUND 
       [0003]    In the present day, ion implanters are often constructed to optimize implantation according to a specific set of applications. In current applications, for example, some beamline ion implanters are configured to generate high current ribbon beams in which the beam cross section that intercepts a substrate is defined by a beam width that is much greater than the beam height. 
         [0004]    For other ion implantation applications, it may be preferable to use a spot beam ion beam in which the beam height and beam width are more equal. One advantage afforded by spot beam ion implantation is the better control of dose uniformity afforded by spot beams. The local ion dose concentration can be modified by adjusting the speed of the ion beam along the direction of spot beam scanning This can be accomplished under computer control in a manner that allows the spot beam scanning to be carefully controlled to optimize ion dose uniformity. 
         [0005]    In the present day it is common to perform ion implantation using ribbon beams in an ion implanter that is dedicated to ribbon beam implantation and to perform spot beam ion implantation in a dedicated spot beam ion implanter. In part this is because several adjustments to a beamline implanter may be required in present day apparatus in order to switch the same ion implanter between ribbon beam and spot beam operating modes. For one, an ion source may be switched to change the type of ion beam generated. In addition, in order to operate in a spot beam mode, a scanner is employed to scan the spot beam before impinging on the substrate in order for the ion spot beam to cover an entire substrate, which is often much larger in size than the spot beam cross section. However, when an ion implanter is operated in a ribbon beam mode in which the width of the ribbon beam is sufficient to cover a substrate such a scanner is superfluous. 
         [0006]    Moreover, in conventional ion implanters the geometry for collimation of a spot beam before reaching a substrate differ from that of a ribbon beam. This is because of the different configuration of beamline components that are employed to provide an ion beam to a collimator. In the case of a ribbon beam, after exiting a mass resolving slit where the ribbon beam is focused, the ribbon beam may diverge from the mass resolving slit until being received by a collimator, which form a collimated ion beam that is directed to the substrate being processed. In the case of a spot beam, after exiting a mass resolving slit the spot beam first enters a scanner that generates an oscillating deflection of the spot beam in order to generate a diverging ion beam envelope before entering the collimator. Accordingly, in a given beamline a collimator that is configured to collimate a ribbon beam may be unsuitable in that configuration for collimating a spot beam. For this reason it is common practice for a ribbon beam ion implanter to be employed for certain ion implantation steps or for certain substrates, such as high dose implantation, while a separate spot beam ion implanter is employed for other ion implantation steps that require better dose control. It is with respect to these and other considerations that the present improvements have been needed. 
       SUMMARY 
       [0007]    This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter. 
         [0008]    In one embodiment, an apparatus to control an ion beam includes a scanner configured in an first state to scan the ion beam wherein the scanner outputs the ion beam as a diverging ion beam. The apparatus may include a collimator configured to receive along a side of the collimator the diverging ion beam and to output the diverging ion beam as a collimated ion beam; a beam adjustment component that extends proximate the side of the collimator; and a controller configured to send a first signal when the scanner is in the first state to the beam adjustment component to adjust ion trajectories of the diverging ion beam from a first set of trajectories to a second set of trajectories. 
         [0009]    In a further embodiment a method a method to control an ion beam includes sending a first signal to activate a scanner configured to scan the ion beam to form a diverging ion beam having a first divergence angle; and sending a second signal to a beam adjustment component to adjust the diverging ion beam to form a second divergence less than the first divergence angle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  depicts a top plan view in block form of a ion implanter according to the present embodiments; 
           [0011]      FIG. 2  depicts a top view of an exemplary architecture consistent with various embodiments; 
           [0012]      FIG. 3  depicts a ribbon beam implementation of the architecture of  FIG. 2 ; 
           [0013]      FIG. 4  depicts a spot beam implementation of the architecture of  FIG. 2 ; 
           [0014]      FIG. 5A and 5B  depicts details of the scenario of  FIG. 4  from two different perspectives; and 
           [0015]      FIG. 6  depicts details of the scenario of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some embodiments are shown. The subject matter of the present disclosure, however, may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout. 
         [0017]    The embodiments described herein provide an ion implanter having novel set of control elements to control geometry of spot beams. In various embodiments beam adjustment components are provided in or adjacent to a collimator to adjust the angle of scanned spot beams provided to a substrate. The control elements may include control rods, multipole elements, control coils, and other features. 
