Abstract:
Provided are a head having improved usability by limiting a movement range of a laser spot and an atomic force microscope having the same. 
     A head according to an exemplary embodiment of the present disclosure is a head measuring bending of a cantilever by using a laser beam reflected on the surface of the cantilever in order to acquire information on a sample surface by using a tip of the cantilever. The head includes: a spot moving means configured to move a laser spot so as to position the laser spot on the surface of the cantilever; and a movement limiting means configured to limit a movement range of the laser spot moved by the spot moving means in a predetermined range.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 10-2014-0188493 filed on Dec. 24, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to a head and an atomic force microscope having the same, and more particularly, to a head having improved usability by limiting a movement range of a laser spot and an atomic force microscope having the same. 
         [0004]    2. Description of the Related Art 
         [0005]    A scanning probe microscope (SPM) represents a microscope that measures a surface characteristic of a sample and shows the measured surface characteristic as a 3D image while making a minute probe manufactured through an MEMS process scan the surface of the sample. The scanning probe microscope may be subdivided into an atomic force microscope (AFM), a scanning tunneling microscope (STM), and the like according to a measurement method. 
         [0006]      FIG. 1  is a schematic perspective view of an atomic force microscope in which an XY scanner and a Z scanner in the related art and  FIG. 2  is a schematic conceptual diagram of a head used in the atomic force microscope having a structure of  FIG. 1 . 
         [0007]    Referring to  FIG. 1 , the atomic force microscope  10  is configured to include a cantilever  2  following the surface of a measurement target  1  in a contact or non-contact state, an XY scanner  11  scanning the measurement object in X and Y directions on an XY plane, a Z scanner  21  connected with the cantilever  2  to move the cantilever  2  in a Z direction with a comparatively small displacement, a Z stage  12  moving the cantilever  2  and the Z scanner  21  in the Z direction with a relatively large displacement, and a fixing frame  13  fixing the XY scanner  11  and the Z scanner  12 . 
         [0008]    The atomic force microscope  10  acquires an image such as topography, or the like by scanning the surface of the measurement object  1  with the cantilever  2 . Relative movement of the surface of the measurement object  1  and the cantilever  2  may be performed by the XY scanner  11  and the cantilever  2  may be vertically moved by the Z scanner  21  so as to follow the surface of the measurement object  1 . 
         [0009]    Meanwhile, the cantilever  2  and the Z scanner  21  are connected by a probe arm  22  and a head  20  including the probe arm  22  and the Z scanner  21  is not explicitly illustrated in  FIG. 1 . 
         [0010]    Referring to  FIG. 2 , the head  20  is configured to serve to measure a motion (for example, a bending degree) of the cantilever  2  by using a laser system and provide the measurement motion to a controller (not illustrated). 
         [0011]    The head  20  has a laser beam generating unit  23  irradiating a laser beam and the laser beam generating unit  23  irradiates the laser beam to a mirror  24  fixed to an intermediate body  28 . The laser beam is directly reflected by the mirror  24  and thereafter, passes through a hole formed in the intermediate body  28  to be reflected on the top surface of the cantilever  2  again. The reflected laser beam is again reflected by a steering mirror  25  to focus on a beam detecting device  26 . Herein, as the beam detecting device  26 , a position sensitive photo detector (PSPD) is primary used and the laser spot is positioned at the center of the PSPD, and as a result, measurement preparation is completed. The Z scanner  21  is controlled based on a signal detected by the beam detecting device  26 . The beam detecting device  26  may be installed to be fixed to a housing  30  of the head  29  and a detailed layout relationship is omitted for easy description. 
         [0012]    In order to position the laser spot at the center of the beam detecting device  26 , first, focusing the laser spot on the top surface of the cantilever  2  needs to be preceded. A user manually adjusts the laser spot to be positioned on the top surface of the cantilever  2  by operating control knobs  27 A and  27 B as a spot moving means while visually verifying whether the laser spot is positioned on the top surface of the cantilever  2  by using a vision system (not illustrated) which may view the top of the cantilever  2 . Control knobs  27 A and  27 B changes a slope of the intermediate body  28  supporting the mirror  24  to change a path of the laser beam. For example, the control knob  27 A may cause movement of the laser spot in a width direction of the cantilever  2  and the control knob  27 B may cause movement of the laser spot in a longitudinal direction of the cantilever  2 . 
         [0013]    A location area (hereinafter, referred to as ‘spot area’) of the laser spot which is adjustable by the control knobs  27 A and  27 B is widely designed by reflecting an assembly tolerance, and the like in order to accommodate cantilevers  2  having various sizes. 
