Patent Publication Number: US-10319563-B2

Title: Electronic beam machining system

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an electronic beam machining (EBM) system and a photolithography method based on electronic beam. 
     2. Description of Related Art 
     Electronic beam machining (EBM) is a method to treat a workpiece by heat generated by the electron beam having high power density. The electronic beam machining can be used to for surface heat treatment, welding, etching, drilling, melting, or material sublimation. 
     The electrons emitted from the scorching cathode filament in a vacuum are accelerated at high voltage in a range from about 30 KV to about 200 KV and focused by the electromagnetic lens to form the electron beam having a power density in a range from about 105 W/cm 2  to about 109 W/cm 2 . The electron beam generates the heat at high temperature so that the workpiece is melted or sublimated. Thus, the welding, etching, or drilling can be performed on the workpiece. However, the conventional electronic beam machining system usually has one electron gun and can emit a single electron beam. Thus, the conventional electronic beam machining system has lower efficiency. If multiple electron guns are used, the electronic beam machining system would be complicated and have a high cost. 
     Therefore, there is room for improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a schematic section view of one embodiment of an electronic beam machining system. 
         FIG. 2  is a schematic section view of a transmission spot and a plurality of diffraction spots. 
         FIG. 3  is a schematic section view of one embodiment of a diffraction unit. 
         FIG. 4  is a schematic section view of one embodiment of a conductor shield. 
         FIG. 5  is a schematic diagram of electron diffraction of one embodiment when an electron beam passes through two-dimensional (2D) nanomaterial or three-dimensional (3D) nanomaterial. 
         FIG. 6  shows a transmission and diffraction image of one embodiment of a single-layered single crystal graphene sheet. 
         FIG. 7  shows a transmission and diffraction image of one embodiment of a three-layered single crystal graphene sheets. 
         FIG. 8  shows a transmission and diffraction image of one embodiment of a large area polycrystalline graphene sheet. 
         FIG. 9  shows a transmission and diffraction image of one embodiment of a single-layered single crystal MoS 2  sheet. 
         FIG. 10  shows a flowchart of one embodiment of a photolithography method. 
         FIG. 11  is a schematic section view of another embodiment of an electronic beam machining system. 
         FIG. 12  is a Scanning Electron Microscope (SEM) image of two cross-stacked drawn carbon nanotube films. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale, and the proportions of certain parts may be exaggerated better illustrate details and features. The description is not to considered as limiting the scope of the embodiments described herein. 
     Several definitions that apply throughout this disclosure will now be presented. The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “outside” refers to a region that is beyond the outermost confines of a physical object. The term “inside” indicates that at least a portion of a region is partially contained within a boundary formed by the object. The term “substantially” is defined to essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series and the like. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. In general, the word “module,” as used herein, refers to logic embodied in hardware or firmware, or to a collection of software instructions, written in a programming language, such as, for example, Java, C, or assembly. One or more software instructions in the modules may be embedded in firmware, such as an EPROM. It will be appreciated that modules may comprise connected logic units, such as gates and flip-flops, and may comprise programmable units, such as programmable gate arrays or processors. The modules described herein may be implemented as either software and/or hardware modules and may be stored in any type of computer-readable medium or other computer storage device. 
     References will now be made to the drawings to describe, in detail, various embodiments of the present electronic beam machining system, and a photolithography method using the electronic beam machining system. The electronic beam machining system can be an electron beam lithography system, electron beam welding system, electron beam drilling system, electron beam melting system or electron beam heating system. 
     Referring to  FIG. 1 , an electronic beam machining system  10  of one embodiment is provided. The electronic beam machining system  10  is an electron beam lithography system and comprises a vacuum chamber  11 , an electron emitter  12 , a controlling gate  13 , an accelerating electrode  14 , a focus electrode  15 , a holder  16 , a control computer  17 , and a diffraction unit  18 . 
     The electron emitter  12 , the controlling gate  13 , the accelerating electrode  14 , the focus electrode  15 , the holder  16 , and the diffraction unit  18  are located inside of the vacuum chamber  11 . The electron emitter  12  is used to emit an electron beam. The electron beam can be accelerated by the accelerating electrode  14  and focused by the focus electrode  15  to form an incident electron beam  22  to radiate the diffraction unit  18 . The diffraction unit  18  includes a two-dimensional nanomaterial. The incident electron beam  22  transmits the two-dimensional nanomaterial to form a transmission electron beam  26 , and a plurality of diffraction electron beams  24 . The transmission electron beam  26  and the plurality of diffraction electron beams  24  radiate and etch the object  20  fixed on the holder  16  to form a transmission spot  29  and a plurality of diffraction spots  27  as shown in  FIG. 2 . The holder  16  is configured to fix the object  20  and can be designed according to need. In one embodiment, the holder  16  is a stage. The plurality of diffraction spots  27  is arranged to form a diffraction ring. The control computer  17  is used to control the electronic beam machining system  10 . 
