Abstract:
A combined aperture, aperture holder, vacuum feed through and beam blanker for a beam of charged particles fits into an existing aperture in a charged particle beam device such as a scanning electron microscope or an ion beam chamber.

Description:
[0001]     This invention relates to charged particle beam blanker and electron beam blanker for devices such as scanning electron microscopes (SEMs) and Focused Ion Beams (FIB). More particularly, this invention relates to a combined/integrated aperture holder, beam blanker and vacuum feed through device that fits into an existing port in such devices.  
         [0002]     Scanning electron microscopes (SEM) or Focused Ion Beams (FIB) may be used to make small semi-conductor and mechanical devices by techniques such as nanofabrication. In scanning electron microscopes, the scan coils are connected to a computer, and an electron beam is moved in a desired pattern over a beam-sensitive target or sample. When so used, the beam forms an exposed area of desired size and shape in the sample.  
         [0003]     In use, scanning electron microscopes (SEMs) and Focused Ion Beams (FIB) generate and direct a stream or beam of electrons or ions toward a sample. A beam blanker electronically diverts such a beam from the axis of such a device. The blanker includes two opposing electrodes alongside the axis or path of the beam, as shown, for example, in  FIGS. 1 and 1 A.  
         [0004]     Many of these devices (SEM or FIB) may not have access openings or ports adequate for installing beam blanker plates and a vacuum feed through. Forming new openings or new ports in such devices is expensive, time-consuming, and difficult, and may void a manufacturer&#39;s warranty. Using existing vacuum or other ports, and combining the vacuum feed through with a beam blanker and an aperture holder, avoids these problems.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     The combined beam blanker for electron beam and ion beam devices, aperture holder and vacuum feed through, can better be understood by reference to the drawings in which:  
         [0006]      FIG. 1  and  FIG. 1A  show a cross sectional view of a scanning electron microscope column that includes beam blanker plates;  
         [0007]      FIG. 2  shows the electronic elements of a beam blanker connected to a scanning electron microscope;  
         [0008]      FIG. 3  shows a SEM vacuum feed through/aperture holder/aperture device without a beam blanker;  
         [0009]      FIG. 3A  shows a top plan view of the right end of the device shown in  FIG. 3 ;  
         [0010]      FIG. 3B  shows a side elevation view of the right end of the device shown in  FIGS. 3 and 3 A;  
         [0011]      FIGS. 4A, 4B  and  4 C show an embodiment of a beam blanker with vacuum feed through;  
         [0012]      FIG. 4A  shows a side elevation view of the device shown in  FIG. 4 . and  FIG. 4B  shows a top view of the device shown in  FIG. 4 ;  
         [0013]      FIG. 4C  shows a plan view of the right end of the device shown in  FIG. 4 ;  
         [0014]      FIGS. 5A, 5B  and  5 C show an embodiment of a vacuum feed through/aperture holder/aperture device, combined with a beam blanker;  
         [0015]      FIG. 5A  shows a top view of the device shown in  FIG. 5 ;  
         [0016]      FIG. 5B  shows a side elevation view of the device shown in  FIG. 5 ; and  
         [0017]      FIG. 5C  shows a cross-sectional view of the device shown in  FIG. 5 , which shows the placement of the blanker plates and aperture. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]      FIG. 1  shows schematically a charged particle source  10 , e.g., a scanning electron microscope gun that generates a beam  11  on an axis. Beam  11  is directed past condenser aperture  12 , condenser lens  13 , beam blanker plates  14 , objective aperture  15  and scan coils  16 , through objective lens  17 , and onto sample  18 . When activated, beam blanker plates  14  divert the beam from its axis, and away from objective aperture  15 , thus “blanking,” i.e., diverting the beam from the sample or target  18 . A voltage, applied to one or both of beam blanker plates  14 , attracts or repels the beam, depending upon voltage polarity, from the axis of the beam.  
         [0019]     In some embodiments, as  FIG. 2  shows, the blanker for SEM column  22  may include at least six elements: a power supply  19 , connected to blanker driver  20  via cable  21 , and vacuum feed through/blanker plates  23  connected to the blanker driver  20  via cable  24 . The blanker driver  20  receives a signal from the computer via cable  25 . In many embodiments of scanning electron microscopes, the electronics, namely the power supply and driver, are similar. The blanker plates and vacuum feed through, however, may vary, depending upon the structure and operation of the particular SEM. SEM column  22  includes an electron gun, aperture lens, and other elements; all are under vacuum during normal SEM operation. SEM column  22  also includes a final aperture adjustment mechanism. The size of this aperture can be externally modified to receive a combined vacuum feed through, beam blanker, aperture and aperture holder.  
         [0020]     An existing SEM vacuum feed through/aperture holder/aperture device without a beam blanker is shown in  FIGS. 3, 3A  and  3 B. The aperture holder may include aperture rod  30  with vacuum seal  31 , aperture strip  33 , aperture retainer  34  and retaining screws  32 . Aperture strip  33  is secured to aperture rod  30  via aperture retainer  34 . Aperture retainer  34  is secured to aperture rod  30  via retaining screws  32 .  
         [0021]     Aperture strip  33  has one or more holes that allow the beam to pass through. Where there are multiple holes, the beam is allowed to pass through each hole by positioning the aperture strip  33  at the axis of beam  11 , using aperture rod  30 .  
         [0022]     An existing SEM vacuum feed through beam blanker device is shown in  FIGS. 4, 4A  and  4 B. This device may include ground plate  40  with vacuum seal  41 , vacuum feed through  42 , biased plate  43 , insulators  45  and mounting screws  44 . Vacuum feed through  42  may include insulated wire  42 A, retaining screw  42 B, insulating washer  42 C, inner electrode  42 D, vacuum seal  42 F, and insulator tube  42 G. Insulated wire  42 A has the insulation removed at the ends, exposing the inner conductor which is secured to inner electrode  42 D via setscrew  42 E at one end and soldered to connector  42 H at the opposite end. Ground plate  40  has a longitudinally extending passage from opening  46  at one end to opening  49  near the center of the rod. Insulator tube  42 G extends from opening  47  to opening  48  and is inserted into ground plate  40 . Inner electrode  42 D is inserted through vacuum seal  42 F, then inserted into insulator  42 G in ground plate  40 . Insulating washer  42 C is placed over inner electrode  42 D, and has an opening extending through the washer to allow passage of insulating wire  42 A. Retaining screw  42 B has an opening extending longitudinally through the screw to allow passage of insulating wire  42 A. Retaining screw  42 B is placed over insulating washer  42 C, and is secured to ground plate  40 . Insulated wire  42 H is connected to cable  24  shown in  FIG. 2 . Connector  42 H may be electrically connected between cable  24  in  FIG. 2  and insulated wire  42 A to facilitate assembly.  
         [0023]     Properly assembled, vacuum feed through  42  provides electrical connection from connector  42 H to biased plate  43  through insulated wire  42 A and inner electrode  42 D. Inner electrode  42 D is prevented from shorting to ground plate  40  via insulating washer  42 C, vacuum seal  42 F, and insulator tube  42 G. Inner electrode  42 D extends beyond opening  48 , but does not extend as far as opening  49 , and is in contact with biased plate  43 . Thus, electrical connection is achieved to allow the biased plate  43  to deflect the beam  11  when a voltage is applied externally.  
         [0024]     Biased plate  43  is attached to ground plate  40  through insulators  45  via mounting screws  44 . Biased plate  43  is in electrical contact with inner electrode  42 D via the opening  48  through opening  49 .  
         [0025]      FIGS. 5, 5A ,  5 B and  5 C show the aperture holder/aperture device of  FIG. 3 , combined with a vacuum feed through/beam blanker shown in  FIG. 4 . In  FIG. 5A , vacuum feed through  42  is identical in description and function to the vacuum feed through  42  in  FIG. 4A . In  FIG. 5A , aperture strip  33  and aperture retainer  34  are as shown in  FIG. 3B , and serve the same function.  FIG. 5C  shows that the opposing plates may be placed above or below the aperture within the device, as space permits, and are here above the aperture.  
         [0026]     In use, when an electrical signal is applied to connector  42 H, the signal activates plate  43 , diverting the electron beam away from aperture  33  and, thus blanking the beam.  
         [0027]     The integrated beam blanker need not be limited to the aperture assembly described here but may be incorporated in a number of devices that have existing vacuum ports; e.g., vacuum manifolds, detectors, and electrical feed throughs.