         [0018]    In various embodiments, the ion implanter may be operated in two different modes: a spot beam mode and a ribbon beam mode. In the ribbon beam mode, the collimator may be set to adjust the angles the diverging ribbon beam to form a collimated beam by a main collimator magnet. In addition, other beam adjustment components, such as rods or multipoles may adjust ion beam uniformity of the ribbon beam. As detailed below, in a spot beam mode, the same beam adjustment components associated with a collimator may be adjusted to correct trajectories of the scanned spot beam according to the different geometry of the scanned spot beam as compared to the ribbon beam. 
         [0019]      FIG. 1  depicts a top plan view in block form of an ion implanter  100  according to the present embodiments. The ion implanter  100  includes an ion source  102  used to generate ions, analyzer magnet  104 , vacuum chamber  106 , scanner  108 , collimator  110 , and substrate stage  112 . The ion implanter  100  is configured to generate an ion beam  120  and deliver the ion beam  120  to a substrate  114 . For simplicity, the ion beam  120  is depicted merely as a central ray trajectory of the ion beam. In various embodiments, the ion source  102  may be an indirectly heated cathode (IHC) ion source, an RF ion source, a microwave ion source or other ion source. The analyzer magnet  104  may alter the trajectory of ions extracted from the ion source  102  as in conventional analyzer magnets. The vacuum chamber  106  may include a mass resolving slit (not shown in  FIG. 1 ) which may function as a conventional mass resolving slit to screen out ions of undesired mass. In various embodiments the scanner  108  may be a magnetic scanner or an electrostatic scanner. The collimator  110  may be a magnetic collimator to function at least to generate a collimated ion beam to be conducted to the substrate  114 . The ion implanter  100  may include other beamline components including apertures, dithering components, acceleration/deceleration lenses, each of whose operation is well known. For clarity, further discussion of such components is omitted herein. 
         [0020]    As further illustrated in  FIG. 1  the ion implanter  100  includes a collimation controller  116  whose function is at least to adjust trajectories of ions during the collimation process. Further details of operation of the collimation controller  116  are disclosed with respect to the figures to follow. However, in brief, the collimation controller  116  may adjust signals sent to beamline components associated with the collimator  110 , such as beam adjustment components discussed below. During ribbon beam mode, signals sent to beam adjustment components may be used to adjust ion beam uniformity of a ribbon beam that is collimated by a magnet of the collimator. During the spot beam mode, the same beam adjustment components may be used to adjust the trajectories of a scanned spot beam. 
         [0021]    For convenience in the discussion to follow, different coordinate systems are employed to describe operation of the present embodiments as shown in  FIG. 1 . At the scanner  108  a first Cartesian coordinate system whose components are labeled Y, Xsc, and Zsc, is used. At the substrate  114  a second Cartesian coordinate system whose components are labeled Y, Xs, and Zs, is used. In each coordinate system, the Y-axis is the same absolute direction. The Z-axis for the different coordinate systems is in each case along the direction of central ray trajectory of ion beam propagation at a particular point. Thus, the absolute direction of the Zsc axis differs from that of Zs. Similarly Xsc differs from Xs. 
         [0022]    In some embodiments, the ion implanter  100  may operate in both ribbon beam and spot beam modes. In various embodiments, the ribbon beam may have a relatively smaller aspect ratio defined by a ratio of ion beam height to ion beam width in a plane that is generally perpendicular to the direction of propagation of the ion beam. For a ribbon beam this ratio may be less than one third and is in some examples less than one tenth. For example, a ribbon beam provided to the substrate  114  whose ions have trajectories along the Zs axis may have a width along the Xs axis of about 300 to 400 mm and a height along the Y axis of about 20 mm at the substrate  114 . The embodiments are not limited in this context. In various embodiments, the spot beam may have a relatively larger aspect ratio such as greater than ½ and in some cases greater than one. For example, a spot beam provided to the substrate  114  may have a width along the Xs axis of about 20 mm and a height along the Y axis of about 30 mm. The embodiments are not limited in this context. It is to be noted that the aforementioned spot beam dimensions apply to the instantaneous dimension of a spot beam, and that the overall treatment area of a scanned spot beam may be the same or similar to that of a ribbon beam. 
         [0023]    Because the ion implanter  100  may operate in either ribbon beam or spot beam mode, the ion implanter  100  provides convenience and process flexibility for processing substrates when a succession of implantation operations for a set of substrates or for different sets of substrates requires different implantation modes. This avoids the requirement to direct substrates to be processed by ribbon beam ion implantation or spot beam ion implantation to a respective ion implanter dedicated for ribbon beam or spot beam implantation. 