     The vacuum chamber  11  is connected to a pumping device (not shown). In of one embodiment, the pumping device includes an ion pump, a first molecular pump, a second molecular pump, a mechanical pump, and a control unit. The ion pump and the second molecular pump are respectively connected to the vacuum chamber  11 . The first molecular pump is connected to the vacuum chamber  11  via a pre-vacuum chamber. The mechanical pump is respectively connected to the first molecular pump and the second molecular pump. The control unit is configured to control the work of the vacuum pumping device. The pressure of the vacuum chamber  11  can be kept at a range from about 10 −3  Pa to about 10 −8  Pa. 
     The electron emitter  12  and the holder  16  are spaced from each other and located on two opposite ends of the vacuum chamber  11 . The controlling gate  13 , the accelerating electrode  14 , the focus electrode  15 , and the diffraction unit  18  are located between the electron emitter  12  and the holder  16 . The electron emitter  12  can include a hot cathode electron source or a field emission cold cathode electron source. 
     The electron emitter  12 , the controlling gate  13 , the accelerating electrode  14 , and the focus electrode  15  form an electron gun. The electron beam  22  provided by the electron gun can have energy in a range from about 0.2 KeV to about 200 KeV, a current in a range from about 0.01 microamperes to about 10 milliamperes, and a spot diameter in a range from about 1 micrometer to about 6 millimeters. In the electron beam lithography system, the incident electron beam  22  provided by the electron gun can have a lower energy and a spot diameter in a range from about 1 nanometer to about 100 micrometers. In the electron beam welding system, the electron beam drilling system, the electron beam melting system, or the electron beam heating system, the incident electron beam  22  provided by the electron gun can have a higher energy and a larger spot diameter. The electron gun can also be a laminar gun. The laminar gun can have a more uniform spot and greater current density. 
     In one embodiment, the electronic beam machining system  10  can include a moving platform (not shown) configured to move the electron gun to scan the object  20 . In one embodiment, the electronic beam machining system  10  can include a deflection electrode (not shown) configured to move the incident electron beam  22  to scan the object  20 . 
     In one embodiment, the diffraction unit  18  can also be connected to a power supply, supplied with an electric potential, and used to accelerate the incident electron beam  22 . Thus, the accelerating electrode  14  is optional. In one embodiment, diffraction unit  18  is connected to an external circuit to conduct away the electrons absorbed by the two-dimensional nanomaterial of the diffraction unit  18 . 
     Referring to  FIG. 3 , the diffraction unit  18  includes a supporter  180 , a grid  182 , and a two-dimensional nanomaterial  184 . The supporter  180  is configured to support and fix the grid  182  and the two-dimensional nanomaterial  184 . The shape and the size of the supporter  180  are not limited and can be designed according to need. In one embodiment, the supporter  180  is a metal sheet, such as a copper plate, having a central through hole  181 . The size of the central through hole  181  is smaller than the grid  182 . The grid  182  is located on the supporter  180  and covers the central through hole  181 . The shape and the size of the grid  182  are not limited and can be designed according to need. The grid  182  can be a copper mesh or a carbon nanotube structure. In one embodiment, as shown in  FIG. 12 , the grid  182  includes two drawn carbon nanotube films stacked with each other. The drawn carbon nanotube film includes a plurality of carbon nanotubes orderly arranged and spaced from each other. The aligned directions of the carbon nanotubes between adjacent stacked drawn carbon nanotube films is about 90 degrees. Thus, parts of the two-dimensional nanomaterial  184  are suspended on a hole between adjacent carbon nanotubes. The drawn carbon nanotube film is an ultra thin, sparse porous structure and has little effect on the two-dimensional nanomaterial  184 . Furthermore, because the primary diffraction spot of the drawn carbon nanotube film is formed by the diffraction that occurs between the adjacent wall of the carbon nanotubes, and has a low angle, the drawn carbon nanotube film would not influence the diffraction spots of the two-dimensional nanomaterial  184 . The two-dimensional nanomaterial  184  can cover the grid  182 . The two-dimensional nanomaterial  184  can be graphene sheet or MoS 2  sheet. Furthermore, the electronic beam machining system  10  can include a moving device to move the diffraction unit  18  along XYZ directions. Thus, the distance D between the two-dimensional nanomaterial  184  and the object  20  is adjustable. 