         [0014]    However, the widely designed spot area brings about inconvenience for use. The user focuses the laser spot on the top surface of the cantilever  2  by adjusting the control knobs  27 A and  27 B again at the time of changing the cantilever  2  and since the spot area is large, the laser spot is frequently lost in the vision system. Users which are not familiar to the device unnecessarily consumes a lot of time to position the laser spot on the top surface of the cantilever  2  to feel inconvenience for use. 
       SUMMARY 
       [0015]    The present disclosure has been made in an effort to provide a head having improved usability by limiting a movement range of a laser spot and an atomic force microscope having the same. 
         [0016]    An exemplary embodiment of the present disclosure provides a head measuring bending of a cantilever by using a laser beam reflected on the surface of the cantilever in order to acquire information on a sample surface by using a tip of the cantilever. The head includes: a spot moving means configured to move a laser spot so as to position the laser spot on the surface of the cantilever; and a movement limiting means configured to limit a movement range of the laser spot moved by the spot moving means in a predetermined range. 
         [0017]    According to another feature of the present disclosure, the spot moving means may have a knob and a screw forming unit and move the laser spot by a linear motion of an end by rotation of the knob. The movement limiting means may limit the rotation of the knob to a predetermined range. 
         [0018]    According to yet another feature of the present disclosure, the movement limiting means may be a projection which is projected on the outer periphery of the spot moving means, and a hook unit may be formed so as to hook the projection. 
         [0019]    According to still another feature of the present disclosure, the movement limiting means may be attachable to the spot moving means, the movement limiting means may have the projection which is projected on the outer periphery thereof, and the hook unit may be formed so as to hook the projection. 
         [0020]    According to still yet another feature of the present disclosure, the movement limiting means may limit a positionable area of the laser spot, and the movement limiting means may be mounted on the spot moving means so that a target point of the surface of a predetermined cantilever is positioned at the center of the positionable area of the laser spot. 
         [0021]    Another exemplary embodiment of the present disclosure provides an atomic force microscope including a head having the above configuration. 
         [0022]    According to exemplary embodiments of the present disclosure, a head and an atomic force microscope having the same can easily position a laser spot on the surface of a cantilever by limiting a movement range of the laser spot to a predetermined range to provide high usability and convenience. 
         [0023]    The effects of the present disclosure are not limited to the aforementioned effects, and other effects, which are not mentioned above, will be apparent to a person having ordinary skill in the art from the following description. 
         [0024]    The objects to be achieved by the present disclosure, the means for achieving the objects, and effects of the present disclosure described above do not specify essential features of the claims, and, thus, the scope of the claims is not limited to the disclosure of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0026]      FIG. 1  is a schematic perspective view of an atomic force microscope in which an XY scanner and a Z scanner are separated in the related art; 
           [0027]      FIG. 2  is a schematic conceptual diagram of a head used in an atomic force microscope having a structure of  FIG. 1 ; 
           [0028]      FIG. 3  is a conceptual diagram schematically illustrating a laser spot adjustment mechanism provided in the head of the general atomic force microscope; 
           [0029]      FIG. 4  is a schematic perspective view schematically illustrating a limiting means and a hook unit; and 
           [0030]      FIG. 5  is a schematic top view for describing operations of the limiting means and the hook unit of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    The advantages and features of the present disclosure, and methods of accomplishing these will become obvious with reference to examples to be described below in detail along with the accompanying drawings. However, the present disclosure is not limited to the exemplary embodiments set forth below, and may be embodied in various other forms. The present exemplary embodiments are for rendering the description of the present disclosure complete and are set forth to provide a complete understanding of the scope of the disclosure to a person with ordinary skill in the technical field to which the present disclosure pertains, and the present disclosure will only be defined by the scope of the claims. 
         [0032]    When an element or layer is referred to as being “on” another element or layer, it may be directly on the other element or layer, or intervening elements or layers may be present. 
         [0033]    Although the terms “first”, “second”, and the like are used for describing various components, these components are not confined by these terms, of course. These terms are merely used for distinguishing one component from the other components. Therefore, a first component to be mentioned below may be a second component in a technical concept of the present disclosure, of course. 
         [0034]    Throughout the whole specification, the same reference numerals denote the same elements. 
         [0035]    Since size and thickness of each component illustrated in the drawings are represented for convenience in explanation, the present disclosure is not necessarily limited to the illustrated size and thickness of each component. 