         [0024]    When a ribbon beam mode is set for the ion implanter  100  a ribbon beam may be generated at the ion source  102  and focused at an MRS (not shown) provided within the vacuum chamber  106 . In ribbon beam mode the scanner  108  may remain in a first state, which may be an inactive state, and may transmit the ribbon beam unperturbed. The ribbon beam may then fan out as it propagates into the collimator  110 . The collimator  110  and adjacent components may be set to provide collimation to such a ribbon beam. As such the collimator  110  may be set to collimate a diverging beam having a focal plane at the MRS. 
         [0025]    In the present embodiments, ion implanter  100  may also be operated in spot beam mode by placing the scanner in a second state, which may be an active state. In the second state the scanner  108  may be active so that a spot beam emerging from the vacuum chamber  106  is scanned by a deflection field oriented along the Xsc axis, such that the ion trajectories fan out over a range of angles before entering the collimator  110 . Consistent with the present embodiments, and as detailed below, the collimation controller  116  may generate signals that are sent to the beam adjustment component  118  in a manner that adjusts trajectories of ions entering the collimator  110 . This allows the ion implanter  100  to be operated in spot beam mode without having to add extra optical components. Such extra components may be otherwise necessary to adjust for the different location of the scanner and mass resolving slit with respect to the collimator  110 , which generate different ion beam envelopes for the respective ribbon beam and spot beam modes. 
         [0026]      FIG. 2  depicts a top view of an exemplary collimation architecture  200  consistent with various embodiments. In the example shown in  FIG. 2  a portion of an ion implanter is shown. As shown in  FIG. 2 , a mass resolving slit (MRS)  204  is disposed upstream of the scanner  108 . In this architecture the scanner  108  is disposed in the beamline in a manner that a ribbon beam or spot beam that exits the mass resolving slit  204  may pass through the scanner  108 . In one implementation, the collimator controller  116  may send signals to activate or deactivate the scanner  108  depending upon whether a ribbon beam or spot beam is to pass through the scanner  108 . However, in other scenarios, other beamline devices (not shown) may activate or deactivate the scanner  108 . 
         [0027]    As shown in  FIG. 2  a beam adjustment component  206  is provided adjacent the collimator  110 . In some embodiments, more than one beam adjustment component  206  may be provided, in locations both upstream and downstream with respect to the collimator  110 . Referring also briefly to  FIGS. 3 and 4 , a beam adjustment component  206  extends along the Xsc direction proximate to a side  208  of the collimator that is configured to receive a diverging ion beam. In various embodiments the beam adjustment component  206  may be configured to control ion beam uniformity of a ribbon beam. This may be adjusted by generating a field or fields from the beam adjustment component  206  that locally or selectively deflect ions within a region or regions of the ribbon beam. In one such example, the beam adjustment component may include a pair of steel bars that are each encircled along their axes with multiple current coils that are individually controlled so that varying amounts of current may be supplied in loops that are positioned along the length (Xsc axis) of the beam adjustment component  206  where the direction of current flow in loops may be generally parallel to the Zsc and Y axis as shown in  FIG. 2 . In this manner local magnetic field variations may be induced at different points along the Xsc axis to selectively deflect ions locally to adjust the ion beam uniformity as the ion beam  202  enters the collimator  110 . 
         [0028]      FIG. 3  depicts one scenario for operation of the architecture  200 . In  FIG. 3 , the ion implanter is operated in ribbon beam mode such that a ribbon beam  302  passes through the mass resolving slit  204 . Although not shown in  FIG. 3 , the ribbon beam  302  may form a converging beam as it propagates toward the mass resolving slit  204  from the ion source  102 . The ribbon beam  302  may converge to form a source at the mass resolving slit  204  and subsequently diverge from the mass resolving slit  204  as it propagates to the collimator  110  as shown. In this scenario a scanner  108  is disposed in the beamline downstream to the mass resolving slit  204  such that the ribbon beam  302  passes through the scanner  108 . The scanner  108  may be positioned so as not to block ions that form a diverging beam from the mass resolving slit  204 . Moreover, because the scanner  108  is not active, the trajectories of the ions of ribbon beam  302  may pass through the scanner  108  unaltered by the scanner  108 . The ribbon beam  302  thus propagates from the scanner  108  as a diverging beam that is intercepted by the collimator  110 . As a result, in the ribbon beam mode the collimator  110  may be set to collimate the ribbon beam  302  based upon a first source location  407  at the mass resolving slit  204  as if the scanner  108  were not present. 