     Furthermore, the electronic beam machining system  10  can include a conductor shield  19  and used to shield the transmission spot  29  and/or at least one of the plurality of diffraction spots  27  and allow the rest of the transmission spot  29  and the plurality of diffraction spots  27  to pass through. The shape and the size of the conductor shield  19  can be designed according to need. The conductor shield  19  can be a conductive rod or conductive plate. In one embodiment, the conductor shield  19  is a conductive rod having a first end and a second end opposite to the first end. The first end of the conductive rod is fixed on the inner wall of the vacuum chamber  11 . The conductive rod is rotatable and can be rotated to be between the two-dimensional nanomaterial  184  and the object  20 . The conductor shield  19  is connected to an external circuit to conduct away the electrons absorbed by the conductor shield  19 . In one embodiment, both the conductor shield  19  and the two-dimensional nanomaterial of the diffraction unit  18  are connected to the same external circuit. The electronic beam machining system  10  can also include a Faraday cup (not shown) so that only a single diffraction beam can be obtained to radiate the object  20 . 
     Referring to  FIG. 4 , in one embodiment, the conductor shield  19  includes a first conductive rod  190  having a first end fixed on the inner wall of the vacuum chamber  11  and a second end opposite to the first end; a first conductive plate  191  fixed on the second end; six second conductive rods  192  connected to the first conductive plate  191 ; and six second conductive plates  193  respectively connected to the six second conductive rods  192 . The first conductive plate  191  is configured to shield the transmission spot  29 . The second conductive plates  193  are configured to shield the plurality of diffraction spots  27 . The second conductive rods  192  are rotatable around the first conductive plate  191  so that any two of the second conductive plates  193  can be overlapped with each other. The number of the second conductive rods  192  and the second conductive plates  193  are the same and can be selected according to the pattern of the diffraction ring of the plurality of diffraction spots  27 . 
     The control computer  17  includes a calculating module and a distance controlling module. The calculating module is configured to calculate the distance D between the two-dimensional nanomaterial  184  and the object  20  according to the lattice period d of the two-dimensional nanomaterial  184  and the radius R of diffraction ring. The distance controlling module is configured to adjust the distance D between the two-dimensional nanomaterial  184  and the object  20 . 
     The two-dimensional nanomaterial, especially, two-dimensional nanomaterial only having a single layer of atoms with different electron diffraction principles. The difference between the conventional electron diffraction of three-dimensional nanomaterial and the electron diffraction of two-dimensional nanomaterial is described below. 
     Referring to  FIG. 5 ( a ) , the electron diffraction of the two-dimensional nanomaterial satisfies the condition d sin θ=λ, wherein d represents the lattice period of the two-dimensional nanomaterial, θ represents the angle between the diffraction electron beam  24  and the transmission electron beam  26 . Referring to  FIG. 5 ( b ) , the electron diffraction of the three-dimensional nanomaterial satisfies the condition 2d′ sin θ′=λ, wherein d′ represents the interplanar spacing of the three-dimensional nanomaterial, θ′ represents the angle between the incident electron beam  22  and the crystal surface  28  of the three-dimensional nanomaterial. In the conventional electron diffraction of three-dimensional nanomaterial, the angle between the diffraction electron beam  24  and the transmission electron beam  26  is 2θ′. Usually, in selected area electron diffraction, the θ or θ′ is much small and satisfies the condition θ≅sin θ≅tan θ or θ′≅sin θ′ tan θ′. Thus, in the electron diffraction of the two-dimensional nanomaterial, it satisfies the condition d sin θ≅d θ=λ, however, in the conventional electron diffraction of three-dimensional nanomaterial, it satisfies the condition 2d′ sin θ′≅2d′θ′=d′2θ′=λ. 
     The lattice period d of the two-dimensional nanomaterial  184  and the wavelength λ of the incident electron beam  22  can be stored in or obtained by the control computer  17 . The radius R of diffraction ring can be obtained according to the desired etching pattern. Referring to  FIG. 2 , along the same crystal direction, the diffraction electron beam  24  form a plurality of diffraction spots  27  on the object  20 , and the transmission electron beam  26  form a transmission spot  29  on the object  20 . The distance between the diffraction spot  27  and the transmission spot  29  is equal to the radius R of diffraction ring. Thus, the distance D between the two-dimensional nanomaterial  184  and the object  20  can be calculated according to the formulas d sin θ≅dθ=λ and sin θ=R/(D 2 +R 2 ) 1/2 . 