         [0036]    The features of various embodiments of the present disclosure can be partially or entirely bonded to or combined with each other and can be interlocked and operated in technically various ways as can be fully understood by a person having ordinary skill in the art, and the embodiments can be carried out independently of or in association with each other. 
         [0037]    Hereinafter, a head and an atomic force microscope according to the present disclosure will be described with reference to the accompanying drawings. 
         [0038]      FIG. 3  is a conceptual diagram schematically illustrating a laser spot adjustment mechanism provided in the head of the general atomic force microscope.  FIG. 4  is a schematic perspective view schematically illustrating a limiting means and a hook unit.  FIG. 5  is a schematic top view for describing operations of the limiting means and the hook unit of  FIG. 4 . 
         [0039]    Prior to detailed description, in regard to components illustrated in  FIGS. 3 to 5 , it should be noted that only components associated with components that serve to adjust a laser spot to be positioned on the top surface of a cantilever are illustrated among various components provided in the head of the atomic force microscope. Components (for example, a component that positions a laser beam reflected on the top surface of the cantilever at the center of a beam detecting device, a component of a Z scanner, and the like) other than the components illustrated in  FIGS. 3 to 5  may follow a known constitution of the head of the atomic force microscope. For example, other components may follow the constitutions of  FIGS. 1 and 2  or follow a constitution of a head of a completely different type atomic force microscope. 
         [0040]    Referring to  FIG. 3 , a mirror  24  is positioned to be attached onto an intermediate body  28 . Herein, an optical path may be formed by using a known prism instead of the mirror  24 . 
         [0041]    A laser beam generating unit  23  irradiates a laser beam (expressed by dotted lines) toward the mirror  24 . The laser beam reflected on the mirror  24  is irradiated downward. The laser beam generating unit  23  is fixed so as not to be relatively displaceable from the intermediate body  28  and the mirror  24 . That is, the laser beam generating unit  23  is not relatively movable with respect to the mirror  24 . 
         [0042]    Spot moving means  27 A and  27 B are provided to change the optical path of the laser beam reflected on the mirror  24  and irradiated downward. One corner portion of the intermediate body  28  is fixed to a housing ( 30  of  FIGS. 2 and 4 ) of the head in such a way that it is rotatable (illustrated as part P in  FIG. 3 ) and the spot moving means  27 A and  27 B are positioned to point-contact corner portions other therethan. 
         [0043]    A spring (not illustrated) provides elastic force in a +Z direction to the intermediate body  28  in order to maintain a contact state of the intermediate body  28  and the spot moving means  27 A and  27 B. Each of the spot moving means  27 A and  27 B has a knob  27   a  and a screw forming unit  27   b  which become handles and the screw forming unit  27   b  is spirally coupled to the housing  30  of the head, and as a result, the spot moving means  27 A and  27 B may vertically move by rotating the knob  27   a.    
         [0044]    The spot moving means  27 A vertically moves by the rotation to rotate the intermediate body  28  around an X axis, thereby causing the laser spot to move in a Y direction. Further, the spot moving means  27 B vertically moves by the rotation to rotate the intermediate body  28  around a Y axis, thereby causing the laser spot to move in an X direction. 
         [0045]    Referring to  FIGS. 4 and 5 , a movement limiting means  40  further added to the head  20  having the constitutions of  FIGS. 2 and 3  will be described in detail. 
         [0046]    The movement limiting means  40  limits the spot moving means  27 A and  27 B so that the laser spot moves only within a predetermined range. The movement limiting means  40  has a hollow  41  so that the knob  27   a  fits the hollow  41  from the top of the knob  27   a.  The movement limiting means  40  is preferably detachable to the spot moving means  27 A and  27 B as illustrated in  FIG. 4  and details will be described below. 
         [0047]    Meanwhile, the hollow  41  is closed upward and opened downward in the exemplary embodiment, but is not limited thereto and may be formed to be opened even upward. 
         [0048]    When the movement limiting means  40  fits in the knob  27   a  of the spot moving means  27 A or  27 B, the spot moving means  27 A and  27 B rotates by rotating the movement limiting means  40 . That is, the movement limiting means  40  and the spot moving means  27 A and  27 B are fixed to each other. A fixing scheme may be variously set and for example, the movement limiting means  40  and the spot moving means  27 A and  27 B may be fixed to each other by engagement of a projection and a slit formed on an inner periphery of the movement limiting means  40  and an outer periphery of the knob  27   a , respectively and a screw hole is formed to penetrate the side of the movement limiting means  40  and a set screw is inserted into the screw hole and fastened to fix the movement limiting means  40  and the knob  27   a.  Besides, the movement limiting means  40  and the knob  27   a  are mixed by various schemes. 