         [0029]      FIG. 4  depicts another scenario in which the architecture  200  is operated in a spot beam mode. In this example, a spot beam  402  passes through the mass resolving slit  204  and enters the scanner  108 . The scanner  108  is activated by collimator controller  116  so that the spot beam  402  is scanned as it passes through. In different embodiments, the scanner  108  may be an electrostatic scanner or a magnetic scanner. In any of these embodiments the scanner  108  may generate an oscillating deflecting field that is applied to the spot beam  402  as it travels through the scanner  108  with an initial direction of propagation parallel to the Zsc axis. In order to deflect the spot beam  402  the deflecting field (not shown) may be applied perpendicularly to the Zsc axis, in a back and forth manner along directions parallel to the Xsc axis. 
         [0030]    This results in the generation of a set of diverging trajectories of ion beams that are directed to the collimator  110  from a second source location  408  positioned within the scanner  108  as the spot beam  402  is scanned. Over time, the spot beam  402  forms a diverging ion beam that has an ion beam envelope  404  as shown. In this scenario the ions of the spot beam  402  fan out from the second source location  408  within the scanner  108 . This second source location  408  is downstream of the plane  406  of the mass resolving slit  204  that contains the first source location  407 . Because of this, the trajectories of ions in the ion beam envelope  404  that enter the collimator  110  are different than those of the ribbon beam  302 , which emerges from the mass resolving slit  204 . In this scenario, the collimator controller  116  sends signals to the beam adjustment component  206  to adjust the angles of the trajectories of ions within the ion beam envelope  404  as the ions enter into the collimator  110 . 
         [0031]      FIGS. 5A and 5B  depict details of the ion beam geometry proximate the collimator  110  for the scenario of  FIG. 4 . As illustrated in  FIG. 5A , the ion beam envelope  404  may be more divergent than the trajectories of adjusted ion beam envelope  502  that enter the collimator  110 . In particular, a divergence angle  508  of the ion beam envelope  404  is larger than a divergence angle  506  defined by the adjusted ion beam envelope  502  as shown by the dotted lines. Thus, the adjusted ion beam envelope  502  may be said to be more convergent that the ion beam envelope  404  that exists before passing proximate the beam adjustment component  206 . 
         [0032]    Notably, the trajectories of adjusted ion beam envelope  502  may more closely match trajectories of ions of a ribbon beam than the trajectories of the ion beam envelope  404 , and the divergence angle  506  of the adjusted ion beam envelope  502  may more closely match that of a ribbon beam discussed below with respect to  FIG. 6 . To accomplish this, as shown in  FIG. 5B , the intensity of a field  504  may be varied along the length of the beam adjustment component  206 . In the view of  FIG. 5B  the perspective is facing downstream toward the collimator  110  (not shown). As the ion beam envelope  404  passes proximate the beam adjustment component  206  the ion beam envelope  404  experiences a varying field strength of the field(s)  504 , as indicated by the size of the arrows representing the field. Notably, this field  504  may have the effect of deflecting the ions of ion beam envelope  404  in the direction parallel to the Xsc axis. In the example of  FIG. 5B , the strength of the field(s)  504  may be systematically increased by the beam adjustment component  206  from its center to periphery on either end in order to generate larger deflection for ion trajectories on the outside of the ion beam envelope  404 . When received by a collimator  110 , the resulting adjusted ion beam envelope  502  may be more similar in shape and size to that of ribbon beam  302  that the ion beam envelope  404 , rendering collimation of the ion beam envelope  502  simpler. 
         [0033]      FIG. 6  depicts details of the ion beam geometry proximate the collimator  110  for the scenario of  FIG. 3 . As illustrated, the diverging ribbon beam  602  has trajectories that originate from the mass resolving slit  204  and define a divergence angle  604 . In the ribbon beam mode, the beam adjustment component  206  may be reconfigured to adjust beam uniformity of the ribbon beam  602 , but not to alter the trajectories in the manner performed in  FIG. 5  for the spot beam  402 . These trajectories of ribbon beam  602  may therefore more closely match the trajectories of adjusted ion beam envelope  502  after the ions that form the ion beam envelope  404  are altered by the beam adjustment component  206 , and the divergence angle  604  may more closely match the divergence angle  506  than the divergence angle  508 . In particular, in order to adjust beam uniformity local fields may be adjusted at at least one location along the Xsc direction by the beam adjustment component  206 . However, this may not be performed in a manner to systematically alter ion beam trajectories to affect divergence angle as describe above with respect to  FIGS. 5A ,  5 B. 
         [0034]    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 in the tended to fall within the scope of the present disclosure. Furthermore, 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. Thus, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.