     The number of the diffraction electron beams  24  and the pattern of the diffraction ring formed by the diffraction electron beams  24  can be adjusted by selecting the two-dimensional nanomaterial  184 .  FIG. 6  shows a transmission and diffraction image when the incident electron beam  22  entirely cover and passes through a single-layered single crystal graphene sheet.  FIG. 7  shows a transmission and diffraction image when the incident electron beam  22  entirely cover and passes through a three-layered single crystal graphene sheets.  FIG. 8  shows a transmission and diffraction image when the incident electron beam  22  entirely cover and passes through a large area polycrystalline graphene sheet.  FIG. 9  shows a transmission and diffraction image when the incident electron beam  22  entirely cover and passes through a single-layered single crystal MoS 2  sheet. 
     Referring to  FIG. 10  a photolithography method of one embodiment includes following steps: 
     S 10 , providing an incident electron beam  22 ; 
     S 20 , allowing the incident electron beam  22  to pass through a two-dimensional nanomaterial  184  to form a transmission electron beam  26  and a plurality of diffraction electron beams  24 ; 
     S 30 , shielding the transmission electron beam  26 ; and 
     S 40 , allowing the plurality of diffraction electron beams  24  to reach a surface of the object  20  to form a plurality of diffraction spots  27 . 
     In step S 10 , the incident electron beam  22  can be parallel or focused. 
     In step S 20 , the incident electron beam  22  can perpendicularly radiate the two-dimensional nanomaterial  184 . The two-dimensional nanomaterial  184  can be graphene sheet or MoS 2  sheet. The layer number of the two-dimensional nanomaterial  184  can be selected according to need and the transmission and diffraction images as shown in  FIGS. 6-9 . 
     In step S 30 , the transmission electron beam  26  is shielded by the conductor shield  19  electrically connected to the two-dimensional nanomaterial  184 . The transmission electron beam  26  and the diffraction electron beam  24  have a different energy. All the diffraction electron beams  24  have the same energy. In another embodiment, some of the plurality of diffraction electron beams  24  are also shielded. Thus, only the rest of the plurality of diffraction electron beams  24  can reach the surface of the object  20  to form a plurality of diffraction spots  27  in step S 40 . In another embodiment, step S 30  can be omitted. Thus, both the transmission electron beam  26  and the plurality of diffraction electron beams  24  reach the surface of the object  20  to form a transmission spot  29  and a plurality of diffraction spots  27  in step S 40 . 
     In step S 40 , the diffraction electron beams  24  can scan the surface of the object  20  by moving the electron gun or moving the holder  16 . The size of the diffraction spots  27  and the radius R of diffraction ring can be adjusted by changing the distance D between the two-dimensional nanomaterial  184  and the object  20 . 
     Referring to  FIG. 11 , an electronic beam machining system  10 A of another embodiment is an electron beam welding system, an electron beam drilling system, an electron beam melting system, or an electron beam heating system. The electronic beam machining system  10 A comprises a vacuum chamber  11 , an electron emitter  12 , a controlling gate  13 , an accelerating electrode  14 , a focus electrode  15 , a holder  16 , a control computer  17 , and a diffraction unit  18 . 
     The electronic beam machining system  10  can use a plurality of diffraction electron beams  24  to etch the object  20  and has high efficiency. 
     The electronic beam machining system  10 A is similar to the electronic beam machining system  10  above except that the electronic beam machining system  10 A includes a plurality of focus electrodes  15  located between the diffraction unit  18  and the holder  16 . Each of the plurality of focus electrodes  15  is located corresponding to one of the plurality of diffraction electron beams  24 . The plurality of diffraction electron beams  24  would have lower energy than the incident electron beam  22 . The plurality of focus electrodes  15  can further enhance the energy of the plurality of diffraction electron beams  24  to meet the requirement of the electron beam welding system, the electron beam drilling system, the electron beam melting system, or the electron beam heating system. The plurality of focus electrodes  15  is moveable so that the plurality of focus electrodes  15  can be aligned with the plurality of diffraction electron beams  24 . 
     The electronic beam machining system  10 A can use a plurality of diffraction electron beams  24  to treat the object  20  and has high efficiency. In one embodiment, six hexagonally arranged holes are drilled on the object  20  simultaneously. 
     It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Any elements described in accordance with any embodiments is understood that they can be used in addition or substituted in other embodiments. Embodiments can also be used together. Variations may be made to the embodiments without departing from the spirit of the disclosure. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure. 
     Depending on the embodiment, certain of the steps of methods described may be removed, others may be added, and the sequence of steps may be altered. It is also to be understood that the description and the claims drawn to a method may include some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps.