Abstract:
Provided is a fusion measurement apparatus which increases or maximizes the reliability of a measurement. The fusion measurement apparatus includes an atomic microscope for measuring a surface of a substrate at an atomic level, an electron microscope for measuring the atomic microscope and the substrate, and at least one electrode which distorts the path of a secondary electron on the substrate covered by a cantilever of the atomic microscope so that the secondary electron proceeds to an electron detector of the electron microscope.

Description:
TECHNICAL FIELD 
     The present invention disclosed herein relates to a measurement apparatus, and in more detail, to a measurement apparatus including an atomic force microscope capable of measuring a surface of a substrate on an atomic scale and an electron microscope capable of observing the surface of the substrate and the atomic force microscope on an electronic scale. 
     BACKGROUND 
     An atomic force microscope (AFM) may measure atomic scales by scanning a surface of a substrate using a probe. The probe may scan the surface of the substrate by using a contact method, a non-contact method, or an intermittent contact method. The AFM may provide an image of a change in position of the probe ascending and descending. Additionally, the AFM may be applied to measure a friction force, a magnetic property, an electric property, an electrochemical property, and electric capacity of the surface of the substrate. Generally, the probe of the ATM may be easily worn or damaged. Interaction between the surface of the substrate and the AFM may be observed by using an electron microscope. A state of the probe of the AFM may be in-situ monitored by using the electron microscope. 
     DISCLOSURE OF THE INVENTION 
     Technical Problem 
     The present invention provides an atomic force microscope (AFM) whose cantilever together with a substrate therebelow may be monitored by using an electron microscope. The present invention also provides a measurement apparatus capable of accurately observing interaction between a cross section of a substrate and a probe of an AFM. 
     Technical Solution 
     According to an embodiment of the inventive concept, there is provided a measurement apparatus including an atomic force microscope (AFM) including a probe scanning a surface of a substrate and a cantilever, an electron microscope including a body tube emitting an electron beam to the AFM and the substrate and an electron detector detecting secondary electrons generated from the substrate due to the electron beam, and at least one distortion unit distorting a path of the secondary electrons emitted from the substrate to be forwarded to the electron detector while the AFM and the substrate are being monitored by using the electron microscope. In this case, the electron microscope may obtain a distinct image of the probe and a cross section of the substrate by vertically emitting the electron beam to the probe of the AFM and the cross section of the substrate. Accordingly, the electron microscope may allow an observer to accurately observe interaction between the cross section of the substrate and the probe. 
     The distortion unit may include an electrode distorting the path of the secondary electrons by using an electric field. 
     The electrode may include an anode charged by a positive charge attracting the secondary electrons by gravitation. 
     The electrode may be formed on an opposite side of the electron gun body tube facing the electron detector. 
     The electrode may be formed on a surface of a terminal of the body tube of the electron microscope. When the path of the secondary electrons is distorted by using the electrode, the path of the incident electron beam having high energy of 1 to 30 kV may be bent due to the electrode. 
     The distortion unit may further include a plurality of permanent magnets distorting the path of the secondary electrons by using a magnetic field. In this case, since the plurality of permanent magnets induces the magnetic field to compensate an effect of the electric field induced by the electrode, the path of the electron beam having the high energy may be maintained. In this case, the secondary electrons having low energy of 50 eV or less may hardly receive the effect of the magnetic field. 
     The plurality of permanent magnets may be disposed on a front and a rear of a plane formed by the electron detector, the body tube, and facing different poles of the plural permanent magnets in opposition. 
     According to another embodiment of the inventive concept, there is provided a measurement apparatus including an AFM including a scanner transferring a substrate, a probe scanning a surface of the substrate transferred by the scanner, and a cantilever fastening the probe and an electron microscope including a body tube vertically emitting an electron beam to a plane formed by a cross section of the substrate and the probe of the AFM and an electron detector detecting secondary electrons generated from the substrate due to the electron beam emitted by the body tube. 
     The measurement apparatus may include at least one distortion unit distorting a path of the secondary electrons emitted from the substrate to be forwarded to the electron detector while the AFM and the substrate are being monitored by using the electron microscope. 
     The distortion unit may include an electrode distorting the path of the secondary electrons by using an electric field. 
     The distortion unit may further include a plurality of permanent magnets distorting the path of the secondary electrons by using a magnetic field. 
     As described above, according to the embodiments, a surface of a substrate below a cantilever may be measured by using a distortion unit distorting a path of secondary elections emitted from the substrate hidden by the cantilever to be forwarded to an electron detector of an electron microscope. 
     Also, since distinct images of a cross section of the substrate and a probe of an atomic force microscope (AFM) may be obtained by allowing electron beams to be vertically incident thereinto, interaction between the cross section of the substrate and the probe may be accurately observed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating a measurement apparatus according to an embodiment of the inventive concept; 
         FIGS. 2 and 3  are views illustrating a distortion unit of  FIG. 1 ; 
         FIG. 4  is a perspective view illustrating an atomic force microscope (AFM) of  FIG. 1 ; 
         FIG. 5  is a schematic view illustrating the measurement apparatus from which an electrode shown in  FIG. 2  is removed; 
         FIG. 6  is a photo of an electron microscope, illustrating a substrate hidden by a cantilever; 
         FIG. 7  is a photo of the electron microscope, illustrating a state in which a cross section of the substrate and a probe are not vertical to an electronic beam; 
         FIGS. 8A and 8B  are photos of the electron microscope, illustrating a state in which the cross section of the substrate and the probe are vertical to electronic beams; 
         FIGS. 9A to 9F  are views sequentially illustrating a state in which a measurement defect of the AFM is monitored by using the electron microscope in the measurement apparatus; 
         FIG. 10  is a photo of the electron microscope, illustrating a state in which a surface of the substrate is scanned while a tip of the probe is being damaged; and 
         FIG. 11  illustrates double dips shown in a direction in which the tip of the probe is damaged in a lateral force microscope. 
     
    
    
     DETAILED DESCRIPTION 
     A measurement apparatus includes an atomic force microscope (AFM) including a probe for scanning a surface of a substrate and a cantilever, an electron microscope including a body tube emitting electron beams to the AFM and the substrate and an electron detector detecting secondary electrons generated by the substrate, and at least one distortion unit distorting a path of the secondary electrons emitted from the substrate to be forwarded to the electron detector while monitoring the AFM and the substrate by using the electron microscope. In this case, the electron microscope vertically emits the electron beams to the probe of the AFM and a cross section of the substrate, thereby obtaining distinct images of the probe and the cross section of the substrate. Accordingly, the electron microscope may allow an observer to accurately observe interaction between the cross section of the substrate and the probe. 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. Advantages and features of the present invention and a method of achieving the same will be specified with reference to the embodiments that will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described below and may be embodied in different forms. The embodiments that will be described hereafter are provided to allow the disclosure to be thoroughgoing and perfect and to allow a person skilled in the art to fully understand the scope of the present invention. The present invention is defined only by the scope of following claims. Through the entire specification, like reference numerals designate like elements. 
     Terms used in the specification are to describe the embodiments but not to limit the scope of the present invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. Also, as just exemplary embodiments, reference numerals shown according to an order of description are not limited to the order. 
       FIG. 1  is a schematic view illustrating a measurement apparatus  100  according to an embodiment of the inventive concept, and  FIGS. 2 and 3  are views illustrating a distortion unit  40  of  FIG. 1 . 
     As shown in  FIGS. 1 to 3 , the measurement apparatus  100  may include at least one distortion unit  40  distorting a path of secondary electrons  35  emitted from a substrate  10  hidden by a bottom or a periphery of a cantilever  26  of an atomic force microscope (AFM)  20  to be forwarded toward an electron detector  34  of an electron microscope  30  when to monitor a measurement state of the AFM  20  by using the electron microscope  30 . 
     In this case, the distortion unit  40  may change a progress direction, that is, the path of the secondary electrons  35  generated from the substrate  10 . The distortion unit  40  may include at least one of an electrode  42  and a plurality of permanent magnets  44 . The electrode  42  may change the path of the secondary electrons  35  into an electric field. On the other hand, the permanent magnet  44  may change the path of the secondary electrons  35  into a magnetic field. The secondary electrons  35  may be detected by the electron detector  34  of the electron microscope  30  without being blocked or seized by the cantilever  26  due to the electric field or the magnetic field. 
     Accordingly, the measurement apparatus  100  may monitor a surface of the substrate  10  below the cantilever  26  of the AFM  20  by using the electron microscope  30 . 
     The AFM  20  may measure a condition of the surface of the substrate  10  on an atomic scale. The AFM  20  may measure the surface of the substrate  10  supported by a scanner  22  by using a probe  24  formed on the cantilever  26 . The scanner  22  may precisely transfer the substrate  10  located below the probe  24 . Also, the scanner  22  may precisely transfer the probe  24  above the substrate  10 . For example, the scanner  22  may include piezoelectric ceramics transferred along an X-axis or a Y-axis or oscillating according to electric signals. The scanner  22  may operate in a way of linear scanning, that is, raster. The scanner  22  passes a first line while scanning the same, returns to an original location, moves vertically by one column, and passes second, third, and nth lines repetitively, thereby entirely scanning a desired two-dimensional area. 
     The cantilever  26  is connected to a cantilever driving unit  23 . The cantilever  26  may be bent according to ascending or descending of the probe  24  to scan according to the scanner  22 . The cantilever  26  may have an elastic coefficient lower than a coupling elastic coefficient between atoms of the substrate  10 , for example, 10 N/m. The cantilever  26  to which a contact type probe  24  of is connected may have an elastic coefficient smaller than the cantilever  26  to which a non-contact type probe  24  is connected. Also, the cantilever  26  to which the non-contact type probe  24  is connected may oscillate with a resonant frequency from about several tens kHz to about several hundreds kHz. Accordingly, the cantilever  26  to which the non-contact type probe  24  is connected may have higher horizontal resolution and stability as the elastic coefficient becomes greater. For example, the cantilever  26  may be formed as a triangular shape to be horizontal to the substrate  10 . The cantilever  26  may be formed as one of a single crystal silicon film and a silicon nitride film. 
     The probe  24  may be formed to protrude and to be sharpened at a terminal of the cantilever  26 . For example, the probe  24  may be manufactured by micro-machining and may be connected to the cantilever  26 . The probe  24  may scan while being in contact or not in contact with the surface of the substrate  10  transferred by the scanner  22 . The substrate  24  may be formed as one of a pyramidal shape, a tetrahedral shape, and a conical shape. The contact type probe  24  may have a tip rounder than that of the non-contact type probe  24 . 
     The electron microscope  20  may detect a change of a location of the probe  24  ascending and descending by using an optical method. The AFM  20  may include a laser unit  27  emitting a laser beam  25  to the cantilever  26  on the probe  24  and a light sensor  28  detecting the laser beam  25  reflected from the cantilever  26 . 
     For example, the laser beam  25  may be shown as an arrow as shown in  FIG. 4  illustrating the AFM  20 .  FIG. 4  is a perspective view illustrating the AFM  20  of  FIG. 1  in more detail. The laser beam  25  generated by the laser unit  27  may pass a reflector  29  and may be incident into the cantilever  26  and then may be reflected toward the light sensor  28  The cantilever  26  may be connected to a driving unit in a direction in which the laser beam  25  is reflected toward the light sensor  28 . The reflector  29  may change a path of the laser beam  25  from the laser unit  27  to the cantilever  26 . The scanner  22  may transfer a location of the substrate by using an X-axis driving unit  21   a , a Y-axis driving unit  21   b , and a Z-axis driving unit  21   c . The substrate  10  may be fastened to a terminal of the scanner  22  and may be scanned through a transfer of the scanner  22 . Accordingly, the AFM  20  may continuously detect changes of the location of the probe  24  ascending and descending, corresponding to changes of an angle of reflection of the laser beam  25 . 
     The AFM  20  may be monitored together with the substrate  10  by the electron microscope  30 . The electron microscope  30  may detect and image the secondary electrons  35  generated by injecting an electron beam  33  in a two-dimensional direction. The electron microscope  30  may monitor the substrate  10  and the probe  24  and the cantilever  26  of the AFM  20  in a chamber  36  pumped to a vacuum degree more than a certain value to prevent scattering of the electron beam  33  and the secondary electrons  35 . For example, the chamber  36  may be pumped to a low vacuum or a high vacuum of about 10-3 torr. The electron microscope  30  may include an electron gun body tube  32  emitting the electron beam  33  to the substrate  10  and the probe  24  and the cantilever  26  of the AFM  20  and the electron detector  34  for detecting the secondary electrons  35  generated from the substrate  10 , the probe  24 , and the cantilever  26 . Accordingly, the electron microscope  30  may obtain images corresponding to the substrate  10 , the probe  24 , and the cantilever  26  by using detection signals of the secondary electrons  35 . 
     The electron gun body tube  32  may focus the electron beam  33  from the outside onto the substrate  10  and the probe  24  and the cantilever  26  of the AFM  20  to scan. The electron gun body tube  32  may include a source generating the electron beam  33  and at least one condenser lens for focusing the electron beam  33 . Also, the electron gun body tube  32  adjusts a speed of the electron beam  33  by using an attenuator, thereby adjusting magnification. A depth of focus of the electron beam  33  may be determined by a final aperture of the electron gun body tube  32 . When a radius of the final aperture becomes smaller, the depth of focus may increase. 
     The electron detector  34  may detect the secondary electrons  35  generated from the substrate  10 , the probe  24 , and the cantilever  26  exposed toward the electron beam  33 . The electron detector  34  may include a first anode charged to be a positive charge attracting the secondary electrons  35  by gravitation. The secondary electrons  35  may be emitted from a surface of a material exposed toward the electron beam  33 . Accordingly, the secondary electrons  35  are surface-emission electrons whose real shape may not be recognized. However, as shown in  FIGS. 1 and 2 , the secondary electrons  35  may be detected by the electron detector  34  as an electron flux or as a secondary electron beam. 
     The secondary electrons  35  may include backscattered electrons. The electron detector  34  may include an SE electron detector, a backscattered electron detector, or a negative emission electron detector. The electron detector  34  may be disposed on the periphery of the electron gun body tube  32  to detect the secondary electrons  35 . The electron detector  34  may detect the secondary electrons  35  while moving along the electron beam  33  of the electron gun body tube  32 . The electron detector  34  may continuously detect the secondary electrons  35  and may convert the same into electric signals while moving together with the electron gun body tube  32 . Accordingly, the electron microscope  30  may output a moving picture by using a display device. 
     The electron microscope  30  may monitor the surface of the substrate  10  and the probe  24  and the cantilever  26  of the AFM  20  in real time. For example, the electron microscope  30  may measure not only a condition of the surface of the substrate  10  but also a damage or destruction of the probe  24  of the AFM  20  in real time. The electron microscope  30  may monitor the surface of the substrate  10  measured by the probe  24  and the cantilever  26  of the AFM  20  in real time. Images obtained by the electron microscope  30  and the AFM  20 , respectively, may be compared with each other. 
     Also, the electron microscope  30  may monitor the surface of the substrate  10  by detecting the secondary electrons  35  generated from the surface of the substrate  10  hidden by the bottom of the cantilever  26 . The secondary electrons  35  have a negative charge. The number or energy of the secondary electrons  35  may be detected by the electron detector  34  to be different according to a kind and a shape of the surface of the substrate  10 . The path of the secondary electrons  35  hidden by the cantilever  26  of the AFM  20  may be distorted by the electrode  42  to be detected by the electron detector  34 . 
     The distortion unit  40  may prevent the secondary electrons  35  generated from the surface of the substrate  10  from being blocked or seized by the cantilever  26 . The electrode  42  of the distortion unit  40  may be disposed between a part emitting the secondary electrons  35  and the electron detector  34 . The electrode  42  may be a second anode attracting the secondary electrons  35  by gravitation. The secondary electrons  35  may return in a direction of being emitted from the electron gun body tube  32 . However, the electron beam  33  and the secondary electrons  35  have the same negative charge. The electron beam  33  and the secondary electrons  35  may be forwarded respectively with a certain angle. The electrode  42  may distort the secondary electrons  35  to reduce the angle between the electron beam  33  and the secondary electrons  35 . A voltage applied to the second anode may be smaller than a voltage applied to the first anode. 
     Accordingly, for example, the electrode  42  may be disposed on an opposite side of the electron gun body tube  32  facing the electron detector  34 . When the electron gun body tube  32  and the electron detector  34  are close to each other, the electrode  42  may be formed on a surface of a terminal of the electron gun body tube  32 . The electrode  42  may be disposed to be close to the aperture of the electron gun body tube  32 . Although the electron detector  34  for detecting the secondary electrons  35  and the electrode  42  are shown in  FIG. 2 , the electron gun body tube  32  may be disposed in a location opposite to the electrode  42  facing the electron detector  34 . 
     The plurality of permanent magnets  44  may be disposed on both front and rear sides of a plane formed by the electron detector  34 , the electron gun body tube  32 , and the electrode  42 . Different polarities of permanent magnets  44  are facing etch other. The plurality of permanent magnets  44  may include a dipole inducing a magnetic field in a direction vertical to the path of the secondary electrons  35 . The magnetic field induced by the plurality of permanent magnets  44  may change the path of the secondary electrons  35  by a Lorentz force. For example, the plurality of permanent magnets  44  may be disposed to induce the magnetic field from the front to the rear of the plane of the path of the secondary electrons  35 . The permanent magnets  44  having a north polar may be disposed on the front of the plane of the path of the secondary electrons  35 , and the permanent magnets  44  having a south polar may be disposed on the rear thereof. 
     Accordingly, since the secondary electrons  35  generated from the substrate  10  hidden by the cantilever are distorted by an electric field or a magnetic field to be forwarded toward the electron detector  34 , the apparatus  100  may monitor the substrate  10  hidden below the cantilever  26 . 
       FIG. 5  is a schematic view illustrating the measurement apparatus  100  from which the electrode  42  is removed. The secondary electrons  35  generated from the substrate  10  below the cantilever  26  may be blocked or seized by the cantilever  26  on the periphery of the probe  24 . In this case, the cantilever  26  may hide the surface of the substrate  10  therebelow while the probe  24  is scanning the surface of the substrate  10 . Accordingly, a shadow  50  may be shown on the substrate  10  below the cantilever  26  as shown in  FIG. 6 . 
       FIG. 6  is a photo of the electron microscope  30 , illustrating the substrate  10  hidden by the cantilever  26 . When the electrode  42  is not used, since some of the secondary electrons  35  are not detected from the substrate  10  below the cantilever  26 , the shadow  50  is shown. In this case, the shadow  50  may be shown because the number of the secondary electrons  35  detected from the substrate  10  below the cantilever  26  decreases. The shadow  50  may be removed by the electrode  42  distorting the secondary electrons  35  emitted from the substrate  10  below the cantilever  26 . 
     Accordingly, the measurement apparatus  100  may measure the surface of the substrate  10  hidden by the cantilever  26  by using the electrode  42  distorting the path of the secondary electrons  35 . 
     On the other hand, the electron microscope  30  may more accurately show the states of the substrate  10  and the probe  24  when the substrate  10  and the probe  24  are separated from the electron gun body tube  32  with the same distance. That is, the electron microscope  30  may obtain an image illustrating the interaction between the substrate  10  and the probe when a plane formed by the substrate  10  and the probe  24  is vertical to the electron beam  33 . Accordingly, the electron microscope  30  may obtain a distinct image when the substrate  10  and the probe  24  are separated from the electron gun body tube  32  with the same distance. For example, the electron microscope  30  allows the electron beam  33  to be vertically incident into a plane formed by a cross section  14  of the substrate  10 , the probe  24 , and the cantilever  26 , thereby showing states of the probe  24  and the cross section  14  of the substrate  10  as an image. The cross section  14  of the substrate  10  may include a side of the substrate  10  whose horizontal plane or level surface is made to stand or split. 
       FIG. 7  is a photo of the electron microscope  30 , illustrating a state in which the cross section  14  of the substrate  10  and the probe  24  are not vertical to the electron beam  33 . When the cross section  14 , for example, the side of the substrate  10  and the probe  24  are not on the same plane, that is, when the cross section  14  of the substrate  10  and the probe  24  have different focal depths from each other, the electron microscope  30  may not provide a distinct image of all the substrate  10  and the probe  24  in one scene. For example, the electron microscope  30  allows the electron beam  33  to be slantly incident into the cross section  14  and the level surface, for example, a top surface of the substrate  10 , thereby obtaining an image in which a boundary line between the cross section  16  and the level surface  16  of the substrate  10  having focal depths different from the probe  24  distinctly shown. Accordingly, when the substrate  10  and the probe  24  are separated from the electron gun body tube  32  of the electron microscope  30  with the same distance and are not vertical to the electron beam  33 , interaction between the AFM  20  and the substrate  10  may be difficult to be monitored by the measurement apparatus  100 . 
       FIGS. 8A and 8B  are photos of the electron microscope  30 , illustrating a state in which the cross section  14  of the substrate  10  and the probe  24  are vertical to the electron beam  33 . When the cross section  14  of the substrate  10  and the probe  24  are on the same plane and the plane is vertical to the electron beam  33 , the measurement apparatus  100  may obtain an image distinctly showing all the cross section  14  of the substrate  10  and the probe  24 . In this case, the photos of the electron microscope  30  show a state in which the substrate  10  and the probe  24  are separated from each other and a state in which the substrate  10  and the probe  24  are in contact with each other. The probe  24  connected to the cantilever  26  may be close to the surface of the substrate  10 . The probe  24  may scan along a pattern  12  formed on the substrate  10 . The tip of the probe  24  may be transferred along the pattern  12  of the substrate  10 . 
     The tip of the probe  24  may not scan all the surface of the substrate  10 . For example, when an inclination angle of the probe  24  moving along the surface of the substrate  10  is smaller than an inclination angle of the pattern  12 , a side of the probe  24  may scan a top of the pattern  12 . 
       FIGS. 9A to 9F  are views sequentially illustrating a state in which a measurement defect of the AFM  20  is monitored by using the electron microscope  30  in the measurement apparatus  100 . 
     Referring to  FIGS. 9A to 9F , the measurement apparatus  100  may obtain an image by using the electron microscope  30 , the image in which the side of the probe  24  scans the top of the pattern  12  formed on the substrate  10 . Also, the electron microscope  30  may show inclined planes of the probe  24  and the pattern  12  as an image. When the inclined plane of the probe  24  is smaller than the inclined plane of the pattern  12 , the side of the probe  24  may scan the top of the pattern. As shown in  FIGS. 9C ,  9 D, and  9 E, in the case of the AFM  20 , when the side of the probe  24  scans the top of the pattern  12 , a measurement defect may occur. Accordingly, the measurement apparatus  100  may monitor the measurement defect of the AFM  20  by using the electron microscope  30 . 
       FIG. 10  is a photo of the electron microscope  30 , illustrating a state in which the surface of the substrate  10  is scanned while a tip  60  of the probe  24  is being damaged. The measurement apparatus  100  may monitor a damage of tip  60  of the probe  24  of the AFM  20  by using the electron microscope  30  in real time. In this case, in the case of the AFM  24 , when scanning in a direction in the tip of the probe  24  is damaged, the measurement defect such as a double dip may occur. 
       FIG. 11  is a view illustrating double dips  70  shown in the direction in which the tip  60  of the probe  24  is damaged in a lateral force microscope. When the AFM  20  scans the pattern  12  of the surface of the substrate  10  by using the probe  24  with the damaged tip  60 , the double dips  70  may be shown. The double dips  70  may indicate that a damaged part of the probe  24  is separated from the surface for a short time while making an ascent of the inclined plane of the pattern  12 . Accordingly, the electron microscope  30  may allow an observer to recognize a state of the damage of the probe  24  of the AFM  20  and a shape of the measurement defect caused thereby. 
     Accordingly, since the measurement apparatus  100  may monitor a measurement state of the AFM  20  by using the electron microscope  30 , measurement reliability may be increased. 
     While one or more embodiments of the present invention have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. Therefore, it will be understood that the embodiments described above are just exemplary but not limitative in all aspects.