         [0049]    A projection  42  is provided on an outer periphery of the movement limiting means  40 . The projection  42  is a portion which is projected so as to have a rotary radius larger than a rotary radius of the outer periphery of the movement limiting means  40 . The projection  42  is formed to be hooked by the hook unit  31  formed in the housing  30  of the head. 
         [0050]    Referring to  FIG. 5 , rotation of the spot moving means  27 A and  27 B is limited by physical interference between the projection  42  and the hook unit  31 . The spot moving means  27 A and  27 B may rotate at R° and R° may be adjusted based on a design by the width of the projection  42 , the size of the hook unit  31 , and the like. Meanwhile, unlike this, two or more hook units  31  are provided to limit the spot moving means  27 A and  27 B or the shape of the hook unit  31  is adjusted to limit the spot moving means  27 A and  27 B. 
         [0051]    Since a pitch of the screw forming unit  27   b  of the spot moving means  27 A or  27 B is predetermined, when a desired R° is determined, a vertical movement width of the spot moving means  27 A or  27 B is determined. When the vertical movement width is determined, a distance at which the laser spot moves may also be determined by calculation. Since the distance at which the laser spot moves varies depending on various design criteria (that is, the distance may vary depending on a positional relationship between a fixing unit P and the spot moving means  27 A or  27 B, and the like), the distance may be appropriately selected. 
         [0052]    Hereinafter, a method that installs the movement limiting means  40  in the spot moving means  27 A and  27 B will be described. 
         [0053]    The movement limiting means  40  limits a positionable area of the laser spot and the movement limiting means  40  is preferably mounted on the spot moving means  27 A and  27 B so that a target point of the surface of the cantilever which is predetermined is positioned at the center of the positionable area of the laser spot. 
         [0054]    First, the head  20  is mounted on a cantilever which becomes a reference (is predetermined) and thereafter, the laser spot is positioned on the top surface of the cantilever  2  by adjusting the spot moving means  27 A and  27 B. Herein, the cantilever which becomes the reference is preferably a cantilever which is frequently used. 
         [0055]    Thereafter, as illustrated  FIG. 5 , the movement limiting means  40  is fixed to the spot moving means  27 A and  27 B so that the projection  42  of the movement limiting means  40  is positioned at an opposite location to the hook unit  31 . That is, the projection  42  is configured to be positioned at the center of an area where the spot moving means  27 A and  27 B is rotatable. As a result, the laser spot may move only with a limited distance in the X direction and the Y direction around the target top surface of the cantilever. 
         [0056]    When the cantilever which becomes the reference is changed or a movement area of the laser spot needs to be changed by a predetermined cause (for example, abrasion of a portion which contacts the spot moving means  27 A or  27 B, or the like) again, the above operation may be performed again. 
         [0057]    When the movement limiting means  40  is mounted as described above, by limiting the movement range of laser spot, the location of the laser spot may be predicted with to some degree, and as a result, use convenience increases. 
         [0058]    Further, the movement limiting means  40  is detachable to enable resetting depending on a situation. However, that that movement limiting means  40  is formed in the spot moving means  27 A or  27 B itself is not excluded should be noted. In this case, the movement limiting means  40  may be a projection which is projected on the outer periphery of the spot moving means  27 A or  27 B. That is, as illustrated in  FIG. 4 , the projection  42  is not formed in the movement limiting means  40  and the projection may be integrally formed on the surface of the knob  27   a.    
         [0059]    Meanwhile, when another cantilever completely different from the cantilever which becomes the reference is used, the movement limiting means  40  may be removed from the spot moving means  27 A and  27 B and the existing method may be used. That is, the movement limiting means  40  is detachable to cope with various situations, and as a result, usability of equipment increases. 
         [0060]    Constitutions other than the above constitution may follow constitutions of heads and atomic force microscopes of XE Series, NX series, and the like of Park Systems Inc. which is an applicant of the present patent. However, the present disclosure is not limited thereto. 
         [0061]    The exemplary embodiments of the present disclosure have been described above with reference to the accompanying drawings, but those skilled in the art will understand that the present disclosure may be implemented in another specific form without changing the technical spirit or an essential feature thereof. Therefore, the aforementioned exemplary embodiments are all illustrative and are not restricted to a limited form.